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This paper is focused on the preparation of novel hybrid polymer composite materials for 3D filaments. As the reinforcing filler, expanded graphite, carbon fibers, and combinations thereof were used in various ratios up to 10%. The mechanical and thermal properties of virgin and recycled polyethylene phthalate glycol-modified (PETG) composite materials were determined. Almost all prepared composite materials were suitable for 3D printing and they have enhanced mechanical properties compared to the neat PETG matrices. Addition of the fillers to both polymer matrices has an only slight effect on the thermal stability, but the addition of carbon fibers significantly reduced the thermal expansion coefficient. The composites from cheaper recycled PETG have comparable properties to virgin PETG composites, which is of economic and ecological importance. New and cheaper materials can help expand 3D printing to manufacturing plants and the use of 3D printers for special applications.
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applied
sciences
Article
Novel Hybrid PETG Composites for 3D Printing
Mária Kováˇcová1, Jana Kozakoviˇcová1, Michal Procházka 1, Ivica Janigová1, Marek Vysopal 2,
Ivona ˇ
Cerniˇcková3, Jozef Krajˇcoviˇc 3and Zdenko Špitalský1,*
1Polymer Institute, Slovak Academy of Sciences, 845 41 Bratislava, Slovakia
2MYMEDIA, s.r.o., 821 01 Bratislava, Slovakia
3Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava,
917 24 Trnava, Slovakia
*Correspondence: zdeno.spitalsky@savba.sk
Received: 31 March 2020; Accepted: 25 April 2020; Published: 28 April 2020


Abstract:
This paper is focused on the preparation of novel hybrid polymer composite materials for
3D filaments. As the reinforcing filler, expanded graphite, carbon fibers, and combinations thereof
were used in various ratios up to 10%. The mechanical and thermal properties of virgin and recycled
polyethylene phthalate glycol-modified (PETG) composite materials were determined. Almost all
prepared composite materials were suitable for 3D printing and they have enhanced mechanical
properties compared to the neat PETG matrices. Addition of the fillers to both polymer matrices has
an only slight eect on the thermal stability, but the addition of carbon fibers significantly reduced
the thermal expansion coecient. The composites from cheaper recycled PETG have comparable
properties to virgin PETG composites, which is of economic and ecological importance. New and
cheaper materials can help expand 3D printing to manufacturing plants and the use of 3D printers
for special applications.
Keywords: 3D printing; graphite; carbon fibers; composite; PETG; recycled polymer
1. Introduction
The beginnings of 3D printing date back to 1984, when Charles W. Hull applied for patenting
of a method based on hardening of plastics by ultraviolet (UV) radiation [
1
]. The principle of
the technology was the irradiation of UV-sensitive polymer material in the places to be hardened.
Non-irradiated unhardened material was removed, and a final 3D product was obtained. Later on,
a method where polymer powder was sintered by laser to obtain a 3-dimensional object was
developed [
2
]. Currently, there are several 3D printing methods in use, and in recent years there has
been a huge boom in 3D printing development as the original patents gradually expire.
Many specialized companies selling 3D printers also focused on research activities, and they want
to provide a competitive advantage. They try to improve the printing technique and prepare new
materials that could be used for the most demanding professional applications. The improvement of the
printing technology also increases the requirements for the used materials. Initially, 3D printing was to
be used only for prototyping products and generating a low number of products. Current professional
3D printers with enhanced materials for 3D printing are gradually being inserted into manufacturing
plants as well. In the case of a machine failure during the production, products from a 3D printer are
printed out of suitable materials capable of replacing damaged parts of the device for at least a short
while until they have the original accessories [
3
]. The large variability of printers and the ability to print
various shapes are used in medical applications, bionics, and also in the food industry [
4
]. The 3D printer
is able to print artificial teeth [
5
], dental fillings [
6
], endoprostheses [
7
], implants [
8
], and prosthetic
limbs [
9
], and recently printing tissues by proteins and living cells has been considered [
10
]. The most
ambitious visions are about printing complete organs from patient cells [11].
Appl. Sci. 2020,10, 3062; doi:10.3390/app10093062 www.mdpi.com/journal/applsci
Appl. Sci. 2020,10, 3062 2 of 15
The most common non-filled thermoplastic materials used in fused filament fabrication (FFF) are
acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). However, other examples of non-filled
thermoplastic filaments commercially available include acrylonitrile styrene acrylate (ASA), polyamide
(PA), polycarbonate (PC), polyphenylsulfone (PPSF, PPS, or PPSU), polyetherimide (PEI), thermoplastic
polyurethane (TPU), polyethylene terephthalate (PET), thermoplastic elastomer (TPE), high impact
polystyrene (HIPS), polyvinyl alcohol (PVA), polyether ether ketone (PEEK), polyvinylidene fluoride
(PVDF), polyoxymethylene (POM), polyhydroxyalkanoate (PHA) blended with PLA, and some
other blends of the previously mentioned polymers. To improve strength, appearance, conductivity,
and temperature resistance, dierent fillers are added to the polymers. New composite materials are
gradually emerging to expand the possibilities of 3D printing [12].
To eliminate crystallization limits of the PET polymer, a glycol-modified PET copolymer has been
prepared. Poly(-ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) is synthesized by
partially replacing the ethylene glycol (EtGly) units of PET with 1,4-cyclohexanedimethanol (CHDM)
units [
13
]. The PETG copolymer is amorphous when the CHDM content is in the range of 32%–62% [
14
].
Mechanical properties of the PETG copolymer are close to those of PET. PETG copolymer has noticeable
tensile toughness, transparency, flexibility, high processability, and excellent chemical resistance [
15
].
It can be used for many applications and in recent years PETG has also become popular in 3D
printing [16].
In this work the preparation of composite materials of PETG with carbon fillers—expanded
graphite (EG), carbon fibers (CF), and combinations thereof—is described. The main aim was to
produce and characterize a composite material that could be used for the fused filament fabrication
(FFF) 3D printing method and later to replace the virgin polymer matrix with a recycled polymer
matrix without losses of properties but with a decreased price.
2. Materials and Methods
2.1. Materials
Virgin PETG, also called GRIPHEN
®
(Arla Plast AB, Västanåvägen, Sweden) and recycled PETG
(Rondo Plast AB, Ystad, Sweden—datasheet is not available) were used as polymer matrices.
Expanded graphite with the commercial name SIGRATHERM
®
GFG5 (SGL CARBON GmbH,
Meitingen, Germany) and an average size of 5
µ
m and carbon fibers T700S (Toray Industries, Inc.
Tokyo, Japan) were used as fillers.
2.2. Preparation of Composite Filaments
A total of 23 samples were prepared. Nineteen samples were based on virgin PETG (label A in the
name of the sample) and four samples of recycled PETG (label B in the sample name) were prepared.
Two of the prepared samples were free of filler (sample A and B) and served as reference samples.
The other prepared composites contained EG (label G), CFs (label F), and combinations of EG and
CFs (label GF) in dierent weight ratios (numerical designation in the sample name). Before mixing,
composite CFs had to be chopped to a length of 2 mm. A clear summary of the prepared virgin PETG
samples from Arla Plast is shown in Table 1. Samples prepared from recycled PETG are summarized
in Table 2.
Appl. Sci. 2020,10, 3062 3 of 15
Table 1. Overview of prepared virgin PETG composite materials.
wt.% PETG wt.% EG wt.% T700S wt.% Filler
100% 0% 0% 0%
AG-1 99% 1% 0% 1%
AG-2 98% 2% 0% 2%
AG-3 97% 3% 0% 3%
AG-4 96% 4% 0% 4%
AG-5 95% 5% 0% 5%
AG-10 90% 10% 0% 10%
AF-1 99% 0% 1% 1%
AF-2 92% 0% 2% 2%
AF-3 97% 0% 3% 3%
AF-4 96% 0% 4% 4%
AF-5 95% 0% 5% 5%
AF-10 90% 0% 10% 10%
AF-20 80% 0% 20% 20%
AGF-8:2 90% 8% 2% 10%
AGF-6:4 90% 6% 4% 10%
AGF-5:5 90% 5% 5% 10%
AGF-4:6 90% 4% 6% 10%
AGF-2:8 90% 2% 8% 10%
Table 2. Overview of prepared recycled PETG composite materials.
wt.% PETG wt.% EG wt.% T700S wt.% Filler
B100% 0% 0% 0%
BG-5 95% 5% 0% 5%
BF-5 95% 0% 5% 5%
BGF-5:5 90% 5% 5% 10%
Preparation of composite materials was carried out in an Xplore Micro Compounder twin
screwdriver (Xplore Instruments BV, Sittard, The Netherlands) with a mixing chamber (volume of
15 mL) at 240
C. The mixture of polymer matrix with filler was loaded at 50 rpm, subsequently, the rate
was increased to 100 rpm for 15 min and the material was drained at a speed of 30 rpm in the form of
the filament.
To test the properties, the composite was compressed into the shape of a rectangular plate on the
press Fontijne Holland SRA 100ECO 225x320 NA (Fontijne Holland BV, Vlaardingen, The Netherlands).
The form with the sample was placed between two metal plates and then into a press machine heated
to 240
C. In the press machine, the sample was allowed to be tempered at a distance of 30 mm,
after 4 min and the sample was treated with a force of 100 kN for 2 min at 240
C. The press plates were
cooled with water at 50
C and 100 kN. After removing the sample from the press, the test pieces were
punched out on the TKI 4L pneumatic punching press (Tinius Olsen Ltd.—ANAMET, Modra, Slovakia)
at a force of 24 kN. Test body dimensions corresponded to body type 5-II according to ASTM D638-14.
2.3. Mechanical Properties
Dog-bone specimens with working areas of 115
×
19
×
2 mm were cut from the slabs. The mechanical
properties were measured at room temperature using an Instron 3365 (Instron, Buckinghamshire, England)
universal testing machine at a deformation rate of 1 mm
·
s
1
, which increased to 5 mm
·
s
1
after 1%
elongation of the sample. For each sample, 6 measurements were made, calculating the arithmetic mean
and standard deviation for Young’s modulus (E), tensile stress at yield (
σY
), tensile stress at break (
σB
),
and elongation at break (εB).
Appl. Sci. 2020,10, 3062 4 of 15
2.4. Thermogravimetric Analysis
Thermogravimetric analysis was performed in two parallel measurements. The measurement was
performed at a temperature range of 25–590
C on a Mettler Toledo TGA/SDTA 851
e
(Mettler-Toledo,
Bratislava, Slovakia) instrument under a nitrogen atmosphere (30 mL/min) and a heating rate of
10
C/min. Indium and aluminum were used to calibrate the temperature. The mass of the applied
samples was ~2 mg. Two parallel runs were performed for each sample.
2.5. Nanoindentation
Nanoindentation analysis was done with a Hysitron TI 750D Triboindenter (Hysitron, Minneapolis,
MN, USA). A Berkovich geometry diamond tip with tip radius ~100 nm was used. For all indents a
load function with 5-sec loading, 2-sec hold maximal force 5000
µ
N, and 5-sec unloadings was used.
Three lines of indents with mutual spacing 20
µ
m were made. The number of indents was calculated
to analyze the full diameter of the string sample. Fitting the unloading parts of the indentation curves
hardness (H) and reduced Young’s modulus (Er) were calculated.
2.6. Contact Angle Measurements
For wettability analysis, the contact angle measurements were performed on the SEE System
(Advex Instruments, s.r.o., Brno, Czech Republic). Distilled water (3
µ
m) was dripped onto the sample
and the resulting drop was immediately taken with an optical device. Using the SEE System software,
the contact angle was evaluated. The measurement for each sample was repeated 10 times and the
resulting value was reported as the arithmetic mean of the measurements with the standard deviation.
2.7. Density
Density measurement was performed using the pycnometry method. A sample was dispensed
into a pre-weighed pycnometer with a stopper (m
1
), the pycnometer was sealed and weighed (m
2
).
To the pycnometer with the sample was added 96% ethanol of known temperature and known density
(
ρethanol
) and pycnometer filled with sample and ethanol was weighted (m
3
). Finally, the pycnometer
was emptied, rinsed, filled with 96% ethanol and was weighted (m
4
). The sample density (
ρsample
) was
calculated according to Equation (1). The measurement was repeated three times for each sample,
and the resulting density (
ρsample
) was determined as the arithmetic mean of each
ρsample
by Equation (2).
The standard deviations of the measurement were on the level of 10
3
, so they are not mentioned later.
ρsample =(m2m1).ρethanol
m4m3m1+m2(1)
ρsample =Pn
iρsample i
n(2)
2.8. Scanning Electron Microscopy
Samples of the filament were fractured in liquid nitrogen and the cross-section area was
sputtered with gold by the Sample Preparation System from Quorum Technologies Q150R S/E/ES
(Quorum Technologies, Laughton, England). The micrographs were made on a FIB Microscope Quanta
3D 200i (FEI Company, Tokyo, Japan) in a secondary electron mode.
2.9. Dilatometry
Linear thermal expansion coecient was measured using a Netzsch DIL 402C dilatometer (Linseis,
Selb, Germany) in argon environment (gas flow 25 mL
·
min
1
) with a heating rate of 3
C
·
min
1
over
the temperature range from 25 to 80
C. The samples had a size of 12.5 mm in length, approximately
2 mm in width and 8 mm in height. During the measurement, the sample was subjected to a load of
30 cN of the Al2O3push rod.
Appl. Sci. 2020,10, 3062 5 of 15
2.10. 3D Printing
The material was printed using a FFF 3D printer (Quandron 1001, MyMedia, Bratislava, Slovakia)
at 260
C and platform temperature of 60
C with nozzle diameter from 0.4 to 1 mm. The layer height
ranged from 0.15 to 0.3 (the lowest for the small products mentioned). The print speed for small
products was 90%–100% under normal flow.
3. Results
3.1. Characterization of the Properties of Virgin PETG and Recycled PETG
The mechanical properties, thermogravimetric analysis, wettability, and density measurements
for virgin and recycled PETG are summarized in Table 3.
Table 3. Experimental properties of virgin PETG (sample A) and recycled PETG (sample B).
E(MPa) σY(MPa) σB(MPa) εB(%) T10
(C)
T50
(C)
m550
(%)
Contact
Angle ()ρ
(g·cm3)
A1600 ±90 58.3 ±2.1 59.7 ±5.5 362.5 ±10.9 402.1 431.8 9.0 86.9 ±2.6 1.27
B1690 ±40 58.4 ±4.6 55.1 ±1.4 326.2 ±52.8 401.9 426.5 9.2 83.3 ±2.6 1.32
E—Young’s modulus,
σY
—tensile stress at yield,
σB
—tensile stress at break,
εB
—elongation at break,
T
10
—the temperature at which 10% weight loss was recorded, T
50
—the temperature at which 50% weight loss was
recorded, m550—char yield at 550C, ρ—density.
As can be seen from the experimental data in Table 3, virgin PETG and recycled PETG can be
considered as very similar, with respect to the standard deviations. The higher elastic content of
virgin PETG compared to recycled PETG was indicated by the Young’s modulus (E) and elongation
at break (
εB
). The term PETG is referred to in the literature as a transparent PET co-polyester and
1,4-cyclohexylenedimethanol (1,4-CHDM) [
17
]. The properties of PETG are aected by the mole ratio
of 1,4-CHDM and EtGly [
18
,
19
]. PET does not contain 1,4-CHDM and has a density of 1.38 g
·
cm
3
according to the literature, virgin PETG has a measured density of 1.27 g
·
cm
3
, and the recycled PETG
has a measured density of 1.32 g
·
cm
3
. From the measured densities, it can be assumed that virgin
PETG and recycled PETG have dierent contents of 1,4-CHDM and EtGly. The density of 1,4-CHDM is
1.04 g
·
cm
3
and the density of EtGly is 1.11 g
·
cm
3
, suggesting that virgin PETG has a higher content
of 1,4-CHDM and therefore lower density than recycled PETG. With this assumption, the measured
values of contact angles also correspond. PET does not contain 1,4-CHDM and has a contact angle of
72.0
according to the literature [
20
]. The measured contact angles for virgin PETG were 86.9
and for
recycled PETG were 83.3
, indicating that the hydrophobicity decreases with the decreasing content of
1,4-CHDM and the contact angle decreases.
3.2. Properties of Virgin PETG with Expanded Graphite
The mechanical properties from tensile test and nanoindentation of the prepared virgin PETG
composite filled with EG are summarized in Table 4. Table 4shows the varying values of Young’s
modulus of elasticity of the prepared composite materials. With increasing content of EG, the E
increases, so that the material becomes stier. Tensile stress at yield (
σY
) and tensile stress at break (
σB
)
did not change significantly with the addition of EG, but for the highest concentration of filler (sample
AG-10) dropped sharply. In order for the filler to increase the strength of the material, the maximum
adhesion to the matrix-filler interface is needed. In the case of the AG-10 sample, the addition of a
large amount of expanded graphite caused weakening interactions between the polymer chains and
fillers and prevailing of shear forces between expanded graphite particles. This idea is also confirmed
by decreasing εB.
Appl. Sci. 2020,10, 3062 6 of 15
Table 4. Mechanical properties of virgin PETG filled with expanded graphite.
Sample E(MPa) σY(MPa) σB(MPa) εB(%) Er(GPa) H(GPa)
A1600 ±90 58.3 ±2.1 59.7 ±5.5 362.5 ±10.9 2.59 ±0.50 0.13 ±0.03
AG-1 1970 ±120 57.7 ±4.4 57.6 ±4.3 4.4 ±0.4 2.80 ±0.10 0.14 ±0.01
AG-2 2040 ±75 55.1 ±1.9 53.5 ±3.9 4.5 ±0.6 2.88 ±0.36 0.13 ±0.02
AG-3 2150 ±225 54.1 ±3.3 53.1 ±2.3 4.4 ±0.5 3.07 ±0.13 0.14 ±0.01
AG-4 2190 ±40 55.4 ±5.2 53.6 ±6.6 4.4 ±0.8 3.07 ±0.17 0.14 ±0.01
AG-5 2250 ±70 54.6 ±3.9 53.4 ±4.0 4.5 ±0.9 3.29 ±0.17 0.14 ±0.01
AG-10 2630 ±90 32.1 ±2.2 32.2 ±1.8 2.4 ±0.2 3.86 ±0.20 0.14 ±0.01
E—Young’s modulus, σY—tensile stress at yield, σB—tensile stress at break, εB—elongation at break, Er—reduced
Young’s modulus, H—hardness.
The same eect was confirmed from nanoindentation measurements. Reduced Young’s modulus
(E
r
) was increased with increasing concentration of filler, but hardness (H) was not significantly
changed with average value about 140 MPa. It is necessary to notice that the nanoindentation test does
not observe a significant drop of properties for the highest concentration of filler.
The results of thermal properties are summarized in Table 5. It provides information about the
T
10
temperature (the temperature at which the sample quantity dropped to 90% of the original sample
quantity), T
50
(the temperature at which the sample quantity dropped to 50% of the original sample
quantity), m
550
(unburnt weight with respect to original weight at 550
C) from thermogravimetric
analysis, and linear thermal expansion coecient (α) from dilatometry.
Table 5.
Thermal properties of the prepared composite materials–virgin PETG and expanded graphite.
Sample T10 (C) T50 (C) m550 (%) α(106K1)
A402.1 431.8 9.0 60.12
AG-1 401.6 426.2 9.2 60.70
AG-2 402.6 427.5 9.7 62.06
AG-3 402.1 428.5 9.2 64.85
AG-4 403.3 430.5 10.0 52.07
AG-5 402.9 431.7 10.9 51.23
AG-10 404.3 432.5 12.4 55.14
From the measured temperatures T
10
and T
50
it can be seen there was only a small eect of filler
on the final thermal stability of polymer composites compared to pure virgin PETG. The value of T
10
was almost unchanged; the value T
50
was more dependent on the concentration of filler; however,
there was no uniform trend. First, it decreased with an increasing amount of filler about 4
C then it
was increased up to the values of neat PETG. In the case of char yield at 550
C, the trend was clear
with assumptions and it increased with an increased amount of EG. It was obvious that EG was not
subject to thermal degradation. Nevertheless, the value for the thermal expansion coecient slightly
decreased from the value for virgin PETG, ~60
×
10
6
K
1
up to ~51
×
10
6
K
1
. The high thermal
conductivity of the EG could result in better heat transfer in the polymer matrix, and it also depends
on homogeneous dispersion of filler inside the matrix. A carbon layer was probably formed on the
surface of the filament, which served as an insulating carbon barrier. Therefore, several opposite eects
led to ambiguous trends.
The wettability analysis (Table 6) showed that the addition of EG to PETG resulted in reduced
contact angle values. It was expected due to the contact angle value of pure expanded graphite,
which was significantly lower,
49.4
[
21
]. A similar situation was also found in the literature, where the
contact angle decreased with increasing content of EG [
22
]. The opposite eect was found in the case
of density. The density of the prepared composite materials increased with increasing content of EG
(Table 6). This trend was clear because the density of the pure expanded graphite was higher than the
PETG density. The value of pure filler was 1.5 g·cm3.
Appl. Sci. 2020,10, 3062 7 of 15
Table 6.
The densities and contact angles of the prepared virgin PETG composite materials with the EG.
Sample Density (g·cm3)Contact Angle ()
A1.27 86.9 ±2.6
AG-1 1.30 78.8 ±3.8
AG-2 1.30 76.9 ±3.6
AG-3 1.31 75.1 ±2.4
AG-4 1.31 73.3 ±4.1
AG-5 1.32 71.3 ±3.5
AG-10 1.32 70.9 ±5.2
Figure 1represents the cross-section of the prepared filament. As can be seen on the AG-5 sample
from a scanning electron microscope at a 708
×
magnification under the electron beam, the EG was
evenly dispersed and no visible agglomerates of the filler were present.
Appl. Sci. 2020, 9, x FOR PEER REVIEW 7 of 15
(Table 6). This trend was clear because the density of the pure expanded graphite was higher than
the PETG density. The value of pure filler was 1.5 g·cm3.
Table 6. The densities and contact angles of the prepared virgin PETG composite materials with the
EG.
Density (g·cm3)
Contact Angle (°)
1.27
86.9 ± 2.6
1.30
78.8 ± 3.8
1.30
76.9 ± 3.6
1.31
75.1 ± 2.4
1.31
73.3 ± 4.1
1.32
71.3 ± 3.5
1.32
70.9 ± 5.2
Figure 1 represents the cross-section of the prepared filament. As can be seen on the AG-5 sample
from a scanning electron microscope at a 708× magnification under the electron beam, the EG was
evenly dispersed and no visible agglomerates of the filler were present.
Figure 1. SEM micrograph of cross-section filamentvirgin PETG composite containing 5 wt.% of the
expanded graphite.
3.3. Properties of Virgin PETG Filled with Carbon Fibers
The tensile mechanical properties of the prepared composite material of the PETG filled with
CFs are summarized in Table 7. Samples were prepared from 2 mm long CFs in the concentration
range 120 wt. %. The mechanical properties were enhanced more significant in case of CFs than EG
filling. The AF-10 sample reached about 30% higher value of Youngs modulus as the AG-10 sample.
The AF-20 sample had a 124% higher E than the pure polymer matrix. As the increase in CF content
also increased the tensile stress, the material became more resistant to permanent (plastic)
Figure 1.
SEM micrograph of cross-section filament–virgin PETG composite containing 5 wt.% of the
expanded graphite.
3.3. Properties of Virgin PETG Filled with Carbon Fibers
The tensile mechanical properties of the prepared composite material of the PETG filled with
CFs are summarized in Table 7. Samples were prepared from 2 mm long CFs in the concentration
range 1–20 wt.%. The mechanical properties were enhanced more significant in case of CFs than EG
filling. The AF-10 sample reached about 30% higher value of Young’s modulus as the AG-10 sample.
The AF-20 sample had a 124% higher Ethan the pure polymer matrix. As the increase in CF content
also increased the tensile stress, the material became more resistant to permanent (plastic) deformation,
while the addition of EG caused the
σY
and
σB
slight decrease. The decrease in the
εB
of the prepared
CF composites is comparable with the eect of EG, although absolute values of
εB
of CF composites are
double the values for EG composites. The same eect was observed for nanoindentation measurements.
Appl. Sci. 2020,10, 3062 8 of 15
The E
r
was increased with increasing loading with CF up to 150% comparing to pure polymer matrix
but H remained constant at the same value as for EG composites—about 140 MPa. Here it is necessary
to note that nanoindentation reinforcement (E
r
) was not as significant as in the case of EG composites.
Table 7. Mechanical properties of virgin PETG filled with carbon fibers.
Sample E(MPa) σY(MPa) σB(MPa) εB(%) Er(GPa) H(GPa)
A1600 ±90 58.3 ±2.1 59.7 ±5.5 362.5 ±10.9 2.59 ±0.50 0.13 ±0.03
AF-1 1850 ±100 60.1 ±1.8 66.4 ±1.8 6.2 ±2.7 2.72 ±0.12 0.14 ±0.0
AF-2 1990 ±135 61.2 ±4.3 64.9 ±5.6 5.7 ±1.2 2.69 ±0.22 0.14 ±0.02
AF-3 2110 ±110 65.6 ±3.0 65.0 ±3.2 5.0 ±0.1 2.60 ±0.18 0.15 ±0.01
AF-4 2370 ±285 66.3 ±2.2 66.4 ±2.1 4.8 ±0.3 2.60 ±0.37 0.13 ±0.02
AF-5 2860 ±190 75.3 ±4.5 72.1 ±1.0 5.1 ±0.5 2.72 ±0.31 0.13 ±0.02
AF-10 3430 ±120 75.4 ±3.4 73.5 ±6.6 5.7 ±1.3 2.75 ±0.53 0.13 ±0.03
AF-20 3580 ±275 75.8 ±1.7 74.4 ±2.1 3.9 ±1.3 3.09 ±0.67 0.13 ±0.04
The results of the thermogravimetric analysis are summarized in Table 8, where the temperature
information T
10
,T
50
, and m
550
are demonstrated. Similar results to EG composite materials were
observed and it can be concluded that thermogravimetric properties are independent of the carbon
filler. However, a significant dierence was observed for dilatometry. As can be seen from Table 8,
α
for CF composites sharply decreased with increasing loading of filler. It is a very positive property in
case of 3D printing when thermal shrinkage is one of the limiting factors for high-volume printing.
Table 8. Thermal properties of the prepared composite materials–virgin PETG and CFs.
Sample T10 (C) T50 (C) m550 (%) α(106K1)
A402.1 431.8 9.0 60.12
AF-1 397.2 425.9 7.1 55.12
AF-2 399.6 427.4 7.8 51.46
AF-3 399.3 427.3 9.5 48.16
AF-4 399.7 427.5 9.2 45.35
AF-5 400.3 428.4 11.3 39.74
AF-10 401.0 429.6 14.8 34.35
AF-20 401.1 432.7 23.7 28.79
The relationship of the contact angle to the CF content is shown in Table 9. The contact angle
dropped, and the eect was the same in case EG composites. Opposite trends, as for the EG filaments,
were observed for the density of CF filaments when density was decreasing with increasing loading up
to 88% of density pure polymer matrix (sample AF-20). It was caused by the low density of pure CFs
since the manufacturer reported the value of 1.80 g·cm3.
Table 9.
The densities and contact angles of the prepared virgin PETG composite materials with the CFs.
Sample Density (g·cm3)Contact Angle ()
A1.27 86.9 ±2.6
AF-1 1.27 77.5 ±4.9
AF-2 1.24 76.5 ±3.5
AF-3 1.16 77.9 ±4.4
AF-4 1.12 75.4 ±3.3
AF-5 1.13 74.7 ±4.3
AF-10 1.13 70.3 ±3.0
AF-20 1.12 64.8 ±3.6
In Figure 2A, which was obtained with a scanning electron microscope at a 75
×
magnification,
the cross-section of the filament is visible. Homogeneous distribution of CFs in the whole fracture
Appl. Sci. 2020,10, 3062 9 of 15
area of filament was observed and no CF clusters occurred. Figure 2B captures the fracture area at
1228
×
magnification under the electron beam. CFs that were coated with a polymer matrix were
captured thereon. Dierent holes were present. It was probably caused by low interfacial forces
between the fibers and polymer matrix.
Appl. Sci. 2020, 9, x FOR PEER REVIEW 9 of 15
Table 9. The densities and contact angles of the prepared virgin PETG composite materials with the
CFs.
Sample
Density (g·cm3)
Contact Angle (°)
A
1.27
86.9 ± 2.6
AF-1
1.27
77.5 ± 4.9
AF-2
1.24
76.5 ± 3.5
AF-3
1.16
77.9 ± 4.4
AF-4
1.12
75.4 ± 3.3
AF-5
1.13
74.7 ± 4.3
AF-10
1.13
70.3 ± 3.0
AF-20
1.12
64.8 ± 3.6
In Figure 2A, which was obtained with a scanning electron microscope at a 75× magnification,
the cross-section of the filament is visible. Homogeneous distribution of CFs in the whole fracture
area of filament was observed and no CF clusters occurred. Figure 2B captures the fracture area at
1228× magnification under the electron beam. CFs that were coated with a polymer matrix were
captured thereon. Different holes were present. It was probably caused by low interfacial forces
between the fibers and polymer matrix.
Figure 2. SEM micrograph of the fracture surface of the prepared AF-5 composite material. (A) shows
the cross-section of the entire string at 75 magnification, and (B) shows a fracture area at 1228×
magnification.
3.4. Properties of Virgin PETG Filled with EG and CFs
Because both the above-mentioned carbon fillers have their own advantages for 3D filaments,
we tried to combine them to prepared hybrid composites. CFs are better for reinforcing and
eliminating thermal expansion, while EG decreases surface roughness of filament and supports the
rheology during 3D printing. For better comparison, the concentration of filler was kept constant at
10 wt.% and the ratio of EG to CFs was varied between 8:2, 6:4, 5:5, 4:6, and 2:8, respectively.
The results of the mechanical properties of the hybrid virgin PETG composites are summarized
in Table 10. In the case of EG composite materials, increasing the concentration of the filler increased
Youngs modulus. An even more pronounced increase in Youngs modulus was recorded in CF
composites. It is understandable that in the case of hybrid composite materials containing a
combination of EG and CFs, Youngs modulus will grow with an increasing of CFs content. From the
AG-1 to AG-10 samples, the σY decreased with an increasing concentration of EG, and in the AF-1 to
AF-20 samples there was an increase in the σY with an increasing concentration of CFs. In the case of
a combination of fillers, the σY and σB can be assumed as constant, but higher than for the pure
Figure 2.
SEM micrograph of the fracture surface of the prepared AF-5 composite material. (
A
) shows the
cross-section of the entire string at 75 magnification, and (
B
) shows a fracture area at 1228
×
magnification.
3.4. Properties of Virgin PETG Filled with EG and CFs
Because both the above-mentioned carbon fillers have their own advantages for 3D filaments,
we tried to combine them to prepared hybrid composites. CFs are better for reinforcing and eliminating
thermal expansion, while EG decreases surface roughness of filament and supports the rheology during
3D printing. For better comparison, the concentration of filler was kept constant at 10 wt.% and the
ratio of EG to CFs was varied between 8:2, 6:4, 5:5, 4:6, and 2:8, respectively.
The results of the mechanical properties of the hybrid virgin PETG composites are summarized in
Table 10. In the case of EG composite materials, increasing the concentration of the filler increased
Young’s modulus. An even more pronounced increase in Young’s modulus was recorded in CF
composites. It is understandable that in the case of hybrid composite materials containing a combination
of EG and CFs, Young’s modulus will grow with an increasing of CFs content. From the AG-1 to AG-10
samples, the
σY
decreased with an increasing concentration of EG, and in the AF-1 to AF-20 samples
there was an increase in the
σY
with an increasing concentration of CFs. In the case of a combination
of fillers, the
σY
and
σB
can be assumed as constant, but higher than for the pure polymeric matrix.
Since the addition of EG and CFs caused a significant drop in
εB
, it also occurred when both fillers
were used simultaneously. E
r
decreased with an increasing ratio of CFs; however for all cases it was
above the value for pure polymer matrix. The hardness from nanoindentation measurements seemed
to be constant.
Table 10. Mechanical properties of virgin PETG filled with EG and CFs.
Sample E(MPa) σY(MPa) σB(MPa) εB(%) Er(GPa) H(GPa)
A1600 ±90 58.3 ±2.1 59.7 ±5.5 362.5 ±10.9 2.59 ±0.50 0.13 ±0.03
AGF-8:2 2646 ±170 63.4 ±2.7 58.6 ±2.3 4.6 ±0.8 4.02 ±0.24 0.16 ±0.02
AGF-6:4 3364 ±190 66.9 ±5.9 65.7 ±5.8 4.2 ±0.8 3.76 ±0.28 0.15 ±0.01
AGF-5:5 3054 ±235 66.2 ±1.1 62.4 ±5.8 4.9 ±1.6 3.26 ±0.38 0.14 ±0.02
AGF-4:6 3095 ±370 66.4 ±4.1 63.9 ±3.9 5.1 ±1.2 3.49 ±0.21 0.14 ±0.01
AGF-2:8 3330 ±480 69.1 ±7.4 66.3 ±1.3 4.5 ±1.6 3.35 ±0.25 0.14 ±0.01
Appl. Sci. 2020,10, 3062 10 of 15
The results of the thermogravimetric analysis are summarized in Table 11. The same trends were
present for filaments with individual fillers. Only a slight eect on the temperature of degradation and
a significant decrease for the coecient of thermal expansion were observed, which were caused by
the presence of CFs.
Table 11. Thermal properties of the prepared composite materials–virgin PETG with EG and CF.
Sample T10 (C) T50 (C) m550 (%) α(106K1)
A402.1 431.8 9.0 60.12
AGF-8:2 400.9 430.1 12.0 48.86
AGF-6:4 401.5 431.7 15.6 48.68
AGF-5:5 402.1 431.8 14.8 34.83
AGF-4:6 403.6 431.9 16.8 36.61
AGF-2:8 401.7 431.7 14.9 40.37
In composite materials with EG, an increase in the concentration of the filler resulted in a reduction
in contact angle values. A similar trend was also found in CF composite materials when the contact
angle was reduced with increasing CF concentration. As can be seen from Table 12, the combination of
these two fillers decreased the contact angle with an increasing concentration of CF. The contact angle
of the prepared composites was higher than the contact angle of samples AG-10 and AF-10.
Table 12.
The densities of prepared PETG composites with EG and CFs at the total loading of 10 wt.%.
Sample Density (g·cm3)Contact Angle ()
A1.27 86.9 ±2.6
AGF-8:2 1.29 89.9 ±3.6
AGF-6:4 1.21 85.5 ±6.7
AGF-5:5 1.20 81.3 ±6.8
AGF-4:6 1.20 80.2 ±5.4
AGF-2:8 1.17 79.3 ±5.5
The densities recorded in Table 12 had a relatively expected progression as EG PETG composites
grew densities with increasing EG content and CF composites density dropped with an increasing CF
content. A similar trend was also evident for hybrid composites when the density decreased with the
decreasing content of EG and the increasing CF content. It should be concluded that all samples except
for sample AGF-8:2 have a lower density than the density of pure virgin PETG and therefore these
filaments can be useful in lightweight applications.
Figure 3shows that the dispersion of the fillers seems to be uniform; there are no visible aggregates
of the fillers or separation of fillers.
3.5. Characterization of the Properties of Recycled PETG Filled with EG, CFs, and Their Combination
Because the price of filament is one of the crucial requirements for mass production of 3D printing
we tried to replaces commercial virgin PETG with cheaper recycled PETG whose price is ten times
lower. The usage of recycled PETG is also an important part of the circular economy that is on the rise
for industrial scales. Also, it significantly helps to protect the planet.
The results of the mechanical properties of pure recycled PETG (sample B) and three prepared
composite materials from recycled PETG are summarized in Table 13. As can be seen from the table,
the values of the Eand
σY
for all prepared materials based on recycled PETG with consideration of the
standard deviation, are comparable with the equivalent composites based on virgin PETG, and only
the sample BF-5 had a slightly lower σY.
Appl. Sci. 2020,10, 3062 11 of 15
Appl. Sci. 2020, 9, x FOR PEER REVIEW 11 of 15
Figure 3 shows that the dispersion of the fillers seems to be uniform; there are no visible
aggregates of the fillers or separation of fillers.
Figure 3. SEM micrograph of the cross-section is of the hybrid PETG filament containing 5 wt.% of
the EG and 5 wt.% of CF. The image was obtained by a scanning electron microscope at a 175×
magnification under an electron beam.
3.5. Characterization of the Properties of Recycled PETG Filled with EG, CFs, and Their Combination
Because the price of filament is one of the crucial requirements for mass production of 3D
printing we tried to replaces commercial virgin PETG with cheaper recycled PETG whose price is ten
times lower. The usage of recycled PETG is also an important part of the circular economy that is on
the rise for industrial scales. Also, it significantly helps to protect the planet.
The results of the mechanical properties of pure recycled PETG (sample B) and three prepared
composite materials from recycled PETG are summarized in Table 13. As can be seen from the table,
the values of the E and σY for all prepared materials based on recycled PETG with consideration of
the standard deviation, are comparable with the equivalent composites based on virgin PETG, and
only the sample BF-5 had a slightly lower σY.
The σB and εB of the prepared recycled PETG composites were comparable with the values for
virgin PETG composites. Again, the sample BF-5 had a σB slightly lower than the AF-5 sample.
Deterioration of mechanical properties was observed from nanoindentation measurements when all
parameters decreased except Er for BF-5 sample. Nevertheless, all mechanical properties were eligible
for reinforced PETG filament with regard to the significant reduction of the final price.
Figure 3.
SEM micrograph of the cross-section is of the hybrid PETG filament containing 5 wt.%
of the EG and 5 wt.% of CF. The image was obtained by a scanning electron microscope at a 175
×
magnification under an electron beam.
Table 13. Mechanical properties of recycled PETG composites.
Sample E(MPa) σY(MPa) σB(MPa) εB(%) Er(GPa) H(GPa)
B1690 ±45 58.4 ±4.6 55.1 ±1.4 326.2 ±52.8 2.41 ±0.13 0.11 ±0.01
BG-5 2115 ±120 53.6 ±1.8 52.8 ±1.4 4.8 ±0.7 2.87 ±0.25 0.11 ±0.01
BF-5 2500 ±265 67.4 ±3.0 66.8 ±2.7 4.9 ±0.6 3.14 ±0.38 0.11 ±0.01
BGF-5:5 3110 ±190 64.5 ±4.3 63.2 ±3.3 4.3 ±0.4 2.47 ±0.3 0.11 ±0.02
The
σB
and
εB
of the prepared recycled PETG composites were comparable with the values
for virgin PETG composites. Again, the sample BF-5 had a
σB
slightly lower than the AF-5 sample.
Deterioration of mechanical properties was observed from nanoindentation measurements when all
parameters decreased except E
r
for BF-5 sample. Nevertheless, all mechanical properties were eligible
for reinforced PETG filament with regard to the significant reduction of the final price.
The thermal properties are summarized in Table 14. Recycled PETG reached T
50
about 5
C lower
than T
50
of virgin PETG. The dierences between the virgin PETG and recycled PETG composites were
not significant after the addition of the filler. This could be caused by the good thermal conductivity of
both carbon fillers. The same eect was also observed in case of linear thermal expansion coecient
α
, when carbon fillers decreased their values, but the absolute value of recycled PETG composites
was slightly higher than the value for virgin PETG composites due to the higher initial value of pure
recycled PETG.
Appl. Sci. 2020,10, 3062 12 of 15
Table 14.
Results of thermogravimetric analysis of the prepared composite materials based on
recycled PETG.
Sample T10 (C) T50 (C) m550 (%) α(106K1)
B401.9 426.5 9.2 73.71
BG-5 402.1 429.5 10.1 61.24
BF-5 398.4 426.7 9.6 48.41
BGF-5:5 404.9 432.2 17.4 46.04
The contact angles and densities of the recycled PETG composite materials are recorded in
Table 15. Similar to virgin PETG composites, recycled PETG composite with EG had a higher density
than the pure polymer sample, and the CF composite had a lower density than the pure polymer
matrix. However, the decrease of BF-5 sample density was not as significant as for the AF-5 sample.
A completely dierent situation was observed in the case of the contact angle. In the case of virgin PETG
composites, the contact angles decreased after filling with EG or CF, and in the case of recycled PETG
these values increased. The growth was not significant; it was only in the range of experimental error.
Table 15. Contact angles and densities of prepared composite materials base on recycled PETG.
Sample Contact Angle ()Density (g·cm3)
B83.3 ±2.6 1.32
BG-5 87.8 ±5.1 1.33
BF-5 87.5 ±5.6 1.29
BGF-5:5 86.8 ±3.6 1.25
3.6. Testing of Prepared Samples by 3D Printing
Prepared composite materials were tested with a commercial 3D printer, which uses FFF technology.
Materials for testing were prepared as a filament (Figure 4A) and 3D printed spare parts are presented
in Figure 4B.
All prepared composite filaments were suitable for 3D printing using the FFF method.
The produced filaments had excellent processing properties for 3D printing, except for the AG-10
filaments, which were very brittle and broke during printing. This break was due to overall worse
mechanical properties and poor dispersion of filler compared to other EG/PETG composites.
It is necessary to mention the positive eect of partially replacing non-environment friendly CFs
for EG—a form of naturally occurring graphite. EG significantly eliminates surface roughness and
therefore eliminates a nozzle abrasion, which is a very common problem during 3D printing filaments
with CF composites. The most positive eect is reducing the final price of filament when commercial
virgin PETG was replaced for cheaper recycled PETG. The final result is a cheaper filament with
enhanced mechanical properties which is more suitable from the point of view of ecology.
The new hybrid material is very suitable for 3D printing, ranging from small parts (Figure 4B)
to larger parts (e.g., large printer pad in Figure 4C) to massive equipment with a total length of over
6 m. The prints are extremely strong, the layers adhere firmly, and the overall strength of the products
is extraordinary. The individual layers adhere perfectly. It enables large product printing as well as
several-day continuous 3D printing compared to competing materials. The resulting products look
more beautiful, which improves subsequent work with products and saves time. As can be seen
in Figure 4C, where the products printed under the same conditions are compared, the dierences
between commercial CF PETG filament (Figure 4C—left) and our hybrid filament from recycled PETG
(Figure 4C—right) are clear. Last but not least, the final products are also lighter by about 25%.
Appl. Sci. 2020,10, 3062 13 of 15
Appl. Sci. 2020, 9, x FOR PEER REVIEW 13 of 15
Figure 4. (A) Prepared PETG composite filament, (B) 3D printed component, (C) 3D printed large
printer pad, leftfrom commercial CF/PETG filament, righthybrid filament from recycled PETG.
It is necessary to mention the positive effect of partially replacing non-environment friendly CFs
for EGa form of naturally occurring graphite. EG significantly eliminates surface roughness and
therefore eliminates a nozzle abrasion, which is a very common problem during 3D printing
filaments with CF composites. The most positive effect is reducing the final price of filament when
commercial virgin PETG was replaced for cheaper recycled PETG. The final result is a cheaper
filament with enhanced mechanical properties which is more suitable from the point of view of
ecology.
The new hybrid material is very suitable for 3D printing, ranging from small parts (Figure 4B)
to larger parts (e.g., large printer pad in Figure 4C) to massive equipment with a total length of over
6 m. The prints are extremely strong, the layers adhere firmly, and the overall strength of the products
is extraordinary. The individual layers adhere perfectly. It enables large product printing as well as
several-day continuous 3D printing compared to competing materials. The resulting products look
more beautiful, which improves subsequent work with products and saves time. As can be seen in
Figure 4C, where the products printed under the same conditions are compared, the differences
between commercial CF PETG filament (Figure 4Cleft) and our hybrid filament from recycled
PETG (Figure 4Cright) are clear. Last but not least, the final products are also lighter by about 25%.
4. Conclusions
The paper was devoted to the preparation of polymer composite materials for 3D printing
technology by fused filament fabrication. Prepared composite materials were based on virgin PETG
and recycled PETG. EG, CFs and their combinations were used as the filler.
From the measured results it is evident that all the composite materials produced have higher
values of the E than the pure polymer matrix. Adding EG resulted in enhancement of mechanical
Figure 4.
(
A
) Prepared PETG composite filament, (
B
) 3D printed component, (
C
) 3D printed large
printer pad, left—from commercial CF/PETG filament, right—hybrid filament from recycled PETG.
4. Conclusions
The paper was devoted to the preparation of polymer composite materials for 3D printing
technology by fused filament fabrication. Prepared composite materials were based on virgin PETG
and recycled PETG. EG, CFs and their combinations were used as the filler.
From the measured results it is evident that all the composite materials produced have higher
values of the Ethan the pure polymer matrix. Adding EG resulted in enhancement of mechanical
properties and increasing density. Composite materials containing CFs and CF/EG also enhanced
mechanical properties but decreased density. Addition of the carbon fillers has minimal influence on
the thermal properties of the material; however, the presence of CF in composites has a significantly
lower thermal expansion coecient. Replacing virgin PETG with recycled PETG does not significantly
change the properties of the filament, just causes a price reduction.
Both PETG and recycled PETG composite materials, except for one sample, have excellent
processing properties on a 3D printer with FFF technology. New hybrid filaments bring benefits
from an economic point of view (cheaper recycled PETG, lower nozzle wear) as well as from an
environmental point of view (recycled materials, partial replacing CF by graphite).
5. Patents
Špit
á
lsk
ý
, Z.; Kov
á
ˇcov
á
, M.; ˇ
Duriš, V.; Vysopal, M.; Svoboda P. Polym
é
rne kompozity pre 3D tlaˇc
(Polymer composites for 3D printing), utility model 8207 Slovakia, 25 July 2018.
Appl. Sci. 2020,10, 3062 14 of 15
Author Contributions:
Methodology, M.V.; investigation, J.K. (Jana Kozakoviˇcov
á
), M.P., I.J., I. ˇ
C., and J.K.
(Jozef Krajˇcoviˇc); writing—original draft preparation, M.K.; writing—review and editing, M.K.; visualization,
M.K.; supervision, Z.Š.; project administration, Z.Š. All authors have read and agreed to the published version of
the manuscript.
Funding: The authors are grateful for the financial support of Grant VEGA 2/0051/20.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Hull, C.W. Apparatus for Production of Three-Dimensional Objects by Stereolithography. U.S. Patent
No. 4575330, 8 August 1984.
2.
Deckard, C.R.; Beaman, J.J.; Darrah, J.F. Method for Selective Laser Sintering with Layerwise Cross-Scanning.
USA Patent No. 5155324, 17 October 1986.
3.
Sun, L.; Hua, G.; Cheng, T.C.E.; Wang, Y. How to price 3D-printed products? Pricing strategy for 3D printing
platforms. Int. J. Prod. Econ. 2020. [CrossRef]
4. Tran, J.L. 3D-Printed Food. Minnesota J. Law Sci. Technol. 2016,17, 855.
5.
Kanazawa, M.; Inokoshi, M.; Minakuchi, S.; Ohbayashi, N. Trial of a CAD/CAM system for fabricating
complete dentures. Dent. Mater. J. 2011,30, 93–96. [CrossRef] [PubMed]
6. Van Noort, R. The future of dental devices is digital. Dent. Mater. 2012,28, 3–12. [CrossRef] [PubMed]
7.
Bazlov, V.A.; Mamuladze, T.Z.; Pavlov, V.V.; Kirilova, I.A.; Sadovoy, M.A. Modern materials in fabrication of
scaolds for bone defect replacement. AIP Conf. Proc. 2016,1760, 020004.
8.
Mangano, C.; Bianchi, A.; Mangano, F.G.; Dana, J.; Colombo, M.; Solop, I.; Admakin, O. Custom-made 3D
printed subperiosteal titanium implants for the prosthetic restoration of the atrophic posterior mandible of
elderly patients: A case series. 3D Print. Med. 2020,6, 1–14. [CrossRef] [PubMed]
9.
Gondokaryono, R.; Gonz
á
lez, L.; Garrido, K.; Sujumnong, N.; Wee, A.; Goal, A.O. A Graphic User Interface
(GUI) to build a cost-eective customizable 3D printed Prosthetic Hand. bioRxiv 2020. [CrossRef]
10.
Mironov, V.; Boland, T.; Trusk, T.; Forgacs, G.; Markwald, R.R. Organ printing: Computer-aided jet-based 3D
tissue engineering. Trends Biotechnol. 2003,21, 157–161. [CrossRef]
11.
Lee Ventola, C. Medical applications for 3D printing: Current and projected uses. Pharm. Ther.
2014
,39,
704–711.
12.
Gonzalez-Gutierrez, J.; Cano, S.; Schuschnigg, S.; Kukla, C.; Sapkota, J.; Holzer, C. Additive manufacturing
of metallic and ceramic components by the material extrusion of highly-filled polymers: A review and future
perspectives. Materials 2018,11, 840. [CrossRef] [PubMed]
13.
Paszkiewicz, S.; Szymczyk, A.; Pawlikowska, D.; Irska, I.; Taraghi, I.; Pilawka, R.; Gu, J.; Li, X.; Tu, Y.;
Piesowicz, E. Synthesis and characterization of poly(ethylene terephthalate-: Co -1,4-cyclohexanedimethylene
terephtlatate)- block -poly(tetramethylene oxide) copolymers. RSC Adv. 2017,7, 41745–41754. [CrossRef]
14.
Rao, Y.Q.; Greener, J.; Avila-Orta, C.A.; Hsiao, B.S.; Blanton, T.N. The relationship between microstructure
and toughness of biaxially oriented semicrystalline polyester films. Polymer
2008
,49, 2507–2514. [CrossRef]
15.
Wang, X.; Liu, W.; Zhou, H.; Liu, B.; Li, H.; Du, Z.; Zhang, C. Study on the eect of dispersion phase
morphology on porous structure of poly (lactic acid)/poly (ethylene terephthalate glycol-modified) blending
foams. Polymer 2013,54, 5839–5851. [CrossRef]
16.
Chen, T.; Zhang, J.; You, H. Photodegradation behavior and mechanism of poly(ethylene
glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymers: Correlation with copolymer
composition. RSC Adv. 2016,6, 102778–102790. [CrossRef]
17.
Liu, Y. Synthesis and Characterization of Amorphous Cycloaliphatic Copolyesters with Novel Structures
and Architectures. Ph.D. Thesis, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA,
22 March 2012.
18.
Li, B.; Zhang, X.; Zhang, Q.; Chen, F.; Fu, Q. Synergistic enhancement in tensile strength and ductility of ABS
by using recycled PETG plastic. J. Appl. Polym. Sci. 2009,113, 1207–1215. [CrossRef]
19.
Scheirs, J.; Long, T.E. (Eds.) Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters;
Wiley Series in Polymer Science; John Wiley & Sons Ltd.: Chichester, UK, 2004; ISBN 0471498564.
20.
Junkar, I.; Vesel, A.; Cvelbar, U.; Mozetiˇc, M.; Strnad, S. Influence of oxygen and nitrogen plasma treatment
on polyethylene terephthalate (PET) polymers. Vacuum 2009,84, 83–85. [CrossRef]
Appl. Sci. 2020,10, 3062 15 of 15
21.
Kepi´c, D.P.; Risti´c, I.S.; Marinovi´c-Cincovi´c, M.T.; Peruško, D.B.; Špit
á
lsky, Z.; Pavlovi´c, V.B.;
Budimir, M.D.; Šialoviˇc, P.; Drami´canin, M.D.; Miˇcuš
í
k, M.; et al. Simple route for the preparation
of graphene/poly(styrene-b-butadiene-b-styrene) nanocomposite films with enhanced electrical conductivity
and hydrophobicity. Polym. Int. 2018,67, 1118–1127. [CrossRef]
22.
Staniszewski, Z.; Fray, M. El Influence of thermally exfoliated graphite on physicochemical, thermal and
mechanical properties of copolyester nanocomposites. Polimery 2016,61, 482–489. [CrossRef]
©
2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
... Kováčová et al. [51] reinforced recycled and virgin PETG with Expanded Graphite (EG) and Carbon Fibers (CF). Composite filament containing EG, CF or a combination of both was extruded. ...
... Tensile strength Wastepaper [ 42 , 44 ]; Cardboard [ 42 , 44 ]; Wood flour [ 42 , 44 ] Hemp (p) [41] ; BAK + Al 2 O 3 + SiC [33] Gypsum (f) [39] ; Autogenic biochar [37] MCC [32] ; Hemp (f) [ 39 , 41 , 43 ]; Harakeke (f) [ 39 , 41 , 43 ]; Hemp (p) [43] ; Harakeke (p) [43] ; CNF [12] ; SiC + Al 2 O 3 [ 28 , 31 ]; BAK + Al 2 O 3 + SiC [33] ; WC [47] ; Coated mineral filler [40] Tensile yield strength EG [51] CF [51] ; CF + EG [51] ; mCF [48] Tensile break strength SiC + Al 2 O 3 [28] ; BAK + Al 2 O 3 + SiC [33] SiC + Al 2 O 3 [28] ; BAK + Al 2 O 3 + SiC [33] Tensile modulus Hemp (p) [41] ; Harakeke (p) [41] MCC [32] ; Hemp (f) [ 39 , 41 , 43 ]; Harakeke (f) [ 39 , 41 , 43 ]; Gypsum (f) [39] ; Hemp (p) [43] ; Harakeke (p) [43] ; CF [51] ; EG [51] ; CF + EG [51] ; Wastepaper [ 42 , 44 ]; Cardboard [ 42 , 44 ]; Wood flour [ 42 , 44 ]; Autogenic biochar [37] ; SiC + Al 2 O 3 [31] ; WC [47] ; mCF [48] Tensile elongation at break CF [51] ; EG [51] ; CF + EG [51] ; WC [47] SiC Cotton [36] Wastepaper [ 42 , 44 ]; Cardboard [ 42 , 44 ]; Wood flour [ 42 , 44 ]; Autogenic biochar [37] ; CNF [12] tan δ Autogenic biochar [37] Cotton [36] Crystallinity ...
... Tensile strength Wastepaper [ 42 , 44 ]; Cardboard [ 42 , 44 ]; Wood flour [ 42 , 44 ] Hemp (p) [41] ; BAK + Al 2 O 3 + SiC [33] Gypsum (f) [39] ; Autogenic biochar [37] MCC [32] ; Hemp (f) [ 39 , 41 , 43 ]; Harakeke (f) [ 39 , 41 , 43 ]; Hemp (p) [43] ; Harakeke (p) [43] ; CNF [12] ; SiC + Al 2 O 3 [ 28 , 31 ]; BAK + Al 2 O 3 + SiC [33] ; WC [47] ; Coated mineral filler [40] Tensile yield strength EG [51] CF [51] ; CF + EG [51] ; mCF [48] Tensile break strength SiC + Al 2 O 3 [28] ; BAK + Al 2 O 3 + SiC [33] SiC + Al 2 O 3 [28] ; BAK + Al 2 O 3 + SiC [33] Tensile modulus Hemp (p) [41] ; Harakeke (p) [41] MCC [32] ; Hemp (f) [ 39 , 41 , 43 ]; Harakeke (f) [ 39 , 41 , 43 ]; Gypsum (f) [39] ; Hemp (p) [43] ; Harakeke (p) [43] ; CF [51] ; EG [51] ; CF + EG [51] ; Wastepaper [ 42 , 44 ]; Cardboard [ 42 , 44 ]; Wood flour [ 42 , 44 ]; Autogenic biochar [37] ; SiC + Al 2 O 3 [31] ; WC [47] ; mCF [48] Tensile elongation at break CF [51] ; EG [51] ; CF + EG [51] ; WC [47] SiC Cotton [36] Wastepaper [ 42 , 44 ]; Cardboard [ 42 , 44 ]; Wood flour [ 42 , 44 ]; Autogenic biochar [37] ; CNF [12] tan δ Autogenic biochar [37] Cotton [36] Crystallinity ...
Article
In a world going through a plastic waste management catastrophe with serious environmental, health, social and economic consequences, the ideal step forward would be the creation of circular flows of material which allow for the materials to remain in the value-chain for as long as possible and completing multiple lifecycles. In the case of thermoplastics, a new recycling route is emerging, made possible by Material Extrusion additive manufacturing (MEX): distributed recycling. However, similar to what happens with mainstream recycling of these materials, the thermo-mechanical processes involved, as well as other factors such as exposure to UV-light, result in waste streams with degraded properties. This way, the possible range of applications and functionality of the polymers is reduced along with number of viable lifecycles. On this scope, the application of methods to control and modify the properties of the polymers, enhancing them or compensating for the degradation in a distributed recycling context, becomes important. Not only is this an emerging, less explored recycling route with great potential to complement the existing ones, but it also presents its own set of challenges and advantages to be explored. In this work, a systematic search methodology is followed to conduct a literature review on which the current practices on the modification and control of properties of parts produced from recycled or reprocessed thermoplastics through MEX are assessed. Research gaps and opportunities are presented from the discussion of the results.
... Its applications include surgical tools [138], 3D bioprinting [121], and electromagnetic induction shielding [139]. chemical resistance [141]. One of its drawbacks is high porosity in the printed product [142], but this can also be an advantage in specific applications such as bone models [143], custom-made laboratory hardware [144] and orthopaedics [145]. ...
... PLA 160-230[110,112] 20-60 [110,158] 60-65 [164] Biodegradable [110], non-toxic, low cost [112] Tough, strong [112] Tissue engineering [113], biosensors [114] acoustics [165] ABS 215-250 [110] 80-110 [110,158] 104-109 [166] Heat resistant, strong, durable [110] Needs high temperature and hot bed, toxic [110] Microdevices [115], biomedicine [116] PVA 160-230 [110,112] 20-45 [110] 45-69 [167,168] Water-soluble, useful as a support [110] Affected by humidity [110] Bracket, dental models [119] TPE 180-230 [110] 20-55 [110] ≈ -35 [169] Flexible [110] Low temperature stability [170] Textile [123], orthopaedic insoles [124] PC 200-280 [125,126] 80-100 [129,158] 140-150 [125,126 ] Resistant to shocks and high temperatures [127,12 8] Needs high temperature and hot bed [125,126] Dental [130], orthopaedic [171],tissue engineering [131] PLA/GRAPHENE 210-230 [138] ≈60 [138] ≈70 [138] Conductive, resistant [137] Needs hot bed, difficult to print Surgical tools [138], bioelectronics [172], electromagnetic induction shielding [139] PETG 220-250 [140] ≈60 [140] ≈74 [173] Notable tensile toughness, transparency, flexibility, high processability, and excellent chemical resistance [141] The final product has high porosity [142] Bone models [143], laboratory hardware [144] and orthopaedics [145] PEEK 340-440 [147] 110-150 [174,175] ≈143 [147] Excellent mechanical properties, good lubricity, and chemical resistance. ...
Article
Fused deposition modelling (FDM) is an advanced 3D printing technique for the manufacture of plastic materials. The ease of use, prototyping accuracy and low cost makes it a widely used additive manufacturing technique. FDM creates 3D structures through the layer-by-layer melt-extrusion of a plastic filament. The production of a printed structure involves the generation of a digital design of the model by 3D design software and its execution by the printer until the complete model is reproduced. This review presents the current status of FDM, how to handle and operate FDM printers, industry standards of printing, the types of filaments that can be used, the post-processing treatments, advantages, and limitations as well as an overview of the increasing application fields of FDM technology. The application areas of FDM are endless, including biomedicine, construction, automotive, aerospace, acoustics, textiles, and occupational therapy amongst others. Even during the current Coronavirus disease (COVID-19) pandemic, FDM has helped to fabricate face masks, ventilators and respiratory systems, respiratory valves, and nasopharyngeal swabs for COVID-19 diagnosis. FDM 3D and 4D printing can produce polymeric and composite structures of various designs, and compositions in a range of materials according to the desired application. The review concludes by discussing the future prospects for FDM.
... However, since the temperatures for 3D printing range from 150 °C to 300 °C, a limited thermal decomposition of the thermosensitive material elements may occur in the case of inaccurate printing profile [12,13]. Polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), nylon, pure polyethylene terephthalate (PET) or its copolymer with glycol (PETG) are among the most significant thermoplastic polymers that can be used in the production of organic/inorganic composites [12][13][14]. A tremendous ecological advantage is the possibility of obtaining plastic components by recycling the used plastics [14]. ...
... Polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), nylon, pure polyethylene terephthalate (PET) or its copolymer with glycol (PETG) are among the most significant thermoplastic polymers that can be used in the production of organic/inorganic composites [12][13][14]. A tremendous ecological advantage is the possibility of obtaining plastic components by recycling the used plastics [14]. For medical purposes, it is convenient to use materials with antimicrobial properties. ...
Article
Purpose This study aims to describe the preparation of antimicrobial material usable in 3D printing of medical devices. Despite the wealth of technological progress at the time of the crisis caused by SARS-CoV-2 virus: Virus that causes current Pandemic situation (COVID-19), the global population had long been exposed beforehand to an acute absence of essential medical devices. As a response, a new type of composite materials intended for rapid prototyping, based on layered silicate saponite (Sap), antimicrobial dye phloxine B (PhB) and thermoplastics, has been recently developed. Design/methodology/approach Sap was modified with a cationic surfactant and subsequently functionalized with PhB. The hybrid material in powder form was then grounded with polyethylene terephthalate-glycol (PETG) or polylactic acid (PLA) in a precisely defined weight ratio and extruded into printing filaments. The stability and level of cytotoxicity of these materials in various physiological environments simulating the human body have been studied. The applicability of these materials in bacteria and a yeast-infected environment was evaluated. Findings Ideal content of the hybrid material, with respect to thermoplastic, was 15 weight %. Optimal printing temperature and speed, with respect to maintaining antimicrobial activity of the prepared materials, were T = 215°C at 50 mm/s for PETG/SapPhB and T = 230°C at 40 mm/s for PLA/SapPhB. 3 D-printed air filters made of these materials could keep inner air flow at 63.5% and 76.8% of the original value for the PLA/SapPhB and PETG/SapPhB, respectively, whereas the same components made without PhB had a 100% reduction of airflow. Practical implications The designed materials can be used for rapid prototyping of medical devices. Originality/value The new materials have been immediately used in the construction of an emergency lung ventilator, Q-vent, which has been used in different countries during the COVID-19 crisis.
... Moreover, the values obtained for the 3-dir and the neat material at a temperature of 30 • C are in accordance with those found in the literature. These values correspond to the CTE value of the neat material for ABS [70,71], PC [70,71], and PETG [70,72,73] as found in the literature. At temperatures near T g , negative CTE values are captured. ...
Article
Full-text available
Large format polymer extrusion-based additive manufacturing has been studied recently due to its capacity for high throughput, customizable bead size and geometry, and ability to manu-facture large parts. Samples from three fiber-filled amorphous thermoplastic materials 3D printed using a Masterprint 3X machine from Ingersoll Machine Tools were studied, along with their neat counterparts. Characterization techniques included thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermo-mechanical analysis (TMA). TGA results showed that the fillers decreased the degradation temperature for most of the materials investigated, with a 30 ◦C decrease for polycarbonate (PC) and a 12 ◦C decrease for polyethylene terephthalate glycol (PETG). For all the materials used, heat capacity increases with increasing temperature. Moreover, results show that a highly conductive filler increases the heat capacity. In contrast, a material with a lower conductivity decreases the heat capacity indicated in the 15.2% and 2.54% increase for acrylonitrile butadiene styrene (ABS) and PC and a 27.68% decrease for PETG. The TMA data show that the printed bead exhibits directional properties consistent with an orthotropic material. Smaller strains and coefficient of thermal expansion (CTE) were measured along the bead direction and across the bead compared to the through bead thickness showing that fillers are predominantly oriented in the bead direction, which is consistent with the literature. CTE values through bead thickness and neat material are similar in magnitude, which corresponds to the CTE of the matrix material. The experimental results serve to characterize the effect of fiber filler on the part thermal strains in three principal directions and two-part locations during the extrusion and bead deposition of large-format polymer extrusion-based additive manufacturing technologies.
... Subsequently, the nozzle position is incremented and a new layer of material can be deposited on top of previously deposited layers. Some of the most commonly used materials with MEX 3D printing include acrylonitrile butadiene styrene (ABS) [22], polylactic acid (PLA) [23,24], polyethylene terephthalate glycol-modified (PETG) [25,26] and nylons [27,28]. Among these, PLA and PETG distinguish themselves as being easy to process and relatively inexpensive, while also requiring inexpensive 3D-printing equipment. ...
Article
Full-text available
In outdoor environments, the action of the Sun through its ultraviolet radiation has a degrading effect on most materials, with polymers being among those affected. In the past few years, 3D printing has seen an increased usage in fabricating parts for functional applications, including parts destined for outdoor use. This paper analyzes the effect of accelerated aging through prolonged exposure to UV-B on the mechanical properties of parts 3D printed from the commonly used polymers polylactic acid (PLA) and polyethylene terephthalate–glycol (PETG). Samples 3D printed from these materials went through a dry 24 h UV-B exposure aging treatment and were then tested against a control group for changes in mechanical properties. Both the tensile and compressive strengths were determined, as well as changes in material creep characteristics. After irradiation, PLA and PETG parts saw significant decreases in both tensile strength (PLA: −5.3%; PETG: −36%) and compression strength (PLA: −6.3%; PETG: −38.3%). Part stiffness did not change significantly following the UV-B exposure and creep behavior was closely connected to the decrease in mechanical properties. A scanning electron microscopy (SEM) fractographic analysis was carried out to better understand the failure mechanism and material structural changes in tensile loaded, accelerated aged parts.
... When printing a face shield, we decided for PETG because its properties -copolymer has noticeable tensile toughness, flexibility, high processability, and excellent chemical resistance [12]. Then, we needed to treat the surface and warm up for better connections between layers. ...
... The main disadvantage of industrial prototypes after their end life usage is a huge negative impact on the environment due to the plastic waste accumulation in terrestrial and aquatic ecosystems. There were several attempts to eliminate it by using recyclable polymers or using biodegradable polymers [13,14]. Especially in the case of medical application, the 3D printed materials should be biodegradable and biocompatible [15]. ...
Article
Fused deposition modelling (FDM) is a process of additive manufacturing allowing creating of highly precise complex three-dimensional objects for a large range of applications. The principle of FDM is an extrusion of the molten filament and gradual deposition of layers and their solidification. Potential applications in pharmaceutical and medical fields require the development of biodegradable and biocompatible thermoplastics for the processing of filaments. In this work, the potential of production of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) filaments for FDM was investigated in respect to its thermal stability. Copolymer P(3HB-co-4HB) was biosynthesised by Cupriavidus malaysiensis. Rheological and mechanical properties of the copolymer were modified by the addition of plasticizers or blending with poly(lactic acid). Thermal stability of mixtures was studied employing thermogravimetric analysis and rheological analyses by monitoring the time-dependent changes in the complex viscosity of melt samples. The plasticization of P(3HB-co-4HB) slightly hindered its thermal degradation but the best stabilization effect was found in case of the copolymer blended with poly(lactic acid). Overall, rheological, thermal and mechanical properties demonstrated that the plasticized P(3HB-co-4HB) is a potential candidate of biodegradable polymer for FDM processes.
... A study comparing commercially available virgin and recycled versions of the same polymer filaments would be superfluous since the mechanical properties are virtually identical. 6,7 Printing parameters and test results are discussed to develop a better understanding of the theoretical and practical aspects of the specimens' physical characteristics. The specimens' linear elastic tensile moduli are compared to make recommendations for the safe application in engineering design. ...
Article
Full-text available
Herein, the effects of recycled polymers on the mechanical properties of additively manufactured specimens, specifically those derived by fused deposition modelling, are determined. The intention is to investigate how 3D-printing can be more sustainable and how recycled polymers compare against conventional ones. Initially, sustainability is discussed in general and more sustainable materials such as recycled filaments and biodegradable filaments are introduced. Subsequently, a comparison of the recycled filament recycled Polyethylene terephthalate (rePET) and a conventional Polyethylene terephthalate with glycol (PETG) filament is drawn upon their mechanical performance under tension, and the geometry and slicing strategy for the 3D-printed specimens is discussed. Finally, the outcomes from the experiments are compared against numerically determined results and conclusions are drawn.
Article
This work reports the thermal, rheological, and crystallographic structural behavior of recycled polyethylene terephthalate (rPET) derived from bottle waste. The intent is to optimize it to an upcoming source for additive manufacturing by modulating its behavior using a chain extender triphenyl phosphite (TPP), nanofiller montmorillonite (MMT K‐10), and catalyst antimony trioxide (Sb2O3). FT‐IR (Fourier Transform Infrared) analysis showed an increase in absorbance due to the Sb2O3. The thermal analysis of the rPET using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) ascertains a 10°C decrease in Tg with a substantial increase in the degradation onset of 7°C due to MMT content. The melt flow index (MFI) study showed an increase with a similar range in intrinsic viscosity and weight average molecular weight (Mw) due to the additives. The percentage crystallinity, interlayer distance, and average crystallite size are determined and analyzed by X‐ray diffraction (XRD) and DSC curves. The results are within the comparative range of both tests. The presence of Sb2O3 with higher MMT content showed agglomeration, and increased TPP showed low crystalline properties. These results provide that rPET can be altered to manufacture feedstock to suit different 3D printing techniques for prototyping. Recycled PET (rPET) flakes were treated with MMT and TPP using reactive extrusion technique to optimize their processability. It was found MMT maximum 3% by weight can be processed to prevent agglomeration. The combinations of TPP, MMT, and Sb2O3 can be altered according to the characteristic properties shown by the rPET that is obtained from the recycled lot.
Article
The focus on the combined effects of fibers and nanoparticles in the realization of novel, high‐performance polymer composites has been increasing progressively. In addition to this, the intervention of additive manufacturing in this pursuit has further enhanced this interest among researchers to experimentally quantify the properties of these composites for various applications. Therefore, this study focuses on experimentally evaluating the thermal behavior of extruded glycol‐modified poly(ethylene terephthalate) (PETG) comonomers reinforced with short carbon fibers (SCFs) and organically modified montmorillonite (OMMT) nanoclay that are apt for 3D printing. Different weight compositions of the aforementioned materials are prepared, compounded, and extruded using a twin‐screw extruder into 16 variants of 3D printable filaments. These filaments are subjected to thermogravimetric analysis, differential scanning calorimetry, and Fourier transform‐infrared (FTIR) spectroscopy as per their respective American society for testing and materials (ASTM) standards. The results show improvements in the thermal behavior of the composites for various concentrations of OMMT and SCFs. The FTIR analyses complement the capability of OMMT particles and SCFs for microvibrational damping and infrared absorption. The study also demonstrates the influence of chemical interactions between the SCFs, OMMT, and PETG on the overall performance of the composites. It is believed that this study paves way for the induction of such composites in relevant applications including secondary aerospace structures, automobile interiors, and other engineering structural needs.
Preprint
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This project aims to create a tool that allows medical staff to use an intuitive graphical user interface (GUI) based application to generate STL models of a customizable prosthetic hand, that can be 3d printed to fit a specific patient's hand size. Since the whole process of adjust and adapt the prosthetics devices could consume most of the resources of small medical attention centers. And the necessity to adapt the prosthetic devices is highly relevant when these are intended to be used by the pediatric population. This software creates a customizable parametric 3d model for a trans-radial prosthetic hand and all its necessary components for 3d print and assemble it. The software is intended to be operated by non-trained staff, reducing the costs of remodeling or adapting the original model to fit the necessity of a patient, allowing to produce personalized prosthetic devices in a cost-effective manner with an effortless customization approach. This will allow that medical practitioners with a lack of technical background to get involved in spreading 3D-prosthetics. Also, using open-source parametric 3D-models could lead to existing 3D-prosthetic projects that will adopt this method of customization, allowing the expansion of 3D-printed prosthetics at developing-countries reaching all needing patients. Ultimately, this tool will allow the medical staff to focus on adjusting or replacing the prosthetic devices more often than previously, due to be considered too expensive.
Article
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Purpose: To present the application of custom-made 3D-printed subperiosteal implants for fixed prosthetic restoration of the atrophic posterior mandible of elderly patients. Methods: Between January 2017 and June 2018, all partially edentulous patients aged over 65 years, with two or more missing teeth in the posterior atrophic mandible, and who did not want to undergo bone regenerative procedures, were included in this study. These patients were rehabilitated with custom-made subperiosteal implants, designed from cone beam computed tomography (CBCT) and fabricated in titanium by means of direct metal laser sintering (DMLS). The outcome measures were fit and stability of the implants at placement, duration of the intervention, implant survival, and early and late complications. All patients were followed for 1 year after surgery. Results: Ten patients (four males, six females; mean age 69.6, SD ± 2.8, median 69, 95% CI 67.9-71.6) were included in the study. The fit of the implants was satisfactory, with a mean rating of 7 out of 10 (SD ± 1.6, median 7, 95% CI 6-8). Only two implants had insufficient fit, because of the presence of scattering in the CBCT; however, they were adapted to the sites during the interventions. The mean duration of the intervention was 44.3 min (SD ± 19.4, median 37, 95% CI 32.3-56.3). At the one-year follow-up, no implants were lost (survival rate 100%). One implant presented immediate postoperative complications with pain, discomfort and swelling, and two patients experienced late complications, having their provisional restorations fractured during the temporisation phase. All these complications were minor in nature, but the final complication rate amounted to 30% (three of ten patients). Conclusions: Although this study has limits (small patient sample and short follow-up), DMLS has proven to be an effective method for fabricating accurate subperiosteal implants, with high survival rates. This may represent an alternative treatment procedure in elderly patients with a severely atrophic posterior mandible, since it allows avoidance of regenerative bone therapies. Further studies are needed to confirm these outcomes.
Article
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Additive manufacturing (AM) is the fabrication of real three-dimensional objects from metals, ceramics, or plastics by adding material, usually as layers. There are several variants of AM; among them material extrusion (ME) is one of the most versatile and widely used. In MEAM, molten or viscous materials are pushed through an orifice and are selectively deposited as strands to form stacked layers and subsequently a three-dimensional object. The commonly used materials for MEAM are thermoplastic polymers and particulate composites; however, recently innovative formulations of highly-filled polymers (HP) with metals or ceramics have also been made available. MEAM with HP is an indirect process, which uses sacrificial polymeric binders to shape metallic and ceramic components. After removing the binder, the powder particles are fused together in a conventional sintering step. In this review the different types of MEAM techniques and relevant industrial approaches for the fabrication of metallic and ceramic components are described. The composition of certain HP binder systems and powders are presented; the methods of compounding and filament making HP are explained; the stages of shaping, debinding, and sintering are discussed; and finally a comparison of the parts produced via MEAM-HP with those produced via other manufacturing techniques is presented.
Article
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A series of poly(ethylene terephthalate-co-1,4-cyclohexanedimethanol terephthalate)-block-poly(tetramethylene oxide) (PETG-block-PTMO) copolymers were synthesized by means of a polycondensation process and characterized using ¹H nuclear magnetic resonance (H NMR) and Fourier transform infrared spectroscopy (FTIR), that confirm the successful synthesis of the material. Differential scanning calorimetry (DSC), small – and wide-angle X-ray diffraction (SAXS and WAXS), and thermogravimetric analysis (TGA) were used in order to evaluate the influence of the block copolymers' composition and microstructure on the phase transition temperatures, thermal properties, as well as the thermooxidative and thermal stability of the PETG-block-PTMO copolymers, respectively. The mechanical properties were investigated by tensile testing and dynamic mechanical measurements (DMTA). We found that along with an increase in PTMO weight fraction, both number-average molecular weights and intrinsic visocisities increase. Moreover, an increase in the flexible segments content in PETG-block-PTMO resulted in shifting the values of glass transition temperatures toward lower ones, which was confirmed by DSC and DMTA analyses, thus affirming the miscibility of both phases. At the same time, along with an increase of PTMO flexible segments amount in the PETG-block-PTMO copolymers, the values of Young's modulus, tensile strength at yield and weight losses in lower temperatures range, i.e. 280–390 °C, decrease.
Article
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New materials which were composites filled with thermally exfoliated graphite (tEG) were prepared. In these composites segmented multi-block thermoplastic elastomer containing 60 wt % of hard segments as in poly(ethylene terephthalate) (PET) and 40 wt % of soft segments comprising amorphous sequences of ethylene ester of dilinoleic acid (DLA) was used as a polymer matrix. The filler, i.e.TEG, which is graphene-like material, was introduced into the polymer matrix in various content (0.1, 0.2, 0.3 and 0.5 wt %) during in situ polycondensation. Scanning electron microscope images of the nanocomposites showed very good nanofiller dispersion in the polymer matrix with few agglomerates. The addition of nanofiller affected the degree of polymer crystallinity as well as the mechanical properties of PET-DLA nanocomposites. Importantly, thermally exfoliated graphite reduced the water contact angle of nanocomposites thus making their surface more hydrophilic and potentially more attractive in medical applications.
Article
3D printing, which is synonymous with the additive manufacturing is gaining popularity, which leads to emergence of 3D printing platforms. The pricing strategies for such platforms are quite complicated, since different kinds of products/services could be provided on the same platform at the same time. We explore the optimal pricing strategy for a 3D printing platform that sells standard and customized products, taking products' differentiation into account, where the platform and designer seek to maximize their profits, while the customer wishes to maximize their utility gained from the product purchase. In the basic model, we derive the platform's optimal prices when the platform allows the designer to add a mark-up for the standard product. We find that the standard product's final price increases with its own quality and decreases with the customized product's quality. When labour cost is low, the customized product's final price increases with its own quality and decreases with the standard product's quality. We also find that the designer's optimal mark-up for the standard product increases with the printing cost of the standard product and quality of the customized product, and decreases with the interaction cost, printing cost of the customized product, and quality of the standard product. We compare the platform's profit in the case of “partial pricing power”, in which the platform allows the designer to add a mark-up, with that in the case of “full pricing power”, in which the platform sets the final price of the standard product and charges a commission fee as its revenue. We find that if the difference in the quality between the standard and customized products is high, then the strategy of charging a commission fee at a rate of more than 25% is more profitable than the strategy of allowing the designer to add a mark-up to the reservation price.
Article
This paper reports a simple route for the preparation of graphene/poly(styrene‐b‐butadiene‐b‐styrene) (SBS) nanocomposite films employing vacuum filtration method. Graphene is well exfoliated by electrochemical procedure and homogeneously dispersed in the polymer matrix. Prepared nanocomposite films were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X‐photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy and scanning electron microscopy. Morphological studies showed that graphene formed a smooth coating over the surface of SBS. The increase in graphene concentration induces the wrinkling of graphene sheets at the composite surface which causes further surface roughness increase. The FTIR, Raman and XPS spectra of graphene/SBS nanocomposite films indicate the strong interactions between graphene and polymer matrix. According to XRD patterns, introducing of SBS in graphene did not modify graphene structure additionally, i.e. crystal lattice parameters do not depend on SBS content in graphene/SBS nanocomposite films. The graphene/SBS nanocomposite films also exhibited better hydrophobicity due to the increased surface roughness and lower sheet resistivity (reduced 10 times) compared to exfoliated graphene.
Article
The effect of copolymer composition on the photodegradation behavior and the mechanism of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymers with different 1,4-cyclohexanedimethanol (CHDM) content were first investigated. The changes in surface chemical groups of the PETG copolymers after UV irradiation were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform-infrared (ATR-FTIR) spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to probe the thermal properties of the PETG copolymers before and after UV irradiation. The crosslinking degree of the PETG copolymers after UV irradiation was evaluated by gel content measurement. The photooxidation rate of the PETG copolymers increased with increasing CHDM content. Namely, the inherent photostability of the PETG copolymers decreased with increasing CHDM content. The PETG copolymers with different compositions exhibited the similar photooxidation mechanism. The presence of CHDM in the PETG molecular chains accelerated the formation of photoproducts. The photoproducts of the PETG copolymers were consisted of aliphatic alcohol, anhydride, benzoic acid, double bond and aliphatic acid as end-groups and molecular terephthalic acid. Moreover, the crosslinking products formed during UV irradiation were not further oxidized in the whole irradiation period (0-800 h). The glass transition temperatures (Tgs) of the PETG copolymers after UV irradiation increased due to the irradiation crosslinking. The increment of Tg increased gradually with increasing CHDM content. Therefore, the higher the CHDM content was, the higher the crosslinking degree obtained.
Conference Paper
The article defines the requirements for modern scaffold-forming materials and describes the main advantages and disadvantages of various synthetic materials. Osseointegration of synthetic scaffolds approved for use in medical practice is evaluated. Nylon 618 (certification ISO9001 1093-1-2009) is described as the most promising synthetic material used in medical practice. The authors briefly highlight the issues of individual bone grafting with the use of 3D printing technology. An example of contouring pelvis defect after removal of a giant tumor with the use of 3D models is provided.