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© 2021 Thais Ferreira da Silva, Gabriel Portilho Monteiro de Souza, Guilherme Ferreira de Melo Morgado, Yves
Nicolau Wearn, Ana Paula Fonseca Albers, Eduardo Quinteiro and Fabio Roberto Passador. This open access article is
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American Journal of Engineering and Applied Sciences
A Brief Review of the Latest Advances of Attapulgite as a
Reinforcing Agent in Polymer Matrix Nanocomposites
1*Thais Ferreira da Silva, 1Gabriel Portilho Monteiro de Souza, 1Guilherme Ferreira de Melo Morgado,
1Yves Nicolau Wearn, 2Ana Paula Fonseca Albers, 2Eduardo Quinteiro and 1Fabio Roberto Passador
1Federal University of São Paulo (UNIFESP) (Polymer and Biopolymer Technology Laboratory (TecPBio),
330 Talim St., São José dos Campos, SP, Brazil, 12231-280), Brazil
²Federal University of São Paulo (UNIFESP) (Ceramic Technology Laboratory, 330 Talim St.,
São José dos Campos, SP, Brazil, 12231-280), Brazil
Article history
Received: 25-04-2021
Revised: 26-05-2021
Accepted: 28-05-2021
Corresponding Author:
Thais Ferreira da Silva
Federal University of São
Paulo (UNIFESP) (Polymer
and Biopolymer Technology
Laboratory (TecPBio), 330
Talim St., São José dos
Campos, SP, Brazil, 12231-
280), Brazil
Abstract: The development of polymeric nanocomposites using clay
minerals as a Nano filler is of great interest to researchers and industry.
Many clay minerals are used to modify the properties of the polymers;
this strategy improves the thermal and mechanical performance and
changes the surface finishing and the processing characteristics. The
Attapulgite (ATP), which is a clay mineral of the hydrated magnesium
silicates family, has gained prominence in recent years because it
combines low cost and high performance. It has a large surface area,
strong absorption capacity superior to any other natural mineral, good
mechanical resistance and thermal stability. These properties make ATP
an ideal candidate for reinforcing polymeric materials. Different
approaches and emerging technologies have been applied to improve the
thermal and mechanical properties of polymer/ATP nanocomposites
which can extend the different chemical treatments used in ATP.
Therefore, this review article presents the latest advances related to the
use of ATP in the development of polymeric nanocomposites, showing
future perspectives for new trends in ATP applications. In general, ATP
modifies the mechanical properties of polymers, either in the natural or
modified state. and is a good alternative for the replacement of lamellar
clays such as montmorillonites with the advantage of having a lower cost
and a wide world market to be explored, that which drive new trends in
applications for ATP, such as flame retardant of cotton fabrics, dye
adsorption, hydrogel membranes for wound dressing, sustainable
packaging and fuel cell applications.
Keywords: Attapulgite, Nanocomposite, Clay Mineral, Polymers, Thermal
and Mechanical Properties
The addition of clay mineral fillers in polymeric
materials is a great industrial strategy and has become
frequent in the polymer industry. This strategy
improves the thermal, mechanical and thermo-
mechanical properties, changing the surface
appearance and processing characteristics and mainly
reducing the final cost of the products (Liu et al., 2020;
Gill et al., 2020; Abbasian et al., 2020; Adak et al.,
2018; Rapacz-Kmita et al., 2015).
The development of nanocomposites with good
cost-benefit resulted in the study of the feasibility and
convenience of using a large number of mineral fillers
(Rapacz-Kmita et al., 2015). Polymeric nanocomposites
are a composite materials class where a dispersed phase
has at least one of its dimensions less than 100 nanometers
(nm). Thus, the dispersed phase has a large surface area,
which allows a greater transfer of tension between the
polymer matrix and the dispersed phase. This great
transfer of tension results in a high reinforcement notably
for the improvement in the mechanical properties,
Thais Ferreira da Silva et al. / American Journal of Engineering and Applied Sciences 2021, 14 (2): 292.307
DOI: 10.3844/ajeassp.2021.292.307
processability, permeability and thermal stability of the
nanocomposite. Another great advantage in the use of
nanofillers is the small amount of clay mineral that is used
in the composition, contributing for the production of
parts with low density and high performance (Bogue,
2011; Hussain et al., 2006; Rane et al., 2018;
Thostenson et al., 2005).
Three main methods can be used to obtain
nanocomposites with the addition of clay minerals.
In Situ Polymerization (ISP): This method involves
the addition of the clay filler in the mixture of monomers
and polymerization reagents. The nanofillers are swollen
by the liquid monomers, followed by the polymerization
process. The particles are then surrounded by the polymeric
chain that is forming, ensuring the dispersion of the
inorganic content. The process is initiated by radiation or
heat, in addition to the diffusion of a suitable initiator for the
monomer in question. However, very strict control of the
polymerization process is required to achieve a good
exfoliation of nanofiller (Rane et al., 2018; Alexandre and
Dubois, 2000; Liu et al., 2017; Powell and Beall, 2007;
Wang et al., 2014; Xie et al., 2014; Zhang et al., 2016).
Solution Intercalation (SI): In this method, the clay
and the polymer are added to an organic solvent. The
solvent is chosen so that the fillers can be easily swollen
by it and the polymer dissolves in it as well. The polymer
solution will adsorb the clay and disperse it. After that, the
solvent is evaporated and the clay particles are well
dispersed in the nanocomposite structure (Rane et al., 2018;
Alexandre and Dubois, 2000; Giannelis, 1996; Lee et al.,
2018; Xiang et al., 2017; Yin et al., 2010a; 2010b).
Melt Intercalation (MI): This method consists of
increasing the system temperature to melt the polymer
and disperse the clay in it. The high shear levels that
the polymer chains will exert on the nanofillers cause
the clay mineral particles to break and disperse. This
way of dispersion of the filler in the polymer is ideal
for the properties to be applied in an anisotropic
manner, that is, without a specific direction for the
stress application. During this process, the melted
polymer chains tend to diffuse in between nanofillers
to produce the nanocomposite system. This process can
be considered eco-friendly, as it does not involve the
use of high amounts of solvents. Also, it is the cheapest
process because it manages to produce nanocomposites
on a large scale (Rane et al., 2018; Zhang et al., 2016;
Fornes et al., 2001; Liu et al., 1999; Qi et al., 2013;
Zhao et al., 2012).
Polymeric nanocomposites using clay usually have
very attractive mechanical and thermal properties and are
superior to conventional composites, as well as reduced
permeability values, better chemical resistance to solvents
and greater flame retardancy. Polymeric composites
reinforced with clays are of great interest due to their
applications in the packaging and automotive
industries. There are studies on clay reinforced with
rubber and silt as well. It is becoming quite common to
mix clay and rubber particles processed in different
civil and geotechnical constructions such as light
landfill, road substrate, fill with embankment,
embankments, asphalt construction, sound barrier,
railway construction and reinforcement of foundation.
However, the use of these mixtures in full-scale projects
requires a better understanding of the mechanical
performance of the mixtures (Rouhanifar et al., 2020;
Majedi et al., 2020; 2021; Yazdani et al., 2018;
Rouhanifar and Afrazi, 2019).
Several clay minerals have been widely studied to
improve the mechanical properties of polymeric matrices,
such as montmorillonite (Rodrigues Passos Severino et al.,
2019; Passer et al., 2013a; 2013b; Barbalho, 2012; Bai et al.,
2018), halloysite (Bertolino et al., 2020; Lisuzzo et al.,
2020; Alam et al., 2020), sepiolite (Ferrari et al., 2017;
Kim et al., 2020; Fernández-Barranco et al., 2020;
Wang et al., 2020; Sun et al., 2020; Di Credico et al.,
2019) and attapulgite (palygorskite) (da Silva et al., 2020;
Tian et al., 2020; Yang et al., 2020; Elbassyoni et al., 2020).
Among the existing clay minerals, some have
remarkable characteristics like the Palygorskite (Pal) or
Attapulgite (ATP). Pal is the term recommended by
International Mineralogical Association (IMA) for
nomenclature, but the most used trade name for many
producers is ATP. In this study, the ATP denomination
will be used. This clay has a fibrous morphology with a
2:1 crystalline structure, which consists of two layers of
periodically inverted silica tetrahedral connected by an
octahedral layer. Each tetrahedral layer presents 180°
inversion for each sequence of four or six SiO4
tetrahedrons. This structure leads to the formation of
channels that extend throughout the longitudinal
direction of the fiber (Murray, 2020; Frost et al., 2001;
López-Galindo et al., 2007).
Bradley (1940) proposed the first structural pattern for
ATP and suggested that the clay mineral has the chemical
formula [(Mg, Al)2Si4O10(OH) .4H2O]. The ATP contains
three forms of water in its structure: (a) Coordinated
water, with cations of the octahedral leaf, (b) zeolitic
water, presents in the channels in which it interacts with
both the coordinated H2O molecule and the leaf
tetrahedral and (c) hydroxyl water, linked to the clay
structure in the center of the leaf octahedron (Xavier et al.,
2012). Figure 1 shows the chemical structure of the ATP
proposed by Bradley (1940).
Due to these structural aspects, ATP has interesting
properties such as high specific surface area, high
sorption, low surface charges, bleaching power and
thixotropic properties in the presence of electrolytes
(Haden and Schwint, 1967; Galán, 1996). Some of its
properties are listed in Table 1. In addition to these good
properties, ATP has a low-cost with a price of 0.2-0.5
Thais Ferreira da Silva et al. / American Journal of Engineering and Applied Sciences 2021, 14 (2): 292.307
DOI: 10.3844/ajeassp.2021.292.307
US$/Kg (as a comparison, the price of montmorillonite is
on average 10-15 US$/Kg). A rough cost estimation was
made based on the price of materials from the platform
The largest deposits of ATP group minerals around the
world were formed either by chemical sedimentation in
island seas and lakes, hydrothermal alteration of clays,
basaltic glass, or volcanic sediments in the open oceans or
by direct crystallization in calcareous soils (Singer and
Galan, 2000). These aspects of geological formation are
associated with the Mediterranean to semi-arid climate,
which reflects in the distribution of these minerals in low
latitudes, mainly in arid and semiarid areas of the world
(Singer et al., 2011). The location of the main reported
deposits of ATP is shown in Fig. 2.
Table 2 shows the chemical composition of ATP from
various sources around the world. All the ATPs in the
municipality of Guadalupe-PI have clay minerals:
Attapulgite, kaolinite, smectite, illite and chlorite, with a
predominance of ATP followed by kaolinite. Brazilian
ATP has a lower CaO and higher K2O content when
compared to ATPs from other countries. These
differences can be attributed to the content and nature of
the Guadalupe ATPs and/or the types and content of
contaminants (Baltar and Luz, 2003). The ATP geological
formation process allows the association with a large
number of accessory minerals, such as quartz, mica,
calcite, dolomite, among others, associated with the
occurrence of clay minerals; in addition to the presence
of organic matter. Often depending on the desired
application, it is necessary to separate the main clay
mineral from all these impurities (accessory minerals
and organic matter) in a process called acid activation
(Luz and Lins, 2008).
Table 1: Properties of attapulgite (Singer et al., 2011)
Melting point (°C) 1.550
Length (μm) 0.2-2.0
Width (Å) 100-300
Thickness (Å) 50-100
Channels dimensions (Å) 3.76.4
Specific surface area (m²/g) 150
Cation Exchange capacity (meqiv/100g) <25
Brookfield viscosity, suspension 10.000-12.000
at 6% in water at 5 rpm (cP)
Specific gravity (g/cm³) 2.0-2.3
Fig. 1: The chemical structure of ATP
Fig. 2: Attapulgite reported deposits
H2O zenolitic
Coordinate H2O
Attapulgite deposits
1. Guadalupe, Piaui (Brazil); 2. Guatemala; 3. Meigs-Attapulgus-Quincy District; 4. Theis and
Nianming (Senegal); 5. Torrejon and Bercimuel (Spain); 6. Ventzia, Grevena (Greece); 7. Cherkassy
(Ukraine); 8. Bhawnagar, Gujarat (India); 9. Maripalli, Andhra Pradesh (India); 10. Guanshan, Anhui
(China); 11. Lake Nerramyne (Australia); 12. Ipswich (Queensland)
Thais Ferreira da Silva et al. / American Journal of Engineering and Applied Sciences 2021, 14 (2): 292.307
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Table 2: Chemical composition of several samples of ATP from different locations (Baltar and Luz, 2003; Grim, 1969; Van Olphen and Fripiat, 1979)
São Pedro Clear São Pedro Dark Boa Vista Nizhnii-Novgorod Taodeni Saara Attapulgus
Content (%) Guadalupe Brazil Guadalupe Brazil Guadalupe Brazil Russia Algeria Georgia USA
SiO2 68.50 66.70 57.90 51.17 54.71 55.03
Al2O3 10.30 9.10 12.10 13.73 13.48 10.24
Fe2O3 4.00 3.70 7.20 1.55 2.10 3.53
FeO - - - 0.31 - -
MgO 5.60 7.40 4.90 6.40 5.44 0.49
CaO 0.17 0.17 0.10 2.89 2.79 -
K2O 1.20 0.83 2.20 - - 0.47
Na2O 0.10 0.11 0.14 - - -
H2O - - - 10.29 8.65 9.73
MnO 0.12 1.10 0.50 - - -
P2O5 0.03 0.03 0.05 - - -
TiO2 0.70 0.60 0.61 - - -
L.F.* 9.50 11.06 13.37 13.24 12.63 10.13
* L.F.- Loss to fire
Purification of ATP
The fibrous morphology, in addition to the presence of
the channels, results in a relatively large surface area for
this clay mineral. When channels are filled with
impurities, the surface area is between 70 to 150 m2/g. Once
activated, the area ranges from 120 to 210 m2/g (Frost et al.,
2001; Xavier et al., 2012; Augsburger et al., 1998).
For the removal of quartz and other minerals with
larger particle sizes, mainly two methods of physical
separation can be used. The first one is the separation by
sieving and the second method is the sedimentation
technique (Purcell and Parker, 2012). In the first method,
the ATP is passed through a sieving process using a 200
mesh (0.074 mm) sieve. For the second method,
sedimentation, water-based suspensions with the addition
of dispersing agents are required. The most widely used
dispersants in the ceramic industry are sodium-based,
such as sodium polyacrylate and sodium silicate.
Macromolecule sodium polyacrylate has the
characteristic of replacing the polar water molecules that
are poorly adsorbed in the phyllosilicate sheets,
promoting the fluidity of the material. Therefore, the
chains generate a double electrical layer, providing high
repulsion energy (de Souza et al., 2021). Sodium silicate
has the function of neutralizing the reactivity between
particles, due to the high surface energies they present in
ceramic powders when in a liquid medium. Van der Waals
forces act to destabilize the suspensions, forming clusters,
in this way, sodium silicate acts in the opposite way
towards these forces (Stempkowska et al., 2017). The
sedimentation method is based on the difference
between the density and/or particle size of minerals to
promote separation between them. In this way, a
mixing process combined with the action of dispersing
agents aims to break up clusters, leaving ATP
suspended particles while quartz and other impurities
settle in the background. From this, through physical
separation methods, non-ATP particles can be removed
(Murray, 2000; Purcell and Parker, 2012).
However, only the sieving and the sedimentation
technique are not effective to remove the total quartz
content, these techniques only reduce the amount of
quartz. Many authors have reported the difficulty of
completely removing quartz. Neto et al. (1993) when
analyzing the ATP from Guadalupe (Brazil), submitted
the samples to physical processing to reduce the quartz
content. Luz et al. (1988) through granulometric analysis
and X-Ray Diffraction (XRD) found a reduction in the
percentage of quartz the finer the granulometry.
In addition to physical separation methods, to
minimize other impurities like carbonates and organic
matter, a chemical and/or thermal treatment can be used.
These treatments also result in an improvement of some
properties, such as absorption, adsorption, specific surface
area, cation exchange capacity, among others. Chemical
treatment can be done by washing or immersing the clay in
acid or oxidizing substances. And heat treatment occurs
when the sample is heated to a certain temperature and then
remains for a certain period (Souza Santos, 1989).
Chemical treatment, also known as acid activation, is
very effective for the removal of organic matter and
carbonates (limestone and dolomite). It is carried out using
oxidizing reagents, such as Hydrogen peroxide (H2O2) and
strong acids, such as Hydrochloric Acid (HCl) and Sulfuric
Acid (H2SO4). H2O2 oxidizes organic matter and depending
on the amount of organic matter and the oxidant content
is observed a self-combustion (Verdade, 1954).
Using strong acids, the acid activation in the clay
occurs as follows: The soluble salts are partially
dissolved, resulting in a reduction of iron and aluminum
content; sodium and potassium ions go in solution unless
they are present into the silicate structure. The calcium ion
present is totally or partially solubilized, while the
magnesium ion can remain almost entirely in the clay. It
is important to note that acid activation allows the
improvement of the physical-chemical properties of ATP
without destroying its crystalline structure, such as
increasing the adsorption capacity, bleaching power and
mainly increasing the surface area (Frost et al., 2001).
Thais Ferreira da Silva et al. / American Journal of Engineering and Applied Sciences 2021, 14 (2): 292.307
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Fig. 3: (a) Diffractogram of raw ATP and ATP-acid and; (b) FEG-SEM micrographs of ATP-acid with magnification of 5000
An example of the effectiveness of acid treatment in
ATP is shown in the study that prepares
nanocomposites of Polyurethane (PU)/epoxy blends
with natural ATP and ATP-acid (Xu et al., 2019). The
results showed that the activation in ATP did not alter
the crystalline structures, it improved the glass
transition Temperature (Tg) of the composites,
however, the addition of activated ATP had a significant
reinforcing effect on the nanocomposite.
Figure 3a shows the diffractogram of raw ATP and
ATP after Acid Treatment (ATP-acid). Analyzing the
diffractogram, it is possible to identify four main phases:
Attapulgite (orthorhombic structure), calcite, dolomite
and quartz. The main ATP diffraction peaks occur at
approximately 8.6° and 19.9°. For quartz, the most
significant peak is found at 26.7° and for calcite around
29.3°. It is possible to observe that with the acid treatment
there was a reduction in the intensity of the peaks of
calcite and dolomite, indicating that these impurities are
partially removed from the ATP. In addition, the ATP
related peaks do not undergo significant changes, which
indicates that the acid treatment does not destroy its
crystalline structure (Fig. 3b) (Kim et al., 2020;
Elbassyoni et al., 2020).
Modification of ATP
In order to improve the interaction of ATP with
polymeric materials, in addition to acid activation, it is
desirable to perform a superficial modification of ATP.
As this clay mineral has a great capacity for cation
exchange, it is possible to perform organophilization by
cation exchange. Thus, ATP can be modified through
two different processes, silanization with the addition
of aminosilane and organophilization with the addition
of an organic compound.
The silanization reactions occur due to the interaction
by covalent bonding of the silylating agent with the silanol
groups that are on the surface of the clay minerals, as
shown in Fig. 4. Silylating agents are compounds that
have the general formula, (X)3Si(R)Y, in which X is an
alkoxide group (RO-), R is called a spacer group which is
usually (CH2)3 and Y determines the reactivity and
applicability of the compound, it assumes several
formulas, the most common being NH2, Cl, CN, NCO and
SH (Xue et al., 2010).
Another technique for the organophilization of clays is
by adding organic compounds. The organophilization
of clays is usually carried out using the ion exchange
technique, or better, with the replacement of cations
present in the clay, usually Na+. These cations are
easily exchangeable because they are monovalent and
they facilitate the exchange for organic cations of
quaternary ammonium salts (cationic surfactants) or
even other types of salts, in an aqueous solution. The
salts used in the modification have one or two groups
of long-chain hydrocarbons linked directly to a
nitrogen atom where the cationic part of the molecule is
located (Kakegawa and Ogawa, 2002).
These modifiers allow reducing the surface energy of
the clay, improving its wettability with the polymeric
matrix. This contributes to the increase in adhesion
between the inorganic phase and the polymeric matrix,
in addition to facilitating the penetration of the
polymeric chains between the clay agglomerates,
enabling dispersion and distribution in the polymeric
matrix (Xue et al., 2010).
Intensity (u.a.)
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
2 ()
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Fig. 4: Scheme of the interaction between the silylating agent and the surface of a clay mineral
Polymer/ATP Nanocomposites
For an overview of the scientific works related to the
use of ATP, an extensive search of the articles and patents
was realized on Web of Science and Espacenet databases,
respectively. To highlight the most recent works and new
trends, the research was limited to the period from 2010
to 2020. Also, to suit the scope of this review, the articles
and patents were researched with the specific filters of the
use of ATP in nanocomposites of the polymeric matrix.
Figure 5a shows the number of articles and patents
produced per year and Fig. 5b shows the different
processing methods of the polymer/ATP nanocomposites.
Studies on obtaining nanocomposites with the
addition of small clay minerals contents to the
thermoplastic matrix have shown significant
improvement in mechanical properties, water vapor
barrier and flammability resistance concerning neat
polymer (Gao et al., 2005).
Table 3 summarizes the developments of polymeric
nanocomposites-based on a thermoplastic matrix with the
addition of ATP, showing the type of ATP treatment,
processing method and the highlighted properties.
Thiré et al. (2011) developed nanocomposites of
PHBV/ATP organically modified with
hexadecyltrimethylammonium chloride. The addition
of 3 and 5 wt% organophilic ATP led to significant
changes in the properties of PHBV like a reduction in
the degree of crystallinity and a decrease in the
crystalline melting Temperature (Tm) and Tg.
The effect of surface modification of ATP on the
morphology and thermal properties of PA6 ATP
nanocomposites was studied by Cisneros‐Rosado et al.
(2018). The nanocomposites were prepared by melt
intercalation and the ATP was modified with
3-aminopropyl trimethoxysilane bromide and
tributylhexadecyl phosphonium. Experimental
evidence confirmed the grafting of surface agents into
ATP and, as expected, nanocomposites exhibited high
thermal stability and less surface energy. The ATP
particles favored the formation of the gamma
crystalline form and increased the decomposition
temperature of PA6.
da Silva et al. (2020) prepared PA12/ATP
nanocomposites by high-speed mixing using a
thermokinetic homogenizer. The addition of ATP
increased the modulus of elasticity, hardness, degree of
crystallinity and the apparent size of the crystallites.
The addition of up to 5% by mass of ATP increased the
tensile strength and deformation at rupture, after this
amount, the concentration increased significantly and
there was no good dispersion.
Wang et al. (2014a) prepared PBT/ATP
nanocomposites by in situ polymerization. The results
show that PBT/ATP nanocomposites have greater thermal
stability than neat PBT. The PBT/ATP nanocomposite
with a higher ATP content can delay the transport of
polymer chains to the growing crystals compared to the
nanocomposite PBT/ATP with a lower ATP content.
According to dynamic results from the mechanical
analysis, the nanocomposite PBT/ATP storage module
has been significantly improved and the addition of ATP
particles promotes the crystallization of PBT.
In addition to these improvements in mechanical and
thermal properties, some recent studies have also studied
the influence of ATP on the flammability of
nanocomposites. Besides the direct influence of ATP
on the flammability of materials, this clay mineral can
also be used as a synergetic agent in combination with
flame retardants. Hou et al. (2020) prepared
PA6/Melamine Cyanurate (MCA)/ATP nanocomposites
by two-step-melt polymerization. For the composition
with 6.2% of ATP and 11.5% of MCA, the mechanical
properties of the nanocomposites were up to 44.81 MPa
and the samples passed the UL-94 V-0 flammability
rating, with the Limited Oxygen Index (LOI) reaching
27.9%. Thus, the authors concluded that the
combination of MCA and ATP provided a marked
improvement in the flame retardancy of PA6, in
addition to maintaining its mechanical properties.
In general, ATP modifies the mechanical properties
of polymers, either in the natural or modified state and
has been shown to be a good alternative for the
replacement of lamellar clays such as montmorillonites
with the advantage of having a lower cost and a wide
world market to be explored.
OH + X3 Si(R)Y
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Fig. 5: (a) number of articles and patents produced per year from 2010 to 2020 and; (b) processing methods of the polymer/ATP
Table 3: Summarizes the developments of polymeric nanocomposites-based thermoplastic matrix with the addition of ATP, showing the type of ATP treatment, processing method and highlighted properties.
ATP Polymer Matrix ATP content Method* H ighlighted Properties Reference
Sieved (320 mesh) Carboxymethyl cellulose 5, 10, 20 and 25 wt% ISP The incorporation of ATP Wang and Wang (2010)
enhanced the swelling capability
Acid activation (HCl) Polyurethane-imide Non specified ISP This work opens up a possibility for Wang et al. (2010a)
the preparation of infrared low-
emissive materials
Sieved (320 mesh) Hydroxyethyl Non specified ISP The introduction of ATP into polymeric
Cellulose-g-PAA1 network can improve the water absorption rate Wang et al. (201)
Pretreated with H2O2 and PAN2 1-7 wt% SI A small amount of results in a homogeneously Yin et al. (2010a)
acid activated (HCl) stress transfer and energy dissipation, increasing
the mechanical properties
Dispersed into ethanol PP3 2-10 wt% MI The steady shear viscosities of the nanocomposites Zhang et al. (2010)
and silane are much higher than those of pure PP3 at lower
shear rates
Sieved (200 mesh) Guar Gum-g-Poly(Sodium Fixed ISP The composites exhibited improved swelling Shi et al. (2011)
Acrylate -co-Styrene) capacity and rate, pH-resistance, salt-resistance
and solvent-responsive properties
Pretreated with H2O2 and PAN2 0.5, 1, 3 and 5 wt% SI The analysis on the stead y shear rheology results Yin et al. (2010b)
acid activated (HCl) showed that elevating temperature may promote the
orientation effect of ATP nanorods on the PAN2 chains
Sieved (200 mesh) Methylcellulose 5, 10, 20 30 and 35 wt% ISP T he nanocomposite shows excellent on-off switching Wang et al. (2010b)
swelling characteristics between pH 2.0 and 7.4
Treated with surfactant PHBV4 1-5 wt% ISP The morphology can be adjusted in a wide range Thiré et al. (2011)
by controlling the contente of the ATP
Treated with surfactant PMMA5 Non specified ISP The different morphologies of ATP/PMMA5 Zhang et al. (2012)
composite particles can be adjusted in a wide range
by simply controlling the introduction of the ATP
Sieved (320 mesh) Psyllium-g-PAA1 5, 10, 20, 30 and 40 wt% ISP The nanocomposites possess excellent water An et al. (2012)
absorption in distilled water or saline solutions
Dispersed in P (MEO2MA-co- Non specified ISP The tensile strength, tensile modulus and an Wang and Chen (2012)
ethanol solution OEGMA-co-AAc) effective cross-linked chain density increased
with the increasing content of ATP
Purified (not specified) Poly (ethylene glycol) 1, 3 and 5 wt% ISP The hydrogel can continue to swell in an Wang et al. (2012)
and doped with Fe3O4 -based hydrogel alternating magnetic field after equilibrium
swelling in deionized water
Sieved (320 mesh) PBMA6 No n specified ISP The incorporation of ATP can improve the oil Wang et al. (2013)
absorbency of PBMA6
Silane coupling in PP3 5, 10 and 15 wt% MI The modulus, fracture strength and tensile Tang et al. (2013)
acid conditions strength enhanced
Grinded So dium carboxymethyl 0-10 wt% ISP Excellent pH-responsive behavior
cellulose-g-PAA1 and good regeneration ability Liu et al. (2013)
Natural PBSA7 1, 3, 5 and 7 wt% MI Nanocomposites revealed significant improvement Qi et al. (2013)
in mechanical properties, Especially the break
elongation of PBSA7/ATP nanocomposite with
1 wt% ATP
Natural PAA1 Non specified MI The composite showed well-connected open Chen et al. (2013)
nanoscale channels and pores in its structure
Washed with PoPD8 Non specified ISP PalPoPD8 sensor displays excellent analytical Luo et al. (2013)
distilled water performances for glucose determination
Washed with PmPD9 Non specified ISP Cr(VI) ions can be efficiently adsorbed onto Xie et al. (2014)
distilled water the PmPD9PG nanocomposite
Baked, grinded and PAA1 Non specified ISP The microgel had a high absorption capacity
acid activated (HCl) towards heavy metal ions, especially to Pb2+. Liu et al. (2014a)
Baked, grinded and PAA1 Non specified ISP The ATP/PAA1 nanocomposite hydrogel Zhu et al. (2014)
acid activated (HCl) showed high uptake toward a cationic dye
Natural Epoxy 3% Thermoset The simulation result revealed that nanoparticle can indeed Zhang et al. (2014)
Matrix change the crack initiation and propagation pattern
Already purified PBT10 1 and 3 wt% ISP ATP acts as a heterogeneous nucleating agent in PBT10 Wang et al. (2014a)
crystallization and accelerated the crystallization rate
Received doped Poly (ethylene glycol) 1 and 3 wt% I SP The microgels possess increasing pH response Yuan et al. (2014)
with Fe3O4 based microgel and excellent temperature-responsive characteristics
Number of publications
Number of patents
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Number of publications
Processing methods of polymer/attapulgite nanocomposites
Number of patents
In situ polymerization
Melt intercalation
Solution intercalation
Thais Ferreira da Silva et al. / American Journal of Engineering and Applied Sciences 2021, 14 (2): 292.307
DOI: 10.3844/ajeassp.2021.292.307
Tanle 3: Continue
Natural PAMPS11 Non specified ISP T he addition of appropriate amount of APT can effectively Xu et al. (2014)
improve the water absorbency and salt water performance of the
superabsorbent composites
Baked, grinded and PAA1 15 - 25wt% ISP The ATP/PAA1 hydrogel showed good adsorption Liu et al. (2014b)
acid activated (HCl) selectivity toward the Pb2+ ion
Silane treatment PP3 and LLDPE12 3, 5 and 7 phr MI Tensile modulus of all compositions increased initially Panda et al. (2014)
and then decreased, indicating embrittlement of polymer
Baked, grinded and PAA1 Non specified ISP The nanocomposite hydrogels showed a good J iang and Liu (2014)
acid activated (HCl) selective adsorption to Pb2+ at pH 5
Acid activated 13 5, 10 15 and 20 wt% MI The flame retardancy of the composites was improved Liu et al. (2014c)
Treated with HCl PEI14 Non specified ISP The nanocomposite proved to be a promising Han et al . (2014)
and H2O2 candidate for early tumor diagnosis
Modified with a PU15 Non specified ISP The storage modulus (Tg), tensile strength and Young's modulus Wang et al. (2014b)
silane coupling agent nanocomposites were enhanced with increased loading
Natural Chitosan/PVAl16 1-6 wt% SI Tensile strength increase Lu et al. (2015)
ATP firstly P(AAc-co-Am)17 Non specified ISP All nanocomposite hydrogels showed better Liu et al. (2015)
baked at 140°C; adsorption selectivity to Cu2+ and Pb2+
acid activation (HCl)
Natural PANI18 Non specified ISP FTIR showed a good polymer coating in the ceramic particles Chae et al. (2015)
Milled and sieved Hydroxyethyl cellulose Non specified ISP The hydrogel exhibited smart salt and Shi and Wang (2015)
(320 mesh) -based hydrogel pH responsive behaviors
Milled and sieved Epoxy resin Non specified Thermoset The prepared coating exhibited super hydrophobicity Yang et al. (2015)
(320 mesh) Matrix
ATP modified with PP-g-MA19 0.5-5 wt% MI Impact strength and tensile strength increase Chen et al. (2015)
Natural PVC20 5 phr MI The Vicat softening temperature showed an Wang et al. (2015)
improvement in the thermal stability
Washed in HCl and PBS21 1 - 8 wt% MI Tensile strength increased Zhang et al. (2016)
introduction of a silane
coupling agent KH-570
Centrifugation PS22 0.5 - 2 wt% ISP Higher Tg and poorer processability Zhu et al. (2016a)
(1500 rpm) and
acidactivation (HCl).
Acid activation (HCl) PAA1 Non specified ISP The material showed na exceptional Ce3+ adsorption Li et al. (2016)
Natural Chitosan 1-4 wt% ISP Fracture stress and elastic modulus were both
over 5 times more than that of neat polymer Wang and Chen (2016)
Dispersed in H2O/ PEBA23 Non specified SI CO2 permeability and CO2/N2 selectivity were improved Xiang et al. (2016)
ethanol solution
Natural PPy24 Non specified ISP Storage modulus and antibacterial activity were improved Zang et al. (2016)
Natural PAA-co-PVA25 Non specified ISP High water absorbency in pH range from 4 to 10 Ma et al. (2016)
Acid activation (HCl) PAA1 Non specified ISP Excellent regeneration and reusability Zhu et al. (2016b)
Natural Chitosan/PVAl16 Non specified ISP The material can be used in the treatment of
wastewater containing low-concentration Cu(II) ions Wang and Wang (2016)
Dissolved into 250 mL PANI18 Non specified ISP The material can be used as the electrode material Xie et al. (2016)
of 0.5 mol.L−i H2SO4 in supercapacitors
Dispersed into a solution EVA26 0.3-7 Phr MI Tear strength, peel strength and compression Shao et al. ( 2017)
of γ-Aminopropyltri- set were improved
ethoxysilane in isopropanol
Natural PEBA23 Non specified SI The material can be used for natural gas sweetening
or biogas purification Xiang et al. (2017)
Natural PLA27/PBAT28 1-7.5 wt%" MI Tensile strength and elongation at break increase. Zhou et al. (2017)
Thermally-Treated PU15 0. 5-2 wt% ISP Tensile strength and Elastic modulus increase. Lee et al. (2018)
Attapulgite (TAT)
Dispersed in silane EVA26 Non specified SI The pour point temperature was reduced Tu et al. (2018)
coupling agent and
organic acid solution.
Natural PASA29 Non specified ISP The water absorbency and retention and the Lu et al. (2018)
microstructure were significantly improved
ATP nanorods were PDMS30 0. 5-5 wt% SI Tensile strength increase Lee et al. (2018)
homogeneously dispersed
in Dimethylacetamide
Acid activation (HCl) PANI18 1.5% ISP The composites studied can be used as microwave-absorbing materials Bai et al. (2020)
Acid activation (HCl) Regenerated cellulose 5-20 wt% SI Tensile strength increased Wang et al. (2018)
Acid activation (HCl) PAA1 Non specified ISP Flame retardant and mechanical properties were Gao et al. (2019)
enhanced with the introduction of ATP
Natural Cellulose Non specified ISP Adsorption capacity of the nanocomposite was Chen et al. (2019)
increased by incorporation of ATP
Thermal activation Epoxy resin Non specified Thermoset The anticorrosive property of the waterborne Nan et al. (2019)
Matrix epoxy coating were improved
Natural PPy23 and PS22 2-3.3 wt% IS P Compression modulus increased Liu et al. (2019)
Acid activation (HCl) Chitosan 1-8 wt% IS P Tensile strength and elongation at break increase Tensile Hu et al. (2020a)
Acid activation (H2SO4) Chitosan 2-10 wt% SI strength increase and elongation at break decrease. Hu et al. (2020b)
Sieved (200 mesh) PA1231 1-10 wt% MI Elastic modulus increased with the addition of ATP Kim et al. ( 2020)
Acid activation (HCl) PAA1 Non specified ISP Increase of flame retardancy when combned with ZnO Gao et al. (2020)
Acid activation (HCl) Cellulose Non specified ISP Increase of heavy metal ions absorbance capacity Chen et al. (2020a)
NH2 and PMMA grafting PVDF32 1 and 2 wt% SI Increase in surface pores and strength and Tian et al. (2020)
decrease of contact angle
Dispersed in H2O/ HDPE33 2, 4, 6 and 8 wt% MI Increase in mechanical properties and flame retardancy Chen et al. (2020b)
ethanol solution
Co-Ni hydroxides grafting UHMWPE34 2 wt% MI Decrease in the friction coefficient and wear volume Meng et al. (2021)
Dispersion in 20% Cellulose 4 and 12 wt% ISP Increase in Cu2+ ions removal Ma et al. (2021)
NaCl solution
* ISP: In Situ Polymerization, SI: Solution Intercalation and MI: Melt Intercalation
1Poly (acrylic acid), 2Polyacrylonitrile, 3Polypropylene, 4Poly (3-hydro xybutyrate-co-3-hydroxyvalerate), 5Poly(methyl methacr ylate), 6Poly(butylmethacrylate), 7Poly(butylene succinate-co-butylene
adipate), 8Poly(o-phenylenediamine), 9Poly(m-phenylenediamine), 10Poly(butylene terephthalate), 11Poly(2-acrylamide-2-methylpropanesulphonic acid), 12Linear low density polyethylene, 13Polyamide
6, 14Polyethyleneimine, 15Polyurethane, 16Poly (vinyl alcohol), 17Poly (acrylic acid-co- acrylamide), 18Polyaniline, 19Maleic anhydride grafted polypropylene, 20Po ly (vinyl chloride), 21Poly (butylene
succinate), 22Polystyrene, 23Poly (ether-block-amide), 24Polypyrrole, 25Poly (acrylic acid)-co-Poly (vinyl alcohol), 26Ethylene-vinyl acetate, 27Poly (lactid acid), 28Poly (butylene adipate-co-terephthalate),
29Poly (aspartic acid), 30Polydimethylsiloxane, 31Polymide 12, 32Polyvinylidene fluoride, 33High-density polyethylene, 34Ultra high molecular weight polyethylene
Thais Ferreira da Silva et al. / American Journal of Engineering and Applied Sciences 2021, 14 (2): 292.307
DOI: 10.3844/ajeassp.2021.292.307
Future Perspectives
The era of nanotechnology has reached several sectors
in recent years, encompassing more and more specific
materials for different applications. The polymer/ATP
nanocomposites listed here highlight the growing search
for these materials with excellent properties. In the past
three years (2018-2020), some specific applications have
been studied, which drive new trends in applications for
ATP, such as flame retardant of cotton fabrics (Gao et al.,
2019), dye adsorption (Chen et al., 2019; Chen and Zhu,
2019), hydrogel membranes for wound dressing (Sun et al.,
2020), sustainable packaging (Wang et al., 2018) and fuel
cell applications (Hu et al., 2020a; 2020b).
Chen et al. (2019; Chen and Zhu, 2019) prepared a
nanocomposite hydrogel based on cellulose and ATP by a
facile method. The SEM micrographs showed that
nanocomposite hydrogel exhibited a porous structure and
rough inner surface and ATP was incorporated inside. The
addition of ATP reduced the swelling degree of
nanocomposite hydrogel and enhanced its adsorption
capacity. Through the results, the authors concluded that
the nanocomposite hydrogel prepared could be used in
removing dyes from wastewater.
Hu et al. (2020a; 2020b) prepared proton exchange
membranes composed of chitosan / modified organic ATP
for fuel cell applications. The composite membranes
exhibited better mechanical property, dimensional and
thermal stability compared to the neat chitoson
membrane. The proton conductivity of the composite
membrane is also increased, the composite membrane
with 4% by weight of ATP content exhibited the highest
proton conductivity of 26,2 mS cm1 at 80°C with 100%
relative humidity, which is 25.1% larger than the pure
chitosan membrane. These results can explore a simple
and green strategy for preparing chitosan-based proton
exchange membranes, which have great potential in the
application of proton exchange membrane fuel cells.
In addition to this trend of applications observed in the
last three years (2018-2020) and limited for the use in
nanocomposites, the specific properties of ATP also allow
for other promising advanced uses such as support of
nanoparticles for sensor devices and high-performing
catalysts, new adjuvants for vaccines, clay-biological
interfaces for tissue engineering and bioreactor devices
(López-Galindo et al., 2007).
ATP has interesting properties such as high specific
surface area, high sorption, low surface charges,
bleaching power and thixotropic properties in the
presence of electrolytes. These properties make ATP an
ideal candidate for reinforcing polymeric materials.
Different approaches and emerging technologies have
been applied to improve the thermal and mechanical
properties of polymer/ATP nanocomposites which can
extend the different chemical treatments used in ATP.
ATP mainly modifies the mechanical properties of
polymers, increasing the elastic modulus and tensile
strength either in the natural or modified state and with low
filler contents (even less than 6%). Regarding thermal
properties, ATP acts as a nucleating agent, increasing the
degree of crystallinity and the Tg of the polymeric matrices.
In this way, ATP is a good alternative for the replacement of
lamellar clays such as montmorillonites with the advantage
of having a lower cost (0.2-0.5 US$/Kg) and a wide world
market to be explored, which drives new trends in ATP
applications, such as flame retardant on cotton fabrics, dye
adsorption, hydrogel membranes for dressings, sustainable
packaging and fuel cell applications.
The authors are grateful to FAPESP (process
2018/09531-2), CNPq (Conselho Nacional de
Desenvolvimento Científico e Tecnológico, process
310196/2018-3, 305123/2018-1) and the Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior - Brasil
(CAPES) - Finance Code 001.
Author’s Contributions
All authors equally contributed in this work.
This article is original and contains unpublished
material. The corresponding author confirms that all of the
other authors have read and approved the manuscript and
no ethical issues involved.
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Linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) are polyolefins widely used in the packaging sector. Seeking to improve the mechanical properties with good cost-effectiveness, attapulgite (ATP) was chosen as a reinforcing filler for the polyolefins. ATP is a hydrated magnesium and aluminum clay mineral with a microfibrous morphology, and the purity of this filler depends on the deposit. ATP is associated with the presence of accessory minerals that need to be removed so as not to interfere with its final application. Thus, an ATP purification process was carried out through physical separation and chemical treatment with hydrogen peroxide (H 2 O 2) and sulfuric acid (H 2 SO 4). This purification process despite having a low yield and is very effective in reducing impurities and organic matter. This ATP was named ATPa. LLDPE/ATPa and HDPE/ATPa nanocomposites with the addition of 1, 3, and 5 wt% of ATPa were prepared by extrusion and hot pressing. The mechanical properties (Shore D hardness, tensile tests, and Izod impact strength), thermal properties (differential scanning calorimetry-DSC and thermogravimetric analysis-TGA), X-ray diffraction, rheological, and transmission scanning microscopy (TEM) were determined for these nanocompo-sites. The mechanical properties of the nanocomposites increased with the addition of ATPa. HDPE/ATPa nanocomposites showed more promise than LLDPE/ATPa nanocomposites. The addition of 5 wt% ATPa increased the tensile strength by 14% for the HDPE matrix and 5% for the LLDPE matrix and increased the elastic modulus by 46% for HDPE and 26% for LLDPE. K E Y W O R D S attapulgite, high-density polyethylene, linear low-density polyethylene, nanocomposites, polyolefins
In this work, Brazilian attapulgite (ATP) with different surface modifications is used as a mineral filler in the development of linear low‐density polyethylene (LLDPE) nanocomposites. As a raw mineral, Brazilian ATP has many impurities in its structural channels (ATPr). Thus, sodium polyacrylate, hydrogen peroxide, and sulfuric acid are used to remove impurities from ATPr in a process called acid activation (ATPa). Also, inorganic materials do not have good interfacial interaction with organic polymers. Therefore, as an alternative to this challenge, two surface modifications are made to the ATPa: silanization (ATPs) and organophilization (ATPo). ATPr, ATPa, ATPs, and ATPo are characterized by FT‐IR (Fourier transform infrared spectroscopy), XRD (X‐ray diffraction), TGA (thermogravimetric analysis), and FEG‐SEM (field emission gun scanning electron microscopy). The effectiveness of surface modifications is evaluated for LLDPE/ATP nanocomposites with the addition of 3 wt% ATP (ATPr, ATPa, ATPs, and ATPo) prepared by extrusion. The nanocomposites are analyzed by XRD, thermal characterization (differential scanning calorimetry—DSC), mechanical characterization (Shore D hardness, tensile test, and Izod impact strength), and morphological characteristics (SEM micrographs). It can be noted that the addition of treated ATP increases the mechanical properties. The silanization is more effective when compared to the organophilization treatment.
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Clays are very important from an economic and application point of view, as they are suitable hosts for organic compounds. In order to diversify the fields of application, they are structurally modified by physical or chemical methods with cationic species, and/or different bifunctional compounds, such as organosilanes. In this study, palygorskite was modified with (3-Aminopropyl) triethoxysilane, which was subsequently modified at the amino group by grafting an acetate residue. By using this strategy, two types of host hybrid materials were obtained on which curcumin derivatives were deposited. The composites obtained were structurally characterized and their photophysical properties were investigated in relation to the structure of the host matrices and interactions with curcumin-type visiting species. The hybrid composites have different colors (orange, yellow, pink), depending on the polarity of the inorganic matrices modulated by different organic groups grafted at the surface. Fluorescence emission in the visible range is characterized by the presence of two emission maxima, one belonging to the chromophore and the other influenced by the physical interactions between auxochromes and host matrices. These hybrid materials, compared to other composite structures, are obtained by a simple adsorption process. They are temperature stable in aggressive environments (acid/base) and render the fluorescent properties of dyes redundant, with improved luminescent performance compared to them.
Organic-inorganic nanocomposites have attracted great interest due to the remarkable improvement in mechanical properties when compared to neat polymers. The use of a low-cost nanofiller added to good properties becomes attractive to the industry. Attapulgite (ATP) is a very interesting nanofiller alternative, especially when used with polyolefins, as in the case of high-density polyethylene (HDPE). However, this system is not simple, as HDPE is a nonpolar polyolefin that can cause low dispersion of ATP. One way to increase the interaction between these phases is the surface modification of ATP. In this work, the surface of ATP was modified using trimethylamine hydrochloride. HDPE/ATP nanocomposites with 1 and 5 wt% of raw ATP (ATPr) or organophilic ATP (ATPo) were prepared by extrusion. The effectiveness of the organophilization process of ATP was evaluated by X-ray diffrac-tion, mechanical properties (Shore D hardness and tensile test), and thermal properties (thermogravimetric analysis and differential scanning calorimetry), contact angle, and scanning electron microscopy. In the HDPE/ATPo nanocomposites, it was possible to observe an improvement in mechanical and thermal properties when compared to HDPE/ATPr nanocomposites. The organophilization of ATP promoted a greater interaction between the phases, contributing to a better dispersion of ATP in the HDPE matrix.
Attapulgite (ATP) is a low-cost hydrated clay mineral of aluminum and magnesium and can be used for the preparation of linear low-density polyethylene (LLDPE) nanocomposites. However, the ATP contains accessory minerals that can harm their performance and hinder their polymer interaction. Then, a purification process of this clay mineral is necessary to raise the interactions between ATP and LLDPE. Furthermore, the non-polar nature of LLDPE can also hinder these interactions. One way to improve these interactions is the surface modification of ATP. In this way, the ATP was modified using aminosilane (3-aminopropyl) triethoxysilane (APTES). Raw ATP (ATPr), purified ATP (ATPp), and silanized ATP (ATPs) were characterized, and LLDPE/ATP nanocomposites with 3 and 5 wt% of ATPr, ATPp, and ATPs were prepared by extrusion. The nanocomposites were characterized by scanning electron microscopy (SEM), mechanical properties (tensile tests, Shore D hardness, and impact strength), and X-ray diffraction. APTES was grafted onto the clay surface. The APTES did not modify the crystal structure of ATP and, in addition, it improved the mechanical properties of LLDPE/ATPs nanocomposites. The addition of 5 wt% of ATPs increases the tensile strength, elastic modulus, and Shore D hardness, in addition to improving the dispersion of nanoclay in the polymer matrix.
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Palygorskite (Pal) is a natural clay mineral with fibrous morphology and high surface area. Depending on the geological origin, it presents impurities, such as quartz and carbonates, which can harm some of its properties. Therefore, this work seeks to define a viable methodology for the purification of a Brazilian Pal. Two types of mixing processes (sonication and milling) and two types of dispersing agents (sodium silicate and sodium polyacrylate) were investigated. In addition, a subsequent acid activation with hydrogen peroxide and sulfuric acid was performed for complete purification. The viability of the purification of Pal was confirmed by X-ray diffraction, X-ray fluorescence, and thermogravimetric analyses. The sonication mixture process and the use of sodium polyacrylate as a dispersing agent were more effective. In addition, BET analysis showed an increase in the surface area of Pal, and scanning electron microscopy confirmed the permanence of its fibrous morphology after the purification steps.
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Loose specimens with a void ratio of 0.86, corresponding to a relative density of 30% for the pure sand, and normal stresses of 50, 100 and 150 kPa were used in this work to study strength and deformation behaviour of sand rubber mixtures. Three types of rubber particles with D-rubber/D-sand = 0.25, 1, and 4, and different rubber to sand ratio of 5, 10, 15, 20, 25, 30, 40 and 50% were investigated by performing more than 300 direct shear tests. The shear strength and deformation characteristics of sand-rubber mixtures were dependent on rubber proportions of the mixtures and size ratio. Angle of friction and cohesion intercept increased and reduced when up to 20% rubber fraction was used, but reduced and increased afterwards. Dimensional analysis of the data suggested that shear strength is a weak function of the rubber fraction for the types of rubber particles used in this study.
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Quasi-brittle materials such as rock are rate sensitive materials and their behaviour under dynamic loading is not identical with that under static loading. In this study, numerical Brazilian tensile tests are conducted using a Split Hopkinson Pressure Bar system in an attempt to reproduce the dynamic increase factors (DIF) of the experimental tests. The rock is modelled by a bonded particle system made of spherical particles which interact at the contact points. The numerical results indicate that while the bonded particle system with a simple contact bond model can closely mimic the static behaviour of the sandstone specimens, it lacks what is needed for a rate dependent material. Therefore, a micromechanical model in which the contact bond strength is allowed to vary in proportion to the relative velocity of the involved particles is introduced. It is shown that the modified model can reproduce the physical tests data reported in the literature. In particular, with the application of strength enhancement coefficients in the range of 0–16 × 105, DIF values of 1.1–13 are obtained in the indirect tensile Brazilian tests, and the induced strain rate in the specimen is in 10–1000 s−1 range. Our preliminary study indicates that the model, consistent with the fact reported for the quasi-brittle materials, shows different rate-dependent sensitivity and dynamic strength enhancement in tension and compression. The micromechanical parameters in the proposed model can be adjusted to reproduce the physical rock strength, and that the shape of the reflected and transmitted numerical waves can be modified to approach those in the physical tests.
Conference Paper
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Rock is a rate dependent material and this rate dependency needs to be considered when dynamic loading such as rock blasting is of interest. In this study, CA3 computer program which is a hybrid bonded particle-finite element program is used to numerically simulate the Brazilian tensile test in the Split Hopkinson Pressure Bar (SHPB) testing. The rock is idealized using the Bonded Particle Model (BPM) while the incident and transmission bars are simulated by a finite element system. It is shown that the induced damage and brittle failure in the Brazilian specimen is consistent with the physical observation. On the other hand, the dynamic tensile strength of the simulated rock is much smaller than the physical result suggesting that inertia alone is not sufficient to capture the strength enhancement observed in reality. To remedy this problem, a micro-mechanical model is proposed in which the strength parameters of the particles are modified as exponential functions of the relative velocity of the involved particles at the contact points. It is shown that the proposed micromechanical model is capable of producing much more realistic results, i.e. the rock strength enhancement due to the applied strain rate can be captured. The numerical results are compared with some published physical tests data and discussed.
This work proposed a facile and effective method to fabricate attapulgite (ATP)@cellulose composite foams. ATP nanorods were integrated into cellulosic matrix via mixing and freeze-drying process. The carboxylated nanocellulose served as skeleton for supporting and dispersing ATP. Moreover, the addition of CaCl2 could improve the mechanical stability of the composites and ultrahigh ATP loadings (> 80 wt%) could be achieved. In the adsorption test, a high metal ion removal efficiency was observed and the hybrid foams can be easily recycled and regenerated. The adsorption equilibrium data were well described by Langmuir isotherm model with a maximum adsorption capacity of 116.5 mg/g. There are three reasons to the good adsorption performance: 1) the hierarchal pore structure, 2) the good dispersion of ATP, and 3) the presence of abundant surface carboxyl groups. Such [email protected] foams are biodegradable, facile to recover, flame-retardant and non-toxic, with great potential for water purification.
We propose a stochastic multi-scale method to quantify the most significant input parameters influencing the heat conductivity of polymeric nano-composites (PNCs) with clay reinforcement. Therefore, a surrogate based global sensitivity analysis is coupled with a hierarchical multi-scale method employing computational homogenization. The effect of the conductivity of the fibers and the matrix, the Kapitza resistance, volume fraction and aspect ratio on the ’macroscopic’ conductivity of the composite is systematically studied. We show that all selected surrogate models yield consistently the conclusions that the most influential input parameters are the aspect ratio followed by the volume fraction. The Kapitza Resistance has no significant effect on the thermal conductivity of the PNCs. The most accurate surrogate model in terms of the R² value is the moving least square (MLS).
In this study, attapulgite (ATP) nanofibers were modified by hydrotalcite-like cobalt-nickel via hydrothermal (named ATP-CoNi(H)) and co-precipitation (named ATP-CoNi(C)) method, respectively. The morphology and the composition of the ATP-CoNi hybrids were investigated. Meanwhile, the fretting wear properties of ultra-high molecular weight polyethylene (UHMWPE)-based composites reinforced by ATP and two kinds of ATP-CoNi hybrids at 2 wt% content were investigated. The results show that ATP-CoNi hybrids exhibit better fretting wear properties than pure ATP in the UHMWPE matrix. Thereinto, the ATP-CoNi(C) nanofibers present the best antifriction property that the friction coefficient and wear volume severally decreased by 27% and 47%. It is attributed to the optimal interfacial bonding between the nanofibers and the matrix, which makes the dense structure of the composite.
Biopolymers as alternative to fossils-derived polymers are attracting the interest of researcher in material science. Besides the economic advantages, the sustainability makes polysaccharides ideal candidates to prepare films and formulations. The addition of Halloysite nanotubes as green inorganic fillers was exploited to improve the physico-chemical properties and to introduce smart response abilities to the material. Halloysite is a natural tubular nanomaterial with hollow cavity and large aspect ratio. The effect of polymer charge on the morphology and mesoscopic properties of polysaccharides/halloysite nanocomposites has been highlighted. Different strategies (solvent casting, lyophilization, cryoscopic technique) for the preparation of nanocomposites have been described. In addition, we present novel protocols for the fabrication of polysaccharides/halloysite nanocomposites suitable as drug delivery systems. The emerging halloysite-based bionanocomposites are addressed to applications such as biomedicine, packaging, corrosion protection and restoration of cultural heritages. This review provides an overview of the recent progress achieved on halloysite-polysaccharides nanocomposites.
A fused-deposition modeling (FDM) 3D-printed polyethylene terephthalate glycol (PETG)–sepiolite composite showed effective synergetic mechanical reinforcement in tensile testing compared to an injection-molded composite. The results showed that the addition of 3 phr sepiolite improved the tensile strength of 3D-printed PETG samples by 35.4%, while the tensile strength of injection-molded PETG samples was improved by 7.2%. To confirm these phenomena, FDM PETG–sepiolite composites were investigated by small-angle X-ray scattering to correlate the nanostructures of the composites with their mechanical strengths. The small-angle X-ray scattering data and transmission electron microscopy observations demonstrated that needle-shaped sepiolite particles were aligned in the printing direction. This fine oriented nanostructure formed during 3D printing created a synergistic effect that improved the material properties of the composite. These novel PETG–sepiolite composites with enhanced mechanical properties can be promising materials fabricated via FDM 3D printing.
Some modified attapulgites (ATPs), such as surface modified by amino (‐NH2) or polymethylmethacrylate (PMMA) were used to prepare polyvinylidene fluoride (PVDF)/ATP composite ultrafiltration membranes by nonsolvent induced phase separation method. The excellent compatibility between PMMA or amino and PVDF may promote the dispersion of ATP in PVDF. The thermal, mechanical, hydrophilic, and micro‐morphology of the composite ultrafiltration membranes were characterized. The results showed that with the addition of the modified ATP, the properties of the membranes, such as mechanical and hydrophilic, were improved. When the content of ATP‐g‐PMMA was 2%, the overall performance of the PVDF composite membranes was the best.