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Evaluation of Recyclability of Waste Mobile Phone Plastics

Authors:
  • Central Institute of Petrochemicals Engineering and Technology (CIPET) , Bhubaneswar
  • Indian Patent Office

Abstract and Figures

Plastic components from waste mobile phones were sorted and characterized using visual, spectroscopic and thermal methods. The mechanical properties of the recovered plastics were investigated by comparing with commercially used reference materials. The results revealed the practical feasibility of these recovered plastics to make new products through mechanical recycling. The samples were also tested for brominated flame retardants (BFRs) using gas chromatography-mass spectrometry (GC/MS) technique and the results indicated the absence of BFR in recovered plastics, hence these can be processed without any risk of BFR toxicity.
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112
International Journal of Environmental Engineering IJEE
Volume 2: Issue 2 [ISSN: 2374-1724]
Publication Date: 30 October, 2015
Evaluation of Recyclability of Waste Mobile Phone
Plastics
[Smita Mohanty, P. Sarath, Sateesh Bonda, S. K. Nayak]
Abstract Plastic components from waste mobile phones were
sorted and characterized using visual, spectroscopic and
thermal methods. The mechanical properties of the recovered
plastics were investigated by comparing with commercially
used reference materials. The results revealed the practical
feasibility of these recovered plastics to make new products
through mechanical recycling. The samples were also tested for
brominated flame retardants (BFRs) using gas
chromatography-mass spectrometry (GC/MS) technique and
the results indicated the absence of BFR in recovered plastics,
hence these can be processed without any risk of BFR toxicity.
Keywords Mobile Phone Waste Valorisation, Plastics
identification, Estimation of Recyclability, Plastics Recycling
I. Introduction
The fast growth in electrical and electronic equipment
industry generated a relatively new kind of waste stream,
termed as Waste Electronic and Electrical Equipment
(WEEE) or simply, e-waste and it has become a major area
of concern throughout the globe due to the vast amount of e-
waste disposed every year [1]. Among WEEE, mobile phone
waste has gained considerable attention in the recent years.
According to latest Gartner reports, mobile phones have
contributed to more than 50% of total sales of electronic
products (in numbers), out of which smart phones hold a
major share. But surprisingly, mobile phones are one of the
least recovered and recycled products of electronic wastes
[2].
India stands second in the global telecom network
having more than 750 million mobile subscribers [3]. The
Smita Mohanty
Laboratory for Advanced Research in Polymeric Materials (LARPM)
Central Institute of Plastics Engineering and Technology (CIPET)
Bhubaneswar, India
P. Sarath
Central Institute of Plastics Engineering and Technology (CIPET)
Chennai, India
Sateesh Bonda
Laboratory for Advanced Research in Polymeric Materials (LARPM)
Central Institute of Plastics Engineering and Technology (CIPET)
Bhubaneswar, India
Sanjay K Nayak
Central Institute of Plastics Engineering and Technology (CIPET)
Bhubaneswar, India
mobile phone waste volume is accordingly escalating at a
fast pace owing to their very short life cycles. India, being a
developing nation, reusing or recycling mobile phone
materials is an efficient way to reduce and manage the
mobile phone wastes. But mobile phones contain a large
number of materials and components making them highly
complex and difficult to segregate for further recycling.
Even though many researchers and industries have
developed many processes for quick dismantling and
segregation of mobile phone wastes, the recycling rate is
still quite low owing to the very limited awareness of the
customer [4].
From the various mobile phone waste management
literatures, it is clear that plastics are the prime constituents
in mobile phones, which are easily acquirable for recycling
and contributes up to 40%-60% of all materials used in
mobile phones. Also, such articles indicate that major share
of plastics used in mobile phones is made up by engineering
grade plastics such as PC, PC/ABS blends, HIPS and ABS,
which may still possess high value in terms of performance
and economy, making them ideal for reuse and recycling
[5].
In the present work, plastic components dismantled from
waste mobile phones, collected from recycling plants, have
been categorized using conventional identification methods
such as generic marking of plastic products supported by
advanced characterization techniques such as FTIR and
Differential Scanning Calorimetry (DSC). Thermal and
mechanical properties of these recovered waste plastics were
evaluated and the data has been corroborated with reference
materials to assess their reusability and sustainability
towards application sector. The present work also highlights
the presence of brominated flame retardants on the selected
mobile phone components. The plastics from 2nd and 3rd
generation mobile phones have been considered in the
present study.
II. Material and Methods
Plastic components from waste mobile phones for
current study was collected from a local recycling facility.
The work was divided into different stages. Initially, the
plastic components from mobile phone waste were
segregated for identification. These parts were then
segregated based on the polymeric markings (as per ISO
1043) during the second stage, and were sub-divided into
parts with and without marking and also as per the type of
polymer, as shown in Table 1. The parts with no generic
markings (F-NC, B-NC and Key-P) were melt-mixed during
third stage, using a twin screw extruder (M/s Thermo Fisher,
USA, Haake Rheomex OS PTW 16) to get a uniform
composition for better FTIR identification studies [18]. The
parts that had markings were directly sent to FTIR analysis
(M/s Thermo Scientific, USA, Nicolet 6700, 4000cm-1 to
400cm-1) in fourth stage.
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International Journal of Environmental Engineering IJEE
Volume 2: Issue 2 [ISSN: 2374-1724]
Publication Date: 30 October, 2015
TABLE 1. TYPES OF MATERIALS IN CURRENT WORK WITH SUB-
CATEGORIES AND CODES
Differential Scanning Calorimetry (DSC) measurements
were carried out using a M/s TA Instruments, USA, Q20
under nitrogen using a heating rate of 10°C/min, from -70°C
to 250°C. Thermogravimetric analysis (TGA) was carried
out in a M/s TA Instruments, USA, Q50 under nitrogen with
a heating rate of 10°C/min, from room temperature to
700°C. Also a GC/MS analysis was done to ensure the
samples are BFR-free (Thermotrace GC Ultra Thermo
DSQ II GC-MS system under electron ionization model).
Tensile and flexural (3-point bend mode) testing was carried
out using an Universal Testing Machine (M/s Instron, UK,
Instron 3382 UTM) machine fitted with a 100kN load cell
operated at a cross-head speed of 5mm/min. Test specimens
for tensile testing (165X19X3.2mm, as per ASTM D638)
and flexural testing (127X13.5X3.2mm, as per ASTM
D790) were preconditioned for 24 hours under standard
conditions prior to testing. Combination of Tinius Olsen IT
504 Plastic impact tester with Tinius Olsen 899 Notch
cutting machine was used for Izod impact testing in
accordance with ASTM D 256 samples with and without
notch. Heat Deflection Temperature (HDT) of the samples
was also measured as per ASTM D648 (M/s Gotech,
Taiwan, HV-2000-C3) at a heating rate of 2°C/min.
III. Results and Discussion
A. Sorting and Identification
After preliminary identification, around four thousand
numbers of mobile components were sorted according to the
product type. markings. Fig. 3 represents the quantitative
data of sorting process.
FIGURE 1. PRELIMINARY SORTING RESULTS OF PLASTICS RECOVERED
FROM MOBILE PHONE WASTE ( VOLUME IN NUMBERS)
Among these components, back casings were high in
volume followed by keypads, whereas front casings were
relatively low. This may be due to rapid growth in touch
screen phone sales. Also, it is important to note that a major
share of plastics had no generic markings. For further
identification of these parts, FTIR analysis was adopted.
B. FTIR Analysis
Fig. 2 shows the FTIR spectra of the products recovered
(F-NC, B-NC and Key-P) from mobile phone waste that had
no marking.
FIGURE 2. FTIR SPECTRA COMPARISON of F-NC, B-NC, Key-P
The observed multiple sharp peaks at (13001000) cm-1
and 1768cm-1 are indicative of carbonyl stretching and
confirms the presence of polycarbonate in all three
materials. Further, minor peaks were observed around
1600cm-1 and 1500cm-1 indicating the aromatic in-ring
vibration which might be due to the possible presence of
styrene from ABS, indicating that these materials might be
also a blend of PC/ABS [6]. The FTIR spectra of Key-P also
showed significant vibrations at 1600cm-1 and 965cm-1
indicating K-P might be a mix of high impact polystyrene
and polycarbonate. The spectral peaks identified from Fig.
3, such as; 2966cm-1 (Si-OCH3), 1258cm-1, 862cm-1 and
785cm-1 (Si-CH3) and 1005cm-1 (Si-O-Si) positively
identified Key-E as silicone rubber [7].
FIGURE 3. FTIR SPECTRA of Key-E
The products with generic markings were also checked
with FTIR analysis and it was found that products were in
complete conformance with their respective markings. Thus
it is clear that together with generic markings and FTIR
analysis, a complete identification for the plastics in mobile
waste stream is possible.
No
Category
Sub Category
Assigned Code
1
Front Casing
With marking
-
2
Without marking
F-NC
3
Back casing
With marking
-
4
Without marking
B-|NC
5
Keypad
Plastic
Key-P
6
Elastomeric
Key-E
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International Journal of Environmental Engineering IJEE
Volume 2: Issue 2 [ISSN: 2374-1724]
Publication Date: 30 October, 2015
C. Thermal Analysis
For detailed identification of recovered plastic parts,
DSC and TGA studies were conducted and are represented
in Fig. 4 (a) and (b).
FIGURE 4. (A) DSC THERMOGRAMS (B) TGA WEIGHT LOSS CURVES FOR B-
NC, F-NC, KEY-P, AND KEY-E
It can be understood from the DSC thermograms, shown
in Fig. 4(a), that both F-NC and B-NC show single glass
transition (Tg 140°C 145°C, which is close to the Tg value
of polycarbonate material (140°C - 150°C) [8]. This
interpretation is also in line with FTIR spectra, which
indicated these two materials consist of significant
polycarbonate peaks.
The DSC of K-P shows a Tg around 100°C and a sharp
Tm around 225°C, both indicating the possible presence of
polystyrene. Thus it can be assumed that K-P is a blend of
PC with PS or HIPS. The calorimetric study of K-E was
performed over -70°C to 0°C (Figure 4 (a) inset) and a broad
melting peak has been observed at -43°C, which is typical of
filled silicone rubber material [9].
Fig. 4(b) shows the weight loss curves of F-NC, B-NC,
Key-P and Key-E. It is observed that both F-NC and B-NC
had degradation temperatures between 470°C and 500°C,
supporting the FTIR and DSC results. The weight loss curve
of K-P showed two-step degradation as it is a blend of
different components which has been predicted by DSC and
FTIR results. These two degradations of K-P can be
attributed to polystyrene (300°C to 450°C) and
polycarbonate (450°C to 550°C). TGA results of K-E
showed around 55% of residue at 600°C, which is a typical
observation of silicone rubber materials containing inorganic
fillers.
D. GC/MS Analysis
GC/MS analysis of the samples was conducted to ensure
that the recovered plastics were free from any kind of
brominated flame retardants. The parts with generic
markings can reveal the information regarding flame
retardants type and quantity. It was observed in the current
study that the parts which had generic markings showed no
sign of BFRs. To ensure the absence of BFRs in the parts
without, they were analyzed using GC/MS.
Fig. 5 shows the ion chromatograms obtained for the
different samples. The results were matched with mass
spectral reference library (NIST2011.L) for brominated
flame retardants. The search was run for all brominated
compounds from di-bromo to deca-bromo compositions.
Although several peaks were observed, none of them
corresponded to any of the known BFR compounds. These
results are synonymous with an earlier work done by Chen
et al. (2012) [10] on their mobile phone housings.
FIGURE 5. ION CHROMATOGRAMS OBTAINED FROM GC/MS ANALYSIS OF
DIFFERENT SAMPLES; (A) FC-N, (B) BC-N AND (C) K-P
Hence, the non-existence of BFRs in the parts which are
recovered from the mobile waste streams in the current
study suggests that the materials can be recycled without
any toxic concerns.
E. Mechanical Properties of Recovered
Plastics
The mechanical properties of plastics recovered from
mobile waste were studied to see how effectively they can
be recycled into new products. The properties of parts were
compared with a PC/ABS alloy (Cycoloy 1200HF), which is
widely used in electrical and electronic equipment (EEE)
manufacturing with reference to product datasheet.
The mechanical properties of PC/ABS based FC-N and
BC-N were compared with commercial reference material
data sheet and is shown in Fig. 6. It is observed that the
flexural (strength and modulus) properties are at par with the
reference data within the standard deviation limits.
FIGURE 6. PROPERTIES OF RECOVERED PLASTICS (WITHOUT GENERIC
MARKING) IN COMPARISON WITH REFERENCE MATERIAL DATA
Whereas, a decrease in tensile strength, tensile modulus
and impact strength have been observed compared to
reference material. This might be indication of some amount
of degradation to the parts during its service life. The
unsaturated sites such as polybutadiene (PBD) in ABS and
carbonyl groups in polycarbonate are susceptible to
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International Journal of Environmental Engineering IJEE
Volume 2: Issue 2 [ISSN: 2374-1724]
Publication Date: 30 October, 2015
degradation under ageing process, resulting in strength
properties. The reported data is also in line with the various
related earlier works [6, 8]. From the Fig. 1, one can
understand polycarbonate is also used solely to make the
mobile phone components. Therefore a comparative report
on mechanical and thermal properties of PC based products
with a standard PC reference material has been presented in
Fig. 7.
FIGURE 7. PROPERTIES OF RECOVERED PC IN COMPARISON WITH
REFERENCE MATERIAL DATA
It is also understood from the data that only tensile and
impact properties are significantly lower compared to the
reference material, which is mostly due to the possible chain
scission resulting from ageing during service life of the
products.
The comparison data of mechanical strongly suggest the
potential use of recovered plastics to tailor the needs of
application sectors. The low impact strength can be
effectively improved with the incorporation of rubber
particles. As a futuristic work, one can grind the elastomeric
components recovered from mobile phones, such as
elastomeric keypads, to a fine powder and can be
incorporated as a toughening agent within the recovered
plastics in order to improve their impact strength.
IV. Conclusion
The polymeric parts from waste mobile phones were
identified by combining visual, spectroscopic and thermal
techniques. The polymeric marking was greatly effective in
identifying a major share of the mobile plastic components.
The parts that had no polymeric markings were identified by
FTIR and thermal analysis methods. The collected polymers
were found to have no kind of brominated flame retardants
as per GCMS analysis and therefore can be reprocessed
without any environmental toxicity concerns. The
comparison of mechanical properties of recovered plastics
with reference materials revealed that most of the properties
are at par with the reference materials even after its service
life. The short life of mobile phones can generate waste
materials having good properties, which can be recycled
with/without further modifications to tailor the industrial
needs. Hence, the present work suggests that the plastics
from mobile phone waste has sufficient potential for being
recycled into new products.
Acknowledgment
The authors would like to thank Department of
Chemicals and Petrochemicals, Government of India for the
financial support.
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The cell phone market is developing at a rapid speed. Today there are more than 1.6billion consumers in the world, and the lifetime of a cell phone is less than 2years. As a consequence, there is an increase in the waste associated to this product, and many alternatives to the disposal of the cell phones are being studied, such as recycling which shows to be the most important. It is crucial to know what materials constitute the cell phone in order to carry out recycling and determine environmental and economical issues. This work presents an evaluation of the cell phone components, characterizing the raw materials and some properties of the recycled materials.
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Market Share Analysis of Mobile Phones in 2013, Worldwide
  • Gartner
Gartner, "Market Share Analysis of Mobile Phones in 2013, Worldwide", From Gartner Inc: https://www.gartner.com/doc/2665319/market-share-analysis-mobilephones, accessed 18 May 2015.