Advances in Materials Physics and Chemistry, 2013, 3, 327-331
Published Online December 2013 (
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Effectiveness of Talc Filler on Thermal Resistance of
Recycled PET Blends
Kazushi Yamada1*, Supaphorn Thumsorn2
1Kyoto Institute of Technology, Kyoto, Japan
2Rajamangala University of Technology Thanyaburi, Pathum Thani, Thailand
Email: *
Received October 27, 2013; revised November 28, 2013; accepted December 12, 2013
Copyright © 2013 Kazushi Yamada, Supaphorn Thumsorn. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited. In accordance of the Creative Commons Attribution License all Copyrights © 2013 are reserved for SCIRP and the
owner of the intellectual property Kazushi Yamada, Supaphorn Thumsorn. All Copyright © 2013 are guarded by law and by SCIRP
as a guardian.
In general, high mechanical properties such as higher impact strength and thermal resistance are required for injection
molded applications. Recycled PET (RPET) is well known to exhibit brittle behavior in the presence of notches and
indicated the low heat distortion temperature. Therefore, we tried to improve the toughness and thermal resistance
properties of RPET by incorporating E-GMA, talc filler and engineering plastics as an impact modifier and talc to in-
crease the rigidity and heat distortion temperature of RPET. As a result, these blends with E-GMA exhibited signifi-
cantly higher stiffness an d strength especially with increasing E-GMA content. In addition, these blends with talc filler
indicated the high heat distortion temperature due to the increase of the crystalinity of RPET blends. Therefore, it was
found that talc played an important role in enhancing the heat resistance of RPET.
Keywords: Recycled PET; Injection Moldings; Talc; Heat Distortion Temperature
1. Introduction
Polyethylene terephthalate (PET) is widely used for syn-
thetic fiber, beverage, food and other liquid container and
so on, which constitu tes a large portion of post consumer
wastes. In the present day, the volume of the PET bottle
products greatly increased. For example, the annual
volume of consumption of PET drinking bottle in Japan
[1] was 338,654 tons in 2000. However, in 2008, a 50%
increase in volume to 520,120 tons was reco rded. There-
fore, recycling of PET bottles offers a very practical so-
lution to reduce landfill waste thus preventing environ-
mental problems. Indeed, there are some researches [2-7]
about recycled PET (RPET) injection moldings from
PET bottles.
Neat PET is known to possess high elastic modulus,
strength and toughness. However, recycled PET (RPET)
is more susceptible to impact loadings and have lower
heat distortion resistance. In order to enhance its tough-
ness, impact modifiers are often incorporated into RPET.
In our previous work, the notched impact resistance of
RPET was significantly enhanced when a polyethyl-ene-
glycidyl-methacrylate (E-GMA) based impact modifier
was incorporated [6]. However, this led to deterioration
in stiffness and yield strength of the material. Further-
more, the material would deform easily even when ex-
posed to temperatures of around 50˚C. In order to im-
prove the stiffness and heat distortion resistance of the
material, talc, which is a popular mineral filler typically
used with polyprop ylene, was incorporated into RPET in
this study. In addition, RPET blends with polybuty-
lene-terephthalate (PBT) were prepared in order to elu-
cidate the effect of talc filler as a nucleation of crystalli-
zation. The effects of talc loading on the heat distortion
temperature, fracture behavior and static and dynamic
mechanical performance of the composites were eluci-
2. Experimental
2.1. Materials
Recycled poly (ethylene terephthalate) (RPET) was sup-
plied by Utsumi-Recycled-Systems Co. Ltd., Japan, which
*Corresponding author.
a waste management company, while the polyeth-ylene-
glycidyl-methacrylate (E-GMA) impact modifier was
provided by Sumitomo Chemicals Co. Ltd., Japan. Fine
talc (Micro ACE series; diameter is 2.5 and 5.0 µm) was
purchased from Nippon Talc Co., Ltd. and was used as
the filler in RPET.
2.2. Sample Preparation
The sample designations and their corresponding compo-
sitions are shown in Table 1. The ratio of RPET:
E-GMA was set at 84:16, which was compounded with 0,
10, 15 and 20 wt% of talc in a twin screw extruder
(TEX30 HSS, Japan Steel Works Co. Ltd., Japan). The
barrel temperature of the extruder was set at 250˚C -
260˚C while the screw rotation speed was 250 rpm. The
blend pellets were dried by using a dehumidifying drier
at 80˚C for 5 hours prior to being injection molded
(UM50, Po Yuen Co. Ltd., China) into dumbbell speci-
mens at a barrel temperature of 280˚C and injection
speed of 100 mm/s. The dumbbell specimens will be
used for mechanical, morphological and thermal charac-
2.3. Characterization
2.3.1. Static Mechaninal Properties
Tensile tests were performed by using an Instron 4206
universal testing machine in accordance to ASTM D638.
The gauge length was 115 mm and the test was con-
ducted at an extension rate of 50 mm/min. At least 5
specimens were used to ensure repeatability.
2.3.2. Izod Impact Performance
Notched Izod impact strength was determined for speci-
mens notched at 2 mm depth (a/w = 0.2). The specimens
were obtained from the parallel regions of the dumbbell
specimens. The tests were conducted by using a Toyo
Seiki Izod impact tester with a 5.50 J pendulum at 23˚C
in accordance to ASTM D256.
2.3.3. Heat Distortion Temperature
Heat deflection temperature (HDT) of composites was
investigated according to ASTMD648 by using the dual
Table 1. Specimen designation for RPET/E-GMA/talc
blends for ϕ2.5 and 5.0 μm talc powder.
Designation RPET (wt%) E-GMA
(wt%) Talc (wt%)
E16T0 84 16 0
E16T5 79.8 15.2 5
E16T10 75.6 14.4 10
E16T15 71.4 13.6 15
E16T20 67.2 12.8 20
cantilever mode of dynamic mechanical analysis
(DMA2980). The standard stress of 0.45 MPa was con-
stantly applied onto the specimens while temperature was
increased at 2˚C/min from room temperature. The chan-
ges in specimen dimension as a function of temperature
was determined. The heat deflection temperature is de-
fined as the temperature at which the specimen deflects
0.25 mm or 0.2% strain.
3. Results and Discussion
3.1. Tensile Properties
Figures 1 and 2 show the tensile properties of th e RPET/
E-GMA/talc composites at various talc contents. The ten-
sile modulus of the composites steadily increased with
talc content due to the high rigidity of the filler [8], as
could be seen in Figure 1. The tensile strength of the
composites, however, was drastically reduced when 5
wt% of talc was present in the system, as shown in Fig-
ure 2. However with increasing talc content, the tensile
strength of the composites was regained, especially when
a smaller talc particle size was used.
3.2. Impact Properties
Figure 3 shows the impact strength of the RPET/E-
GMA/talc composites at various talc contents. With the
Tensile Modulus /GPa
Talc Content /wt%
5.0 m
2.5 m
Figure 1. Effect of talc content on tensile modulus of RPET/
E-GMA/talc blends.
Tensile Strength /MPa
Talc Content /wt%
5.0 m
2.5 m
Figure 2. Effect of talc content on tensile strength of RPET/
E-GMA/talc blends.
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Impact Strength /kJ m
Talc Content /wt%
5.0 m
2.5 m
Figure 3. Izod impact strength as a function of talc content
wt% for RPET/E-GMA blends.
presence of talc, the notched impact strength of the com-
posites drastically decreased, while similar impact per-
formance was recorded irrespective of subsequent in-
crements in talc content. The absence of a gradual dete-
rioration in toughness during impact loading could be
attributed to the notch sensitivity of RPET as well as the
presence of micro-voids as a result of incompatibility
between the matrix and talc, which acted as stress-con-
centration regions. Nevertheless, the notched Izod impact
strength of the composites were still two times higher
than that of monotonic RPET, which is attributed to the
more complex crack propagation path with the presence
of talc. It should also be noted that the impact properties
were not affected by talc particle size, which indicates
that talc is an effective stress concentrator. All un-
notched specimens did not fracture upon impact, thus the
results were not included in the discussion.
3.3. Dynamic Mechanical Properties
Figures 4 and 5 show the dynamic mechanical properties
of the RPET/E-GMA/talc composites. A gradual but sig-
nificant increment in storage modulus could be observed
with the increment of talc content in RPET, which is in
good agreement with tensile and flexural test results.
With increasing temperature, the storage modulus of the
composites would gradually deteriorate until around
70˚C where a sudden loss in modulus would occur,
which indicates the onset of glass transition temperature.
The decreasing tanδ peak height in Figure 5 as a func-
tion of talc content correspond s to the reduced molecular
chain mobility in RPET. The usage of smaller talc parti-
cles would also result in lower Tanδ peak intensities,
which indicate less molecular movement and higher ri-
gidity of the composites.
3.4. Heat Deflection Temperature
The heat deflection temperature (HDT) test is a popular
industry standard, especially during the designing of
products, which can be used as a simple comparison of
Storage Modulus /MPa
Temperature /°C
5.0 µm
2.5 µm
20 wt%
15 wt%
10 wt%
0 wt%
20 wt%
15 wt%
10 wt%
Figure 4. Storage modulus of RPET/E-GMA/talc blends.
Temperature /°C
2.5 µm
5.0 µm
0 wt%
10 wt%
15 wt%
20 wt%
10 wt%
15 wt%
20 wt%
Figure 5. Tanδ of RPET/E-GMA/talc blends.
the thermal flexural stability of materials [9]. The incor-
poration of talc improved the heat deflection temperature
(HDT) of the blends, as shown in Figure 6. HDT of the
composites was increased by 38% to 85˚C with the in-
corporation of 20 wt% talc with a particle size of 5.0 µm.
This result suggests that the presence of talc would im-
prove the dimensional stability of the composites by im-
parting resistance to molecular movement as well as in-
ducing crystallization of RPET. The improvement in
HDT would be even more pronounced when smaller (2.5
µm) talc particles were incorporated into the composites.
It is thought that this material could be used for the pro-
duction of kitchenware such as trays, bowls or plates,
which are required to withstand temperatures of up to
80˚C such as during dish washing or sterilization. The
higher HDT would also indicate that the material re-
quires less cooling time during molding, hence reducing
the cycle time during injection molding.
From above results, we indicated that talc played an
important role in enhancing the crystallization and heat
resistance of RPET blends. However, the amount of
E-GMA was fixed at the ratio of RPET/E-GMA = 84/16,
and it is considered this percentage of E-GMA is excess
as general injection moldings products. Therefore, we
tried to investigate the mechanical and th ermal properties
for the lower content and smaller size of talc filler as
shown in Table 2.
Figure 7 shows the results of Izod impact test for
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Table 2. Specimen designation for RPET/E-GMA/talc/PBT
blends for ϕ2.5 μm talc powder.
Designation R-PET
(wt%) EGMA
(wt%) Talc
(wt%) PBT
E3T0 97 3 0 0
E3T5 92.1 2.9 5 0
E3T10 87.3 2.7 10 0
E3T15 82.5 2.5 15 0
E3T20 77.6 2.4 20 0
PBT5 92.1 2.9 0 5
PBT10 87.3 2.7 0 10
PBT15 82.5 2.5 0 15
PBT20 77.6 2.4 0 20
Talc Content /wt%
5.0 m
2.5 m
Figure 6. HDT properties for talc contents (wt%) on RPET/
E-GMA blends.
Figure 7. Izod impact strength for PBT or talc contents
(wt%) on RPET/E-GMA(3 wt%) blends.
RPET/E-GMA/PBT and RPET/E-GMA/talc blends. In
the case of RPET/E-GMA/PBT as shown in Figure 7,
impact strength indicated about 40 kJ/m2 and it was the
constant value for each PBT content. On the other hand,
in the case of RPET/E-GMA/talc blends as shown in
Figure 7, impact strength was about 40 kJ/m2 at 0 and 5
wt% content of talc. However, impact strength was dras-
tically changed over 10 wt%, it was about 2 to 5 kJ/m2.
This tendency was similar to the high E-GMA content
results, that is, the results of Figure 3. PBT is engineer-
ing plastics and polyester, thereby, it is considered to
indicate the good co mpatibility between PET and PBT as
compared with other engineering plastics. Consequently,
PBT inhibit the crystallization of PET due to protect to
grow up the nucleation of lamella body. As a result, im-
pact strength of RPET/E-GMA/PBT blends had kept the
high value with increasing the PBT content. In the case
of talc blends, it is considered that crystallization is in-
creased with increasing the content of talc. However, the
impact strength indicated the lower value at high content
of talc, because crack or delamination is formed readily
between RPET and talc filler.
Therefore, DSC measurement was performed for
RPET/E-GMA/talc blends. Figure 8 shows the result of
DSC curves of RPET/E-GMA/talc blends. For RPET/E-
GMA blends, cold-crystallization peak and melting peak
were observed at 120˚C and 250˚C, respectively. How-
ever, cold-crystallization peak was decreased with in-
creasing the content of talc and the pe ak was almost nev-
er observed at 20 wt% talc content.
Figure 9 shows the results of HDT measurement for
RPET/E-GMA/PBT and RPET/E-GMA/talc blends. As
shown in Figure 9, HDT value of PBT blends was al-
most constant at 75˚C, on the contrary, HDT value was
slightly decreased with increasing the PBT content.
Therefore, it is considered that PBT component prevent
PET from crystallizing. On the other hand, HDT value
for RPET/E-GMA/talc blends was increased with in-
creasing the talc content. Finally, the HDT value indi-
cated about 170˚C at 20 wt% talc content. This result will
be supported by the DSC result in Figure 8. It is con-
cluded that talc plays an important role in enhancing the
crystallization and heat resistance of RPET blends and
E-GMA worked so well to improve the toughness of
RPET blends by optimizing the additive amount for
RPET blen d s .
4. Conclusion
In this investigation, we tried to elucidate the effect of
talc filler and polymer blends for RPET injection mold-
ings. The heat deflection temperature and rigidity of
RPET can be significantly enhanced with the incorpora-
tion of talc. The effects would be more pronounced if the
talc particle size was smaller. However, the talc particles
would cause a significant reduction in notched impact re-
sistance, thus low talc content is recommended for the
commodity composites in order to attain a balance in
terms of toughness and dimensional stability. Therefore,
it was found that talc played an important role in en-
hancing the heat resistance of RPET.
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Figure 9. HDT properties for PBT or talc contents (wt%)
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5. Acknowledgements
This work was partly supported by Japan Science and
Technology Agency (JST), A-STEP feasibility study pro-
gram (#AS242Z01291K). We would like to express our
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