Effectiveness of Talc Filler on Thermal Resistance of Recycled PET Blends

doi:10.4236/ampc.2013.38045

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Advances in Materials Physics and Chemistry, 2013, 3, 327-331

Published Online December 2013 (http://www.scirp.org/journal/ampc)

http://dx.doi.org/10.4236/ampc.2013.38045

Open Access AMPC

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: *[email protected]

Received October 27, 2013; revised November 28, 2013; accepted December 12, 2013

Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is

as a guardian.

ABSTRACT

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-

dated.

2. Experimental

2.1. Materials

Recycled poly (ethylene terephthalate) (RPET) was sup-

plied by Utsumi-Recycled-Systems Co. Ltd., Japan, which

*Corresponding author.

K. YAMADA, S. THUMSORN

328

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-

terizations.

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.

Specimen

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

2.4

2.0

1.6

1.2

Tensile Modulus /GPa

20151050

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

20151050

Talc Content /wt%

5.0 m

2.5 m

Figure 2. Effect of talc content on tensile strength of RPET/

E-GMA/talc blends.

Open Access AMPC

K. YAMADA, S. THUMSORN 329

Impact Strength /kJ m

-2

20151050

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

120100806040

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.

Tan

120100806040

Temperature /°C

2.5 µm

5.0 µm

0 wt%

10 wt%

15 wt%

20 wt%

10 wt%

15 wt%

20 wt%

Tanδ

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

Open Access AMPC

K. YAMADA, S. THUMSORN

330

Table 2. Specimen designation for RPET/E-GMA/talc/PBT

blends for ϕ2.5 μm talc powder.

Specimen

Designation R-PET

(wt%) EGMA

(wt%) Talc

(wt%) PBT

(wt%)

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

100

HDT /°C

20151050

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.

Open Access AMPC

K. YAMADA, S. THUMSORN

Open Access AMPC

331

[2] S. Thumsorn, K. Yamada, Y. W. Leong and H. Hamada,

“Thermal Decomposition Kinetic and Flame Retardancy

of CaCO3 Filled Recycled Polyethylene Terephtha-

late/Recycled Polypropylene Blend,” Journal of Applied

Polymer Science, Vol. 127, 2013, pp. 1245-1256.

http://dx.doi.org/10.1002/app.37673

Endothermic Heat Flow

30025020015010050

Temperature [°C]

RPET/E-GMA

Talc 5 wt%

Talc 10 wt%

Talc 15 wt%

Talc 20 wt%

[3] M. Ogasahara, M. Shidou, S. Nagata, K. Yamada, Y. W.

Leong and H. Hamada, “Effectiveness of High Frequency

Heating on Drying and Intrinsic Viscosity Enhancement

of Recycled Poly (Ethylene Terephthalate),” Journal of

Applied Polymer Science, Vol. 126, 2012, pp. E166-E171.

http://dx.doi.org/10.1002/app.34368

[4] S. Thumsorn, K. Yamada, Y. W. Leong and H. Hamada,

“Effect of Pellet Size and Compatibilization on Thermal

Decomposition Kinetic of Recycled Polyethylene Ter-

ephthalate/Recycled Polypropylene Blend,” Journal of

Applied Polymer Science, Vol. 124, 2012, pp. 1605-1613.

http://dx.doi.org/10.1002/app.35166

Figure 8. DSC curves of RPET/E-GMA/talc blends at vari-

ous talc content.

[5] S. Thumsorn, K. Yamada, Y. W. Leong and H. Hamada,

“Development of Cockleshell-Derived CaCO3 for Flame

Retardancy of Recycled PET/Recycled PP Blend,” Mate-

rials Sciences and Applications, Vol. 2, 2011, pp. 59-69.

http://dx.doi.org/10.4236/msa.2011.22009

[6] N. Kunimune, K. Yamada, Y. W. Leong, S. Thumsorn

and H. Hamada, “Influence of the Reactive Processing of

Recycled Poly(Ethylene Terephthalate)/Poly (Ethylene-

Coglycidyl Methacrylate) Blends,” Journal of Applied

Polymer Science, Vol. 120, 2011, pp. 50-55.

http://dx.doi.org/10.1002/app.32836

[7] R. Konishi, K. Miyata, K. Yamada, Y. W. Leong, Y.

Hashimoto and H. Hamada, “Interface of Draw Ratio on

Adhesion of Heat-sealed Recycled-PET Films,” Journal

of Packaging Science and Technology, Vol. 20, No. 2,

2011, pp.107-115.

Figure 9. HDT properties for PBT or talc contents (wt%)

on RPET/E-GMA(3 wt%) blends.

[8] Y. Yand, C. G’Sell, J. Hiver and S. Bai, “Dynamic Me-

chanical Properties and Morphology of High-Density

Polyethylene/CaCO3 Blends with and without an Impact

Modifier,” Journal of Applied Polymer Science, Vol. 103,

2007, pp. 3907-3914.

http://dx.doi.org/10.1002/app.25619

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

profound gratitude to them. [9] B. Alcock, N. O. Cabrera, N.-M. Barkoula, C. T. Rey-

nolds, L. E. Govaert and T. Peijs, “The Effect of Tempe-

rature and Strain Rate on the Mechanical Properties of

Highly Oriented Polypropylene Tapes and All-Polypropy-

lene Composites,” Composites Science and Technology,

Vol. 67, 2007, pp. 2061-2070.

http://dx.doi.org/10.1016/j.compscitech.2006.11.012

REFERENCES

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PET Bottle Resin Polymer in Japan,” 2009.

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