Recycled poly(ethylene terephthalate)/polypropylene/wollastonite composites using PP-g-MA as compatibilizer: Mechanical, thermal and morphological properties

P Chaiwutthinan, S Suwannachot, A Larpkasemsuk


Polymers investigated in this study were recycled poly(ethylene terephthalate) (rPET) as a major phase (matrix) and virgin polypropylene (PP) as a minor phase (dispersed phase). Initially, rPET was melt mixed with four different PP contents (10–40 wt%) on a co-rotating twin screw extruder and then injection molded. The blend at 30 wt% PP exhibited the highest impact strength and elongation at break and an acceptable tensile strength and Young’s modulus. The 70/30 (w/w) rPET/PP blend was then upgraded its compatibility using 1–7 parts by weight per hundred of blend resin (phr) of maleic anhydride grafted PP (PP-g-MA). Among the compatibilized blends, that with 3 phr PP-g-MA imparted the highest impact strength and elongation at break owing to the better phase interaction. Therefore, the 70/30/3 (w/w/phr) rPET/PP/PP-g-MA compatibilized blend was selected for preparing composites with 5–20 phr of ultrafine wollastonite (WLN) in order to widen its applications. The effects of WLN content on mechanical properties (impact and tensile tests), thermal behaviors (differential scanning calorimetry and heat distortion temperature (HDT)) and morphology (scanning electron microscopy) of the composites were then investigated. The results showed that the tensile strength, Young’s modulus and HDT of the composites were enhanced by up to 1.1-, 1.5- and 1.3-fold, respectively, over those of the neat compatibilized blend in a WLN-dose-dependent manner, whereas the impact strength and elongation at break only decreased slightly. This finding was due to the high aspect ratio, stiffness and thermal resistance of the WLN.

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