Influence of poly(butylene terephthalate) and wollastonite on properties of recycled poly(ethylene terephthalate) preforms

Influence of poly(butylene terephthalate) (PBT) and wollastonite (WLN) on properties of recycled poly(ethylene terephthalate) (RPET) was investigated. RPET was first melt-mixed with PBT at five loadings (10-50 wt%) on a twin screw extruder, and then injection molded. Scanning electron micrographs showed the immiscible blends. The blends at 10-40 wt% PBT displayed droplet-matrix morphology, while the blend at 50 wt% PBT showed a matrix inversion. All blends showed a PBT-dose-dependent increase in impact strength and Young's modulus with an expense of tensile strength and elongation at break. Among five RPET/PBT blends, the one at 40 wt% PBT exhibited the good balanced mechanical properties in terms of toughness and stiffness, which was subsequently filled with four loadings of WLN (10-40 wt%). The addition of WLN showed a noticeable increase in the impact strength and Young's modulus, especially at 30 wt% WLN, and a slight reduction in the tensile strength and elongation at break. The composite at 30 wt% WLN exhibited a better dispersion of WLN in polymer matrix and wettability between polymers and WLN, leading to the higher mechanical properties. Differential scanning calorimetry revealed the miscibility of RPET and PBT in amorphous region and the immiscibility in crystalline phase.