Mechanical properties, morphology and molecular characteristics of poly(ethylene terephthalate) toughened by natural rubber

The melt blending of poly(ethylene terephthalate) (PET) and natural rubber (NR) in a twin-screw extruder is studied. Parameters affecting the blend properties such as the amounts of the NR in the blends and screw speeds are investigated. Increased toughness of the PET/NR blend was found as the amount of NR was increased. The impact strength of the PET/NR (80/20 wt%) blend using a screw speed of 100 rpm, increased up to seven-fold when compared to that of pure PET. The morphology of the blend was investigated by SEM. The molecular characteristic was evaluated by spectroscopic technique. The toughening effect of NR on the PET might come from the possible interaction between the two phases, which was clearly evidenced by solid-state CP/MAS 13C NMR data. The data revealed an increase in the cross polarization time (TD) of the carbonyl carbon and a decrease of the T1ρH relaxation of the carbonyl groups in the PET/NR blend. This should come from the interaction between the carbonyl group of PET with some abnormal groups such as hydroxyl function in the NR, resulting in an improvement of the compatibility of the studied blends.