Enhanced ductility of polylactide materials: Reactive blending with pre-hot sheared natural rubber

Both polylactide (PLA) and natural rubber (NR) are biocompatible and biodegradable. PLA performs high strength and modulus but low toughness, while NR exhibits excellent elasticity and ductility. In view of their complementary properties, NR seems an ideal candidate to toughen PLA. To the best of our knowledge, PLA and rubber blends usually show notable enhancement in ductility when more than 10 % rubber was added, but accompanied by great loss in mechanical strength. This study demonstrates a significant improvement in the toughness of PLA by its melt blending with pre-hot sheared natural rubber (NR). With as little as 3 % pre-hot sheared NR for 10 min, the elongation at break and tensile toughness were significantly improved over that of pure PLA (196.2 % vs. 16.3 % and 77.5 MJ/m3 vs. 8.8 MJ/m3, respectively) with a slight loss in tensile stress. FTIR spectra indicated that carbonyl groups generated in NR chains after hot shearing and led to the enhanced interfacial adhesion between PLA and NR. The SEM studies showed that the rubber phase was uniformly dispersed in PLA matrix in NR/PLA blends with 3 % rubber content. The addition of NR after hot shearing for 10 min reduced the glass transition temperature of PLA, which was characterized by DSC measurement. Rheological measurements also proved a better compatibility of the blend with pre-hot shearing of NR for a longer time.