In situ fibre-reinforced composite films of poly(lactic acid)/low-density polyethylene blends: effects of composition on morphology, transport and mechanical properties

摘要

This study aimed to investigate the effects of blend composition on packaging-related properties of poly(lactic acid) (PLA) and low density polyethylene (LDPE) blown films. Blend films with PLA contents of 5-20 wt% were produced and compared. Scanning electron micrographs of cross-sectional cryofractured surfaces of the blend films revealed that in situ fibre-reinforced composites were obtained. Viscosity ratio of the polymer components of ca 1 confirmed that fibre formation was favourable for this blend system. PLA microdomains were dispersed throughout the film in forms of long fibres (length-to-diameter ratio > 100) and ribbons. The number of fibres and ribbons increased with an increase of PLA content. Critical content of PLA was found to be 20 wt% for effective improvement of both moduli and gas barrier properties. Incorporation of poly[ethylene-co-(methyl acrylate)] compatibilizer showed minimal effect on PLA structure. However, it did improve moduli and O-2 barrier properties when sufficient amount (1.5 pph) was used in 10 wt% PLA/LDPE. In short, flow behaviour, ratio of polymer components and degree of compatibility together played intricate roles in the morphology and hence mechanical and transport properties of PLA/LDPE immiscible blends. (C) 2017 Society of Chemical Industry