Rotational Moulding of Poly-lactic Acid; effect of plasticization and degree of crystallinity

This work is aimed to study the suitability of polylactic acid (PLA) plasticized by two cardanol derivatives, i.e. cardanol (CA) and epoxidized cardanol acetate (ECA), in two different processing techniques, i.e. injection molding and rotational molding. Plasticized PLA samples were obtained by melt mixing. For comparison purposes, poly(ethylene glycole), PEG plasticized PLA was also produced. Initially, the crystallization kinetics of plasticized were studied, highlighting the effect of PEG in increasing the rate of crystallization during cooling. Then, plasticized PLA were processed by the two different techniques, which are characterized by significantly different cooling rates: very fast for injection molding, and very low for rotational molding. For injection molded samples, the cooling rate is much higher than the critical quenching rate, which allows to obtain almost completely amorphous samples at 10 phr of plasticizer. On the other hand, in rotational molding, for PEG, the cooling rate is much lower than the critical quenching rate, which leads to the production of almost completely crystalline samples, showing a very brittle behaviour. The lower critical quenching rate of CA and ECA allowed to produce almost completely amorphous samples also by rotational molding, thus allowing to retain very good toughness of the produced samples.