PROCESSING OF POLY(LACTIC ACID) BLOWN FILMS WITH FOOD GRADE CHAIN EXTENDERS FOR PACKAGING APPLICATIONS

摘要

Poly(lactic acid) or PLA films are brittle and difficult to manufacture due to PLA's insufficient melt strength,which are overcome by chain branching with melt strength enhancers (MSEs).Thus,the effectiveness and efficiency of two newly developed and FDA-approved food grades MSEs with different epoxy equivalent weights (low and high) in chain extending PLA were studied first using a torque rheometer.Both multifunctional epoxies chain-extended PLA effectively since they significantly increased the torque during mixing.However,the MSE with lower epoxy equivalent weight was more efficient in chain branching PLA due to its higher reactivity.Secondly,the feasibility of utilizing this most efficient MSE in extrusion-blown PLA film processing was assessed.Chain extension reactions also occurred during film production as confirmed by its increased molecular weight.However,film manufacture was only feasible for blends with up to 0.5% MSE,becoming unprocessable above this content due to the increased viscosity.Chain branching of PLA film was found beneficial in overcoming its brittleness since its impact strength increased almost linearly with the chain extender content.These sustainable ductile films have tremendous potential for food packaging applications.