The Influence of Peroxide on Bubble Stability and Rheological Properties of Biobased Poly(lactic acid)/Natural Rubber Blown Films

This study investigated the effects of natural rubber (NR) and an organic peroxide on the rheological properties, mechanical properties, morphology, and bubble stability during film blowing of poly(lactic acid) (PLA). The NR and peroxide contents were varied from 0 wt% to 25 wt% and 0 wt% to 0.5 wt%, respectively. The results confirmed that the presence of well-dispersed NR could significantly improve the toughness, elongation at break, and processability of PLA films, where the optimal amount of NR was 15 wt%. For the reactive blending with peroxide, a suitable peroxide content for good film toughness and clarity was 0.03 wt%, while the higher content of 0.1 wt% could provide slightly higher processability. These contents are considered much lower than that in the PLA system (without NR), which required up to 0.5 wt% peroxide. The rheological studies indicated that the melt strength, the storage modulus (G ') and complex viscosity (eta ') at low frequency could be correlated with good film blowing processability of the PLA/NR films at low gel contents. These parameters failed to correlate in the films having high gel contents as the deformation rate experienced by each test was different leading to the different levels of response to the type and amount of gels.