PLA/PCL/NR ternary blown films with high ductility and thermal shrinkage performance via dynamic vulcanization.

The low melt strength and brittleness of polylactic acid (PLA) significantly limit its application in high-performance and functional films. In this study, we successfully prepared ternary thermoplastic vulcanizates (TPVs) comprising of PLA, poly(caprolactone) (PCL) and natural rubber (NR), which exhibit co-continuous structure. During the peroxide-induced dynamic vulcanization process, PLA chains were effectively grafted and anchored to the cross-linked rubber network, thereby enhancing the melt strength of the material. This improvement allowed the ternary TPVs to be continuously and stably blown into films. The films exhibited excellent mechanical properties due to the synergistic effect of ductile PCL and elastic NR. Both the elongation at break and tear strength improved greatly. Interestingly, during the film blowing process, the highly stretched continuous NR crosslinked network stored large amounts of elastic energy, endowing the film with excellent heat shrinkage performance. With 15 phr NR, the heat shrinkage exceeded 35 %, which is sufficient for practical needs. This biodegradable film with heat-shrinkage properties can be processed on a large scale, offering a potential strategy to the urgent issue of plastic film pollution.