Reactive toughening of injection-molded polylactide pieces using maleinized hemp seed oil

Abstract

The present study describes the effect of maleinized hemp seed oil (MHO) on the physical performance of polylactide (PLA) pieces. To this end, PLA pieces with varying MHO contents in the 0-10 wt% range were manufactured by twin-screw extrusion (TSE) followed by injection molding. The resultant pieces were characterized in terms of their mechanical, thermal, and thermomechanical properties. The obtained properties suggested that, unlike typical plasticizers, MHO does not only induce an increment in elongation at break and impact strength but it also enhances both elastic modulus and tensile strength. In addition, it was observed a moderate decrease in the glass transition temperature (Tg). This was ascribed to a linear chain extension and/or branching phenomenon due to the reaction of the multiple maleic anhydride (MAH) groups present in MHO with the hydroxyl groups of the PLA terminal chains. Furthermore, morphology characterization revealed that, though certain phase separation occurred at its highest content, MHO was finely dispersed as submicron droplets within the PLA matrix contributing to improving toughness. The use of multi-functionalized reactive oils thus represents a highly sustainable solution to reduce the intrinsic brittleness of PLA materials without compromising their mechanical resistance and the toughened biopolymer pieces described herein can find interesting applications in, for instance, rigid packaging.

Improved Toughness in Lignin/Natural Fiber Composites Plasticized with Epoxidized and Maleinized Linseed Oils

“…This macromolecular change can be based on the fact that the cold crystallization peak was broader (or even disappeared) as the MLO content increased and the melting peak slightly shifted to lower temperatures. In particular, the T cc of Arboform formulations with 1 wt % and 2.5 wt % MLO moved up to 100.7 • C and 103.8 • C, respectively, while the neat matrix showed a T cc of 97.2 • C. A similar T cc was observed for formulations with 5, 10 and 15 wt % MLO with values of 102-103 • C [43]. This suggests a break of the crystalline structure in the polymeric phase, so the shift in the cold crystallization process can be related to the network formation of PLA molecules of higher molecular weight that inhibits chain motion during packing and rearrangement.…”

Manufacturing and compatibilization of PLA/PBAT binary blends by cottonseed oil-based derivatives

“…Nevertheless, the efficiency of vegetable oil-based plasticizers is very poor as, in general, a very slight decrease on the glass transition temperature is achieved. Nevertheless, the highly reactive groups in modified vegetable oils (mainly epoxy, acrylate, maleic anhydride groups, among others) can react with hydroxyl groups present in the end chains of polyesters thus leading to additional reactions that could lead to chain extension, branching and crosslinking simultaneously as reported by Quiles-Carrillo and coworkers [41][42][43] in several works. With regard to Joncryl ® , typical amounts of 1 wt% are recommended by suppliers to avoid gel formation by crosslinking.…”

On the use of acrylated epoxidized soybean oil as a reactive compatibilizer in injection‐molded compostable pieces consisting of polylactide filled with orange peel flour

“…These multi‐functionalized vegetable oils present the dual advantages of being derived from natural resources and of acting as plasticizers due to their intrinsic lubricant effect on polymer matrices . This is of great interest from an environmental point of view since they allow one to obtain totally ecofriendly and fully bio‐based polymer formulations with improved toughness . In this regard, chemically modified oils, such as maleinized linseed oil or epoxidized soybean oil, have been recently used to increase the filler–matrix compatibility in PLA‐based composites with very promising results.…”