Poly(lactic acid)/coplasticized thermoplastic starch blend: Effect of plasticizer migration on rheological and mechanical properties

Abstract

Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio‐based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic immiscibility, which may restrict its usage in packaging applications. Subsequently, our approach in this research is compatibilization of PLA/TPS blends by utilization of primary well tuning of TPS formulation with a combination of sorbitol and glycerol plasticizers. In this work, the wide composition range of melt mixed PLA/TPS blends was prepared using a laboratory twin screw extruder. The effects of microstructure on the rheological and mechanical properties of PLA/TPS blends were studied using different methods such as scanning electron microscopy (SEM) images, contact angle, oscillatory shear rheological measurements, and tensile and impact strength mechanical tests. The rheological and mechanical properties were interpreted according to the morphological features and considering the possibility of plasticizer migration from TPS to PLA phase during melt blending. Reduction in complex viscosity and storage modulus of PLA matrix samples indicates the improved melt processability of blends. Finally, in comparison with mechanical results reported in literature, our simple approach yielded the blends with elastic modulus and ductility comparable with those of chemically compatibilized PLA/TPS blends.

Graphene Derivatives in Biopolymer-Based Composites for Food Packaging Applications

“…However, PLA also has several shortcomings such as poor heat resistance, brittleness, poor melting strength, low degradation rate, and a narrow processing window [ 138 , 139 , 140 ]. To overcome these drawbacks, PLA-based products are being designed not only using PLA but also by mixing it with other biodegradable (bio)polymers and non-biodegradable resins and/or by compounding PLA with fillers such as fibers or micro- and nanoparticles [ 141 , 142 , 143 ]. Currently, PLA is being used in packaging applications as films, as thermoformed blow-molded containers and as short shelf life bottles [ 139 , 140 , 142 , 143 ].…”

Sustainable polymer reaction engineering: Are we there yet?

“…[34] As plasticizers are not covalently bonded to the polymer matrix, they may migrate and eventually lead to contamination of the environment. [35,36] Therefore, it is essential to seek alternatives when applicable. [37,38] Epoxidized vegetable oils and their derivatives have been considered as more environmental friendly plasticizers to replace phthalate esters that are typically used in poly(vinyl chloride).…”

Effect of acrylonitrile content of acrylonitrile butadiene rubber on mechanical and thermal properties of dynamically vulcanized poly(lactic acid) blends

“…Furthermore, the tensile, flexural and impact properties of the PLA/ACR blends strongly depended on the soft/hard ratio of ACR . Thermoplastic starch (TPS) plasticized by glycerol/sorbitol mixtures increased the elongation at break of PLA about 100% compared with neat PLA; however, the PLA/TPS blends showed reduced impact strength by about 30% which was attributed to a weak inherent strength of the TPS phase and a poorly bonded interfacial area . An addition of elastomer is also an interesting technique to increase the toughness of thermoplastics.…”