Advance on processing of compostable and thermally stable biodegradable polyester blends

Abstract

Flexible and semiflexible packagings can be manufactured by cast extrusion of plastic sheet and thermoforming of containers. Thermal stability is often required as packaging items after being thermoformed can come in contact with hot food/beverage, especially during hot filling operations. In this framework, the present study deals with the design and manufacturing by thermoforming of plastic containers that are, at the same time, compostable and suitable for high‐temperature applications (~100 °C). First, extrusion compounding of Poly(l‐lactic acid) (PLLA)‐based biodegradable polyester blends was performed. In particular, the effect on the material properties of different types of nucleating agents was investigated. Combinations of micro‐lamellar talc, poly(d‐lactic acid) (PDLA), ethylene bisstearamide (EBS), and titanium dioxide (TiO2) were studied. The formulations involving EBS boast the highest crystallinity and the fastest onset of the crystalline phase on sheets produced by cast extrusion. Conversely, the formulations involving TiO2 feature the lowest degree of crystallinity and the slowest onset of the crystalline phase. Combinations of talc and PDLA exhibit an intermediate behavior. Second, thermoforming of the plastic foils was performed. A very different trend of the crystallization after thermoforming is shown. Indeed, crystallinity is the highest for the formulations involving talc and PDLA, the lowest for the ones containing EBS. In conclusion, the biodegradable polyester blends are found to be suitable for the manufacturing of compostable and thermostable packaging items by cast extrusion and thermoforming. Final crystallization of the material and the resulting thermal stability can be fine‐tuned by modulating type and amount of nucleating agents. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48722.

Optimizing crystallinity of engineered poly(lactic acid)/poly(butylene succinate) blends: The role of single and multiple nucleating agents

“…The present study extends a previous application work 84 and is aimed to evaluate binary PLA/PBS blend in cast extrusion and thermoforming of films. The addition of PBS, which retains partial miscibility with PLA and high elongation at break, 85 aims to increase the ductility of the composite to stem the high fragility of PLA, without substantially affecting the strength and modulus of the PLA matrix itself.…”

Blown film extrusion of poly(lactic)acid/poly(3‐hydroxybutyrate‐4‐hydroxybutyrate) blends for improved toughness and processability

“…From the literature it is known that EBS has a lubricating effect on the polymeric chains that may favor higher elongation at break. [ 38 ]…”

“…From the literature it is known that EBS has a lubricating effect on the polymeric chains that may favor higher elongation at break. [38] Standard deviation of the tensile test is rather high despite 10 samples were considered for each formulation. Blown films feature a smooth surface and are apparently free from defects, however results suggest microdefects are present in the film which cause high variability of results.…”

Mechanical recycling of PLA: Effect of weathering, extrusion cycles, and chain extender

“…One of the most popular chain extenders is Joncryl ADR-4368, which has been recently used for PLA. [14][15][16] Joncryl ADR-4368 has several epoxy groups which can react with the hydroxyl or carboxyl groups of the degraded chains of different polymers, making it a multifunctional molecule able to produce linear chain extension, branching, or cross-linking. 17 Figure 1 shows the reaction mechanism between PLA and Joncryl ADR proposed by Tuna and Ozkoc, consisting of a ring opening of the epoxy group and its reaction by covalent bonds with the hydroxyl group of PLA.…”

“…Chain extenders are an alternative to overcome molecular weight loss caused by reprocessing or weathering. One of the most popular chain extenders is Joncryl ADR‐4368, which has been recently used for PLA 14–16 . Joncryl ADR‐4368 has several epoxy groups which can react with the hydroxyl or carboxyl groups of the degraded chains of different polymers, making it a multifunctional molecule able to produce linear chain extension, branching, or cross‐linking 17 .…”