Effect of Extrusion on the Mechanical and Rheological Properties of a Reinforced Poly(Lactic Acid): Reprocessing and Recycling of Biobased Materials

Abstract

The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript.

Structure-properties relationships in melt reprocessed PLA/hydrotalcites nanocomposites

“…However, the replacement of conventional polymers with biodegradable polymers cannot be the only way to reduce the accumulation of plastic materials in landfills. Several papers also investigated the possibility to recycle biodegradable polymers in order to reduce the environmental impact related to the life cycle of biodegradable polymer-based items [5][6][7][8][9][10][11]. Among the different recycling routes, mechanical reprocessing represent an easy and low cost method [12,13].…”

Bio‐based blends from poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and natural rubber for packaging applications

“…The gel from the PHBV and natural rubber blends was obtained by extraction in chloroform at 60 °C for 48 h. The gel fractions ( G f ) were calculated by the following equation: where m 0 is the initial weight of the samples, and m 1 is the weight of the dried residues obtained after extraction …”

“…Also, the high crystallinity of PHBV makes it stiff at temperatures up to its T m but very fluid above its T m , resulting in a very narrow temperature window for processing . The processability of PHBV has been improved by: (1) broadening the processing window by including additives to lower the PHBV T m and/or increase the T p ; (2) decreasing the degree of crystallinity ( X c ) of PHBV by increasing the valerate content or incorporation of elastomers, nanofillers, or other thermoplastics which can decrease the nucleation density of PHBV; (3) improving the melt strength of PHBV by introducing long‐chain branched structures or melt strength enhancers, such as acrylic copolymer and silicate nanoclays; and (4) improving the thermal stability of PHBV by incorporating polymer which can efficiently dissipate the heat to minimize its thermal degradation during the manufacturing process . For example, PHBV blended with dynamically crosslinked PBS had increased viscosity and improved processability …”

Three-dimensional printing of PLA and PLA/PHA dumbbell-shaped specimens of crisscross and transverse patterns as promising materials in emerging application areas: Prediction study

“…6) of the specimens from the beginning of the experiment for both ageing temperatures (50 ºC and 70 ºC). The progress of degradation greatly increased at temperatures above the glass transition of PLA, therefore, the degradation progress at 50 ºC was slower [20][21][22][23][24][25][26][27][28][29][30][31]. There are no significant differences in mass loss between specimens degraded at 70 ºC, however, the specimens printed in vertical direction showed higher values of mass loss as a result of weaker cohesion between layers and faster disintegration of the specimens.…”

“…Mixing time, temperature and drying also influence the degradation of PLA-based materials. [25,26] That is why it is so important to determine the effect of processing conditions on polymer properties and course of hydrolytic degradation.…”