No abstract

In this work, poly(lactic acid), PLA and thermoplastic starch, TPS blends (with a fixed 11 content of 30 wt.% TPS) were prepared by melt extrusion process to increase the low ductile 12

Highly sustainable composites were produced by melt compounding polylactide (PLA) with almond shell flour (ASF), a processed byproduct of the food industry, at a weight content of 30 wt.-%. However, due to the lack of miscibility between PLA and ASF, both being raw materials obtained from crops, resultant green composite presented poor ductility and low thermal stability. To overcome this limitation, maleinized linseed oil (MLO), a multi-functionalized plant-derived additive, was originally incorporated as a reactive compatibilizer during the extrusion process. Both chemical and physical characterizations showed that 1-5 parts per hundred resin (phr) of MLO successfully serve to function as a novel compatibilizer on the PLA/ASF composites, leading to highly sustainable materials with balanced mechanical, thermal, and thermomechanical properties. Achieved compatibilization was particularly related to a dual effect of plasticization in combination with grafting. The latter effect was ascribed to the formation of new carboxylic ester bonds through the reaction of the multiple maleic anhydride groups present in MLO with the hydroxyl terminal groups of both PLA chains and lignocellulose on the ASF surface. The fully bio-based and 2 biodegradable composites described herein give an efficient sustainable solution to upgrade agrofood wastes as well as contributing to reducing the cost of PLA-based materials.

This research work aims to study the influence of the reprocessing cycles on the mechanical, thermal, and thermomechanical properties of polylactide (PLA). To this end, PLA was subjected to as many as six extrusion cycles and the resultant pellets were shaped into pieces by injection molding. Mechanical characterization revealed that the PLA pieces presented relatively similar properties up to the third reprocessing cycle, whereas further cycles induced an intense reduction in ductility and toughness. The effect of the reprocessing cycles was also studied by the changes in the melt fluidity, which showed a significant increase after four reprocessing cycles. An increase in the bio-polyester chain mobility was also attained with the number of the reprocessing cycles that subsequently favored an increase in crystallinity of PLA. A visual inspection indicated that PLA developed certain yellowing and the pieces also became less transparent with the increasing number of reprocessing cycles. Therefore, the obtained results showed that PLA suffers a slight degradation after one or two reprocessing cycles whereas performance impairment becomes more evident above the fourth reprocessing cycle. This finding suggests that the mechanical recycling of PLA for up to three cycles of extrusion and subsequent injection molding is technically feasible.

Green composites were prepared with polypropylene matrix and 20 wt.% spent coffee ground (SCG) powder for uses as a wood plastic composite (WPC). The effects of hydrophobic treatment with palmitoyl chloride on SCG powder is compared with conventional surface treatment based on silanization with (3-glycidyloxypropyl) trimethoxysilane and the use of a maleated copolymer compatibilizer (polypropylene-graft-maleic anhydride, PP-g-MA) in terms of mechanical properties, morphology, thermal properties and water uptake. Composites were previously mixed in a twin-screw co-rotating extruder and subsequently subjected to injection moulding. The comparative effect of the different surface treatments and or compatibilizers on mechanical performance was studied by flexural, impact tests and dynamic mechanical thermal analysis (DMTA-torsion); in addition, the stabilizing effect of SCG was revealed by differential scanning calorimetry (DSC) and thermogravymetric analysis (TGA). As one of the main drawbacks of wood plastic composites and natural fiber reinforced plastics is the moisture gain, water uptake tests were carried out in order to quantify the effectiveness of the hydrophobization process with palmitoyl chloride. Results show a slight increase in flexural modulus for composites with both untreated and treated/compatibilized SCG powder (20 wt.%).As expected, thermal stability is improved as indicated by an increase of more than 8% in the