Thermal properties of extruded and injection‐molded poly(lactic acid)‐based cuphea and lesquerella bio‐composites

Abstract

The degree of compatibility between poly (lactic acid) (PLA) and different bio-fillers was examined using thermal methods. The biofillers were fibers extracted from cuphea and lesquerella seeds. Bio-composites of PLA:Fiber were prepared at 85 : 15, 70 : 30, and 100 : 00 and blended by extrusion and then injection molding. Thermal properties of the extruded (EX) and the extrudedinjection molded (EXIM) composites were examined using differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). Composites analysis using DSC provided information essential for determining: (1) glass transition (T g ); (2) crystallization and melting temperatures and DH; (3) percent crystallinity; and (4) Enthalpic Relaxation (ER). TGA was used to measure the mechanism of the thermal decomposition of the composites. The effect of fiber composition, processing conditions, and aging time on the thermal properties of the bio-composites was used to examine the relative compatibility of the fibers with PLA. The data showed that ER increased steadily as a function of aging. Because of the difference in protein content between cuphea and lesquerella, the two fibers influenced the T g (temperature and DC p ) differently. The percent crystallinity of neat PLA was significantly reduced by EX or EXIM, while the enzymatic degradation showed that EX composites are more biodegradable than EXIM. The TGA profiles indicated a multi-step degradation especially in air. The largest value of q, which indicated that, intermolecular interaction was strongest between lesquerella and PLA extruded materials, compared to the other three blends, possibly due to the higher protein content. Results also indicated that intermolecular interaction was least strong (q ¼ À33.9156) in the EXIM PLA-cuphea. Although the q values of both cuphea composites were significantly lower than those of the lesquerella samples, this greater effect of extrusion over injection molding on intermolecular interaction was also seen in the q value of the EX and EXIM samples.

Use of Nutshells as Fillers in Polymer Composites

“…Thermal properties of samples were evaluated by differential scanning calorimetry (DSC) performed on DSC7 [15][16][17][18][19][20] Cellulose fibers [21][22][23] Cellulose whiskers [24] Microcrystalline cellulose [21,25] Wood flour and fibers [21,26,27] Flax fibers [23,28,29] Hemp fibers [30,31] Kenaf fibers [32,33] Bamboo fibers [34] Jute [21,35] Corn husks and stover [36,37] Apple solids and fibers [38,39] Sugar beet pulp [38,40] Oat husks [39] Cocoa shells [39] Wheat straw [37] Soy stalks [37] Abaca leaves [41] Green coconut [42] Cuphea and lasquerella seeds [43] Cotton burr and hull [44] Polyethylene Starch [45][46][47][48][49][50][51][52]…”

Desenvolvimento de biocompósitos de poli(L-ácido láctico) (PLLA) com serragem de madeira

“…Diferentes estratégias têm sido desenvolvidas para alterar as propriedades mecânicas de PLLA, dentre elas a proposição de diferentes compósitos aplicando fibras naturais ou artificiais, tais como cânhamo, linho, kenaf, fibra de vidro e fibra de carbono para reforço PLLA [19]. Dentre alguns exemplos de aplicações de fibras naturais em biocompósitos de matriz PLLA com sementes de Cuphea e lasquerella visando desenvolver compósitos poliméricos verdes com propriedades mecânicas adequadas para materiais de construção leves ou painéis interiores automotivos [20]. A utilização de fibras de cânhamo em PLLA aumentou a resistência à tração e ao impacto e o módulo de flexão devido à boa compatibilidade entre as fibras de cânhamo e o PLLA [21].…”

Banana/sisal fibers reinforced poly(lactic acid) hybrid biocomposites; influence of chemical modification of BSF towards thermal properties

“…This clearly indicates the superior compatibility and effective dispersion of BSF throughout PLA matrix as a consequence of IM process. This could be one of the possible reasons why an improved thermal stability was imparted by BP‐T‐BSF/PLA composites than virgin PLA and UT‐BSF/PLA composites .…”

“…The virgin PLA and BP-T-BSF/PLA biocomposite test specimens were fabricated by IM with the same procedure adopted for UT-BSF/PLA composites. The test specimens were subjected to annealing at a temperature of 80 8C in an oven as long as 24 h [3,[9][10][11][12].…”

“…As a result, PLA has been chosen as matrix material and BSF as reinforcing material for our recent study to fabricate hybrid biocomposites, which can offer improved properties that are required for various engineering applications [6][7][8][9][10][11]. Moreover, the hybridization of BSF with PLA can be done by extrusion process in a twin-screw extruder and the extruded composites were further injection molded to test specimens [8][9][10][11][12]. Furthermore, the intention of this research is to study the thermal properties of virgin PLA, UT-BSF/PLA, and BP-T-BSF/PLA biocomposites by means of Fourier transformed infrared (FTIR) spectra, DSC, and TGA characterization techniques.…”