Effect of different thermal treatments on the mechanical performance of poly(L‐lactic acid) based eco‐composites

Abstract

PLLA-based eco-composites reinforced with kenaf fiber and rice straw and containing red or yellow pigments have been studied. The mechanical behavior of the composites was tested by DMTA at two different annealing temperatures (65 C and 85 C) and times (15 min and 120 min) as well as at two preparation conditions: vacuum drying and long time at room temperature. A decrease of microhardness was observed during the water absorption tests. Moreover, the rice straw-based composites absorbed more water than the kenaf-ones. Generally, the dyed NFs composites presented better water resistance than undyed ones. The pigments improved the adhesion and led to better mechanical performance. The natural fibers favored the cold crystallization process of PLLA and shifted the cold crystallization peak temperature to lower values, as it was confirmed by DSC measurements. The values of tensile storage modulus obtained after different preparation condition were strongly affected by the process of physical ageing. According to, tan d parameter, the samples stored at room temperature for a long time showed the highest amorphous content. The PLLA eco-composite reinforced with kenaf fibers, dyed with the red pigment, and annealed at 85 C for 2 h displays the best mechanical properties.

Effect of Thermal Processing on the Dynamic/Isothermal Crystallization and Cytocompatibility of Polylactic Acid for Biomedical Applications

“…It is known that poly-lactides (PLA) have a low crystallization rate, and many efforts have been spent in order to enhance PLA´s crystallization rate with nucleating agents. [12] The effect of processing on crystallization kinetics should not be ignored, considering that the PLA is sensitive to processing conditions. The reduction of PLA molecular weight takes place due to the thermomechanical history that the polymer undergoes during processing and can affect the crystallization kinetics.…”

Does magnesium compromise the high temperature processability of novel biodegradable and bioresorbables PLLA/Mg composites?

“…5, Table 3). This behaviour contrasts with the important nucleation effect of different fillers in the crystallization of PLLA (Pinho et al, 2009;Papageorgiou et al, 2010;Dobreva et al, 2010a;Dobreva et al, 2010b). Heating from the amorphous condition (CR10F10 - Fig.…”

Investigation on Polylactide (PLA)/Poly(butylene adipate-co-terephthalate) (PBAT)/Bark Flour of Plane Tree (PF) Eco-Composites

“…Figure 7 illustrates wide angle X-ray diffraction (WAXD) patterns of the isothermally crystallized samples. The diffraction peaks at 2θ = 16.7° and 19.3° correspond to (110)/(200) and (203) planes of PLA, respectively, which belong to the orthorhombic α crystal form of PLA [ 4 , 17 , 23 , 33 , 39 ]. Only two distinctive peaks of α-PLA are observed for PLA/PF, PLA/T-PF and PLA/PBAT/T-PF composites.…”

“…In the case of the eco-composites, various kinds of natural fibers such as kenaf fiber [ 17 , 18 ], sisal fiber [ 19 ], jute fiber [ 20 ], flax fiber [ 21 , 22 ], hemp fiber [ 23 , 24 ], phormium tenax fiber [ 25 ], pineapple leaf fiber [ 26 ], banana fiber [ 27 ], coconut fiber [ 28 ], durian skin fiber [ 29 ], cotton fiber [ 30 ], rice straw fiber [ 17 , 31 ], bamboo fiber [ 28 , 32 ], water bamboo husk [ 33 ], micro fibers separated from wheat husk and rye husk [ 34 ], fibers extracted from cuphea and lesquerella seeds [ 35 ], milkweed fiber [ 36 ], artichoke fiber [ 37 ], nutshells powders from almond, pistachio and walnut [ 38 ], micropowders derived from agricultural by-products such as oat husks, cocoa shells, and apple solids that remain after pressing [ 39 ], acorn powder [ 40 ], bleached birch kraft fiber [ 41 ], recycled newspaper cellulose fiber [ 42 ], fully bleached sulphite softwood pulp [ 43 ], and wood flours [ 28 , 44 , 45 , 46 , 47 , 48 ] are being added to biodegradable polymers, e.g., PLA to develop green composite materials. PLA biocomposites provide a means to produce relatively inexpensive PLA-based composites with a variety of properties.…”

“…The natural fiber/matrix interface plays an important role on the physical, chemical and mechanical properties of composites. To improve the interfacial properties, natural fibers are subjected to various physical and chemical treatments such as hydrothermal modification [ 47 ] sodium hydroxide (NaOH) treatment [ 19 , 23 , 24 , 26 , 27 , 29 , 45 ], NaOH + acetylation treatment [ 45 ], NaOH + silane treatment [ 45 ], silane treatment [ 18 , 19 , 24 , 26 , 27 , 40 , 47 ], aluminum acid ester coupling agent and stearic acid treatment [ 28 ], isocyanate treatment [ 32 , 40 ], butantetracarboxylic acid treatment [ 41 ], stearic acid treatment [ 47 ], maleic anhydride (MAH) treatment [ 47 ], MAH + dicumyl peroxide modification [ 17 ], enzyme modification [ 34 ], and with addition of chitosan [ 46 ], citrate esters [ 21 ], lignin [ 30 ], poly(butyl acrylate) ( in situ suspension polymerization) [ 31 ], PLA grafted with MAH [ 40 ], and ethylene-methyl acrylate-glycidyl methacrylate (EMAGMA) [ 44 ]. The surface modification of natural fiber facilitates the fiber dispersion and induces bond formation between the fiber and the PLA matrix.…”