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The application of bamboo fibers (BFs) to reinforce the impact strength of polylactic acid (PLA) is attractive because of its low cost and high specific strength. However, the main disadvantages of PLA/BF composites are their low compatibility and poor interfacial adhesion caused by different surface energies. In this work, a bio‐based compatibilizer is used to modify PLA/BF composites with a BF content up to 30 wt%. First, sebacic acid (SA) and epoxidized soybean oil (ESO) are reacted to obtain ESO‐SA oligomers with different branching and crosslinking structures. Next, ESO‐SA is incorporated into a PLA/BF composite through dynamic vulcanization, and fully bio‐based PLA/BF/ESO‐SA ternary composites are prepared. Compared to the PLA/BF composite without ESO‐SA addition, the impact strength of PLA/BF/16ESO‐SA12 increases from 5.8 to 14.55 KJ/m2. The toughening mechanism results confirm that the chemical structure of ESO‐SA is the key indicator of the toughening efficiency. [ABSTRACT FROM AUTHOR]

In this work, lignin was used as a heterogeneous nucleating agent to increase polylactic acid (PLA) crystallinity. To enhance the gas barrier performance of PLA/LG composite films, two graft copolymers, polylactide‐graft‐glycidyl methacrylate (PLA‐g‐GMA) and polylactide‐graft‐poly (ethylene glycol) methyl ether methacrylate (PLA‐g‐PEGMA) were successfully synthesized and separately used as compatibilizers to modify PLA/LG composite properties such as interfacial adhesion, crystallinity, and mechanical properties. Since crystallites can act as obstacles to gas diffusion, the higher the crystallinity of the polymer matrix, the better gas barrier performance of the composite film will be. The crystallinity and crystalline structure of the PLA matrix was demonstrated by wide‐angle X‐ray diffraction and differential scanning calorimetry results. Since LG particles can act as efficient heterogeneous crystal nucleating agents, a roughly 50% reduction in oxygen permeability (PO2) was obtained by adding 1 phr LG to the PLA matrix (PLA/1LG). Following addition of 10 phr PLA‐g‐GMA to the PLA/LG composite, PLA/PLA‐g‐GMA/LG composite films showed lower gas barrier properties than PLA/LG composites without added compatibilizer. Moreover, the interfacial adhesion of PLA/LG composites was significantly improved after addition of PLA‐g‐GMA. Therefore, PLA/PLA‐g‐GMA/3LG showed the highest tensile strength, 33% higher than that of neat PLA. Following addition of 10 phr PLA‐g‐PEGMA to the PLA/LG composite, the long liner side chains of PLA‐g‐PEGMA were able to act as nucleating agents for PLA to promote the crystallization of PLA. Accordingly, PLA/PLA‐g‐PEGMA/3LG with 3 phr LG showed a roughly 86% reduction in PO2 when compared with neat PLA film. [ABSTRACT FROM AUTHOR]

This article reports synthesis and structure property studies of block copolyimides synthesized using diamino room temperature ionic liquids (RTIL) as diamine monomers. Specifically, polyimide oligomers of different lengths were synthesized using 2,2- bis (3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and diamino RTIL (1,3-di(3-aminopropyl) imidazolium bis[(trifluoromethyl) sulfonyl] imide). These oligomers were copolymerized with 6FDA and m-phenylenediamine (MDA) using in situ polymerization to form (6FDA-RTIL)-(6FDA-MDA) block copolyimides. The impact of the length and relative concentration of 6FDA-RTIL oligomer in the copolymer on the resulting thermal, physical, and gas transport properties was monitored. As the concentration of the 6FDA-RTIL segments increased, the backbone of the block copolyimides became more flexible resulting in a decrease in the glass transition temperature (Tg) and an increase in the density. The permeabilities of the RTIL containing copolyimides were consistently lower than those of the base polyimide, 6FDA-MDA, with some increase in selectivities. Interestingly, the permeabilities of films produced with the low molecular weight oligomers were very different than those produced with same composition of the high molecular weight oligomers. This may be indicative of very different morphologies within these copolyimides. [ABSTRACT FROM AUTHOR]