Pretreatment of the sisal fiber (SF) grafting with L‐lactide (LA) monomer via a ring‐opening polymerization catalyzed by a Sn(II)‐based catalyst was performed to improve the interfacial adhesion between SF and poly (lactic acid) (PLA). Biocomposites from LA‐grafted SF (SF‐g‐LA) and PLA were prepared by compression molding with fiber weight fraction of 10, 20, 30, and 40%, and then were investigated in contrast with alkali‐treated sisal fiber (ASF) reinforced PLA composites and untreated SF reinforced PLA composites. PLA composites reinforced by half‐and‐half SF‐g‐LA/untreated SF (half SF‐g‐LA) were prepared and studied as well, considering the disadvantages of SF‐g‐LA. The results showed that both the tensile properties and flexural properties of the SF‐g‐LA reinforced PLA composites were improved noticeably as the introduction of SF‐g‐LA, compared with pure PLA, untreated SF reinforced PLA composites and ASF reinforced PLA composites. The mechanical properties of the half SF‐g‐LA reinforced PLA composites were not worse, even better in some aspects, than the SF‐g‐LA reinforced PLA composites. Fourier transform infrared analysis and differential scanning calorimetry analysis exhibited that both the chemical composition and crystal structure of the SFs changed after LA grafting. In addition, the fracture surface morphology of the composites was studied by scanning electron microscopy. The morphological studies demonstrated that a better adhesion between LA‐grafted SF and PLA matrix was achieved. POLYM. COMPOS., 37:802–809, 2016. © 2014 Society of Plastics Engineers

Sisal fibers were pretreated by alkali and alkylation, and then mixed with polylactic acid to make sisal fiber-reinforced polylactic acid composites, respectively. The architecture and aspect ratio of sisal fibers before and after mixing, the micro-morphology of fracture surface, and the properties of composites were investigated. The results showed that surface treatment greatly impacted the fiber fracture behavior. Shearing fracture occurred to the untreated sisal fibers and alkali-treated sisal fibers, which led to a sharp reduction in the length of the fiber, while the sheartear facture occurred to the alkylation-treated sisal fibers and resulted in obvious decrease in both length and diameter of alkylation-treated sisal fibers. The fiber aspect ratio of sisal fibers was affected first by the pretreatment method, then by the processing temperature, and the sisal fiber content. Furthermore, the mechanical properties of reinforcing fibers and sisal fiber-reinforced polylactic acid composites were influenced fundamentally by the pretreatment method.

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The in situ reactive interfacial compatibilization and properties of polylactide/sisal fiber biocomposites made via melt blending with an epoxy-functionalized terpolymer elastomer were investigated.

Untreated sisal and coir fibers (USF and UCF), alkali‐treated sisal and coir fibers (ASF and ACF), and alkali‐treated sisal/coir hybrid fibers (ASF/ACF) reinforced polylactide (PLA) composites were prepared by compression molding technique. The materials were characterized in terms of tensile, flexural, and impact properties. While all mechanical tests showed that the composites reinforced by alkali‐treated fibers could withstand more fracture strain than untreated fibers reinforced composites which could be attributed to the improved interfacial adhesion between alkali‐treated fibers and matrix related to the remove of lignin, hemicellulose and pectin by the alkali treatment, the addition of ACF in PLA/ASF composites improved the impact strength of PLA/ASF/ACF composites and showed a positive effect. More fibers tended to be torn apart or fractured, but less pulled out with the increase of coir fiber content. Compared to other composites, the ASF/ACF‐reinforced PLA composites offered superior mechanical properties when the ratio of sisal to coir was 7:3. POLYM. COMPOS., 39:E188–E199, 2018. © 2017 Society of Plastics Engineers