Mechanical and biodegradable properties of L-lactide-grafted sisal fiber reinforced polylactide composites

Sisal fiber (SF) was grafted with low polymerization degree polylactide (PLA) according to the principle of coordinative ring-opening polymerization of lactide, and then the lactide-grafted sisal fiber (SF-g-LA) was mixed with PLA to make PLA/SF-g-LA composites. The mechanical properties, morphology, and biodegradability of PLA/SF-g-LA composites were systematically investigated, comparing with untreated SF reinforced PLA (PLA/USF) and alkali-treated SF reinforced PLA (PLA/ASF) composites. Results showed that the interfacial properties between SF-g-LA and PLA matrix showed dramatic improvement. The PLA/SF-g-LA composites exhibited noticeably superior tensile and flexural properties; however, their impact strength decreased slightly compared with pure PLA. All of the composites were buried in soil and different degrees of degradation were achieved. Because of better interfacial adhesion between SF-g-LA and PLA matrix, the degradation rate of PLA/SF-g-LA composite was lower than those of PLA/USF and PLA/ASF composites, although still higher than that of pure PLA. The biodegradation of PLA/SF-g-LA composites was marked by appearance of cavities, the exfoliation of fragmental materials, and the degradation of cellulose fibrils.