Use of commercial synthetic filament waste to reinforce biobased poly(butylene succinate) with the aid of compatibilizers

Since poly(butylene succinate) (PBS) has low rigidity for engineering application, this research attempted to reinforce PBS with poly(ethylene terephthalate) (PET) and polyamide-6 (nylon6) filaments with the reservation of polymer toughness. Filaments were chopped to be short fibers (length of 2 mm to 4 mm) and melt compounded with PBS pellets in the weight ratio of 1 wt%, 5 wt%, and 7 wt% using a twin-screw extruder that the temperature profile was set high enough for melting only PBS matrix. Two types of compatibilizers; hexamethylene diisocyanate (HMDI) or hexamethylene diamine (HMDA) of 0.05 wt% were used to treat fiber surface. It was found that tensile modulus of PBS increased with respect to fiber concentration, which untreated PET fibers provided higher tensile modulus about 2% to 7%. Surface treatment of fibers with either HMDI or HMDA increased rigidity of the composites, while elongation at break and impact strength were also improved with respect to fiber concentration. Also, shifting in glass transition temperature of PBS by DMA indicated improved interfacial interaction, which HMDA treatment gave the best benefit for mechanical properties. Number-average molecular weight of HMDI-treated composites was closed to extruded PBS, however, those of HMDA-treated composites were reduced dramatically implying chain scission highly occurred. SEM micrographs revealed good interfacial adhesion obtained after fiber treatment. Crystallization of PBS studied by XRD showed that the crystal form was not affected by the compatibilizer.