Use of oil palm frond waste to reinforce poly(lactic acid) based composites with the improvement of interfacial adhesion by alkali treatment

Abstract

Oil palm frond waste was used as reinforcing fibers for biodegradable poly(lactic acid) or PLA in order to produce green composites that increased the value of agricultural waste. The alkali-treated oil palm frond (OPF) fibers of 30 wt% or 40 wt% were compounded with PLA and moulded into specimens. The alkali treatment was 0 wt%, 1 wt%, 3 wt%, and 5 wt% of the fibers for compatibility improvement with PLA matrix. It was found that the alkali-treated PLA/OPF composites adding 30 wt% and 40 wt% had the flexural modulus to be about 55% and 75% higher than those without the treatment, respectively. Tensile modulus of the composites was also increased. Nevertheless, the higher rigidity composites became more brittle as evident by the fracture toughness testing. The increase of total breaking energy confirmed the better interfacial adhesion between phases as shown in SEM micrographs. The glass transition temperature (Tg) of PLA matrix in the composites was shifted to lower temperature attributed to the thermal degradation of PLA during the melt compounding confirmed by the lower degradation temperature. Increasing the alkali concentration for surface treatment caused the Tg of PLA composites to be higher, supporting that the improvement of interfacial adhesion was achieved.