Characterisation and properties of biocomposites fabricated from Cyperus odoratus and linear low density polyetheylene

The potential of Cyperus Odoratus (CY) as a filler was studied. In powder form, CY was mixed with linear low density polyethylene (LLDPE), prior to being fed into a twin screw extruder and subsequently into an injection moulding machine to produce LLDPY/CY biocomposite dumbbell specimens. LLDPE/CY biocomposites with composition ratios of 5% to 20 wt% were studied. The results obtained showed that the increased of CY loading and size resulted in an increment of the Young’s modulus, but slightly reduction in tensile strength and elongation at break (Eb). In addition, as determined through the SEM, the morphology characterisation of tensile fracture surface of these composites showed poor interfacial adhesion between the CY filler and thermoplastic LLDPE matrix. A 5% NaOH treatment on CY improved the tensile strength and Young’s modulus of the LLDPE/CY biocomposites significantly, although it caused a decrement in Eb. The NaOH treatment enhanced both the tensile and thermal properties of the composites. In terms of crystallinity and thermal stability, the treated composites were superior compared with those of the untreated composites. Meanwhile, electron beam irradiation (EBI) was applied on the composites for crosslinking purposes, using a 1.5 MeV electron beam accelerator within the dosage range of 0–150 kGy. Based on the results of the tensile strength, the radiation at 100 kGy caused the optimum absorption by the LLDPE/CY biocomposites. Trimethylolpropane triacrylate (TMPTA) and tripropylene glycol diacrylate (TPGDA) were used as the crosslink promoters and the results indicated that the composites added with TMPTA showed higher tensile properties, thermal stability, gel content, and crystallinity, compared with those of the composites added with TPGDA. Also, the addition of TMPTA and EBI at 100 kGy improved all the physical properties, which provided suitable material based on natural polymer for biocomposites. The presence of TMPTA enhanced the crosslinking of LLDPE/CY during irradiation, which in turn enhanced the thermal stability of the composites. The natural soil burial and weathering of LLDPE/CY biocomposites were carried out for 1 year and the samples were collected and measured after 3, 6, and 12 months for degradability tests, by means of tensile tests, morphological study, and weight loss measurements. Within the 1-year exposure to soil burial and weathering test, the tensile strength and Eb of the composites decreased, while their Young’s modulus increased. The deterioration in weight properties of the composites was investigated, where the presence of CY filler in the composites significantly accelerated the degradation of the LLDPE/CY biocomposites. The effects of cobalt stearate (CS) in natural soil burial and weathering on the properties of LLDPE/CY biocomposites were also examined, and the results indicate that the tensile strength and Eb of the composites decreased, while the Young’s modulus increased with the increment in CY and CS contents. The morphology characterisation through SEM proved that the addition of CS to the composites accelerated their degradation.