Rule of mixture models are usually used in the tensile properties prediction of polymer composites reinforced with synthetic fibres. They are less utilized for natural fibre/polymer composites due to natural fibres physical and mechanical properties variability which reduces rule of mixture model's prediction values accuracy compared to the experimental values. This had led to studies conducted by various researchers to improve the existing rule of mixture models to give a better reflection of the true natural fibres properties and enhance the rule of mixture models prediction accuracy. In this paper, rule of mixture model's utilization includes the existing rule of mixture models as well as proposed rule of mixture models which have one or more factors incorporated into existing rule of mixture models for natural fibre/polymer composites tensile properties prediction are reviewed.

In this study, the kiln-dried oil palm trunk (OPT) was impregnated with phenol formaldehyde (PF) and urea formaldehyde (UF) resin as a matrix using high-pressure vaccum impregnation chamber. Different percentages of resin were loaded in oil palm trunk lumber (OPTL) and compared with kiln-dried OPT and rubberwood (RW). The physical, mechanical, and environmental properties were studied according to BS and ASTM standards. The morphology of resin-loaded OPTL was analyzed by scanning electron microscopy (SEM), while thermal characterization was carried out by thermogravimetric analysis. In general, the OPTL exhibited better values of physical and mechanical properties than dried OPT and OPTL (50% resin loading), which were slightly lower than RW; however, OPTL exhibited good thermal stability compared with dried OPT and RW. Furthermore, the OPTL exhibited a high resistance against termites. The observation of SEM micrograph showed that OPTL with PF resin loading exhibited better morphology than OPTL with UF resin loading, and full penetration of resin into OPT structures was observed.