**5. Conclusion**

Rice husk biofibre (RHB)-reinforced recycled high-density polyethylene/recycled polyethylene terephthalate (rHDPE/rPET) biocomposites were fabricated via a two-step melt-blending method. The TPB matrix types (UTPB and CTPB) and RHB contents have significantly affected the physical properties, mechanical behaviours, thermal stability and morphological performance of biocomposites. As RHB contents increased from 40 to 80 wt%, tensile and flexural properties as well as thermal stability improved remarkably but reduced the impact strength. In the long-term water immersion test, the water absorption and thickness swelling increased with the content of RHB and immersion time regardless of the matrix types. The diffusion coefficient and swelling rate parameter that are determined from the Fickian and swelling model, respectively, increased with the RHB contents. Biocomposites based on CTPB matrix possessed higher mechanical properties and dimensional stability than those based on UTPB matrix. Based on the findings in this study, it is proven that natural fibres/recycled thermoplastic blend biocomposites are suitable for the outdoor applications such as in the field of buildings and constructions.
