Response surface optimization of hybrid composites reinforced crab shell flour and rubberwood sawdust for waterproof composite products in tropical countries

Abstract

Hybrid composites reinforced with crab shell (CS) waste and rubberwood sawdust (RWS) were developed for applications in tropical countries. D-optimal mixture design was applied in experiments, to determine the effects on three main fractions including recycled polypropylene (rPP), RWS, and CS on the mechanical properties after immersing in distilled water and seawater. Response Surface Methodology (RSM) was used to identify the optimal formulation that maximizes the mechanical properties. The results indicated that the mechanical properties fit best with the quadratic models. Statistical analysis revealed that all the models had a less p value than 0.05 and could accurately predict the mechanical properties. Moreover, these factors negatively affected the mechanical properties whereas the CS had the highest coefficient of all the models. Mechanical properties of the hybrid composites immersed in seawater decreased significantly compared to those immersed in distilled water. Therefore, the optimal formulation of overall mechanical properties was 55.1-wt% rPP, 32.5-wt% RWS, 6.9-wt% CS, 4.0-wt% maleic anhydride-grafted polypropylene, 0.5-wt% ultraviolet stabilizer, and 1.0-wt% lubricant with a desirability score of 0.976. Finally, the optimal formulation of the hybrid composites has been presented and is expected to be applied for applications and waste management from natural materials.