Response surface optimization and statistical analysis of composites made from calcium carbonate filler-added recycled polypropylene and rubberwood fiber

Abstract

Mixture design method of experiments was used to determine the compositions of wood-plastic composite samples manufactured from recycled polypropylene (rPP), rubberwood flour (RWF), and calcium carbonate (CC). Factors were determined the mixture compositions rPP, RWF, CC, maleic anhydride-grafted polypropylene (MAPP), ultraviolet (UV) stabilizer, and lubricant (Lub) on properties of the samples, namely tension, compression, surface roughness, water absorption (WA), thickness swelling (TS), and thermogravimetric analysis (TGA). The specimens were produced by extrusion and compression molding methods. The analysis of variance and response surface methodology were employed for the analysis and optimization of the compositions. Optimal composition for overall response was 51.8 wt% rPP, 35.9 wt% RWF, 7.2 wt% CC, 3.9 wt% MAPP, 0.2 wt% UV stabilizer, and 1.0 wt% Lub with desirability score combining their output value of 0.757. The addition of CC content increased the mechanical properties but decreased the WA and TS. A high RWF content increased WA and TS with longer immersion times. The TGA of composites mainly depends on the chemical components of RWF and rPP types. The scanning electron microscope morphology in the composites with different amount of CC increased their densities due to good dispersion of CC as filler and good contact between the RWF reinforcement and rPP matrix.