Modeling and optimization of tensile strength and modulus of polypropylene/kenaf fiber biocomposites using Box–Behnken response surface method

Abstract

The aim of this work includes modeling and optimization of the tensile properties of natural fiber biocomposites using the concept of experimental design. A three‐factor, three‐level Box–Behnken design, which is subset of the response surface methodology (RSM), has been applied to present mathematical models. The effect of three independent variables; kenaf fiber load, fiber length and polypropylene‐grafted maleic anhydride (PP‐g‐MA) compatibilizer content have been investigated on the tensile strength and modulus of polypropylene/kenaf fiber/PP‐g‐MA biocomposite. These models can be used as an interesting method for analytically evaluating both the tensile strength values and their corresponding tensile modulus as function of independent variables. The optimization results, obtained using the optimization part of Design‐Expert Software, showed that the most optimal tensile strength and tensile modulus were to be 32.70 MPa and 2,182.33 MPa, respectively; and achieved at 28.95 wt% of the kenaf fiber, fiber length of 6.22 mm and PP‐g‐MA content of 5 wt%. The obtained values and normal probability plots indicated a good agreement between the experimental results and those predicted by the model (above 0.95 for all the responses). Moreover, the tensile modulus of the biocomposite was analyzed by means of micromechanical models. The performance of the Halpin–Tsai and Cox–Krenchel models in predicting the tensile modulus of biocomposites was compared with available experimental results. In addition, the fracture surface morphologies and wettability of the samples were investigated by scanning electron microscopy (SEM) and contact angle measurement, respectively. It was found that the fiber load and PP‐g‐MA compatibilizer content play a significant role in the tensile properties and morphology of the biocomposites, as proven by SEM and contact angle measurement. POLYM. COMPOS., 39:E463–E479, 2018. © 2017 Society of Plastics Engineers