Effects of Surface Treatment of Ground Rice Husk on the Polyurethane Based on Castor Oil

Abstract

Polyurethane (PU) elastomer based on castor oil and polymeric diphenylmethane diisocyanate (PMDI) was synthesised with NCO/OH ratio = 2 as a polymeric matrix. Polyurethane was composited with rice husk with average particle size less than 200 μm. Ground rice husk was pretreated by steam and sodium hydroxide solution in order to study and evaluate the effect of different surface treatment methods on the properties of the polyurethane composites. Scanning Electron Microscopy (SEM) was used to investigate dispersion and fracture surfaces of the composites. Mechanical test (hardness), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC), were employed to characterise the developed composite materials in details. Composite polyurethanes based on treated and untreated rice husk showed different physical, chemical and mechanical properties. SEM micrographs of PU-treated rice husk (steam) displayed rice husk tightly embedded in the PU matrix with uniform distribution. The steam treatment increased the interfacial adhesion within the material, which showed a high thermal stability. PU-treated rice husk (sodium hydroxide 10 wt.%) showed poor mechanical properties. Untreated rice husk showed moderate mechanical properties as compared to the preceding cases.