Effect of silane coupling agent pretreatment on the properties of rice straw particleboard bonded with prevulcanized natural rubber latex

Abstract

Burning rice straw particles is a problem for generating atmospheric particulate matter (PM2.5) in Thailand. Increase in value-added rice straw such as production of rice straw particle board is an attractively promising product. The prevulcanized natural rubber-bonded rice straw particles using bis-(3-triethoxysilylpropyl)tetra sulphide (Si-69) acting as silane coupling agents were used to produce rice straw particle board. The effect of Si-69 concentrations of 2, 5, 7, and 10%w/v on the properties of rice straw particle board was investigated. The surfaces of treated rice straw particles were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). In addition, modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding (IB) thickness swelling (TS) and water absorption (WA) of the prepared samples were measured. The result illustrated that the rice straw particle board was successfully manufactured using prevulcanized natural rubber and Si-69 coupling agent. The rice straw surface was fully covered by Si-69 and the amount of silicon and sulphur elements were increased with increasing Si-69 concentration. Consequently, the IB, MOR and MOE of the rice straw particle tended to increase with increasing Si-69 concentration. This is possibly due to good interfacial adhesion and reasonable stress transfer between rice straw particles and prevulcanized natural rubber as well as higher crosslink density of prevulcanized natural rubber. On the other hand, TS and WA of the rice straw particle were sharply decreased with increasing Si-69 concentration because the rice straw surface may be partially covered by the hydrophobic parts of Si-69.