Effect of using two types of coupling agent in the poplar-polypropylene particleboard manufacturing on its mechanical and physical properties

Wood plastic composites in recent years have been the attention of many researchers. The major part the combination of these composites, lignocellulosic material constituted. The disadvantages of natural fiber can be mentioned incompatibility between the hydrophilic fibers and hydrophobic polymers. This problem can be reduced by incorporation of coupling agent into the compound. Because of the addition of coupling agent, the interface between two phases of lignocellulosic fiber and polymeric matrix improve. This study with aim of investigation the effect of two types of coupling agent on mechanical and physical properties of particleboard made of polypropylene- poplar was done.

in this research, the mixing ratio of poplar wood to polypropylene at level of 90:10 was used. Phenol formaldehyde resin used at 8 percent level of dry weight of raw material. Two types of coupling agents of maleic anhydride grafted to polypropylene and triethoxymethylsilane in level of 6 percent based on dry weight of polypropylene were used. Coupling agents were used in two different methods including inside the resin and on the polypropylene particles. After the mixing process raw material together, mat at temperature of 180°c for 5 minutes under hot press was placed. The physical and mechanical properties were evaluated according to European standards set of EN. Physical and mechanical properties of panels analyzed using factorial analysis in 5% probability level.

The results showed, the addition of both types of silane and MAPP coupling agents improved the bending strength, modulus of elasticity and internal bonding, while decreased water absorption and thickness swelling of the boards compared to the control sample (without coupling agent). Compared to the silane coupling agent, MAPP coupling agent created more favorable properties in the boards. The addition method of coupling agent on the polypropylene particles in comparison with inside resin improved the physical and mechanical properties of the boards. Because in the addition method of coupling agent on the polypropylene, all of the coupling contents are placed on the polypropylene particles, and therefore, the presence of the coupling agent on the interface between the polymer phase and the reinforcement phase increases.

According to the results of this research, using of coupling agent increased significantly the dimensional stability of the boards. The addition of coupling agents increased bending strength, modulus of elasticity and internal bonding of boards. Compared to the properties of the boards produced by EN standard, with addition method of MAPP on the polypropylene can be produced particleboards with favorable properties for use in dry conditions (Type P3).