Abstract:
Pultrusion process is suitable for forming constant cross-section and continuous composite. Generally, this process is known as thermosetting pultrusion process using thermosetting resin as a matrix. Currently, thermoplastic pultrusion process has not been studied and this composite has not been produced widely for industrial and commercial materials comparing with thermosetting pultrusion process. Thermoplastic pultrusion is performed by pulling reinforcement fibers and thermoplastic fiber through the heated die causing melting and impregnation in the reinforcement fibers. The fibers were pulled though the constant cross-section of the heated die to form continuous composite.
In this research, polypropylene fibers were used as matrix resin and jute fibers were used as reinforcement fiber whereas glass fibers were used as additional reinforcement fiber to strengthen its structure for the successful pultrusion process. The filling ratio of fiber was an important parameter of this process calculating from the ratio of cross-section of materials to cross-section of the molding die. This ratio was designed over 100 % so the ratio of 100.52 % was employed consisting of 23.06 % jute fiber, 9.01 % glass fiber and 68.45 % polypropylene fiber. Pultrusion temperatures were set at 190, 200, 210, and 220 oC and pulling speeds were 40, 100, and 140 mm/min. The microstructure was examined to evaluate the impregnation quality of resin into fiber bundle by using Photoshop CS6 and ImageJ 1.52a. Tensile (ASTM D3039) and flexural test (ASTM D790) were conducted to evaluate these composites strength.
The continuous composite from jute fibers reinforced polypropylene was successfully fabricated by thermoplastic pultrusion process with the size of 25 X 3 millimeter, and the length of 1,500 millimeter. All reinforced fibers were performed in unidirection. From the microstructure examination, it was found that the pultrusion temperature and speed affected the impregnation quality of polypropylene resin and void content in the composite. The resin was impregnated into the fiber bundle better at higher temperature while higher speed decreased the resin impregnation. Higher pultrusion temperature caused higher mechanical properties. Pultrusion temperature of 200 oC showed the best mechanical properties. When the temperature was over 200 oC, the mechanical properties decreased despite of good impregnation qualities. This was because jute fiber was affected by high temperature similar to its degradation point. Moreover, when the pultrusion speed increased, the impregnation and mechanical properties decreased. The best pultrusion speed was 40 mm/min. Therefore, this research can be used as a guideline to design thermoplastic pultrusion process suitable for continuous composite from natural fibers reinforced in the thermoplastic matrix.