Effect of Surface Tension on the Impregnation of Glass Fiber Mat Reinforced Thermoplastic (GMT)

The flow of the melted polypropylene among the glass fibers was observed at 200 ℃ by a microscope with a heater. The results show that under the effect of the surface tension the melted polypropylene can flow spontaneously in the micropores formed by the fibers. With the decreasing of the fiber gap, the flow rate of the polypropylene resin increases obviously. And the flow rate of the polypropylene accelerates after a short time of the spontaneous flow. Furthermore, the critical capillary diameter between the fibers and the lowest pressure for the spontaneous flow can be calculated indirectly by determination of the width of the melted polypropylene in the cross fibers.