Effect of hot water immersion on tensile and fatigue properties of long glass fibre-reinforced polypropylene

摘要

This paper deals with the effect of hot water immersion on tensile and fatigue properties of long glassfibre-reinforced polypropylene (LGF/PP). Tensile tests and pulsating4ension fatigue tests have beencarried out using smooth specimens of two grades of the material, with and without an acid modifiedpolypropylene (APP). Specimens were immersed in distilled water at 80°C up to 6666 h. In bothmaterials, the weight increased rapidly and reached the maximum value, then decreased graduallywith immersion time. The material without APP showed initially larger increase in weight, but overthe immersion time of 2500 h more remarkable decrease was observed. Since the weight gain of theresin itself was negligible, water entered into the interface between the fibres and the resin. Therefore,the weight loss was attributed to leaching of surface treatment agents and the dissolusion of glassfibres by hot water. The variation in weight with immersion time depended strongly on watertemperature. The weight increased gradually with time in distilled water at ambient temperature andthe material without APP showed larger weight gain than the material with APP, indicating that theaddition of APP was effective in improving water absorption characteristics in LGF/PP. Tensile andfatigue strengths were considerably decreased after hot water immersion, but the material with APPstill exhibited higher strengths than the material without APP. The length of fibres appeared onfracture surfaces tended to be shorter in immersed specimens, suggesting the degradation of thefibres.