Sea Water Aging Of Glass Fiber / Unsaturated Polyester Composites

Materials are the physical foundation to improve the level of all production and people's life and also are the milestone of human progress. So it is of much important significance to do some basic research on materials. Glass fiber reinforced unsaturated polyester resin plastic has high ratio of property to price and is applied in many industrial fields increasingly. The GFRP based on unsaturated polyester resin owns better technical property and it is cheaper than epoxy one so it is widely used in marine industry. Ocean petroleum and gas exploitation is the industry which owns wide foreground and is the new market of GFRP. These GFRP products are inevitably immersed by sea-water so there are certain practical value to study the property of this material immersed in sea-water environment.Samples are immersed in sea water for different days in room temperature and then the water-absorption rate and the static mechanical property (such as tensile strength, bending modulus and impacting strength) are studied. Material's water-absorption rate mates the Fick's rule during the short-term immersion but after long-term immersion it deviates the Fick's rule appearing the phenomenon of losing weight through observing the fitting curve of water-absorption rate. The material's static mechanical properties have similar downtrend and the downtrend is in the form of exponent through observing the tensile fitting curve. The bonding interface of fiber and resin is demolished demonstrated by dynamic mechanical thermal analysis (DMTA). The results show that the storage modulus (E') and the glass transition temperature (Tg) of GF/UP composite decreases with prolonged immersion time, while the loss factor (tanδ) increases. There are not only plasticization and swelling but also hydrolysis reactions in the material during immersion. These reactions are important reasons which induce the downtrend of material's properties. The probable hydrolysis reaction equation which would occur in resin and glass fiber is indicated. A great deal of cracks and holes appear on the face of GF/UP composite after immersion while the interface between fiber and resin is damaged seriously demonstrated by the SEM photoes.