Durability Evaluation Of Glass Fiber Reinforced Vinyl Ester Resin Composites

In present, woven E-glass fiber reinforced vinyl ester resin(GF/VE) composite is the most frequently used materials of battery containers. So the study of corrosion behavior and durable years of GF/VE composites is significative to the lifetime evaluation of battery. The corrosion behavior of GF/VE composites has been studied. Acid immersion test was achieved by immersing the composites in 40 wt % sulfuric acid solution at constant temperature of 35℃, 55℃, 65℃and 75℃for more than 3000 hours by accelerated ageing test. Weight change of vinyl ester resin cast, covered and uncovered composites were characterized through weight measurements, the Fe-ion in glass fiber depleted in solution was tested through spectrophotometric method and the change of flexural properties, thermal properties and electrical resistance before and after corrosion were tested. The corrosion rate of GF/VE composites was studied by fitting their weight changing curves then taking first derivative and the corrosion mechanism was analyzed. At last, the lifetime of GF/VE composite was predicted based on Arrhenius equation through least square method.The results showed that the weight change of vinyl ester resin cast increased quickly with immersion time at first and then slow down with a nearly constant invariable value in the final stage which is similar to weight change of covered composites while the weight change of uncovered composites were kept on increasing with the corrosion rate going faster and faster. The weight changes of all the three were increased with the increase of temperature. The mass of Fe-ion in solution was increased with both corrosion time and temperature, which was the same to the weight changes trend of composites. Flexural strength and electrical resistance of GF/VE composites were decreased with corrosion time and the increase in temperature.Combining the analysis above, corrosion of GF/VE composites in 40 wt % sulfuric acid solution were mainly corroded by resin corrosion in initial state with small molecules entered the resin producing swelling of resin and then after the resin get saturated, the main corrosion in the following state was the interphase and glass fiber corrosion.Combine to the corrosion mechanism, a method consists of two stages was put forward to predict the lifetime of GF/VE composites. The first stage was considered to be the time resin matrix get saturated and the second stage was the limited time of interphase and fiber getting corroded with material out of protection and the weakness was breached through. With the weight change of composite reached the technical target in GJB5270-2003, a lifetime of GF/VE composite was predicted of about 10 years.