Geogrids are widely used in foundation engineering for reinforcing foundations due to their light weight, high strength, and excellent performance. In this study, two kinds of polypropylene biaxial geogrids were used, and indoor thermal oxygen and photooxygen aging tests were carried out. The residual mechanical stability of the exposed materials was determined by tensile testing. The results of both accelerated test methods are discussed and compared in detail. After aging of the geogrid, the trend of tensile strength and fracture elongation change with aging time is obtained. The gray prediction model was used to predict the variation in the retention rate of tensile strength in the geogrid with photooxygen aging time. Model tests of cushions were carried out in a large geogroove to compare the load bearing characteristics of pure sand and the unaged and aged geogrid-reinforced sand cushions. The results show that ultraviolet radiation illuminance plays a decisive role in the aging degree of the polypropylene geogrid. The influence of photooxygen aging on the tensile strength and fracture elongation of a polypropylene biaxial geogrid is greater than that of thermal oxygen aging. Different types of polypropylene biaxial geogrids with photooxygen aging showed different retention rates of tensile strength, and the aging resistance of the geogrid with higher tensile strength was significantly higher than that of the geogrid with lower tensile strength. The tensile strength of the geogrid has an effect on the bearing capacity of reinforced sand cushions. Under proper elongation, the bearing capacity of the reinforced sand cushion is clearly improved compared with that of the unreinforced cushion. The aging behavior of the two geogrids reduces the load bearing capacity of the reinforced cushion by influencing the property of the interface between the geogrid and sand.

Catalytic oxidization has been studied for elimination of indoor formaldehyde. It was found that manganese dioxide (MnO2) is the most effective catalyst among all the tested catalysts at room condition. In the present investigation, the formaldehyde removal efficiency of several commercially available MnO2 catalysts was studied with typical method. Studies showed that the efficiency of MnO2 can be affected by the particle size, the dispersity and the work hours.

The thermal conductive composites prepared by twin-screw extrusion extrudes polypropylene and graphite.This paper studies the influence of molding process on the thermal conductivity.The experimental results show that thermal conductivity of composites changes with the screw rotate speed changing,obtaining the maximum when the screw rotate speed is 300r/min.Results indicate that the opposite trend with thermal conductivity and the melt index and injection speed,and the injection temperature has not a big influence on the thermal conductivity. The crystallization influences the electrical conductivity and density of some points of molding samples.In addition,the test condition has cast impact on thermal conductivity,in the lower temperature(lower than the Debye temperature),the thermal conductivity of composites increased with the of temperature and humidity increasing.