干旱区生态环境知识资源中心

The utilization of new polymeric materials as sand-fixing agents has become very popular in desertification control. These materials have relatively better performance in protecting sand from wind and water erosion, but the durability in aggressive environments is highly important. Therefore, with this important factor in mind, a novel hydrophilic polyurethane has been developed and studied in this research which presents a significant effect on sand fixing. In this study, the aging performance under sunlight, corrosion behaviour under the conditions of acid, alkali, salt, freeze and thaw are considered. Specimens, consisting of sand-fixing bodies solidified by hydrophilic polyurethane (W-OH), were exposed to Xenon Lamp, freeze-thaw cycles and immersed in acidic, alkali, salt solutions. Mechanical properties of compressive strength and hardness were chosen as the indexes to evaluate the performance. The results demonstrated that in all conditions the loss rates for compressive strength and hardness of sand fixation body decreased with the increase of W-OH concentrations, the higher concentrations, and the bigger cohesion force were observed. The concentration of W-OH had a relatively large effect on hardness and comprehensive strength, the increased rates could reach 16% and 50%, respectively. When the specimens were exposed in simulation irradiation and immersed in the acid, and alkali solutions after 5 weeks, creep occurs in the surface and structure. The loss rate of hardness was relatively big exceeding 10% when the concentration of W-OH is 3%, while the loss rate is smaller and insignificant in the condition of 4% and 5% W-OH and salt solutions. Moreover, the loss rates of compressive strength also decreased less in all above conditions less than 5%, so the decrease in mechanical performance was negligible. However, the corrosion resistances were slightly different and the results demonstrated that the resistance to salt was higher compared with the one for acid and the resistance to alkali was the weakest. Moreover, loss rate of hardness in concentrations of 3%, 4% and 5% W-OH sand-fixing specimens were 6.5%, 5.2% and 4% after treatment of 50 freeze-thaw cycles, and the corresponding loss rate of compressive stress were respectively 10.2%, 6.5% and 4.9%, indicating that compressive strength was more sensitive in freeze thaw condition. Therefore, when W-OH is used in sand fixation, its concentrations should be considered and selected to guarantee the effect and durability.