稻壳粉/改性脲醛树脂模压成型材料的力学性能

    Mechanical properties of moulding material made from crop stalks and modified UF resin

    • 摘要: 为了研究成型材料对模压花盆力学性能的影响,该文以改性脲醛树脂为基体树脂,稻壳与稻壳粉为增强材料,经混炼、热压、成型工序,制备出一种环保花盆。探讨了脲醛树脂改性、改性脲醛树脂用量、稻壳与稻壳粉比例以及湿循环处理对花盆力学性能的影响,采用热重分析仪(thermo-gravimetric analysis,TGA)及扫描电子显微镜(scanning electronic microscope,SEM)分析了秸秆花盆湿循环处理前后的热稳定性及微观结构。结果显示:改性脲醛树脂和稻壳粉有利于改善秸秆花盆的力学性能,当增强填料与基体树脂的比例为1:0.5,稻壳占稻壳粉的质量分数为30 %时,花盆的静曲强度(modulus of rupture,MOR)、弹性模量(modulus of elastic,MOE)及拉伸强度(tensile strength,TS)分别达75.48 MPa、16.06 GPa、17.44 MPa;湿循环处理试验中,以稻壳为增强材料为例,当基体树脂为改性脲醛树脂时,其MOR、MOE及TS分别降低21.97 %、24.91 %、15.09 %;当基体树脂为大豆蛋白改性脲醛树脂时,其MOR、MOE和TS分别降低9.92 %、15.37 %、30.10 %。热重分析发现湿循环处理后花盆热稳定性有所提高,微商热重出现最大失重率的温度向高温侧偏移29.5℃。扫描电子显微镜分析表明湿循环处理后样品表面粗糙度增加,增强体与树脂发生分离。该研究结果为进一步研究秸秆花盆制作工艺和使用年限的相关性提供理论依据。

       

      Abstract: Abstract: Due to advantages in being lightweight, inexpensive, biodegradable, and an easy process, composite materials with plant fiber filler have been widely applied in industry, agriculture, national defense, and other fields. In this study, flowerpots in a friendly environment were moulding-prepared through the procedure of mixing and hot-pressing in an oil hydraulic machine. The flowerpots were made of rice husk, rice husk power, and modified urea-formaldehyde resin. The rice husk or husk power components were added as reinforcing agents, while the resin component was added as a matrix material. The purpose of this paper is to discuss the influence of the dosage of urea-formaldehyde resin (UF), modified urea-formaldehyde resin (SUF), ratio of rice husk and rice husk power, and the wet cycle treatment on the mechanical property of the flowerpots. Thermal stability and microstructure of the flowerpots treated with the rewetting method were analyzed by Thermo-gravimetric Analysis (TGA) and a Scanning electronic microscope (SEM). The results showed that the mechanical properties of the flowerpots could be improved by applying modified urea-formaldehyde resin or adding rice husk power. With the dosage of modified UF, modulus of rupture, modulus of elasticity, and tensile strength of the straw flowerpot all improved. The modulus of rupture, modulus of elasticity, and tensile strength were 75.48 MPa, 16.06 GPa, and 17.44 MPa, respectively, when the ratio of reinforcing agent and matrix material was 1:0.5 (w/w) and the ratio of unbroken rice husk and rice husk power was 3:7 (w/w). Wet cycle treatment led mechanical parameter values of all formula specimens to decline in different degrees, with tensile strength and maximum bending deformation of SUF-pot specimens dropping most significantly. Using rice husk as the reinforcing agent (RH) in the wet cycle treatment resulted in the modulus of rupture, modulus of elasticity, and tensile strength of UF/RH to drop to 21.97%、24.91%、and 15.09%, while SUF/RH dropped 9.92%、15.37%, and 30.10%, respectively. TGA analysis showed that the pyrolysis rate and mode of the straw flowerpot materials by wet cycle treatment had been slightly changed; namely materials mass loss rate was reduced and maximum thermal decomposition temperature increased. The SEM graphs of the composites fractured surface showed that the surface of the flowerpots treated by wet cycling had become rough. Some pieces of rice husk divorced from modified urea formaldehyde resin were clearly visible. Obviously, the interface between rice hull and SUF had become weak. This test showed that the straw flowerpots prepared with SUF resin were less stable than those prepared with UF resin, which implied that the former was liable to degrade. In regard to the production costs, the straw flowerpots are more than 10% lower than the plastic flowerpots. Substitution of plastic flowerpots with straw flowerpots would not only be beneficial in reducing white pollution from the use of plastic products, but also in promoting comprehensive utilization of the crop straw. Therefore, there will be an excellent market prospect of straw flowerpots.

       

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