羽毛角蛋白改性脲醛树脂模压秸秆花盆力学及降解性能

Mechanical and degradation properties of molded straw flowerpot prepared by modified urea-formaldehyde adhesive with feather keratin

为解决现有秸秆模压花盆使用不可降解脲醛树脂导致秸秆花盆废弃后难降解的问题,该研究使用还原法从家禽废弃羽毛中提取角蛋白,替代部分尿素与甲醛缩聚合成改性脲醛树脂,并与微生物改性的水稻秸秆混合模压成一种绿色环保可降解花盆。采用傅立叶红外光谱和热重分析仪探讨改性脲醛树脂的官能团变化及热力学性质,同时采用三点弯曲试验、微生物降解能力试验及土壤掩埋降解试验探究模压制备秸秆花盆的力学强度变化和生物降解性能。结果表明:角蛋白能够降低脲醛树脂中的游离甲醛含量,提升胶黏剂的粘度,角蛋白中的-NH和-COOH基团有利于与脲醛树脂的共聚,从而形成交联网络。角蛋白质量为尿素总量3%时,代表树脂缩聚交联结构的第三热解峰对应温度285.8℃,相比于未改性脲醛树脂提升5.0%,热稳定性最好,与脲醛树脂相比,添加角蛋白的改性脲醛树脂的最终残碳量均不同程度降低,有利于其制备的复合材料自然降解。与此同时,角蛋白质量为尿素总量3%时,改性脲醛树脂模压制备的秸秆花盆弹性模量和抗弯强度最优,分别为2552和47.7 MPa,相比于未改性脲醛树脂制备的花盆提升8.97%和85.59%。角蛋白质量为尿素总量5%时,改性脲醛树脂模压制备的秸秆花盆生物降解性能最佳,28 d后微生物在秸秆花盆表面的生长面积达到91.2%,6个月后秸秆花盆的剩余质量百分比为64.10%,相比于未改性脲醛树脂降解速度提升80.95%。该研究提供一种可降解秸秆花盆创制方式,合理消纳废弃畜禽羽毛和农业秸秆,可为废弃物处置利用提供参考。

Discarded Straw flowerpots are usually difficult to degrade in the soil environment,due mainly to the non-degradable urea-formaldehyde adhesive during molding.In this study,keratin was extracted from the wastes of poultry feathers using reduction,instead of part of urea and the extracted keratin polycondenses with formaldehyde,further to synthesize a modified urea-formaldehyde adhesive for the straw flowerpots.The modified urea-formaldehyde adhesive was then mixed with the rice straw of biological modification to mold a green and environment-friendly degradable flowerpot.An investigation was made to explore the effect of different contents of keratin on the physical and chemical properties of modified urea-formaldehyde as well as the influence of modified urea-formaldehyde on the mechanical and biodegradable properties.Fourier infrared spectroscopy and thermogravimetric analysis were used to characterize the basic adhesive properties of urea-formaldehyde adhesive,thereby analyzing the changes of functional group and thermodynamic properties of the modified urea-formaldehyde adhesive.At the same time,three-point bending tests,microbial degradation ability tests,and degradation in soil tests were also carried out to determine the variation in the mechanical strength and biodegradability of molded straw flowerpots.The results showed that keratin significantly reduced the content of free formaldehyde in the urea-formaldehyde adhesive with a higher viscosity.The-NH and-COOH groups in keratin were favorable for the copolymerization with UF adhesive,where a cross-linking network was formed.The temperature of the third pyrolysis peak was 285.8℃representing the adhesive polycondensation cross-linked structure when the keratin content was 3%.The modified urea-formaldehyde adhesive increased by 5.0%,compared with non-free formaldehyde,indicating the best thermal stability.Furthermore,the final carbon residuals of modified urea-formaldehyde adhesive were all reduced with different contents of keratin,compared with UF,indicating suitable for natural degradation of composites prepared by the modified urea-formaldehyde and straw fibers.Meanwhile,the best elastic modulus and flexural strength were achieved in 2552 and 47.7 MPa for the straw flowerpots with 3%keratin-modified urea-formaldehyde adhesive,indicating the increases of 8.97%and 85.59%,respectively,compared with the unmodified.NH and-COOH groups of keratin normally participated in the adhesive body structure,thereby achieving better crosslinking adhesive in the substrate surface infiltration formed on the solid bonding interface.Since too much keratin cannot participate in the shape of the structure during the crosslinking reaction,the reduction in the conduction process made a great contribution to the decrease in the strength of bonding interface stress of composites,thus determining the macroscopic mechanical properties of the material.Additionally,the best biodegradability was also achieved in the straw molded flowerpot with 5%keratin-modified urea-formaldehyde adhesive.The microbial growth area was 91.2%on the straw flowerpot surface in 28 days,while the residual mass percentage of straw flowerpot in 6 months was 64.10%.Consequently,the degradation muss loss increased by 80.95%,respectively,compared with the unmodified.This finding can provide strong theoretical support to create the degradable straw flowerpots.In this case,crops straws can widely be expected for waste disposal and utilization in sustainable agriculture.