作 者：
孙宗兴;叶仁伟;荐佳琳;宋楠;刘亭;付晴雨;高振华
关键词：
大豆胶黏剂;环氧氯丙烷-聚酰胺多胺树脂;pH;交联特性;胶合性能
摘 要：
由聚酰胺多胺-环氧氯丙烷(PAE)树脂和脱脂豆粉复合制得的人造板用无醛大豆胶黏剂,其pH与PAE树脂的交联固化特性、大豆蛋白的溶解分散特性以及胶黏剂的胶合性能等密切相关,通过调控PAE树脂溶液的pH,采用傅里叶红外分析(FT-IR)、X射线衍射(XRD)、溶胶-凝胶测试、~(13)C NMR固体核磁等现代分析方法结合胶黏剂性能评价,探究PAE溶液pH对大豆胶黏剂结构与性能的影响。结果表明,改变PAE溶液pH对大豆蛋白胶黏剂的黏度、适用期、结晶度、交联特性、胶接耐水性能及大豆蛋白二级结构都会产生重要影响。综合FT-IR和XRD分析结果可知:当PAE溶液的pH大于4.6后进一步提高其pH,可促进大豆蛋白球形结构的伸展,以及展开的蛋白分子链在胶液中发生结构重排,形成更为规整有序的结构,表面可交联活性基团减少。综合FT-IR、~(13)C NMR和溶胶-凝胶分析结果表明:提高pH还会促进PAE树脂的自交联反应,从而减少能与大豆蛋白反应的交联功能基团数量。大豆蛋白的球形结构伸展和PAE树脂的自交联共同作用使得胶液的黏度随pH增加而逐渐增加,胶黏剂的适用期、交联密度及耐水性能则呈现逐渐降低的趋势。综合考虑大豆胶黏剂的胶合性能、涂布性、适用期等各方面因素,PAE溶液的pH应在5.9以下,最好低于4.6。
译 名：
Effect of pH of PAE resin on the structure and properties of soybean adhesive
作 者：
SUN Zongxing;YE Renwei;JIAN Jialin;SONG Nan;LIU Ting;FU Qingyu;GAO Zhenhua;Material Science and Engineering College, Northeast Forestry University;
关键词：
soybean adhesive;;polyamidoamine-epichlorohydrin resin;;pH;;crosslinking characteristic;;bonding property
摘 要：
Soybean adhesives prepared from defatted soybean meal flour and polyamidoamine-epichlorohydrin(PAE) resin as both crosslinker and disperser are commonly applied for wood composites due to its good bonding strength, acceptable water resistance, non-formaldehyde addition and renewability of soybean meal. Since the crosslinking reaction of PAE resin, the dispersion and solubility of soybean protein and bonding property of soybean adhesives are related to the pH of adhesive liquid, various pH of PAE solution lead to pH changes of resultant adhesives accordingly, which may importantly affect bonding property of soybean adhesives. This study investigated the effects of pH of PAE solution on the structure and properties of soybean adhesives based on the characterizations by the Fourier infrared analysis(FT-IR), X-ray diffraction(XRD), sol-gel tests, solid-state ~(13)C nuclear magnetic resonance(~(13)C NMR), bonding properties and physical properties of soybean adhesives. The test results indicated that the pH had important effects on the secondary structure of the soybean protein, crystallinity, crosslinking characteristic, viscosity, pot life and water resistance of soybean adhesives. Plywood evaluation indicated that the pH of PAE solution had no significant effects on the dry-state bonding property while the increase of its pH gradually decreased the water resistance. All evaluated soybean adhesives with various pH met the requirements for type-II grade of plywood, showing that the wet strengths after soaking in 63 ℃ water for 3 h were higher than the required values. However, their wet strength after 28 h boiling-dry-boiling treatment was lower than the required value(0.70 MPa) for the engineering wood flooring, the viscosity of adhesive increased significantly, and their pot lives shortened gradually when the pH of PAE solution was more than 5.9. The results from the FT-IR and XRD analyses confirmed that, after the pH reached 4.6, the continuous increase of pH of PAE solution would lead to the unfolding of globular structure of soybean protein, and the unfolded protein chain immediately rearranged to form more order structures that decreased the crosslinkable sites on protein. Meanwhile, the results from the FT-IR analysis, ~(13)C NMR analysis and sol-gel test evidenced that the increase of the pH of PAE solution promoted the self-crosslinking reaction of PAE resin, which decreased the available group content in PAE resin crosslinkable to soybean protein. These facts resulted in higher viscosity, shorter pot life, less crosslinking density and worse water resistance of soybean adhesives prepared from PAE solution with ever-increasing pH. With considerations of bonding property, spreading and pot life of soybean adhesives, the pH of PAE solution should be less than 5.9 and preferably be less than 4.6.
