柠檬酸对聚醋酸乙烯酯胶黏剂耐水性能的影响

Effects of citric acid on the water resistance of polyvinyl acetate adhesive

摘要:

聚醋酸乙烯酯乳液具有环保、可室温固化等优点,在木材胶黏剂中具有较大的应用潜力,但是耐水性能较差。本研究采用柠檬酸(CA)对聚醋酸乙烯酯进行改性,研究了柠檬酸对乳液性能的影响,旨在改善其耐水性能并用于木材工业提高其粘结性能。通过傅里叶变换红外光谱(FTIR)和X射线衍射仪(XRD)对其结构进行表征,发现CA能够与聚合物中的羟基发生反应,CA对胶黏剂的结晶度影响不大。差示扫描量热仪(DSC)和热重分析仪表明,添加CA后,提高了聚合物的耐热性能,玻璃化温度从39.39℃提高到41.5℃。经过吸水性能和接触角测试表明,随着CA添加量增大,CA为5%时,吸水率最低,接触角最大为86.91°。CA对胶合强度有较大幅度的提高,当CA加入量为5%时,胶合板的湿胶合强度达到1.22MPa,满足二类板的强度要求。

Abstract:

Polyvinyl acetate emulsion has the advantages of environmental protection and room temperature curing. It has great application potential in wood-based adhesives, but its water resistance is poor. In this study, citric acid was used to modify polyvinyl acetate, and the effect of citric acid on the performance of the emulsion was investigated, aiming to improve its water resistance and be used in the wood industry to enhance its bonding performance. The structure of the adhesive was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). It was found that CA could react with hydroxyl groups in the polymer, and CA has little effect on the crystallinity of the adhesive. Differential scanning calorimetry (DSC) and thermogravimetric analysis showed that the addition of CA improved the heat resistance of the polymer, and the glass transition temperature increased from 39.39 ℃ to 41.5 ℃ and then decreasing. The water absorption performance and contact angle tests showed that as the amount of CA added increases, the water absorption expansion rate is the lowest when CA is 5%, and the maximum contact angle is 86.91 °. CA significantly improves the bonding strength. When the amount of CA added is 5%, the wet bonding strength of plywood reaches 1.22 MPa, meeting the strength requirements of Class II plywood.