玄武岩纤维改性大豆蛋白胶黏剂性能及胶合机理

为提高大豆蛋白胶黏剂的胶合强度,开发环境友好型木材用生物质胶黏剂,采用玄武岩纤维(basalt fiber,BF)作为增强改性剂,成功制备了胶接性能优良的玄武岩纤维改性大豆蛋白胶黏剂(basalt fiber/soybean protein isolate adhesive,BF/SPIA),并对BF/SPI的胶接强度、流变特性、化学基团及形态结构进行了分析。研究结果表明:随着玄武岩纤维用量的逐步提高,改性大豆蛋白胶黏剂的力学强度呈先增加后下降的趋势。当BF质量分数为5%时,BF/SPIA干、湿状胶接强度分别达2.15和0.92 MPa。流变特性测试结果表明BF/SPI胶黏剂的剪切模量有所增加;傅里叶红外光谱(fourier infrared spectrum,FTIR)显示出改性大豆蛋白胶黏剂中亲水基团降低,Si—O键特征峰明显,BF与大豆蛋白分子间相互作用,形成新的复合结构;扫描电镜(scanning electron microscope,SEM)图谱印证了BF与SPAI两相体系融合性良好,且固化胶接界面较为致密。中试试验结果进一步表明玄武岩纤维改性大豆蛋白胶黏剂具有良好的稳定性,其湿状胶接强度可高达1.05 MPa,木材压缩率仅14.92%,实用性较强。该研究可为改性大豆蛋白胶黏剂的工业化应用及推动环保木材胶黏剂的应用进程提供理论参考。

Performance and bonding mechanism of soy protein adhesives modified by basalt fiber

Abstract: Nowadays, the "three-formaldehyde" adhesives are faced with more and more outstanding problem since resources shortage and the threat of serious environmental pollution to human beings are aggravating. In order to reduce usage of formaldehyde adhesives in plywood, the soybean adhesive is gaining increasing attention because of its reproducibility and pollution-free feature. However, chemical modified soybean adhesive can not meet the demands of the woody adhesive industry market because of lower adhesive strength and water resistance, and pollution property. In this study, in order to enhance utilization value of soybean protein and develop environment-friendly woody adhesive, a new approach for improving the adhesion performance of modified soybean protein adhesive has been studied. The modified soybean protein adhesive was prepared as a new kind of waterproof adhesive to make plywood. For modified adhesive, soybean protein isolate (SPI) was used as main raw bonding material, and water resistance and bonding strength of modified soybean protein adhesive were enhanced by adding basalt fiber (BF). Hence, mechanical properties, rheological properties and morphological structure of the modified soybean adhesives were analyzed to determine the water resistance, and at the same time, relevant bonding mechanism was discussed by Fourier transform infrared spectrometer (FTIR) and Differential scanning calorimetry (DSC). The results revealed the bonding strength with drying and wetting has been increasing with the gradual improvement of BF dosage. During the test, the measured drying bonding strength value of BF/SPI-5% (the mass of BF was 5% of that of SPI) was 2.15 MPa, while the wetting bonding strength was 0.92 MPa. The measurement of wetting bonding strength referred to the GB/T 17657-2013 and the wetting bonding strength could be as high as 1.05 MPa, while the wood compression rate was only 14.92%, which was confirmed by the pilot-scale experimental research, and the results further verify the BF/SPI modification adhesive has a good stability and practicability too. It was found that the shear elasticity was increased according to the result of the rheological behavior. FTIR analysis showed that a new compound structure could be formed with the interaction between BF and soybean protein molecule, and this consequence was confirmed by DSC. And adding small amount of BF led to relatively stable continuous phase in the soybean protein adhesive matrix, as shown in scanning electron microscope (SEM) images. Experimental results confirm that lower dosage BF is beneficial for increasing tack-up reticular structure, which can block up water immersion effectively, and thus greatly improve the bonding strength. In addition, the synthesis process of modified soybean protein adhesive does not need higher temperature. What is more, it has small energy consumption, no waste water, no waste gas, and no waste residue discharge, which are perfectly in accordance with national industrial policy. In conclusion, the research can provide a reference for BF/SPIA application in plywood industry and scientific basis for accelerating the development of environment-friendly woody adhesive.