改性无醛大豆基胶粘剂的研究

采用表面活性剂(A)改性豆粕的方法制备了无甲醛大豆基胶粘剂。研究了A的用量、热压时间和热压温度对大豆基胶粘剂胶合性能的影响,采用差示扫描量热(DSC)仪对大豆基胶粘剂的热性能进行了研究。研究结果表明,当w(A)=2.5%(相对于豆粕而言)、热压时间为15min和热压温度为140～160℃时,大豆基胶粘剂表现出最佳的胶合强度;其主要的热反应在160℃以下完成。     

大豆基胶粘剂的研究进展

介绍了大豆蛋白的结构与组成,综述了近年来国内外大豆基胶粘剂的发展概况和改性进展,提出了研发中存在的问题以及发展大豆基胶粘剂的意义。     

大豆基生物质胶粘剂研究进展

随着人们环保意识的增强,开发研究木材加工用环保型胶粘剂已越来越受到重视。介绍了一种环境友好型胶粘剂(大豆基木材胶粘剂)近年来在国内外的研究概况,提出了该胶粘剂今后的发展方向,为大豆基生物质木材胶粘剂的后续研究和应用创造了一定的理论条件和经验基础。     

大豆基木材胶粘剂的研究进展

综述了大豆基木材胶粘剂的应用原理、历史和研究进展,重点介绍了豆胶的新型交联体系,指出了豆胶存在的问题.     

大豆基生物胶环境友好

20世纪40～60年代,大豆基木材胶粘剂曾经在美国西海岸胶合板市场盛极一时,但因合成树脂胶粘剂的出现,使其逐渐退出市场。随着人们环保意识的增强,环保型胶粘剂备受青睐,大豆基木材胶粘剂又东山再起,渐受重视。在第二届中国发明家论坛会上,大豆基无甲醛胶粘剂受到关注,这种完全无毒的木材胶粘剂有望取代目前普遍使用的脲醛胶,将对我国木材胶粘剂行业产生巨大影响,真正破解人造板甲醛污染的难题。大豆基无甲醛胶粘剂是以可再生的大豆豆粕为原料,经过提取蛋白质并使其改性,在添加一定的助剂后,再经特殊生物工程技术处理,获得的胶粘剂可达到预定的粘接强度,     

木材工业用环保型耐水性大豆基蛋白质胶粘剂

<正>由福建农林大学材料工程学院研发的木材工业用环保型耐水性大豆基蛋白质胶粘剂,日前经省级专家鉴定,证明其已达到国际同类产品的先进水平。福建尤溪三林木业有限公司已决定投资兴建年产5 000 t的环保型耐水性大豆基蛋白质胶粘剂生产线。     

本期特约专栏主持人——许戈文

主持人语:水性聚氨酯胶粘剂是水性胶粘剂中的重要一类,具有聚氨酯材料"可裁剪性"的特点,继承了聚氨酯材料的全部优良性能,应用面也在迅速扩大。当今水性聚氨酯胶粘剂研究的重中之重是对其结构与性能关系的研究。本专题结合结构表征,重点讨论了聚氨酯结构中酯基含量和聚酯中侧基含量对胶膜力学性能的影响,以及磺酸型水性聚氨酯胶粘剂中催化剂的选择对胶膜力学性能的影响。为水性聚氨酯胶粘剂软段和亲水链段的研     

大豆基生物质胶粘剂

<正>将大豆榨油后残留的豆粕制成生物质胶粘剂,并用于人造板的制造,可帮助家具建材"抛弃"甲醛。上海理工大学研发的"大豆基胶粘剂技术及其在中密度纤维板上的应用"已成为市科委重点攻关项目。     

木素基酚醛树脂胶粘剂的应用性能研究

采用热化学酚化技术活化木素得到木素酚化产物,以酚化产物代替苯酚制备低成本的木素酚化液基酚醛树脂(LPF)胶粘剂。采用红外光谱(FT-IR)对LPF和传统PF的结构进行了表征,通过对比试验分析了LPF的应用性能,并对LPF胶粘剂应用性能产生的机理作了一定的探讨。结果表明:酚化后的木素参与了LPF胶粘剂的合成,并具有新的不同取代基的苯环结构;LPF胶粘剂与传统酚醛树脂(PF)胶粘剂具有相似的应用性能,前者比后者具有更低的游离酚(醛)含量(游离酚<0.12%,游离醛<0.08%)、更快的干燥速率和更低的施胶量(固含量29%时施胶量为297g/m2);另外,LPF胶粘剂具有优异的胶合性能(达到了Ⅰ类胶合板的标准要求)和储存稳定性,完全满足高性能环保型胶粘剂的使用要求。     

氟硅化β-环糊精改性异氰酸酯胶粘剂的制备与性能研究

对β-环糊精进行端基氟硅化处理,再与异氰酸酯相交联制备改性胶粘剂。对该胶粘剂进行了分析与表征,并针对不同氟硅化β-环糊精用量对胶粘剂的性能影响进行探讨。研究结果表明:氟硅化β-环糊精用量的增大,有利于胶粘剂黏度的增大和胶膜表面张力、拉伸强度、弹性模量以及铅笔硬度的提升。     

Shear strength and water resistance of modified soy protein adhesives

Soy protein polymers recently have been considered as alternatives to petroleum polymers to ease environmental pollution. The use of soy proteins as adhesives for plywood has been limited because of their low water resistance. The objective of this research was to test the water resistance of adhesives containing modified soy proteins in walnut, maple, poplar, and pine plywood applications. Gluing strength and water resistance of wood were tested by using two ASTM standard methods. Glues with modified soy proteins had stronger bond strength than those containing unmodified soy proteins. Plywood made with glue containing urea-modified proteins had higher water resistance than those bonded with glues containing alkali-modified and heat-treated proteins. After three 48-h cycles of water-soaking, followed by 48 h of air-drying, no delamination was observed for either walnut or pine specimens glued with the urea-modified soy protein adhesives. Gluing strength for wood species with smooth and oriented surface structure was lower than for those with rough, randomly oriented, surface structures. Wood species with greater expansion of dimensions during water-soaking had a higher delamination rate than those showing less expansion.     

Soy-based adhesives for wood-bonding – a review

Over recent years, the interest in bio-adhesives, including soy-based adhesives, has increased rapidly. Among natural renewable resources suitable for industrial use, soy is a reasonable choice due to its high production volume and the small use of soy meal-based products for human food consumption. Soy flour can be an ideal raw material for the manufacturing of wood adhesives due to its low cost, high protein content and easy processing. There are also more concentrated forms of soy proteins, i.e. concentrates and isolates, which are also suitable raw materials for adhesive production except that their prices are higher. Extensive research has been carried out on improving the cohesive properties, especially water resistance, of soy-based adhesives. However, there is insufficient experimental data available for understanding the influences of modification methods on the structure of soy proteins and therefore for understanding the influences of structural changes on the adhesion. In this paper, some experimental techniques are proposed to be used for analysing soy-based adhesives to enable better understanding of those factors and improve future development. This review of soy-based adhesives is made with the focus on soy proteins’ chemical composition, soy protein product types (raw materials for adhesive production), modification methods for improving the adhesive properties of soy-based adhesives, and commercial soy-based adhesives.     

Soy proteins as plywood adhesives: formulation and characterization

Soybean proteins have great potential as bio-based adhesives. The objectives of our study were to develop and characterize formaldehyde-free soybean wood adhesives with improved water resistance. Second-order response surface regression models were used to determine the effects of soy protein isolate concentration, sodium chloride, and pH on adhesive performance. All three variables affected both dry and wet strengths of bonded wood specimens. The optimum operation zone for preparing adhesives with improved water resistance is at a protein concentration of 28% and pH 5.5. Sodium chloride had negative effects on adhesive performance. Soy adhesives modified with 0.5% sodium chloride had dry strength, wet strength, and boiling strength of bonded specimens comparable to nonmodified soy adhesives. Rheological study indicated that soy adhesives exhibited shear thinning behavior. Adhesives modified with sodium chloride showed significantly lower viscosity and yield stress. Sodium chloride-modified soy adhesives formed small aggregates and had low storage moduli, suggesting reduced protein–protein interactions. These formaldehyde-free soy adhesives showed strong potential as alternatives to commercial formaldehyde-based wood adhesives.     

Physicochemical Properties of Soy Protein Adhesives Obtained by In Situ Sodium Bisulfite Modification During Acid Precipitation

Successful industrial applications of soy protein adhesives require high adhesion strength and low viscosity at high solid protein concentration. This study examined the effects of β-conglycinin (7S) and glycinin (11S) ratios on the physicochemical properties of soy protein adhesives. Soy protein adhesives with various 7S/11S ratios were extracted from soy flour slurry modified with sodium bisulfite using the acid precipitation method, which is based on the different solubilities of 7S and 11S globulins. Seven glycinin-rich soy protein fractions and six β-conglycinin-rich soy protein fractions were obtained. The external morphology of the samples changed from the viscous cohesive phase to the clay-like phase without cohesiveness. The viscous cohesive samples had good flowability and good water resistance with a wet adhesion strength of 2.0–2.8 MPa. They were stable for up to several months without phase separation at room temperature. Based on the results, we suggest that proper protein–protein interaction, hydration capacity (glycinin-rich soy protein fractions), and certain ratios of 7S and 11S (β-conglycinin rich soy protein fractions) in the soy protein sample are crucial to continuous protein phase formation. Hydrogen bonding, electrostatic forces, and hydrophobic interactions are involved in maintaining the protein viscous cohesive network, whereas disulfide bonds do not exert significant effects. This study describes a new way to investigate viscous cohesive soy protein systems with high solid protein content, thus alleviating the disadvantages of traditional methods for studying the adhesive properties of soy protein isolates, which tend to have poor water resistance, low solid contents, and short storage life.     

Adhesion properties of soy protein adhesives enhanced by biomass lignin

Soy protein adhesives have great potential as sustainable eco-friendly adhesives. However, low adhesion under wet conditions hinders its applications. The objective of this research was to enhance the water resistance of soy protein adhesives. The focus of this research was to understand the effect of protein to lignin ratio and lignin particle size i.e. large (35.66 μm), medium (19.13 μm), and small (10.26 μm) on the adhesion performance of soy protein adhesives as well as to characterize its rheological and thermal properties. Results showed that the lignin particle size and the protein to lignin ratio greatly affected the adhesion performance of soy protein adhesives. The addition of lignin slightly increased the viscosity, spreadability, and thermostability of soy protein adhesives. The wet strength of soy protein adhesives increased as lignin particle size decreased. Soy protein mixed with small size lignin at a protein to lignin ratio of 10:2 (w/w) at 12% concentration presented the lowest contact angle and the highest wet adhesion strength of 4.66 MPa., which is 53.3% higher than that of 10% pure soy protein adhesive. The improvements in adhesion performance and physicochemical properties of soy protein adhesives by lignin were ascribed to the interactions between protein and lignin. Lignin with smaller particle size increased the wet shear strength of soy protein adhesives because a larger surface area of lignin was available to interact with the protein.     

High temperature performance of soy-based adhesives

We studied the high temperature performance of soy meal processed to different protein concentrations (flour, concentrate, and isolate), as well as formulated soy-based adhesives, and commercial nonsoy adhesives for comparison. No thermal transitions were seen in phenol-resorcinol-formaldehyde (PRF) or soy-phenol-formaldehyde (SoyPF) or in as-received soy flour adhesive during differential scanning calorimetry scans heating at 10?°C/min between 35 and 235?°C. Heat flow rates decreased in the order soy flour (as received)?>?SoyPF?>?PRF?>?emulsion polymer isocyanate (EPI). In thermogravimetric analysis (TGA) scans from 110 to 300?°C at 2?°C/min, total weight loss decreased in the order soy flour (as-received)>SoyPF?>?PRF?>?casein?>?maple?>?EPI. For bio-based materials, the total weight loss (TGA) decreased in the order soy flour (as-received) > concentrate, casein?>?isolate. Dynamic mechanical analysis from 35 to 235?°C at 5?°C/min of two veneers bonded by cured adhesive showed 30–40% decline in storage modulus for maple compared to 45–55% for the adhesive made from soy flour in water (Soy Flour) and 70–80% for a commercial poly(vinyl acetate) modified for heat resistance. DMA on glass fiber mats showed thermal softening temperatures increasing in the order Soy Flour?<?casein?<?isolate?<?concentrate. We suggest that the low molecular weight carbohydrates plasticize the flour product. When soy-based adhesives were tested in real bondlines in DMA and creep tests in shear, they showed less decrease in storage modulus than the glass fiber-supported specimens. This suggests that interaction with the wood substrate improved the heat resistance property of the adhesive. Average hot shear strengths (ASTM D7247) were 4.6 and 3.1?MPa for SoyPF and Soy Flour compared to 4.7 and 0.8?MPa for PRF and EPI and 4.7 for solid maple. As a whole, these data suggest that despite indications of heat sensitivity when tested neat, soy-based adhesives are likely to pass the heat resistance criterion required for structural adhesives.     

The effect of hydrolyzed soy protein isolate on the structure and biodegradability of urea–formaldehyde adhesives

The hydrolyzed soy protein isolate (HSPI) was used to partially substitute urea to synthesis modified urea–formaldehyde (UF) adhesives via copolymerization process, in order to reduce the dependency on petroleum-based chemicals and mitigate possible environmental pollution. The soy protein isolate (SPI), HSPI, and modified UF adhesives were characterized by attenuated total reflection Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (¹H NMR), and thermo-gravimetric analysis (TGA). The bonding strength, adhesive properties, biodegradability, and micrographs of the UF and HSPI-modified UF after degradation were also measured. The results show that the SPI native structure is unfolded during the treatment with sodium hydroxide. The thermal stability of HSPI is better than SPI. HSPI can incorporate into the structure of cured UF adhesives with three different feeding methods. And the best bonding strength of modified UF adhesives is 1.31?MPa when HSPI is added at the first step. The formaldehyde emission of modified UF adhesives is lower compared with UF. The earlier the HSPI is added, the better the properties for modified UF adhesives can be obtained. The degradation rate of modified UF adhesives improved nearly two times compared to the UF after six months of degradation in biologically active soil. There are microorganisms adhering to the surface of modified UF from the SEM micrographs.     

Correlation between Physical Properties and Shear Adhesion Strength of Enzymatically Modified Soy Protein-Based Adhesives

This work was to correlate physical properties with adhesion properties of soy protein‐based adhesives. By building such a correlation, the adhesion properties can be predicted by measuring physical properties of soy protein‐based adhesives. In this context, three important physical properties, viscosity, tacky force, and water resistance, were selected to correlate with adhesion strength of enzymatically modified soy protein‐based adhesives (ESP). Response surface methodology, specifically central composite design, was used with three independent variables to prepare ESP: trypsin concentration (X₁), incubation time (X₂), and glutaraldehyde (GA) concentration (X₃). The three physical properties measured were all greatly affected by our three independent variables with significance at the 95 % confidence level. The responses were then correlated with the adhesion properties of ESP. In conclusion, viscosity can be used to predict the dry adhesion strength of ESP based on the coefficient of determination (R²) of 0.8558. In addition, tacky force and water resistance can be used to represent wet adhesion strength of ESP based on R² of 0.7082 and 0.6930, respectively (P < 0.05). This work preliminarily identified the significant physical properties that can predict the adhesion strength of the ESP system crosslinked with GA, but the results need to be further confirmed by another protein modification system to give a generic conclusion.     

Development of High-Strength Soy Protein Adhesives Modified with Sodium Montmorillonite Clay

This study investigated the high strength of a soy protein adhesive system with good flowability at high protein concentration. Sodium montmorillonite (Na MMT), the most widely used silicate clay, was incorporated into viscous, cohesive soy protein adhesives at concentrations ranging from 1 to 11 % (dry basis, w/w). Hydroxyethyl cellulose was used as a suspension agent to stabilize the soy protein and nano clay to be the dispersion system. The interaction between soy protein and Na MMT was characterized by XRD, FTIR, Zeta potential and DSC. Results indicated that soy protein molecules were adsorbed on the surface of the interlayer of Na MMT through hydrogen bonding and electrostatic interaction. The soy protein/Na MMT adhesives had the intercalation structure with Na MMT contents ranging from 1 to 11 %. Adhesion strength, specifically wet adhesion strength, of soy protein adhesives at isoelectric point (pI) was significantly improved by the addition of Na MMT. It is believed that the physical cross‐linking reactions between soy protein and Na MMT mainly contribute to the improved adhesion performance of soy protein adhesives. Wet adhesion strength increased from 2.9 MPa of control soy protein adhesive to 4.3 MPa at 8 % Na MMT. An increase of pH beyond pI value resulted in decreased adhesion strength due to increased surface charges of soy protein and slightly reduced affinity of soy protein on the nano clay surface.