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.     

Preparation of a New Type of Polyamidoamine and Its Application for Soy Flour-Based Adhesives

The most commonly used curing agents for soy-based adhesives are polyamines, which have the problem of low solid content and/or high viscosity. To overcome this problem, a new type of polyamidoamine (PADA) resin was synthesized and applied to soy flour-based adhesives to improve their water resistance. The PADA solution obtained had a high solid content of 50 wt% and low viscosity of 270 cP. The optimum weight ratio of soy flour/PADA/maleic anhydride to prepare adhesive was 40/7/1.68. The wet strength of plywood prepared at the optimum weight ratio was 0.82 MPa, which meant the plywood could be used as type II plywood according to the Chinese National Standard GB/T 9846.7-2004. The results of water-insoluble solid content measurement and SEM observation demonstrated that cured soy flour–PADA–maleic anhydride adhesive had a 16 % greater water-insoluble solid content than soy flour–NaOH adhesive. The cross-linking network formed by the reactions of PADA and MA would increase the water-insoluble solid contents and improve water resistance of cured soy flour-based adhesives.     

高强度耐热环氧胶带的研制

所研制的是耐热性环氧胶，通过选择基材（包括处理方法）、固化促进剂和耐热性改性剂等，并改进胶带的制法，得到了粘接强度高、耐热性好、使用期长的环氧胶带，选择好的促进剂，不但可以提高固化速度，还可以使胶带具有较长的适用期，先溶解双氰双胺，再将其它组合加入到胶液，得到的胶带的性能较好。     

Preparation and Characterization of High Mechanical Strength Chitosan/Oxidized Tannic Acid Composite Film with Schiff Base and Hydrogen Bond Crosslinking

Chitosan-based composite films with good biodegradability, biocompatibility, and sustainability are extensively employed in the field of food packaging. In this study, novel chitosan/tannic acid (CTA) and chitosan/oxidized tannic acid (COTA) composite films with excellent mechanical and antibacterial properties were prepared using a tape casting method. The results showed that, when 20% tannic acid (TA) was added, the tensile strength of the CTA composite film was 80.7 MPa, which was 89.4% higher than that of the pure chitosan (CS) film. TA was oxidized to oxidized tannic acid (OTA) with laccase, and the phenolic hydroxyl groups were oxidized to an o-quinone structure. With the addition of OTA, a Schiff base reaction between the OTA and CS occurred, and a dual network structure consisting of a chemical bond and hydrogen bond was constructed, which further improved the mechanical properties. The tensile strength of 3% COTA composite film was increased by 97.2% compared to that of pure CS film. Furthermore, these CTA films with significant antibacterial effects against Escherichia coli (E. coli) are likely to find uses in food packaging applications.     

环氧豆油/酚醛交联树脂的制备和抗吸水机理研究

通过苯酚羟基醚化和环氧豆油(ESO)扩链聚合制备了环氧豆油/酚醛(PR)交联树脂,采用扫描电子显微镜和热分析分别研究了醚化和扩链对改性酚醛树脂微观形貌及抗吸水性的影响.ESO扩链聚合物与酚醛树脂不相容,通过醚化反应可改善相容性并接枝形成软硬链段交联网络.ESO与酚醛交联聚合能够增强树脂的抗吸水性,由该交联树脂制得的纸层...     

大豆分离蛋白纸张表面施胶剂的制备及性能

以大豆分离蛋白(SPI)为原料、烯基琥珀酸酐(ASA)为疏水改性剂，控制ASA与SPI伯氨基的摩尔比合成四种不同酰化度的疏水大豆分离蛋白ASAn-SPI (下标n表示摩尔比，n=0.5，1，1.5和2)。通过伯氨基含量、FT-IR、UV-vis、荧光光谱、疏水指数等测定方法对ASAn-SPI的结构和性能进行表征。结果表明：长链疏水基团成功引入到SPI骨架上，ASAn-SPI的酰化度和疏水指数随着n的增加而增大，当n达到1.5后趋于稳定。ASA1.5-SPI的施胶量为0.77 g/m2时，施胶纸的初始水接触角可达132?，水滴保留时间可达53 min。XPS和SEM分析证实ASA1.5-SPI在纸纤维表面形成一层粗糙的疏水薄膜。此外，纸张力学性能测试表明，ASA1.5-SPI施胶纸的抗张强度由未施胶纸的0.6 kN/m提升至0.67 kN/m。     

Contemporary Issues in Protein Requirements and Consumption for Resistance Trained Athletes

In recent years an explosion of research papers concerning protein consumption has been published. The need to consolidate this information has become critical from both practical and future research standpoints. For this reason, the following paper presents an in depth analysis of contemporary issues in protein requirements and consumption for resistance trained athletes. Specifically, the paper covers: 1.) protein requirements for resistance trained athletes; 2.) the effect of the digestion rate of protein on muscular protein balance; 3.) the optimal timing of protein intake relative to exercise; 4.) the optimal pattern of protein ingestion, relative to how an individual should consume their protein throughout a 24 hour period, and what sources are utilized during this time frame; 5.) protein composition and its interaction with measures of protein balance and strength performance; 6.) the combination of protein and carbohydrates on plasma insulin levels and protein balance; 7.) the efficacy of protein supplements and whole food protein sources. Our goal is to provide the reader with practical information in optimizing protein intake as well as for provision of sound advice to their clients. Finally, special care was taken to provide future research implications.     

SiO2-Al2O3-MgO系高强玻璃纤维耐酸性能研究

采用高温熔融法制备了SiO2-Al2O3-MgO系统的S级高强玻璃纤维,研究了不同玻璃组分对玻璃耐酸性能的影响,利用扫描电镜(SEM)、红外光谱(IR)和核磁共振(NMR)等手段分析了酸侵蚀前后纤维的表面形貌和微观结构,进而分析了S级高强玻璃纤维在酸腐蚀环境下的破坏机理.结果表明:S高强玻璃的结构主要由硅氧四面体[SiO4]和铝氧四面体[AlO4]等构成,随着酸蚀的进行,玻璃网络结构被破坏,Si-O-Si断裂形成Si-OH键并形成凝胶附着在纤维表面;而铝氧多面体中Al-O键断裂,Al3+逐渐从玻璃结构中被置换出来,导致玻璃网络中Al3+浓度大大降低;高强系列玻璃的耐酸性能与玻璃表面的化学组成以及玻璃内部的微观结构关系密切.致密的玻璃网络结构有利于抑制H+对玻璃结构破坏,抑制阳离子与H+的置换作用;此外引入离子场强高的Ti4+,由于"积聚"作用而使玻璃结构致密,提高玻璃纤维的耐酸性.     

Different Effects of Water and Glycerol on Morphology and Properties of Poly(lactic acid)/Soy Protein Concentrate Blends

When containing extra water, soy protein concentrate (SPC) can behave like a plastic melt rather than particulate filler in blending process. In this study, blends of formulated SPC and poly(lactic acid) (PLA) were prepared. The effects of glycerol and water added to SPC on phase morphology, rheological, thermal, thermal‐dynamic, and mechanical properties of the blends were investigated. The results demonstrated that water was more effective in gelating SPC and transforming it into a plastic than glycerol. With extra water added, SPC in the resulting blend existed as stretched threads with certain degree of interconnectivity between the threads. In contrast, with only glycerol added, SPC existed as large SPC agglomerates. Consequently, the blends made from extra water‐containing SPC exhibited higher mechanical, thermal‐dynamic, and rheological properties.

     

高压绕线电机用水电阻调速技术在选煤厂水泵上的使用及节能

介绍水电阻调速器的工作原理,从理论上分析了水电阻调速器应用于水泵类负载时的节能原理,并与其它调速方式进行了比较。     

A Dual Physical Cross-Linking Strategy to Construct Tough Hydrogels with High Strength,Excellent Fatigue Resistance,and Stretching-Induced Strengthening Effect

Hydrogels with excellent stiffness, toughness, anti-fatigue, and self-recovery properties are regarded as promising water-containing materials. In this work, a dual physically cross-linked (DPC) sodium alginate (SA)/poly[acrylamide (AAm)-acrylic acid (AAc)-octadecyl methacrylate (OMA)]-Fe³⁺ hydrogel is reported, which is constructed by hydrophobic association (HA) and ionic coordination (IC). The optimal DPC hydrogel demonstrates excellent mechanical performance: tensile modulus of 0.65 MPa, tensile strength of 3.31 MPa, elongation at break of 1547%, and toughness of 27.8 MJ m^–3. SA/P(AAm-AAc-OMA)-Fe³⁺ DPC hydrogels also exhibit prominent anti-fatigue and self-recovery performance (99.1–109.7% modulus recovery and 90.4–108.9% dissipated energy recovery after resting for 5 min without additional stimuli at ambient temperature) through the reconstruction of reversible physical cross-linking. Some of the SA/P(AAm-AAc-OMA)-Fe³⁺ DPC hydrogels even exhibit a stretching-induced strengthening effect, which is similar to the performance of muscle—“the more training, the more strength.” Hence, the combination of HA and IC will provide an effective approach to design DPC hydrogels with desirable mechanical performances and a longer service life for wider applications of soft materials.     

高浓度砷氟硫酸废水处理装置的设计与运行

针对锌、铜冶炼烟气制酸烟气净化洗涤水酸性强,且含有大量的锌、铜、铅、镉、砷、汞等污染物,采用石灰中和再硫化处理的三级中和工艺,取得了较好的效果.介绍了工艺流程、控制指标和处理效果,实现了长期稳定运行、达标排放,处理后的废水回收利用的目标.