水可分散型异氰酸酯固化剂的研究进展

以水可分散型异氰酸酯固化剂为主体,介绍了2种不同类型的异氰酸酯固化剂,主要介绍了异氰酸酯固化剂的亲水改性方法和封闭剂的类型,概括了水性异氰酸酯固化剂的性能及应用,并对其应用前景进行了展望。     

亲水型气相二氧化硅对环氧固化剂流变性能的改性研究

采用亲水型气相二氧化硅对环氧固化剂的流变性能进行了改性,研究了不同含水率亲水型气相二氧化硅在不同类型环氧固化剂中的改性效果,以及改性效果的储存稳定性,其结果表明亲水型气相二氧化硅对不同类型的环氧固化剂的流变性能改性效果不同,最优的是改性酚醛胺固化剂,其次是改性脂环胺固化剂,对聚醚胺固化剂改性效果差.亲水型气相二氧化硅对...     

水性多异氰酸酯固化剂

简要介绍固化剂功能与应用、涂料中常见的固化剂类型,列举了水性多异氰酸酯固化剂产品性能与应用。     

国内固化剂修复重金属污染土壤的研究进展

综述了土壤重金属污染来源、修复重金属污染土壤的主要方法及主要方式,并着重论述了常见的无机固化剂、有机固化剂、离子拮抗剂、复合固化剂的修复机理及修复效果。综合来看向土壤施加固化剂可以有效地吸附和固定土壤重金属,但也存在一定风险,使用不当易造成二次污染。研究发现多种固化剂联合修复较单一固化剂修复效果要更好。在使用土壤固化剂时需结合土壤类型、土壤污染物类型及污染物性质等多方面的因素来综合使用,从而达到修复重金属污染土壤最好的效果。     

改性胺固化剂对防腐涂料的影响

利用缩水甘油醚和二乙烯三胺制得端氨基环氧-胺加成物作为固化剂,采用扫描电镜探讨了不同类型固化剂对涂层乳液粒径、表观形貌的影响;利用交流阻抗技术研究了不同固化剂对涂层耐蚀性的影响。结果表明:共混封端的固化剂的乳化性能较好,乳液的平均粒径较小,其制备的涂层耐蚀性最好。     

水性环氧树脂固化剂的研究进展

水性环氧固化剂是水性环氧体系的重要组成部分,其组成和结构直接影响涂膜的物理化学性能。文中概述了水性环氧固化剂的类型及特点,总结了离子型与非离子型水性环氧固化剂的一般制备方法及优缺点,探讨了水性环氧固化剂的相容性和反应活性对固化膜的影响及其调控方法,为选择合适的固化剂和开发性能优异的水性环氧固化剂提供参考。     

单宁基胶粘剂的研究

以杨梅单宁、相思单宁或黑荆树单宁为基体材料,甲醛(F)、戊二醛、乙二醛或糠醛为固化剂,PF(酚醛树脂)为键桥增长剂,制备了不同的单宁基胶粘剂,并着重探讨了单宁、固化剂类型对单宁基胶粘剂性能的影响。研究结果表明:单宁的类型和结构会影响单宁基胶粘剂的性能,黑荆树单宁胶粘剂具有相对最高的干态胶接强度和耐沸水胶接强度;添加固化剂和键桥增长剂,可制备耐沸水性优良的单宁基胶粘剂;F是单宁基胶粘剂理想的固化剂,但不适合大规模使用,可用乙二醛替代F作为单宁基胶粘剂的固化剂。     

桩基施工泥浆固化处理新技术的应用研究

桩基工程施工废弃泥浆直接排放的污染风险较大,需要对其进行处理。因此,以某桩基工程施工废弃泥浆经过絮凝和脱水处理后的絮凝体为研究对象,开展了泥浆固化处理实验研究,以固结体的无侧限抗压强度为评价指标,主要考察了固化剂类型、固化剂掺量、泥浆絮凝体含水量、养护温度和养护时间等因素对固化处理效果的影响。结果表明：不同类型固化剂的加入均能提高固结体的无侧限抗压强度,其中新型复合固化剂GT-2的固化处理效果最好。当实验用泥浆絮凝体的含水量固定在40%时,目标桩基施工废弃泥浆固化处理的最佳实验参数为：选择固化剂类型为新型复合固化剂GT-2,固化剂的掺量为6%,养护温度为35℃,养护时间为28 d。在此实验条件下泥浆固结体的无侧限抗压强度值可以达到0.631 MPa,达到了良好的固化处理效果。现场应用结果表明,新型复合固化剂GT-2的加入能够对现场桩基施工废弃泥浆起到较好的固化效果,并且处理成本较低,具有良好的环境、经济和社会效益。     

高固体分环氧树脂涂料耐酸隆的研究

采用低分子量环氧树脂、胺类固化剂配制高固体分环氧树脂涂料。讨论了室温固化条件下环氧树脂分子量、固化剂类型、不同酸性介质对涂层耐酸性的影响。     

固体燃料的合成工艺研究

本文介绍了以硬脂酸盐类为固化剂合成固体燃料的方法，用正交试验法研究了温度、固化剂类型、固化剂用量以及硬脂与氢氧化钠溶液的配比等诸因素对固体燃料的合成工艺和对产品性能的影响。确定了制备固体燃料的最佳工艺条件和最佳配方。     

Failure of tannic acid to inhibit digestion or reduce digestibility of plant protein in gut fluids of insect herbivores

The rate of hydrolysis of the abundant foliar protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC), in enzymatically active gut fluid ofManduca sexta larvae is very rapid and is unaffected by the presence of tannic acid, even when tannic acid is present in the incubation mixture in amounts in excess of the amount of RuBPC. When this protein is dissolved in the denatured gut fluids ofM. sexta larvae orSchistocerca gregaria nymphs, large amounts of tannic acid must be added to bring about the precipitation of significant quantities of protein. The ability of insect gut fluid to prevent the formation of insoluble tannin-protein complexes is due to the presence of surfactants. On the basis of our results and a review of the findings of other investigators, we argue that there is no evidence that tannins reduce the nutritional value of an insect's food by inhibiting digestive enzymes or by reducing the digestibility of ingested proteins and, further, that the failure of tannins to interfere with digestion is readily explained on the basis of well-documented characteristics of the digestive systems of herbivorous insects. In challenging the currently popular notion that tannins are digestibility-reducing substances, we do not challenge the general utility of either the apparency theory or resource availability theory of plant defense. In debating the merits of these two analyses of plant-herbivore interactions, however, the demise of tannins as all-purpose, dose-dependent, digestibility-reducing defensive substances must be taken into account.     

机制砂岩性与级配对混凝土抗硫酸盐侵蚀性能的影响

为了探究不同岩性、不同级配机制砂对混凝土性能的影响,对三种不同岩性机制砂混凝土及天然河砂混凝土的工作性和抗压强度进行研究。此外,对比分析了四种混凝土在干湿循环制度下的抗硫酸盐侵蚀性能。结果表明,天然河砂混凝土的工作性优于机制砂混凝土,钙质机制砂混凝土的工作性略好于硅质机制砂混凝土。机制砂混凝土的抗压强度优于天然河砂混凝土,在硫酸盐侵蚀循环作用下的力学性能变化趋势与天然河砂混凝土基本一致。在相同级配条件下,机制砂混凝土的抗蚀系数高于天然河砂混凝土;机制砂岩性并不会对混凝土抗硫酸盐侵蚀性能带来负面影响。级配良好的机制砂可以增强混凝土抗压强度和抗硫酸盐侵蚀性能。     

Functional properties of proteins in foods

The measurement of functionality of protein food ingredients has developed somewhat haphazardly, probably due to the wide range of proteins used as ingredients and the diversity of foods. Studies of the physiochemical properties of proteins should enable prediction of a proteins response to process environments and prove more fruitful than many of the empirical measurements of functionality. The effects of pH, salt type and concentration on the phase behaviour of the oilseed globulin and arachin, demonstrates the complexity of protein solubility and the inadequacies of simple tests that have arisen. Studies of the effects of salts and conditioning on meat fibres, coupled with measurement of the location of water in pellets from water holding tests enable the latter to be applied with increased confidence. Comparison of the endothermic transitions observed on heating with the development of storage and loss moduli allow the contributions of domains of skeletal muscle myosin to gel structure to be investigated.     

Aggregation pheromone system of adult gregarious desert locust schistocerca gregaria (forskal)

Six electrophysiologically active aromatic compounds, viz., anisole, benzaldehyde, veratrole, guaiacol, phenylacetonitrile, and phenol, were identified in the volatiles of older-adult male desert locust. Young adults and females of all age groups produced none or only trace quantities of these compounds. Comparison of the aggregation responses of young and older adults to the crude, older-adult, volatile extract and different synthetic blends of the six compounds showed that the aggregation pheromone system of the adult gregarious locust consists of phenylacetonitrile, guaiacol, phenol, and benzaldehyde. Like the crude volatile extract of older males, neither the synthetic blend of the six compounds nor the adult pheromone blend evoked any significant aggregation responses from nymphs. These results confirm our previous report of sexual differentiation in the production of adult aggregation pheromone in the desert locust and of the evidence of two distinct aggregation pheromone systems in the two stages of the insect.     

Molecular mechanics modelling of interfacial energy and flexibility on cellulose

Molecular mechanics modelling is used to calculate the energies of interaction, hence the molecular level energy of adhesion at the interface with crystalline cellulose I of three different photopolymerizable primers and of a polyester varnish at the interface with the primer/cellulose assembly. The energy of interactions for just one of the primers with the statistically most common conformation of amorphous cellulose has also been obtained for comparison. Experimental results of adhesion by a standard peel test and by thermomechanical analysis, in which the effect of viscoelastic energy dissipation by crack tip propagation has been respectively minimized or is not present, hence in which the energy of interfacial interaction is nothing else but the work of adhesion, correlated well with the energies of interaction calculated by molecular mechanics. An equation correlating the energy of interaction at each finish/cellulose interface with the deflection derived by thermomechanical analysis, and with the number of internal bond rotational degrees of freedom as well as the degree of networking of the finish, has been derived and is presented. A relationship between the intrinsic fracture energy Go and the molecular mechanics-derived energy of interaction at the interface equating this to the square of the work of adhesion is obtained and is presented.     

Distribution of birch (Betula SPP.), willow (Salix SPP.), and poplar (Populus SPP.) secondary metabolites and their potential role as chemical defense against herbivores

Isoprenoids and phenolics, major metabolites of important browse species, are reviewed in regard to concentrations, distribution within tissues, and between species. Seasonal variation of specific substances and changes with age of the plant are also considered. The distribution of substances may affect food selection and feeding behavior of animals. Wild mammalian herbivores tend to avoid plant parts rich in these substances, in spite of high nutritional content of the plant tissue. Possible mechanisms for defense by plants against depredation by mammalian herbivores are discussed within the framework of the plants' biochemistry.     

Sr改性Cu催化剂的果糖加氢制备甘露醇性能

使用共沉淀法制备负载Cu催化剂。通过添加碱土金属Sr，对Cu催化剂进行了改性，以提高Cu催化剂在果糖加氢制备甘露醇过程中的活性和选择性。采用ICP-MS、TEM、XRD、H₂-TPR、XPS和CO₂-TPD等对所制备的催化剂进行了系统表征。结果表明：Sr的添加能增大催化剂的比表面积，促进活性组分Cu的分散，从而提高了催化剂的活性，并且增加了催化剂的碱性，使果糖优先形成β-呋喃糖中间体，从而提高了甘露醇的选择性。在果糖浓度为1.1 mol·L^-1、催化剂用量为反应物质量的6%、反应温度为373 K、反应氢压为4.0 MPa、Cu/Sr原子比为7∶1的反应条件下，果糖转化率为99%，甘露醇的选择性为79%。催化剂循环使用了20次，其催化稳定性基本保持不变。     

Measured kinetics of the acid-catalysed hydrolysis of sugar cane bagasse to produce xylose

Experimental trials of the water hydrolysis of bagasse to produce xylose, arabinose and glucose were conducted using a temperature-controlled microwave digester. The experimental variables were temperature, ratio of water mass to bagasse mass, type of bagasse material and reaction time. The pH of the liquid and concentration of dissolved xylose, arabinose and glucose were measured at the completion of each trial. Kinetic modelling of the global rates of formation of monosaccharide products was performed using schemes based on earlier researchers’ models of acid hydrolysis using mineral acids. For the most plentiful product, xylose, the most accurate kinetic model of the global reactions was determined to be two parallel pathways for hydrolysis of xylan to xylose followed by a single pathway for xylose decomposition. The calculated activation energies of the reactions were within the range reported by other researchers for the hydrolysis of a range of lignocellulosic materials using mineral acids.     

接触式机械密封界面泄漏机理研究的关键科学问题

密封界面的泄漏机理是机械密封研究与应用的焦点问题之一,涉及泄漏通道表征、粗糙表面的接触力学模型、界面微观形貌变化以及介质流体在泄漏通道中的流动阻力等问题。回顾了近几十年国内外接触式机械密封泄漏通道模型的研究,深入分析了G-W模型、M-B模型和Persson模型3种粗糙表面接触力学模型的贡献和存在的问题,提出了一种基于逾渗理论的泄漏通道新模型;探讨了密封界面的分形参数、泄漏通道的流动阻力以及密封界面的有限尺寸效应对泄漏特性的影响,指出孔隙连通贯穿界面和流体流经贯穿通道的流动阻力小是密封界面产生泄漏的成因,以及泄漏通道的形成和泄漏通道内的流体流动特性是泄漏机理研究的主要方向。