Additives for improving the strength,stiffness, and ductility of epoxy resins

A range of additives at 7 to 20 wt% loading can increase the stiffness and strength of crosslinked epoxy resins by up to 60%, yet the tensile specimens also fail in a ductile fashion. In additive formulations where little chemical bonding occurs between the additive and the epoxy matrix (e.g., the reaction product of 4-hydroxyacetanilide and 1,2-epoxy-3-phenoxypropane), the increase in modulus is directly related to the decrease in free volume available for segmental mobility. The increase in strength results from a combination of the increased modulus and an increased fracture energy, A ductile mode of failure occurs because the cured plastic exhibits a large increase in free volume on straining (low Poinsson's ratio). The strain-induced increase in free volume effectively takes the sample through the glass to rubber transition. In more highly reactive formulations (e.g., the reaction product of 4-hydroxyacetanilide and vinyl cyclohexene dioxide), chemical bonding effects complicate this simple free volume interpretation, but the occurrence of a ductile failure mode is again related to the free volume increase with strain.     

Weibull analysis of stiffness and strength in bulk epoxy adhesives reinforced with particles

The mechanical and statistical behaviour of aerospace structural adhesives has been investigated by performing tensile tests on moulded samples and applying Weibull theory to results. Effects of loading rate, sample size and process parameters have been studied. The experimental design method has been employed in an attempt to extend the experimental results to other combinations of parameters. Three kinds of structural adhesive have been characterised, viz, Hysol^® EA9321, Hysol^® EA9394 and Hysol^® EA9395, which are particle reinforced epoxy adhesives, all of them containing voids with statistically distributed sizes (partially dependent on bonding technique). These highly heterogeneous, but natural, microstructures explain the dispersion of measured strength and Young’s modulus of the materials. These two quantities are demonstrated not to be correlated. With these results, simple fibre bundle theory is used to evaluate the mean value and variance of the failure stress of a bonded joint loaded in tension.     

提高聚氨酯胶对玻璃钢粘接强度的研究

为了提高聚氨酯粘胶剂对玻璃钢的粘接强度,在聚氨酯胶粘剂配方中添加固化催化剂,在玻璃钢表面涂刷ＫＨ－５５０偶联剂,并且进行加速老化试验考核。结果表明,以上措施提高了粘接强度,能满足长期工作的需求。     

基于Tsai-Hill理论环氧玻璃钢管的强度分析

目前是按照工程经验对环氧玻璃钢管支撑结构进行设计,缺乏系统的理论研究。为了能有效地评估环氧玻璃钢管支撑结构的安全性,进而合理对其进行设计校核,本文首先依照纤维增强塑料性能的测试方法,对环氧玻璃钢材料进行低温力学性能测试试验;然后以应变强化型移动式真空绝热容器为研究对象,针对不同工况的运输环境,采用非线性有限元分析方法对该容器进行数值模拟,利用Tsai-Hill强度理论对环氧玻璃钢管结构进行强度校核。试验结果表明,环氧玻璃钢材料在低温环境下具有较好的拉压性能,但是抗剪切性能较差。模拟研究结果表明,低温液体运输车在实际运输过程中遭遇颠簸的路况时,相比于其他工况,此工况下支撑结构区域的Mises等效应力最大,但小于材料的许用应力;不同工况下固定端下支撑处的环氧玻璃钢管支撑结构相比于其他位置处所受的应力较大;环氧玻璃钢管作为该类容器的主要支撑构件,不同工况下其强度校核值远小于1,能够保证容器的安全运输。     

热固性树脂补强NBR的性能研究

研究环氧树脂(EP)、酚醛树脂(PF)和不饱和树脂(UP)对NBR胶料性能的影响.结果表明,在无炭黑NBR胶料中,EP的补强效果最佳,UP最差;在白炭黑补强NBR胶料中,PF和UP用量在12～20份之问补强效果较好,胶料的抗撕裂性能提高最明显.SEM显示,复合材料内部形成了局部互穿网络结构,树脂相直径约为200 nm.     

Fibre reinforced composites of multifunctional epoxy resins

Glass and carbon fibre reinforced epoxy composites were fabricated for N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) and its formulated systems with tri- and di-functional reactive epoxy diluents using 30% diaminodiphenyl sulphone (DDS) as a curing agent. The epoxy laminates were evaluated for their physical, chemical and mechanical properties [at room (26°C) and high (100°C) temperatures]. A marginal increase (<20%) in the mechanical properties of CFRP was found compared with GFRP laminates. Incorporation of epoxy diluents altered the mechanical properties of the composites significantly. The incorporation of triglycidyl-4-aminophenol diluent to TGDDM systems resulted in an improvement in mechanical properties of about 2–6%.     

增强热塑性塑料复合管国内外发展比较

详细分析了增强热塑性塑料复合管发展的市场、背景和应用现状,对国外成熟产品与国内产品的研发和应用案例作了比较。0前言我国塑料管道的生产和应用从上世纪九十年代起,开始进入一个快速发展时期;     

Parameters determining the strength and toughness of particulate-filled epoxy resins

The effects of such parameters as the filler volume fraction, particle size, aspect ratio, modulus and strength of filler, resin-filler adhesion, and toughness of the matrix on the stiffness, strength, and toughness of particulate-filled epoxy resins were evaluated. The mechanisms of crack initiation and subsequent crack propagation in these multiphase materials are discussed and illustrated by scanning electron microscopy of fracture surfaces.     

Electric strength of epoxide resins and its relation to the structure

Epoxide resins having various ratios of ether and ester bonds were investigated as to the relation between electric strength and polymer characteristics. The electric strength over a wide range of temperature is presented here. A marked reduction of strength characteristics of the epoxide resins occurs at a critical temperature indistinguishable from the glass transition temperature T_g, which is related to the free volume and molecular relaxation process. At temperatures exceeding T_g, the electric strength has a strong dependence on polymer structure, film thickness, and applied pulse width. This behavior is considered to obey the thermal breakdown mechanism, and it is assumed that the ion is important in the precursory region of electric breakdown.     

钢增强塑料管道市场前景（上）

中国的塑料管道行业也已经发展成为国民经济中的重要组成部分,总产量位居世界第一,并有广阔的发展前景。在各类管道之中,钢增强塑料管道由于其技术经济性能上的优势,在我国的塑料管道市场中占据了特殊的地位。本报告（《中国塑料管道市场分析报告》）就是在调查分析我国塑料管道发展现状基础上,提出钢增强塑料管道及其装备的市场发展前景。由...     

钢增强塑料管道市场前景（下）

中国的塑料管道业已经发展成为国民经济中的重要组成部分,管道管件总产量位居世界第一,并有广阔的发展前景。在各类管道之中,钢增强塑料管道由于其技术经济性能上的优势,在我国的塑料管道市场中占据了特殊的地位。本报告（《中国塑料管道市场分析报告》）就是在调查分析我国塑料管道发展现状基础上,提出钢增强塑料管道及其装备的市场发展前景...     

On the effect of the fiber orientation on the flexural stiffness of injection molded short fiber reinforced polycarbonate plates

The through-thickness fiber orientation distribution of injection molded polycarbonate plates was experimentally determined by light reflection microscopy and manual digitization of polished cross sections. Fiber length distribution was determined by pyrolysis tests followed by image analysis. A statistical analysis was done to determine the confidence limits of the fiber orientation results. The fiber orientation distribution was described by using second-order orientation tensors. The through-thickness stiffness variations were determined by the orientation averaging approach. This layer stiffness distribution was used to simulate the behavior of beams subjected to three point bending with a FEM Ansys model. The results were compared with experimentally determined flexural stiffness both in the flow direction and in the transverse flow direction. The effect of flow rate and melt-temperature on stiffness and fiber orientation is discussed.     

Time-dependent changes in mechanical properties of neat and reinforced epoxy resins

Several neat and reinforced epoxy resin formulations were prepared and investigated. Solid glass microspheres, with and without coupling agent, were used as reinforcement. After completion of post-cure all samples were quenched into an ice-water bath. Upon removal from the ice-water bath, dynamic mechanical and fracture properties of all samples were evaluated as a function of time elapsed after quenching. Electron microscopic evidence was obtained for the existence of nodular morphology in all cured systems. The changes in dynamic mechanical and fracture parameters, induced by the sub-T_g annealing, were described in terms of the model of inhomogeneous thermoset morphology.     

An additive for increasing the strength and modulus of amine-cured epoxy resins

The reaction product of 4-hydroxyacetanilide and 1,2-epoxy-3-phenoxypropane, when added at 19 wt% to a conventional epoxy-resin-curing agent mixture, increases the tensile strength of the cured system from 82 MPa to 123 MPa and increases the shear modulus (20°C, 1 Hz) from 970 MPa to 1560 MPa. As well as showing increased strength, the tensile-test specimens also fail in a ductile fashion, i.e., the slope of the stress–strain curve is negative at failure, with appreciable localized deformation occurring during fracture. For notched samples (compact tension specimens), the fracture properties are strongly strain-rate-dependent. At low strain rates the additive-containing sample has a fracture energy (??, critical strain energy release rate) about twice that of the additive-free control, but at higher strain rates ?? falls to about 65° of the control value. The critical stress for crack propagation is also strain-rate-dependent and is about 50% higher than the control at low strain rates and about 10% less than the control at higher strain rates. Dynamic mechanical analysis and dielectric loss measurements indicate that the additive causes a decrease in the T_g and a suppression of the β-relaxation. Chemically, the additive accelerates the cure process but does not significantly alter the final extent of reaction of the epoxy resin. After curing, the additive is almost totally extractable by solvent indicating that it is not chemicaly bound to the polymer. These observations are discussed in terms of the concept of antiplasticization.     

端羧基聚醚离子液体的合成及增强增韧酚醛树脂

采用阳离子开环聚合法先合成端羟基聚环氧氯丙烷(PECH)中间体,再将其与氯乙酸和N-甲基咪唑反应,制备端羧基聚醚咪唑离子液体([HOOC-PECH-MIM]Cl),并用红外和核磁谱图对其结构进行表征。用合成的端羧基聚醚离子液体与酚醛树脂预聚物共混,制备了改性酚醛树脂。用GPC测定了[HOOC-PECH-MIM]Cl的分子量及其分布,研究了分子量对酚醛树脂拉伸与冲击性能的影响。结果表明,合成的端羧基聚醚离子液体是目标产物,且其对酚醛树脂具有优异的增强增韧效果,当端羧基聚醚离子液体分子量为1 379时,[HOOC-PECH-MIM]Cl与酚醛树脂预聚物质量比为1∶4,改性后的酚醛树脂的冲击强度由原来的3.28 MPa提高到12.04 MPa,拉伸强度由原来的0.93 k J/m2提高到10.18 k J/m2。     

端羧基聚醚离子液体的合成及增强增韧酚醛树脂

采用阳离子开环聚合法先合成端羟基聚环氧氯丙烷(PECH)中间体,再将其与氯乙酸和N-甲基咪唑反应,制备端羧基聚醚咪唑离子液体([HOOC-PECH-MIM]Cl),并用红外和核磁谱图对其结构进行表征。用合成的端羧基聚醚离子液体与酚醛树脂预聚物共混,制备了改性酚醛树脂。用GPC测定了[HOOC-PECH-MIM]Cl的分子量及其分布,研究了分子量对酚醛树脂拉伸与冲击性能的影响。结果表明,合成的端羧基聚醚离子液体是目标产物,且其对酚醛树脂具有优异的增强增韧效果,当端羧基聚醚离子液体分子量为1 379时,[HOOC-PECH-MIM]Cl与酚醛树脂预聚物质量比为1∶4,改性后的酚醛树脂的冲击强度由原来的3.28 MPa提高到12.04 MPa,拉伸强度由原来的0.93 k J/m2提高到10.18 k J/m2。     

Modification of reinforced thermosetting plastic with ultraviolet radiation

Curing of filled systems previously treated with UV radiation is a first-order process with respect to the oligomers that takes place in the diffusion region. The slowing effect of viscose fibres in the initial stage of curing increases the impact strength of the reinforced material. The UV radiation increases the probability of linear chain growth during curing and results in material with a high average weight of crosslinked chains. UV treatment increases the impact strength and static bending breaking stress by 20–50% in comparison to materials obtained without irradiation and is an effective method of modification. The polymer reinforcement decreases the density and increases the strength characteristics of concrete articles in comparison to unreinforced concrete. __________ Translated from Khimicheskie Volokna, No. 1, pp. 45–48, January–February, 2008.