Synthesis and properties of epoxy resin modified with epoxy-terminated liquid polybutadiene

Epoxy resin networks have been modified with block copolymer of polybutadiene and bisphenol A diglycidyl ether (DGEBA)-based epoxy resin. Block copolymers prepared from isocyanate-terminated polybutadiene (NCOPBER) resulted in cured transparent epoxy networks with no discernible phase-separated morphology, as indicated by scanning electron microscopy. Epoxy resin modified with block copolymer derived from carboxyl-terminated polybutadiene (CPBER) presented an opaque aspect with dispersed rubber particle diameters in the range of 0.5-3μm. This value is substantially smaller than that found in epoxy matrix modified with hydroxyl-terminated polybutadiene. The different morphological characteristics observed in these modified systems were attributed to the different times to achieve the gelation (gel time) and also to the different structures of the block copolymers. The visual homogeneity of the NCOPBER block copolymer-modified network cannot be attributed to the presence of dissolved rubber, since the glass transition temperature of the epoxy matrix (determined from dynamic mechanical analysis) has not been substantially influenced by the presence of this block copolymer. The epoxy resin modified with the different block copolymers presented an improved impact resistance. The best mechanical performance in terms of flexural and tensile properties was achieved with the block copolymer derived from carboxyl-terminated polybutadiene, whereas a more flexible material has been obtained with NCOPBER block copolymer-modified network.     

Flexibility improvement of short glass fiber reinforced epoxy by using a liquid elastomer

In certain applications of fiber reinforced polymer composites flexibility is required. The aim of this study was to improve flexibility of short glass fiber reinforced epoxy composites by using a liquid elastomer. For this purpose, diglycidyl ether of bisphenol-A (DGEBA) based epoxy matrix was modified with hydroxyl terminated polybutadiene (HTPB). A silane coupling agent (SCA) was also used to improve the interfacial adhesion between glass fibers and epoxy matrix. During specimen preparation, hardener and HTPB were premixed and left at room temperature for an hour before mixing with epoxy resin to allow possible reactions to occur. In order to compare flexibility of the specimens flexural tests were conducted and the data were evaluated numerically by using a derived relation. Test data and scanning electron microscope analysis indicated that surface treatment of glass fibers with SCA, and HTPB modification of epoxy matrix improved flexural properties especially due to the strong interaction between fibers, epoxy, and rubber. It was also observed that HTPB modification resulted in formation of relatively round rubber domains in the epoxy matrix leading to increased flexibility of the specimens.     

国内外顺丁橡胶的市场分析

分析了国内外顺丁橡胶的生产和消费情况，提出了发展我国顺丁橡胶生产的一些建议。     

高分子附聚法450nm聚丁二烯胶乳的制备研究

高分子附聚方法是一项独特的技术。特别是在制备超大粒径胶乳方面,可以在较短的时间内制备稳定的胶乳,从而改善产品质量,提高生产效率。作者对制备粒径450nm聚丁二烯胶乳的附聚工艺进行了深入研究,考察了附聚剂胶乳用量、附聚后静置时间、乳化剂用量和搅拌强度等附聚工艺对聚丁二烯胶乳粒径及稳定性的影响,确定了制备450nm聚丁二烯胶乳较为优化的附聚工艺,制备的聚丁二烯胶乳稳定,可用于高性能ABS的制备。     

中空玻璃用双组份聚氨酯密封胶的研究

以端羟基液体聚丁二烯、粗MDI为主要原料,复配制备中空玻璃用双组份聚氨酯密封胶。研究了NCO/OH比例、填料、增塑剂、扩链剂、粘接促进剂及催化剂含量对双组份聚氨酯密封胶性能的影响。     

Synthesis of polybutadiene-acrylates and properties of the photocured films

The acrylation of polybutadienes was performed by reaction of acrylic acid with epoxy, epoxy-hydroxyl functionalized and hydroxyl-terminated oligomers. Some epoxy-functionalized oligomers were previously obtained by epoxidation of a liquid 1,4-polybutadiene. The properties of the acrylated products were affected by the oligomer type and the reaction procedure. The UV-curing of these products was studied by FTIR and thermal analyses, which showed the amorphous and rubbery nature of the resulting films. In some cases, the double bonds conversion was increased by a thermal post-curing, but the adhesion properties were strongly reduced. The swelling of the UV-cured films was studied by varying the solvent polarity. The mixtures of some polybutadiene-acrylates with a typical epoxy-acrylic resin gave highly cross-linked films showing a flexibilizing effect due to the polybutadiene oligomers which can act as reactive diluents.     

The dynamic response of isolated polybutadiene chains undergoing thermal retraction from extended conformations

All-atom molecular dynamic simulations were performed on isolated polybutadiene chains to study the retraction velocity of a free end of an idealized network chain from extended conformations due to thermal collisions. We compare the snap-back velocity calculated from these simulations with experimental measurements on bulk rubber samples. Over a range of chain lengths, extension ratios and temperatures, we find that the average retraction velocity of a free end seen in the simulations is about two orders of magnitude less than the experimental value.     

Toughening mechanisms of rubber modified thin film epoxy resins

An epoxy terminated polybutadiene (ETPB) was synthesized and utilized to enhance the toughening of an epoxy system, in both bulk and coating states. In the first step, the fracture energy of the modified samples was determined using a single edge notched type specimen in a three point bending (SEN3PB) geometry. The effective toughening mechanisms of bulk epoxy specimens were examined using scanning electron microscopy (SEM). The results showed that plastic void growth, cavitation and shear yielding mechanisms were the main toughening mechanisms of the bulk epoxy systems. In the next step, mechanical properties (i.e. impact resistance, flexibility, cupping resistance and hardness) and adhesion of the thin film specimens were evaluated in accordance to the amount of synthesized ETPB. The results showed that the mechanical properties of the ETPB modified epoxy resins considerably improved. In all cases, it was found that the improvement of the mechanical properties reached a maximum at 7.5 wt.% and then began to decrease with further increase in ETPB content. The effective toughening mechanisms in the modified thin films were also examined using SEM and compared to the bulk types. In contrast to the bulk types, the results showed that crack arresting and shear yielding were active mechanisms in thin films. The contribution of these mechanisms led to the improvement of adhesion and mechanical properties by energy dissipation.     

环氧化聚丁二烯树脂

讨论了环氧化聚丁二烯的制备方法、化学特性、固化物性能及其在涂料、离子交换树脂、胶粘剂和阻燃材料中的应用。