端羟基丁腈共聚物对环氧树脂的增韧

国外早期曾用丁腈橡胶增韧环氧树脂。六十年代后，主要用端羧基丁腈共聚物（丁腈羧，CTBN）作为增韧剂增韧环氧树脂。但丁腈羧的合成方法中，引发剂引发效率很低，产品纯制比较麻烦，要使用较多溶剂，因此，成本较高。这是使用丁腈羧作为增韧剂的缺点。针对这种情况，朴光哲曾研究用丁腈羟增韧环氧树脂，方法是先将羟基转化成羧基后，，再用于增韧环氧树脂。使用丁腈羟作为增韧剂的原因是因为丁腈羟合成较易，是遥瓜型液体橡胶中价格较低的品种。我们认为，用丁腈羟增韧环氧树脂是适宜的，可以解决用丁腈羧作为增韧剂所存在的问题。但上述方法是经过端基转化，间接使用丁腈羟的方法。此论文的内容是研究直接使用丁腈羟作为增韧剂的方法。即略去端基转化过程，这样可以达到简化工艺的目地。另外，在固化体系中，增加酸酐用量。使酸酐既与丁腈羟反应，也与环氧基反应，又与仲羟基反应。这样有利于改进增韧环氧树脂的结构和性能。按照这种设想，设计了增韧环氧树脂固化体系。在此基础上，所进行的研究工作内容包括：1，固化反应动力学；2，固化物的力学性质；3，固化物的形态结构；4，固化物的TTT图；5，固化物的热分解。用示差扫描量热计及红外光谱对六氢邻苯二甲酸酐固化的增韧环氧树脂进行了固化反应动力学的研究，得到固化温度，固化时间和转化率的关系式为：1/0.2 [1/((1-P)~(0.2)) - 1] = kt其中，P为转率；K为表观反应速率常数；t为反应时间。通过此式，即可达到控制固化反应的目地。同时还得到该体系的固化速率主要决定于酸酐的扩散过程，其原因认为是由于固化反应过程中，微观凝聚相的形成。对不同固化体系增韧环氧树脂的力学性能研究表明。固化物性能的变化一般可分为增韧，增柔，相倒转三个阶段。丁腈羟增韧环氧树脂的增韧效果与所选固化剂种类，丁腈羟用量、丁腈羟中丙烯腈的含量有关。在所研究的酸酐固化体系中，以六氢邻苯二甲酸酐固化体系的增韧效果最好。从固化物的综合性能看，增韧剂用量以10～20份，丁腈羟中丙烯腈含量以15%左右为宜。丁腈羟用量为10份的增韧体系中，抗剪强度提高20%达27MPa，抗张强度提高41%，达80MPa。断裂伸长提高一倍，断裂功提高三倍，断裂表面能提高十倍。而杨氏模量仅降低7%倍。固化物各阶段的力学性能取决于固化物的形态结构。其形态结构与环氧树脂固化体系中各组分的相容性及固化速度密切相关。未增韧的环氧树脂是均相，增韧环氧树脂是两相结构。由橡胶微区和环氧基体组成，橡胶微区的大小和组成与丁腈羟用量，橡胶中丙烯腈含量，固化温度有关。随丁腈羟用量加大，橡胶微区增多，直径分布增大。用量增到一定程度，发生相倒转现象。固化剂不同，微区和基体的结构差异很大。六氢邻苯二甲酸酐，70酸酐，甲基四氢邻苯二甲酸酐固化体系的形态结构相似。甲基内次甲基四氢邻苯二甲酸酐固化体系的橡胶微区是由橡胶-环氧组成的橡胶富集相。桐油酸酐固化体系则有更小的橡胶微区出现。用扫辨仪研究了增韧和未增韧环氧树脂的等温固化过程。作出TTT图。得出两体系的固化行为相似，增韧环氧树脂的玻璃化曲线略有推迟，Tg_0 = -23 ℃, Tg_∞ = 85 ℃，(未增韧环氧树脂Tg_∞ = 88 ℃)。通过热重分析法研究以六氢邻苯二甲酸酐为固化剂的丁腈羟增韧环氧树脂在空气中分解的情况。起始分辨温度为250 ℃。表现活化能由180kJ/mol提高到280kJ/mol。分解过程中有一缓慢失重阶段，在酸酐用量较大的情况下，起始分解温度降低，说明增大酸酐用量并未提高固化物交联密度。总之，用丁腈羟直接增韧环氧树脂是一个适宜的增韧方法。解决了用丁腈羧作为增韧剂的缺点。为环氧树脂的增韧技术，增添了新的内容。

液体橡胶 HTBN 增韧耐高温环氧树脂

通过热重分析仪研究了四氢邻苯二甲酸酐做固化剂增韧 F－44 环氧树脂在 N_2 气中分解的情况。起始分解温度为 320℃，表观活化能为 260KJ/mol，随着反应程度的增加，分解活化能升高。HT13N 能够增韧 F－44 环氧树脂和酚酞环氧树脂。有两方面的特点。一是降低 CTBN 增韧氧树脂的成本。二是提高了环氧树脂增韧体系的耐热性。这些为增韧环氧树脂的研究增添了新的内容。

Studies on the Toughening of Epoxy Resins

This thesis aims to develop new toughened systems for epoxy resin via physical and chemical modifications. Initially the synthesis of DGEBA was carried out and the properties compared with that of the commercial sample. Subsequently the modifier resins to be employed were synthesized. The synthesized resin were characterized by spectroscopic method (FTIR and H NMR), epoxide equivalent and gel permeation chromatography. Chemical modification involves the incorporation of thermoset resins such a phenolics, epoxy novolacs, cardanol epoxides and unsaturated polyester into the epoxy resin by reactive belnding. The mechanical and thermal properties of the blends were studied. In the physical modification route, elastomers, maleated elastomers and functional elastomers were dispersed as micro-sized rubber phase into the continuous epoxy phase by a solution blending technique as against the conventional mechanical blending technique. The effect of matrix toughening on the properties of glass reinforced composites and the effect of fillers on the properties of commercial epoxy resin were also investigated. The blends were characterized by thermo gravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy and mechanical property measurements. Among the thermoset blends, substantial toughening was observed in the case of epoxy phenolic novolacs especially epoxy para cresol novolac (ECN). In the case of elastomer blending , the toughest blends were obtained in the case of maleic anhydride grafted NBR. Among functional elastomers the best results were obtained with CTBN. Studies on filled and glass reinforced composites employing modified epoxy as matrix revealed an overall improvement in mechanical properties

Block Copolymers of Unsaturated Polyesters and Functional Elastomers

Block copolymers of unsaturated polyester were prepared by condensation polymerization of hydroxyl or carboxyl terminated liquid rubbers with maleic anhydride, phthalic anhydride, and propylene glycol. The condensate obtained was mixed with styrene monomer to get an unsaturated polyester resin formulation. In this study, copolymers of unsaturated polyesters with hydroxy terminated polybutadiene, carboxy terminated nitrile rubber, and hydroxy terminated natural rubber were prepared. Mechanical properties such as tensile strength, tensile modulus, elongation at break, toughness, impact strength, surface hardness, abrasion resistance, and water absorption were evaluated after the resin was cured in appropriate molds for comparison with the control resin. The fracture toughness and impact resistance of CTBN-modified unsaturated polyester show substantial improvement by this copolymerization without seriously affecting any other property

Bond properties of rubber modified epoxy

In this paper, the bond integrity of unmodified and rubber-modified epoxy used for bonding the carbon fibre sheets to the hosting steel surface was investigated. The rigidity of the bonding agent is one of the factors that have a significant role in the premature failure (debonding) of this application. In order to overcome this issue, a series of experiments were conducted on the steel plates using the epoxy resin modified by CTBN and ATBN reactive liquid polymers, in addition to the unmodified epoxy resin. The interface between the carbon fibre matrix and the hosting surface is subjected to a longitudinal shear force for which the corresponding displacement is recorded. The shear stress-strain relationship for the tested specimen is plotted. The result shows that, the bond behaviour of modified epoxy using CTBN and ATBN reactive liquid polymers was improved in terms of ductility and toughness.

Experimental investigation on bonding properties of reactive liquid rubber epoxy in CFRP retrofitted concretet members

The load bearing capacity of aging reinforced concrete structures, such as bridges, is increasingly extended with the use of Carbon Fibre Reinforced Polymer (CFRP). Premature failure, which is attributed to the rigid behaviour of the bonding agent (epoxy resin) and the high stresses at the interface region, can occur because of the debonding of CFRP sheets from host surfaces. To overcome the debonding issue, the epoxy resin is modified by different reactive liquid polymers to improve its toughness, flexibility, adhesion, and impact resistance. This study reports the usage of two reactive liquid polymers, namely, liquid Carboxyl-Terminated Butadiene-Acrylonitrile (CTBN) and liquid Amine-Terminated Butadiene-Acrylonitrile (ATBN), to improve the mechanical properties of the commercially available MBrace saturant resin when added to a ratio of 100:30 by weight. The neat and modified epoxies were analysed using the Dynamic Mechanical Thermal Analysis (DMTA) to determine and compare the storage modulus and glass transition temperatures of these materials. Moreover, the bonding strength of neat and modified epoxies was evaluated through single-lap shear tests on CFRP sheets bonded to concrete prisms. The results indicate that the modified resins exhibited improved ductility and toughness and became reasonably flexible compared with the neat epoxy resin. The improved properties will help delay the premature debonding failure in CFRP retrofitted concrete members.

Experimental investigation on CFRP-steel bond properties using ionic liquid

Solving the problem of pre mature debonding of CFRP retrofitted structure is a main concern for most of structural engineers nowadays. Reducing the brittleness of the bonding agent at the CFRP/concrete interface is a major factor to avoid this behaviour. In this research, the effect of modifying the bonding agent using different percentages of ionic liquid (IL) is investigated. This paper reports on an experimental investigation on the behaviour of modified epoxy resin with IL. Steel plates were used as hosting surface of the CFRP laminates, the laminates were attached to the steel surface using the IL modified epoxy. The shear mechanism at the interface of CFRP laminates to steel plates is discussed considering the relationship between the shear and the slip at the interface. The shear stress- displacement are traced for all specimens, the results are compared with control test prepared using unmodified epoxy. A 20% IL modified epoxy shows improved Behaviour. The improvement is with respect to ductility enhancement of the overall behaviour.