Carboxyl‐terminated butadiene acrylonitrile rubber/epoxy polymer alloys as damping adhesives and energy absorbable resins

Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber/epoxy (diglycidyl ether of bisphenol‐A: DGEBA) / diamino diphenyl methane (DDM) resins, in which CTBN was 60 wt % as the major component, were formulated to evaluate the damping and adhesive properties. In cases where acrylonitrile (AN) was 10～18 mol % as copolymerization ratio in CTBN, the blend resins showed micro‐phase separated morphologies with rubber‐rich continuous phases and epoxy‐rich dispersed phases. The composite loss factors (η) for steel laminates, which consisted of two steel plates with a resin layer in between, depended highly on the environmental temperature and the resonant frequencies. On the other hand, in the case where AN was 26 mol % in CTBN, the cured resin did not show clear micro‐phase separation, which means the components achieve good compatibility in nano‐scale. This polymer alloy had a broad glass‐transition temperature range, which resulted in the high loss factor (η > 0.1) for the steel laminates and excellent energy absorbability as the bulk resin in a broad temperature range. Also the resin indicated high adhesive strengths to aluminum substrates under both shear and peel stress modes. The high adhesive strengths of the CTBN/epoxy polymer alloy originated in the high strength and the high strain energy to failure of the bulk resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Adhesive strength and mechanisms of epoxy resins toughened with pre-formed thermoplastic polymer particles

The aim of this study was to characterize the adhesive properties of epoxy resins toughened with pre-formed polyamide-12 particles in comparison to the conventional approach using core–shell rubber particles. Dicyandiamide-cured diglycidyl ether of bisphenol-A was used as the base epoxy resin. The T-peel adhesive strength of the toughened resin containing 20 phr polyamide-12 particles was about 3-times higher than that of the unmodified resin. In the case of rubber toughening, the improvement in adhesive strength tended to reach a plateau, even after improvement in the resin toughness itself. Besides, the polyamide particle toughening utilizes the bulk resin toughness for the peel adhesive strength, even in a thin adhesive layer between the substrates. The polyamide particles embedded in epoxy resin matrix were fractured after bridging cracks and stretching in the peel process. The crack-bridging mechanism by the pre-formed thermoplastic polymer particles was operative behind the crack-tip and would, therefore, experience a relatively small constraint by the presence of rigid metal substrates in comparison to conventional rubber toughening. The requirements for the polymer particles to work as a modifier using the bridging mechanism would be good adhesion to the epoxy matrix, high toughness and a relatively lower modulus of elasticity than that of matrix resin.     

Studies on The Modification of Epoxy Resin with Silicone Rubber

In order to find a compatibilizer for epoxy resin/silicone rubber systems, interfacial tension of epoxy resin mixed with modified silicone oils which had the compatible groups to epoxy resin was measured against RTV silicone rubber and silicone oil. From the results, it was found that one of polyether modified silicone oils (EtMPS) had strong interfacial activity. Then using the EtMPS as the compatibilizer, RTV silicone rubber or silicone diamine was filled in epoxy resin. The effects of silicone content of these materials on impact fracture energy and on peel strength were investigated. The impact fracture energy of epoxy resin was increased by the addition of RTV silicone rubber up to two times that of unmodified resin while silicone diamine had almost no effect which might be due to the small molecular weight. T-peel strengths of aluminium plates bonded by epoxy resin filled with RTV silicone rubber and with silicone diamine effectively increased with the increasing of silicone content showing the maximum at 10 ∼ 20 phr. The fracture surfaces after the mechanical tests of these materials were observed by a scanning electron microscope. Many particles of silicone rubber in the size of 1 ∼ 20 μ were observed over the fracture surface.     

Studies on The Modification of Epoxy Resin with Silicone Rubber

In order to find a compatibilizer for epoxy resin/silicone rubber systems, interfacial tension of epoxy resin mixed with modified silicone oils which had the compatible groups to epoxy resin was measured against RTV silicone rubber and silicone oil. From the results, it was found that one of polyether modified silicone oils (EtMPS) had strong interfacial activity. Then using the EtMPS as the compatibilizer, RTV silicone rubber or silicone diamine was filled in epoxy resin. The effects of silicone content of these materials on impact fracture energy and on peel strength were investigated. The impact fracture energy of epoxy resin was increased by the addition of RTV silicone rubber up to two times that of unmodified resin while silicone diamine had almost no effect which might be due to the small molecular weight. T-peel strengths of aluminium plates bonded by epoxy resin filled with RTV silicone rubber and with silicone diamine effectively increased with the increasing of silicone content showing the maximum at 10 ～ 20 phr. The fracture surfaces after the mechanical tests of these materials were observed by a scanning electron microscope. Many particles of silicone rubber in the size of 1 ～ 20 μ were observed over the fracture surface.     

核壳聚合物增韧环氧树脂的研究及进展

核壳聚合物(CSP)用来增韧环氧树脂的最大优点,即在提高韧性的同时而不降低材料的Tg和加工性能。综述了核壳聚合物增韧环氧树脂的特点,核壳聚合物的制备方法、微观结构及形态,以及增韧环氧树脂及其复合材料的性能及影响因素。树枝形聚合物作为一种结构特殊的聚合物,也越来越得到广泛的研究和应用。并对环氧树脂的增韧机理进行了阐述,即空穴化-塑性形变。文中还对核壳聚合物及树枝形聚合物增韧环氧树脂进行了展望。     

核-壳粒子和液体橡胶增韧环氧胶粘剂的研究

采用丙烯酸酯核-壳粒子和液体橡胶分别增韧改性环氧树脂胶粘剂,探讨了2种增韧体系对冲击强度和粘接强度的影响。研究发现,核-壳粒子在用量较少的情况下可获得比液体橡胶更优异的冲击强度和粘接强度,剥离强度达到10 kN/m以上。通过SEM观察改性环氧树脂断裂表面的微观形貌,并通过TEM进一步观察核-壳粒子增韧环氧树脂的分散状态,探讨微观形态与冲击强度和粘接强度之间的关系。     

Mechanical properties and fracture behaviors of epoxy composites with phase‐separation formed liquid rubber and preformed powdered rubber nanoparticles: A comparative study

Epoxy composites filled with phase‐separation formed submicron liquid rubber (LR) and preformed nanoscale powdered rubber (PR) particles were prepared at different filler loading levels. The effect of filler loading and type on the rheological properties of liquid epoxy resin suspensions and the thermal and mechanical properties of the cured composites as well as the relative fracture behaviors are systematically investigated. Almost unchanged tensile yield strength of the cured epoxy/PR composites is observed in the tensile test compared with that of the neat epoxy; while the strength of the cured epoxy/LR composites shows a maximum value at ∼4.5 wt% and significantly decreases with increasing LR content. The glass transition temperature (T_g) of the cured PR/epoxy has shifted to the higher temperature in the dynamic mechanical thermal analysis compared with that of the cured pure epoxy and epoxy/LR composites. Furthermore, the presence of LR results in highly improved critical stress intensity factor (K_IC) of epoxy resin compared with the corresponding PR nanoparticles. In particular, the PR and LR particles at 9.2 wt% loading produce about 69 and 118% improvement in K_IC of the epoxy composites, respectively. The fracture surface and damage zone analysis demonstrate that these two types of rubber particles induce different degrees of local plastic deformation of matrix initiated by their debonding/cavitation, which was also quantified and correlated with the fracture toughness of the two epoxy/rubber systems. POLYM. COMPOS., 36:785–799, 2015. © 2014 Society of Plastics Engineers     

Structure and properties of epoxy resins modified with acrylic particles

The morphology and material properties of dicyandiamide (DICY)‐cured epoxy resins modified with acrylic particles consisting of a PBA (polybutyl acrylate) core and a PMMA (polymethyl methacrylate) shell and epoxy resins modified with acrylic rubber (PBA) particles alone were studied. It was found that the epoxy system modified with core/shell acrylic particles showed higher fracture toughness, indicating that the modification had a larger effect on improving the material properties of the epoxy resin. A characteristic shown by the core/shell acrylic particles is that they swell along with the epoxy resin under exposure to heat and gel before the latter cures. In this process, the epoxy resin penetrates the surface of the shell layer and a bond is formed between the epoxy matrix and the core/shell acrylic particles. This suggests that the epoxy matrix around the core/shell acrylic particles has the effect of increasing the level of energy absorption due to plastic deformation of the matrix. This is thought to explain why the epoxy resin modified with core/shell acrylic particles showed higher fracture toughness. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2955–2962, 1999     

Modification of Epoxy by a Liquid Elastomer and Solid Rubber Particles

Summary This work covers studies on epoxy resin systems modified with two different rubber phases. The first modification was the use of recycled car tire rubber particles; while in the second one a silicon based liquid elastomer (Tegomer) was mixed with the epoxy resin matrix. In the third method epoxy resin was modified with both solid rubber particles and liquid elastomer together.Mechanical tests showed that these modifications resulted in no significant improvements in the mechanical performance of the epoxy resin system. Fractographic studies indicated that poor interfacial adhesion was occurred between the epoxy matrix and the solid rubber particles, while liquid elastomer resulted in formation of round rubbery domains and some plastic deformation lines in the epoxy matrix. For better improvements interfacial phenomenon will be explored.     

The fracture of epoxy- and elastomer-modified epoxy polymers in bulk and as adhesives

The fracture behavior of a piperidine/bisphenol A diglycidyl ether (A) resin has been determined in bulk and as an adhesive using the linear elastic fracture methods developed by Mostovoy¹. The effect of adding carboxy-terminated butadiene–acrylonitrile (CTBN) elastomer to resin A was investigated. The opening-mode fracture energy () of resin A was 120 to 150 J/m², and largely attributable to plastic deformation. Fractographic evidence was obtained for plastic flow at the crack tip during crack initiation. Propagation was unstable due to the rate dependence of the plasticity. There were no significant differences in the bulk and adhesive fracture behavior. Addition of 5–15% CTBN to resin A produced minute elastomer particles which increased to ～4000J/m² (at 15%). Further CTBN addition resulted in an elastomer–epoxy blend and a decrease in fracture energy. Fractography again indicated that crack initiation involved plastic deformation but that the elastomer had greatly increased the volume in which the deformation occurred. The adhesive fracture of the elastomer–epoxy was found to be strongly dependent on the crack-tip deformation zone size (r_yc) in that was a maximum when bond thickness was equal to 2 r_yc. At bond thicknesses less than 2 r_yc, there was a restraint on the development of the plastic zone resulting in lower values.     

Carboxyl-terminated poly(propylene glycol) adipate-modified room temperature curing epoxy adhesive for elevated temperature service environment

An investigation was carried out into the effect of modification of an epoxy resin with carboxyl-terminated poly(propylene glycol) adipate (CTPPGA) liquid rubber, on room temperature and elevated temperature adhesive joint strengths, after curing at room temperature (25°C) with tris-2,4,6-(N,N-dimethyl amino methyl) phenol hardner. CTPPGA prepared by the esterification of poly(propylene glycol) (PPG) and molar excess of adipic acid was incorporated into the epoxy resin by the prereact method. CTPPGA modification showed significant enhancement of adhesive joint strengths over the unmodified epoxy and the joint strengths were found to depend on the molecular weight of CTPPGA and its content in the epoxy resin. The elevated temperature lap shear strength measurement made for the CTPPGA-modified epoxy adhesive showed that the adhesive formulation has a temperature service capability up to 120°C. The results are discussed in terms of the data obtained from the tensile tests, DSC analysis, and SEM observations of the fractured surfaces.     

高性能室温固化环氧结构胶的制备与研究

为了改善环氧固化物的韧性,又保持其热稳定性及提高其抗冲击性能,采用超细全硫化羧基丁腈橡胶粒子改性环氧树指技术,并辅以玻璃微珠,球型硅微粉,ACR丙烯酸酯橡胶微球等抗冲剂填充,制备出一款高性能室温固化环氧结构胶.实验中采用高速搅拌球磨法在环氧树脂中分散超细全硫化羧基丁腈橡胶粒子,辅以填充物,制备的环氧树脂结构胶剪切冲击强...     

有机硅硼改性环氧耐高温胶粘剂

采用自制有机硅硼树脂改性双酚A环氧树脂,配合AG-80环氧树脂,改性咪唑为固化剂,得到80～100℃固化的无溶剂耐高温胶粘剂。室温剪切强度大于15MPa,200℃剪切强度大于8Mpa,分析表明,该树脂体系具有优异的耐温性能。200℃／1000h老化具有较高的粘接强度,DSC分析表明,具有良好的热稳定性。扫描电镜分析表明,二元改性体系中存在均匀的“孔洞”结构和微分相,可以减小应力集中和阻止断裂发生,达到增韧效果。     

Temperature effects on rigid nano‐silica and soft nano‐rubber toughening in epoxy under impact loading

The rigid nano‐silica and soft nano‐rubber toughening effects on neat epoxy under impact loading in a range of ?50 to 80 °C were investigated. Nanosilica particles (20 nm) toughened neat epoxy at all temperatures with a maximum toughening efficiency at ?50 °C and lower efficiency at elevated temperatures. In contrast, except at ?50 °C, nano‐rubber particles (100 nm) showed the deterioration effect on the impact fracture toughness of epoxy resin. Scanning electron microscopy examinations revealed that the crack pinning and local epoxy deformation induced by rigid particles in term of nano‐silica/epoxy and nano‐rubber/epoxy interfacial debonding (at ?50 °C) led to positive toughening efficiency on neat epoxy. However, at 20 and 80 °C, the rubber cavitations/void plastic growth was significantly suppressed under the impact loading, which led to the negative toughening efficiency on epoxy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45319.     

Fracture properties of epoxy/poly(styrene‐co‐allylalcohol) blends

The epoxy/polystyrene system is characterized by a poor adhesion between the constituent phases, which determines its mechanical properties. The adhesion can be improved via blends based on epoxy resin and random copolymers, poly(styrene‐co‐allylalcohol) (PS‐co‐PA). In this work, the influence of PS‐co‐PA content and the good adhesion between the phases on the tensile properties and the fracture toughness achieved through instrumented Charpy tests have been investigated. The tensile strength and the deformation at break showed an increase in the PS‐co‐PA content while the Young's modulus remained the same. The tensile fracture surfaces revealed that the improvement of these magnitudes was mainly due to a crack deflection mechanism. Also, the fracture toughness of the blends was superior to that of the pure epoxy resin. The main operating toughening mechanism was crack deflection. The fractographic analysis showed that ～ 80% of the particles were broken, and the crack tended to divert from its original path through the broken PS‐co‐PA particles. The remaining particles were detached from the epoxy resin, and the holes left suffered plastic deformation. Analytical models were used to predict successfully the toughness due to these mechanisms. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

环氧改性丙烯酸酯结构胶的研究

以环氧丙烯酸酯树脂、端羧基丁腈橡胶改性环氧预聚物、多官能度环氧作为改性环氧树脂,对传统的第二代丙烯酸酯结构胶黏剂进行改性研究,测试表征了耐高温性、耐水性、伸长率、贮存性能等。结果表明,同时采用多种改性环氧树脂对丙烯酸酯结构胶进行改性,其综合性能明显提高:180℃剪切强度由0.3MPa提高到2.7MPa、28d浸水试验剥离强度保持率由2%提高到75%、断裂伸长率由3.5%提高到19.3%。     

Use of surface modified recycled rubber particles for toughening of epoxy polymers

The objective of this research is to investigate the feasibility of using surface treated recycled rubber particles for toughening of epoxy polymers. These particles are obtained through grinding of scrap tires followed by oxidizing the surface of the particles in a reactive gas atmosphere. Surface treated recycled rubber particles with a nominal particle size of approximately 75 μm and a commonly used reactive liquid elastomer, CTBN, have been incorporated in a DGEBA epoxy resin. It has been shown that the recycled rubber particles are not as effective as CTBN in toughening of the epoxy matrix. However, blending of the two modifiers results in a synergistic toughening. Microscopy reveals that, when used alone, recycled rubber particles simply act as large stress concentrators and modestly contribute to toughening via crack deflection and microcracking. In the presence of micron size CTBN particles, which cavitate and induce massive shear yielding in the matrix, however, the recycled particles “stretch” the plastic deformation to distances far from the crack tip. This mechanism causes plastic zone branching and provides an unexpectedly high fracture toughness value. This study, therefore, provides a practical approach for manufacturing engineering polymer blends utilizing the surface modified recycled rubber particles.     

室温固化耐热环氧树脂结构胶粘剂

介绍了一种液体端羧基丁氰橡胶 (CTBN)改性环氧树脂为主体 ,以改性聚硫橡胶为固化剂的结构胶粘剂 ,强度高 ,韧性好 ,室温固化 10天 ,室温剪切强度 2 5 .9MPa ,12 0℃剪切强度为 14 .9MPa ,室温剥离强度 6 .0kN/m ,综合性能优异。用于航空、航天工业耐热结构部件的粘接     

The Curing Behavior and Adhesion Strength of the Epoxidized Natural Rubber Modified Epoxy/Dicyandiamide System

The curing properties and adhesive strengths of the epoxidized natural rubber (ENR, 25 mole percent epoxidation) modified epoxy systems are studied with differential thermal calorimetry (DSC), scanning electron microscopy (SEM), and lap shear strength (LSS) measurement. The results of DSC analyses indicate that the curing exotherm, the curing rate, the reaction order, and the glass transition temperature of the epoxy system are affected by the presence of reactive ENR. From SEM micrographs, it is obtained that a second spherical rubber phase is formed during cure and the particle size of the rubber phase is increased by increasing the curing temperature and the ENR content. The changes of the volume fraction of the rubber phase and the T_g of the cured systems indicate that the mutual dissolution between epoxy resin and ENR happens and which changes with the curing temperature and the ENR content. The LSS of adhesive joints prepared with the ENR modified adhesives are all lower than those of the unmodified epoxy system, and decrease with increasing the amount of ENR added because of the limited compatibility of the ENR with the epoxy matrix.     

Adhesive properties of epoxy resin modified by end‐functionalized liquid polybutadiene

Adhesive properties of epoxy resin networks modified with different functionalized liquid polybutadiene were evaluated by using aluminum adherent. The end‐functionalized polybutadiene rubbers were hydroxyl‐ (HTPB), carboxyl‐ (CTPB), and isocyanate‐terminated polybutadiene (NCOTPB). The adhesive properties depend upon the morphology and the degree of interaction between the rubber–epoxy system. The most effective adhesive for Al–Al joint in both butt and single‐lap shear testing was epoxy resin–NCOTPB system. This system presents stronger rubber–epoxy interactions and a higher degree of rubber particle dispersion with particle size diameter in the nanoscale range. These characteristics were not important for improving the toughness of the bulk network but are fundamental for the improvement of adhesive strength. The effect of the pretreatment of the aluminum surface on the roughness was also evaluated by using profilometry analysis. The type of failure was also investigated by analyzing the adhered surfaces after fracture by scanning electron microscopy and profilometry. A proportion of cohesion failure higher than 90% was observed in all systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2370–2378, 2004