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.     

纳米碳酸钙含量对室温硫化硅橡胶热稳定性的影响

测试了不同纳米碳酸钙含量的室温硫化硅橡胶的热稳定性,并结合对不同纳米碳酸钙含量填充硫化胶的热降解活化能的计算可知,随着纳米碳酸钙含量的增加热降解活化能增加,说明纳米碳酸钙的填充可提高室温硫化硅橡胶耐热性能。其机理是纳米碳酸钙与硅橡胶的相互作用,从而提高了纳米碳酸钙填充室温硫化硅橡胶的耐热性能。     

低模量硫化硅橡胶粘接研究

采用sol—gel工艺自制的SiO2补强增韧环氧树脂作为胶粘剂,对低模量硫化硅橡胶与金属或复合材料进行粘接试验,分析胶粘剂中SiO2理论含量及粘接工艺对粘接性能的影响,并把硫化硅橡胶放在改性环氧树脂中进行溶张试验,探索胶粘剂对硅橡胶的粘接机理、结果表明,随着SiO2先驱体-有机硅烷含量的增加,硅橡胶的溶胀程度提高改性环氧树脂胶粘刺能浸入硅橡胶的表层,对硅橡胶具有良好的亲和力。用该胶粘剂对硅橡胶与金属或复合材料进行粘接时,取得了良好的粘接效果。     

Influence of crosslinking degree of silicone rubber particles on properties of epoxy resin

Silicone rubber particles with different degrees of crosslinking were prepared. Silicone oils containing Si—H groups and vinyl groups were reacted at various mol ratios in their composite emulsions. Epoxy resin was modified using these particles and the results indicated that the content of the silicone rubber particles, the crosslinking degree of the rubber particles, and the addition of a coupling agent affected the properties of the modified epoxy resins. The influence of the coupling agent depends on the crosslinking degree of the silicone rubber particles. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 619–625, 1998     

缩合型室温硫化硅橡胶耐热性能的研究

采用单因素变量法研究了不同的生胶(107胶)分子量,硅烷交联剂、催化剂以及硅烷偶联剂对缩合型室温硫化(RTV)硅橡胶耐热空气老化的影响,并初步探讨了自制有机硅高沸树脂对RTV硅橡胶在空气中耐热性的影响。通过热重分析仪(TGA)表征了RTV硅橡胶的热失重。结果表明,催化剂对RTV硅橡胶的耐热性有很大影响。有机硅高沸树脂可适当提高RTV硅橡胶的耐热性能,且在一定范围内,RTV硅橡胶的最大热失重温度和最终残炭率均随高沸树脂添加量的增加而增加。耐热性较好的RTV硅橡胶组分为:较高分子量的107胶、正硅酸乙酯、氨丙基三乙氧基硅烷、钛酸丁酯,以及适量的有机硅高沸树脂。     

Toughening of epoxy resin by functional‐terminated polyurethanes and/or semicrystalline polymer powders

Hydroxyl‐, amine‐, and anhydride‐terminated polyurethane (PU) prepolymers, which were synthesized from polyether [poly(tetramethylene glycol)] diol, 4,4′‐diphenylmethane diisocyanate, and a coupling agent, bisphenol‐A (Bis‐A), 4,4′‐diaminodiphenyl sulphone (DDS), or benzophenonetetracarboxylic dianhydride, were used to modify the toughness of Bis‐A diglycidyl ether epoxy resin cured with DDS. Besides the crystalline polymers, poly(butylene terephthalate) (PBT) and poly(hexamethylene adipamide) (nylon 6,6), with particle sizes under 40 μm were employed to further enhance the toughness of PU‐modified epoxy at a low particle content. As shown by the experimental results, the modified resin displayed a significant improvement in fracture energy and also its interfacial shear strength with polyaramid fiber. The hydroxyl‐terminated PU was the most effective among the three prepolymers. The toughening mechanism is discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by the scanning electron microscopy revealed that the modified resin had a two‐phase structure. The fracture properties of PBT‐particle‐filled epoxy were better than those of nylon 6,6‐particle‐filled epoxy. Nevertheless, the toughening effect of these crystalline polymer particles was much less efficient than that of PU modification. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2903–2912, 2001     

Effect of rubber/matrix interfacial modifications on the properties of a rubber-toughened epoxy resin

The interface of a rubber-toughened epoxy resin was modified by using epoxide end-capped carboxyl-terminated butadiene and acrylonitrile random copolymer (CTBN). The end-capping epoxides were formulated with different ratios of flexible diglycidyl ether of propylene glycol (DER732) and rigid diglycidyl ether of bisphenol-A (Epon 828). The microstructure and the fracture behavior of these rubber-modified epoxy resins were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The thermal and mechanical properties were also investigated. With an increase in the amount of end-capping DER732, the interfacial zone of an undeformed rubber particle and the degree of cavitation of the rubber cavity on the fracture surface were greatly increased. At the maximal addition of DER732, fracture energy (GIc) for this toughened epoxy resin containing 10phr CTBN rubber increases up to 2.4 fold compared to that of a conventional CTBN-toughened epoxy resin, but the thermal and the mechanical properties remained quite unaffected. The modification on the interfacial property provides a new technique in the improvement of fracture toughness of a rubber-toughened epoxy resin.     

Epoxidized natural rubber/epoxy blends: Phase morphology and thermomechanical properties

Epoxidized natural rubbers (ENRs) were prepared. ENRs with different concentrations of up to 20 wt % were used as modifiers for epoxy resin. The epoxy monomer was cured with nadic methyl anhydride as a hardener in the presence of N,N‐dimethyl benzyl amine as an accelerator. The addition of ENR to an anhydride hardener/epoxy monomer mixture gave rise to the formation of a phase‐separated structure consisting of rubber domains dispersed in the epoxy‐rich phase. The particle size increased with increasing ENR content. The phase separation was investigated by scanning electron microscopy and dynamic mechanical analysis. The viscoelastic behavior of the liquid‐rubber‐modified epoxy resin was also evaluated with dynamic mechanical analysis. The storage moduli, loss moduli, and tan δ values were determined for the blends of the epoxy resin with ENR. The effect of the addition of rubber on the glass‐transition temperature of the epoxy matrix was followed. The thermal stability of the ENR‐modified epoxy resin was studied with thermogravimetric analysis. Parameters such as the onset of degradation, maximum degradation temperature, and final degradation were not affected by the addition of ENR. The mechanical properties of the liquid‐natural‐rubber‐modified epoxy resin were measured in terms of the fracture toughness and impact strength. The maximum impact strength and fracture toughness were observed with 10 wt % ENR modified epoxy blends. Various toughening mechanisms responsible for the enhancement in toughness of the diglycidyl ether of the bisphenol A/ENR blends were investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39906.     

“核-壳”型硅橡胶对聚碳酸酯回收料的增韧及阻燃改性研究

采用"核-壳"型硅橡胶对聚碳酸酯(PC)回收料进行增韧及阻燃改性,考察了该共混体系的力学性能、阻燃性能、断裂面形貌及热稳定性。研究表明:两相不相容导致"核-壳"型硅橡胶与PC回收料共混没有增韧效果。只有添加环氧树脂或苯乙烯-马来酸酐共聚物作为增容剂,其缺口冲击强度才能获得大幅提高。冲击断裂面形貌观察显示:增容剂能有效提高"核-壳"型硅橡胶的聚甲基丙烯酸酯壳与PC基体间的界面黏结性,降低两相表面张力,使硅橡胶粒子在基体中获得单分散分布,这是取得优异增韧效果的关键因素;并根据实验结果分析了增韧机理。"核-壳"型硅橡胶不仅可以有效地增韧PC回收料,也能显著提高其阻燃性能。在共混物燃烧过程中,硅橡胶能迅速迁移到PC表面,形成高阻燃性的炭保护层;同时在PC基体与硅橡胶之间形成交联结构,从而对PC回收料产生阻燃作用。因此,添加质量分数为7%的"核-壳"型硅橡胶和3%的增容剂,就可使PC回收料的阻燃级别达到UL94V-0级。     

新型环氧树脂软模的制备

以聚醚改性硅油为相容剂,硅橡胶和环氧树脂(EP)混合固化制备了具有较高强度和良好脱模性能的EP软模。红外光谱(FT-IR)分析表明聚醚改性硅油的合成物中含有聚醚与硅油基团,说明反应能够顺利进行;在聚醚改性硅油作用下,硅橡胶与EP具有良好的相容性,并可通过增减硅橡胶的用量来调节模具的强度,同时模具的使用寿命显著增加,使用次数至少为硅橡胶模具的100倍;硬脂酸锌的加入使模具的表面张力降低,脱模性能明显提高,并且已达到菱镁制品的脱模要求。当硅橡胶的质量分数为30%时,加入20%的硬脂酸锌可使模具的表面张力降至24.83×10-5 N/cm。     

The Effect of Modification of an Epoxy Resin Adhesive with ATBN on Peel Strength

The effects of rubber content, rate of peel and temperature on peel strength of ATBN modified DGEBA based epoxy resin adhesives have been investigated. The fracture surfaces of peel test specimens and the distribution of rubber particles in cured bulk epoxy resin have been observed with SEM and TEM, respectively. The mechanical properties of bulk rubber modified epoxy resin have been also measured. The peel strengths increased with increasing rubber content, peel rate, and decreasing temperature. The peel strengths were superposed as a function of rate and temperature. Plots of the shift factors against temperature gave two straight lines, which followed an Arrhenius relationship. The region of temperature below the intersection of the two straight lines, temperature somewhat lower than T_g of epoxy adhesive, gave markedly high peel strengths and a stick-slip failure due to plastic deformation of the adhesive, and a number of micro holes produced by the rupture of rubber micro particles on the fracture surface. The region of temperature above the intersection gave lower peel strengths and an apparent interfacial failure with ductile fracture of the adhesive, and larger, shallow holes or no holes. From these results, the marked increase of peel strength was concluded to be mainly attributed to the plastic or viscoelastic deformation of epoxy matrix, the strong bond at the interface between rubber particles and epoxy matrix, and the dilation and rupture of a number of rubber particles.     

Effects of nanotube modification on the dielectric behaviors and mechanical properties of multiwall carbon nanotubes/epoxy composites

Multiwall carbon nanotubes (MWNTs) were modified by three methods, namely, oxidizing the tubes and opening both ends, filling the tubes with Ag, and grafting the tubes with hexamethylene diamine. Modified MWNTs/epoxy composites were prepared by melt‐mixing epoxy resin with the tubes. Transmission electron microscope images showed that the modified MWNTs can be dispersed in the epoxy matrix homogeneously. The dielectric behaviors and mechanical properties of the composites were investigated. The dielectric and mechanical properties of the modified MWNTs/epoxy composites were considerably improved compared with those of the epoxy matrix. The tensile strengths of the Ag‐filled, opened, and grafted MWNTs composites at the same filler content of 1.1 wt% were higher by ～30.5%, 35.6%, and 27.4%, respectively, than that of neat epoxy. The Izod notched impact strength of the grafted MWNTs/epoxy composite with filler content of 1.1 wt% was approximately four times higher than that of neat epoxy. A dielectric constant of ～150 of the composite with 1.1 wt% Ag‐filled nanotubes was observed in the low‐frequency range, which was ～40 times higher than that of the epoxy matrix. The proper modification of nanotubes provides a way to improve the properties of the polymer‐based composites. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

LED封装用改性环氧树脂研究进展

传统的LED环氧树脂封装材料存在脆性大、耐冲击性差、容易老化、透光率低、折射率低等缺陷,限制了其在LED封装产业中的应用,通过环氧树脂改性可弥补其作为LED封装材料的缺陷。本文综述了近年来LED环氧树脂封装材料在高折射率、光稳定、抗黄变、有机硅改性方面的研究进展,并展望了LED改性环氧树脂封装材料的发展前景。     

Effects of rubber‐rich domains and the rubber‐plasticized matrix on the fracture behavior of liquid rubber‐modified araldite‐F epoxies

The fracture behavior of a bisphenol A diglycidylether (DGEBA) epoxy, Araldite F, modified using carboxyl‐terminated copolymer of butadiene and acrylonitrile (CTBN) rubber up to 30 wt%, is studied at various crosshead rates. Fracture toughness, K_IC, measured using compact tension (CT) specimens, is significantly improved by adding rubber to the pure epoxy. Dynamic mechanical analysis (DMA) was applied to analyze dissolution behavior of the epoxy resin and rubber, and their effects on the fracture toughness and toughening mechanisms of the modified epoxies were investigated. Scanning electron microscopy (SEM) observation and DMA results show that epoxy resides in rubber‐rich domains and the structure of the rubber‐rich domains changes with variation of the rubber content. Existence of an optimum rubber content for toughening the epoxy resin is ascribed to coherent contributions from the epoxy‐residing dispersed rubber phase and the rubber‐dissolved epoxy continuous phase. No rubber cavitation in the fracture process is found, the absence of which is explained as a result of dissolution of the epoxy resin into the rubber phase domains, which has a negative effect on the improvement of fracture toughness of the materials. Plastic deformation banding at the front of precrack tip, formed as a result of stable crack propagation, is identified as the major toughening process.     

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     

Fracture Behaviour of Thermoplastic Modified Epoxy Resins

This work has shown that the addition of polyetherimide (PEI) can significantly increase the toughness of highly cross-linked epoxy resins, whilst retaining a high T_g and modulus. These combined properties indicate the potential of PEI modified epoxy resins for use as matrices for advanced composite materials. In terms of G_IC, addition of 20wt% PEI raised the toughness by a factor of eight. Evidence from SEM fracture surfaces suggests that the toughening mechanism operating in bulk PEI modified epoxy resin is ductile drawing of the PEI. Carbon fibre composites based on 30wt% PEI modified epoxy resin matrices show considerable improvement in toughness at low and high strain rates when compared with CFRP possessing unmodified or 20wt% modified PEI content epoxy resins.     

Preparation of high-performance epoxy-containing silicone rubber via hydrosilylation reaction

A novel epoxy-containing silicone rubber network was constructed by hydrosilylation reaction among the synthesized vinyl-containing epoxy resin prepolymers, vinyl terminated silicone oil and hydrogen-containing silicone oil. The structure of the vinyl-containing epoxy resin prepolymers was characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy. Morphology observations revealed that uniform “sea-island” phase separation structure was present in modified silicone rubbers. The compatibility between silicone rubber and epoxy resin was enhanced, thanks to the good dispersion of vinyl-containing epoxy prepolymers in silicone rubber matrix. The adhesion and tensile properties of modified silicone rubbers were greatly enhanced when compared with those of unmodified counterparts. The thermal degradation behavior of cured silicone rubbers was studied using thermogravimetric analysis and thermogravimetric/infrared spectrometry analysis. Results showed that the formation of epoxy-containing silicone rubber network altered the degradation process of silicone rubber, thereby yielding a higher residue at 800 °C under nitrogen atmosphere. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48397.     

PP-硅橡胶-LLDPE三元共聚物的合成及性能研究

以聚丙烯(PP)为基体树脂,硅橡胶为增韧剂,线性低密度聚乙烯( LLDPE)为辅增韧剂,制备了一系列的PP/硅橡胶LLDPE的三元共聚物,考察了PP填充不同配比的硅橡胶共混物的力学性能.结果表明,随着硅胶含量不断的增加,样条的断裂伸长率,弹性模量,冲击强度逐渐增加,样条的拉伸强度随着硅胶的增加而逐渐减少;LLDPE的加入量为15％时,PP/硅橡胶/LLDPE的三元共混体系力学性能最佳;硅橡胶的加入量为20％时,PP/硅橡胶/LLDPE的三元共混体系具有良好的拉伸性能和冲击强度.     

Modification of epoxy resins with acrylic rubbers containing a pendant epoxy group

New acrylic rubbers with a pendant epoxy group were prepared by copolymerization of butyl acrylate (BA) with vinylbenzyl glycidyl ether (VBGE). The modification of an epoxy system (bisphenol-A diglycidyl ether/p,p′-diaminodiphenyl sulfone) with the acrylic rubbers was carried out in order to increase the toughness of the cured epoxy resin. The addition of 20 wt.-% of the copolymer containing 74% of BA and 26% of VBGE units resulted in a 30% increase in the fracture toughness (K_IC) of the cured resin at minimal expenses of strength and modulus of the resin. The modified epoxy resin had two-phase morphology in which the rubber particles with average diameter of 2 μm are dispersed in the epoxy matrix. The copolymer without the pendant epoxy group, prepared from BA and vinylbenzyl methoxyethyl ether, was ineffective as a modifier, indicating that the reaction of the pendant epoxide with the epoxy matrix resulted in good interfacial adhesion between the rubber particles and the matrix, and in the increased toughness. The epoxide-containing copolymers with 55 or 86% of BA units were also insufficient modifiers. The addition of the former yielded cured resins with homogeneous structure, whereas that of the latter resulted in macroscopic phase separation between the rubber and the epoxy resin.     

MP填充型膨胀阻燃硅橡胶复合材料的制备及其动态燃烧行为

采用α,ω-二羟基聚二甲基硅氧烷(107胶)、气相白炭黑、自膨胀阻燃剂三聚氰胺磷酸盐(MP)等制备了阻燃脱醇型室温硫化硅橡胶(RTV),研究了MP用量对脱醇型RTV硅橡胶阻燃性能、动态燃烧性能和机械性能的影响,以及MP阻燃脱醇型RTV硅橡胶的热稳定性。用扫描电镜(SEM)考察了MP在RTV硅橡胶的分散情况。结果表明,当MP的用量达50份以上时,脱醇型RTV硅橡胶才具有良好的阻燃性能。但随着MP用量的增加,脱醇型RTV硅橡胶的初始分解温度下降。另外,MP能很均匀地分散在RTV硅橡胶中,使MP添加量增加到50份时其拉伸强度、断裂伸长率也没有受到严重破坏。