电子束辐射固化环氧树脂的动态力学分析——树脂化学结构、分子量及其分布的影响

应用不同化学结构、分子量及其分布的环氧树脂进行了电子束辐射固化实验 ,对固化物进行了动态力学分析 ,研究了不同样品凝胶含量、内耗tanδ及动态模量的变化规律 .分析结果表明环氧树脂辐射反应活性与其化学结构有很大关系 ,酚醛型环氧树脂的辐射反应活性高 ,固化后高温模量及玻璃化温度较高 ,而脂环族环氧树脂反应活性小 .在低辐射剂量下 ,环氧树脂的固化度随分子量增大略有下降 ,但固化物的玻璃化温度随分子量增加而升高 .增大辐射剂量 ,树脂固化度的提高受分子量大小的影响很小 ,分子量较大样品的网络均匀程度有所提高 ,在较高反应程度下 ,玻璃化温度主要受固化度影响 .树脂固化程度也是决定其模量高低的主要因素 ,而在固化程度相近的情况下 ,分子量的影响作用很大 .在同样辐射剂量下 ,分子量分布宽的树脂固化反应程度高 ,但交联网络均匀性低 .     

Alkoxysilane functionalized polycaprolactone/polysiloxane modified epoxy resin through sol-gel process

Incorporating elastic polysiloxane and/or an inorganic silica network in epoxy resin could result in the enhancement of physico-chemical properties due to the existence of Si-O bonds. To improve the compatibility between polysiloxane and epoxy matrices and intensively strengthen the properties of the modified system, here polysiloxane was introduced into epoxy resin through compatibilizing epoxy-immiscible polysiloxane with epoxy-miscible polycaprolactone segments via a sol-gel process. To fulfill the process, a blend containing alkoxysilane-functionalized polycaprolactone/polydimethylsiloxane (PCS-2Si) was firstly synthesized using direct nucleophilic addition between -OH groups of polydiol and -NCO of a silane. And then a series of modified epoxy resins were prepared in different epoxy/PCS-2Si weight ratios. All the modified composites were characterized by conventional methods, and their morphological, thermal degradation and surface properties were studied. The results showed that increasing the PCS-2Si content caused the changes of miscibility between epoxy and polysiloxane. Also, the thermal stability of the modified composites was greatly improved. As for the temperature value at 5% weight loss, it reached to 308.5 °C for the composite containing 50-60% (wt%) PCS-2Si, over 150 °C higher than that for neat amine-cured epoxy resin. Similarly, the modified composites showed good hydrophobicity. The improvement of these properties came from the improved interaction between PCS-2Si and epoxy, the forming of Si-O-Si network and the enrichment of siloxane chains on the surface of films. Therefore, it is believed that this modified epoxy appears promising as new high performance and highly functional materials.     

环氧氯丙烷修饰的对位和间位芳纶涂覆剂研究

制备了具有环氧丙基侧链的对位芳纶(PPTA-ECH)和间位芳纶(PMIA-ECH),并将其用做对位芳纶(PPTA)织物/环氧树脂复合材料中PPTA织物的涂覆剂。采用场发射扫描电子显微镜(FE-SEM)及XPS等方法对PPTA织物表面的PPTA-ECH涂层结构进行了表征。考察了PPTA-ECH和PMIA-ECH涂覆的PPTA织物/环氧树脂复合材料的层间剪切强度和面内剪切强度,并与未经涂覆的PPTA织物复合材料的性能作比较。结果表明,PPTA-ECH和PMIA-ECH可显著改善PPTA织物和环氧树脂之间的界面性能。涂覆了PPTA-ECH及PMIA-ECH的PPTA织物/环氧树脂复合材料的层间剪切强度(ILSS)比未经涂覆的复合材料分别提高了26.20%和14.76%,面内剪切强度(ISS)分别提高了26.98%和11.86%。由于PPTA-ECH对PPTA纤维具有更强的亲和能力,因此PPTA-ECH在层间剪切强度和面内剪切强度方面的增强效果均优于PMIA-ECH。对PPTA-ECH在PPTA纤维表面铺展与吸附及对复合材料的增强机理也进行了初步探讨。作为新型涂覆剂,PPTA-ECH在对位芳纶复合材料的开发应用方面具有潜在的应用前景。     

Adhesives and coatings based on phenolic/epoxy resins

Low molecular weight epoxy resin based on bis (4‐hydroxy phenyl) 1,1 cyclohexane was prepared and modified with various types of the prepared phenolic resins. Phenol–, cresol–, resorcinol–and salicylic acid–formaldehyde resins were used. The optimum conditions of formulation and curing process were studied to obtain modified wood adhesives characterized by high tensile shear strength values. This study indicated that the more suitable conditions are 1:2 weight ratio of phenol–or cresol–formaldehyde to epoxy resin in the presence of phthalic anhydride (20 wt%) of the resin content as a curing agent at 150°C for 80 min. Resorcinol–or salicylic acid–formaldehyde/epoxy resins formulated at 1:2 weight ratio were cured in the presence of paraformaldehyde (20 wt%) at 150°C for 60 min. The effect of the structure of phenolic resins on the tensile shear strength values of formulated resin samples, when mixed with the epoxy resins and cured under the previously mentioned optimum conditions for different times, was investigated. Metallic and glass coatings from the previous resins were also prepared and evaluated as varnishes or paints. Copyright © 1999 John Wiley & Sons, Ltd.     

电子束固化环氧树脂的物理特征及其分析

分析了环氧树脂电子束辐射固化的物理特征 ,电子束辐射固化过程受活性中心扩散控制 ,整个固化区域由片层状结构组成 .与电子能量沉积分布相对应 ,环氧树脂辐射固化度的最高值是在一定深度而不是在辐射表面出现 .对电子束辐射环氧树脂体系的固化过程进行了模型解释 ,固化区域大小主要由电子的能量传递范围和浓度决定 ,反应活性中心的扩散作用影响较弱     

Nano- and micro-structured random copolymer modified cycloaliphatic epoxy resins for use as light-emitting diode encapsulation

Poly(2,2,3,4,4,4-Hexafluorobutylmethacrylate–random–glycidolmethacrylate) random copolymer (P(HFBMA-r-GMA)) was synthesized via free radical polymerization. The novel reactive random copolymer was incorporated to modify cycloaliphatic epoxy resins and obtain the nano- or micro- structured composites. The chemical structures of P(HFBMA-r-GMA) were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The morphology and light transmittance of the cured epoxy resins were observed by scanning electron microscopy (SEM), transmission electron microscope (TEM) and ultraviolet-visible spectrophotometry (UV-vis), respectively. It is indicated that the optical transmittance of composites were basically kept although the microphase separation occurred in the curing process, which has a profound influence on the mechanical properties and refractive indexes. The thermal properties, surface dewettability and water absorbency of the cured epoxy resins were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle measurement and immersion test respectively. The experimental results revealed that the values of glass transition temperatures (Tg), surface dewettability and water resistance were effectively improved by the high cross-linking density and the enrichment of the fluorinated random copolymer dispersing in the composites. With respect to the corresponding properties of the neat epoxy resin, P (HFBMA-r-GMA)-0.25 hybrimer embraced the relatively good comprehensive properties, making the modified epoxy resins as good candidates for LED encapsulation.     

Effect of internal mold release agent on flexural and inter laminar shear properties of carbon and glass fabric reinforced thermoset composites

The study is focused on thermoset composites reinforced with carbon and glass woven fabrics. Two types of thermoset resins, for example, epoxy and vinyl ester were used as the matrix. Varying concentrations of internal mold releasing (IMR) agent was used in the resin. The composites were cured both at room temperature and at 80°C. The flexural properties were studied using 3‐point bending test method. Further theinter‐laminar shear strength (ILSS) was investigated using the short beam shear strength test based on 3‐point bending. The flexural modulus of room temperature cured epoxy resin is higher than that of high temperature cured epoxy resin and cured vinyl ester resin. The flexural modulus is lowest for 1% IMR sample in epoxy system and the modulus for 0% and 2% epoxy are not significantly different. Lowest flexural strength and modulus can be observed for the combination of reinforcement and curing conditions for samples containing 1% IMR for the epoxy systems. Carbon fiber is found to be less compatible with the vinyl ester resin system and the addition of IMR to the resin degraded the properties further. Inter‐laminar shear strength for epoxy‐based composites is not much affected by presence of IMR, but in case of vinyl ester based composites there is a decrease in ILSS on addition of IMR agent. The study explains variation in flexural properties on addition of IMR and change of curing conditions. These results can be used for ascertaining variation in mechanical properties in real use.     

The dynamic mechanical behavior of random-in-plane short fiber-reinforced epoxy resin composites

In the present paper, the dynamic mechanical properties of random-in-plane short fiber-reinforced epoxy resin composites were studied by using a rheometrics solids analyzer. The three-point bend testing of the four composites (glass fiber/913 epoxy resin, glass fiber/924 epoxy resin, carbon fiber/913 epoxy resin and carbon fiber/924 epoxy resin) was carried out over temperatures from −100°C to 200°C at a frequency of 10 Hz and strain 0.05%. The composites based on 924 epoxy resin, which has been designed specially for high temperature applications, have less energy loss than the 913 epoxy resinbased composites. For the same resin, the carbon fiber-reinforced composites have less energy loss than the glass fiber-reinforced composites. All the composites have less energy loss than their corresponding matrices; the greater the fiber content, the lower the energy loss. The beta transition of 913 epoxy resin has been shifted to a higher temperature after being reinforced. It was shifted from −50°C to −30°C after being reinforced with glass fiber and made a diffuse shoulder-like peak commencing at −30°C after being reinforced with carbon fiber. The 924 epoxy resin has undergone the same change in beta transition as the 913 resin, though to a smaller extent. The phenomenon suggested that interactions between the macromolecules of the epoxy resins and the molecules along the fiber's surface.     

Oligo-fluoropolymer Modified Cycloaliphatic Epoxy Resins with Excellent Compatibility,Waterproof and Mechanical Properties for LED Encapsulation

An oligo-fluoropolymer(PFM) with functional cycloaliphatic epoxy and fluorinated groups was obtained via free radical polymerization and applied to the modification of cycloaliphatic epoxy resins(CE). The chemical structure of PFM was characterized by Fourier transform infrared(FTIR) spectroscopy, gel permeation chromatography(GPC) and nuclear magnetic resonance(NMR) spectroscopy, and the effects of different PFM concentrations(0.5%—6%, mass fraction) on the thermal resistance, mechanical properties, surface dewettability, light transmission, refractive index and various cured polymer properties were studied in detail. The DSC and TGA results demonstrate that the modified epoxy resins possess a higher thermal resistance than the neat epoxy resin. The improvements in the surface dewettability and water resistance are caused by the high crosslinking density and the enrichment of the oligo-fluorinated random copolymers dispersed in the matrix. The fracture surface morphologies of the thermosets were investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). It was observed that the optical transmittance of the composites was maintained even though microphase separation occurred during the curing process. With respect to the corresponding properties of the neat epoxy resins, the 2 phr(parts per hundreds of resin) PFM thermoset exhibited relatively better comprehensive properties, making the cured material a good candidate for light-emitting diode(LED) encapsulation.     

Thiirane functional spherosilicate as epoxy resin modifier

Epoxy resin-based composites, also those containing POSS compounds, have been the subject of extensive research because of their attractive properties and broad practical applications. However, in some applications they suffer from too long curing times or not strong enough adhesion to metals. A solution to this problem is the use of episulfide (thiirane) derivatives or their combination with epoxies. In this paper, the synthesis of new octakis[(3-(thiiran-2-yloxy)propyl)dimethylsiloxy]octasilesquioxane from its 3-glycidoxypropyldimethylsiloxy analog is described. Results of study of its influence on thermal properties as well as curing processes of modified with this compound epoxy resins hardened with maleic, phthalic, and pyromellitic anhydrides are also presented. It is shown that addition of this new thiirane functional POSS compound can significantly increase thermal stability of obtained epoxy resin composites and decrease its curing temperatures.     

Preparation and Characterization of DGEBA/EPN Epoxy Blends with Improved Fracture Toughness

The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied.One of the resins was a bifunctional epoxy resin based on diglycidyl ether ofbisphenol A and the other resin was a multifunctional epoxy novolac resin.Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples.The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin.The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples.The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples,probably due to enhanced cross-link density and molecular weight.Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples.The epoxy blends exhibited significantly higher fracture toughness (by 23％ at most) compared with the neat samples.The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.     

Recent advances in epoxy resins and composites derived from lignin and related bio-oils

This short critical review gives an insight on the potential that lignin and its bio-oils present towards the production of thermosetting epoxy polymers and composites. Green and sustainable ways of producing monomers and polymers from renewable sources are critical and lignin, as an underutilized bio-based waste material, presents a high exploitation potential. Due to its versatile and highly functional phenolic structure, the utilization of lignin or its depolymerized fractions (bio-oils) has been investigated in the last years as alternative for fossil-based epoxy resin pre-polymers and crosslinkers. Lignin can in fact be considered as a crosslinker for epoxy resins, especially after appropriate functionalization with amine groups or with additional hydroxyl groups, or it can be modified with epoxide groups towards the replacement of toxic BPA-based epoxy prepolymers. Furthermore, lignin derived pyrolysis or hydrogenolysis bio-oils may offer highly reactive soluble oligomers that after appropriate functionalization could be utilized as bio-based epoxy prepolymers. The lignin-based epoxy resins and composites exhibit similar or even better and novel properties, compared to those of pristine epoxy polymers, thus rendering lignin a highly valuable feedstock for further utilization in the thermoset polymer industry.     

化学改性环氧树脂水基涂料的研究——涂膜性能

用对氨基苯甲酸改性环氧树脂 ,使其具有亲水亲油两亲性质 ,测定了改性产物和纯环氧树脂共混物的玻璃化转变温度 ,结果显示两者能够相容 ,并以改性产物及其与纯环氧树脂的混合物制备水基涂料 ,测定了涂膜的物理和化学性能。结果表明 ,涂膜性能优良 ,保持了溶剂型环氧涂料的抗冲击强度、光泽度和硬度等方面的优点 ,而附着力提高 ,同时柔韧性大为改善 ,涂膜耐水性和耐化学药品性能优良。     

Preparation and properties of aniline chain-extended thermoplastic epoxy resin using triphenylphosphine as catalyst

Thermoplastic resins have been widely used in fiber reinforced polymer composites because of its recyclability and short cycle times. However, the high viscosity after heating and melting restricts its infiltration on the surface of fiber. In this study, a series of thermoplastic epoxy resins were prepared via the chain extension reaction of epoxy groups with liquid aniline using triphenylphosphine (TPP) as catalyst. The relationship between polymer network structure and performance was comprehensively investigated. The solubility tests indicated that excessive aniline or TPP facilitated the crosslinking of resins. Besides, on the premise of thermoplasticity, appropriate TPP could increase the degree of chain extension, molecular weight, and glass transition temperature of resins. Furthermore, the in-situ polymerization process facilitated infiltration between epoxy resin and the fibers before chain extension reaction. The bending test showed that the flexural performance of the sample with 2 phr of TPP was improved by 38.8%. Therefore, this work provides a feasible method to prepare the thermoplastic epoxy resins and its fiber-reinforced composites with good mechanical properties.     

羧基化环氧丙烯酸酯合成及在光成像阻焊油墨中的应用

树脂;多元羧酸酐;光固化;碱显影;羧基化环氧丙烯酸酯合成及在光成像阻焊油墨中的应用     

Linseed oil‐based reactive diluents preparation to improve tetra‐functional epoxy resin properties

Two kinds of bio‐resourced reactive diluents have been synthesized from linseed oil. The prepared epoxidized linseed oil (ELO) and the cyclocarbonated linseed oil (CLO) were separately blended with a petroleum‐based tetra‐functional epoxy resin (TGDDM) to improve its processability and to overcome the brittleness of the thermoset network therefrom. The linseed oil modifications were spectrally established, and processability improvement of the resin blends was rheologically confirmed. The curing of samples was studied by differential scanning calorimetry, and their mechanical properties (ie, tensile, flexural, fracture toughness, and adhesion) were investigated as well. Scanning electron microscopy images were obtained to reconfirm the toughness improvement of the modified thermosets. In contrast of the epoxidized soybean oil (ie, the most conventionally studied bio‐based reactive diluent), ELO and CLO had no negative effects on the thermoset material characteristics. They improved properties such as tensile strength (up to 43.2 MPa), fracture toughness (1.1 MPa m^1/2), and peel‐adhesion strength (4.5 N/25 mm). It was concluded that ELO and CLO were efficient reactive diluents to be used in formulations of polymer composites, surface coatings, and structural adhesives based on epoxy resins.     

环氧树脂水基化化学改性的研究

用对氨基苯甲酸改性环氧树脂 ,使其成为具有亲水性的树脂。测定了改性树脂的溶解性 ,发现改性后树脂在有机溶剂中的溶解性能变差 ,但在碱性溶剂中溶解性增强。对改性树脂进行了红外光谱表征 ,并根据环氧基特征峰的吸收对环氧基转化率进行了定量分析。测定了改性产物的DSC曲线 ,发现随着反应物中对氨基苯甲酸比例的提高 ,改性产物的玻璃化转变温度升高。涂膜的性能测试表明 ,对氨基苯甲酸改性环氧树脂水基涂料的机械力学性能和耐化学试剂性能比溶剂型纯环氧树脂要优越。     

Mechanical and thermal properties of (Ag/C nanocable)/epoxy resin composites

A novel Ag/C nanocable and epoxy resin composite was obtained by compounding Ag/C nanocables and epoxy resin. The nanocable is composed of a nanowire (core) wrapped with one or more outer layers (shell). Scanning electron microscopy images proved that the nanocables consisted of a silver nanowire core and a carbon outer shell. The Ag/C nanocables were modified by hyperbranched poly (amine ester) to improve their mechanical properties for further application. We separately compounded raw and modified Ag/C nanocables with epoxy resin, and then tested the thermal performance, tensile properties, and fracture morphology of each composite. We found that the tensile strengths of the two composite systems were enhanced by the epoxy resin, with the modified (Ag/C)/epoxy resin composite system improving more significantly. Differential scanning calorimeter (DSC) results showed that the glass transition temperature of the unmodified (Ag/C)/epoxy resin composite is increased when the Ag/C nanocable is filled, while that of the modified system slightly decreased. Fracture morphology results showed that both (Ag/C)/epoxy composite systems featured increased toughness. The modified Ag/C nanocables had better compatibility with the epoxy resin. The relationship between the properties and microstructure of the composites were discussed in detail to explain the mechanism behind the observed changes in material properties.     

对-氨基苯甲酸改性环氧树脂的性能表征及乳化性质

以对氨基苯甲酸改性环氧树脂,使其成为具有亲水性的树脂.实验结果表明,改性后树脂在有机溶剂中的溶解性变差,在碱性溶剂中溶解性增强.对改性树脂进行了红外表征,并根据环氧基特征峰的吸收对环氧基转化率进行了定量分析.测定了改性产物的DSC曲线,发现随着反应物中对氨基苯甲酸比例的升高,改性产物的玻璃化转变温度升高.此外还研究了改性环氧树脂水基微乳液制备过程的电导率变化规律,并探讨了羧酸基中和程度及溶剂极性对乳液粒径以及粒子形态的影响.     

聚苯基硅氧烷与聚甲基苯基硅氧烷改性环氧树脂的合成与性能比较

热熔法制备了一系列聚苯基甲氧基硅氧烷(PPMS)、聚甲基苯基甲氧基硅氧烷(PMPS)改性环氧树脂,通过环氧值、红外光谱(IR)分析表明聚硅氧烷接枝了E-20环氧树脂且环氧基保持不变.探讨了有机硅含量对改性树脂固化体系耐热性能及韧性的影响.实验表明,当E-20环氧树脂与PPMS、PMPS的质量比为7∶3时,改性树脂固化体系的耐热性能明显提高,玻璃化转变温度(Tg)为95.8、88.3℃,分别比改性前提高了9.0℃和1.5℃;质量损失50%时的热分解温度(Td)为476.5、487.8℃,分别比改性前提高了58.3℃和69.5℃.与ED-30固化体系相比,EPMS-30固化物的耐热性能,韧性等力学性能提高的更加明显,并且还具有优良的涂膜性能.