Studies on the cure kinetics and networks properties of neat and polydimethylsioxane modified tetrafunctional epoxy resins

The cure kinetics of tetrafunctional epoxy resins with three different backbone structures and their modification by polydimethylsioxane (PDMS) were studied by means of differential scanning calorimetry with dynamic approach. The development of epoxy networks was characterized by dynamic viscoelastic measurements. Results showed that all the epoxy resins obeyed the autocatalytic reaction mechanism with a reaction order of about 3. Epoxy resin with softer aliphatic backbone demonstrated a higher cure reactivity and stronger tendency towards autocatalysis, as well as lower crosslinking density. The PDMS‐modified epoxy resins showed higher early cure reactivity and a lower crosslinking density due to the plasticization and restriction effect of the dispersed PDMS phase, respectively. Based on cure kinetics and dynamic viscoelastic results, the α_m was found to be an effective precursor for describing the developing of epoxy networks during the course of cure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of tetrafunctional epoxy resins and their modification with polydimethylsiloxane for electronic application

High-performance tetrafunctional epoxy resins were synthesized by reacting a suitable tetraphenols which were obtained by the condensation of appropriate dialdehyde with phenol followed by epoxidation with a halohydrin. The structure of the synthesized tetraphenols was confirmed by infrared (IR), mass spectra (MS), and nuclear magnetic resonance (NMR) spectroscopy. Dispersed silicone rubbers were used to reduce the stress of the synthesized tetrafunctional epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The dynamic viscoelastic properties and morphologies of neat rubber-modified epoxy networks were investigated. The thermal mechanical properties and moisture absorption of encapsulants formulated from the synthesized tetrafunctional epoxy resins were also studied. The results indicate that a low-stress, high glass transition temperature (T_g), and low-moisture-absorbing epoxy resin system was obtained for semiconductor encapsulation application. © 1996 John Wiley & Sons, Inc.     

Fracture and mechanical properties of epoxy resins and rubber-modified epoxy resins

Fracture and mechanical property data on a wide range of epoxy resin systems are presented. The extent to which toughening can be induced by heterophase rubber inclusions depends more on the curing agent used than on the resin component. The greatest improvements in toughness were obtained by rubber modification of epoxy resins cured with an anhydride. A preformed ABS polymer can be used to toughen many epoxy resin systems. With one major exception (where a large improvement was found) only small changes in tensile properties occur when small amounts of rubber are present.     

Synthesis, curing behavior and properties of siloxane and imide-containing tetrafunctional epoxy

A novel tetrafunctional epoxy resin containing siloxane and imide groups, i.e., N,N,N′,N′-tetraglycidyl-bis(4-aminophenyl)-5,5′ (1,1,3,3-tetramethyl-1,1,3,3-disiloxane-bisnorbornane-2,3-dicaroximide, was synthesized and characterized. The curing behavior of this resin and the properties of its cocured material with commercial tetraglycidyl meta-xylene (GA-240) was studied. Functional group changes during cocuring reactions were investigated with FTIR. Kinetic parameters were analyzed with dynamic DSC. Thermal properties were measured with TGA, TMA and DMA. Curing kinetics revealed that this novel tetrafuctinal epoxy indicated a lower activation energy and lower curing temperature than GA-240. The cocured materials, due to the presence of siloxane and imide groups in the polymer matrix, show higher glass transition temperature, better dimensional stability and toughness, and also enhanced properties than pure GA-240.     

Thermal and dielectric properties of epoxy resins

Epoxy resins were prepared using various molar ratios of epichlorohydrin and bisphenol-A and then cured with four different hardeners: diaminodiphenyl methane (DADPM), dithioterephthalic acid (DTTPH), dimethylamino propylamine (DMAPA) and diethylene triamine (DT). The thermal behaviour of these epoxy resins was studied. From the energy of activation data it was observed that DADPM gives the highest thermal stability of all these curing agents. Dielectric constant measurements of uncured resins were made at 30°C and at a frequency of 2.5 × 10³ Hz. The higher activation energies of the resins are related to the polarity of the hydroxyl moiety in the epoxy resins.     

Influence of oxidation treatment of carbon powders on the cure kinetics of amine cured tetrafunctional epoxy resins

A tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) type tetrafunctional epoxy resin containing carbon powders was cured with the stoichiometric amount of a tetrafunctional curing agent, namely m-phenylenediamine (mPDA). Carbon powders were oxidised with air or nitric acid. The influence of carbon powders on curing of the resin was followed by dynamic mechanical analysis, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Gelation and vitrification times were determined as a function of the variations of dynamic properties. The evolution of viscoelastic modulus during curing of the different mixtures showed that untreated carbon powder clearly accelerated the kinetics of curing whilst oxidation of carbon powders could remove their catalysing effect. These results were confirmed by monitoring the changes in conversion of epoxy and amine groups during cure using the FTIR technique. DSC experiments also showed the influence of carbon powder as a catalyst and the loss of the catalysing effect as a consequence of chemical treatment.     

木质素基环氧树脂的合成与应用

木质素是一种储量丰富的多酚类天然高分子材料,以木质素为原料合成的木质素基环氧树脂具有原料可再生、成本低、可降解等特点。本文从木质素直接环氧化以及通过酚化、酯化、丙氧基化等改性后再环氧化这2方面综述了木质素基环氧树脂的合成与应用,并对其未来的发展进行了展望。     

Synthesis and properties of phosphorus containing advanced epoxy resins

A series of advanced epoxy resins with various epoxy equivalent weights were synthesized from a reactive phosphorus‐containing diol, 2‐(6‐oxido‐6H‐dibenz[c,e][1,2]oxaphosphorin‐6‐yl)‐1,4‐dihydroxy phenylene and diglycidyl ether of bisphenol A and then cured with 4,4′‐diaminodiphenyl sulfone, phenol novolac, or dicyandiamide. The parameters of the polymerization reaction (such as reaction time, catalyst) are discussed in this article. Thermal properties of cured epoxy resins were studied using differential scanning calorimetry, dynamic mechanical analysis, and thermal gravimetric analysis. The flame retardancy of cured epoxy resins was tested by limiting oxygen index. The relations between thermal properties, flame retardancy, and epoxy equivalent weights were also studied. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 429–436, 2000     

环氧树脂改性有机硅聚合物的合成与应用性能研究

正硅酸乙酯水解可得有机硅聚合物,但产物分子量不高,成膜性差。用环氧树脂对其改性,制得物的涂膜成膜性优良,且大大缩短固化时间。研究了水解温度与时间,催化剂种类,溶剂用量和环氧树脂用量、反应温度与时间对改性物的影响。结果表明,水解温度50℃,时间3h,硫酸催化,乙醇用量35%,环氧树脂用量20%～50%,反应温度50℃,反应时间1h,涂膜性能优良。     

The effect of amine/epoxy ratio on the fracture toughness of tetrafunctional epoxy resin

Summary. The effect of amine/epoxy ratio on the fracture toughness (K_Ic) of tetrafunctional epoxy resin was investigated. K_Ic value was measured by single-edge notch-bend test. The K_Ic value of the tetrafunctional epoxy resin increased with increasing the amount of amine curing agent. This result was explained with the structural viewpoint of the epoxy network. The network structure of the tetrafunctional epoxy was analyzed with dynamic thermomechanical measurement and in-situ near IR technique. Received: 19 June 1997/Accepted: 17 Juli 1997     

Preparation and cured properties of novel cycloaliphatic epoxy resins

Preparation and characterization of novel cycloaliphatic epoxy resins, which are derived from octadienyl compounds, were studied. From a model peracetic acid epoxidation reaction using 2,7-octadienyl acetate-1, the structure of the liquid resins is estimated to be mainly terminal epoxides and some amount of inner epoxide depending on the epoxide content. The epoxy resins offer lower toxicity and lower vapor pressure. The reactivity of the resin with acid anhydrides is moderate but faster than that of traditional cyclohexane epoxide-type resins and slower than that of the glycidyl ester-type resins. This reactivity was also examined using model compounds. The heat deflection temperature of the hexahydro-phthalic anhydride-cured resins is shown to be directly proportional to the number of epoxy groups in the molecules. The flexural strength of the cured resins is nearly equivalent to that of the commercial resins, although the flexural elongation of the resins is larger than that of the rigid cyclohexane epoxide-type resins. The thermal stability of the cured resins is comparable to typical rigid cycloaliphatic resins; furthermore, high water resistance of the cured resins is suggested to be attributed to the hydrophobic character of the C₈ chain by cross-linking. © 1993 John Wiley & Sons, Inc.     

Synthesis and properties of cationic resins derived from polyether/polyester-modified epoxy resins

Four polyether and one polyester-modified cationic resins were synthesized by reacting polyether/polyester-modified epoxy resins with 2-ethylhexanol-blocked-toluene diisocyanate (2-EH-blocked TDI) and diethanolamine and subsequently neutralizing the resins with acetic acid. Four different polyethers and one polycaprolactone diol (PCP) were used to react with epoxy resin to form polyether-modified epoxy resins (1a–d) and polyester-modified epoxy resin (1e). The extent of reaction of epoxy resin and polyether or polyester was evaluated by the change of epoxy equivalent weight and the gel permeation chromatography curve of the resulting product. Cationic resins were dissolved in suitable solvents and were mixed with deionized water to form emulsions. Some factors, such as pH value of emulsion, solvent content, and applied voltage affecting the emulsion and electrodeposition properties, were investigated. Cationic resins, prepared from PPG (#1000)-modified epoxy resins, yielded a wider pH range of stable emulsion and also yielded deposited films with a pleasing appearance. PEG (#1000)-modified cationic resins produced a higher deposition yield, but higher throwing power was obtained by deposition of the PCP (#530)-modified cationic resins.     

水性环氧树脂的合成及其乳液的研究

使用环氧树脂6002分别与不同分子量的聚乙二醇(PEG1000或PEG2000)反应合成出自乳化型水性环氧树脂(WEP1000与WEP2000),并将其与环氧树脂6002按照不同的比例配制成乳液,再加入大分子聚胺类XCT-802固化剂组成水性环氧树脂黏合剂。考察了不同的WEP、用量及其他表面活性剂对环氧树脂6002乳液的稳定性以及固化物的黏接强度的影响。结果表明:当m(WEP1000):m(EP6002)=15:85、其含量为乳液的50%、预糊化淀粉为3%时配成的乳液具有良好的稳定性,且与大分子聚胺类XCT-802固化剂形成的固化物也具有最高的黏接强度。     

Synthesis and properties of cationic resins derived from aniline-modified epoxy resins and various amines

Aniline-modified epoxy resin which contains tertiary amine in the middle of the polymer chain was synthesized by the reaction of aniline and epoxy resin. The resulting aniline-modified epoxy resin and two commercial epoxy resins with different epoxy equivalent weights were reacted with 2-ethylhexanol-blocked toluene diisocyanate (2-EH-blocked TDI) to obtain thermally crosslinkable epoxy resins. These epoxy resins were subsequently reacted with various secondary amines and partially neutralized with acetic acid to give thermally crosslinkable cationic resins. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form emulsions. The crosslinking properties, emulsion, and electrodeposition properties of these resins were studied in some detail. The electro-deposition yields of the emulsions prepared from aniline-modified epoxy resins were higher than those of other emulsions. The crosslinked films prepared from aniline-modified epoxy resins were also glossier than those prepared from commercial epoxy resins. High deposition yield and high glossiness were the characteristic properties of the aniline-modified epoxy resins. Thermal properties were not affected by aniline-modified epoxy resins.     

氢化双酚A型环氧树脂合成工艺研究

以氢化双酚A(HBPA)和环氧氯丙烷(ECH)为原料,通过自制助催化剂与NaOH复配,按照醚化路线合成出氢化双酚A型环氧树脂.通过正交实验和单因素实验优化出最佳合成配方及工艺条件.采用核磁共振波谱表征其结构,并与BASF公司产品进行性能对比.     

The effect of urea bond on structure and properties of toughened epoxy resins

In this article, modified poly(oxypropylene) diamines were synthesized and used as a new flexible curing agent for epoxy resins. The purpose of modification is to introduce urea group into epoxy resins. The reaction rate, mechanical properties, glass transition temperature (T_g), and fracture surface morphology of these toughened epoxy resins were investigated. Because of urea groups, the reactivity between poly(oxypropylene) diamines and epoxy resins was significantly enhanced. At the same time, the urea groups resulted in strong intersegmental hydrogen bonding between modified poly(oxypropylene) chain, which reduced the compatibility of poly(oxypropylene) with epoxy resins and resulted in higher T_g of toughened epoxy. The modified sample had tensile strength of 15.8 MPa and ultimate elongation of 118% at room temperature, whereas the unmodified sample only had 6.2 MPa and 70%. The scanning electron microscope analysis showed that the modified system displayed tough fracture feature, whereas the unmodified system showed typical brittle fracture. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The studies of physical properties of dimeric fatty acid-modified thiodiphenyl epoxy resins

A thermally stable thiodiphenyl epoxy resin was modified with a dimeric fatty acid at an epoxy resin:fatty acid molar ratio of 4:1. The thermal and mechanical properties of the modified epoxy resin were studied by preparing an epoxy composition with an amine curing agent and a catalyst, followed by curing at 170 °C to produce a neat plastic epoxy resin. The tensile and impact strengths of the resin indicated improved flexibility and toughness compared to other epoxy resins. Enhanced toughness was confirmed by the increased lap shear strength in single lap joints prepared with steel substrates attached by the resin.     

Structure and properties relationships of epoxy resins part 1: Crosslink density of cured resin: (I) model resins synthesis

Two model epoxy resin precursors based on the N-glycidyl derivatives of 4.4'-diaminodiphenylene methane (DDM) were prepared: N,N bis-(2,3-epoxypropyl)-N′,N″-dimethyl-4.4'-diaminodiphenylene methane (G2A); N.N′ bis-(2,3-epoxypropyl)-N,N′-dimethyl-4,4'-diaminodiphenylene methane (G2S). To prepare these, aniline or N-methyl aniline was reacted with epichlorohydrin, using acetic acid as catalyst. The products were coupled via acid-catalysed condensations in the presence of formaldehyde or with N,N-dimethylaminobenzyl alcohol. The coupled chlorohydrins formed were then dehydrochlorinated to form the desired product. All reactions were monitored and purifications of the crude products were effected by high pressure liquid chromatographic techniques. The products were characterised by proton and carbon-13 nuclear magnetic resonance, infrared and mass spectroscopy, elemental and titrametric analysis. Results were compared with those obtained for tetra-N-glycidyl-4,4'-diaminodiphenylene methane (TGDDM). All the data confirmed the structures of the model resins. These, together with TGDDM. will be used to prepare epoxy resin networks of controlled crosslink density and chemical homogeneity.     

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     

Mechanical and thermal properties of epoxy resins with reversible crosslinks

The tensile properties: Young's modulus, ultimate tensile strength, ultimate elongation, the glass transition temperature, and the dynamic mechanical properties (dynamic shear modulus (G'), loss tangent (Tan δ)), of three epoxy resins (Epon 828, Epon 836, Epon HPT 1071) cured with the disulfide-containing crosslinking agent—4.4-dithiodianilme (DTDA) have been characterized. The results show that DTDA is a satisfactory crosslinking agent for the epoxide resins that have been studied as compared to the well-known curing agent methylene dianiline (MDA). There are no significant differences between the properties of Epon 828 cured with DTDA at stoichiometric ratio (2:1) and Epon 828 cured with DTDA at small amine excess ratio (1.75:1). The glass transition temperature of the cured tetrafunctional epoxy resin Epon HPT 1971 (235°C) is significantly higher than that of difunctional epoxy resins such as Epon 828 (T_g–175°C), but the product is too brittle to be used without plasticizer.