环氧化端羟基聚丁二烯增韧环氧树脂的研究

使用环氧化端羟基聚丁二烯（EHTPB）对双酚A型环氧树脂进行增韧改性。对EHTPB增韧的固化产物及端羟基聚丁二烯（HTPB）增韧的固化产物进行力学性能测试,运用差示扫捕量热法测试同化产物的玻璃化转变温度,采用扫面电镜观察树脂增韧前后的断面形貌,显示为韧性断裂。各种结果表明,EHTPB对环氧树脂的增韧效果优于HTPB,该增韧剂的加入能够在不明显降低树脂强度的条件下,大幅度提高体系韧性的同时保持树脂的玻璃化转变温度。     

Synthesis and characterization of diphenylsilanediol modified epoxy resin and curing agent

A series of diphenylsilanediol modified epoxy resins and novel curing agents were synthesized. The modified epoxy resins were cured with regular curing agent diethylenetriamine (DETA); the curing agents were applied to cure unmodified diglycidyl ether of bisphenol A epoxy resin (DGEBA). The heat resistance, mechanical property, and toughness of all the curing products were investigated. The results showed that the application of modified resin and newly synthesized curing agents leads to curing products with lower thermal decomposition rate and only slightly decreased glass transition temperature (T_g), as well as improved tensile modulus and tensile strength. In particular, products cured with newly synthesized curing agents showed higher corresponding temperature to the maximum thermal decomposition rate, comparing with products of DGEBA cured by DETA. Scanning electron microscopy micro images proved that a ductile fracture happened on the cross sections of curing products obtained from modified epoxy resins and newly synthesized curing agents, indicating an effective toughening effect of silicon–oxygen bond.     

Modification of epoxy resins with poly(aryl ether ketone)s

Poly(aryl ether ketone)s were used as modifiers for bisphenol-A diglycidyl ether epoxy resin (AER 331) cured with methyl hexahydrophthalic anhydride. Poly(phthaloyl diphenyl ether) (PPDE), soluble in the uncured epoxy resin without using solvents, was prepared by the Friedel-Crafts reaction of phthaloyl chloride and diphenyl ether. The mechanical, thermal, and dynamic viscoelastic properties of the modified resins with PPDE were examined and compared to the parent resin (AER 331). The fracture toughness, K_IC, for the modified resins increased at no expense to their mechanical and thermal properties on 10 wt % addition of PPDE with molecular weights of more than 17,000. The toughening mechanism is discussed based on the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system.     

环氧化端羟基聚丁二烯改性氰酸酯树脂体系研究

采用环氧化端羟基聚丁二烯(EHTPB)对双酚A型二氰酸酯树脂(BADCy)进行增韧改性。运用差示扫描量热法分析改性体系的反应性,发现EHTPB对BADCy的固化反应有一定的催化作用。采用傅立叶变换红外光谱仪、扫描电子显微镜和广角X射线衍射仪等表征共混物的结构特征,研究增韧改性机理,并对固化产物进行热重分析和力学性能测试。结果表明,EHTPB能在不显著降低体系热稳定性的同时改善体系的韧性,使得改性树脂具有较好的综合性能。     

无卤阻燃含磷环氧树脂的研究进展

无卤阻燃含磷环氧树脂中的磷成分具有气相和凝聚相的双重阻燃作用,且材料本身降解产物不产生可持续性环境污染物,因而作为环境友好型阻燃材料而被广泛研究。本文综述了近年来关于含9,10-二氢-9-氧杂-10-磷杂菲10-氧化物(DOPO)环氧树脂体系（包含DOPO环氧树脂、DOPO基固化剂和添加型DOPO改性聚合物）、磷酸酯型环氧树脂体系（包括磷酸酯环氧树脂、环状磷酸酯环氧树脂、磷酸酯型固化剂）、含磷固化剂以及磷腈环氧树脂和磷-硅环氧树脂的研究进展,介绍了每种体系的性能特点。总结了含磷环氧树脂的阻燃性能、热性能、阻燃机理,以及磷-氮协同效应、磷-硅复合二元体系的阻燃机理。     

Catalytic effect of 2,2′‐diallyl bisphenol A on thermal curing of cyanate esters

Cyanate esters are a class of thermal resistant polymers widely used as thermal resistant and electrical insulating materials for electric devices and structural composite applications. In this article, the effect of 2,2′‐diallyl bisphenol A (DBA) on catalyzing the thermal curing of cyanate ester resins was studied. The curing behavior, thermal resistance, and thermal mechanical properties of these DBA catalyzed cyanate ester resins were characterized. The results show that DBA is especially suitable for catalyzing the polymerization of the novolac cyanate ester resin (HF‐5), as it acts as both the curing catalyst through depressing the exothermic peak temperature (T_exo) by nearly 100°C and the toughening agent of the novolac cyanate ester resin by slightly reducing the elastic modulus at the glassy state. The thermogravimetric analysis and dynamic mechanical thermal analysis show that the 5 wt % DBA‐catalyzed novolac cyanate ester resin exhibits good thermal resistance with T_d⁵ of 410°C and the char yield at 900°C of 58% and can retain its mechanical strength up to 250°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1775–1786, 2006     

Influence of Multiwalled Carbon Nanotubes on Mechanical,Thermal and Electrical Behavior of Polybenzoxazine-Epoxy Nanocomposites

Multiwalled carbon nanotubes (MWCNT)-reinforced polybenzoxazine-epoxy nanocomposites were prepared via the solvent method and were investigated for their thermal, thermo-mechanical, mechanical, electrical and morphological properties. Epoxy resin (DGEBA) was modified with 5, 10 and 15 wt.% of benzoxazines using 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. Epoxy and benzoxazines-modified epoxy systems were further reinforced with 0.25, 0.50 and 0.75 wt.% of surface-modified MWCNT. MWCNT-reinforced polybenzoxazine-epoxy nanocomposites exhibited better thermal, mechanical and dielectric properties. Dispersion of MWCNT in benzoxazine-epoxy resins and nanostructure of the composites was confirmed by transmission electron microscopy analysis.     

A random acrylate copolymer with epoxy‐amphiphilic structure as an efficient toughener for an epoxy/anhydride system

Toughening of epoxy resin by block copolymers containing an epoxy‐philic block and an epoxy‐phobic block is usually costly because of their complex preparation procedure. In this work, a novel, random epoxy‐amphiphilic copolymer (PHGEL), which combines an “epoxy‐philic” component and an “epoxy‐phobic” component, has been synthesized and evaluated as a potential toughening agent for a diglycidyl ether of bisphenol A–based epoxy thermoset (EP). The curing behavior of the EP/PHGEL system has been investigated, and the results show that the hydroxyl group on the PHGEL chain can slightly activate the curing reaction. The mechanical testing shows that the toughness of the epoxy resin is improved by 294% when 4 wt % of PHGEL is added. Simultaneously, the tensile strength, elongation at break, and glass‐transition temperature are also improved. In addition, the thermogravimetric analysis shows that PHGEL has no obvious effect on the thermal stability of the epoxy thermosets. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44863.     

Preparation,characterization, and improvement of hollow epoxy particle‐toughened vinyl ester composites for high‐end applications

Spherical hollow epoxy particles (HEPs) that can serve as advanced reinforcing fillers for vinyl ester thermosets were prepared using the water‐based emulsion method. The HEP fillers were incorporated into the vinyl ester matrices at different loading amounts, ranging from 0 to 9 wt %, to reinforce and toughen the vinyl ester composite. The optimum mechanical properties of the HEP‐toughened epoxy composite can be achieved by the addition of 5 wt % HEP filler into the vinyl ester matrices. The toughening and strengthening of the epoxy composites involved the interlocking of vinyl ester resins into the pore regions on the HEP fillers. The toughening and interlocking mechanisms of HEP‐toughened vinyl ester composites were also proposed and discussed. The addition of HEP fillers into vinyl ester matrices increased the glass transition temperature (T_g) and thermal stability of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Toughening epoxy resins with polyepichlorohydrin

Polyepichlorohydrin (PECH) rubbers were found to toughen epoxy resins based on the diglycidyl ether of bisphenol A (DGEBA) and cured with piperidine. The degree of toughening depends on the molecular weight of the PECH and on the curing temperature. Best toughening was achieved with PECH of the highest nominal molecular weight of 3400 (Hydrin 10 × 2). Hydrin 10 × 1 (nominal molecular weight 1700) did not toughen the epoxy resin unless bisphenol A was also added, whereas Hydrin 10 × 2 toughened it in the absence of bisphenol A. Curing resins containing bisphenol A and Hydrin 10 × 1 at 160°C resulted in a slightly more brittle resin than when cured at 120°C. The effect of PECH rubbers on the T_g, modulus, and hot/wet properties is similar to that of carboxy-terminated butadiene-acrylonitrile rubbers (CTBN). Dynamic mechanical thermal analysis (DMTA) and scanning electron micrographs (SEM) of fractured surfaces show that the PECH separates as a discrete phase during curing. © 1993 John Wiley & Sons, Inc.     

The effects of polyamic acid on curing behavior,thermal stability,and mechanical properties of epoxy/DDS system

A thermoplastic modification method was studied for the purpose of improving the toughness and heat resistance and decreasing the curing temperature of the cured epoxy/4, 4′‐diaminodiphenyl sulfone resin system. A polyimide precursor‐polyamic acid (PAA) was used as the modifier which can react with epoxy. The effects of PAA on curing temperature, thermal stability and mechanical properties were investigated. The initial curing temperature (T_i) of the resin with 5 wt % PAA decreased about 50°C. The onset temperature of thermal decomposition and 10 wt %‐weight‐loss temperature for the resin system containing 2 wt % PAA increased about 60°C and 15°C respectively. Besides, the value of impact toughness and plain strain fracture toughness for the modified epoxy resin increased ～ 190% and 55%, respectively. Those changes were attributed to the outstanding thermal and mechanical properties of polyimide, and more importantly to formation of semi‐interpenetrating polymer networks composed by the epoxy network and linear PAA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of the structure of curing agents modified by epoxidized oleic esters on the toughness of cured epoxy resins

The aim of this study was to determine the effect of the ester carbon chain length of curing agents modified by epoxidized oleic esters on the toughness of cured epoxy resins. An amine‐terminated prepolymer (i.e., curing agent G) was synthesized from a bisphenol A type liquid epoxy resin and triethylene tetramine. The toughening curing agents (G1 and G2) were prepared by reactions of epoxidized oleic methyl ester and epoxidized oleic capryl ester, respectively, with curing agent G. Fourier transform infrared spectrometry was used to characterize the chemical structure of the curing agents. The effects of the carbon chain length of the oleic ester group in the curing agents on the toughness and other performances of the curing epoxy resins were investigated by analysis of the Izod impact strength, tensile strength, elongation at break, thermal properties, and morphology of the fracture surfaces of the samples. The results denote that the toughness of the cured epoxy resins increased with the introduction of oleic esters into the curing agents without a loss of mechanical properties and that the toughness and thermal stability of the materials increased with increasing ester carbon chain length. The toughness enhancement was attributed to the flexibility of the end carbon chains and ester carbon chains of the oleic esters in the toughening curing agents. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Toughening of aromatic diamine-cured trifunctional epoxy resins by modification with N-phenylmaleimide–styrene copolymers containing pendant p-hydroxyphenyl groups

N-Phenylmaleimide (PMI)–N-(p-hydroxy)phenylmaleimide (HPMI)–styrene (St) terpolymers (HPMS), containing pendant p-hydroxyphenyl (HP) groups, were prepared and used to improve the toughness of triglycidyl aminocresol epoxy resin cured with p,p′-diaminodiphenyl sulfone. HPMS was effective as a modifier for the toughening of the epoxy resin. When using 15 wt % of HPMS (1.0 mol % HP unit, M_w 129,000), the fracture toughness (K_IC) for the modified resin increased 190% with a medium loss of flexural strength. The toughening of epoxies could be attained because of the cocontinuous phase structure of the modified resins. The decrease in flexural strength was suppressed to some extent by introducing a functional group into the modifier. The toughening mechanism was discussed in terms of the morphological behavior of the modified epoxy resin system. © 1995 John Wiley & Sons, Inc.     

Poly(ester‐amine) hyperbranched polymer as toughening and co‐curing agent for epoxy/clay nanocomposites

The marriage between hardness and flexibility of epoxy resins (improved toughness) is a desired feature, which broads their application in various industrial fields, especially for high impact resistance purposes. Accordingly, this work aims to improve toughness properties of epoxy resin (Epon‐828)/Ancamine (curing agent) system using amino‐terminated hyperbranched poly(ester‐amine) [Poly(PEODA‐NPA)] (HP) as toughening and/or co‐curing agent, in presence of organo‐modified Montmorillonite clay (OMMT) as a reinforcing filler. HP was synthesized via Michael addition reaction of poly(ethylene glycol) diacrylate (PEODA) to N‐methyl‐1,3‐propanediamine (NPA). Chemical structure and molecular weight of HP were elucidated using infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) techniques, respectively. Epoxy/OMMT nanocomposites toughened with HP (at different concentrations) showed remarkable improvement in their toughness without any adverse effect on the other physico‐mechanical properties. The optimum concentration of HP and OMMT was found to be 20 wt % and 1–3 wt% of the epoxy resin, respectively. The extent of exfoliation and dispersion of OMMT platelets within the epoxy cured films was assessed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. In addition, thermal gravimetric analyses (TGA‐DTA) of epoxy/OMMT nanocomposites toughened with HP showed a slight increase in their decomposition temperature, particularly at low OMMT loading. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Effect of anhydride curing agents,imidazoles, and silver particle sizes on the electrical resistivity and thermal conductivity in the silver adhesives of LED devices

This study investigated the preparation of silver adhesives applied to a light‐emitting diode (LED) device as die‐attach materials consisting of silver particles, on epoxy resin, curing agents, and accelerants for complete curing at 150 °C for 30 min. For the epoxy resin, this study used 3,4‐epoxycyclohexyl‐methyl‐3,4‐epoxycyclohexanecarboxylate mixed with different types of anhydride curing agents such as 4‐methylcyclohexane‐1,2‐dicarboxylic anhydride and hexahydrophthalic anhydride as well as imidazole accelerants such as 2‐ethyl‐4‐methyl‐1H‐imidazole‐1‐propanenitrile, 2‐phenylimidazole, 2‐methylimidazole, 2‐phenyl‐2‐imidazoline, and 1,2‐dimethylimidazole. In addition, different size of silver particles and hybrid silver particles were used for the electrical resistivity and thermal conductivity of silver adhesives. Differential scanning calorimetric (DSC) measured conversion of silver adhesives based on different types and contents of the curing agents and accelerants under heating. The silver particles' distribution of silver adhesive also affected electrical resistance, as proved by scanning electronic microscopy (SEM) and four‐point probe. The obtained results showed that the silver adhesive containing an 100 wt % of epoxy resin mixed with 85 wt % of hexahydrophthalic anhydride, 1.0 wt % (weight of epoxy resin) of 2‐ethyl‐4‐methyl‐1H‐imidazole‐1‐propanenitrile, and 80 wt % (weight of epoxy resin) of hybrid silver particles (40 wt % 15 μm and 40 wt % 1.25 μm) was perfect, having the lowest electrical resistivity at 1.11 × 10^?4 Ω·cm and good thermal conductivity at 3.2 W/m·K. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43587.     

Effect of Phenol/Formaldehyde Stoichiometry on the Modification of Epoxy Resin Using Epoxidized Novolacs

ABSTRACT

Unmodified epoxy resins based on bisphenol A exhibit brittleness and low elongation after cure. This article reports the results of a study for improving the properties of epoxy resin by blending with suitable thermosets. Hybrid polymer networks of diglycidyl ether of bisphenol A (DGEBA) resin with epoxidized phenolic novolac resins (EPN) containing phenol and formaldehyde in different stoichiometric ratios were prepared by physical blending. The modified epoxy resins were found to exhibit improved mechanical and thermal properties compared to the neat resin. DGEBA resins containing 2.5 to 20 wt% of epoxidized novolac resins (EPN) prepared in various stoichiometric ratios (1:0.6, 1:0.7, 1:08, and 1:0.9) between phenol and formaldehyde were cured using a room temperature amine hardener. The cured samples were tested for mechanical properties such as tensile strength, modulus, elongation, and energy absorption at break. All the EPNs are seen to improve tensile strength, elongation, and energy absorption at break of the resin. The blend of DGEBA with 10 wt% of EPN-3 (1:0.8) exhibits maximum improvement in strength, elongation, and energy absorption. EPN loading above 10 wt% is found to lower these properties in a manner similar to the behavior of any filler material. The property profiles of epoxy–EPN blends imply a toughening action by epoxidized novolac resins and the extent of modification is found to depend on the molar ratio between phenol and formaldehyde in the novolac.     

Toughening of epoxy resins by modification with aromatic polyesters

Aromatic polyesters, prepared by the reaction of phthalic or isophthalic acids and α,ω-alkanediols, were used to reduce the brittleness of bisphenol-A diglycidyl ether epoxy resin cured with methyl hexahydrophthalic anhydride. These polyesters were effective as modifiers for toughening of the epoxy resin system. The most suitable composition for modification of the epoxy resins was inclusion of 20 wt % of poly(ethylene phthalate) (MW 7200), which resulted in a 150% increase in the fracture toughness (K_IC) of the cured resin at no expense of its mechanical properties. The effectiveness of poly(alkylene phthalate)s as modifiers decreased with increasing the chain length of alkylene units. The toughening mechanism was discussed based on the morphological and dynamic mechanical behaviors of the modified epoxy resin system.     

聚脲基氨酯增强增韧环氧树脂的研究

用原位多相聚合法合成了聚脲基氨酯/环氧树脂互穿聚合物网络（IPN）,测定了产物的力学性能和热性能。探讨了IPN中聚脲基氨酯含量对环氧树脂增韧过程的影响,结果表明,对于N,N-二甲基苄胺固化体系,加入12.0phr的聚脲基氨酯,在不降低其热稳定性的同时,可使环氧树脂冲击强度提高35%左右,拉伸强度提高12%～15%;对于4,4＇-二氨基二苯砜或4,4＇-二氨基二苯甲烷固化体系,加入12.0phr的聚脲基氨酯可使环氧树脂冲击强度提高92%左右,拉伸强度提高20%～24%。     

Studies on isotactic poly(phenyl glycidyl ether)‐modified epoxy resins. II. Toughening of epoxy resins

A semicrystalline polymer, isotactic poly(phenyl glycidyl ether) (i‐PPGE) was used as a modifier for epoxy resin; 1,8‐Diamino‐p‐methane (MNDA) and 4,4′‐Diamino diphenyl sulfone (DDS) were used as curing agents. In the MNDA‐cured resins, the dispersed phase were spherical particles with diameters in the range of 0.5–1.0 μm when the resin was blended with 5 phr i‐PPGE. In the DDS‐cured resins, the particle size distribution of the dispersed phase was much wider. The difference was traced back to the reactivity of the curing agent and the different regimes used for curing. Through dynamic mechanical analysis, it was found that in the MNDA‐cured systems, i‐PPGE had a lower crystallinity than in the DDS‐cured system. In spite of the remarkable difference in the morphology and microstructure of the modified resins cured with these two curing agents, the toughening effects of i‐PPGE were similar for these resins. The critical stress intensity factor (K_IC) was increased by 54% and 53%, respectively, for the resins cured by DDS and by MNDA, blending with 5 phr of the toughner. i‐PPGE was comparable with the classical toughners carboxyl‐terminated butadiene‐acrylonitrile copolymers in effectiveness of toughening the epoxy resin. An advantage of i‐PPGE was that the modulus and the glass‐transition temperature of the resin were less affected. However, this modifier caused the flexural strength to decrease somewhat. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1223–1232, 2002; DOI 10.1002/app.10445     

Preparation of epoxy-terminated poly(aryl ether sulfone)s and their use as modifiers for epoxy resins

Epoxy-terminated poly(aryl ether sulfone)s (PSE) were prepared by the reaction of epichlorohydrin with hydroxyethyl-terminated polysulfones, which were synthesized from chloro-terminated polysulfones (PSC) and diethanolamine. Both PSE and PSC were used as modifiers for toughening of bisphenol A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulfone. The mechanical, thermal, and dynamic viscoelastic properties of the modified resins were examined and compared to the parent epoxy resin. The effectiveness of PSC was larger than that of PSE. The fracture toughness, K_IC, for the modified resin increased 45% at slight expense of its mechanical properties on 20 wt % addition of PSC (M_w 5300). These results were discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system.