Glass fiber‐reinforced composites of diglycidyl ether of 2,7‐dihydroxy naphthalene

The curing reactions of epoxy resin diglycidyl ether of 2,7‐dihydroxy naphthalene (DGEDHN) with different aliphatic and aromatic amines have been studied by differential scanning calorimetry (DSC). The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber‐reinforced composites were fabricated, and their mechanical, electrical properties and resistance to chemicals were studied. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1345–1349, 2000     

Bonding properties of epoxy resins containing two mesogenic groups

Liquid‐crystalline epoxy resins, with introduced aliphatic chains between two mesogenic groups, were synthesized and their adhesive bonding properties were compared to those of the bisphenol‐A–type epoxy resin and the liquid‐crystalline epoxy resin, previously reported. The bonding strength of the former resin system was higher than that of the two later systems. We suggest that the high bonding strength of the twin mesogenic epoxy resins, cured with an aromatic amine, was attributable to the large plastic deformation of the adhesive layer in the fracturing process. We also investigated the effects of the aliphatic chain length in the twin mesogenic epoxy resin on their dynamic mechanical and bonding properties. The bonding strength of the cured twin mesogenic epoxy resins increased with an increase in the aliphatic chain length. We suggest that the high bonding strength of the system introduced by the long aliphatic chain was attributable to the large plastic deformation of the adhesive layer because of the higher network mobility. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3721–3729, 2004     

聚醚胺对高弹性-高伸长率环氧树脂胶粘剂力学性能影响的研究

用聚醚胺(D230,D400,T403)和聚醚胺(D2000)作为混合固化剂,用浇铸成型法制备了系列环氧树脂结构胶粘剂。目的是通过配方设计、简化工艺研制出系列具有高弹性-高伸长率的环氧树脂胶粘剂。并与普通改性脂肪胺(593#)和聚醚胺(D2000)作为混合固化剂,聚醚多元醇(HF220)作为改性剂的环氧树脂体系进行了比较。实验用SEM法对树脂浇铸体断面微观形貌进行了观察,用动态DMTA法对树脂玻璃化转变温度(Tg)进行了测定,并对固化物的拉伸强度、断裂伸长率、以及断面形貌进行了测定,考察了聚醚胺相对分子质量、结构、官能度对拉伸强度、断裂伸长率和应力-应变的影响。动态力学分析法(DMTA)结果显示:体系的玻璃化转变温度(Tg)随着聚醚胺(D2000)加入量的增加而降低,当m(D400)∶m(D2000)=35∶100,Tg为16.63℃,达到最低,说明材料在低温也具有较好的柔弹性。通过扫描电镜(SEM)观察,证明聚醚胺对环氧树脂具有优异的相容性,对环氧树脂起到了增柔-弹性化的作用。     

Fluorination of epoxy surfaces by a physical method

To enhance the surface hydrophobicity of epoxy polymers, a simple physical method for the simultaneous surface fluorination during curing of epoxy resins was proposed and evaluated. Curing of epoxy resins against a polytetrafluoroethylene (PTFE) mold gave rise to fluorinated epoxy polymer surfaces due to the anchorage of PTFE molecules on the epoxy polymer surface. The modified epoxy surfaces were characterized using contact‐angle measurements and X‐ray photoelectron spectroscopy (XPS). The fluorinated epoxy resin surfaces are highly hydrophobic, exhibiting contact angles of similar magnitude to that of the pristine PTFE film surface. The PTFE mold can be used repeatedly to give fluorinated epoxy surfaces with large contact angles. Aging and solvent extraction tests indicated that the fluorinated epoxy surfaces were very stable. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 296–304, 2000     

Reactions of phenolic ester alcohol with aliphatic isocyanates—transcarbamoylation of phenolic to aliphatic urethane: A 13C‐NMR study

Reactions of aliphatic isocyanates with a phenolic ester alcohol (PHEA) were investigated using ¹³C‐NMR spectroscopy. PHEA has two reactive sites: a phenolic  OH group and a secondary aliphatic  OH group. Both  OH groups react with the isocyanate groups. With an organotin catalyst, dibutyltin dilaurate (DBTDL), the aliphatic  OH group reacts first. With a tertiary amine catalyst, 1,4‐diazabicyclo[2.2.2]octane (DABCO), or triphenylphosphine (Ph₃P) or even in the absence of a catalyst at room temperature (RT) the phenolic  OH group reacts first. With the organotin catalyst, the reactions are generally complete in a day at RT. With DABCO or triphenylphosphine or DNNDSA catalysts, the reactions are almost complete only in 3–4 days at RT in ethyl acetate or acetonitrile. Uncatalyzed reactions are slower. With an acid catalyst such as dinonylnaphthalenedisulfonic acid (DNNDSA), both  OH groups react with the isocyanate. When equimolar quantities of PHEA and hexamethylenediisocyanate (HDI) polymerize at RT or reflux in the presence of a catalyst, both  OH groups react, with the phenol reacting slowly. Upon refluxing, the phenolic  OH‐based urethane slowly rearranges (transcarbamoylation) to the aliphatic  OH‐based urethane. DABCO and Ph₃P catalysts effect this rearrangement at a much slower rate than does the acid catalyst. In the presence of a catalytic amount of DBDTL in a refluxing solvent, this rearrangement is complete in 2 h. By refluxing the phenolic–OH‐based urethane in isopropanol, the mechanism of transcarbamoylation was found to be intermolecular. The mechanism is likely to involve deblocking of the phenolic urethane and subsequent reaction of the isocyanate generated, with the aliphatic  OH group. This conclusion was confirmed by differential scanning calorimetry (DSC) experiments. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2212–2228, 2000     

柔性环氧树脂的制备及其性能研究

通过在环氧树脂（EP）的侧链接枝柔性的聚丙二醇（PPG）制备了具有较高断裂伸长率的柔性EP。利用异佛尔酮二异氰酸酯（IPDI）中2个异氰酸酯（—NCO）基团的不同活性,首先在二月桂酸二丁基锡的催化作用下将IPDI引入EP,制备出带有NCO侧基的EP;然后再与不同相对分子质量的聚丙二醇（PPG400,PPG1000,PPG2000）进行反应,得到了具有不同长度柔性侧链的改性环氧树脂（PPG-g-EP）;使用聚醚胺（D400）作为固化剂,采用万能试验机测试固化树脂的力学性能。结果表明,柔性侧链的引入可以有效地降低材料的模量,提高其断裂伸长率,其中PPG2000改性EP的断裂伸长率最高可以达到98 %。     

环硫丙烯酸酯树脂的合成反应研究

将双酚A型环硫树脂ES128,ES128/环氧树脂CYD128混合物分别与丙烯酸反应制备了环硫丙烯酸树脂及环硫/环氧丙烯酸酯树脂。以红外光谱表征了产物结构,讨论了反应机理,并对丙烯酸用量,溶剂及加料顺序等对反应的影响进行了研究。结果表明:较佳的合成工艺条件为:甲苯为溶剂,环氧官能团与丙烯酸物质的量比为1∶2,反应温度90℃,反应时间4.5 h。工艺操作为先加入丙烯酸,再升温加入催化剂N,N-二甲基苄胺,可有效防止凝胶现象发生。与环氧官能团相比,环硫官能团与丙烯酸的反应活性较低。     

Tetrafunctional aliphatic epoxy I. Synthesis and characterization

A low viscosity tetrafunctional epoxy resin was synthesized by reacting amino-terminated polydimethylsiloxane with epichlorohydrin followed by dehydrohalogenation. The synthesized tetrafunctional aliphatic epoxy resin had an epoxy equivalent weight of 382, M_n of 1492, M_w of 2296, and a viscosity of 4.2 poise at 25°C. The chemical structure of the tetrafunctional aliphatic epoxy resin was studied by gel permeation chromatography (GPC), Fourier transform infrared spectra (FTIR), and ¹H-NMR spectra. Results showed the tetrafunctional aliphatic epoxy-blended aromatic epoxy resin possessed high impact strength and flexural strength. SEM photographs were investigated to study the compatibility of the blended epoxy system. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 51–58, 1998     

Toughening of epoxy resins with aromatic polyesters

Polyesters, prepared by direct polycondensation from bisphenol A and aliphatic dicarboxylic acids [adipic acid (AD), suberic acid, sebacic acid (SE), and dodecanedioic acid], were used to improve the toughness of the diglycidyl ether of the bisphenol A/diaminodiphenyl methane epoxy system. Polyesters had the number average molecular weight (M_n) ranging from 4300 to 19,200 g/mole. The epoxy systems modified with the AD system (M_n = 6400 g/mole) and the SE system (M_n = 10,200 g/mole) showed phase separated structures with discrete domains of 0.2 μm, but other systems showed smooth fracture surfaces when observed by scanning electron microscopy. The modified epoxy systems except for the AD system and SE system showed two tan δ peaks corresponding to the α and β transitions of the epoxy resin. The modified epoxy systems showed maximum values of K_1c at around 10 wt % of polyester and maximum flexural properties at 5 wt % of polyester. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2464–2473, 2000     

环氧脂肪酸钙的直接法合成及其对PVC热稳定作用的研究

以一种简便的方法制备了环氧基保留完好的高纯度环氧脂肪酸钙,研究发现环氧脂肪酸钙对聚氯乙烯的热稳定作用类似于硬脂酸钙,具有长期热稳定性的特征,但其热稳定效能明显优于后者,且具有较好的初期着色性。     

Performance of paint systems with polyurethane topcoats, proposed for atmospheres with very high corrosivity category

The EN ISO Standard 12944-5 describes the types of paint and paint systems commonly used for corrosion protection of steel structures. In this work four paint systems, applied on steel, including polyurethane topcoats, recommended for atmospheres with high corrosivity (C5 category), codified by 1–4, were studied. Systems 1 and 4 include zinc rich primers and epoxy/polyamide intermediates, system 2 has solvent free epoxy/polyamide primer and intermediate and, system 3 is a hybrid system with vinyl–acrylic water based primer and a high solids epoxy/polyamide intermediate. Systems 2–4 have acrylic–polyurethane topcoats and, the topcoat of the system 1 was identified as an aliphatic polyurethane.

According to EN ISO 12944-6, water condensation and neutral salt spray tests were performed. Three exposure times were considered taking into account the durability ranges of paint systems: low, medium and high, respectively. The paint systems were complementary submitted, during 30 days, to ultraviolet radiation with water condensation test according to ASTM G 154. At the same time, natural exposure was conducted in the marine atmosphere of Sines, with very high corrosivity (>C5).

The paint adhesion, before and after artificial ageing, was evaluated by cross-cut test and, for the systems with dry thickness greater than 250 μm, by pull-off test. Visual inspections were carried out.

For the exposure in UV radiation test chamber and at test site, gloss reduction, colour change and chalking were measured. Chemical changes on polyurethane topcoats exposed in the UV radiation test chamber were studied by Fourier transform infrared spectroscopy (FTIR).

In spite of the higher aesthetic degradation by UV radiation, of the aliphatic polyurethane topcoat of the system 1 relatively to the acrylic–polyurethane topcoats of the other systems, system 1 with ethyl silicate zinc rich primer and epoxy intermediate, was the one that presented the best corrosion protection when exposed in artificial and natural salty environments. At the test site, the worst anticorrosive behaviour seems to be presented by the system 2 with two coats of solvent free epoxy paint.     

Influence of chemical structure of isophthaloyl dichloride and aliphatic,cycloaliphatic, and aromatic diamine compound polyamides on their chlorine resistance

The influence of the chemical structures of the polyamides on chlorine resistance was studied by measuring their chlorine uptake rates. They were prepared from isophthaloyl dichloride and aliphatic, cycloaliphatic, or aromatic diamines by the solution or interfacial polycondensation method. This study showed that the chlorine resistance was dependent on the chemical structures of the diamine compounds used in the synthesis of the polyamides. We concluded that the polyamides comprising the diamine components with the following chemical structures had higher chlorine resistance: aliphatic or cycloaliphatic diamine compounds with a secondary amino group, aliphatic or cycloaliphatic diamine compounds with a shorter methylene chain length between end amino groups, and aromatic diamine compounds with methyl or chlorine substituents at the ortho position of the amino groups. Chlorine resistance is related to the basicity of the aliphatic and aromatic diamines used. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 201–207, 2000     

Study on Novel Epoxy Based Poly (Schiff Reagent)s

Abstract

Novel poly(schiff reagent)s from diketo derivative of epoxy resin were synthesised and characterised. A series of epoxy resin based poly(schiff reagent)s were synthesised by reacting an epoxy resin, diglycidyl ether of bisphenol-A (DGEBA) with 4-amino acetophenone (4-AAP) in a 1:2 mole ratio to afford the corresponding diketo derivative, and subsequent reaction with various aliphatic diamines in a presence of a triethyl amino as a catalyst. The resultant poly(schiff reagent)s were characterised by infrared spectroscopy (IR) and number average molecular weight (Mn) of PSs were estimated by non-aqueous conductometric titration. As produced, PSs having amine groups may act for curing of epoxy resins. Differential scanning calorimetric (DSC) curing kinetics of the epoxy resins viz. diglycidyl ether of bisphenol-A(DGEBA) and triglytidyl-p-amino phenol (TGPAP) have been investigated using PSs as a curing agent and triethyl amine as a catalyst. Thermal stability of the cured epoxy systems were studied by thermogravimetric analysis (TGA). The glass fiber reinforced composites of the produced PSs-epoxy system have been fabricated and were characterised by their mechanical properties and chemical resistance.     

Chemical modification of Bombyx mori silk with epoxide EPSIB

Bombyx mori silk fabrics were chemically modified by EPSIB (a multifunctional silicone‐containing epoxy crosslinking agent). The reactivity of the epoxy groups with silk fibroin was studied by using amino acid analysis. The physical properties of the modified silks such as resiliency (both wet and dry), moisture regain, dyeing behaviors, and solubility in a mixture solvent (C₂H₅OH × CaCl₂ : H₂O = 2 : 1 : 8, molar ratio) were examined. The modified silk fabrics exhibited a significantly improved resiliency, a small increase in moisture regain and whiteness, and a slightly decreased tensile strength. The contents of Serine, Trosine, Lysine, and Histidine decreased linearly as the wet crease recovery angle (CRA) increased. The solubility in the mixture solvent also decreased as the wet CRA increased. The changes of physical properties, especially the wet CRA, were mainly due to the presence of stable cross‐links between silk fibroin and epoxy groups. The DSC and TGA analyses showed that EPSIB‐modified silk fibroin had a higher thermal stability compared with the control. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3579–3586, 2004     

Toughening of an epoxy anhydride resin system using an epoxidized hyperbranched polymer

This paper reports on the use of an epoxidized hyperbranched polymer (HBP) as an additive to an epoxy anhydride resin system. The hyperbranched polymer used was an aliphatic polyester with a molecular weight of around 10 500 g mol^?1. The epoxy resin mixture used was a combination of a difunctional diglycidyl ether of bisphenol A (DGEBA) epoxy and an epoxy novolac, and was cured with a catalysed anhydride curing agent. It has been shown that, at a concentration range of 0 to 20 wt% addition, the HBP is able to almost double the fracture toughness, with little evidence of any deleterious effects upon processing and the durability of the cured resin system. The flexural modulus and stress, however, were found to both decrease by about 30% as a result of HBP addition while the T_g was found to decrease by about 10%. The processability of the uncured resin systems has been investigated by using rheological and calorimetric techniques and it was found that the processability window, as determined by the gel time and viscosity changes, was relatively unaffected by HBP addition. The fracture surfaces were evaluated by using scanning electron microscopy which showed that the unique structure of the HBP facilitates an enhanced interaction with the polymer matrix to achieve excellent toughness enhancement of the polymer matrix. The durability of the epoxy network has been investigated via thermogravimetric analysis (TGA) and solvent uptake, and the HBP has been shown to have little systematic deleterious effect upon the degradation temperatures and the total amount of solvent absorbed. Copyright © 2003 Society of Chemical Industry     

Study on Novel Epoxy Based Poly(schiff reagent)s

Abstract

Novel poly(schiff reagent)s (PSs) from diketo derivative of epoxy resin were synthesised and characterised. A series of epoxy resin based poly(schiff reagent)s were synthesised by reacting an epoxy resin, diglycidyl ether of bisphenol-A (DGEBA) with 4-amino acetophenone (4-AAP) in a 1:2 mole ratio to afford the corresponding diketo derivative, and subsequent reaction with various aliphatic diamines in the presence of a triethyl amine as a catalyst The resultant poly(schiff reagent)s were characterised by infrared spectroscopy (IR) and number average molecular weight (Mn) of PSs were estimated by non-aqueous conductometric titration. As produced, PSs having amine groups may act for curing of epoxy resins. Differential scanning calorimetric (DSC) curing kinetics of the epoxy resins viz., diglycidyl ether of bisphenol-A(DGEBA) and triglycidyl-p-amino phenol (TGPAP) have been investigated using PSs as a curing agent and triethyl amine as a catalyst. Thermal stability of the cured epoxy systems was studied by thermo-gravimetric analysis (TGA). The glass fiber reinforced composites of the produced PSs-epoxy system have been fabricated and were characterised by their mechanical properties and chemical resistance.     

Synthesis and Properties of Interpenetrating Polymer Networks Composed of Epoxy Resins and Polysulphones with Cross-linkable Pendant Vinylbenzyl Groups

Polysulphones with cross-linkable pendant vinylbenzyl groups (PSF-VB) were prepared via chloromethylation of commercial polysulphones. The curing reactivity of PSF-VB was investigated by differential scanning calori-metry. Interpenetrating polymer networks (IPNs) were prepared based on bisphenol A diglycidyl ether (DGEBA) and PSF-VB, where DGEBA was cured by 4,4′-diaminodiphenyl sulphone and VB groups of PSF-VB were radically polymerized using dicumyl peroxide (DCP). Polysulphones having pendant benzyl groups (PSF-Bz) were also prepared and used as non-reactive modifiers. The fracture toughness (K_IC) for the resulting epoxy/PSF-VB IPN increased by 65% with no loss of mechanical properties on 10wt% addition of PSF-VB (7·9mol% VB unit, MW 74000). Non-reactive PSF-Bz was less effective than PSF-VB. Although the PSF-Bz modified resin had a particulate structure, the morphologies of the PSF-VB/epoxy IPNs were not clear from scanning electron micrographs. Furthermore, the epoxy/PSF-VB IPNs had higher solvent resistance than the epoxy/PSF-Bz blends. Morphological behaviour, modification results and high solvent resistance of the cured epoxy/PSF-VB resins indicate that cross-linked PSF-VB and the epoxy network entangled fully in the presence of DCP. © of SCI.     

Polyurethane‐modified epoxy resin: Solventless preparation and properties

A polyurethane‐modified epoxy resin system with potential as an underfill material in electronic packaging and its preparation procedure were studied. The procedure enabled the practical incorporation of an aliphatic polyurethane precursor, synthesized from poly(ethylene glycol) and hexamethylene diisocyanate without a solvent, as a precrosslinking agent into a conventional epoxy resin. With a stoichiometric quantity of the polyurethane precursor added to the epoxy (ca. 5 phr), the polyurethane‐modified epoxy resin, mixed with methylene dianiline, exhibited a 36% reduction in the contact angle with the epoxy–amine surface, a 31% reduction in the cure onset temperature versus the control epoxy system, and a viscosity within the processable range. The resultant amine‐cured thermosets, meanwhile, exhibited enhanced thermal stability, flexural strength, storage modulus, and adhesion strength at the expense of a 5% increase in the coefficient of thermal expansion. Exceeding the stoichiometric quantity of the polyurethane precursor, however, reduced the thermal stability and modulus but further increased the coefficient of thermal expansion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Self-healing thermoset using encapsulated epoxy-amine healing chemistry

Self-healing was achieved with a dual-microcapsule epoxy-amine chemistry in thermoset epoxy. One capsule contained a modified aliphatic polyamine (EPIKURE 3274) while the second capsule contained a diluted epoxy monomer (EPON 815C). Amine microcapsules were prepared by vacuum infiltration of EPIKURE 3274 into hollow polymeric microcapsules. Epoxy microcapsules were prepared by an in situ polymerization method. Both types of capsules were incorporated into an epoxy matrix (EPON 828:DETA) and recovery of mode-I fracture toughness was measured using tapered-double-cantilever-beam (TDCB) specimens. The optimal mass ratio of amine: epoxy capsules was 4: 6 and an average healing efficiency of 91% was achieved with 7 wt% amine capsules and 10.5 wt% epoxy capsules. Long-term stability of the healing system was demonstrated for six months at ambient conditions. Thermal stability was investigated by post curing samples at 121 °C and assessing healing performance.     

Novel thermosets based on DGEBA and hyperbranched polymers modified with vinyl and epoxy end groups

The cationic polymerization of DGEBA with two hyperbranched polymers (HBPs) with epoxy or vinyl end groups, using ytterbium triflate as initiator, has been studied. These HBPs have been obtained from commercial Boltorn H30 of which terminal hydroxyl groups have been replaced with long aliphatic ester chains having vinyl or epoxy end groups. Differences between the HBPs added as modifiers are observed with respect to the curing kinetics, network development, properties and morphology of the cured materials. While terminal epoxy groups ease the solubility of the HBP in DGEBA and allows its covalent incorporation into the network structure, the HBP with vinyl terminal groups is only miscible at high temperature and phase-separates during curing. As a consequence, morphology and thermal–mechanical properties are strongly dependent on the HBP employed.