CARDURAE-10改性水性环氧固化剂及其室温固化机理

用具有多支链柔韧性链段的C12～14叔碳酸缩水甘油酯(CARDURAE-10)对环氧-胺加成物EPON828-TETA进行封端改性。CARDURAE-10改性后的水性环氧固化剂与液体环氧树脂在室温下固化所形成的涂膜性能良好。采用傅立叶转换红外光谱法(FT-IR)对其室温固化过程和机理进行了研究。     

水性环氧固化剂分散体的制备及改性

采用不同分子量的聚乙二醇与液体环氧树脂EPON828合成反应型乳化剂,然后将反应型乳化剂链段引入到以液体环氧树脂EPON828与间苯二甲胺为原料合成的端胺基中间体的分子结构中,再用活性稀释剂进行封端,最后加水分散,制得水性环氧固化剂分散体。采用了γ-氨丙基三乙氧基硅烷(即硅烷偶联剂KH-550)对其进行改性。确定了间苯二甲胺与环氧树脂EPON828的摩尔比为2.2∶1,聚乙二醇6000与环氧树脂EPON828(摩尔比为1∶1)制备的反应型乳化剂用量为9%,硅烷偶联剂KH-550的用量为固化剂分散体的质量的2%时,所制备的水性环氧固化剂分散体稳定性最佳,其粒径为750.8nm,固含量约60%,胺值为118mgKOH/g,黏度为4500mPa·s。室温固化后,涂膜硬度为3H,光泽度(60°)为108%,冲击强度50kg·cm,柔韧性1mm,附着力1级,耐酸碱腐蚀性能好。通过傅立叶变换红外光谱表征了反应产物。     

环氧树脂增韧固化剂固化反应的FT-IR研究

使用环氧-三乙烯四胺缩聚物G(Epon828-TETA)及其环氧油酸辛酯改性物(G1)作为环氧树脂(Epon828)的固化剂,通过傅立叶变换红外光谱(FT-IR)法,比较研究了G/Epon828和G1/Epon828两个固化体系的动态等温固化过程,并能进一步对两个固化体系固化初期的固化反应进行了动力学研究.结果表明:两个固化体系的环氧基转化率都在较短时间内达到较高水平,随时间的延长,转化率上升缓慢并逐渐趋于恒定;固化温度越高,转化率越高;固化反应的反应速率在开始时很快达到最高,随反应时间的延长,反应速率逐渐下降并趋于稳定,并且固化温度越高,反应速率越高;但在相同的固化温度下,G/Epon828固化体系的转化率始终高于G1/Epon828固化体系.前者的固化反应速率在初期也大于后者;G/Epon828和G1/Epon828固化体系的固化反应均属一级反应,在相同的环氧基转化率时,前者的反应活化能和指前因子均小于后者.     

新型非离子型水性环氧固化剂的制备

以苯酚、甲醛、二乙烯三胺为原料制备曼尼希胺(Man - A1),然后以聚乙二醇与液体环氧树脂的反应物(P)为改性剂对Man - A1进行改性,再用苯基缩水甘油醚封端,制得具有自乳性的改性曼尼希胺(Man - A2),最后采用相反转法制得了非离子型水性环氧固化剂.讨论了聚乙二醇相对分子质量、聚乙二醇与环氧树脂物质的量之比以及端羟基环氧聚合物P的含量对乳液的稳定性和粒径的影响.结果表明:以聚乙二醇4 000为原料制备端羟基环氧聚合物P,当聚乙二醇4 000与环氧树脂物质的量之比为3:4,P的添加量为20％时,所得的水性环氧固化剂体系的稳定性最佳,在3 000 r/min的离心机中20 min不分层,平均粒径最小,为0.43 μm,固含量约为50％,胺值为160 mgKOH/g.室温固化后,涂膜硬度4H,耐冲击性50 cm,柔韧性1mm,附着力0～1级,适用期5～6h,耐水性优异.     

Ⅰ型水性环氧树脂涂料的研制

采用低分子量液体环氧树脂与非离子表面活性剂（BMJ）反应合成BMJ－环氧加成物,将表面活性链段引入到环氧树脂分子链中,然后经封端和成盐得到Ⅰ型水性环氧固化剂,研究了影响Ⅰ型水性环氧固化剂及其所配乳液涂料性能的因素,并对乳液的稳定性和固化速度,漆膜硬度等性能进行了评价。     

Hybridization of aqueous PU/epoxy resin via a dual self‐curing process

Amino‐terminated and carboxyl‐containing polyurethane (PU) is prepared by an isocyanate‐terminated PU prepolymer process. Carboxyl‐containing epoxy resin is obtained from a half‐esterification of epoxy resin with maleic anhydride. These two aqueous resins are obtained after neutralization with triethylamine and dispersion into water phase, respectively. A latent curing agent (TMPTA‐AZ) is prepared by a Michael addition of aziridine with trimethylolpropane triacrylate (TMPTA). A self‐curing system of PU/epoxy hybrid is obtained from a blending of these two aqueous resins with latent curing agent. PU/epoxy hybrid is derived from two self‐curing reactions on drying. The first curing for hybridization between PU amino groups with oxirane groups of epoxy resin is via a ring‐opening reaction and the secondary curing takes place on carboxyl groups of PU/epoxy hybrid with aziridine of TMPTA‐AZ. The final properties of these dual self‐cured PU/epoxy hybrids are reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rubber modified epoxy resin. II: Phase separation behavior

DGEBA (diglycidyl ether of bisphenol A)–ATBN (amine terminated butadiene acrylonitrile copolymer) blends exhibited upper critical solution temperature (UCST) behavior. Triethylene tetramine (TETA) was introduced as an amine curing agent of epoxy. The real-time phase separation behavior of ATBN-added epoxy system during cure was investigated using laser light scattering. SEM (scanning electron microscopy) and optical microscopy were also employed to observe the morphology of the epoxy blends. Since the DGEBA–ATBN blends showed UCST behavior, the degree of phase separation when cured at low temperature was higher than that when cured at high temperature. The domain correlation length increased as the curing temperature was lowered. Dynamic mechanical analysis (DMA) results indicated that the phase inversion occurred above 20 wt% of ATBN composition.     

新型非离子水性环氧分散体的制备及性能研究

采用聚醚胺与环氧树脂 E51为原料合成了非离子反应型两亲性乳化剂,以“相反转”法乳化环氧树脂 E20,考察了乳化工艺对乳化效果的影响。结果显示：乳化剂用量 14%、乳化温度 75~ 80 ℃、转速 3 000~3 500 r/min、添加 5%丙二醇丁醚助溶剂时效果最佳,制备的分散体平均粒径为 320 nm、黏度为 4 320 mPa·s,具有良好的贮存稳定性。该环氧分散体与市售水性环氧固化剂树脂复配,固化涂膜机械性能、耐水性和耐盐雾性优异。     

反应型非离子水性环氧乳液的制备及性能

选用环氧树脂E-51、邻苯二甲酸酐(PA)和聚乙二醇单甲醚(MPEG)为原料,合成了反应型非离子水性环氧树脂乳化剂,然后通过相反转法制备了水性环氧树脂乳液,研究了MPEG相对分子质量乳化剂用量对乳液稳定性和涂膜固化性能的影响。采用红外光谱(FT-IR)对乳化剂进行结构表征,通过透射电镜(TEM)观察了乳液中乳胶粒的形貌及其分布状态。结果表明:当MPEG相对分子质量为2 000,乳化剂用量为10%时,乳液稳定性良好,且制得的水性环氧树脂乳液的涂膜固化物具有优良的涂膜性能,铅笔硬度达2H,柔韧性为2 mm,耐冲击性达50 cm;耐水性优良。     

秸秆基环氧树脂乳液的制备及其涂膜性能

以脂肪醇聚氧乙烯醚(AEO-9)和十二烷基硫酸钠(SDS)复配为乳化剂,通过相反转技术乳化秸秆基环氧树脂,考察了复配乳化剂的HLB值、用量以及乳化温度和搅拌速率对乳液临界含水量Rf值、粒径及稳定性的影响,获得了如下较佳的乳化工艺条件:HLB值17,复合乳化剂用量8%,乳化温度35°C,搅拌速率800 r/min。以此工艺制得的乳液稳定性较好,平均粒径为1.57μm。以水性聚酰胺为固化剂,将此乳液制成清漆,固化后所得漆膜综合性能良好。     

Comparison of the effect of epoxy microspheres on the thermomechanical and rheological properties of an epoxy resin system

The rheological and thermomechanical behaviors of toughened epoxy resins filled with thermosetting microsized spherical particles were investigated. Two epoxy systems were used to prepare microspheres: a Bisphenol A‐type resin (EPON825) cured with 2,4‐diaminotoluene and a Bisphenol F‐based epoxy resin (PY306) crosslinked with diethyltoluenediamine. Both systems of microspheres were synthesized through dispersion polymerization and differed to each other in size, as evidenced by morphological analysis. These microparticles were blended, in different weight percents (10 and 20 wt%), with a matrix consisting of diglycidyl ether of Bisphenol A (EPON828) and 3,3′‐diaminodiphenylsulphone (3,3′DDS). Rheological behavior of the prepared blends was preliminarily studied. After cure, the dynamic‐mechanical properties of the composites were also investigated. Results indicated that the reactivity of the uncured blends, as well as the viscoelastic properties of crosslinked systems, are influenced not only by the nature and the amount of the microparticles introduced, but also, in a significant way, by their size. POLYM. ENG. SCI. 46:1739–1747, 2006. © 2006 Society of Plastics Engineers.     

Imidazole catalysis in the curing of epoxy resins

The high catalytic activity of imidazoles and particularly of 2-ethyl-4-methylimidazole (EMI) for the curing of epoxy resins and the properties of the resulting resins prompted this study concerned with the nature of the curing reaction. Epon 828 epoxy resin and the model compound phenyl glycidyl ether were used as starting materials with EMI, 2-methylimidazole, and dimethylbenzylamine as catalysts. During the curing of the resin at 50°C., the decrease in the infrared absorption of the epoxy band with time is accompanied by a decrease in the intensity of the imine band of the imidazole moiety, indicating its reaction with the epoxy group and its incorporation into the resin. The measurement of the residual epoxy content after curing for 24 hr. at 50 and 140°C. showed that the imidazoles were not more efficient in completing the epoxy reaction than dimethylbenzylamine. In the experiments with phenyl glycidyl ether the rate of reaction of the epoxy group with EMI was faster than the rate of polymerization, proving that the imidazole becomes permanently attached to the polymer chain. These results also suggest that the true catalytic species is not EMI but some addition product thereof. In comparative rate measurements the compound formed from equimolar quantities of EMI and phenyl glycidyl ether was found to be an excellent catalyst. The NMR analysis of the 1:1 and 1:2 adducts of EMI and phenyl glycidyl ether has shown that the second mole of phenyl glycidyl ether reacts with the ring nitrogen in the 3 position and not with the hydroxyl group of the mono adduct. By forming the bis adduct in this way the imidazole molecule acts as a crosslinking agent and at the same time introduces an alkoxide ion which can initiate further polymerization. It is very likely that this crosslinking is the process that leads to the superior physical and chemical properties (high heat deflection temperature, resistance to chemicals and oxidation) of the resins prepared with imidazoles as catalysts.     

双组分水性环氧防腐涂料的研制

采用双酚A型环氧树脂与非离子表面活性剂反应,合成了反应型水性环氧乳化剂,将具有表面活性的分子链段引入到环氧树脂分子链中,用相反转技术制备水性环氧树脂乳液。为了改善乳液与固化剂的相容性,合成了聚醚型水性环氧树脂固化剂,用其制备的双组分水性环氧防腐涂料具有优异的机械性能、耐水性、耐盐水性及耐盐雾性。     

Self‐curable system of an aqueous‐based polyurethane dispersion via a ring‐opening reaction of azetidine end groups

An azetidine (AZT) containing compound, 3‐azetidinyl propanol was synthesized from methyl acrylate with 3‐amino‐1‐propanol in a four‐step reaction. It was introduced into an isocyanate‐terminated carboxylic acid containing polyurethane (PU) prepolymer as the end group. A single‐component, AZT‐terminated self‐curable aqueous‐based PU dispersion was obtained from the water dispersion process after it was neutralized with triethylamine. Its carboxylic groups served not only as the internal emulsifier stabilizing the aqueous PU dispersion but also as PU self‐curing sites toward its AZT end groups via a ring‐opening reaction. The curing reaction took place on drying and resulted in polymeric network structure formation among the polymers. The performance properties of this self‐cured PU were evaluated in this study. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4383–4393, 2006     

Influence of rubber on the curing kinetics of DGEBA epoxy and the effect on the morphology and hardness of the composites

The influence of the end groups of two liquid rubbers on curing kinetics, morphology, and hardness behavior of diglycidyl ether of bisphenol-A based epoxy resin (DGEBA) has been studied. The rubbers are silyl-dihydroxy terminated (PDMS-co-DPS-OH) and silyl-diglycidyl ether terminated (PDMS-DGE). Crosslinking reactions, investigated by shear rheometry, ranged 90–110 °C, using a constant concentration (5 phr) of liquid rubbers and 1,2-Diamino cyclohexane (1,2-DCH) as hardener agent. The gel time, t _gel, of the neat epoxy significantly decreased when adding the elastomers, more so for the silyl-dihydroxy terminated elastomer; at 110 °C the reaction was nearly complete before rheological test started. The results suggest that the elastomers induced a catalytic effect on the curing reaction. Scanning electron microscopy revealed phase separation of the elastomer during the curing reaction with rubber domains about 5 μm size. However, the DGEBA/dihydroxy terminated elastomer composite cured at 110 °C exhibited a homogenous morphology, that is, the rapid reaction time would not allow for phase separation. Water contact angle tests evidenced either more hydrophilic (silyl-diglycidyl ether terminated rubber) or more hydrophobic (silyl-dihydroxy terminated rubber) behavior than the neat epoxy. The latter effect is attributed to the presence of aromatic rings in the backbone structure of PDMS-co-DPS-OH. Microindentation measurements show that the elastomers significantly reduced the hardness of the epoxy resin, the DGEBA/ether terminated composite exhibiting the lowest hardness values. Moreover, hardness increased as reaction temperature did, correlating with a reduction of microdomains size thus enabling the tuning of mechanical properties with reaction temperature.     

Reinforcing effect of organoclay in rubbery and glassy epoxy resins,part 1: Dispersion and properties

The reinforcing effect of organoclay in two epoxy matrices, one rubbery and one glassy, was studied. The rubbery and glassy epoxy matrices were chosen to have a very similar chemistry to minimize its impact on the comparison of properties. The epoxy resin was EPON? 828, and the two hardeners were amine‐terminated polyoxypropylene diols, having different average molecular weights (MW) of 2000 and 230 g/mol, namely Jeffamine® D‐2000 and Jeffamine® D‐230, respectively. The nanocomposites were prepared with the organoclay Cloisite® 30B from Southern Clay Products. The quality of dispersion and intercalation/exfoliation was analyzed by means of X‐ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the curing reactivity and the thermal stability of the epoxy resin systems, respectively. Tensile properties and hardness of epoxy resin and epoxy nanocomposites were measured according to ASTM standards D638‐02 and D2240‐00, respectively. Fracture surfaces were also analyzed by FEGSEM. These two epoxy systems as well as their nanocomposites display totally different physical and mechanical behavior. It is found that the quality of clay dispersion and intercalation/exfoliation, and the mechanical behavior of the glassy and rubbery epoxy nanocomposites are distinct. The results also indicate that the presence of the clay does not significantly affect the T_g of either the rubbery or the glassy epoxy; however, the fracture surface and mechanical properties were found to be influenced by the presence of nanoclay. Finally, several different reinforcing mechanisms are proposed and discussed for the rubbery and glassy epoxy nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Poly(phenylene ether)/epoxy thermoset blends based on anionic polymerization of epoxy monomer

Low molar mass poly (phenylene ether) (LMW‐PPE) with phenol‐reactive chain ends was used as modifier of epoxy thermoset. The epoxy monomer was diglycidylether of bisphenol A (DGEBA), and several imidazoles were used as initiators of anionic polymerization. The curing and phase separation processes were investigated by different techniques: Differential Scanning Calorimetry, Size Exclusion Chromatography, and Light Transmission measurements. The final morphology of blends was observed by Environmental Scanning Electron Microscopy and Transmission Electron Microscopy. The epoxy network is obtained by imidazole initiated DGEBA homopolymerization. Initial LMW‐PPE/DGEBA mixtures show an UCST behavior with cloud point temperatures between 40 and 90°C. PPE phenol end‐groups can react with epoxy, leading to a better interaction between phases. The curing mechanism and phase separation process are not influenced by the chemical structure of initiators, except when reactive amine groups are present. The phase inversion is observed at 30 wt % of PPE. The mixtures with amine‐substituted imidazole present important differences in the initial miscibility and curing process interpreted in terms of fast room temperature amine‐epoxy reaction during blending. Final domain size is affected by this prereaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2678–2687, 2004     

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.     

水性环氧乳化型固化剂(AEEC)乳化特性研究

试验合成了一种水性环氧乳化型固化剂(AEEC),该固化剂是既亲水又亲油的两亲性化合物,除具有与环氧树脂(EP)的环氧基起交联反应的固化性能外,对液体EP具有良好的乳化能力。将AEEC与EP以适当比例混合,不加其它乳化剂,通过相反转法制备出稳定的EP水乳液。试验结果表明:在EP/AEEC固化剂/水三元体系中,当w(水)=30%~40%时,可以完成相反转过程;通过相反转法配制的乳液,乳液粒径小(1μm左右),粒径分布较窄,乳液稳定性良好;当固化剂成盐率为50%~60%时,乳液经离心(3 000 r/min)分离30 min不分层,固含量为10%的乳液室温静置一周不分层。     

非离子型水性环氧树脂乳化剂的合成及特性研究

采用端甲氧基聚乙二醇-马来酸酐-E-44多元共聚物合成非离子型水性环氧树脂乳化剂。利用红外光谱对产物结构进行表征。以相反转技术乳化环氧树脂E-44,研究了乳化剂合成过程中酯化率与反应时间、乳化剂用量对乳液稳定性的影响,并对其固化性能进行了探讨。结果表明:端甲氧基聚乙二醇-马来酸酐与环氧树脂E-44在110~120℃反应5 h,酯化率达98%以上;乳化剂用量在16.5%~20.0%时其乳化效果及所制得乳液的稳定性最好。