Cure kinetics of biphenyl epoxy resin system using latent catalysts

The investigation of the cure kinetics of a biphenyl epoxy–phenol resin system with different kinds of latent catalysts was performed by differential scanning calorimetry using an isothermal approach. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicated that the curing reaction of the biphenyl epoxy resin system in this experiment proceeded through an autocatalytic kinetic mechanism, irrespective of the kind of catalyst. The epoxy resin system with acid/diazabicycloundecene (DBU) salt as the latent catalyst showed a second overall reaction order; however, a third reaction order was represented for microencapsulated triphenylphosphine (TPP). The storage stability tests for these systems were performed, and a good shelf life was observed in the epoxy resin system with pyromellitic acid/DBU salt, trimellitic acid/DBU salt, and microencapsulated TPP as the latent catalyst. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2711–2720, 2001     

Curing of epoxides with O,O‐di‐t‐butyl phenylphosphonate as thermally latent initiator

The polymerization of glycidyl phenyl ether (GPE) was examined with O,O‐di‐t‐butyl phenylphosphonate (BP) as an initiator in the presence of several Lewis acids, ammonium salts, and methyl cyanoacetate. BP served as an excellent thermally latent initiator in the polymerization of GPE in the presence of ZnCl₂ and Zn(acac)₂. Epikote 828 was cured with BP (5 mol %) in the presence of ZnCl₂ at 150°C to afford the solvent‐insoluble gelled epoxy resin quantitatively, which was thermally more stable than was the one cured without ZnCl₂. No curing took place at room temperature for 7 months. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2347–2351, 2001     

A novel latent initiator for cationic polymerizations of epoxides: Composite catalysts containing aluminum complexes phase‐separated in epoxides

A novel latent initiator for cationic polymerizations of epoxides heterogeneous aluminum complex/phenol initiator (HAP) is reported. Phase transitions are newly employed for realizing the latent property. The initiator consists of 4,4′‐dihydroxydiphenylsulfone and aluminum tris(alkyl acetoacetate), with the alkyl group containing more than 18 carbons. The composite initiator is phase‐separated and dispersed uniformly in epoxy resins at room temperature. When the mixture is heated to a temperature greater than 70°C, the composite initiator makes clear mixtures with epoxy resins because of the phase change in the aluminum complexes. Homogeneous epoxy resins containing these composite initiators are ready for various types of processing, including impregnation and injection. Gelation occurs rapidly at temperatures greater than 100°C. The phase change in the initiator makes it possible for the epoxy compounds to have a long storage stability at room temperature and a high curing speed at greater than 100°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1046–1053, 2002     

光引发阳离子聚合及其在环氧树脂固化研究中的进展

从光引发阳离子聚合的特点、常见阳离子型光敏引发剂及其引发聚合机理、光引发环氧树脂阳离子聚合体系及发展前景等几个方面进行了简要概述。     

Novel piperidinium salts as latent initiators for cationic polymerization of epoxide and vinyl ether

Novel dibenzylpiperidinium salts with nonnucleophilic anions (DBPi‐SbF₆, DBPi‐PF₆) have been prepared as latent cationic initiators. Utility of these salts in the photo and thermal‐induced cationic polymerizations of epoxide and vinyl ether monomer systems has been studied. The new initiator, DBPi‐SbF₆ showed good solubility, high reactivity, and high thermal latency for polymerizations of epoxide and vinyl ether monomers with only 1 wt % of concentration. Cationic polymerization of vinyl ether monomer was significantly faster than epoxide monomer by the synthesized initiators. This article describes the synthesis, characterization, and activity of novel initiators. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

含有潜伏性催化剂的环氧树脂/酸酐体系的研究

使用固态聚胺与疏水性微粒子WS-12制备出一种潜伏性催化剂,评价了该催化剂在环氧树脂/甲基六氢苯酐固化体系中的催化固化作用。在25～50℃的范围内本固化体系长时间黏度变化平稳,而在150℃以上时具有高效的催化效果,显示出该催化剂具有优异的潜伏功能。该催化固化体系能适合于各种黏度的环氧树脂,当使用一种低黏度环氧树脂时,即m(环氧树脂6002):m(甲基六氢苯酐):m(潜伏性催化剂)=100:70:3时,其固化物显示出最佳的力学性能。     

Cure behavior of epoxy resins with different kinds of onium salts as latent thermal catalysts

Two latent thermal catalysts, Dimethyl phenacylsulfonium hexafluoroantimonate, (Benzyl‐S), and triphenyl benzyl phosphonuim hexafluoroantimonate, (Benzyl‐P), were synthesized. Both these synthesized catalysts fulfill requirements for a rapid cure at a moderately elevated temperature in curing the epoxy resins of neat 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane‐carboxylate, (EPC), neat 2,2‐bis(4‐glycidyloxyphenyl)propane, (EPA), and their hybrid resin. The cure behavior of these resins cured individually with the synthesized catalysts was studied through correlation of the in situ FTIR (Fourier transform infrared) spectroscopy and DSC (differential scanning calorimetry) dynamic scanning results. Catalyst Benzyl‐S is more effective than Benzyl‐P. Resin EPC is significantly more sensitive to the latent thermal catalysts than the EPA resin. Activated chain‐end (ACE) and activated monomer (AM) mechanisms are basically adopted. Isomerization occurs in the neat EPA cure system, and transesterification takes place in all systems containing EPC species in the latter curing stage. Most importantly, ester linkages C?O in the hybrid systems have been destroyed at some time during the curing process, but some reformed at the latter curing stage. It is most likely that the C?O linkage in the EPC segments was attacked by the activated chain‐end of the epoxide group of EPA species to form a five‐membered cyclic acetal. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3539–3551, 2001     

PVC树脂聚合用有机过氧化物引发剂

介绍了目前国内外引发剂的使用及开发方向,并对引发剂的选择及其对树脂质量的影响进行了讨论。     

聚合引发剂TX23替代EHP的应用对比

对聚合引发剂TX23替代EHP的可行性进行了论证并试用,介绍了Tx23和EHP引发剂的性能和分解原理,对使用TX23和EHP引发剂生产的树脂的质量、加工性能、母液水等性能进行了对比,找出优缺点,进而拓宽PVC树脂聚合使用的引发剂种类,提高了PVC树脂产品的质量。     

潜伏性环氧固化剂研究进展

按固化条件的不同分别介绍了加热型、光固化型、潮湿型潜伏性环氧固化剂,列举了各类固化剂的典型代表及其性质,展望了今后潜伏性固化剂的研究重点和发展趋势。     

Photoinitiated cationic polymerization of epoxides

Difunctional epoxy monomers have been polymerized cationically by UV irradiation in the presence of a triarylsulfonium photoinitiator. The curing process was followed quantitatively by monitoring the disappearance of the epoxy group by infrared spectroscopy and the insolubilization and hardening of the resin upon UV exposure. The addition of epoxidized soyabean oil (ESO) to an aromatic diepoxide was shown to accelerate the crosslinking reaction with formation of a tight polymer network. The photoinitiated copolymerization of ESO with a cycloaliphatic diepoxide proceeds extensively and leads within seconds to a fully cured insoluble material showing increased hardness, flexibility and scratch resistance. Interpenetrating polymer networks have been generated by a short UV‐irradiation of blends of acrylate and epoxy monomers. © 2001 Society of Chemical Industry     

Novel dibenzocycloheptenyl phosphonium salts as thermolatent initiator in cationic polymerization

In this study, novel thermolatent cationic initiators based on dibenzocycloheptenyl phosphonium salts ( 1a , 1b , 1c , 1d , 2a , and 3a ) were synthesized and their efficiency was examined in bulk polymerization of glycidyl phenyl ether (GPE). The polymerization of GPE was performed with 1 mol % of dibenzocycloheptenyl triphenylphosphonium salts ( 1a – 1d ) with different counter anions (SbF₆^?, PF₆^?, AsF₆^?, and BF₄^?) at 25–200°C for 1 h. The order of initiator activity was found as 1a > 1d > 1b > 1c . To examine the effect of phosphine moiety, the activity of 1a was compared with dibenzocycloheptenyl‐tri‐n‐butylphosphonium hexafluoroantimonate ( 2a ). The order of initiator activity was observed as 1a > 2a. The initiator activity of 1a was compared with that of 10,11‐dihydro‐dibenzocycloheptenyltriphenylphosphonium hexafluoroantimonate ( 3a ) to understand the effect of extended conjugation in dibenzocycloheptenyl ring. In general, with the increase in the polymerization temperature, conversion (%) also increases. The solubility of initiators in various solvents and epoxy monomers was also examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Analyzing the real advantages of bifunctional initiator over monofunctional initiator in free radical polymerization

Monofunctional initiators are extensively used in free radical polymerization. To enhance productivity, a higher temperature is usually used; however, this leads to lower molecular weights. Bifunctional initiators can increase the polymerization rate without decreasing the average molecular weight and this can be desirable. A bifunctional initiator is an important issue to be investigated, and it is of great interest to industries. The objective of this work is to study polymerization reactions with mono‐ and bi‐functional initiators through comprehensive mathematical models. Polystyrene is considered as case study. This work collects and presents some experimental data available in literature for polymerization using two different types of bifunctional initiators. Model prediction showed good agreement with experimental data. It was observed that the initial initiator concentration has a huge impact on the efficiency of initiators with functionality bigger than one and high concentrations of bifunctional initiator make the system behave as if it were a system operating with monofunctional initiator. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Externally stimulated initiator systems for cationic polymerization

At present, there is growing interest in polymerizations initiated by external stimulation, such as photoirradiation, heating or high energy irradiation. Since many industrially important monomers can only be polymerized by a cationic mechanism, much effort has been made to develop systems that produce initiating cations upon external stimulation. In this article, the latest developments in externally stimulated systems for cationic polymerization are reviewed. The goal is, furthermore, to show differences as well as parallels between systems for different modes of external stimulation.     

Encapsulation of imidazole with synthesized copolymers for latent curing of epoxy resin

Anisotropic conductive film (ACF) is an essential component in the manufacture of liquid crystal displays, and an imidazole–epoxy resin system that exhibits a latent behavior is generally used as an adhesive in the ACF. In this study, a new copolymer was synthesized using methacrylic acid and dodecyl methacrylate, and this copolymer was used to encapsulate an imidazole curing agent to endow the ACF with latent behavior. A spray‐drying method was used in the encapsulation process, and this encapsulated imidazole was mixed with epoxy resin to form an imidazole–epoxy resin system. A comparison with our previous results showed that a smaller amount of polymeric material could be used in the encapsulating process, and a superior latent behavior could be obtained. © 2016 Society of Chemical Industry     

潜伏性环氧树脂固化促进剂M-Cd的合成及其应用

采用间苯二胺和溴化镉合成了一种具有潜伏性的环氧树脂固化促进剂M－Cd它是一种络合物，将它应用于二氰二胺／环氧树脂脂固化体系的高温结构粘剂中，能够显著地降低粘剂的固化温度，缩短固化时间，本文还讨论了合成该促进剂主要成分的投料比，应用于二氰二胺／环氧树脂固化体系的高温结构胶粘剂中该促进剂的使用量以及固化条件对粘剂力学性能的影响，同时还考核了应用该促进剂M的高温结构胶粘剂的综合性能。     

合成引发剂技术在聚合装置上的应用

介绍了釜内直接合成引发剂的生产过程及影响合成引发剂收率的因素。该工艺合成的引发剂是在釜内由CatC(氯甲酸乙酯 )、CatD(双氧水 )、CatE(氢氧化钠 )进行反应生成的过氧化物EHP。该引发剂是直接合成的 ,不存在诱导期 ,聚合反应速率平稳。其成本为 5 .95元 / (t·PVC) ,远低于配制的引发剂 ,这也代表着过氧类引发剂的另一种使用方法 ,具有广泛的市场前景。     

Rapid polymerization initiated by redox initiator for the synthesis of polyaniline nanofibers

High quality polyaniline nanofibers have been synthesized by a rapid polymerization of aniline using ammonium peroxydisulfate (APS)/Fe²⁺ redox initiator as the oxidant without any hard or soft templates. The addition of Fe²⁺ in conventional polymerization system plays an important role in changing the bulk morphologies of polyaniline from irregular particle agglomerates to nanofibers. Open-circuit potential measurements indicate that the rate of polymerization of aniline with the aid of Fe²⁺ ions has a substantial increase. The influences of synthetic parameters, such as the concentrations of aniline, dopant, and redox initiator, and reaction time, on the sizes and morphologies of polyaniline nanostructures have been investigated for elucidating the formation of polyaniline nanofibers. Fourier transform infrared spectrum, UV-vis spectrum, and cyclic voltammograms reveal that the molecular structures and electrochemical properties of polyaniline nanofibers do not differ significantly from that of conventional polyaniline.     

双官能团引发剂引发甲基丙烯酸甲酯的聚合速率

研究了双官能团引发剂2,5-双(2-乙基己酰过氧化)-2,5-二甲基己烷（TX-141）引发甲基丙烯酸甲酯（MMA）的自由基聚合动力学,考察了引发剂浓度、聚合温度对聚合动力学的影响.结果表明：该体系的聚合活化能为91 kJ•mol^-1左右,计算得到TX-141引发剂的分解活化能为140 kJ•mol^-1左右,与实验值接近;TX-141引发剂的反应级数约为0.72,说明MMA聚合终止基元反应中单基和双基终止并存.同时与相似半衰期的过氧化二苯甲酰（BPO）比较,发现当TX-141引发剂浓度为BPO的1/2时,两者在各个聚合温度下的聚合动力学曲线几乎相同;但相对分子质量有明显增加,随聚合转化率增加,TX-141与BPO引发的聚合物数均分子量之比从1.2变化到1.33;由TX-141引发的聚合物低转化率时DSC曲线出现放热峰,而高转化率以及BPO引发的聚合物则没有.说明双官能团引发剂TX-141引发聚合时,在低转化率下TX-141引发剂的2个过氧键没有全部断裂,随聚合进行,断裂程度加深.     

New tetrafunctional epoxy resin system with increased shelf life

Chlorine‐ and methyl‐substituted aromatic diamines based on diaminodiphenylmethane were epoxidized and characterized. The effect of different substituents on epoxidation was studied. The cure studies of the two new tetrafunctional resins in comparison with unsubstituted resin N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) was carried out by DSC with 3,3′‐dichloro‐4,4′diaminodiphenylmethane (o‐DCDDM; 30% w/w) as a common curing agent. The mechanical properties such as flexural, Izod impact, heat distortion temperature (HDT), of such cured neat resins were also studied. The results of the cure studies indicate that the substitution of the α‐hydrogen of the resin by chlorine or methyl group decreases the reactivity of the resin leading to an increase in the shelf life. This study also indicates that the functionality of the resin plays a pivotal role in the reactivity and thus the shelf life of an epoxy resin system. The results of the mechanical properties of the neat resin casts obtained by subjecting to a common cure schedule when compared with the unsubstituted resin showed a decrease in impact strength, which is obvious because of the presence of a bulky pendant group but the impact strength was higher than that of the TGOS30 resin system. Results of flexural strength of the different substituted neat resin casts did not show much of a deviation from that of the unsubstituted resin system. The HDT results indicate no significant difference in the values of the unsubstituted resin vis‐a‐vis with substituted resin systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2790–2801, 2004