Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC

Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry     

Adhesive and thermal characteristics of maleimide-functional novolac resins

A novel, addition-curable maleimide-functional novolac phenolic resin was evaluated for adhesive properties such as lap shear strength and T-peel strength using aluminium adherends, when thermally self-cured and cocured with epoxy resins. The adhesive properties of the self-cured resin, although inferior at ambient temperature, improved at high temperature and were found to depend on the cure conditions. When cocured with epoxy resin, the adhesive properties improved significantly and showed a strong dependence on the nature of the epoxy resin used, on the stoichiometry of the reactants, on the concentration of imide groups in the phenolic resin, and on the extent of polymerization of the maleimide groups. Optimum adhesive properties were obtained for novolac resins with a moderate concentration of maleimide groups, taken on a 1 : 1 hydroxyl–epoxy stoichiometry with a novolac epoxy resin. In comparison to the conventional novolac, the imide–novolac contributed to improved adhesion and better adhesive property retention at higher temperature when cured with the novolac–epoxy resin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 695–705, 1999     

耐热环氧聚氨酯复合涂层的制备与表征

通过苯甲酸改性酚醛环氧树脂得到了含羟基的酚醛环氧树脂,再经固化剂甲苯二异氰酸酯三聚体和邻苯二甲酸酐固化后,得到了耐热的环氧聚氨酯复合涂层.通过改变苯甲酸改性酚醛环氧树脂的开环率,研究了在聚氨酯体系中引入酚醛环氧树脂的量对其耐热性能的影响.以傅里叶变换红外光谱研究了苯甲酸改性酚醛环氧树脂及其固化过程,以热重分析研究了酚醛...     

Aging and Thermal Studies on Epoxy Resin Modified by Epoxidized Novolacs

Epoxy resins are thermosetting polymers widely used for polymer composites, adhesives, high performance coatings, potting and encapsulation, and numerous other applications. These resins have excellent mechanical and electrical properties, low cure shrinkage, and good adhesion to most substrates. This study is an attempt to improve the thermal and aging characteristics of epoxy resin by blending with other multifunctional epoxies such as EPN and ECN. Bis-phenol A epoxy resins containing 2.5 to 20 wt% of epoxy novolac were cured in the presence of a polyamide hardener and tested for thermal and mechanical properties, hardness, water absorption, etc. Blends containing 10 to 15 wt% of epoxy novolac show substantial improvement in properties such as tensile strength, elongation, and energy absorbed to break. The novolac derived from p-cresol was better than that based on phenol in enhancing the properties. TGA, DSC, and DMA were employed for studying the thermal properties of the modified resin. The study reveals that modification using epoxy phenol and p-cresol novolac resins (EPN and ECN, respectively) improves the aging characteristics of the epoxy resin in addition to overall improvement of the mechanical properties.     

New type of phenolic resin: Curing reaction of phenol‐novolac based benzoxazine with bisoxazoline or epoxy resin using latent curing agent and the properties of the cured resin

In this study, we aimed to reduce the cure time, and to lower the cure temperature of the benzoxazine compound. Therefore, curing reaction of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent and the properties of the cured resins were investigated. The cure behavior of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent was monitored by differential scanning calorimetry and measurements for storage modulus (G′). The properties of the cured resin were estimated by mechanical properties, electrical insulation, water resistance, heat resistance, and flame resistance. As a result, it was confirmed that by using the latent curing agent, cure time of benzoxazine and bisoxazoline or epoxy resin was reduced, and cure temperature was lowered. And it was found that the curing reaction using phenol‐novolac based benzoxazine (Na) as the benzoxazine compound could proceed more rapidly than that using bisphenol‐A based benzoxazine (Ba) as the benzoxazine compound. However, the cured resins from Ba and bisoxazoline or epoxy resin using the latent curing agent showed good heat resistance, flame resistance, and mechanical properties compared with those from Na and bisoxazoline or epoxy resin using the latent curing agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Relationship between viscoelastic properties and gelation in the epoxy/phenol‐novolac blend system with N‐benzylpyrazinium salt as a latent thermal catalyst

A study of viscoelastic properties and gelation in epoxy/phenol‐novolac blend system initiated with 1 wt % of N‐benzylpyrazinium hexafluoroantimonate (BPH) as a latent cationic thermal initiator was performed by analysis of rheological properties using a rheometer. Latent behavior was investigated by measuring the conversion as a function of curing temperature using traditional curing agents, such as ethylene diamine (EDA) and nadic methyl anhydride (NMA) in comparison to BPH. In the relationship between viscoelastic properties and gelation of epoxy/phenol‐novolac blend system, the time of modulus crossover was dependent on high frequency and cure temperature. The activation energy (E_c) for crosslinking from rheometric analysis increased within the composition range of 20–40 wt % phenol‐novolac resin. The 40 wt % phenol‐novolac (N40) to epoxy resin showed the highest value in the blend system, due to the three‐dimensional crosslinking that can take place between hydroxyl groups within the phenol resin or epoxides within the epoxy resin involving polyaddition of the initiator with BPH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2299–2308, 2001     

我国特种环氧树脂生产和研究进展

介绍了我国环氧树脂的生产消费概况,分析了溴化环氧树脂、邻甲酚醛环氧树脂、双酚F环氧树脂、酚醛环氧树脂和双酚A酚醛环氧树脂等特种环氧树脂的生产和研究进展,提出了我国发展环氧树脂的见解.     

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.     

DOPO与邻甲酚醛环氧树脂反应特性的研究

通过环氧值滴定和红外光谱研究反应型含磷阻燃剂(DOPO)与邻甲酚醛环氧树脂的反应特性,确定其最佳反应条件。实验结果表明:120℃下添加20%催化剂三苯基膦,反应120 min可获得最佳效果。红外谱图进一步确认DOPO与邻甲酚醛环氧树脂反应进行的程度及DOPO含磷环氧树脂的初步结构。采用DTA分析方法研究DOPO与邻甲酚醛环氧树脂的反应动力学,测得DOPO与邻甲酚醛环氧树脂反应的动力学参数lnA0为58.63,表观活化能E为298.51 kJ/mol,反应级数n为0.97。     

Curing characteristics of epoxy resin systems that include a biphenyl moiety

The curing characteristics of epoxy resin systems that include a biphenyl moiety were investigated according to the change of curing agents. Their curing kinetics mainly depend on the type of hardener. An autocatalytic kinetic reaction occurs in epoxy resin systems with phenol novolac hardener, regardless of the kinds of epoxy resin and the epoxy resin systems using Xylok and DCPDP (dicyclopentadiene‐type phenol resin) curing agents following an nth‐order kinetic mechanism. The kinetic parameters of all epoxy resin systems were reported in terms of a generalized kinetic equation that considered the diffusion term. The fastest reaction conversion rate among the epoxy resin systems with a phenol novolac curing agent was obtained in the EOCN‐C epoxy resin system, and for systems with Xylok and DCPDP hardeners, the highest reaction rate values were obtained in NC‐3000P and EOCN‐C epoxy resin systems, respectively. The system constants in DiBenedetto's equation of each epoxy resin system with different curing agents were obtained, and their curing characteristics can be interpreted by the curing model using a curing agent as a spacer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1942–1952, 2002     

水性环氧树脂/双氰胺体系的研究

多官能团酚醛环氧树脂F-51与适量二乙醇胺反应,制得一种分子中含环氧基和亲水基团的改性F-51环氧树脂,该树脂成盐后具有良好亲水性。以双氰胺为固化剂,对体系的反应性及固化物主要性能进行研究,结果表明固化反应起始温度显著降低,固化膜的硬度达6H,并具有很强的附着力。     

新型含磷环氧树脂的合成及其反应动力学研究

将9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)与邻甲酚醛环氧树脂进行加成反应制得了含磷环氧树脂,并用FT-IR和NMR对其结构进行了表征,确认了该含磷环氧树脂的结构。采用DSC分析方法研究了DOPO与邻甲酚醛环氧树脂的反应动力学,得到两者反应的表观活化能Eα为53.457kJ/mol,反应级数n为0.93。     

输油管线用熔结环氧粉末涂料的制备

采用线型酚醛环氧树脂(ENR)、环氧树脂E-12、固化剂JECP-02B制备了输油管线用熔结环氧粉末涂料。考察了线型酚醛环氧树脂与环氧树脂E-12质量比对涂料性能的影响,以及固化剂JECP-02B、流平剂GLP588和固化促进剂2-甲基咪唑对固化行为的影响,用红外光谱分析了固化前后树脂的变化,m(ENR)/m(E-12)=(75/25)~(25/75)、m(固化剂)/m(环氧树脂)=1/4、m(流平剂)/m(环氧树脂)=2/100、m(2-甲基咪唑)/m(环氧树脂)=(0.1~0.15)/100时,涂层性能达到输油管线防腐指标(SY/T 0315-97)。长庆化工有限责任公司用该技术扩大生产约10 t环氧粉末涂料,用于长庆油田输油管线的防腐,产品满足了1.5 m in/230℃快速固化的施工要求。     

Hybrid Polymer Networks of Epoxy Resin and Substituted Phenolic Novolacs

Hybrid polymer networks of diglycidyl ether of bisphenol (DGEBA) resin and phenolic novolac resins were prepared and tested for mechanical properties, hardness, and water absorption. The novolacs employed were based on each of phenol and substituted phenols such as p-cresol, t-butyl phenol, and cardanol. Cardanol is the main constituent of cashew nut shell liquid (CNSL), a renewable resource. Blends containing 10–15 wt% of novolac resin show substantial improvement in properties. These properties show a declining trend with higher novolac loading. The stoichiometric ratio between phenol and formaldehyde in the novolacs was optimized (1:0.8) for maximum property enhancement. The property profiles of the epoxy/novolac networks show that novolacs are effective modifiers for commercial epoxy resin. Incorporation of novolacs of substituted phenols results in relatively greater improvement in energy absorption during failure.     

Nano-phase structures and mechanical properties of epoxy/acryl triblock copolymer alloys

Phase structures and mechanical properties of epoxy/acryl triblock copolymer alloys using several curing agents were studied. PMMA-b-PnBA-b-PMMA triblock copolymers synthesized by living anionic polymerization were applied as the toughening modifiers for the epoxy resins. An aromatic amine, an acid anhydride and an anionic polymerization catalyst as curing agents resulted in macro-phase separation in the epoxy/triblock copolymer blends during the cure process. However, a phenol novolac as the curing agent created nano-phase structures in the epoxy blends. The size of the spherical phases or cylindrical phases was about 40 nm in diameter, and the main component in the nano-phases was the PnBA of the triblock copolymer. The fracture toughness of the epoxy/triblock copolymer alloys with the nano-cylindrical phases reached 2530 J/m². The fracture toughness was more than twenty fold relative to the unmodified epoxy resin, and was equivalent to the toughness of polycarbonates.     

Synthesis of high purity o-cresol formaldehyde novolac epoxy resins

Summary The content of total chlorine in o-cresol formaldehyde novolac epoxy resin (CNE), the main resin component for encapsulation formulation, affects the reliability of semi-conductor device greatly and it is one of the major criteria used by the electronic industry in measuring the quality of resins. A new process which synthesizes a high purity CNE with less than 300 ppm total chlorine content has been developed. This high purity resin has provided an extended device life under the accelerated stress test condition.     

Thermo-mechanical properties of rosin-modified o-cresol novolac epoxy thermosets comprising rosin-based imidoamine curing agents

Rosin-modified o-cresol novolac epoxy resin (AEOCN) was synthesized by condensation of rosin acid with o-cresol formaldehyde novolac resin (AOCN). The AEOCN resin was further epoxidized using epichlorohydrin and sodium hydroxide. Rosin-based imidoamine curing agents (IAMDK, IASDK, and IAEDK) were also prepared by reacting dimaleopimaryl ketone (DMPK), a dimerized rosin product with aromatic diamines. The chemical structures of all synthesized products were confirmed by FTIR, ¹H-NMR, ¹³C-NMR, and DEPT-135° spectroscopic techniques. The curing process of rosin-modified epoxy cured with imidoamine crosslinkers was studied using differential scanning calorimetry (DSC) and the results were compared to o-cresol novolac epoxy resin (EOCN) and some previously reported commercial-based systems. The thermal and mechanical properties of the cured epoxy thermosets were determined using a thermogravimetric analyzer (TGA) and a universal testing machine (UTM), respectively. The chemical resistance analysis was carried out by immersing cured epoxy coated panels in 1M NaOH, 1MHCl, and 1M NaCl solutions. The results were evaluated in terms of % weight loss method and the morphological changes that appeared due to chemical exposure were also investigated via scanning electron microscopy (SEM). This study presents the economical synthetic approach towards high-performance bio-based epoxy coating materials impending to replace some of the petrochemical compounds in coating industries.     

酚醛环氧乙烯基酯树脂碳纤维复合材料的制备及性能研究

把酚醛环氧乙烯基酯树脂分别与固化剂过氧化氢异丙苯(CHP)、过氧化苯甲酸叔丁酯(TBPB)、过氧化二异丙苯(DCP)进行混溶,模压成型,碳纤维层合板,进行了力学性能和热稳定性的研究。结果表明,研究的碳纤维-酚醛环氧基乙烯基酯树脂复合材料具有非常好的力学性能及热稳定性,弯曲强度达到1 400～1 900 MPa。