Curing kinetics and mechanism of novel high performance hyperbranched polysiloxane/bismaleimide/cyanate ester resins for resin transfer molding

Curing kinetics and mechanism determine the structure and property of thermosetting resins and related composites. The curing kinetics and mechanism of a novel high performance resin system based on hyperbranched polysiloxane (HBPSi), 2,2′‐diallylbisphenol A modified bismaleimide (BD), and cyanate ester (CE) resins for Resin Transfer Molding (RTM) technique were systemically studied by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) spectra, and torque rheometer. Results show that the addition of HBPSi to BD/CE resin not only decreases the initial curing temperature and apparent activation energy, but also changes the curing mechanism, and thus the structure and properties of resultant crosslinked networks. An “Interpenetrating network (IPN)‐coupling structure” is proposed to be formed in the HBPSi/BD/CE system, which is different from traditional “IPN” structure in BD/CE resin. The simulation of curing reaction suggests that the variety of the curing activity leads to the difference between the curing behaviors of BD/CE and HBPSi/BD/CE resins, which is in good agreement with FTIR and DSC analyses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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 %。     

Study on Curing Kinetics and Thermal Degradation Kinetics of Hyperbranched Poly(Trimellitic Anhydride Ethylene Glycol) Epoxy (HTME)/Diglycidyl Ether of Bisphenol-A Epoxy Hybrid Resin

Hyperbranched poly(trimellitic anhydride ethylene glycol) epoxy (HTME) not only has relatively low viscosity and high molecular weight but also is a functional additive of enhancement and toughness and is used in the thermosetting resin field widely. The curing kinetics and thermal degradation kinetics of HTME/diglycidyl ether of bisphenol-A epoxy hybrid resin were studied in detail using differential scanning calorimetry and thermogravimetric analysis technique, respectively, by the Coats-Redfern model. The effect of molecular weight or generation and content of HTME on activation energy, reaction order, curing time, and curing reaction were discussed and analyzed, and the results indicated that HTME could accelerate curing reaction and reduce activation energy and reaction order of the curing reaction.     

A new supertough epoxy formulation with high crosslinking density

A highly crosslinked thermosetting epoxy resin was modified by a reactive blending process carried out in the presence of bisphenol-A polycarbonate (PC). FTIR spectroscopy investigations demonstrated that the presence of PC in the blend decreases the reactants conversion after the curing and postcuring processes. Moreover, it was found that the fracture toughness of this blend system increases markedly by increasing the PC content in the blend. No evidence of phase separation of the minor component during the crosslinking reaction steps was observed.     

环氧树脂聚酰胺网络体系性能研究

用红外光谱法表征了4种聚酰胺固化剂与环氧树脂按等当量配比,在一定条件下的固化反应过程。DSC法测定了其固化反应活性。桐马聚酰胺/环氧树脂固化体系较聚酰胺650/环氧树脂固化体系的固化活性大大提高,同时测定了该固化产物的热失重(TG)及玻璃化温度(Tg),对该固化物的热稳定性进行了评价,还测定了不同固化时间的剪切强度以研究其动态力学性能,从浇铸体的冲击强度方面比较其韧性。综合比较分析了聚酰胺固化剂与环氧树脂固化体系的力学性能、耐热性、电绝缘性等。结果表明:桐马聚酰胺Ⅲ型固化剂具有黏度低、粘接强度大、耐热性好、力学性能优等优点。     

降冰片烯酰亚胺型双苯并嗪的合成及性能

首先用降冰片烯二酸酐、对氨基苯酚为原料合成降冰片烯酰亚胺（NI）,然后用合成的NI、4,4-二氨基二苯醚（ODA）和多聚甲醛为原料进行Mannich反应合成出降冰片烯酰亚胺型双苯并嗪（NI-BOZ）,经高温固化后形成热固性树脂。用FTIR、¹H NMR、¹³C NMR分析了NI和NI-BOZ的化学结构,证实了所得的目标产物;用DSC对NI-BOZ的固化动力学进行研究;用DMA和TGA分析了NI-BOZ的固化物的热性能。结果表明：NI-BOZ的固化反应活化能为86.27 kJ·mol^-1,反应级数为0.91;poly（NI-BOZ）树脂空气条件下的玻璃化转变温度为215℃,氮气条件下失重5%的温度为445℃,失重10%的温度为467℃,在800℃的残碳率为63%。     

Properties and curing behavior of reactive blended allyl novolak with bismaleimide using dicumyl peroxide as a novel curing agent

For reducing the cure temperature and improving the thermal stability and mechanical properties, a thermosetting resin system composed of novolak and bismaleimide (BMI) was developed by reactive blending and using dicumyl peroxide (DCP) as a novel curing agent. Novolak was allylated and reacted with BMI to produce bismaleimide allylated novolak (BAN), and the effect of DCP on flexural, impact and heat distortion temperature of cured resin were investigated. On the basis of improved mechanical and thermal properties at 0.5% DCP contents, the curing behavior of DCP/BAN resin system was evaluated by DSC analysis. Ene, Diels‐Alder, homo‐polymerization and alternating copolymerization which occurred in DCP/BAN resin system were further verified using FTIR at sequential cure conditions from 140 to 200°C. Kissinger and Ozawa‐Flynn‐wall methods were used to optimize the process and curing reactions of DCP/BAN resin system. The results showed that the addition of 0.5% DCP in BAN reduced the curing temperature and time of the modified resin. For evaluating process ability of the modified system, composite samples using polyvinyl acetyl fiber were molded and tested for flexural properties. The resulting samples showed better flexural properties when compared with the composite made with neat BAN. The modified 0.5% DCP/BAN resin system with good mechanical properties and manufacturability can be used for making bulk molding compounds and fiber reinforced composites required in various commercial and aerospace applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41829.     

Synthesis and Structure Characterization of Boron-Nitrogen Containing Phenol Formaldehyde Resin

ABSTRACT

A boron-nitrogen modified phenol formaldehyde resin (BNPFR) was prepared from phenol, formalin, ammonia water, n-butyl alcohol, boric acid, and paraformaldehyde. The reaction mechanism and structure of BNPFR during the synthesis and curing process were investigated by FTIR, NMR. The thermal stability was determined by thermogravimetric analysis. The results showed that borate, ether linkage, methylene bridges, and hexatomic ring containing coordinate linkage of boron-nitrogen were formed mostly in the synthesis and thermosetting process. The carbonyl group was formed in the synthesis and curing process at higher temperature. The initial thermal degradation temperature of BNPFR is 100°C higher than common phenol formaldehyde resin (PFR).     

Wood-induced catalytic activation of PF adhesives autopolymerization vs. PF/wood covalent bonding

The reaction of polycondensation of phenol-formaldehyde (PF) resins in the presence of wood was confirmed to have a lower energy of activation than of the PF resin alone. Under the low temperature and short curing times characteristic of the application of PF resins as thermosetting wood adhesives DSC, TGA, chemical kinetics, and IR of PF resins and relevant model compounds were carried out. These indicated that two effects appear to be present when a PF resin cures on a wood surface, both induced by the polymeric constituents of the substrate, namely carbohydrates and lignin. These appear to be (1) the catalytic activation of the resin self-condensation induced particularly by carbohydrates such as crystalline and amorphous cellulose and hemicelluloses and (2) the formation of resin/substrate covalent bonding, particularly in the case of lignin. The first appears to be, by far, the major cause of the lowering of the activation energy of PF resins curing. The contribution of the second has been found to be very small and often negligble under the conditions pertaining to thermosetting wood adhesives applications. Molecular mechanics results appear to indicate that the marked catalytic activation of PF resins autocondensation and curing appears to be induced by the strong set of PF adhesive/substrate secondary forces interactions which appear to weaken bonds which, by cleavage, lead to PF resins autocondensation. © 1994 John Wiley & Sons, Inc.     

聚醚砜/环氧树脂共混体系流变特性与固化性能的研究

环氧树脂是一种性能优良的热固性树脂,但是存在抗冲击性能差的缺点。聚醚砜(PES)是一种高性能热塑性树脂,与环氧树脂共混能够改善环氧树脂的韧性。系统研究了不同PES含量的PES/环氧树脂共混体系的流变特性和固化性能。通过对等温粘度曲线的数据拟合分析,建立了粘度模型,分析了PES对PES/环氧树脂共混体系粘度的影响机理,并通过DSC测试研究了PES对共混体系固化性能的影响。结果表明,PES在环氧树脂中的溶解过程可以引起共混体系粘度的波动,PES的引入缩短了PES/环氧树脂共混体系的凝胶时间,而且PES中的羟基对环氧树脂的固化具有促进作用。     

A new epoxy/episulfide resin system for electronic applications — 2: pot life and prepreg storage life evaluation

A new epoxy/episulfide thermosetting resin was evaluated, using a dicyandiamide (DICY) curing agent. The system was found to exhibit a longer pot life and prepreg storage life than the standard epoxy system. The properties are attributable to the change in reaction mechanism caused by the addition of episulfide. The reaction mechanisms were studied using a mono-functional model compound system; the extent of episulfide-amine reaction is relatively high in the epoxy/episulfide system relative to epoxy-amine. A tert-amine salt is probably formed which does not act as a catalyst for the epoxy ring opening, resulting in a greater pot life.     

Dielectric modeling of the curing process

Dielectric data from an epoxy resin system were used as the foundation for dielectric modeling of the curing process. This resin system (DGEBA-polyamide) was chosen as an easily processible model system. Dielectric average relaxation times, defined as the reciprocal of the angular frequency at which the loss component of the dielectric constant reaches a maximum, were determined for a 40°C isothermal cure. The changes in the average relaxation time through the cure exhibited similar behavior to those for viscosity, which inspired the correlation of the two properties. The dielectric relaxation time was modeled using a six-parameter model analogous to that used for viscosity. The model parameters were in turn associated with both intrinsic properties of the system and reaction kinetics describing the cure. The possibility of extending the relaxation time model for use with single-frequency data by means of a time-frequency correlation was also investigated. Combined, these two modeling methodologies provide a powerful constitutive approach for describing dielectric properties of thermosetting polymers during cure.     

A variable reaction order model for prediction of curing kinetics of thermosetting polymers

Based on the study of the curing reaction of an fluorinated aliphatic cyanate ester resin using an isothermal Differential Scanning Calorimetric (DSC) method, a new kinetics model with variable reaction order was proposed to describe the curing of thermosetting resins in both the chemical controlled and diffusion controlled regions. α-T_g relationship was used to calculate the diffusion controlled reaction rate constant during cure. Then the chemical and diffusion rate constants were combined in the Simon-Gillham equation to model the overall rate constant for the entire reaction. By using the overall rate constant combined with the variable reaction order, a simple model can be built up for prediction of curing kinetics of thermosetting polymer in both the chemical and the diffusion controlled regions. The new model is simple, easy to use and has very good agreement with the experimental results.     

几种胺类固化剂对环氧树脂固化行为及固化物性能的影响

固化剂结构对环氧树脂的固化行为和固化物性能具有重要影响,本文研究了聚醚胺(D-230)、异佛尔酮二胺(IPDA)和3,3'-二甲基-4,4'-二氨基-二环己基甲烷(DMDC) 3种胺类固化剂与实验室自制的低翻度环氧树脂A进行固化反应.通过薪度分析、红外(FTIR)光谱分析、DSC分析等手段研究了环氧树脂与固化剂反应程度...     

The kinetics of B‐a and P‐a type copolybenzoxazine via the ring opening process

The structure of benzoxazines is similar to that of phenolic resin through thermal self‐curing of the heterocyclic ring opening reaction that neither requires catalyst nor releases any condensation byproduct. These polybenzoxazine resins have several outstanding properties such as high thermal stability and high glass transition temperature. To better understand the curing kinetics of this copolybenzoxazine thermosetting resin, dynamic and isothermal differential scanning calorimetry measurements were performed. Three models, the Kissinger method, the Flynn–Wall–Osawa method, and the Kamal method, were used to describe the curing process. Dynamic kinetic activation energies based on Kissinger and Flynn–Wall–Osawa methods are 72.11 and 84.06 KJ/mol, respectively. The Kamal method based on an autocatalytic model results in a total order of reaction between 2.66 and 3.03, depending on curing temperature. Its activation energy and Arrhenius preexponential are 50.3 KJ/mol and 7959, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 730–737, 2005     

变温红外光谱法研究聚氨酯固化

提出利用红外光谱仪可控温附件研究丙烯酸聚氨酯树脂的固化过程。将热固性丙烯酸树脂(BS-965)作为A组分,异氰酸酯固化剂(740D)作为B组分,以一定质量比(如:A∶B=3∶1)的聚氨酯样品为例,当固化温度为120℃时,每隔5 min进行1次红外光谱扫描,通过测定官能团—NCO的特征峰2 272 cm-1透射率的变化,根据公式直接计算并得到反映热固性树脂固化程度的转化率曲线。该方法在一定温度下,只需1次制样,且不需要参比峰,使对聚氨酯固化的研究更方便、有效。     

热固性聚酰亚胺的研究进展及其在印制电路板上的应用

热固性聚酰亚胺作为一类先进的基体树脂,在航空航天、印制电路板、高温绝缘材料等领域的应用不断扩大.相对于热塑性聚酰亚胺来说,热固性聚酰亚胺具有更好的可加工性能.而且,其加工窗口温度可通过变换不同反应性端基来实现.若选用合适的反应性端基,其在固化时无小分子挥发物放出.对热固性聚酰亚胺的研究现状分类作了综述,对降冰片烯、烯丙基降冰片烯、乙炔基、苯乙炔基、马来酰亚胺、苯基马来酰亚胺、苯并环丁烯等封端型热固性聚酰亚胺的研究进展进行了重点阐述,对它们结构与性能的关系、齐聚物的固化机理等进行了讨论,并对其在印制电路板上的应用和发展趋势作了概述和展望.     

环氧树脂固化技术及其固化剂研究进展

综述了近年来国内外关于环氧树脂的热固化、微波固化及光固化技术的研究情况。在热固化技术领域 ,着重介绍了具有高耐热性、阻燃性、韧性等性能的几种功能性固化剂以及几种新型改性胺类固化剂 ;通过与热固化的对比 ,对环氧树脂的微波固化体系进行了初步的分析与探讨 ;在光固化技术领域则主要概述了环氧树脂的阳离子紫外光固化体系与自由基 -阴离子混杂光固化体系的进展情况     

Morphology and thermomechanical properties of nanostructured thermosetting blends of epoxy resin and poly(?-caprolactone)-block-polydimethylsiloxane-block-poly(?-caprolactone) triblock copolymer

Poly(?-caprolactone)-block-polydimethylsiloxane-block-poly(?-caprolactone) triblock copolymer (PCL-b-PDMS-b-PCL) was synthesized via the ring-opening polymerization of ?-caprolactone with dihydroxypropyl-terminated PDMS (HTPDMS) as the initiator. The triblock block copolymer was characterized by means of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The triblock copolymer was incorporated to prepare nanostructured thermosetting blends. The morphology of the epoxy thermosets containing PCL-b-PDMS-b-PCL were investigated by means of atomic force microscopy (AFM), transmission electronic microscopy (TEM) and small-angle X-ray scattering (SAXS). The thermomechanical properties of the nanostructured blends were investigated by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The formation of the nanostructures in the thermosetting composites was judged to follow the self-assembly mechanism in terms of the difference in miscibility of PDMS and PCL subchains with epoxy resin after and before curing reaction.     

酚醛树脂/碳化硼/聚硼氮烷复合物的固化行为及其热解性能

酚醛树脂作为一种热固性树脂基体具有广泛的应用。为了满足其作为高性能树脂基体在苛刻条件（耐高温和抗氧化）下的使用,进一步提高酚醛树脂的耐热性能并兼顾其工艺性能显得尤为重要。采用含有无机元素的耐热性聚合物（聚硼氮烷）和碳化硼纳米粒子协同改性酚醛树脂的方法,能够克服单独加入碳化硼导致的酚醛树脂固化温度升高的问题。固化动力学分析表明,加入聚硼氮烷的酚醛树脂改性体系,其固化转化率显著高于同温度下酚醛树脂或碳化硼改性酚醛树脂的转化率。同时,聚硼氮烷和碳化硼协同改性酚醛树脂固化物在高温阶段（800～1000℃）的热解稳定性较改性前有大幅度的提高。通过红外光谱分析了不同热解程度下酚醛树脂及其改性物的结构,进一步阐述了聚硼氮烷和碳化硼协同作用对酚醛树脂改性体系固化行为和热解过程的影响机制。上述采用耐热性活性聚合物和碳化硼陶瓷粒子协同改性热固性树脂的方法,有望在高性能复合材料树脂基体中得到运用。