Curing behavior of epoxy resin having hydroxymethyl group

A new type of epoxy resin having hydroxymethyl group was synthesized. This epoxy resin was mixed with commercial epoxy resin in various ratios. The mixed epoxy resins were cured with a mixture of 4,4′-diaminodiphenylmethane and m-phenylenediamine (molar ratio, 6 : 4) as a hardener. Curing behavior of the epoxy resin systems with the hardener was examined by DSC and TG-DSC, and parameters of cure reaction were obtained. Viscoelastic properties of cured resin were studied by dynamic mechanical analyzer. It was found that the higher the amount of epoxy resin having hydroxymethyl group, the lower the activation energy (Ea) and the higher the rate constant (k) were. It was also found that the higher the amount of the epoxy resin having hydroxymethyl group, the better heat resistance the fully-cured resin had. These results were explained as follows: Hydroxymethyl group accelerated an epoxideamine reaction. The crosslinking density of the cured resin was increased because in the hydroxymethyl group occurred a condensation reaction above 200°C.     

Synthesis and properties of urethane elastomer-modified epoxy resin having hydroxymethyl group

Synthesis and properties of urethane elastomer-modified epoxy resins were studied. The urethane elastomer-modified epoxy resins were synthesized by the reaction of a 4-cresol type epoxy compound having hydroxymethyl groups (EPCDA) with isocyanate prepolymer. The structure was identified by IR, ¹H NMR and GPC. These epoxy resins (EPCDATDI) were mixed with a commercial epoxy resin (DGEBA) in various ratios. The mixed epoxy resins were cured with a mixture of 4,4′-diaminodiphenylmethane and 3-phenylenediamine (molar ratio 6:4) as a hardener. The curing behaviour of these epoxy resins was studied by DSC. The higher the concentration of EPCDATDI, the higher the onset temperature and the smaller the rate constant (k) of the exothermic cure reaction were. It was considered that the ratio of hydroxymethyl group to epoxide group was very small and the molecular weight of EPCDATDI was large. Therefore, the accelerating effect of the hydroxymethyl group on the epoxide–amine reaction was cancelled by the retardant effect of increased molecular weight and viscosity, and decreased molecular motion. Toughness was estimated by Izod impact strength and fracture toughness (K_1C). On addition of 10 wt% EPCDATDI with low molecular weight (M?_n 6710, estimated by GPC using polystyrene standard samples), Izod impact strength and K_1C increased by 70% and 60%, respectively, compared with unmodified epoxy resin. Glass transition temperatures (T_g) for the cured epoxy resins mixed with EPCDATDI measured by dynamic mechanical spectrometry were the same as those of unmodified epoxy resin. The storage modulus (E′) at room temperature decreased with increasing concentration of EPCDATDI. Toughness and dynamic mechnical behaviour of cured epoxy resin systems were studied based on the morphology.     

Curing behavior of dicyandiamide/epoxy resin system using different accelerators

Various amounts of dicyandiamide (Dicy), two grades of epoxy resins, i.e. Epiran 06 and Epikote 828, and three different accelerators including benzyl dimethyl amine (BDMA), 3-(4-chlorophenyl)-1,1-dimethyl urea (Monuron) and 2-methyl imidazole (Im) were used in curing of Dicy/epoxy resin system. Both of the used epoxy resins were based on diglycidyl ether of bisphenol A (DGEBA). The effects of type and concentration of accelerators on curing behavior were studied by differential scanning calorimetry (DSC) method in dynamic or non-isothermal mode. The optimum concentration of Dicy for curing of epoxy resins was obtained based on the glass transition temperature of the cured epoxy/Dicy formulations. The maximum glass transition temperature of 139 °C was obtained at the stoichiometric ratio of Dicy to epoxy of 0.65. The results showed that BDMA has a broader curing peak in DSC and starts the cure reaction earlier than the others. However, Monuron has a narrow curing reaction peak with good cure latency. The tensile properties of Dicy-cured Epiran 06 and Epikote 828 epoxy resins reinforced with chopped strand mat showed that these two epoxy resins have similar mechanical properties. For composites based on the Epiran 06 and Epikote 828 reinforced with 40 wt % glass chopped strand mat, tensile strength and modulus were 156 and 153.4 MPa and 11.6 and 12.4 GPa, respectively.     

Curing behavior and thermal properties of multifunctional epoxy resin with methylhexahydrophthalic anhydride

The curing behavior and thermal properties of bisphenol A type novolac epoxy resin (bisANER) with methylhexahydrophthalic anhydride (MHHPA) at an anhydride/epoxy group ratio of 0.85 was studied with Fourier‐transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry. The results showed that the FTIR absorption intensity of anhydride and epoxide decreased during the curing reaction, and the absorption peak of ester appeared. The dynamic curing energies were determined as 48.5 and 54.1 kJ/mol with Kissinger and Flynn–Wall–Ozawa methods, respectively. DSC measurements showed that as higher is the curing temperature, higher is the glass transition. The thermal degradation of the cured bisANER/MHHPA network was identified as two steps: the breaking or detaching of ? OH, ? CH₂? , ? CH₃, OC? O and C? O? C, etc., taking place between 300 and 450°C; and the carbonizing or oxidating of aromatic rings occurring above 450°C. The kinetics of the degradation reaction was studied with Coats–Redfern method showing a first‐order process. In addition, vinyl cyclohexene dioxide (VCD) was employed as a reactive diluent for bisANER (VCD/bisANER = 1 : 2 w/w) and cured with MHHPA, and the obtained network had a higher T_g and a slight lower degradation temperature than the undiluted system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2041–2048, 2007     

含磷阻燃环氧树脂的固化动力学研究

通过差热分析(DSC)研究了环氧树脂/DDM/DOPO-HQ(2-(6H-二苯并<1,2>-5-氧杂-6-膦酰杂-6-苯基-1,4-对苯二酚)体系的非等温过程固化反应动力学,研究了不同含磷量对固化反应的影响,通过Kissinger法与Crane法计算了固化反应的活化能和反应级数,确定了环氧树脂/DDM/DOPO-HQ的固化工艺条件。结果表明,含磷单体的加入量越大,固化反应的活化能越低,由51.32降低到33.51 kJ.mol-1。确定了固化工艺应为110℃固化1 h,150℃固化4 h,180℃固化1 h。     

异氰酸酯/环氧树脂的固化机理

详细研究了异氰酸酯/环氧树脂体系的固化反应和固化机理。采用差示扫描量热法（DSC）和红外光谱法（FTIR）跟踪了异氰酸酯/环氧树脂固化反应过程,定量分析了异氰酸酯、环氧基团和新生成的异氰脲酸酯和口恶唑烷酮的变化。DSC分析结果表明,DSC曲线上出现3个放热峰,说明固化过程中存在至少3种反应;FTIR分析结果表明,在140℃以下固化体系主要发生异氰酸酯的三聚反应生成三嗪环（异氰脲酸酯）;在200℃下,异氰酸酯-NCO基团与环氧基团开环反应生成口恶唑烷酮;在230℃ 下,三嗪环（异氰脲酸酯）进一步与环氧基团开环反应生成口恶唑烷酮。研究了不同温度下环氧基团、异氰酸酯基团、异氰脲酸酯基团、口恶唑烷酮基团随反应时间的变化规律。     

Curing of epoxy resin contaminated with water

Epoxy resins used for reinforcement of bridges and buildings are explored in the light of both curing rates and mechanical properties when resins are contaminated with water in outdoor construction. The developed resin is composed of a conventional resin of bisphenol A diglycidyl ether and a hardener with a polyoxipropyldiamine base. Curing rates were obtained by time variation of the near infrared absorbance of amine groups in the hardener at various water contents. They obeyed the second‐order reaction law with respect to the hardener, of which the activation energy was 70 kJ mol⁻¹. Water increased the reaction rate. Mechanical properties such as ultimate tensile strength, adhesive shear stress, and flexural strength were measured at various water contents for the developed epoxy resin and the commercially available low‐temperature epoxy resin. The developed cured resin shows not only higher mechanical strengths but also much less deterioration by water than the conventional cured resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 214–220, 2001     

中分子质量环氧树脂合成新工艺

采用了双酚A与环氧氯丙烷醚化生成氯醇醚,再与双酚A反应并经过闭环反应合成中分子质量环氧树脂新工艺,可较大幅度提高环氧树脂的质量。     

Curing behavior and thermal property of epoxy resin with boron‐containing phenol‐formaldehyde resin

The curing reaction of bisphenol‐A epoxy resin (BPAER) with boron‐containing phenol–formaldehyde resin (BPFR) was studied by isothermal and dynamic differential scanning calorimetry (DSC). The kinetic reaction mechanism in the isothermal reaction of BPAER‐BPFR was shown to follow autocatalytic kinetics. The activation energy in the dynamic cure reaction was derived. The influence of the composition of BPAER and BPFR on the reaction was evaluated. In addition, the glass transition temperatures (T_gs) were measured for the BPAER‐BPFR samples cured partially at isothermal temperatures. With the curing conditions varying, different glass transition behaviors were observed. By monitoring the variation in these T_gs, the curing process and the thermal property of BPAER–BPFR are clearly illustrated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1054–1061, 2000     

低黏度高分子质量超支化环氧树脂的合成及性能

利用一步法合成了低黏度高分子量的第四代芳香族超支化环氧树脂HTDE-4,该种树脂能作为环氧树脂的稀释剂。将HTDE-4与双酚A型环氧树脂杂化复合,研究其固化物的机械性能。杂化树脂的性能随超支化环氧树脂含量的增加先增加后下降;当用量为12%(质量分数)左右时,体系的拉伸强度、弯曲强度、冲击强度和断裂韧性分别提高15.6%,14.8%,158.9%和36.9%,断裂韧性达到2.78 kPa.m1/2。用傅里叶变换红外光谱和核磁共振氢谱、扫描电镜和分子模拟技术对产物进行了研究。     

Property of diblock copolymer having extremely narrow molecular weight distribution

Molecular weight distribution effect on the morphological behavior of polystyrene-block-polyisoprene (PS-b-PI) diblock copolymers was investigated. PS-b-PI samples were prepared by anionic polymerization and further fractionated by HPLC to obtain the fractions of similar average molecular weight and composition but of narrower distributions in both molecular weight and composition. The strategy is to use reversed-phase LC to fractionate the PI block and normal phase LC to fractionate the PS block with a minimal effect on the other blocks. The interfacial thickness, grain size and the phase transition behavior of the unfractionated and fractionated PS-b-PI were compared by X-ray reflectivity, small angle X-ray scattering, transmission electron microscopy and rheological measurements. The fractionated PS-b-PI with more homogeneous molecular weight and composition exhibits a narrower interface, larger grain size and a sharper morphological transition compared to the unfractionated PS-b-PI.     

氢化双酚A型环氧树脂的固化性能研究

本文研究了聚醚胺（D-230）、聚醚胺（T-403）、甲基四氢苯酐（MeTHPA）3种固化剂与氢化双酚A型环氧树脂的固化反应性能,针对不同体系的反应活性和固化反应动力学凝胶时间、粘接性能和冲击断口的表面形貌进行了研究。结果表明：随着温度的升高,三种体系的凝胶时间均显著下降,其中MeTHPA体系的凝胶时间最短;T-403体系在室温下的剪切强度最大,达到30.059MPa;D-230体系的冲击韧性较高,达到51.279kJ/m2;用这3种固化剂进行固化反应的表观活化能分别为56.55、63.99、67.60kJ/mol,其反应级数分别为0.865、0.902、0.998。     

Curing of acrylated epoxy resin based on bisphenol-S

The acrylated diglycidyl ether of bisphenol-S was prepared by reacting diglycidyl ether of bisphenol-S (DGEBS) with acrylic acid using dimethyl benzylamine as a catalyst. The acrylated epoxy resin thus obtained was characterized by IR, ¹³C-NMR, and DSC. The curing reaction of the acrylated epoxy resin with dicumyl peroxide was investigated by differential scanning calorimetry at three different heating rates. The overall curing kinetics were found to be approximately second order, independent of the scan rate. The TGA was used to investigate the thermal decomposition of acrylated epoxy resin and to determine the kinetic parameters such as activation energy, preexponential factor, and reaction order. Such information can be used for quick estimation of polymer lifetimes.     

纳米粒子改性环氧树脂固化反应动力学研究

采用示差扫描量热仪(DSC)研究了不同用量纳米Al2O3粒子改性的环氧树脂基体的固化反应动力学,根据DSC实验的结果采用Kissinger和Crane方法计算得到不同树脂体系的固化动力学参数并研究了固化度与温度之间的关系。结果表明,纳米粒子的加入使固化的起始温度与终止温度降低,并缩短了固化时间。随着纳米粒子含量的增加,改性树脂体系固化反应放热峰的峰值温度逐渐降低,固化反应的表观活化能降低,但反应频率因子及反应级数基本不变。     

Curing behavior and properties of epoxy resins cured with the diamine having the quinoxaline or triazine structure

2,3-Bis(4-aminophenyl)quinoxaline (1a), 2,3-bis(4-aminophenyl)-6-methylquinoxaline (1b), and 5,6-bis(4-aminophenyl)-3-(2-pyridyl)-1,2,4-triazine (2) were studied as curing agents of epoxy resins. The exotherms on differential scanning calorimetry thermograms of the mixtures of diglycidyl ether of bisphenol A (DGEBA) with 1a, 1b, and 2 were observed at higher temperatures than that of the mixture of DGEBA with a commercially used diamine, for example, 4,4′-diaminodiphenylsulfone (DDS). However, the epoxy resin cured with 1a (EP-1a) showed higher tensile strength to stainless steel at 20°C than that cured with DDS, and the high tensile strength of EP-1a was maintained even at 180°C. The epoxy resin cured with 1b or 2 also possessed higher tensile strength at 20°C than that cured with DDS, but the high tensile strength lowered somewhat at 120°C. Using diamines 1a, 1b, and 2 as a curing agent improved heat distortion temperatures of the cured epoxy resins. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1737–1741, 1998     

Curing behavior of epoxy resin/tung oil anhydride exfoliated nanocomposite by differential scanning calorimetry

The nanocomposite of epoxy resin/tung oil anhydride/organic montmorillonite was prepared by casting and curing. The distance of the clay gallery rose and the exfoliated nanocomposite was formed. The exfoliation behaviors of the nanocomposite had been investigated by X‐ray diffraction (XRD). The curing mechanism and kinetics of epoxy resin with the different amounts of organic montmorillonite were studied using isothermal and dynamic methods by differential scanning calorimetry (DSC). Some parameters, the activation energy and reaction orders, were calculated by the modified Avrami equation in analysis of the isothermal experiment. The total curing mechanism and kinetics of curing reaction were also analyzed by the Flynn–Wall–Ozawa method. It was noted that the instantaneous activity energy during the curing process could be obtained by the Flynn–Wall–Ozawa method and the trend of the results was in agreement with those obtained from the modified Avrami equation. These results show that the activity energy decreases with the addition of organic montmorillonite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3822–3829, 2004     

Effect of the epoxy molecular weight on the properties of a cyanate ester/epoxy resin system

Bisphenol A dicyanate (BADCy) was modified by diglycidyl ether of bisphenol A epoxy resins with different molecular weights [E20 (weight‐average molecular weight = 1000) and E51 (weight‐average molecular weight = 400)] to investigate the effects of the epoxy molecular weight on the properties of the modified systems. The reactions were monitored with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy, and the results showed that more pentacyclic oxazolidinone rings were formed in BADCy/E51 than in BADCy/E20 with the same epoxy resin weight content. DSC showed that BADCy/E20 had a lower curing temperature than BADCy/E51 because of the higher concentration of hydroxyl groups (? OH) in E20. Thermal, moisture absorption, and mechanical testing showed that E51‐modified BADCy performed better because of its lower molecular weight. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1744–1750, 2006     

环氧树脂/有机脲体系的固化反应动力学

研究了环氧树脂/有机脲体系的固化行为,探讨了固化反应机理。结果表明:有机脲是一种能有效固化环氧树脂的潜伏性固化剂;固化反应机理为有机脲与环氧树脂首先反应生成噁唑酮和仲胺,在环氧树脂过量的情况下,仲胺与环氧树脂反应生成叔胺,叔胺进一步反应产生阴离子活性中心,最终引发阴离子开环聚合。反应初期固化反应速率受有机脲分解产生仲胺浓度的影响,反应中期有机脲分解完毕,阴离子活性中心浓度为常数。     

Curing of epoxy resin using imide‐amines

The curing behavior of diglycidyl ether of bisphenol‐A (DGEBA) was investigated by differential scanning calorimetry, using varying molar ratios of imide‐amines and 4,4′‐diaminodiphenyl sulfone (DDS). The imide‐amines were prepared by reacting 1 mol of pyromellitic dianhydride (P) with excess (2.5 mol) of 4,4′‐diaminodiphenyl ether (E), 4,4′‐diaminodiphenyl methane (M), or 4,4′‐diaminodiphenyl sulfone (S) and designated as PE, PM, PS. Structural characterization was done using FTIR, ¹H NMR, ¹³C NMR spectroscopic techniques and elemental analysis. The mixture of imide‐amines and DDS at ratio of 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0 were used to investigate the curing behavior of DGEBA. The multiple heating rate method (5, 10, 15, and 20°C/min) was used to study the curing kinetics of epoxy resins. The peak exotherm temperature was found to be dependent on the heating rate, structure of imide‐amine, and also on the ratio of imide‐amine : DDS used. Activation energy was highest in case of epoxy cured using a mixture of DDS : imide‐amine of a ratio of 0.75 : 0.25. Thermal stability of the isothermally cured resins was also evaluated in a nitrogen atmosphere using dynamic thermogravimetry. The char yield was highest in case of resins cured using mixture of DDS : PS (0.25 : 0.75; EPS‐3), DDS : PM (0.25 : 0.75; EPM‐3), and DDS : PE (0.75 : 0.25; EPE‐1). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3502–3510, 2006