成分比例不同的MEKP固化不饱和聚酯树脂研究

通过45,50,55和60℃等温DSC固化研究了成分(过氧化氢、MEKP单体和二聚体)比例不同的过氧化甲乙酮(MEKP)对不饱和聚酯树脂(UP)固化诱导期、峰值时间和固化率的影响,并讨论了固化引发机理。结果发现,过氧化氢质量分数较少、单体和二聚体质量比为1.5∶1的MEKP对UP固化有利。     

RTM用乙烯基酯树脂的固化反应研究

本文通过动态ＤＳＣ实验获得相应曲线，利用Ｋｉｓｓｉｎｇｅｒ法对实验曲线进行数学处理，求得树脂固化过程的活化能和反应级数，从而建立了ＭＦＥ－２乙烯基酯树脂的的固动力学方程，从而为对树脂的固化过程进行监控和提高树脂的固化质量提供理论依据。     

乙烯基树脂后固化制度的优化研究

采用DSC法研究了乙烯基树脂体系的固化动力学参数,并通过对该体系树脂浇铸体的固化度、力学性能、玻璃化转变温度的测试确定了最佳后固化制度。结果表明,该体系固化反应的表观活化能为56.27 kJ/mol,频率因子为4.96×107/s,反应级数为0.9;最佳后固化制度为100℃/1 h,此时固化度可达94.7%,弯曲强度可达102.6 MPa,拉伸强度可达64.1 MPa,玻璃化转变温度可达107.8℃。     

含乙烯基有机硅树脂的电子束固化行为研究

以八甲基环四硅氧烷、四甲基四乙烯基环四硅氧烷为单体,六甲基二硅氧烷为封端剂,碱胶为催化剂,合成了含乙烯基有机硅树脂;并研究了电子束辐射剂量对其固化行为的影响和固化涂层的热性能。红外谱图及凝胶率测试结果表明,有机硅树脂中的碳碳双键吸收峰强度随辐射剂量的增加而减弱,辐射诱导交联网络结构的形成导致固化涂层的凝胶率随剂量的增加而显著增加;辐射剂量为30 kGy时,凝胶率为46.2%;辐射剂量增加至60 kGy时为70.1%和100 kGy时为85.9%。差示扫描量热分析和热质分析结果表明,固化涂层具有优良的耐低温性和热稳定性。     

固化放热温度和时间对酚醛型乙烯基酯树脂最终玻璃化转变温度的影响

考察了不同固化环境对酚醛型乙烯基酯树脂的性能影响,设计了两种极端固化工艺:一种在良导热材料不锈钢模具中固化;一种在不良导热塑料烧杯中固化,并测试了两种不同固化工艺下固化物的玻璃化转变温度、固化度、苯乙烯和低聚物双键剩余率,并通过延长常温固化时间和不同高温后处理时间进一步研究了上述性能参数的变化情况,得到结论,在良导热材料不锈钢模具中固化的样条的起初玻璃化转变温度低于烧杯中固化样条,并且通过延长常温固化时间或者高温后处理时间,较难达到烧杯固化样条的玻璃化转变温度和固化度。     

乙烯基树脂及其碳纤维复合材料的电子束辅助固化研究

本文详细讨论了乙烯基树脂进行电子束固化的机理,成功地实现了乙烯基树脂为基体的碳纤维复合材料的电子束辐射固化,并比较电子束辅助固化该树脂复合材料的力学性能与相应热固化复合材料的力学性能。     

低收缩乙烯基酯树脂的研究

本文选用聚氨酯、聚醋酸乙烯酯、丁腈橡胶等聚合物作为低收缩添加剂,研究了它们在降低乙烯基酯树酯固化收缩率方面的作用。探讨了树脂固化收缩率与添加剂种类、含量、分子量及成型温度等因素之间的关系,用DDV、SEM等现代分析手段对改性体系的亚微观结构进行了表征。在实验的基础上,找到了效果较为满意的改性配方。     

可见光固化树脂的研究

本文介绍了一种新型的可见光固化(VLC)树脂,通过与一般过氧化物固化的乙烯基酯树脂的机械性能和耐腐蚀性能比较可以看出,两者性能相当。但使用可见光,而非对人体有害的紫外光,安全环保,应用广泛;快速固化,苯乙烯挥发极少,操作简便,无需繁琐的添加促进剂及固化剂和脱泡过程。提高生产效率的同时,大幅度降低施工成本。     

过氧化甲乙酮的组成结构对树脂固化反应的影响

过氧化甲乙酮是不饱和聚酯和乙烯基酯树脂的主要引发剂，它由几种不同结构的有机过氧化物组成，其中两种结构的有机过氧化物对聚酯树脂和乙烯基酯树脂的凝胶和固化起决定作用，过氧化氢的存在将影响这种作用。     

乙烯基酯树脂体系固化反应动力学研究

本文采用非等温DSC法对树脂体系的固化过程进行了研究。利用Kissinger和Crane法计算得到固化反应的表观活化能Ea、指前因子A、固化反应级数N等动力学参数,建立了固化反应动力学方程,并用T-β外推法确定了固化工艺温度,同时对体系的玻璃化转变温度进行了测定。     

Effect of oxirane groups on curing behavior and thermal stability of vinyl ester resins

The effects of oxirane groups in vinyl ester (VE) resin and reactive diluent on curing characteristics and thermal behavior of cured resins are described. Stoichiometric (0.5:1, sample A) as well as nonstoichiometric (0.5:0.85, sample B) ratios of the diglycidyl ether of bisphenol-A (DGEBA) and methacrylic acid (MA) were used for the synthesis of VE resins. Resin sample B had more residual epoxy groups because of the stoichiometric imbalance of the reactants. VE resins thus obtained were diluted with methyl methacrylate (MMA; 1:1, w/w), and controlled quantities of epoxy groups were introduced by partial replacement of MMA with glycidyl methacrylate (GMA), keeping the overall ratio of resin and reactive diluent constant. Increase of GMA content in resin A or B resulted in a decrease in gel time, indicating that the curing reaction is facilitated by the presence of epoxy groups. An increase in initiator content also reduced the gel time. In the differential scanning calorimetry (DSC) scans, a sharp curing exotherm was observed in the temperature range 107 ± 3–150 ± 1 °C. The onset temperature (T_onset) and peak exotherm temperature (T_exo) decreased with increase in GMA content. Heat of curing (ΔH) also increased with increase in GMA content. A broad exotherm was observed after the initial sharp exotherm that was attributed to the etherification reaction. Cured VE resins were stable up to 250–260 °C, and started losing weight above this temperature. Rapid decomposition was observed in the temperature range 400–500 °C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 416–423, 2001     

Morphology of rubber‐modified vinyl ester resins cured at different temperatures

The morphologies of styrene (St) crosslinked divinylester resins (DVER) modified with elastomers were analyzed. The primary focus of this study was on the effect of the molecular weight of the resins, the reactivity of the elastomeric modifiers, and the temperature of curing. All of these variables have a strong influence on both the miscibility and the viscosity of the system, affecting the phase‐separation process that takes place in the unreacted and the reacting mixture. The selected liquid rubbers were carboxyl‐terminated poly(butadiene‐co‐acrylonitrile) (CTBN), a common toughening agent for epoxy resins, and an almost unreactive rubber with the DVER; and St comonomers and vinyl‐terminated poly(butadiene‐co‐acrylonitrile (VTBN), a reactive rubber. Different morphologies potentially appear in these systems: structures formed by DVER–St nodules surrounded by elastomer and spanning the whole sample; dual cocontinuous micron‐size domains formed by elastomer‐rich or resin‐rich domains; and a continuous DVER–St‐rich phase with included complex nodular domains. These microstructures can be varied by just changing the nature and concentration of the elastomer, the molecular weight of the resin, or the curing temperature. The appearance of these morphologies is discussed as a function of the above variables. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 274–283, 2003     

Curing kinetics and thermal properties of vinyl ester resins

The curing kinetics of dimethacrylate-based vinyl ester resins were studied by scanning and isothermal DSC, gel time studies, and by DMTA. The rate of polymerization was raised by increased methyl ethyl ketone peroxide (MEKP) concentration but the cocatalyst, cobalt octoate, retarded the reaction rate, except at very low concentrations. By contrast, the gel time was reduced for all increases in either peroxide or cobalt concentration. This contradictory behavior was explained by a kinetic scheme in which the cobalt species play a dual role of catalyzing the formation of radicals from MEKP and of destroying the primary and polymeric radicals. The scanning DSC curves exhibited multiple peaks as observed by other workers, but in the present work, these peaks were attributed to the individual influence of temperature on each of fundamental reaction steps in the free radical polymerization. Physical aging appeared to occur during the isothermal polymerization of samples cured below the “fully cured” glass transition temperature (T_g). For these undercured materials, the difference between the DSC T_g and the isothermal curing temperature was approximately 11°C. Dynamic mechanical analysis of a partially cured sample exhibited anomalous behavior caused by the reinitiation of cure of the sample during the DMTA experiment. For partially cured resins, the DSC T_g increased monotonically with the degree of cure, and this dependence was fitted to an equation related to the Couchman and DiBenedetto equations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 769–781, 1997     

MMA对乙烯基酯树脂及其复合材料性能的影响

通过粘度分析和力学性能、阻燃性能测试,研究了以甲基丙烯酸甲酯(MMA)作活性稀释剂的乙烯基酯树脂的流变性能及其对复合材料性能的影响。结果表明:常温下MMA能有效降低乙烯基酯树脂的粘度,20~40℃下,添加量>30%时,树脂体系的粘度在450 mPa.s以内,可应用于RTM工艺;固化后该复合材料的拉伸、弯曲强度、抗冲击性能、层间剪切强度和阻燃性能优异,可应用于高性能阻燃型复合材料构件的制备。     

Effects of processing conditions on the curing of a vinyl ester resin

The effects of temperature, initiator, and accelerator levels on the curing of an epoxy bisphenol‐A vinyl ester resin Derakane® 411‐45 (formulated with styrene) were investigated by gel‐time and exotherm‐peak measurements on bulk samples. It was observed that the gel time was reduced as the initiator or accelerator ratio increased. Except at higher contents of the accelerator, a small kinetic plateau was seen in the gel curve and a shift of the maximum exotherm toward high temperatures in the DSC curves. This was explained by the dual role played by the accelerator species. A regression analysis of all gel‐time data showed a dependence of 3/2 order in the accelerator and first order in the initiator concentrations. Thus, for this polymerization initiation system, the gel time can be predicted for any initiator and cobalt levels and at any temperature within the ranges studied. The effect of the initiator on the unreacted styrene and vinyl ester was also examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1146–1154, 2002; DOI 10.1002/app.10403     

HBP-SiO2对氰酸酯树脂固化动力学的影响

为了提高nano-SiO2在树脂基体中的分散性,采用一种超支化聚硅氧烷修饰的纳米二氧化硅(HBP-SiO2)改性氰酸酯(CE)树脂。利用非等温差示扫描量热法(DSC)研究了HBP-SiO2/CE电子封装材料的固化动力学,求得其固化工艺参数和固化动力学参数分别为:凝胶温度150.17℃,固化温度197.81℃,后处理温度258.97℃;表观活化能11.22kJ/mol,反应级数0.75,频率因子18342.84s-1。研究表明,HBP-SiO2的加入可以降低CE的活化能,使其固化反应可以在较低温度下进行。     

FT‐IR studies on the curing behavior of polycardanol from naturally renewable resources

In the present study, the curing behavior of polycardanol prepared by enzymatic oxidative polymerization of thermally treated cashew nut shell liquid, which can be available from naturally renewable resources, was explored in the presence of methyl ethyl ketone peroxide (MEKP) and cobalt naphthenate (Co‐Naph). The curing behavior was monitored varying Co‐Naph concentration and curing temperature by means of Fourier transform infrared (FT‐IR) spectroscopy. The result revealed that the characteristic absorption bands were significantly affected by the given curing condition, resulting mainly from the unsaturated moiety in the polycardanol molecule. The extent of curing of polycardanol strongly depended on curing temperature, showing a typically sigmoidal curve reaching almost 1.0 upon processing at 200°C for 120 min. The thermal curing conditions for preparing polycardanol with an optimal state of cure were provided in the work. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical characterization and chemical resistances of cured unsaturated polyester resins modified with vinyl ester resins based on recycled poly(ethylene terephthalate)

Unsaturated polyester resin (UP) was prepared from glycolyzed oligomer of poly(ethylene terephthalate) (PET) waste based on diethylene glycol (DEG). New diacrylate and dimethacrylate vinyl ester resins prepared from glycolysis of PET with tetraethylene glycol were blended with UP to study the mechanical characteristics of the cured UP. The vinyl ester resins were used as crosslinking agents for unsaturated polyester resin diluted with styrene, using free‐radical initiator and accelerator. The mechanical properties of the cured UP resins were evaluated. The compressive properties of the cured UP/styrene resins in the presence of different vinyl ester concentrations were evaluated. Increasing the vinyl ester content led to a pronounced improvement in the compression strength. The chemical resistances of the cured resins were evaluated through hot water, solvents, acid, and alkali resistance measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3175–3182, 2007     

Mechanical behavior and structure of rubber modified vinyl ester resins

Vinyl esters are used widely as thermoset matrix materials for reinforced composites; however, they suffer from low‐impact resistance. Substantial enhancement of the toughness of brittle polymers may be achieved by dispersing elastomeric inclusions or rubber particles in the polymer matrix, inducing multiple crazing and shear yielding of the matrix. The main objectives of this work are morphological characterization of vinyl ester/reactive rubber systems and investigation of the mechanical and fracture behavior of these systems. Additional studies focused on rubber endcapped vinyl ester in the absence and presence of added reactive rubber. The initial compatibility of the liquid rubber with the liquid resin was studied. This is a key factor, along with cure conditions, in determination of the possible morphologies, namely, the degree of phase separation and particle size. The initial rubber/resin compatibility was found poor and all attempts to improve it by means of surfactants or ultrasonic treatment have not been successful. The flexure mechanical and fracture behavior of the cured resin/rubber systems was investigated. Three basic types of crack propagation behavior, stable, unstable, and stick‐slip, were observed. Fracture toughness of various resin/rubber systems was evaluated and was found to increase with increased content of rubbery second‐phase material. However, there is some payoff in stiffness and flexural strength of the cured resins. The addition of rubber does not affect the resin toughness at impact conditions. Analysis and interpretation of fractures morphology show that both multiple crazing and external cavitation play an important role in the fracture mechanism of the rubber modified specimens. No shear yielding is evident. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 647–657, 1999