【作者】 胡建华；

【导师】 童真；

【作者基本信息】 华南理工大学 ， 材料学， 2015， 博士

【摘要】 国内外关于无卤阻燃环氧的研究,主要集中在阻燃环氧树脂、阻燃固化剂和纳米阻燃剂的合成,以及研究这些阻燃固化物阻燃性能(极限氧指数、垂直燃烧性能、热释放速率和总量等)和热分解过程(热分解温度、残炭率和裂解产物质谱分析等),以揭示可能的阻燃机理。没有或很少对阻燃环氧固化过程动力学进行跟踪和描述,而阻燃环氧树脂的固化物的性能依赖于其固化状态。因而要得到高性能的阻燃环氧树脂,理解并应用固化动力学就很有必要。DSC通过热焓的变化来研究固化动力学,测试方便,能得到固化行为规律并且能定量描述转化率速率,流变则能反应固化环氧的结构变化。因此,本研究围绕含DOPO的阻燃环氧,通过等温和升温固化探讨转化率与固化度同温度之间的关系,揭示固化过程热焓和结构的变化。研究不同固化促进剂对固化动力学的影响。同时对玻璃化和凝胶化对体系固化的影响也有陈述。以期对实际生产过程中工艺和性能提供指导。1、以4,4-二氯甲基联苯和对氨基苯酚为原料,通过一锅法合成了氨基封端的含有联苯结构的固化剂(BPDP),采用FT-IR,1-NMR, ESI-MS和元素分析对其结构进行了表征。与常规固化剂4.4-二氨基二苯甲烷(DDM)搭配共固化环氧树脂。EP828/BPDP/DDM固化物同EP828/DDM固化物相比,热稳定性、残炭率和耐水性能有所提高。EP828/BPDP/DDM固化物的玻璃化温度随BPDP含量增加而提高。含磷1wt%的环氧DOPOER/BPDP/DDM固化物阻燃性能达到UL94V-0级,BPDP的加入提高了阻燃性能。通过用Malek法对不同含量BPDP体系进行了非等温固化动力学的分析,发现反应均具有自催化的特征,符合S B(m, n)模型。2、从工业界使用的含磷(DOPO)环氧树脂与普通EPIKOTE 828环氧材料复配,优选阻燃效果能达到LrL-94 V-0级的配方EP-1.5为：EPIKOTE 828:磷含量为3.2wt%环氧树脂：双腈胺(DICY)：有机脲U-52=10：11：1：0.6(重量比)。该配方得到的环氧树脂固化物冲击强度为14.5 kJ/m2,拉伸强度为48MPa。Kissinger法得表观活化能Ea为72.96kJ/mol。根据Malek方法发现体系非等温固化过程具有自催化的特征,固化反应行为可用简化SB(m, n)模型描述。等温固化曲线均只有单一放热峰出现,温度越高,反应速率越快,极限转化率越高。等温反应具有自催化机理。用Kam al模型模拟预测的固化速率同实验得到的固化速率符合情况良好。3、考察优化阻燃配方的促进剂改变后的1.5P-D-U-EMI体系的固化过程。采用量热法建立玻璃化温度与转化率之间的关系。在固化温度低于完全固化后的玻璃化温度T∞时,等温固化后期,观察到扩散控制现象。引入扩散控制因子对Kamal模型对计算结果进行修正。采取持续频率扫描方法对1.5P-D-U-EMI体系进行等温流变测试,等温流变过程中观察到玻璃化现象,玻璃化后,模量还是继续增加。不同的等温条件下,G值最后都达同一平台值,说明虽然不同的等温条件固化需要的时间不同,但最终都能达到同样固化度。通过对不同等温条件下的液固转变点的转化率推算和活化能计算,发现液固转变点转化率一样,推算的活化能为83.28kJ/mol,与前面Kissinger方法求得体系的Ea为85.46 kJ/mol非常接近。说明对于15P-D-U-EMI体系,DSC方法和流变测试方法,在同等条件下的固化本质是一致的。4、讨论了含量为lphr咪唑改性的氧化石墨烯对1.5P-D-U-EMI体系固化的影响。量热学角度表明,当GO-IPDI-MZ用量为lphr不会改变1.5P-D-U-EMI体系的非等温固化反应机理。1.5P-D-GOM-1体系固化起始温度Tonset、峰顶温度Tp均比15P-D-U-EMI体系降低,而总的固化热△H比15P-D-U-EMI体系的△H升高。说明GO-IPDI-MZ用量为lphr时,对我们研究的环氧体系能起到一定的促进固化和共固化作用。在固化反应后期阶段体系出现了玻璃化现象,在此阶段含扩散控制因子的Kamal模型预测结果与实验结果能较好地一致。利用多频率扫描模式,1.5P-D-GOM-1体系的非等温和等温固化过程中均可以观察到Winter凝胶化点的存在。通过流变测得的凝胶化点时间求得的活化能为79.42kJ/mol,比1.5P-D-U-EMI体系用流变方法求得的活化能83.28kJ/mol小,同样说明GO-IPDI-MZ的加入对体系固化有促进作用。5、研究2-乙基-4-甲基咪唑改性的氧化石墨烯(GO-IPDI-EMI)对于阻燃环氧树脂-双氰胺的催化作用。非等温热流图谱起始温度Tonset值和峰顶温度Tp值随GO-IPDI-EMI含量的增加移向低温。Friedman法说明GO-IPDI-EMI从反应一开始就降低反应活化能,起到了良好的催化作用。利用Kamal模型得到等温固化速率常数k1和k2求得非催化活化能Eal和自催化活化能Ea2较未加GO-IPDI-EMI的环氧体系显著下降。Winter法凝胶化的时间点随GO-IPDI-EMI含量的增加而向低温方向移动,通过等温凝胶化的时间点求得的活化能随GO-IPDI-EMI含量的增加而减小。量热法和流变均表明GO-IPDI-EMI对阻燃环氧固化起到了较好催化作用,能作为环氧树脂固化促进剂使用。更多还原

【Abstract】 An interest in halogen-free flame retardant epoxies has been around for recent years both at home and abroad. The flame retardant epoxy resins, the flame retardant curing agents and the nano-flame retardants are the focus, also the flame retardant curing performance (limiting oxygen index, vertical combustion performance, heat release rate and total amount etc.) and the thermal decomposition process (thermal decomposition temperature, residue rate and mass spectrum analysis of decomposition productions) are cared about in order to reveal the possible mechanism of flame resistance. It is seldom that the kinetics of the flame retardant epoxy curing process be described. And the performances of the flame retardant epoxy resins depends on their cure conditions. So it is necessary to understand and apply the curing kinetics to get high-performance flame retardant epoxy resins.Curing kinetics is studied by the change of enthalpy through DSC. It is convenient to describe cure behaviors and can calculate the conversion rate quantitatively. The response of the change of epoxy structure could be tracked by rheology.Therefore, the kinetics of the flame retardant epoxies containing DOPO was studied. The relations between the cure degree and the temperatures were obtained through the heat enthalpy of the cure process and the change of the structure. The effects of different cure catalyst on curing kinetics were studied. Also the influence of vitrification and gelation to the cure system have been stated. Our work provide guidance for the technology and the production performance.1、In order to increase thermal stability and decrease water uptake of conventional epoxy resins, the biphenyl structure was introduced through the curing agent. A novel biphenyl-containing amine (BPDP) was synthesized by one-pot method and used as the curing agent for bisphenol-A epoxy resin EP828. Thermal property, water uptake and curing kinetics of the co-cured epoxy with diaminodiphenyl methane (DDM) were studied. The introduction of BPDP obviously improved the thermal stability, char yield, and water-uptake of the cured epoxy resins. The glass transition temperature Tg and weight-loss temperature increased with increasing BPDP content in the co-curing agent of BPDP and DDM. BPDP showed lower reactivity towards epoxy DGEB A than DDM with higher apparent activation energy Ea. Curing reaction of the epoxy resins co-cured with BPDP and DDM was investigated by non-isothermal DSC and the curing kinetics was described by a truncated two-parameter autocatalytic equation of the Sestak-Berggren model with experimentally determined parameters, which fitted the observed non-isothermal curing reaction rate quantitatively. The cured samples of DOPOER BPDP/DDM with 1wt% phosphorous content achieved UL-94 V-0 grade, so the flame retardant performance was improved by BPDP.2、A halogen-free flame retardant epoxy resin was prepared consisting of DOPO-based glycidyl ether of cresol formaldehyde novolac and diglycidyl ether of bisphenol A cured by micronized dicyandiamide with accelerator U-52. The optimized epoxy resin formula contained 1.5 wt% of phosphorus and achieved UL-94 V-0 grade and LOI of 32%, with high tensile strength and impact strength of 48 MPa and 14.5 kJ/m2, respectively. Curing reaction kinetics for the DOPO-containing epoxy with 1.5 wt% of P was investigated by DSC through both non-isothermal and isothermal scanning. A two-parameter autocatalytic equation of the Sestak-Berggren model was constructed with experimentally determined kinetics parameters, which described the non-isothermal curing reaction rate quantitatively. For the isothermal curing kinetics, the Kamal-Sourour model was adopted to express the autocatalytic effect. The parameters of the reaction rate constant and reaction order were evaluated by curve fitting, and the calculated curve described the observed reaction rate fairly well. The determined kinetics parameters reflected the characteristics of the autocatalytic reaction for the curing of the phosphorus-containing epoxy system.3、The 1.5P-D-U-EMI system was changed from the optimum flame retardant epoxy formula by using different catalyst. The curing process of the 1.5P-D-U-EMI system was compared. The relationship between the glass transition temperature and conversion was established by DSC. The phenomenon of diffusion control was observed at the later stage at the isothermal conditions below the completely cured glass transition temperature Tg∞. The Kamal-Sourour model with diffusion was adopted to calculated curve described the observed reaction rate fairly well. The isothermal rheological test was under continuous frequency sweep. Vitrification phenomenon was observed in the process of isothermal rheological test. The modulus of the epoxy system increased continuously after vitrification. The G’ value of the epoxy system finally reach the same platform finally because the epoxy system achieves the same cure degree in the end although the isothermal conditions or the cure time are different. The conversion of the liquid-solid transition point at different isothermal conditions is the same. And the activation energy by rheology is 83.28kJ/mol, which is very close to the activation energy 85.46 kJ/mol by Kissinger method. It is demonstrated that the cure essence is the same under the same condition by DSC and the rheological test.4、The isothermal cure mechanism of 1.5P-D-U-EMI was not changed by adding lphr GO-IPDI-MZ. Tonset and Tp of 1.5P-D-GOM-1 are reduced compared to that of 1.5P-D-U-EMI, but the total heat ΔH of 1.5P-D-GOM-1 was higher than that of 1.5P-D-U-EMI. So lphr GO-IPDI-MZ plays a catalytic and co-curing action on the epoxy system. The phenomenon of diffusion control was observed at the later stage at the isothermal conditions. The Kamal-Sourour model with diffusion was adopted to calculated curve described the observed reaction rate fairly well. The isothermal rheological test was under multiple frequency sweep. The Winter gel point can be observed in both rheological non-isothermal or rheological isothermal tests. And the activation energy by rheology is 79.42kJ/mol, which is lower than the activation energy 83.28 kJ/mol of 1.5P-D-U-EMI. Also the results of the rheological tests show that the GO-IPDI-MZ plays a catalytic action on the epoxy system.5、The catalyst action of GO-IPDI-EMI for the cure reaction of the epoxy-dicyandiamide system. Tonset and Tp of the system move to lower temperatures with the increase of the GO-IPDI-EMI content. The Friedman method showed that a catalytic action occured at the begin since the activation energy decreased. The curing rate constant k1 and k2 determined by Kamal model became lower and the activation energy was reduced when GO-IPDI-EMI was added. The Winter gel points moved to lower temperatures in rheological non-isothermal tests with the content of GO-IPDI-EMI increased. Also the activation energy was reduced by rheological isothermal tests with the content of GO-IPDI-EMI increased. It showed that GO-IPDI-EMI catalyze the flame retardant epoxy systems by calorimetry and rheological tests. In other words, GO-IPDI-EMI can be used as a catalyst for epoxy resins.更多还原