Study of cure kinetics of epoxy/DDS/nanosized (SiO2/TiO2) system by dynamic differential scanning calorimetry

In this study the curing kinetics of epoxy based on the diglycidyl ether of bisphenol A (DGEBA), 4,4′‐diaminodiphenyl sulfone (DDS) as a hardener, and SiO₂/TiO₂ (70:30) as a nanofiller was investigated by nonisothermal differential scanning calorimetry (DSC). The effects of different weight contents of SiO₂/TiO₂ nanoparticles were studied using DSC in Dynamic Mode and the best value of the nanofiller was found to be 5 phr (parts per hundred). Dynamic measurements were used to obtain the total heat of reaction of the epoxy system as well as its activation energy (E_a) based on the isoconversional methods of Kissinger and Ozawa. The process revealed a dependence of the activation energy on conversion (α). The morphology of the cured system was investigated by scanning electron microscopy (SEM). It showed a strong cross‐linking between the resin and hardner and a relatively better dispersion of surface modified filler nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd.     

Isothermal differential scanning calorimetry study of a glass/epoxy prepreg

Isothermal differential scanning calorimetry (DSC) was used to study the curing behavior of epoxy prepreg Hexply®1454 system, based on diglycidyl ether of bisphenol A (DEGBA)/dicyandiamid (DICY) reinforced by glass fiber. Cure kinetics of an autocatalytic‐type reaction were analyzed by general form of conversion‐dependent function. The characteristic feature of conversion‐dependent function was determined using a reduced‐plot method where the temperature‐dependent reaction rate constant was analytically separated from the isothermal data. An autocatalytic kinetic model was used; it can predict the overall kinetic behavior in the whole studied cure temperature range (115–130°C). The activation energy and pre‐exponential factor were determined as: E = 94.8 kJ/mol and A = 1.75 × 10¹⁰ sec^?1 and reaction order as 2.11 (m + n = 0.65 + 1.46 = 2.11). A kinetic model based on these values was developed by which the prediction is in good agreement with experimental values. Copyright © 2009 John Wiley & Sons, Ltd.     

基于HEA封端聚氨酯大孔树脂颗粒的合成、表征及水声声学性能

制备了丙烯酸-β-羟乙酯（HEA）封端的聚氨酯（PUA）大分子单体,采用正庚烷作致孔剂,用悬浮聚合法合成了聚氨酯-苯乙烯（PUA-St）及聚氨酯-苯乙烯-甲基丙烯酸乙酯-二乙烯基苯（PUA-St-EMA-DVB）AB-交联共聚物大孔树脂颗粒。SEM表明：合成的PUA-St-EMA-DVB颗粒含有规整的、孔径较大的孔洞,...     

Characterization and thermal stability of PMR polyimides using 7-oxa-bicyclo[2,2,1]hept-5-ene-2, 3-dicarboxylic anhydride as end caps

An anhydride monomer containing ether oxide bridge,7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride (ONA),was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride.The ONA was also studied as an end-cap for the polymerization of monomer reactant(PMR) type polyimides.Three molecular weight levels of the ONA end-capped PMR resins were evaluated.The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated.It was demonstrated that the imidized prepolymers using the end-cap have good processability,and the cured polyimide specimens exhibited good thermal stability.The initial decomposition temperature, T_d(ca.580℃) and glass transition temperature,T_g(330℃) of the novel resin(PI-20),prepared under optimum process conditions,compare favorably with the T_d(ca.620℃) and T_g(ca.348℃) of the state-of-the-art resin(PI’-20),respectively.     

Characterization of a modified silicon-containing arylacetylene resin with POSS functionality

A modified silicon-containing arylacetylene resin with a well-defined organic-inorganic POSS functionality was successfully synthesized by Huisgen azide-alkyne 1,3-dipolar cycloaddition.The POSS hybridized resin exhibits excellent thermal properties which were characterized by differential scanning calorimetry(DSC) and thermogravimetric analyses (TGA).Scanning electron microscope(SEM) was used to characterize fracture surface of the hybridized polymer.The results show that phase separation occurs.The POSS moieties are aggregated each other in the polymer to form 200-400 nm domains.     

酚醛树脂包覆氧化天然石墨作为锂离子电池负极材料

天然石墨经过浓硫酸氧化处理,酚醛树脂包覆并高温碳化后形成具有核壳结构的碳包覆氧化天然石墨复合材料.采用扫描电子显微镜(SEM),透射电子显微镜(TEM),X射线衍射(XRD),激光显微拉曼光谱(Raman)等检测技术对氧化处理以及酚醛树脂热解碳包覆前后天然石墨材料的结构与形貌进行分析与表征.结果表明,氧化处理与适量的酚醛树脂热解碳包覆有效修复了天然石墨表面的一些缺陷结构,使其表面更为光滑.电化学测试结果显示,经过氧化处理与酚醛树脂热解碳包覆后天然石墨材料电化学性能得到明显提高.酚醛树脂包覆量为9%时,复合材料表现出最好的电化学性能,其首次放电比容量为434.0mAh·g-1,40次循环后,放电比容量保持在361.6mAh·g-1,而未经处理的天然石墨放电比容量仅为332.3mAh·g-1.该改性方法有效提高了天然石墨材料的比容量,对其进一步应用具有重要意义.     

离子交换法处理曝气后氯化亚铜的废水研究

通过预曝气的方法,氯化亚铜废水溶液中Cu(Ⅰ)被氧化为Cu(Ⅱ),并能简化氯化亚铜废水溶液的粒子结构,分别采用201×7 OH-型强碱性阴离子树脂和732 Na型强酸性阳离子树脂处理曝气后的氯化亚铜废水,进行了曝气时间、pH值和温度等因素对废水处理效果的研究,得到最佳的处理废水条件。曝气180 min后,在温度60 ℃,V溶液/V树脂=2/1,阳离子交换反应15 min时,可使废水溶液中铜粒子浓度达到国家废水一级排放标准。     

微波协同阳离子交换树脂催化合成阿魏酸乙酯

以732型强酸性阳离子交换树脂为催化剂,在微波辐射下用阿魏酸与乙醇酯化合成了阿魏酸乙酯.通过单因素实验,考察了催化剂活化方法对催化剂活性的影响,结果表明,微波法活化阳离子交换树脂的催化性能好.通过单因素实验和正交实验,考察了催化剂用量、醇酸摩尔比、微波辐射时间、微波辐射功率等因素对反应的影响.确定了最佳反应工艺条件:阿魏酸0.1mol,酸醇摩尔比5:1,催化剂用量为反应物质量的35%,微波功率300w,反应时间30min,产率达84.2%.732型树脂催化剂可再生循环使用,重复使用4次,产率不低于80%.     

凝结水精处理阳树脂硫酸根溶出特性研究

电站给水系统中存在微量的SO42-就会对金属材料造成严重腐蚀。针对目前凝结水精处理系统投运后导致核电站蒸汽发生器或炉水中SO42-含量升高的问题,采用动态循环溶出和静态浸泡的方法对几种凝结水精处理常用阳树脂的SO42-溶出行为进行了研究。结果表明,不同树脂的SO42-溶出行为有较大差异,SO42-含量在短时间内随时间增长呈上升趋势,新树脂溶出SO42-的量比旧树脂大得多。通过对溶出液进行高温和氧化处理,发现溶出物中还含有一些有机磺酸盐,它们在高温或氧化条件下会分解产生SO42-和酸性物质。     

HPD-100树脂吸附小檗碱的热力学及动力学研究

研究了小檗碱在HPD-100树脂上的吸附热力学和动力学行为。考察了小檗碱在HPD-100树脂上的吸附等温曲线和吸附动力学曲线,确定了吸附过程的热力学及动力学参数。结果表明,HPD-100树脂对小檗碱的等温吸附可采用Langmuir方程描述、吸附为自发进行的放热型物理吸附过程;Dunwald–Wagnen内扩散方程能较好地拟合吸附动力学数据,吸附过程以颗粒内扩散为主要控制步骤,该吸附过程的表观活化能为29.11kJ/mol。本文为HPD-100树脂分离富集小檗碱类生物碱的实际应用提供基础数据及指导。