Effect of TPB on curing reaction of HTPB-TDI

Catalysis effect of triphenyl bismuth （TPB） on kinetics of hydroxyl terminated polybutadiene-toluene diisocyanate （HTPB-TDI） curing reaction was studied by non-isothermal differential scanning calorimetry （DSC）. The characteristic temperature of curing system was measured for calculating kinetic parameters and establishing curing reaction kinetic equations. The results show that activation energy （Ea） of uncatalyzed HTPB-TDI curing system is 51.29 kJmol-1, and TPB decreases Ea to 46.43 kJ＇mol-1. Catalyst lowers reaction temperature and shortens curing time through decreasing ac- tivation energy of curing reaction and accelerating reaction rate. TPB can increase the reaction rate at 27 ℃ to the value of uncatalyzed system at 80 ℃. The catalytic activity reaches the maximum when concentration is 0.5 %.

Study of catalytic effect of ammonium molybdate on the bisphthalonitrile resins curing reaction with aromatic amine

A kind of catalyst, ammonium molybdate was developed in this paper to promote the curing reaction of bisphthalonitrile resins with aromatic amine as curing agent, and the catalytic effect was studied by differential scanning calorimetry （DSC）, rheometric measurements and thermogravimetric analysis （TGA）. The results indicated that the catalyst could improve the curing rate and increase the curing degree, which could be regulated by the content of the catalyst used in the reaction.

Study on curing reaction of 4-aminophenoxyphthalonitrile/bisphthalonitrile

A series of phthalonitrile blending resins were prepared from 4-aminophenoxyphthalonitrile(APN) and 4,4'-bis(3,4- dicyanophenoxy)biphenyl(BPH) by directly powder-mixing and copolymerization.Differential scanning calorimeter(DSC) and dynamic rheology were used to study the curing reaction behaviors of APN/BPH blends,and the results indicated that the introduction of APN accelerated the curing rate of BPH,and the existence of BPH decreased the curing temperature of APN/BPH systems.The thermal stability of postcured APN/BPH resins was investigated by thermogravimetric analysis(TGA),and the TGA results indicated that the crosslinked polymers of APN/BPH systems possessed good thermal stability.

Curing reaction and mechanism of phenol-formaldehyde novolac resins for foundry

In this study on the curing dynamics of phenol-formaldehyde novolac resins(PFNR) and hexamethylene tetramine(HMTA), two typical commercial PFNR were selected as examples and the curing reactions of the resins with HMTA were studied by differential scanning calorimetry(DSC). Based on the data calculated by the Kissinger equation and the Crane equation, a thermocuring dynamic model was established, from which the process conditions, activation energy, reaction kinetics equation and a f irst-order reaction of the curing reactions were derived.

Synthesis of 3-Methylbutanal by Strecker Reaction at Unelevated Temperature and in Acidic Systems

3-Methylbutanal was obtained by the Strecker reaction with L-leucine and D-ribose at unelevated temperature and acidic conditions. Volatile compounds from reaction systems were analyzed by solid phase microextration （SPME） coupledwith gas chromatography-mass spectroscopy （GC-MS）. The formation mechanism of 3-methylbutanal was also proposed. Various reaction conditions were investigated, including reaction time, reaction temperature, pH value and salt content of the system.

MECHANICAL RELAXATION AND INTERMOLECULAR INTERACTION IN EPOXY RESINS/POLY (ETHYLENE OXIDE) BLENDS CURED WITH PHTHALIC ANHYDRIDE

The miscibility of the blend,composed of a bisphenol A epoxy resins (Diglycidyl ether of bisphenol A) (DGEBA) and poly(ethylene oxide) (PEG) and crosslinked by phthalic anhydride (PA) was studied using dynamic mechanical method. Single glass transition temperatures intermediate between the two pure components were observed for all blend levels. The secondary relaxation mechanism should relate to not only diester linkage, but also hydroxyether structural unit in the system. Fourier transform infrared spectroscopy (FTIR) is applied to study the curing reaction and intermolecular specific interaction of the system. The results indicate the PEO participates the crosslinking reaction, accelerates the curing reaction and make the reaction more perfect. The shifts of the hydroxyl band and carbonyl band demonstrate the presence of the intermolecular interaction in the cured blend. Moreover, the molecular interaction between the side hydroxyl in the hydroxyether units and the ether bond in PEO macromolecules is stronger.

Curing Reaction Model of Epoxy Asphalt Binder

In order to understand the strength developing law of the epoxy asphalt mixture,a curing reaction model of the epoxy asphalt binder was proposed based upon the thermokinetic analysis.Given some assumptions,the model was developed by applying the Kissinger law as well as Arrhenius equation,and the differential scanning calorimetry was performed for estimating the model parameters.To monitor the strength development of the epoxy asphalt mixture,a strength test program was employed and then results were compared to those produced from the proposed model.The comparative evaluation shows that a good consistency exists between the outputs from test program and the proposed model,indicating that the proposed model can be used effectively for simulating the curing reaction process for the epoxy asphalt binder and predicting the strength development for the epoxy asphalt mixture.

Statistical deduction and experimental verification on kinetic equations for the curing reactions of epoxy resins/amines

Based on three typical mechanisms (second-order, third-order and competitive mechanisms) for the curing reactions of the epoxy resins with amines, a pair of the kinetic equations (for primary and secondary aminations) was presented to explain the uniformity and relationship among the three different kinetic mechanisms of the reactions. The presented macro-equations were deduced from the kinetic micro-equations by the statistics method. And the constitutive equations were verified by experimental data at different reaction times and temperatures (95°C, 60°C and 39°C), taking diglycidyl ether of bisphenol A (DGEBA) /ethyleneamine (EA) as a model.

STUDY ON THE POST-CURE KINETICS OF EPOXY RESIN IRRADIATED BY AN ELECTRON BEAM

The post-cure kinetics of electron beam (EB) curing of epoxy resin initiated by diaryiodinium was investigated. The post-cure reaction fits first order reaction kinetics. The reaction rate constant increases with increasing treatment temperature of post-cure. The reaction rate of post-cure is much lower than the rate of its reaction on electron beam treatment.

CURE OF A MICROGEL-EPOXY RESIN TWO-PHASE POLYMER WITH ETHYLENE DIAMINE

The curing of a microgel-epoxy resin two phase polymer prepared by in situ copolymerization of unsaturated polyester with acrylic monomer was studied. The unsaturated unit reacted with N—H during the cure of the resin with ethylene diamine. The Michael type reaction was ten times more rapid than the addition of N—H to epoxide.This was accounted for the lower apparent activation energy of the curing of the two phase resin.

超声在线监测不饱和聚酯树脂固化过程及其动力学行为

为探索不饱和聚酯树脂(UPR)固化体系在不同温度下的超声振幅变化规律,采用超声波穿透技术对UPR固化过程进行在线监测,获得声速、储能模量、松弛时间、凝胶时间等动力学参数变化规律,并得到固化反应动力学方程。结果表明:温度越高,声速与储能模量变化越快,且最终数值也越大,而固化松弛时间与凝胶时间随温度增加而缩短;此外,超声法与差示扫描量热法(DSC)得到的固化度曲线变化高度一致,通过2种方法所得到的反应活化能分别为38.14 kJ/mol和45.3 kJ/mol;最终,通过DSC法确定了UPR固化反应动力学级数为0.92。总之,超声法与DSC法2种方法相互结合,不仅证明了超声结果的准确性,也为UPR固化过程提供一种精准的在线监控技术和量化方法,从而为UPR生产过程提供理论指导。

水凝胶紫外光固化建模仿真

利用COMSOL Multiphysics仿真软件对紫外光固化进行建模和仿真,探究了单体浓度、引发剂浓度和氧气浓度对紫外光固化反应速度的影响。仿真结果表明:随着单体浓度和引发剂浓度的增加,反应逐渐加快;而随着氧气浓度的增加,反应先加快而后减慢,即氧阻聚现象。通过PEGDA水凝胶紫外光固化实验验证了单体浓度与反应速度的关系。

取代基对氰基官能化苯并噁嗪树脂固化反应及热稳定性的影响

基于含不同取代基的酚与间氨基苯甲腈合成了3种含氰基苯并噁嗪单体(PH-bn、mPHbn、aPH-bn),并固化得到苯并噁嗪树脂(poly(PH-bn)、poly(mPH-bn)、poly(aPH-bn))。采用傅里叶变换红外光谱(FT-IR)、核磁共振氢谱(^(1)H-NMR)、凝胶渗透色谱(GPC)对苯并噁嗪单体的结构与组成进行了表征,通过差示扫描量热分析(DSC)比较了取代基对固化行为的影响,并进一步探讨了固化反应机理。此外,采用热重分析(TGA)和热重分析-红外联用(TGA-FTIR)研究了3种固化物的热稳定性和热解机理。结果表明:噁嗪环与部分氰基在固化过程中同时发生交联反应。给电性甲基的存在使得体系的固化反应峰值温度增加、热稳定性降低;而吸电性醛基使得体系的固化反应峰值温度降低,同时醛基的交联反应使体系的热稳定性显著增加。poly(aPH-bn)的5%失重温度为380℃,800℃时N_(2)气氛下残炭率高达67.3%。

增硅与养护温度对底灰碱激发材料性能影响的研究

为了探索效益更高的城市生活垃圾焚烧底灰碱激发材料的制备方式,对底灰碱激发材料开展了配合比设计、强度试验及微观分析,分析了养护温度及不同配合比底灰碱激发试件抗压强度发展的影响,并结合XRD、SEM-EDS、FT-IR等微观检测技术分析了聚合反应机理。结果表明:当底灰粒径不大于1.25 mm时,使用体积比为2∶1的水玻璃溶液与氢氧化钠溶液,底灰碱激发试件的抗压强度达到最优;密封条件下复合养护温度更有利于聚合反应的进行与聚合产物的生成。

烯丙基醚化酚醛亚胺树脂的固化动力学研究

采用差示扫描量热仪测定了不同升温速率下烯丙基醚化酚醛亚胺树脂(APMI-F树脂)的DSC曲线,用非等温热力学的研究方法研究了APMI-F树脂的固化反应动力学。用T-β外推法确定了APMI-F树脂的固化反应的起始温度Ti、峰值温度Tp和终止温度Tf,并将其作为探究APMI-F树脂固化工艺的依据。通过Kissinger法和Starink法求得APMI-F树脂的表观活化能,由Starink法得到不同固化度下的表观活化能,并将其与试验数据对比,以验证固化动力学模型的准确性。研究结果表明:(1)利用外推法确定了APMI-F树脂固化反应的Ti、Tp和Tf分别为161.09、226.81、263.42℃;(2)Starink法求得的平均活化能要高于Kissinger法所得数据;(3)在固化反应过程中,随着固化程度的升高,APMI-F树脂的表观活化能呈现先降低后升高的趋势,固化初期活化能因黏度的降低而降低,随着交联度的提高,链段运动受到限制导致活化能渐渐升高;(4)采用Málek法成功地建立了APMI-F树脂的固化动力学模型,通过与试验数据对比,发现该模型能够很好地描述APMI-F树脂的固化过程。

考虑热-化学耦合的NEPE推进剂固化过程数值模拟

采用热-化学耦合模型表征热传导和固化动力学反应,利用物理试验测定硝酸酯增塑聚醚(NEPE)推进剂在不同固化度下的热参数和密度,研究了NEPE推进剂药柱在固化过程中温度场和固化度的分布和演变规律。结果表明,因推进剂固化反应的生热速率与外界热量传递速率存在差异,导致固化过程中出现内部温度场和固化度场分布不均匀的现象。固化时间为1~4 d时,药柱中心位置的温度较高(最高57.6℃),外侧较低;固化时间大于等于5 d时,药柱温度场慢慢与环境温度(50℃)趋向于平衡。推进剂固化度-时间曲线近似为“S”型,固化时间小于1 d时和大于4 d时,固化速率缓慢;固化时间2~4 d时,固化速率快。固体发动机的m数对推进剂固化温度和固化速率有一定影响,m数越大,推进剂的最高温度越高,同时温差也越大,温度差会导致推进剂药柱内部固化速率产生差异,造成推进剂达到指定固化度的时间变长。

二氧化碳养护水泥基材料的研究进展

水泥基材料通过碳化反应可以快速形成以碳酸盐和高聚度硅胶为主要产物的固碳制品。固碳制品因其可以兼顾CO_(2)消纳能力与优良的力学性能受到了广泛的关注。国内外研究团队在原材料开发、组成与工艺优化、养护制度设计等基础上,开发了多种应用场景,主要包括板材、小型砌块、骨料等。从碳化反应机理与动力学出发,归纳了反应条件对结构与产物组成的影响规律,总结了现有制品的种类、性能与应用现状,以期为建材工业的碳减排提供新的思路。

活性钙含量与养护温度对底灰碱激发材料性能的影响

为了探索效益更高的城市生活垃圾焚烧底灰碱激发材料的制备方式,对底灰碱激发材料开展了配合比设计、强度试验及微观分析,分析了养护温度及不同配合比底灰碱激发试件抗压强度发展的影响,并结合XRD、SEM-EDS、FT-IR等微观检测技术分析了聚合反应机理。结果表明:当底灰粒径不大于1.25 mm、水玻璃溶液与氢氧化钠溶液体积比为2∶1时,粒化高炉矿渣含量的提高会在一定程度上提高底灰碱激发试件的抗压强度;密封条件下复合养护温度更有利于聚合反应的进行与聚合产物的生成。

OPC-MCA固化剂对盾构废泥的固化性能及其微观作用机制研究

通过添加高炉矿渣(GGBS)、脱硫石膏(FGDG)、铝酸钙粉、生石灰和明矾到普通硅酸盐水泥P.O42.5(OPC)中,制备一种新型盾构废泥改良材料OPC-MCA。首先,通过正交测试法确定OPC-MCA中各原料的最优配比。然后,使用该材料和OPC在10%~40%的掺量下处理芜湖市城南过江隧道工程产生的盾构废泥,并检测不同固化时间(3、7、28 d)下的抗压强度。最后,采用扫描电镜(SEM)、工业CT系统和X射线衍射(XRD)观察和分析固化后废泥试样的微观形貌、孔隙和裂纹特征以及矿物成分变化。研究结果表明:OPCMCA的最优材料配比为51%OPC、32%GGBS、8%FGDG、5%铝酸钙粉、3%生石灰、1%明矾;OPCMCA对芜湖盾构废泥的固化能力比OPC的强,在低掺量情况下更是如此;固化剂掺量和固化时间的增加会导致试样强度增加、脆性增强,并使部分试样转变为拉伸破坏;在OPC-MCA固化的试样中检测到了OPC固化试样中未检测到的水化硅铝酸钙(C-A-S-H)和单硫型硫铝酸盐(AFm),并且钙矾石(AFt)含量也更高;在同等掺量下,OPC-MCA固化试样中大尺寸孔隙的比例以及孔隙的总体积均比OPC固化试样的小。

UV及潮气双重固化硅树脂的制备及性能研究

以含氢MQ硅树脂(HMQ)和1,2-环氧-4-乙烯基环己烷(VCHO)为原料,2,6-二叔丁基-4-甲氧基苯酚(BHT)为抗氧化剂,无水甲苯为溶剂,在铂的乙烯基络合物催化作用下通过硅氢加成反应制备得到含有脂环族环氧官能团和硅羟基的有机硅树脂,通过核磁共振波谱(NMR)、傅里叶红外光谱(FT-IR)以及凝胶渗透色谱(GPC)等手段对树脂结构进行了表征。对合成的脂环族环氧官能化硅树脂进行UV及潮气双重固化实验,探究了UV光照时间、脂环族环氧基含量以及Si-OH含量等因素对硅树脂材料性能的影响。结果表明:当UV光照时间为20s时,制备得到的双固化树脂材料的综合性能良好,凝胶率大于80%、吸水率小于2.4%、水接触角大于111.2°、氮气中5%失重温度大于370℃、空气中5%失重温度大于340℃、玻璃化转变温度(T_(g))大于17℃、铅笔硬度大于4H(3d)。