硅烷接枝聚乙烯储存稳定性的研究

利用熔体流动速率测定仪进行了硅烷接枝聚乙烯的水解缩合交联反应的加速试验,发现该反应对水分浓度为一级反应,反应的表现活化能４２ｋＪ／ｍｏｌ,由此可推算Ａ组份的保存期。当催化剂存在时,水解缩合反应明显加快,这时的表观活化能降到２０ｋＪ／ｍｏｌ。     

Pt／NM,Pd／NM催化剂上甲苯深度氧化反应动力学

在氧气过量的条件下，考察了Ｐｔ／ＮＭ、Ｐｄ／ＮＭ催化剂上甲苯深度氧化反应动力学及反应活性。Ｐｔ／ＮＭ催化剂对甲苯的氢化活性高于Ｐｄ／ＮＭ，深度氧化反应服从反应物强吸附双分子反应Ｌｔａｎｇｍｕｉｒ－Ｈｉｎｓｈｅｌｗｏｏｄ机理，其动力学方程为：相应的动力学参数，Ｐｔ／ＮＭ为：活化能△Ｅ＝４９．９ｋＪ／ｍｏｌ，吸附热Ｑ＝－２９．６ｋＪ／ｍｏｌ；Ｐｄ／ＮＭ为：△Ｅ＝９４．２ｋＪ／ｍｏｌ，Ｑ＝－１９．１ｋＪ／ｍｏｌ．     

硅橡胶热降解动力学的研究

用恒温热失重方法，研究了甲基硅橡胶（Ｓｉ—Ｏ—１），用氢氧化钾催化聚合的甲基硅橡胶（Ｓｉ—Ｏ—２），主链含环二硅氮烷的硅氮橡胶（Ｓｉ—Ｎ—１）以及它与Ｓｉ—Ｏ—１的共混物Ｓｉ—Ｏ—３和与Ｓｉ—Ｏ—２的共混物Ｓｉ—Ｏ—４的热降解反应动力学．结果表明Ｓｉ—Ｎ—１有最高的热稳定性，在氮气下，其降解反应活化能为３４４ｋＪ／ｍｏｌ．并且发现它分别与Ｓｉ—Ｏ—１和Ｓｉ—Ｏ—２的共混物的热稳定性大幅度提高．Ｓｉ—Ｏ—３在氮气下的降解活化能由未加入Ｓｉ—Ｎ—１前的１５２ｋＪ／ｍｏｌ提高到２３０ｋＪ／ｍｏｌ；Ｓｉ─Ｏ─４则由未混入Ｓｉ─Ｎ─１前的６１ｋＪ／ｍｏｌ提高到１４４ｋＪ／ｍｏｌ．我们认为这种作用机理是由于硅氮橡胶除去了微量吸附水和硅羟基并导致催化剂的离子对难于分离的结果．     

丁二烯－八甲基环四硅氧烷的嵌段共聚合研究 Ⅰ．嵌段共聚物合成及D4开环动力学

以α－甲基萘钾为引发剂，按顺序加入丁二烯，八甲基环四硅氧烷（Ｄ４）在ＴＨＦ中进行负离了嵌段共聚，制备了聚丁二烯－聚二甲基硅氧烷嵌段共聚物，讨论了聚合条件对嵌段共聚合过程的影响。考察聚丁二烯活性链引发Ｄ４进行嵌段共聚的反应动力学，求得在ＴＨＦ中３０℃时Ｄ４，开环链增长的表观速率为１０ｋｇ／ｍｏｌ．ｈ表观活化能为２８．３ｋＪ／ｍｏｌ。     

福建无烟粉煤流化床混合气催化气化表观动力学的研究

在一模试流化床中,首次报道了福建劣质无烟粉煤（挥发分〈５％）采用工业副产碱盐为主制备的复合催化剂进行混合气催化气化的结果,指出这一复合催化剂适宜的添加饱和度为１０％;表观动力学实验表明在该添加饱和度下,使反应表观活化能由无催化剂时的Ｅａ＝７６．０３ｋＪ／ｍｏｌ降为Ｅａ＝４５．８３ｋＪ／ｍｏｌ（几乎降低了４０％）,并且在气化温度８５０℃条件下,其表观反应速率常数比无催化剂时提高２．７倍;在气化温度８５０－９００℃,催化剂浓度１０％的适宜操作范围,可获得产气率Ｖ＝３．７７－３．５８ｍ＾３／ｋｇ（１ｋｇ煤）,煤气热值ＱＬＨＶ＝５．３１＝６．０３ＭＪ／ｍ＾３与冷煤气效率η＝７９．７２＝８５．７３％的良好结果,这对劣质无烟粉煤催化气化生产燃料气与化工副产碱盐制取廉价催化的工业化实践具有重要的应用价值与可操作的现实意义。     

阳离子交换树脂催化氯乙酸和甲醇酯化反应动力学

以强酸性阳离子交换树脂为催化剂合成氯乙酸甲酯，研究催化反应的动力学，研究确定为表观正、逆向二级反应，求得其表观活化能为Ｅａ＋＝３４．２０１ＫＪ／ｍｏｌ，Ｅａ＝４８．３０５ＫＪ／ｍｏｌ。     

硅氮聚合物交联剂交联的室温硫化硅橡胶的热稳定性

利用硅氮聚合物作交联剂使双组分缩合型室温硫化硅橡胶在不需要催化剂存在下硫化，通过对硫化胶老化后的热失重、交联密度和力学性能的测定，表明这种硫化胶的耐温性能由２００℃提高到３５０℃．对硫化胶的降解动力学研究表明：降解反应活化能由７０ＫＪ／ｍｏｌ提高到３３０ＫＪ／ｍｏｌ，这是由于消除了端基引发的主链降解．     

Theoretical Studies on the Mechanism of Mannich Reaction Involving Iminium Salt as Potential Mannich Reagent(4)——Use 2-Methylpropaldehyde as Pseudo-acid Component

以一个真实的Ｍａｎｎｉｃｈ试剂（ＣＨ３）２Ｎ＋ＣＨ２·Ｃｌ－作为研究对象．根据ＡＭ１方法的计算结果，胺、醛及伪酸在中性和酸性介质中的经典Ｍａｎｎｉｃｈ反应的关键步骤的活化能分别为３９０．０和３２１．８ｋＪ／ｍｏｌ．而由新Ｍａｎｎｉｃｈ试剂参与的Ｍａｎｎｉｃｈ反应的关键步骤活化能则为２７８．６ｋＪ／ｍｏｌ．因此新Ｍａｎｎｉｃｈ试剂可以提高反应速率，还分析了新Ｍａｎｎｉｃｈ试剂能降低反应活化能的原因．此外还讨论了另一种可大大降低活化能的新Ｍａｎｎｉｃｈ反应机理本文是研究Ｍａｎｎｉｃｈ反应机理的系列文章之一．     

在Pd(Ⅱ)-Cu(Ⅱ)/活性炭催化剂上水汽对CO氧化的影响

研究了ＣＯ在Ｐｄ（ Ⅱ） － Ｃｕ（ Ⅱ）／ 活性炭催化剂上的催化氧化反应，发现当空气中含有水汽时催化活性大大提高。并对ＣＯ 络合催化机理进行了讨论，求得总包反应级数约为１ ．３，表观活化能为５０ ．４６ｋＪ·ｍｏｌ－ １ 。     

在（TPA）2O—Na2O—SiO2—H2O系统中MFI型硅沸石的结晶行为（I）：结…

以四丙基溴化铵作模板剂，以白炭黑（Ｉ）、硅溶胶（Ⅱ）和水玻璃（Ⅲ）为不同硅源在１４０￣１８０℃合成ＭＦＩ型硅沸石。反应物配比相同，其结晶动力学曲线有明显差异。从它们的成核诱导期及生长速度计算出各体系硅沸石晶核形成活化能与生长活化能，在体系（Ｉ）中为４６／７６ｋＪ／ｍｏｌ，体系（Ⅱ）中为４１／４３ｋＪ／ｍｏｌ，体系（Ⅲ）中为３８／７９ｋＪ／ｍｏｌ。产物结晶粒径的大小由各体系成核活化能与生长活化能的差     

Isothermal cure kinetics of uncatalyzed and catalyzed diglycidyl ether of bisphenol-A/carboxylated polyester hybrid powder coating

The thermal cure behavior of diglycidyl ether bisphenol-A/carboxylated polyester hybrid powder coating system in the absence and presence of catalyst was monitored using differential scanning calorimetry. Curing temperatures were between 160 and 200?°C. The experimental results showed an autocatalytic behavior of the reaction, which could be described by the model proposed by Kamal. This model includes two rate constants k ₁ and k ₂ and two reaction orders m and n. The activation energies E _a1 and E _a2 of these rate constants were 51.7 and 42.3?kJ/mol for uncatalyzed cure reaction and 40.6 and 35.0?kJ/mol for externally catalyzed reaction. The average order of the overall reaction was found to be 2.45 and 2.72 for uncatalyzed and catalyzed system, respectively. Except for the late stage of cure reaction, the model agreed well with the experimental data, especially at high temperatures and in externally catalyzed cure reaction. A diffusion factor was introduced into the model to account for the effect of diffusion on the cure rate. The modified model greatly improved the predicated data at the late stage of cure reaction.     

CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅱ

Cure characteristics of hydroxyl terminated polybutadiene (HTPB) prepolymer with avariety of blocked toluene diisocyanate (TDI) in the presence of triethylamine (TEA) andchloroacetic acid catalyst are reported. Phenol, thiophenol, p-chloropheno1, p-nitrophenol,p-cresol, resorcinol, naphthols, caprolactam and butylated-hydroxytoluene were used as blockingagents. Viscosity measurements have been carried out using a mixture of HTPB and blocked TDIin cyclohexanone in the presence of the catalysts at 50℃ and 60℃ using Haake rotational vis-cometer. Viscosity measurements have also been carried out with 50% solids such as ammonium sulphate along with HTPB and TDI adduct.     

Synthesis of polyurethane acrylate oligomers based on polybutadiene polyol

Polyurethane acrylate oligomers (PUA) were prepared by a competitive reaction of 4,4′-dicyclohexyl methane diisocyanate (H₁₂MDI) with hydroxy terminated polybutadiene (HTPB) and hydroxyethylacrylate (HEA). Kinetic models were established for noncatalytic and catalytic systems, and the reaction constants were calculated using a numerical method. The evolution of the noncatalyzed and catalyzed reactions were analyzed, respectively, by SEC and FTIR. Comparing the reactivities of HTPB and HEA, as well as other small molar mass model alcohols, the HTPB showed the higher reactivity. HTPB is 700 times more reactive than HEA at 80°C. This high reactivity was analyzed as a result of lower concentration of hydrogen bonds in bulk HTPB. The activation energy of the noncatalyzed and catalyzed reactions were found to be, respectively, 56.98 and 45.16 KJ/mol. The structures of the PUA synthetized in one-step or two-step process were analyzed and discussed using a gelation model and the kinetic data obtained. © 1996 John Wiley & Sons, Inc.     

Liquid crystalline polyurethane. Polyurethanes containing bis-(p-oxymethylphenyl) terephthalate

Several polyurethanes based on bis-(p-oxymethylphenyl) terephthalate (BOPT) were synthesized and studied with respect to some of their thermal properties. BOPT exhibits a mesomorphic phase at 252–264°C. Polymerization was carried out by equimolar reaction with hexamethyl-ene diisocyanate (HDI), 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI) α,α'-diisocyanate-1,3-dimethylcyclohexane (H6 XDI), 4,4′-diphenylmeth-ane diisocyanate (MDI), 2,4-tolylene diisocyanate (TDI), and phenylene diisocyanate (PDI). It became clear that polyurethanes obtained from BOPT with HDI, H₁₂MDI, H₆XDI, and TDI have mesomorphic phases at 243–291, 214–250, 172–229, and 180–234°C, respectively, as determined by DSC and polarized microscopy, and that all polyurethanes are crystalline as evidenced by x-ray diffraction.     

Unsaturated poly(ester-imide)s from hydroxy-terminated polybutadiene, dianhydride and diisocyanate

Hydroxy terminated polybutadiene has been used for the first time in the synthesis of poly(ester-imide)s [P(E-I)s]. Anhydride terminated polyester prepolymers were prepared by the reaction of two different polyols--polytetramethyleneoxide glycol (PTMG) of molecular weight 1000 and hydroxy terminated polybutadiene (HTPB) of molecular weight 2500--and different dianhydrides--pyromellitic dianhydride (PMDA), benzophenonetetracarboxylic dianhydride (BTDA) and 4,4^′-(hexafluoroiso-propylidene)diphthalic anhydride (HFDA). The prepolymers were then reacted with different diisocyanates--80:20 mixture of 2,4- and 2,6-tolylene diisocyanate (TDI), 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and 4,4^′-methylene bis(phenylisocyanate) (MDI) resulting in P(E-I)s. The P(E-I)s were characterised by FT-IR, FT-NMR, GPC, TGA, DSC and for static and dynamic mechanical properties. The polymers based on PTMG showed two distinct melting points and behave as thermoplastic elastomers. The thermal stability and mechanical properties of P(E-I)s based on HTPB were substantially higher than those based on PTMG.     

Density functional theory study on mechanisms of epoxy‐phenol curing reaction

A comprehensive picture on the mechanism of the epoxy‐phenol curing reactions is presented using the density functional theory B3LYP/ 6‐31G(d,p) and simplified physical molecular models to examine all possible reaction pathways. Phenol can act as its own promoter by using an addition phenol molecule to stabilize the transition states, and thus lower the rate‐limiting barriers by 27.0–48.9 kJ/mol. In the uncatalyzed reaction, an epoxy ring is opened by a phenol with an apparent barrier of about 129.6 kJ/mol. In catalyzed reaction, catalysts facilitate the epoxy ring opening prior to curing that lowers the apparent barriers by 48.9–50.6 kJ/mol. However, this can be competed in highly basic catalysts such as amine‐based catalysts, where catalysts are trapped in forms of hydrogen‐bonded complex with phenol. Our theoretical results predict the activation energy in the range of 79.0–80.7 kJ/mol in phosphine‐based catalyzed reactions, which agrees well with the reported experimental range of 54–86 kJ/mol. © 2014 Wiley Periodicals, Inc.     

Biosynthesis of riboflavin. The reaction catalyzed by 6,7-dimethyl-8-ribityllumazine synthase can proceed without enzymatic catalysis under physiological conditions

6,7-Dimethyl-8-ribityllumazine is the biosynthetic precursor of the vitamin, riboflavin. The biosynthetic formation of the lumazine by condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and 3,4-dihydroxy-2-butanone 4-phosphate is catalyzed by the enzyme, lumazine synthase. We show that the condensation reaction can proceed without enzyme catalysis in dilute aqueous solution at room temperature and neutral pH. The reaction rate is proportional to e (pH). The activation energy of the uncatalyzed reaction is E(a) = 46.3 kJ mol(-)(1). The regioselectivity of the uncatalyzed reaction increases with pH and temperature (70% at 65 degrees C and pH 7.75). The data suggest partitioning of the uncatalyzed reaction via two different reaction pathways. The value of k(cat)/k(uncat) may be indicative for an entropy driven process for the enzyme-catalyzed reaction.     

咪唑封端聚氨酯予聚体改性环氧树脂E-51/双氰双胺固化体系性能研究

以聚丙二醇PPG10 0 0、甲苯二异氰酸酯 (TDI)、咪唑为原料 ,合成了咪唑封端的聚氨酯予聚体 ,简称扩链脲TIEU .利用DSC、粘弹谱仪、冲击试验机及扫描电镜 (SEM)等手段对TIEU改性的环氧树脂E 5 1/双氰双胺(dicy)固化体系的反应活性、动态力学行为、冲击性能、断裂面形态结构进行了系统研究 .实验结果表明 ,改性后的E 5 1 dicy体系反应活性明显提高 ,固化反应的表观活化能由未改性体系的 131kJ mol降至 75～ 80kJ mol.与咪唑促进体系比较结果显示 ,两种固化反应的促进机制具有一定的差异 .另外与未改性体系相比 ,经过改性的环氧树脂体系冲击强度提高 2～ 3倍 ,而玻璃化温度和模量基本不变 ,冲击断面呈韧性断裂     

Partial Carbamoylation of Cellulose Microspheres:a New Method to Prepare Adsorbents for Liquid Chromatography简

Micron-sized cellulose microspheres were prepared through sol-gel method using NaOH/urea solution to dissolve cellulose, then cross-linked by 1,6-hexanylene diisocyanate （HDI）, toluene 2,4-diisocyanate （TDI） and 1,4-phenylene diisocyanate （PDI）, respectively. The reaction conditions for partial modification of the microspheres were studied. The degree of substitution （DS） in cellulose was controlled by adjusting the reaction conditions. HDI-crosslinked microspheres were partially modified with phenyl isocyanate to obtain chiral stationary phases （CSPs）. The CSPs of a lower degree of crosslinking （DC） showed better chiral recognition ability than those of a higher DC. Meanwhile the CSPs prepared by pre- modification exhibited better chiral recognition ability than those prepared by pre-crosslinking.     

CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅰ

Controlled release of TDI and hence the cure characteristics of several blocked TDI with HTPB are reported. The reactions were followed through viscosity measurements as a function of time and temperature under the catalytic influence of triethylamine. The effect of nature of substituents present on the end capping substrate, temperature, solvent, basicity of catalyst and kinetics thereon have been studied.