均匀设计优化环氧橡胶籽油的制备工艺

以橡胶籽油、甲酸和双氧水为原料,磷酸作催化剂,采用无溶剂法合成环氧橡胶籽油,采用均匀设计法研究了甲酸用量、反应时间及双氧水用量等对环氧值的影响。结果表明,最佳制备工艺条件为:橡胶籽油100 g,甲酸12.80 g,质量分数为30%的双氧水50.53 g,反应时间6 h,反应温度50～55℃,产品环氧值达11.68%。     

天然胶乳／甲酸／过氧化氢混合物的酸度效应

研究了天然胶乳／甲酸／过氧化氢混合物的酸度效应,探讨了混合物的酸度与其组成及停留时间的关系。结果表明,过氧化氢可使pH＝2．0的天然胶乳－甲酸混合物的pH值显著下降,对于pH＝2．0的天然胶乳／甲酸／过氧化氢混合物,随着停留时间的推移,体系的pH值在初期发生显著的下降,随后又上升并超过初始pH值。天然胶乳／甲酸／过氧化氢混合物所表现的上述酸度效应是混合物中所含天然橡胶、甲酸和过氧化氢之间相互作用和反应情况的综合体现。     

Kinetics of graft polymerization of styrene on cis-1,4-polybutadiene

By measurements of polymerization rate, grafting efficiency and number-average molecular weight of free and grafted polystyrene, the α-dicumyl peroxide initiated polymerization of styrene on cis-1,4-polybutadiene at 100°C and at low extents of reaction was studied. The polymerization rate and the polystyrene molecular weights decreased with the rubber content of the solution. The grafting efficiency was found to be substantially independent of the peroxide concentration, but to increase with rubber content. A rigorous mathematical model of the reaction was developed, from which it has been possible to confirm the proposed mechanism and to establish the value of many kinetic constants.     

The curing retardation and mechanism of high temperature vulcanizing silicone rubber filled with superconductive carbon blacks

The curing retardation and mechanism of high‐temperature vulcanizing silicone rubber (HTV SR) filled with superconductive carbon black (CB) BP2000 have been studied experimentally and theoretically. The results show that both rubber matrix and CBs have influences on the peroxide curing of rubber/CBs composites. The retardation does not appear as prominent in nature rubber (NR)/BP2000 composites as in HTV SR/BP2000 composites. Quantum chemistry calculations reveal that the curing retardation of HTV SR/BP2000 composite should not be attributed to the curing reaction dynamics of HTV SR molecules. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) analyses of CBs show that the effect of radical scavenging of phenol‐OH groups existing on BP2000 surface is the main reason for the retardation in the peroxide curing reaction. The effect is found to be more effective in HTV SR/BP2000 composite and thus retards its curing. The curing retardation does not appear in silicone rubber (SR)/BP2000 composites vulcanized by condensation reaction, and the resulting vulcanizates have excellent physical properties. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Kinetics investigation on the hydrogenation of acrylonitrile-butadiene rubber latex by using new catalytic reaction system

The kinetics of hydrogenation of acrylonitrile-butadiene rubber latex with hydrazine hydrate/hydrogen peroxide/selenium catalytic reaction system was investigated by calculating the initial reaction rate constants. The reaction rate constants of the reaction system were obtained by initial reaction measurements of different reactant dosages, such as selenium, hydrazine hydrate, and hydrogen peroxide. Hydrogenation rate constants and reaction order corresponding to the various factors were obtained from the hydrogenation kinetic data. The kinetic equation of this reaction system between 50–70 °C and the reaction activation energy was derived.     

Modification of rubber powder with peroxide and properties of polypropylene/rubber composites

Waste tire powder was functionalized in the presence of various concentrations of allylamine and benzoyl peroxide. Fourier transform infrared spectroscopy studies confirmed the presence of allylamine on the surface of the rubber powder. The surface energy of the functionalized rubber powder revealed that the introduction of allylamine onto the rubber powder surface increased the surface activity. Improvements in the tensile strength, elongation at break, and storage modulus were observed for polypropylene/modified rubber powder/maleic anhydride grafted polypropylene, and this was attributed to an improvement in the compatibility due to the chemical interaction between the rubber powder and compatibilizer. Evidence for the reaction between the rubber surface and compatibilizer was observed in Fourier transform infrared studies. This peroxide‐initiated monomer‐grafting technique is feasible for large‐scale processes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2237–2243, 2007     

Dicumyl peroxide cross‐linking of nitrile rubbers with different content in acrylonitrile

The scope of this article is the study of peroxide curing of two nitrile rubbers with low and high nitrile content. The peroxide efficiency can be much higher than one, and the polymer structure determines the mechanism of cross‐linking. In the rubber with low nitrile content, the peroxide radical may give rise to a polymerization reaction between adjacent double bonds generating a heterogeneous network with a negative effect on the vulcanizate properties. On the contrary, in the nitrile rubber with high nitrile content, this negative effect it is not present or is present to a lesser extent, and their vulcanizates show good physical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1–5, 2005     

Differential thermal analysis using high frequency dielectric heating II. Curing kinetics studies

A previous paper described the theory and equipment of Differential Thermal Analysis using High Frequency Dielectric Heating, DTA/HF. Curing studies using DTA/HF on cis-1,4-polyisoprene rubber filled with 50 phr of CaCO₃ and containing from 1.5 to 4.5 phr of dicumyl peroxide (DCP) curative indicated that below about 185°C, the curing reaction was first order with respect to DCP; the mean activation energy was 32.6 kcal/mole; and the heat of reaction ranged from 60 to 80 kcal/mole DCP. These results are in agreement with published results. Above 185°C both thermodynamic and kinetic evidence implied that the reaction mechanism changed; the first order peroxide decomposition no longer controlled the overall rate of reaction. The curing of both stereo styrene-butadiene rubber (SBR) and cis-1,4-polybutadiene rubber (BR) containing 50 phr of CaCO₃ and 0.5 phr of DCP was found to follow first order kinetics as expected. The magnitude of the heat of curing was used to determine the frequency of a vinyl propagation-type cross-linking reaction. Eight to 36 crosslinks per molecule of DCP were obtained. This reaction became more extensive at high temperature, in agreement with published results.     

环氧化稀土异戊橡胶的制备与表征

以过氧化氢为氧化剂,甲酸为催化剂对稀土异戊橡胶（Ln-IR）进行环氧化改性。采用核磁共振氢谱（1 H-NMR）对制备的环氧化Ln-IR的结构进行了表征,并进行了定量计算。结果表明,在反应温度40～60℃,反应时间2～5h,甲酸与过氧化氢物质的量的比约为1时,环氧化度较高且没有副反应发生。     

混炼硅橡胶的配合技术(九)

介绍了用2，4-二氯过氧化苯甲酰作硫化剂的挤出成形用混炼硅橡胶（包括低硬度混炼硅橡胶、不粘连芯线的混炼硅橡胶、高电气强度电线用混炼硅橡胶）的配制方法及改进其加工和表面性能的方法；同时，还介绍了用甲基苯甲酰类过氧化物作硫化剂时改进混炼硅橡胶表面性能的方法（包括添加含氢硅油、硅藻土、二烷基过氧化物或过氧化苯甲酰以及细化硫化剂粒子）。     

均匀设计优化硒催化氢化丁腈橡胶乳液的研究

以硒粉为催化剂,水合肼和过氧化氢为氧化还原引发体系,进行了常温常压下的丁腈橡胶乳液加氢反应,采用均匀设计法研究了水合肼用量、硒粉用量、过氧化氢用量、二酰亚胺凝胶抑制剂用量、反应温度以及反应时间等对丁腈橡胶氢化度的影响,并利用红外光谱对氢化产物进行了表征.实验结果表明,在适宜的反应条件下,可制得氢化度为90％的氢化丁腈橡...     

新型橡胶密封件交联体系的研究

在橡胶密封件硫化体系中,由于硫磺硫化体系压缩永久变形性能比较差,而最常用的过氧化物交联剂过氧化二异丙苯的硫化胶容易产生刺鼻的异味,从而限制了它在高档制品中的用途。本实验使用1,4-双叔丁基过氧异丙基苯做为丁腈橡胶交联剂。实验结果表明:使用1,4-双叔丁基过氧异丙基苯做为交联剂的硫化胶不仅在综合性能上优于过氧化二异丙苯,而且也避免了刺鼻异味的产生。并且和硫磺硫化体系相比它也大大改善了硫化胶的压缩永久变形性能,从而拓宽了过氧化物交联体系在密封制品中的用途。同时,本文还研究了双组分补强填料对丁腈橡胶的补强效果。     

Grafting of acrylate monomers onto chlorinated rubber

Grafting of chlorinated rubber with ethylacrylate and butyl methacrylate in xylene solution has been studied using benzoyl peroxide as the initiator. It is observed that the grafting reaction follows conventional kinetic behavior under the present experimental conditions. The energies of activation obtained for both monomers were 10.8 and 10.95 K.cals, respectively. The grafting efficiency and percent grafting were calculated. Additional proof for grafting onto chlorinated rubber was also obtained by characterization of the graft copolymer by gel permeation chromatography.     

Epoxidation of Unsaturated Rubbers with Alkyl Hydroperoxide using Molybdenum Compounds as Catalyst in the Reactive Processing Equipment

A novel approach to the epoxidation of unsaturated rubbers in a reactive processing equipment is presented for the first time in this paper. The effects of the structures of unsaturated rubbers and catalysts on the epoxidation reaction were examined. The experimental results show that the reactivity of three typical unsaturated rubbers follows the decreasing order: ethylene‐propylene‐diene rubber (EPDM) > butadiene rubber (BR) > styrene‐butadiene rubber (SBR). No obvious further oxidation side reaction occurs during the epoxidation of EPDM and BR, while SBR has a significant degradation during reaction. Moreover, investigation of the catalytic system composed of tert‐butyl hydroperoxide (TBHP) and three different molybdenum compounds reveals that a blue molybdenum compound (Mo‐b), which is the product of the reaction of hydrogen peroxide (30% aqueous solution) with an excess of molybdenum powder, gives the highest catalytic activity and the highest efficiency of TBHP.     

接枝改性法制备天然橡胶吸油材料的工艺研究

以丙烯酸丁酯为单体,N,N′-亚甲基双丙烯酰胺为交联剂,过氧化苯甲酰为引发剂,采用乳液聚合法合成吸油性橡胶。研究了引发剂和交联剂种类和用量、反应时间和温度、天然胶乳和单体配比对吸油性能的影响,并对吸油橡胶的吸油倍率及对水面浮油的回收性能等进行了考察。通过对煤油等几类油品的吸收对比,确定最佳的工艺条件。制得的吸油橡胶吸煤油最高可以达11.92g/g;吸四氯化碳为15.21g/g。     

Kinetic modeling of the epoxidation of natural rubber with in-situ–formed peracid

In the presence of excess hydrogen peroxide and formic acid the latex stage epoxidation of natural rubber is pseudo–first order in nature. A kinetic model is developed to predict the maximum extent of epoxidation for the reaction system and its variation with increasing acid concentration. Th dependence of the overall rate constant on acid concentration is also studied.     

Structural characterization of vulcanizates. Part IX. Comparison of the vulcanization of natural rubber and cis-trans-isomerized natural rubber with sulfenamide-accelerated sulfur and dicumyl peroxide vulcanization systems

Large variations in the microstructure of 1,4-polyisoprenes, from ca. 100% cis-trialkylethylene groups, as in natural rubber (NR), to ca. 40% cis- and 60% trans-trialkylethylene groups, as in an equilibrium-isomerized NR, have little influence on the overall chemistry of vulcanization of the polyisoprenes by a N-cyclohexylbenzothiazole-2-sulfenamide-accelerated sulfur system or by a dicumyl peroxide system. The peroxide crosslinks the equilibrium-isomerized NR more efficiently than it crosslinks NR; this is attributed to the sulfur dioxide, which is used to isomerize the NR, scavenging some of the nonrubber constituents in the NR, which are known to compete with the rubber hydrocarbon for reaction with free radicals from the peroxide. By comparison with NR vulcanizates, the corresponding equilibrium-isomerized NR vulcanizates have higher values of the C₂ term of the Mooney-Rivlin stress–strain equation and higher χ (polymer–swelling liquid interaction parameter) values of the Flory-Huggins equation.     

端羟基聚丁二烯液体橡胶的环氧化研究

采用过氧甲酸原地法对端羟基聚丁二烯液体橡胶(HTPB)进行环氧化,通过过氧化氢消耗率、环氧值及开环几率详细讨论了反应温度、反应时间、原料配比等因素对环氧化反应影响的规律。并对环氧化产物(E HTPB)的固化性能进行了研究,实验表明EHTPB用于环氧树脂改性时有较好的共混相容性,能显著提高环氧树脂固化物的柔韧性和耐热性。     

有机硅过氧化物偶联剂在粘接上的应用

本文以有机硅过氧化物偶联剂乙烯基三特丁基过氧基硅烷（VTPS）为例,介绍了有机硅过氧化物偶联剂的粘接机理和使用方法,以实际应用数据对比的方式讨论了有机硅过氧化物偶联剂在特种橡胶（硅橡胶、氟像胶）与各种金属材料粘接上的应用,显示出有机硅过氧化物偶联剂在粘接方面优异的性能。     

Adhesion behavior of natural rubber‐based adhesives crosslinked by benzoyl peroxide

The loop tack, peel, and shear strength of crosslinked natural rubber adhesive were studied using coumarone‐indene and toluene as the tackifying resin and solvent, respectively. The concentration of benzoyl peroxide‐the crosslinking agent—was varied from 1 to 4 parts per hundred parts of rubber (phr). A SHEEN hand coater was used to coat the adhesive on the polyethylene terephthalate substrate at various coating thickness. Loop tack, peel, and shear strength were measured by a Llyod adhesion tester operating at 30 cm min^?1. Result shows that loop tack and peel strength of the adhesive increases up to 2 phr of benzoyl peroxide concentration after which it decreases with further benzoyl peroxide content. This observation is attributed to the optimum crosslinking of natural rubber where optimum cohesive and adhesive strength occurs at 2 phr peroxide loading. However, for the shear strength, it increases with increasing benzoyl peroxide concentration where higher rate of increase is observed after 2 phr of peroxide content, an observation which is associated to the steady increase in cohesive strength of crosslinked rubber. In all cases, the adhesion properties of adhesives increase with increase in coating thickness. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012