Effect of crosslinking on the conductivity of conductive silicone rubber

We investigated the effect of polyvinylsilicone oil (C gum) as a crosslinker and 2,5‐bis(tert‐butyl peroxy)‐2,5‐dimethyl hexane (DBPMH) as a curing agent on the conductivity of conductive silicone rubber with two different kinds of conducting mechanisms. The experimental results show that the volume resistivity of conductive silicone rubber changed with its degree of crosslinking. When the carbon black loading was 25 parts per hundred rubber (phr) and a completely continuous conducting network had not formed, the volume resistivity of the vulcanizates decreased with increasing crosslink density. The volume resistivity of the vulcanizate with a suitable amount of C gum decreased to 53%, and the tensile strength increased by 0.8 MPa compared to the vulcanizate without C gum. When the carbon black loading was 40 phr and a completely continuous conducting network had formed, the crosslink density of vulcanizates changed as the amount of DBPMH changed. The volume resistivity of vulcanizates first decreased and then increased with increasing crosslink density. There was a valley value in the resistivity–crosslink density curve. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3471–3475, 2003     

Synthesis and characterization of maleated rosin‐modified fluorosilicone resin and its fluorosilicone rubber

Imide‐containing vinyl fluorosilicone resin (MR‐VFS) was synthesized from maleated rosin (MR). And then, with MR‐VFS as a new polar cross‐linking agent in a heat curable fluorosilicone rubber composition, a series of maleated rosin‐modified fluorosilicone rubbers (MR‐FSR) were obtained. The effects of MR‐VFS on the mechanical properties, oil resistance, thermal stability, and low‐temperature performance were studied in detail. It was found that MR‐VFS could increase the tearing strength and high‐temperature thermal stability of fluorosilicone rubber. When the MR‐VFS weight content reached to 2 wt %, the tearing strength of MR‐FSR increased by 20.1% compared with that of common fluorosilicone rubber. However, MR‐FSR showed a similar low‐temperature resistance and a little worse oil resistance. The morphological study showed that incorporation of maleated rosin could intensify the microphase separation of fluorosilicone rubber. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41888.     

Curing characteristics,morphology, thermal stability,mechanical properties,and irradiation resistance of methylethylsilicone/methylphenylsilicone rubber blends

Methylethylsilicone rubber (MESR)/methylphenylsilicone rubber (MPSR) blends were cured with 2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)hexane. The curing characteristics, morphology, thermal behaviors, mechanical properties at different temperatures, radiation resistance, and thermal aging resistance of the MESR/MPSR blends were investigated. The results show that a high MPSR content could decrease the optimum curing time and improve the scorch safety. Dynamic mechanical analysis revealed that the glass‐transition temperature of the blends increased slightly with the addition of MPSR. Scanning electron microscopy showed that MESR and MPSR had good compatibility in the blends. Thermogravimetric analysis indicated that the thermal stability of the blends increased with increasing quantity of MPSR. The blends had excellent mechanical properties at low temperatures. However, these properties were significantly reduced when the temperature was increased. Moreover, changes in the mechanical properties decreased with increasing MPSR content at high temperatures, especially at temperatures higher than 100°C. In addition, the radiation resistance and thermal aging resistance of the blends increased with increasing MPSR content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40529.     

2,5-二甲基-2,5-二叔丁基过氧化己烷对混炼型聚氨酯橡胶性能的影响

研究了2,5-二甲基-2,5-二叔丁基过氧化己烷(简称双-2,5)对混炼型聚氨酯橡胶的综合性能的影响,并与硫黄硫化的聚氨酯橡胶的性能进行比较。结果表明,添加过氧化物双-2,5的混炼型聚氨酯橡胶的硫化时间较短,扭矩值较高。与硫黄硫化体系相比,以双-2,5为硫化剂时,硫化胶的物理机械性能较低,但可以明显减少聚氨酯橡胶的高温压缩永久变形,且玻璃化温度较低。增加双-2,5的用量,硫化胶的耐油性能得到提高。     

A study of dynamic vulcanization for polyamide‐12 and chlorobutyl rubber

Polyamide‐12 and chlorobutyl rubber were blended by dynamic vulcanization in a high shear environment using curing systems based on sulfur, dithiocarbamate/ZnO, and 4,4‐methylenebiscyclohexylamine/MgO. As expected, all blends with curing agents show increased tensile strength and elongation at break in comparison to blends without curing agents. Maximum mechanical properties are obtained at relatively low levels of curing agent in all systems. Hexane extraction of the mixtures and measurement of percentage of insolubles along with the swelling index of the rubber phase confirm that a high level of cure is achieved at low levels of curing agent. Although the curatives are designed for the rubber phase, differential scanning calorimetry results indicate that both phases are affected during the dynamic vulcanization process, with polyamide‐12 showing a reduced melting temperature that is indicative of molecular weight reduction, structure changes, or reaction with the rubber phase. Scanning electron microscopy results indicate that phase size is reduced with increased blending time and level of curing agent. Rheological studies indicate that blends containing curing agents exhibit non‐Newtonian behavior to a greater extent than polyamide or nonvulcanized polyamide/chlorobutyl rubber blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 871–880, 2003     

Thermally stable bromobutyl rubber with a high crosslinking density based on a 4,4′‐bismaleimidodiphenylmethane curing agent

The development of thermally stable bromobutyl rubbers has been a challenge in rubber chemistry and engineering. In this circumstance, 4,4′‐bismaleimidodiphenylmethane (BMI) was newly applied as a novel crosslinking agent for thermally stable brominated isobutylene–isoprene rubber (BIIR) with a high crosslinking density. With oscillating disk rheometry and differential scanning calorimetry, the curing characteristics of BIIR were systematically investigated with respect to the content of BMI. We found that BMI alone could crosslink BIIR at higher temperature, and a corresponding possible chemical reaction mechanism was proposed. With the introduction of zinc oxide, the curing reaction of BIIR with BMI was significantly accelerated, and the resulting vulcanizate provided a higher state of curing with excellent overcure reversion stability even at a temperature of 190 °C for 2 h. The content of the dicumyl peroxide (DCP) reaction accelerator was also optimized to be BMI/DCP = 1:0.05 on the basis of considerations of the curing rate, scorch safety, maximum rheometric torque, and reversion resistance at 160 °C. Compared with the conventional sulfur‐cured BIIR, the BMI‐cured BIIR exhibited a higher crosslinking density with a superior low compression set property at elevated temperatures and an excellent thermal stability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44092.     

Preparation and characterization of polymethyltrifluoropropylsilicone modified acrylonitrile–butadiene rubber/fluorosilicon rubber blend

The blending of polymethyltrifluoropropylsilicone‐modified acrylonitrile–butadiene rubber (MNBR) and fluorosilicon rubber (FSR) at 70 : 30 ratio was investigated. The grafting of mercapto‐functionalized polymethyltrifluoropropylsilicone onto acrylonitrile‐butadiene rubber (NBR) by thiol‐ene reaction was carried out with 2,2′‐azobisisobutyronitrile as initiator in a Haake torque rheometer. The rheological properties of NBR grafting obtained at varying dosages of polymethyltrifluoropropylsilicone in a Haake torque rheometer were studied using torque curves. Grafting reaction was confirmed by ¹H nuclear magnetic resonance and energy‐dispersive X‐ray spectroscopy. Results of scanning electron microscopy and dynamic mechanical analysis showed better compatibility of MNBR/FSR blend than NBR/FSR reference blend. Meanwhile, the macro‐mechanical properties of the blend significantly improved. The tensile strength and tear strength of MNBR/FSR blend were improved to 14.34 MPa and 44.94 KN/m, respectively, which were 2.92 MPa and 13.03 KN/m higher than those of NBR/FSR reference blend. The low‐temperature brittleness of the blend was improved to ?57°C, an increase of ?6°C compared with that of NBR. These results indicated that MNBR/FSR blend at 70 : 30 ratio had improved compatibility because of the grafting chains that acted as interfacial agents. The low‐temperature resistance of the blend was also enhanced. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42328.     

Mechanical properties,flame retardancy,hot‐air ageing,and hot‐oil ageing resistance of ethylene‐vinyl acetate rubber/hydrogenated nitrile‐butadiene rubber/magnesium hydroxide composites

The mechanical properties, flame retardancy, hot‐air ageing, and hot‐oil ageing resistance of ethylene‐vinyl acetate rubber (EVM)/hydrogenated nitrile‐butadiene rubber (HNBR)/magnesium hydroxide (MH) composites were studied. With increasing HNBR fraction, elongation at break and tear strength of the EVM/HNBR/MH composites increased, whereas the limited oxygen index and Shore A hardness decreased slightly. Hot‐air ageing resistance and hot‐oil ageing resistance of the composites became better with increasing HNBR fraction. Thermal gravimetric analysis results demonstrated that the presence of MH and low HNBR fraction could improve the thermal stability of the composites. Differential scanning calorimeter revealed that the glass transition temperature (T_g) of the composites shifted toward low temperatures with increasing HNBR fraction, which was also confirmed by dynamic mechanical thermal analysis. Atomic force microscope images showed MH has a small particle size and good dispersion in the composites with high HNBR fraction. The flame retardancy, extremely good hot‐oil ageing, and hot‐air ageing resistance combined with good mechanical properties performance in a wide temperature range (?30°C to 150°C) make the EVM/HNBR/MH composites ideal for cables application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

动态硫化NBR/CPE/EVA热塑性弹性体的研制

为了获得一种耐热油，弹性好，强度高，橡胶感强，易加工的油封材料，我们采用动态硫化法制备了共混型NBR／CPE／EVA热塑性弹性体，系统讨论了橡塑并用比，硫化温度和硫化时间对热塑性弹性体的凝胶含量及力学性能的影响。结果表明：在一定温度和时间范围内，硫化温度升高和硫化时间延长，热塑性弹性体的凝胶含量增大，随着热塑性弹性体中EVA用量增大，弹性体的拉伸强度，赵氏硬度和拉伸永久变形有增大。     

聚硫橡胶增韧环氧树脂模具材料的研究

以液态聚硫橡胶为增韧剂,低分子量聚酰胺为固化剂,制备聚硫橡胶/环氧树脂快速模具材料。以冲击强度、压缩强度和固化时间为考核指标,通过正交设计优化了固化温度、聚硫橡胶的加入量、固化剂的加入量和石墨用量等参数。结果表明:固化温度、固化剂用量对环氧固化物的冲击强度、压缩强度和固化时间的影响十分显著,液态聚硫橡胶明显改善了环氧树脂快速模具材料的力学性能,而石墨对其影响较小。综合冲击性能、压缩性能和固化时间三项指标,确定了环氧树脂模具材料的最佳制备条件为:固化温度70℃,聚硫橡胶加入量25%,固化剂加入量100%,石墨加入量30%。     

白炭黑/炭黑混合填料对氟橡胶/硅橡胶共混胶性能的影响

采用沉淀白炭黑和高耐磨炭黑作为氟橡胶/硅橡胶共混胶的填料.研究以不同质量比混合的沉淀白炭黑和高耐磨炭黑对氟橡胶/硅橡胶共混胶的硫化特性、门尼粘度、力学性能、耐热老化性能和耐油性能的影响,并通过RPA分析表征填料-填料的相互作用,采用SEM表征白炭黑/炭黑混合填料在氟橡胶/硅橡胶共混胶中的分散性.结果表明,随着混合填料中白炭黑所占比例的增大,氟橡胶/硅橡胶共混胶的硫化转矩升高,焦烧时间(t10)缩短,正硫化时间(t90)延长,门尼粘度增大.氟橡胶/硅橡胶共混胶的力学性能,耐热老化性能和耐油性能都随着混合填料中白炭黑用量增多而提高.RPA分析表明,全部采用白炭黑补强的共混胶Payne效应最明显,炭黑补强的共混胶Payne效应最弱.SEM分析表明,白炭黑在共混胶中分布比炭黑更加均匀,填料聚集体粒径较小.     

BIPB硫化氢化丁腈橡胶性能的研究

研究了双叔丁基过氧化异丙基苯(BIPB) 硫化剂用量对氢化丁腈橡胶混炼胶硫化特性及硫化胶力学性能、耐热性能、耐油性能及压缩永久变形性能的影响。结果表明：随着BIPB用量的增加,混炼胶的焦烧时间t10和正硫化时间t90均逐渐减小,交联效率提高;硫化胶的物理机械性能、耐热性能、耐油性能和压缩永久变形性能均逐渐提高。当BIPB用量为4份时,硫化胶的综合性能达到最优。     

Effect of organoclay and silver‐substituted zeolite on the mechanical and antibacterial properties of a silicone rubber filled with 2‐hydroxypropyl‐3‐piperazinyl‐quinoline carboxylic acid methacrylate

Silicone rubber compounds filled with different loadings of organoclay (OC) and silver substituted zeolite (SSZ) solid fillers were prepared and cured with 2,5‐dimethyl‐2,5‐di(tert‐butylperoxy) hexane. The rubber vulcanizates contained an antimicrobial agent to protect them against Escherichia coli (E. coli ATCC 25922) and Staphylococcus aureus (S. aureus ATCC 25923) bacteria. The tensile strength, elongation at break, stored energy density at break, Young's modulus, modulus at 100% elongation, cyclic fatigue life, and glass transition temperature of the rubber vulcanizates were subsequently measured. The antimicrobial performance of the rubber surfaces were determined by disk diffusion testing and plate count agar method. The antimicrobial agent had an adverse effect on the mechanical properties, but the cyclic fatigue life of the rubber vulcanizate improved. The addition of OC and SSZ could improve the tensile strength, elongation at break and stored energy density at break, but deteriorated the tear energy, Young's modulus and modulus at 100% elongation. The inclusion of the fillers was not beneficial to the antimicrobial activity of the rubber against bacteria. The HPQM in the rubber was effective more against E. coli. than against S. aureus. Furthermore, the antimicrobial activity increased when the contact time in the test solution was increased. POLYM. ENG. SCI., 54:932–941, 2014. © 2013 Society of Plastics Engineers     

硫化剂对硅橡胶性能的影响

考察硫化剂TX-29、双2,5、双2,4和DCP对硅橡胶硫化特性和物理性能的影响。试验结果表明:采用硫化剂DCP的硅橡胶的综合物理性能最佳;可根据生产工艺、成本和性能要求,选用不同的硫化剂来实现产品性能目标。     

Effect of curing temperature on the morphology of unsaturated polyester resin blended with poly(vinyl acetate)

Phase separation of unsaturated polyester/styrene (UPE/styrene) resin blended with 5 and 10 wt% of poly(vinyl acetate) (PVAc) cured at various temperatures ranging from 75°C to 150°C was studied using low angle laser light scattering (LALS) and scanning electron microscopy (SEM). For UPE/styrene resin blended with 5 wt% PVAc cured at a temperature below 90°C, a discrete phase‐separated structure was observed. As curing temperature was raised above 90°C, SEM micrographs revealed that more and more cured UPE globules fused together with increasing curing temperature. The LALS intensity profile became broader with increasing curing temperature, indicating a less discrete phase‐separated structure at a higher curing temperature. As PVAc content was increased to 10 wt%, SEM micrographs revealed a co‐continuous phase‐separated structure. The LALS intensity decayed slowly from the center of the scattering pattern to a high scattering angle without the appearance of maximum scattering peak intensity. The morphology of the cured sample did not change too much with curing temperature for UPE/styrene resin blended with 10 wt% of PVAc.     

An effect of OMMT on the anti‐reversion in NR/CR blend system

The influence of dispersed organomodified montmorillonite (OMMT) on curing behaviors of natural rubber (NR)/chloroprene rubber (CR) blend was investigated. The preparing procedure includes premixed rubber individually with its additives and then the two components were blended according to gum weight ratio for NR to CR is 75/25. Sulfur was chosen as the vulcanizing agent, and the research on vulcanization was carried through the rotor‐Rheometer at 143°C. Transmission electron microscopy showed the dispersion of OMMT in the rubber blends and detected little OMMT migrated into the NR phase. The scorch time (t₁₀), optimum vulcanizing time (t₉₀), and reversion phenomenon were both measured by the curing curve; meanwhile, the crosslinking densities and mechanical properties were determined through equilibrium swelling‐method, magnetic resonance crosslink density spectrometer, and tensile tests. By comparing the test results, an interesting phenomenon was discovered and furthermore was verified that the addition of OMMT can obviously modify the reversion resistance of the binary blend. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

硫化剂对陶瓷化耐火硅橡胶性能的影响

研究了2,5-二甲基-2,5-二（叔丁基过氧基）己烷（俗称双二五）、2,4-二氯过氧化苯甲酰（俗称双二四）、过氧化二异丙苯（DCP）3种硫化剂对陶瓷化耐火硅橡胶力学性能和烧结性能的影响。结果表明,一次硫化和二次硫化后,使用DCP做硫化剂的硅橡胶的硬度都是最大,使用双二五做硫化剂的硅橡胶的拉断伸长率都是最高,采用双二四做硫化剂的硅橡胶拉伸强度都是最大;使用双二四做硫化剂的硅橡胶烧结硬度最高。综合来看,使用双二四作硫化剂时陶瓷化耐火硅橡胶的力学性能最好,其最佳用量为1.25份。     

Effect of plasticizer and curing system on freezing resistance of rubbers

At glass transition temperature, T_g the rubber compound becomes stiff and brittle and it loses all its rubbery characteristics. This article deals with the changes in T_g of rubber blends based on natural rubber and polybutadiene rubber of varying vinyl content having different types and content of plasticizers, different curing systems and its effect on physico‐mechanical properties to improve its freezing resistance. The plasticizers used were dioctylphthalate (DOP), tricrecylphosphate (TCP), dioctyladipate (DOA), and oil type plasticizers like parafinic oil (P#2) and aromatic oil (A#2). Among the plasticizers, when DOP and DOA content was high, an appreciable decrease of T_g was found compared to TCP. Moreover, there was a remarkable decrease of T_g using DOA plasticizer, which shows more effective on freezing resistance. However, there was not much change in T_g with oil‐type plasticizers with high oil content compared to TCP plasticizer. The effect of cross‐linking systems such as conventional sulfur vulcanization (CV), efficient sulfur vulcanization (EV), and dicumyl peroxide (DCP) and rubber blends with varying vinyl content in polybutadiene rubber were also carried out. It was found that T_g in different cross‐linking system decreased in this order: CV < EV < DCP. It reveals that DCP cross‐linking system affect more for improving freezing resistance. Physico‐mechanical properties such as tensile strength, tear strength, hardness were also measured. The ratio of initial slope (M₀) to steady‐state slope (M₁), M₀/M₁ in tensile curves of different blends were verified, which in turn related to the physico‐mechanical properties and freezing resistance of rubber compounds. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39795.     

EVM橡胶过氧化物交联体系的研究

研究了交联剂过氧化二异丙苯(DCP)、双叔丁基过氧异丙基苯(BIPB)、2,5-二甲基-双(叔丁基过氧基)己烷(DBPMH)以及助交联剂三烯丙基异氰脲酸酯(TAIC)、三烯丙基氰脲酸酯(TAC)、N,N′-间苯撑双马来酰亚胺(HVA-2)对乙烯-醋酸乙烯酯橡胶(EVM)硫化特性、交联密度以及力学性能的影响。通过测试硫化曲线、力学性能和交联密度还研究了无机阻燃填料氢氧化镁的隔离效应对EVM橡胶交联效率的影响。结果表明,EVM橡胶最优过氧化物交联体系为BIPB和TAIC,其最佳配比为2.3/2.5,此时EVM橡胶有较好交联效率、交联速率和力学性能。氢氧化镁对EVM橡胶的交联效率没有影响,但硅烷化氢氧化镁能够提高EVM橡胶的表观交联密度。使用高交联效率过氧化物交联体系BIPB和TAIC,并添加硅烷化氢氧化镁,可平衡EVM橡胶阻燃性能和力学性能。     

Structural evolution of recycled tire rubber in asphalt

The performance of recycled‐tire‐rubber‐modified asphalt mainly depends on the structure of rubber in the asphalt. The effects of the curing temperature, mixing time, and shearing on the evolution of the chemical structure and morphological structure of crumb rubber in asphalt were investigated. The crosslink density, compositions, and morphological evolution of the residual crumb rubber were characterized. The results show that the structure evolution of tire rubber in asphalt was greatly affected by the curing temperature. At a low curing temperature (180°C), the crosslinking network of the tire rubber was broken down, and this led to the partial dissolution of natural rubber (NR). However, at high curing temperature (240°C), the dissolution of NR, synthetic rubber, carbon black, and inorganic filler was observed. The released carbon black covered with a thin layer of bound rubber dispersed at a microstructured or nanostructured size in the asphalt. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42954.