Effects of catalyst on the electrical properties of silicone rubber

Electrical properties, such as dissipation factor and electric conductivity, were studied for silicone rubber sheets. The specimens were prepared by the reaction of α,ω-dihydroxypolysiloxane with ethoxysilane, using dibutyltin dilaurate as a catalyst, at a relative humidity of about 100% at various temperatures and for various reaction times. It was found that the electrical properties were a function of the vulcanizing conditions; i.e., the further the vulcanization proceeded, the higher the dissipation factor and the electric conductivity. A reaction describing deterioration in electrical properties was then considered. Infrared spectroscopic studies on dibutyltin dilaurate showed that the dibutyltin dilaurates were partly hydrolyzed to lauric acid and dibutyltin dihydroxide. It was concluded that electrical property deteriorations, which were caused by changes in the vulcanizing conditions, were due to dibutyltin dilaurate hydrolysis. However, since the decomposed products were finally oxidized at elevated temperatures in an oxygen atmosphere, with a subsequent change to electrically inactive compounds, the initial electrical properties were recovered.     

聚酯短纤维含量对其增强橡胶复合材料硫化性能的影响

该文研究聚酯短纤维用量及硫化温度的不同对短纤维橡胶基复合材料（SFRC）硫化特性的影响。结果表明,随着聚酯短纤维用量的增大,复舍材料的Mm呈增加趋势,t90逐渐缩短;随着短纤维含量的增加,硫化平坦性变差,热硫化时间和硫化平坦期很短,此后交联键及链段的热裂解反应剧烈,复合材料性能迅速下降,最大转距和最小转距之差呈上升趋势;随着硫化温度的升高,复合材料的硫化速度加快,焦烧时间缩短,硫化平坦性降低;硫化温度宜选在130℃左右;通过电子扫描显微镜观察,复合材料与短纤维的粘着情况在硫化前后有较大不同,随着纤维用量的增加,纤维和基体的粘着性逐渐降低。     

Effect of iron oxide on the vulcanization and electrical properties of conductive butyl rubber composites

Rubber ceramic composite, negative temperature coefficient of conductivity (NTCC) thermistors, are widely used in industry because of the high dependence of their electrical conductivity on temperature. The effect of iron oxide (Fe₃O₄) on the vulcanization process, DC conductivity, thermoelectric power, dielectric constant and I–V characteristics have been measured. Also the conduction mechanism is discussed. A hot‐pressing technique has been used to enhance the microstructure core of rubber composites. It has been found that Fe₃O₄ acts as a catalyst during vulcanization process and the characteristic time constant during vulcanization decreases as the content of Fe₃O₄ increases. © 2000 Society of Chemical Industry     

NBR／PP共混热塑性弹性体材料的研究

通过分别选择普通氯化聚乙烯(CPE)、高氯化CPE、MP(马来酸酐接枝聚丙烯简称)、复合CPP等对丁腈橡胶/聚丙烯(NBR/PP)共混体系进行增容研究;利用半有效硫化体系以及改性树脂硫化体系对共混体系进行动态全硫化研究;用透射电镜研究部分共混体系的亚微观结构,讨论其与共混体系宏观性能间的关系;利用示差扫描量热分析(DSC)对连续相的结晶形态进行研究。实验研究表明,以CPP为相容剂的共混体系经过动态全硫化后具有优良的耐热油性及其他综合性能。     

Influence of γ-irradiation on proton spin–lattice relaxation of SBR used as antirads and its ESR investigation

Proton spin–lattice relaxation time t₁ was measured on SBR samples with carbon black or kaolin filler using modified linseed oil. The NMR pulse technique at 90MHz was used in the temperature range from 180 to 400 K. The temperature dependence of t₁ indicates that samples filled with carbon black have similar molecular dynamics to the standard unfilled SBR samples. The activation energy for the motion of the main chain for these samples amounts to 16.4kJ/mol. Samples containing linseed oil modified with para-toluidine showed an activation energy of about 14.6kJ/mol and were not affected by γ-irradiation. Values of the minimum relaxation time t^min₁ were increased by γ-irradiation in comparison with a standard SBR sample. ESR measurements carried out at room temperature by means of an X-band spectrometer indicated that unidentified radicals within the rubber were formed during its mastication with vulcanizing additives. The ESR spectra did not change during the vulcanization process. Samples filled with carbon black showed a broadening of the ESR line; this is consistent with the increase in the electrical conductivity.     

提高载重斜交轮胎耐磨性的研究

从配方及硫化工艺角度分析了载重斜交轮胎在实际使用中耐磨性差的原因,认为胎面胶生胶体系采用ＮＲ／ＢＲ／ＳＢＲ三胶并用体系,软化剂采用芳烃油,补强填充剂采用新工艺炭黑Ｎ２３４,加工助剂采用新型加工助剂及通过强化轮胎硫化测温来确定最佳硫化工艺条件可提高载重斜交轮胎耐磨性,试验结果表明,采取这些措施可使９．００～２０ １６ＰＲ载重斜交轮胎总行驶时间和总行驶里程均提高１６．９％,１１．００－２０１８ＰＲ轮胎     

橡胶厚制品硫化

本文对橡胶制品,于硫化时,在两边传热介质温度不同或温度相同的条件下,内部温度場的变化提出了理论计算的方法。 对于复杂橡胶制品,如汽车轮胎在硫化时内部温度場变化的理论计算,虽然各国橡胶学者曾提出过解答方法,但对于轮胎采用逐步升温硫化,即外界热源随时间而变化的计算方法还没有成功。因此,我们假设了一种“综合的”或“相似的”准数,应用板状橡胶制品的导热理论公式来计算,所得结果与实际测得的非常接近。 我们并且制作了图表,简化了计算方法。最后,提出了硫化效应的计算和制订硫化技术条件的方法。     

砷的高效硫化回收技术在污酸处理中应用实践

介绍了大冶有色金属集团股份有限公司冶炼厂净化污酸处理系统的工艺改进、主要设备及运行情况。改进后污酸处理系统先采用硫化处理再采用石灰-铁盐法处理,处理后废水能稳定达标排放或回用,减少了含砷石膏渣的产生量。新增硫化工序主要设备是利用闲置的硫酸净化工序部分设备改造而成,节省了投资成本。     

共聚氯醚橡胶的再生及再生胶硫化体系的配合

研究了机械法再生硫化共聚氯醚橡胶（ECO）薄通次数及辊距对其性能的影响以及ECO再生胶的硫化体系的配合，结果表明通过适当机械再生工艺制造的ECO再生胶是可行的。较好的再生工艺条件为辊距0．4mm和薄通20次。ECO再生胶较好硫化体系配合为：NA-220．4；四氧化三铅4；硫黄0．2。     

复合硫化体系在EPDM胶料中的应用

介绍了一种复合硫化体系（3DCP＋2TE）,采用该复合物体系硫化三元乙丙橡胶（EPDM）胶料时,可以提高其物理性能及耐老化性能,使EPDM具有良好的综合性能。     

二段硫化工艺对铝镀银导电橡胶性能的影响

导电橡胶是一种复合型导电高分子材料,具有导电性好、耐高低温以及柔韧性好、易加工等性能。对硫化工艺对铝镀银导电橡胶导电性能、电磁屏蔽效能和力学性能的影响进行了系统研究。     

In situ dynamic vulcanization process in preparation of electrically conductive PP/EPDM thermoplastic vulcanizate/expanded graphite nanocomposites: Effects of state of cure

In situ melt dynamic vulcanization process has been employed to prepare electrically conductive polypropylene (PP)/ethylene–propylene–diene rubber (EPDM) (40/60 wt %) thermoplastic vulcanizates (TPVs) incorporated by expanded graphite (EG) as a conductive filler. Maleic anhydride grafted PP (PP‐g‐MAH) was used as compatibilizer and a sulfur curing system was designed and incorporated to vulcanize the EPDM phase during mixing process. Developed microstructures were characterized using scanning electron microscopy (SEM), melt rheomechanical spectroscopy (RMS), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) and were correlated with electrical conductivity behavior. For comparison, another class of TPV/EG nanocomposites was fabricated using a commercially available PP/EPDM‐based TPV via both direct and masterbatch melt mixing process. Conductivity of the nanocomposites prepared by in situ showed no significant change during dynamic vulcanization till the mixing torque reached to the stationary level where micro‐morphology of the cured rubber droplets was fully developed, and conductivity abrupt was observed. In situ cured nanocomposites showed higher insulator to conductor transition threshold (3.15 vol % EG) than those based on commercially available TPV. All electrically conductive in situ prepared TPV nanocomposites exhibited reinforced melt elasticity with pseudosolid‐like behavior within low frequency region in dynamic melt rheometry indicating formation of physical networks by both EG nanolayers and crosslinked EPDM droplets. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

环氧型丙烯酸酯橡胶的硫化

通过硫化曲线评定,选用苯甲酸铵作硫化剂环氧丙烯酸酯橡胶低温胶进行硫化。结果表明,共聚单体中甲基丙烯酸缩水甘油酯用量为２％－３％,苯甲酸铵用量为１．５份时,经胶的力学性能最好。二段硫化对硫胶的力学性能几乎无影响。     

硫化体系对动态硫化NBR/PA6热塑性硫化胶性能的影响

采用动态硫化法制备NBR/聚己内酰胺(PA6)热塑性硫化胶(TPV),研究硫化体系对其性能的影响.结果表明:与硫化剂HVA-2/促进剂DM硫化体系相比,采用硫化剂SP-1045/促进剂氯化亚锡硫化体系制备NBR/PA6TPV的加工性能和物理性能较好,且体系中PA6结晶度较小;当硫化剂HVA-2/促进剂DM并用比为1.95/0.49或硫化剂SP-1045/促进剂氯化亚锡并用比为2.6/0.32时,制备NBR/PA6 TPV的NBR分散相粒径较小、分散较均匀和综合物理性能较好.     

NBR/聚丙烯酸酯橡胶共混物动态硫化的研究

ＮＢＲ的溴化酚醛树脂硫化体系和聚丙烯酸酯橡胶（ＡＣＭ）的硫化剂ＡＢＳ会相互干扰，产生硫化不相容性，导致ＮＢＲ，ＡＣＭ和ＮＢＲ／ＡＣＭ共混物性能下降。通过在ＮＢＲ／ＡＣＭ共混物中加入溴化酚醛树脂对ＮＢＲ进行动态硫化，然后加入ＡＢＳ对ＡＣＭ进行静态硫化的方法，能够较好地解决这两种不相容硫化体系的相容性问题，所得到的共混物表现出良好的物理性能，且优于相应的静态硫化共混物。同时考察了ＮＢＲ／ＡＣＭ的共混比对共混物性能的影响。     

硫化钢圈夹具对全钢轮胎硫化胶囊使用寿命的影响

通过力学仿真方法研究硫化钢圈夹具对全钢轮胎硫化胶囊使用寿命的影响。根据轮胎硫化过程中硫化胶囊的受力状态优化钢圈夹具与硫化胶囊的接触面形状后,硫化胶囊使用寿命延长15%~19%,因硫化胶囊裂口引起的废次品率大大降低,提升了轮胎外观质量,同时可减轻劳动强度。     

评价影响丁苯橡胶硫化胶性能的因素

为理解和正确执行丁苯橡胶（ＳＢＲ）１５００系列硫化胶性能评价的国家标准及为修订标准做必要准备，在现有实验室条件下，做了４个方面的工作：一是混炼温度对硫化胶性能的影响。试验表明：混炼温度在５０℃±５℃对硫化速度无明显影响，但随着混炼温度的升高，硫化２５ｍｉｎ的３００％定伸应力有升高趋势；二是硫化室温对硫化胶性能的影响。试验表明，室温对硫化胶影响不明显，但恢复时间Ｔ＿Ｒ的长短会直接影响硫化胶的物性，尤其对硫化２５ｍｉｎ的３００％定伸应力的影响是敏锐的，应引起足够重视；三是硫化时间对硫化胶性能的影响。试验推断Ｔ＿Ｂ的长短对硫化２５ｍｉｎ的３００％定伸应力的影响是举足轻重的，硫化时间（３５±２）ｍｉｎ对硫化胶性能影响不大；四是硫化温度对硫化胶性能的影响。试验指出，在１４５℃±１℃下，硫化２５ｍｉｎ的３００℃定伸应力相差３．３ＭＰａ，在１４５℃±０．５℃下，相差１．７ＭＰａ，由于差异会直接影响产品等级的判定，因此，国际标准规定硫化温度控制在１４５℃±０．５℃是十分必要的。     

橡胶材料硫磺硫化体系低锌/无锌技术研究进展

硫化是决定橡胶是否能够作为材料使用最为重要的步骤。橡胶硫磺硫化体系中,氧化锌的使用不仅可以改善橡胶的硫化性能,并且能够大幅度提高橡胶制品的物理机械性能。但是,由于游离的锌离子易迁移至环境,会对水生生物等产生危害,所以欧盟和美国加州相继颁布法案限制氧化锌的使用。另外,锌矿产资源也日渐枯竭。因此,减少锌元素在橡胶配方中的应用,是保护环境并保证橡胶硫化反应正常进行的热点研究课题。该综述介绍了目前橡胶硫磺硫化体系配方中减少硫化活化剂氧化锌的用量和用非含锌化合物替代氧化锌的研究进展,包括纳米氧化锌、有机锌复合物、无机填料载锌技术、其他金属氧化物和稀土型多功能橡胶硫化剂等新型硫化活化剂的研究现状,并对未来发展方向进行展望。