乙烯基含量对热硫化硅橡胶抗撕裂性能的影响

研究不同乙烯基含量对热硫化硅橡胶的力学性能尤其是抗撕裂性能的影响,采用平衡溶胀法测定硅橡胶的交联密度,研究不同乙烯基含量的硅橡胶并用胶的撕裂强度和交联密度的关系。结果表明,随着硅橡胶乙烯基含量的增大,硅橡胶硫化胶的断裂伸长率减小,300%定伸应力和硬度升高,当乙烯基摩尔分数为0.15%时,撕裂强度和拉伸强度较高。乙烯基摩尔分数为0.15%的硅橡胶和乙烯基摩尔分数为0.06%的硅橡胶并用,当并用比为50/50时,撕裂强度高达45.8 kN/m,乙烯基摩尔分数为0.30%的硅橡胶和乙烯基摩尔分数为0.06%的硅橡胶并用,当并用比为4/96时,撕裂强度可达42.9kN/m。乙烯基摩尔分数为0.30%的硅橡胶和乙烯基摩尔分数为0.15%的硅橡胶并用,并用比对硫化胶的撕裂强度影响不大。高乙烯基含量和低乙烯基含量的硅橡胶并用,有利于使硅橡胶的交联结构由"分散交联"转变为"集中交联",当并用胶的乙烯基摩尔分数在0.15%以内,硅橡胶并用胶的撕裂强度随乙烯基摩尔分数的增加而先增大后降低,而此时并用胶的交联密度与撕裂强度成反比。     

老化对NR硫化胶的影响

研究了热空气老化和真空老化对ＮＲ硫化胶结构和性能的影响,采用化学探测剂脱硫的方法测定了老化过程中ＮＲ硫化胶交联密度及交联键分布变化的情况,同时测定了硫化胶的力学性能和动态性能随时间变化的情况。结果显示,热空气老化使硫化胶的交联密度增加,但力学性能损失严重,原因是主链氧化断裂。真空老化使ＮＲ硫化胶交联密度略微降低,但力学性能保持良好,类似于硫化返原。热空气老化使ＮＲ硫化胶的动态性能改善,而真空老化后     

硅烷含硫原子数对NR硫化胶性能的影响

研究了Ｓｉ６９系列的硅烷偶联剂对ＮＲ胶料力学性能和耐磨性能的影响。试验结果表明,硫原子数影响力学性能和耐磨性,但基本上不影响它们随硫化时间下降的趋势。另外,硫原子数对力学性能和耐磨性、以及耐磨性随硫化时间下降趋势的效应填充体系（炭黑、炭黑、／白炭黑）而异。     

马来酸酐化液体聚丁二烯对天然橡胶/芳纶短纤维复合材料性能的影响

研究马来酸酐化液体聚丁二烯(MLPB)对芳纶短纤维(SAF)补强天然橡胶(NR)复合材料性能的影响。结果表明:SAF和炭黑对NR的补强有协同作用,加入相容剂MLPB提高了橡胶基体与纤维的界面粘合性能,复合材料静态和动态力学性能明显提高;随着MLPB用量的增大,复合材料100%定伸应力增大,拉伸强度、拉断伸长率和撕裂强度在MLPB用量为4.5份时达到最大值。     

硫化返原对NR硫化胶结构与性能的影响

研究了硫化返原对NR硫化胶的结构和性能的影响。采用化学探测剂脱硫的方法,测定了硫化返原过程中NR的交联密度和交联键分的变化情况,结果证实了硫化返原的机理;测定了不同温度下随着硫化时间的延长NR力学性能的变化规律以及在硫化期和返原期的动态性能。结果表明,动态生热引起返原,反过来返原导致损耗模量增大,这是轮胎破坏的重要原因。     

炭黑表面活性对填充NR硫化胶性能的影响

先将同一批次中超耐磨炭黑N234进行脱灰、脱挥发分处理,再在高温(500℃、1000℃和1500℃)氮气氛围下分别处理1h和6h,制备出具有不同表面活性的炭黑填料;采用同一配方和工艺制备出硫化胶,研究了不同表面活性的炭黑填料对硫化胶补强性能的影响。结果表明,随着处理温度的升高,炭黑粒子表面能升高,分散性变差,结合胶含量降低,拉伸强度变化不大;与1#未高温处理炭黑填充硫化胶相比,1500℃×1h条件下处理的炭黑填充硫化胶拉断伸长率、相对磨耗量和压缩生热分别增大了25%、33%和147%,定伸应力下降了51%,滞后损失变化不大。延长高温处理时间,炭黑表面活性降低,分散性变好,结合胶含量增大。     

马来酸酐预处理炭黑对硫化天然橡胶动态力学性能的影响

用DMA研究了马来酸预处理炭黑对硫化天然橡胶动态力学性能的影响,结果表明,马来酸酐预处理炭黑有利于降代天然橡胶的滚动阻力。     

硫化体系对SBR/NR并用胶性能的影响

研究硫化体系对丁苯橡胶(SBR)/天然橡胶(NR)并用胶性能的影响。结果表明:当硫化体系的总有效硫质量份为0.86时,在硫化剂S-80用量为0.8份、促进剂TMTD用量为0.4份、硫化剂DTDM-80用量为1.5份时,并用胶的综合性能最佳,适用于大多数橡胶制品的生产;在促进剂TMTD的用量为0.4份时,硫化剂S-80和DTDM-80的配比对并用胶的物理性能和耐热老化性能均有很大影响,通过调整硫化剂S-80和DTDM-80的用量,可以得到适用于不同场合的、综合性能优异的SBR/NR并用胶。     

预硫化时间对MFIIR／NR并用胶性能的影响

采用预硫化工艺,制备了MFIIR／NR并用胶。研究了预硫化时间和温度对并用胶硫化特性、力学性能和拉伸断面形貌的影响。结果表明,随着预硫化时间的延长,并用胶的焦烧时间和正硫化时间延长,拉伸强度呈先增加后减少的趋势,最大达到10．60MPa（大于传统工艺的4．46MPa）,但并用胶的拉伸断面具有较高致密程度,出现明显的脊状线和均匀的外观;不同预硫化温度下,并用胶的最佳力学性能基本相同。     

MLPB在橡胶改性中的应用初探

简要介绍了马来酸酐化聚丁二烯(MLPB)在软木填充丁腈橡胶制品和丁基橡胶配方改性中的应用效果。研究表明,MLPB能在一定程度上提高有机填料与橡胶基体之间的界面结合强度；同时，也能有效地提高IIR胶料的自粘性能和撕裂强度等性能指标。     

环保型促进剂二苄基二硫代氨基甲酸锌对天然胶乳硫化胶膜性能的影响

选择二苄基二硫代氨基甲酸锌(ZBDC)、二异丙基黄原聚硫、二硫化四苄基秋兰姆作为天然胶乳(NRL)的硫化促进剂,采用正交试验确定了NBL的硫化配方及最佳工艺,对比了促进剂ZBDC及传统促进剂二乙基二硫代氨基甲酸锌(ZDC)对NRL硫化胶膜性能的影响,考察了贮存时间对NRL硫化程度及硫化NRL黏度、机械稳定性的影响。结果表明,硫化NRL的最佳配方及工艺:促进剂ZBDC、硫黄、氧化锌用量分别为0.75,1.25,0.50份,硫化温度为70℃,硫化时间为2.5 h;随着促进剂ZBDC用量的增加,NRL硫化胶膜的交联密度逐渐增大,而300%定伸应力、500%定伸应力、700%定伸应力、拉伸强度均呈现先增大后减小的趋势;当促进剂ZBDC与ZDC并用时,硫化胶膜的300%定伸应力、500%定伸应力、700%定伸应力和交联密度都达到了最大值,但拉伸强度和撕裂强度比采用最优方案制得硫化胶膜小;随着促进剂ZBDC用量的增加,NRL硫化胶膜的耐老化性能先提高后又下降;无论ZDC与ZBDC并用还是单独使用,硫化胶膜的耐老化性能都较优;随着贮存时间的延长,无论是使用环保型促进剂ZBDC还是使用促进剂ZDC,NRL的硫化程度均增加,硫化NRL的黏度均逐渐增大,而机械稳定性先稍有提高后下降。     

增塑剂对硅橡胶硫化胶性能的影响

在确定硅橡胶基本配方的前提下，分析了增塑荆对硅橡胶硫化胶性能的影响。研究结果表明，试验中选用的酯类增塑剂和醇类增塑荆均能明显降低硅橡胶硫化胶的模量，但采用自制的环氧改性胶粘荆进行硅橡胶硫化胶与金属粘接时，含酯类增塑荆的硫化胶粘接效果较好。试样破坏形式为橡胶内聚破坏；而采用醇类增塑剂的硫化胶。粘接质量较差。试样破坏形式均为粘接面破坏。     

Inhibited oxidation of vulcanized natural rubber

Rates of oxidation in oxygen at 140°C. of natural rubber gum vulcanizates containing PBNA as inhibitor have been compared. They are a function of sulfur combined with the rubber, and only slightly affected by curing system for sulfur alone, TMTD sulfurless, and very high-efficiency sulfenamide plus dithiocarbamate-accelerated compositions. Addition of diphenylguanidine to simple sulfur vulcanizates causes much faster oxidation. No conclusions about oxidation mechanism can be drawn from rates of oxidation alone.     

Viscoelastic and thermoelastic properties of general purpose commercial vulcanized natural rubber

Viscoelastic and thermoelastic properties of general purpose vulcanized natural rubber were investigated focusing attention on its nonideal or irreversible natures. The master curve is not composed by simple horizontal shift of stress–relaxation curves at various temperatures by the time–temperature superposition principle. In order to compose a smooth master curve, both horizontal and vertical shifts are necessary. The relative stress–time relation elucidates the fact that the stress–relaxation mechanism is caused by the chemical scission by oxidation occurring in the network system. The value of vertical shift increases with increasing temperature or strain. This phenomenon has the same meaning as the one derived from the relative stress–time relation. The activation energies are calculated using the horizontal shift factors determined empirically. The result suggests the existence of two concurrent relaxation mechanisms with different activation energies. From the stress–temperature relation at any given strain, energetic and entropic components of the stress–strain curve are obtained. The energetic component is very significant as compared with the case of ideal crosslinked natural rubber. This phenomenon is considered to be caused by the internal friction and/or chemical scission of bonds in the system associated with the deformation process of sample.     

Uniaxial ratchetting behavior of vulcanized natural rubber

Most of rubber engineering components endure cyclic loading during their service, and a nonzero mean stress during cyclic loading may cause an accumulation of strain which is known as ratchetting phenomenon. In order to study the ratcheting effect of rubber, a series of uniaxial ratchetting experiments were conducted on vulcanized natural rubber (NR). The effects of cyclic stress amplitude, mean stress and their histories on ratchetting behavior were studied, respectively. The uniaxial ratchetting behavior of natural rubber depends greatly on the stress amplitude and mean stress. The ratchetting strain rate greatly increases with the stress amplitude or mean stress increased. Experimental results reveal that the rubber material exhibits a strong memory of the previous high loading history, and such memory plays a significant role on the subsequent ratchetting. The ratchetting behaviors of the rubber exhibit little sensitive to the applied cyclic stress rate except for the initial strain. POLYM. ENG. SCI., 48:191–197, 2008. © 2007 Society of Plastics Engineers     

Effect of MAH modified carbon black on dynamic mechanical properties of vulcanized natural rubber

用DMA研究了马来酸酐预处理炭黑对硫化天然橡胶动态力学性能的影响。结果表明,马来酸酐预处理炭黑有利于降低天然橡胶的滚动阻力。     

高强度双组分室温硫化硅橡胶的

用钛酸酯和硅烷偶联剂KH－550合成了一种TH偶联剂。研究了偶联剂、活性高分子材料、促进剂和填料的各类和加入量对双组分硅橡胶性能的影响。结果表明,TH偶联剂双KH－550改性效果好。端痉基聚氨酯予聚物,106硅橡胶和TH偶联剂共同对107硅橡胶进行改性,可明显提高其粘接强度。例如,对铝的剪切强度可由1MPa左右提高到4MPa以上。     

Experimental study on multiaxial ratcheting behavior of vulcanized natural rubber

Multiaxial ratcheting characteristics of vulcanized natural rubber (NR) at room temperature were studied experimentally. The effects of axial stress, shear strain amplitude, shear strain rate, and their histories on ratcheting behavior were discussed. It is shown that the ratcheting strain depends on the axial stress and cyclic strain range. The ratcheting strain increases more rapidly as the constant axial stress or shear strain amplitude become larger. The ratcheting behaviors of the rubber exhibit nonsensitivity to the applied cyclic stress rate except initial axial strain. Furthermore, the loading histories also play an important role in progress of ratcheting. The prior cycles with higher axial stress, larger strain range or lower strain rate greatly restrains ratcheting strain of subsequent cycling with lower ones. Influence of creep on ratcheting behavior can not be neglected and its value reaches 87% of ratcheting strain. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers