Blending of Natural Rubber/Recycled Ethylene-Propylene-diene Rubber: Promoting the Interfacial Adhesion Between Phases by Natural Rubber Latex

This article deals with blends based on natural rubber (NR) and recycled ethylene-propylene-diene rubber (R-EPDM). Natural rubber latex (NRL) was introduced into the blends to enhance interfacial adhesion between NR and R-EPDM. A new route of compounding was also suggested. The blends were prepared by mixing R-EPDM and other additives in NRL before blending with natural rubber on a two-roll mill. By applying this method, the homogeneity of the blends and cross-linking distribution are significantly improved. The blends exhibited superior state of cure, swelling resistance, mechanical properties and dynamic mechanical properties. The degree of entanglement between NR and R-EPDM also increased after NRL modification.     

Addition of Transition Metals to Improve Physico-Mechanical Properties of Radiation-Vulcanized Natural Rubber Latex Films

The effect of transition metals as a promoter of physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of transition metals (Fe, Mn, etc.) of different concentrations (0–30 ppm) in natural rubber (NR) latex and irradiated with various radiation doses (0–20 kGy). The concentrations of metal ions and radiation doses were optimized and found to be 20 ppm and 12 kGy, respectively. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films were increased with increasing concentration of metal ions as well as radiation doses. The mechanical properties of the films were enhanced by approximately 20% at the optimum conditions. In contrast, elongation at break, permanent set, and swelling ratio of the films were decreased under the same conditions. The comparative effect of metal ions can be explained by Fajan's rules, reported in this article.     

Radiation Vulcanization of Nitrile Butadiene Rubber/Butadiene Rubber Blends

Blends of nitrile butadiene rubber (NBR) with butadiene rubber (BR) with varying ratios have been prepared. Vulcanization of prepared blends has been induced by ionizing radiation of gamma rays with varying dose up to 250 kGy. Physical properties, namely soluble fraction and swelling number have been followed up using toluene as a solvent. Mechanical properties, namely tensile strength, tensile modulus at 100% elongation and elongation at break have been followed up as a function of irradiation dose, as well as blend composition. Thermal stability of blends was studied by TGA. The result indicated that the addition of NBR has improved the properties of NBR/BR blends. Also, NBR/BR blend is thermally stable than BR alone.     

环氧化天然橡胶的研究进展

天然橡胶(NR)作为一种植物合成的可再生资源,与由石油生产的合成橡胶相比,更能满足当今世界普遍追求可持续发展的需要。NR的环氧化改性具有操作简单、方法经济、反应可在水相中进行的特点,制备得到的环氧化天然橡胶(ENR)具有良好的相容性、抗湿滑性、低的滚动阻力、耐油性和气密性等特点,在轮胎工业、胶粘剂和新型复合材料等领域中有着广泛的应用前景。本文对近年来ENR制备和表征方法、ENR与白炭黑之间的相互作用、ENR的硫化及其在轮胎胶料中的应用等方面的最新进展进行了综述,并对今后的研究方向提出了建议。     

天然橡胶/石墨烯纳米复合材料的制备及耐核辐射性能

采用乳液共混和原位还原法制备了天然橡胶(NR)/还原氧化石墨烯(RGO)纳米复合材料,研究了γ射线辐照对复合材料力学性能和热稳定性的影响.研究结果表明,RGO以少数几层堆叠片层结构均匀分散于NR基体中.RGO的加入可显著提高NR的力学性能和热稳定性,加入质量分数为0.6%的RGO可使材料拉伸强度由(22±1.4)MPa提升至(25±1.1)MPa,质量损失50%对应的温度(T50)升高6.4℃.经200 k Gy的γ射线辐射后,纯NR的拉伸强度和T50分别下降了75%和4.5℃,而NR/RGO-0.6%复合体系仅分别下降了56%和1.2℃.揭示了RGO提高材料耐辐射性能的机理,由于RGO可捕捉猝灭因辐射产生的自由基,从而减弱了辐射老化降解和交联反应的发生.     

Effect of Ground Rubber Powder on Properties of Natural Rubber

Ground rubber powder (GRP) with three different sizes was incorporated into nature rubber matrix with different loading. Cure characteristics, swelling behaviour, crosslink density, tensile fractured surface, and mechanical properties have been studied. Based on the cure characteristics, it is evident that the processability of the rubber compounds has not changed obviously with the different GRP loading. The introduction of GRP in virgin rubber leads to the increase in swelling degree and the decrease in crosslink density. Tensile strength, hardness and abrasion resistant deteriorate with the increase of GRP loading, but the tear resistance gets better. If the ground rubber particles are smaller, the properties are more similar to the virgin rubber. Because of the phase separation of the GRP and matrix, the properties get worse with the bigger ground rubber powder.     

丁腈橡胶的配位硫化

在丁腈橡胶中引入无机金属盐粒子,通过腈基与金属离子之间的固相配位反应来实现丁腈橡胶的配位硫化,创建了一个完全不同于传统硫磺硫化体系的新型非共价键配位交联的橡胶网络体系.同时制备了具有优异的力学性能的配位硫化橡胶材料,既可以作柔性的橡胶材料使用,也可以作为韧性、脆性的塑料材料使用.本文就影响配位交联反应的两个关键因素(金属盐粉末的粒径和丁腈橡胶的丙烯腈含量)进行了探讨,提出了提高配位硫化效率的办法(结晶水、增塑剂等).     

硅土/白炭黑复合填料对天然橡胶硫化胶性能的影响

硅土主要是由低温石英和粘土矿物组成的非金属矿物,具有独特的粒片叠置结构。本工作采用经改性处理的硅土与白炭黑并用,测定硅土/白炭黑复合填料对天然橡胶(NR)的硫化特性和力学性能,探讨填料并用对天然橡胶性能的影响。实验结果表明:经改性处理,硅土平均粒径减小,疏水性增强。硅土与白炭黑并用,有利于增强NR硫化初期的流动性,延长焦烧时间而不明显降低硫化速率,能改善橡胶的加工性能。拉伸性能测试结果表明,复合填料与白炭黑或硅土单独使用相比,能显著提高填充NR硫化胶的拉伸强度、定伸应力、交联密度,而不降低橡胶弹性。当硅土占复合填料质量为40%时,NR硫化胶的拉伸强度达到最大。动态机械性能测定结果表明,相比白炭黑,硅土更有利于减小硫化胶的生热和滚动阻力。     

环氧化天然橡胶二次改性的研究进展

环氧化天然橡胶(ENR)分子链中存在易开环的反应性环氧基团,环氧基团的开环反应为ENR进行进一步的改性提供了极大的方便。ENR选择性氢化双键可以提高其抗热氧稳定性;ENR与胺类化合物和含磷化合物的反应,可以将防老剂和阻燃剂负载到ENR分子链上,从而达到在分子尺寸的分散;可以利用环氧基团的选择性氧化裂解制备NR基嵌段共聚物的前驱体遥爪型NR;通过环氧基团可以进行接枝改性其它聚合物;此外,分子链中的环氧基团使ENR与无机填料和其它极性聚合物共混相容性提高。     

Effect of montmorillonite intercalant structure on the cure parameters of natural rubber

Two quaternary phosphonium salts (aromatic and aliphatic) have been used as intercalants for Na-montmorillonite and the effect of intercalant structure on clay morphology and natural rubber vulcanization kinetics was investigated. Due to its lower rigid structure the aliphatic salt was easier to intercalate into the clay galleries giving rise to a higher interlayer distance and facilitating the rubber intercalation obtaining an exfoliated structure in the nanocomposite. The vulcanization process was sensibly accelerated by this organoclay and a higher crosslinking degree was observed in the nanocomposite which gave rise to materials with improved processing and physical characteristics.     

Vulcanization kinetics of graphene/styrene butadiene rubber nanocomposites

This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber （SBR） with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.     

Simultaneous Enhancement of Mechanical and Dynamic Mechanical Properties of Natural Rubber/Recycled Ethylene-Propylene-Diene Rubber Blends by Electron Beam Irradiation

Mechanical and dynamic mechanical properties of natural rubber/recycled ethylene-propylene-diene rubber (NR/R-EPDM) blends were simultanoeusly enhanced by electron beam (EB) irradiation. The cross-linking promoter, trimethylolpropane triacrylate (TMPTA), was also introduced into the blends to induce the cross-linking. By applying EB irradiation, the tensile modulus, hardness, swelling, cross-link density, and storage modulus increased with increase in the irradiation dose; an irradiation dose of 50 kGy was efficient to gain optimum tensile strength. The formation of irradiation-induced cross-links after EB irradiation is a major concern for the enhancement of mechanical, swelling resistance, and dynamic mechanical properties of the blends.     

天然胶乳中蛋白质和磷脂对橡胶分子结构的影响

采用碱性蛋白酶和磷脂酶处理天然胶乳,制备脱蛋白胶乳和脱脂胶乳,结合原子吸收光谱仪、核磁共振交联密度仪、凝胶色谱(GPC)等仪器对处理前后的天然胶乳进行了分析。通过对比分析,发现酶处理后胶乳分子量降低,分子量分布变宽,金属离子浓度、凝胶含量和交联密度均降低。结果表明,金属离子与天然橡胶中的蛋白质、磷脂间存在着物理的或化学的作用力;蛋白质、磷脂在天然橡胶中起到节点的作用,有利于形成分子间交联,增大天然橡胶分子量,形成分子间网络结构。     

聚氯乙烯表皮成分对加成型硅橡胶固化的影响

采用流变学方法研究了双组分加成型硅橡胶在不同聚氯乙烯(PVC)表皮上的固化动力学,并利用红外光谱、核磁共振波谱、电感耦合等离子体质谱仪等手段分析了PVC表皮成分,以确定导致双组分加成型硅橡胶不固化的具体原因。 结果表明,PVC表皮中导致硅橡胶不固化的主要元素为P元素。 在固定硅橡胶厚度为1 mm的情况下,当PVC表皮中的P元素质量分数低于3×10^-3%时,浇注在其上的双组分加成型硅橡胶依然能固化;而当PVC表皮中的P元素质量分数超过约2.4×10^-2%时,虽然浇注在其上的双组分加成型硅橡胶的中间层依然能固化,但与PVC表皮接触部分的硅橡胶不固化,且不固化层厚度随P元素质量分数增加而增加。 本文还研究了在P元素质量分数低于3×10^-3%的PVC表皮上,降低硅橡胶厚度至微米级时的固化行为,在P元素质量分数低于3×10^-3%的PVC表皮上,当硅橡胶厚度低于2 μm时,硅橡胶出现不完全固化现象。 双组分加成型硅橡胶在含有P元素的PVC表皮表面的固化行为主要是由硅橡胶样品中铂催化剂总含量及PVC表皮中的P元素含量确定的,同时也会受到双组分加成型硅橡胶反应速率以及铂催化剂、P元素在硅橡胶中的扩散速率的影响。     

Thermo-Mechanical Performance of Natural Rubber/Recycled Ethylene-Propylene-Diene Rubber Blends in the Presence of ZnO Nanoparticles

In the present study, recycled ethylene-propylene-diene rubber (R-EPDM) was used in an attempt to create a value-added natural rubber (NR) material based on NR/R-EPDM blends. ZnO nanoparticles were also incorporated in a way to replace the conventional ZnO together with special attention to improve the thermo-mechanical performance of the blends. Polyhedral and spherical shapes of ZnO nanoparticles were synthesized, and they were found to have no impurities, with a dimension ranging from 10 to 40 nm. ZnO nanoparticles not only act as a curing activator but also improve the thermal stability and dynamic mechanical properties of the blends.     

Hydrophilicity Modification of Addition-cured Room Temperature Vulcanization Silicone Rubber

Allyl terminated polyether was used to improve the hydrophilicity of addition-cured room temperature vulcanization silicone rubber. With the increasing of the polyether, both the hydrophilicity and water absorbed of the vulcanizates were increased. The mechanical properties were also improved by adding the polyether. The result showed that 1.5wt% of the polyether provided the silicone rubber with proper hydrophilicity.     

橡胶硫化促进剂的研究进展

作为橡胶加工成形过程中最重要的步骤之一,橡胶硫化直接影响橡胶制品的性能。与单用硫黄相比,少量的促进剂与硫磺配合可以极大地提高硫化速率,改善硫化胶的性能。但目前橡胶硫化促进剂普遍具有潜在的人类健康和环境风险问题,同时硫化促进效能较低、功能单一。因此,开发无毒、无或少氧化锌、高效、多功能的新型硫化促进剂对橡胶工业具有非常重要的意义。本文首先简要介绍了橡胶硫化促进剂的发展历程,然后综述了近年来新型橡胶硫化促进剂的研究进展(包括离子液体促进剂、新型二硫代氨基甲酸盐类促进剂、稀土促进剂、以及含新型副促进剂的硫化并用体系等),并对橡胶硫化促进机理、新型橡胶硫化促进剂的设计进行了展望。     

Studies on the Morphology of Natural Rubber/Polyacrylate Interpenetrating Polymer Networks

The interpenetrating polymer network(IPN) systems have attracted a lot of attention because of their unique two-phase structure and properties. There have been many publications concerning the IPNs in which poly (isoprene) (PIP) or polyacrylates (PAC) is formed as one of the networks.In the present study, Four serles of natural rubber(NR)/PAC IPNs were prepared and their morphologies were investigated with dynamic mechanics analysis(DMA) and transmission electron microscopy (TEM).