热氧老化EPR电缆绝缘局部放电特性及劣化机理

为了探究热氧老化后乙丙橡胶电缆绝缘的局部放电特性及劣化机理,文中通过典型柱–板电极对不同老化程度的乙丙橡胶试样进行了局部放电试验,并对其放电发展特性和材料理化性质进行了分析。结果表明:放电起始电压和闪络电压均随绝缘老化程度的提高而降低;根据放电过程中放电特征量的变化规律,可将放电过程划分为4个阶段:起始阶段、发展阶段、持续阶段、预闪络阶段,且不同老化程度试样的PRPD谱图在各阶段呈现出特定形状;老化后的试样表面气化或气体解吸附、内部添加剂成分析出导致试样表面出现"沟壑区"、白色块状物和"微孔",分子结构中的羰基等含氧基团、聚乙烯和聚丙烯等自由基数量的增加是乙丙橡胶绝缘在热氧老化后更易出现局部放电的关键原因。     

Pyrolysis of vulcanized styrene-butadiene rubber via ReaxFF molecular dynamics simulation

Styrene-butadiene rubber (SBR) is widely used in tires in the automotive segment and vulcanization using sulfur is a common process to enhance its mechanical properties. However, the addition of sulfur as the cross-linking agent usually results in impurities in pyrolysis products during rubber recycling, and thus the desulfurization during tire pyrolysis attracts much attention. In this work, the pyrolysis of vulcanized SBR is studied in detail with the help of ReaxFF molecular dynamics simulation. A series of crosslinked SBR models were built with different sulfur contents and densities. The following ReaxFF MD simulations were performed to show products distributions at different pyrolysis conditions. The simulation results show that sulfur products distribution is mainly controlled by sulfur contents and temperatures. The reaction mechanism is proposed based on the analysis of sulfur products conversion pathway, where most sulfur atoms are bonded with hydrocarbon radicals and the rest transfer to H₂S. High sulfur contents tend to the formation of elemental sulfur intermediate, and temperature increase facilitates the release of H₂S.     

丁腈橡胶的发展现状与应用研究进展

综述了国内丁腈橡胶(NBR)的生产能力、产量与市场现状,分析了其国内市场的走向,从国内NBR生产工艺改进、新产品开发和特性化改性及国外丁腈橡胶信息传输应用和氢化丁腈橡胶聚合材料等几个方面介绍了国内外NBR生产技术的最新进展,并提出了我国NBR市场及技术的发展建议。     

丙烯酸酯橡胶耐有机溶剂及耐油性的研究

采用平衡溶胀法测定了日本瑞翁公司生产的活氯型丙烯酸酯橡胶(AR840)在24种不同有机溶剂中的溶胀行为,得到了AR840的一维溶解度参数值,其范围在18~23(MPa)^1/2之间。进一步用汉森三维溶解度参数软件(HSPiP)对溶胀数据进行分析研究,得到AR840三维溶解度参数值,色散分量(δ_d)、极性分量(δ_p)和氢键分量(δ_h)分别为18.20、8.70、3.60(MPa)^1/2。结果表明,AR840与24种溶剂存在着能量差(R_a),AR840与溶剂的溶胀比随着它们之间的Ra值的变化呈现反“S”型曲线,借助Ra的大小可以表征AR840在有机溶剂中的溶胀特性,能相对准确地表征丙烯酸酯橡胶(ACM)耐有机溶剂及耐油性能,对耐有机溶剂及耐油ACM的配方设计有一定的指导意义。     

生物质硅炭增强改性氢化丁腈橡胶的性能及老化规律

以生物质硅炭(Si/CB)取代部分N550炭黑为补强剂、HNBR为基体制备了生物质硅炭改性的HNBR复合材料。研究了硅炭对HNBR的补强行为,高温真空介质中橡胶的热老化行为及主链老化结构的演变。与传统炭黑的增强效果相比,生物质硅炭增强的HNBR表现出更好的韧性、撕裂强度、较低的永久变形及高温力学性能。160℃下老化20 d,材料的拉伸强度保持率大于100%,生物质硅炭表现出较好的耐老化能力。链接-CN官能团的α-碳原子高温下易均裂氢原子生成自由基,连续加氢还原使-C■N转化为-C■NH,直至形成化学交联结构,导致橡胶的玻璃化转变温度升高。氢化丁腈的CN含量越低,耐老化能力越突出。依据分子主链老化的结构演变信息,提出了HNBR的可能老化机理。     

Stereocomplex Crystallization Induced Significant Improvement in Transparency and Stiffness–Toughness Performance of Core-Shell Rubber Nanoparticles Toughened Poly(l-lactide) Blends

Toughening modification of poly(l -lactide) (PLLA) with rubber particles is often realized at the cost of transparency, mechanical strength, and modulus because high rubber loadings are generally required for toughening. In this work, a promising strategy to simultaneously improve the transparency and stiffness–toughness performance of poly(butyl acrylate)-poly(methyl methacrylate) (BAMMA) core-shell rubber nanoparticles toughened PLLA blends by utilizing the stereocomplex (SC) crystallization between PLLA and poly(d -lactide) (PDLA) is devised. The results reveal that the construction of SC crystallites in PLLA matrix via melt-mixing PLLA/BAMMA blends with PDLA can prevent BAMMA nanoparticles from aggregation and promote them to form network-like structure at lower contents. As a result, not only higher toughening efficiency with less rubber contents but also superior transparency is achieved in the PLLA/PDLA/BAMMA blends as compared with the PLLA/BAMMA ones where large aggregated BAMMA clusters are formed. Moreover, the outstanding reinforcement of SC crystallites network for PLLA can impart an enhanced tensile strength and modulus to PLLA/PDLA/BAMMA blends, thus improving the stiffness–toughness performance of PLLA/PDLA/BAMMA blends to a higher degree. This work demonstrates that SC crystallization is a promising solution to solve the contradiction between transparency and mechanical properties and then obtain superior comprehensive performances in rubber toughened PLLA blends.     

型材弯曲模设计

分析了型材在弯曲后其口型失稳起皱的原因,介绍了在型材槽型中填充胶条后在模具的夹持中弯曲成形的工艺,从根本上解决了型材的失稳和起皱,保证了型材的口型尺寸。     

Aging and mechanical properties of NR/BR blends

The mechanical properties and post-thermal aging properties of natural rubber (NR) and polybutadiene rubber (BR) blends at different blending ratios are investigated herein. The experimental results show that both tensile and tear strengths of NR/BR blends increase with increasing NR content. BR has a higher compression stiffness than NR. The deformation of BR is less than that of NR under the same load conditions. With regard to aging properties, both tensile stress and strain of NR/BR blends decrease after prolonged aging. In addition, the stress loss of BR is lower than that of NR, meaning that the aging resistance property of BR is superior to that of NR. Furthermore, accumulated thermal history has shifted the glass transition temperature (T _g) of NR/BR blends toward lower temperatures while the loss tangent (tan δ) value increases with prolonged thermal aging.     

艺术铸件冷冻冰模制模方法的研究

艺术铸件是艺术创作和铸造技术的完美组合，铸造工艺是艺术思想的重要保证。从古至今，艺术家和铸造工作者进行了不懈的探索。本文通过试验，分析了冷冻铸造方法用于艺术铸造的一些优势，探讨了用硅橡胶模具制作冰模的工艺方法，并将用此工艺成功制作的一些冰模展示出来。     

橡胶密炼机混炼工艺瞬时功率控制法

橡胶密炼机混炼工艺瞬时功率控制法的理论由３部分组成：橡胶混炼过程的机理、密炼机流理论和混炼过程功率曲线与能量控制法不同，瞬时功率控制法实质上是控制混炼过程中胶料的粘度，确保混炼工艺过程保持最佳状态。因而瞬时功能控制法可监控生产过程，为密炼机混炼工艺的智能控制奠定了基础。