COORDINATION CROSSLINKING OF NITRILE RUBBER FILLED WITH COPPER SULFATE PARTICLES

By incorporating copper sulfate （CuSO4） particles into acrylonitrile butadiene rubber （NBR） followed by heat pressing, a novel vulcanization method is developed in rubber through the formation of coordination crosslinking. This method totally differs from traditional covalent or non-covalent vulcanization approaches of rubber. No other vulcanizing agent or additional additive is involved in this process. By analyzing the results of DMA, XPS and FT-IR, it is found that the crosslinking of CuSO4 particles filled NBR was induced by in situ coordination between nitrogen atoms of nitrile groups （-CN） and copper ions （Cu^2＋） from CuSO4. SEM and EDX results revealed the generation of a core （CuSO4 solid particle）- shell （adherent NBR） structure, which leads to a result that the crosslinked rubber has excellent mechanical properties. Moreover, poly（vinyl chloride） （PVC） and liquid acrylonitrile-butadiene rubber （LNBR） were used as mobilizer to improve the coordination crosslinking of CuSO4/NBR. The addition of PVC or LNBR could lead to higher crosslink density and better mechanical properties of coordination vulcanization. In addition, crystal water in CuSO4 played a positive role to coordination crosslinking of rubber because it decreased the metal point of CuSO4 and promoted the metal ionization.

Physical and damping properties of kenaf fibre filled natural rubber/thermoplastic polyurethane composites

The paper presents the investigation of the effect of alkaline treatment of sodium hydroxide(NaOH) on physical and dynamic mechanical analysis(DMA) viscoelastic properties of kenaf fibre filled natural rubber(NR)/thermoplastic polyurethane(TPU) composites.The treated kenaf fiber,NR and TPU were weighed and proportioned according to the required compositions and were blended using hot mixed Brabender machine.The polymer composites were then fabricated using the hot press to form a sample board.The sample was cut and prepared and water absorption,density,thickness swelling and DMA tests were performed.As far as physical properties are concerned,composites with the highest NR amount of shows the best results,which indicates good fiber bonding adhesion.The polymer composites with the highest amount of TPU shows the highest damping properties at high temperature.

Effect of UV radiation aging on creepage discharge characteristics of high temperature vulcanized silicon rubber at high altitude

The physicochemical properties and creepage discharge characteristics of aged high temperature Vulca nized(HTV)silicone rubber materials were investigated by ultraviolet radiati on(UV)aging method in this study.The experimental results show that as the aging time increases,the creepage discharge flashover voltage increases first and then decreases.But the aging time has little effect on the creepage discharge inception voltage.With the aging time prolonged,the discharge endurance time of HTV silicone rubber is shortened,and the creepage discharge development velocity is accelerated.In the short time of applying voltage to aging material,the magnitude of discharge in creases rapidly.According to the partial discharge characteristic parameters of creepage discharge,the whole creepage discharge process is partitioned into four stages.Compared with unaged HTV silicone rubber,the aged HTV silicone rubber has less fluctuation in performance parameters and a clear trend.The study found that UV aging not only affects the physicochemical and hydrophobic properties of the HTV silicone rubber,but also accelerates the development of creepage discharge under AC voltage.

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 Reax FF molecular dynamics simulation.A series of crosslinked SBR models were built with different sulfur contents and densities.The following Reax FF 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 H_(2)S.High sulfur contents tend to the formation of elemental sulfur intermediate,and temperature increase facilitates the release of H_(2)S.

Magnetic,thermal stability and dynamic mechanical properties of beta isotactic polypropylene/natural rubber blends reinforced by NiZn ferrite nanoparticles

The dispersion of magnetic nanoparticles in matrix is crucial to ensure optimum performance of the composite.The difficulty level of achieving good dispersion is further increase when a multi-phases of matrix is present.A pre-coating technique of magnetic nanoparticles with polypropylene using ball-mill prior to melt-blending process was employed to prepare a multi-phases thermoplastic natural rubber composite.The effect of filler loading(2 wt%-10 wt%) on morphology,structure,magnetic properties,thermal stability and dynamic mechanical properties of the composites were investigated.It was found that the NiZn ferrite nanoparticles act as nucleating agent to form beta isostatic polypropylene thermoplastic composites.The composites’ magnetic properties are directly dependent on the filler concentration.The dispersion of magnetic fillers in polymer matrix plays role in affecting the magnetic properties and thermal stability.The preference of filler to locate at amorphous phase has distorted the chain orientation of natural rubber and polypropylene.Hence,the polymorphism and crystallinity of the matrix varied as the filler loading increased,affecting the dynamic mechanical properties.It was found that 8 wt% NiZn nanocomposite exhibits highest E’ and tanδ,indicating the dynamic mechanical properties of NiZn nanocomposite are affected by β-phase degree.

STUDIES ON SELF-VULCANIZING FLUOROELASTOMER/PHENOL HYDROXY SILICONE RUBBER BLENDS

Self-vulcanizing blends of phenol hydroxy silicone rubber (PHSR) and fluoroelastomer (FPM) were prepared. Vulcanized rubbers with lower glass transition temperature (T(g)) were successfully obtained. The results of dynamic mechanical analysis (DMA) show that the vulcanized FPM/PHSR (10 phr) blend has only one T(g) temperature, demonstrating the well compatibility between FPM and PHSR. The thermogravimetric analysis (TGA) demonstrates that the PHSR do little damage to the thermal stability of FPM. The vulcanization characteristics of the FPM/PHSR blends were analyzed by using oscillating disc rheometer (ODR). The results show that FPM/PHSR blends have smaller S(min) values and longer scorch time than that of FPM with the same level of bisphenol AF curing agent. It means that FPM/PHSR blends have better processability and curing security. Better mechanical properties can be gained for FPM/PHSR blends at appropriate level of PHSR.

EFFECTS OF SOME PHENYLETHYNYLSILICON COMPOUNDS ON HEAT-CURABLE SILICONE RUBBER Ⅲ 1, 1, 3, 3-TETRAMETHYL-1, 3-DIPHENYLETHYNYL-DISILOXANE

We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed.

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.

Study the Effect of Recycled Tire Rubber on the Mechanical and Rheological Properties of TPV (HDPE/Recycled Tire Rubber)

Thermoplastic elastomeric blends prepared from blending of (10%, 20%, 30%, 40% and 50 wt%) high density polyethylene(HDPE) and (10%, 20%, 30%, 40% and 50 wt%) ground rubber tire (TPV-R). The blends prepared contain (HDPE)/polybutadiene (TPV-V). The two blends were successfully prepared through a dynamic vulcanization process, involving dicumyl peroxide (3%) as vulcanizing agent. The data of the mechanical (tensile strength at yield, %elongation and young modulus) and rheological properties (shear stress, shear rate, viscosity, flow behavior index and activation energy of melt flow) of the TPV-V and TPV-R showed that there was comparable results between the two blends.

Improving the Thermal Conductivity and Mechanical Properties of Twocomponent Room Temperature Vulcanized Silicone Rubber by Filling with Hydrophobically Modified SiO_2-Graphene Nanohybrids

The SiO_2 nanoparticles were coated on the surface of graphene oxide(GO) by sol-gel method to get the SiO_2-G compound.The SiO_2-G was restored and oleophylically modified to prepare hydrophobic modified SiO_2-G(HM-SiO_2-G) which was subsequently added to silicone rubber matrix to prepare two-component room temperature vulcanized(RTV-2) thermal conductive silicone rubber. The morphology, chemical structure and dispersity of the modified graphene were characterized with SEM, FTIR, Raman, and XPS methods.In addition, the heat-resistance behavior, mechanical properties, thermal conductivity, and electrical conductivity of the RTV-2 silicone rubber were also studied systematically. The results showed that the SiO_2 nanoparticles were coated on graphene oxide successfully, and HM-SiO_2-G was uniformly dispersed in RTV-2 silicone rubber. The addition of HM-SiO_2-G could effectively improve the thermal stability, mechanical properties and thermal conductivity of RTV-2 silicone rubber and had no great influence on the electrical insulation performance.

Insight into Vulcanization Mechanism of Novel Binary Accelerators for Natural Rubber

A novel TU derivative, N-phenyl-N＇-（γ-triethoxysilane）-propyl thiourea （STU）, is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso- thiocyanate fragment still remains in the NPUSTU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.

液体丁腈橡胶YN25对丁腈橡胶2980的改性

将液体丁腈橡胶(牌号YN 25)与丁腈橡胶(NBR)2980进行机械共混制备了NBR 2980 M,研究了YN 25加入量对NBR 2980 M混炼胶的门尼黏度、硬度和硫化特性及硫化胶拉伸性能的影响。结果表明,随YN 25加入量增加,NBR 2980 M的门尼黏度、50 min的300%定伸应力、拉伸强度、最大和最小转矩均呈线性下降,扯断伸长率及25 min、50 min和90 min三个转矩差硫化时间均线性上升,而混炼胶硬度的变化不明显。YN 25在NBR 2980 M中的质量分数每增加1%,混炼胶门尼黏度下降0.78,50 min的300%定伸应力、拉伸强度、最大和最小转矩分别下降0.15 MPa、0.17 MPa、0.12 dN·m和0.02 dN·m,扯断伸长率及25 min、50 min和90 min三个硫化时间分别增加4.1%、0.05 min、0.08 min和0.18 min。

不溶性硫磺用环保橡胶填充油的制备及性能评价

以环烷基减一线馏分油为原料,经加氢精制工艺得到环保橡胶填充油(简称橡胶油),以此环保橡胶油制备充油型不溶性硫磺,并对其应用性能进行评价。结果表明:加氢精制工艺可以制备满足欧盟2005/69/EC法规要求的环保橡胶油,以此环保橡胶油制备的充油型不溶性硫磺具有优良的使用性能,有效地拓宽了减一线馏分油的应用领域,实现油品向特色化工品的转变。

环保橡胶增塑剂RAE作橡胶填充油的性能研究

以环烷基减压渣油为原料,制备高芳碳含量的环保橡胶增塑剂RAE,将其与进口处理芳烃油进行对比研究。试验结果表明,RAE可作为填充油制备充油乳聚丁苯橡胶,充油丁苯橡胶的生胶性能、化学组成、结构组成等与使用进口处理芳烃油合成的充油丁苯橡胶性能相近;使用RAE制备的充油丁苯橡胶,在半钢胎胎面胶配方中,具有良好的混炼胶性能、硫化胶物理性能和动态力学性能。

3种汽车密封条用TPV的性能研究

研究了3种国产汽车密封条用热塑性硫化橡胶(TPV)产品(TPV-1,TPV-2,TPV-3)的力学性能、耐热性能、微观形貌和热氧老化性能。结果表明:3个产品的树脂相可能均为嵌段共聚聚丙烯(PP)。3个产品中,TPV-3的拉伸强度、断裂伸长率和撕裂强度均最大,TPV-1的拉伸强度和断裂伸长率均最小,TPV-1和TPV-2的撕裂强度相当,TPV-1的耐热性能和热氧老化性能均最好,TPV-3的耐热性能最差,TPV-2和TPV-3的热氧老化性能相当,在温度70℃、时间22 h、压缩率25%下,TPV-1的压缩永久变形最大,TPV-3最小,在温度23℃、时间72 h、压缩率25%下,TPV-1和TPV-3的压缩永久变形相当,TPV-2的压缩永久变形最小。

环氧化溶聚丁苯橡胶改性的溶聚丁苯橡胶/白炭黑复合材料的性能

将环氧度为15%的环氧化溶聚丁苯橡胶作为改性剂,研究了环氧化溶聚丁苯橡胶对溶聚丁苯橡胶/白炭黑复合材料的加工性能、物理机械性能、动态力学性能及白炭黑分散性等的影响。结果表明,环氧化溶聚丁苯橡胶的加入减缓了复合材料的硫化速率,混炼胶中的结合胶含量增大;溶聚丁苯橡胶/白炭黑硫化胶的定伸应力、耐磨性及回弹性能提高,压缩生热降低,同时硫化胶的抗湿滑性能得到提升、滚动阻力下降。

医疗器械用热塑性弹性体的制备及耐辐照性能

采用具有耐辐照特性的溴化聚(异丁烯-对甲基苯乙烯)(BIMS)为基体橡胶,与苯乙烯-乙烯-丁烯-苯乙烯嵌段共聚物(SEBS)共混,以烷基苯酚二硫化物作为硫化交联剂,并配合一种生物基增塑剂,采用动态硫化工艺,制备了一种医疗器械用耐辐照动态硫化热塑性弹性体(TPV)。通过对不同剂量辐照后TPV的基本理化性质、顶空气相色谱、红外图谱、热稳定性、动态机械性能和力学性能对比分析研究发现,在辐照灭菌(≤40 kGy)后,产品性能未发生变化,可满足常规医疗器械用弹性体制品对耐辐照性能的要求。

天然橡胶/三元乙丙橡胶并用胶辐射交联制备及其耐热空气老化性能

针对天然橡胶(NR)/三元乙丙橡胶(EPDM)并用胶共混效果不佳和耐老化性能较差的问题,本研究采用辐射交联技术制备了天然橡胶/三元乙丙橡胶并用胶,通过与热交联制备的并用胶对比,明确了辐射交联工艺对共混效果的促进作用。重点分析了NR/EPDM共混胶中生胶并用比和辐射交联等因素对老化前后并用胶力学性能的影响规律。热空气老化前,随着EPDM占比的增大,热交联样品的初始拉伸强度和伸长率曲线呈先降低后上升趋势,而辐射交联样品初始拉伸强度和伸长率呈线性下降趋势,说明辐照处理改善了EPDM/NR并用胶初始力学性能,辐射交联提高了NR和EPDM分子之间交联结构的完善性。热空气老化后,辐射交联样品的性能下降幅度小于热交联的样品,说明在热交联基础上,引入辐射技术可以提升辐射交联样品热老化后的伸长率保持率,尤其是在NR占比较大的情况下,辐射样品性能下降幅度能减小约50%。由此说明,利用辐射交联技术制备天然橡胶/三元乙丙橡胶并用胶具有比传统热硫化交联具有更好的耐热空气老化性能。

对氨基水杨酸镧对天然橡胶硫化特性的影响

以氯化镧和对氨基水杨酸钠为原料,采用沉淀法合成了新型环保促进剂对氨基水杨酸镧(PAS-La)。通过元素分析、热分析和红外光谱分析等方法对产物进行了表征并确定其分子式为La(C_(7)H_(6)NO_(3))_(3)·H_(2)O。利用无转子硫化仪、平衡溶胀法和万能试验机考察了PAS-La对天然橡胶硫化特性、交联密度和力学性能的影响,并对硫化动力学进行了分析。结果表明,随着PAS-La添加量的增加,天然橡胶的正硫化时间存在最大值,焦烧时间先减小后增大;硫化胶的交联密度增大,力学性能明显增强。当PAS-La的添加量为1.2份(质量)时,其对天然橡胶的硫化促进作用达到最佳。动力学计算发现,随着PAS-La添加量的增加,交联前驱体的反应活性增强,活化能先减小再增大。

氯丁橡胶硫化反应动力学

以1,2-亚乙基硫脲为促进剂、氧化锌和氧化镁为硫化剂对氯丁橡胶进行硫化,采用差示扫描量热法研究了氯丁橡胶的非等温硫化反应动力学,通过Kissinger方程和Crane方程计算了硫化反应的动力学参数,并采用硫化仪法研究了等温硫化反应的动力学,计算了硫化反应热硫化阶段的表观活化能。结果表明,n级动力学模型可以有效描述氯丁橡胶的非等温硫化过程,硫化反应的表观活化能为92.78 kJ/mol,反应级数为0.93;氯丁橡胶的等温硫化过程可以分为焦烧阶段、热硫化阶段和平坦硫化阶段,其中热硫化阶段符合一级反应动力学特征,此时表观活化能为53.38 kJ/mol。