Development of polybutadiene (BR)–polyethylene (LDPE) blend based microcellular soles for low‐temperature applications

Microcellular (MC) soles based on polybutadiene (BR) and low‐density polyethylene (LDPE) blends for low‐temperature applications were developed. A part of BR in BR–LDPE blend was replaced by natural rubber (NR) for property improvement. The BR–NR–LDPE blend‐based MC sole shows good technical properties. Sulphur curing and DCP curing were tried in BR–LDPE and NR–BR–LDPE blends. Study shows that sulphur‐cured MC sheets possess better technical properties than DCP‐cured MC sheets. 90/10 BR–LDPE and 60/30/10 BR–NR–LDPE blend combinations are found to be suitable for low‐temperature applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 277–281, 2000     

Thermo-oxidative stability of rubber magnetic composites cured with sulfur,peroxide and mixed curing systems

Rubber magnetic composites were prepared by incorporation of strontium ferrite into rubber matrices based on natural rubber (NR) and acrylonitrile butadiene rubber. The sulphur, peroxide and mixed sulphur/peroxide curing systems were applied for cross-linking of rubber compounds. The main goal of the work was to investigate the influence of the curing system composition on the physical–mechanical and magnetic properties of prepared composites. The thermo-oxidative stability of the composite materials was assessed by evaluation of thermogravimetric analysis and ageing test. The results showed that the composition of curing system influences the physical–mechanical properties of composites, but in strong dependence on the type of rubber matrix. After exposure of test sample to the conditions of thermo-oxidative ageing, the changes in composite properties were also recorded. The influence of thermo-oxidative degradation was more pronounced in the case of composites based on NR, where the sample cured only with peroxide system was almost completely degraded in the given conditions of ageing. On the other hand, the magnetic characteristics of composites seem to be influenced neither by curing system composition nor by ageing.     

Preparation and properties of iodine‐doped radiopaque natural rubber

Polymers exhibit low electron density and they are radiolucent. Polymers can be made radiopaque by different techniques. We report a method for the preparation of radiopaque material from natural rubber (NR). NR in its latex form was iodinated. Iodinated natural rubber (INR) was characterized by using UV, thermo gravimetric analysis (TGA), and X‐ray images. INR was compounded at high and low temperatures and its physical properties were measured. The low temperature cured samples show good radiopacity and conductivity. The optical density of low temperature cured samples was measured. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical and Viscoelastic Properties of Natural Rubber/ Reclaimed Rubber Blends

Summary Addition of reclaimed rubber affected mechanical properties, processing and rheological behavior of rubber compounds. Sulfur left in reclaimed rubber affected curing process of NR/reclaimed rubber blends. The most suitable curing was achieved with ratio 1:1 of natural rubber and reclaimed rubber which was used in this study. Presence of fillers in reclaimed rubber, non-homogeneity of phases, non-uniform filler dispersion and lower molecular weight of reclaimed rubber due to chain scission in reclaiming process caused diminishing of mechanical properties of NR/reclaimed blends, particularly dynamic-based properties. Reclaimed rubber also affected rheological behavior of natural rubber. In a strain sweep viscoelastic test, it could be observed that NR/reclaimed blend show more non-linear viscoelastic and viscous behavior than predicted one which was due to non-homogenized phases. This non-homogenized morphology was detected using scanning electron microscopy (SEM) and the blend with ratio 1:1 had the most homogenized morphology.     

丁基橡胶再生胶硫化体系的选择及其对硫化性能的影响

采用超临界CO2流体作传输介质,二苯基二硫(DD)作脱硫剂,研究了废旧丁基橡胶的脱硫再生。结果表明,所得丁基橡胶再生胶(RIIR)不能被硫黄硫化,但能被树脂硫化。在丁基橡胶(IIR)的硫黄硫化过程中,DD不能用作硫化剂和硫化促进剂,其对硫化过程有明显的抑制作用。采用丙酮抽出残留DD后,RIIR可被硫黄硫化。针对IIR/RIIR并用体系,分别以硫黄和树脂作硫化体系且用量相同时,树脂硫化体系的交联密度明显高于硫黄硫化体系。     

Novel dynamic vulcanization of polyethylene and ozonolysed natural rubber blends: Effect of curing system and blending ratio

Dynamic vulcanization was studied in terms of the change in α‐relaxation temperatures of the LDPE matrix, morphology, and mechanical properties of LDPE/ozonolysed NR blends which were vulcanized at various blend ratios and with different curing systems, i.e., peroxide and sulfur systems. The ozonolysed NR with M _w = 8.30 × 10⁵ g mol⁻¹ and M _n = 2.62 × 10⁵ g mol⁻¹, prepared by the in situ ozonolysis reaction of natural rubber latex, was used in this study. The significant change in the α‐relaxation temperature of LDPE in the LDPE/ozonolysed NR, dynamically vulcanized using the sulfur system, suggested that sulfur vulcanization of the blend gave a higher degree of crosslink density than using peroxide and corresponded with the improved damping property and homogenous phase morphology. However, the peroxide cured blends of LDPE/ozonolyzed NR gave more improvement of tensile strength and elongation at break than the sulfur cured system. Furthermore, the mechanical properties of tensile strength, elongation at break, and damping were improved by increasing the ozonolyzed natural rubber content in both DCP and sulfur cured blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

木质素-蒙脱土复合物代替三角带底胶中炭黑的应用研究

通过共沉淀-脱水法制备了木质素-蒙脱土复合物填料,并湿法混炼制备了木质素-蒙脱土复合物填充三角带底胶试验胶。研究了硫磺和促进剂的量、天然橡胶(NR)和顺丁橡胶(BR)的质量比对三角带底胶试验胶的硫化特性和力学性能的影响。并将木质素-蒙脱土复合物填充三角带底胶与炭黑填充的三角带底胶进行了比较。结果表明:增加硫磺和促进剂的量,提高了三角带底胶试验胶的硬度和300%定伸应力。增加天然橡胶和顺丁橡胶的质量比提高了三角带底胶试验胶的拉伸强度。调整配方后三角带底胶试验胶的综合性能已与N330填充胶料相当。     

杜仲胶/天然橡胶/顺丁橡胶并用胶的工艺研究

用杜仲胶(TPI)替代部分天然橡胶(NR),并与顺丁橡胶(BR)共混生产出混炼胶,研究了TPI/NR/ BR共混硫化胶料制备过程中,硫化温度、硫化时间、硫化剂的用量、硫化促进剂的种类及用量对胶料物理机械性能的影响。研究结果表明,硫化过程中当硫化温度为150℃、硫化时间为20 min、硫化剂为硫黄(质量不超过3份)和硫化促进剂的含量为2份时,胶料的综合物理机械性能较好。     

Improved mechanical properties of NR/EPDM and NR/ butyl blends by precuring EPDM and butyl

Ethylene-propylene-diene rubber (EPDM) and isobutylene-isoprene rubber (IIR) were compounded, precured to a low degree, and then were blended with natural rubber (NR). The compounding ingredients for NR were then added and the final curing was done. NR/EPDM and NR/IIR blends, prepared using this method, were found to possess much improved mechanical properties as compared to their conventional counterparts. The optimum precuring crosslink density that has to be given to the EPDM and IIR phases has been determined. © 1993 John Wiley & Sons, Inc.     

NR/SBR内胎胶配方的改进

对天然橡胶(NR)/丁苯橡胶(SBR)内胎胶配方进行调整:降低NR用量比例,调整补强体系和硫化体系。结果表明:NR/SBR并用比由60/40减小到50/50,胶料的门尼粘度较大,焦烧时间较长,加工安全性较好,热老化后性能下降率低,其他性能差异不大;成品内胎的耐热老化后性能明显改善,生产成本降低。     

木质素-硅藻土复合物在三角带底胶中的应用研究

通过共沉淀-脱水法制备了木质素-硅藻土复合物填料,并湿法混炼制备了木质素-硅藻土复合物填充三角带底胶实验胶。通过无转子硫化仪、电子万能试验机、邵氏硬度计研究了硫磺和促进剂的量、天然橡胶和顺丁橡胶的量对三角带底胶实验胶的硫化特性和力学性能的影响,并将木质素-硅藻土复合物填充三角带底胶与炭黑填充的三角带底胶实验胶进行了比较。结果表明:增加硫磺和促进剂的量,提高了三角带底胶实验胶的硬度和300%定伸应力;将顺丁橡胶替换成天然橡胶则提高了三角带底胶实验胶的拉伸强度。配方调整后三角带底胶实验胶的综合性能已与N330填充胶料相当。     

Influence of nanoclay‐carbon black hybrid fillers on cure and properties of natural rubber compounds

The influence of organically modified nanoclay‐carbon black (CB) hybrid filler on the curing behavior of natural rubber (NR) was explored in this investigation. Here an effort was paid to understand the curing kinetics of organomodified nanoclay filled rubber compounds. On the basis of two different types of modified clay, NR nanocomposites were prepared and cured by a conventional vulcanization system. A faster curing rate and lower torque values were found when the modification was done by quaternary ammonium compounds. The activation energy of the rubber curing process decreased with the incorporation of nanoclay. In addition, it was revealed that the quaternary ammonium compounds used as modifier in the clay show a plasticization effect. Additionally, X‐ray diffraction studies indicated, that the basal spacing of the clay minerals was increased in both cases after incorporation in the rubber matrix. The dynamic mechanical analysis using a strain sweep mode showed that the Payne effect decreases because of an improved dispersion of CB induced by the presence of nanoclay. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

天然橡胶疲劳性能的配方与工艺研究

研究了配方及加工工艺对天然橡胶疲劳性能的影响。结果表明：1）硫化体系对硫化胶疲劳寿命有显著影响,普通硫化体系抗疲劳性能最好,有效硫化体系抗疲劳性能最差;2）加入增硬剂可获得流动性好、疲劳性能优异的高硬度天然橡胶胶料;3）加工工艺对橡胶材料疲劳性能影响显著,采用密炼工艺,以升华硫磺替代沉淀硫磺,同时在胶料中加入适量的分散剂,可明显改善胶料中炭黑和配合剂的分散性,提高橡胶硫化制品的抗疲劳性能。     

生胶挤出中的动态结晶及应力振荡行为

用Instron毛细管流变仪研究了NR、BR和NR/BR并用胶的流动行为,讨论了一定条件下形成不稳定流动的原因及影响因素。发现在较低温度下NR由于动态结晶而产生压力突增现象及不规则应力振荡;在较高温度下BR由于粘滑效应而产生规则应力振荡。这两种振荡都不可能在一般加工温度和剪切速率范围内完全加以避免,因此采用NR/BR并用胶是解决高含胶率胶料稳定挤出的有效途径。     

Effects of filler contents and processing parameters on the weldline strength of compression molded natural rubber

The presence of weldlines in rubber products is regarded as a one of the most undesirable phenomena, since it results in poor mechanical properties. Compression molding of large or complicated products are prepared by multiple charges, which produces weldlines once the melt fronts are joined by the impingement flow. In this work, the effects of curing systems, processing parameters, filler types, and contents on weldline strength of compression molded natural rubber (NR) were investigated. Furthermore, the effects of curing systems on the aging properties of NR vulcanizates were studied in details. The results show that an increased amount of calcium carbonate does not affect the weldline strength. However, the difference in tensile strength between weldline and nonweldline specimens becomes larger with the high loading of silica and carbon black. In addition, for the factors selected in the experiments, clamping pressure, and curing system were found to be the principal factors affecting the weldline property of vulcanizates. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

A Study of Rheological Behavior and Compatibility of NR/BR Blends

In this study, we research the Mooney viscosity, curing rates, and processibility of natural rubber (NR) and polybutadiene rubber (BR) blends at different blending ratios. The changing values are measured during vulcanization processing and were tested by Mooney viscometer, Monsanto viscometer, etc. The results of scanning electron microscope (SEM) and dynamic mechanical analysis (DMA) experiments are used to explore the surface morphologies and molecular mobility of NR/BR blends.

The experimental results indicate that Mooney viscosity tends to decrease with increasing NR content of NR/BR blends, and this results in superior processibility of NR/BR blends with increasing NR content. NR/BR blends' curing rate improved with increasing NR content. The DMA experimental results show that the temperature is suitable to produce a character peak (T_αn) in molecular motions of NR/BR blends. There tends to a lower temperature range with decreasing NR content of NR/BR blends. In addition, T_αb would move to a lower temperature with decreasing BR content of NR/BR blends.     

Thermal aging properties and chemical resistance of blends of natural rubber and epoxidized low molecular weight natural rubber

Studies into solvent resistance and aging properties of blends of natural rubber and epoxidized low molecular weight natural rubber were carried out. Vulcanization of the blends using the semi‐efficient vulcanization (semi‐EV) system was found to have curing advantages over conventional vulcanization (CV) and efficient vulcanization (EV) systems. The rheological properties (cure time, t₉₀, and scorch time, t₂), solvent resistances, and aging properties of the vulcanizates were found to improve as the level of epoxidized low molecular weight natural rubber in the blends increases. The mechanical properties of the blends were also found to be within the accepted level for NR vulcanizates. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1733–1739, 2005     

Covulcanisation of natural rubber and chlorobutyl rubber. Effect of curative diffusion between phases and ZnCl2 addition

Abstract

Natural rubber (NR) and chlorobutyl rubber (CIIR) were compounded with various formulations containing tetramethylthiuram disulphide (TMTD), sulphur, and ZnO, and masterbatches of these compounds were blended in a 70 : 30 NR/CIIR ratio and vulcanised in a press at 150°C. Crosslink densities of vulcanisates were determined by swelling and tensile properties measured. In formulations in which the concentration gradient permitted the diffusion of TMTD and sulphur to a CIIR phase containing ZnO, tensile strengths were slightly better than 70% of the values of NR compounds of similar crosslink densities. In formulations in which TMTD and sulphur diffused to the faster curing NR phase, blend properties were also better than 70% of those of NR compounds, but at higher crosslink densities, tensile strengths and elongation at break decreased in parallel. This was attributed to failure in a layer of more highly crosslinked material formed within the NR phase close to the interface. Although ZnCl₂ can crosslink CIIR to NR, thus ensuring good interfacial bonding, the addition of ZnCl₂ to the CIIR masterbatch led to attack on the TMTD accelerator and a significant reduction in crosslink density and tensile properties of blends.     

Natural rubber–isotactic polypropylene thermoplastic blends

Thermoplastic elastomers, prepared by melt blending of natural rubber (NR) and isotactic polypropylene (PP) through a dynamic vulcanization technique, were developed during the later 1970s. However, they have certain drawbacks due to thermal degradation and higher molecular weight of NR. In the study reported here, NR was masticated to different levels prior its addition to isotactic polypropylene to improve the flow properties and to reduce the incompatibility resulting from molecular weight mismatch of NR/PP thermoplastic blends. Mixing energy curves of uncrosslinked blends and those of dynamically vulcanized blends crosslinked using different cure systems were compared. The mixing energy curves of blends containing NR of different molecular weight (M _n) and two grades of PP (injection and film grades) were also compared. Technological and processing properties of the dynamically vulcanized (sulphur and peroxide cure systems) and unvulcanized blends were compared with those of the samples containing unmasticated NR. The results indicated that a number average molecular weight in the range 4 × 10⁵ for NR increased the procoessability without significantly affecting the technological properties of NR/PP thermoplastic blends. Among the three cure systems studied Luperox 101 and dicumyl peroxide gave better technological properties than the sulphur‐cured samples. Two antioxidants, viz. quinoline (TDQ) and imidazole (MBI) type, were tried in NR/PP blends. It was found that TDQ imparts better aging resistance compared to MBI. The improvement in processability due to the reduction in molecular weight of natural rubber by mastication is more noticeable in the case of peroxide vulcanized blends compared to sulphur vulcanized samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2063–2068, 2004     

平衡硫化体系硫化天然橡胶的平衡硫化性和化学应力松弛行为

<正>WOlff’‘,”采用双（3-三乙氧基甲硅烷基丙基）-四硫化物（St69）与硫黄组成的平衡硫化体系（EC）,既减少了硫化返原的产生,又保留了传统硫黄硫化体系（CV）的优点,同时克服了因采用有效硫化体系（EV）或半有效硫化体系（SEV）所导致的强度等