Cure characteristics and mechanical properties of hydrogenated natural rubber/natural rubber blends

The cure characteristics and mechanical properties of blends consisting of hydrogenated natural rubber (HNR) and natural rubber (NR) blends were investigated. The HNR/NR blends at 50/50 wt ratio were vulcanized using various cure systems: peroxide vulcanization, conventional vulcanization with peroxide, and efficient vulcanization with peroxide. The HNR/NR vulcanizates cured by the combination of peroxide and sulfur donor (tetramethylthiuram disulfide, TMTD) in the efficient vulcanization with peroxide exhibited the best mechanical properties. It was also found that the hydrogenation level of HNR did not affect the tensile strength of the vulcanizates. The tensile strength of the blends decreased with increasing HNR content because of the higher incompatibility to cause the noncoherency behavior between NR and HNR. However, the HNR/NR vulcanizate at 50/50 wt ratio showed the maximum ultimate elongation corresponding to a co‐continuous morphology as attested to by scanning electron micrographs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thioacetate- and mercapto-functionalized hydrogenated natural rubber

Due to the differences in unsaturation levels of constituent rubbers, thioacetate and mercapto functional groups were introduced into hydrogenated natural rubber (HNR) to increase the compatibility of natural rubber (NR)/HNR blends. The effect of thioacetic acid and initiator concentrations including reaction time on the thioacetate content in HNR was investigated. Methanolysis of thioacetate-modified HNR (HNRTA) yielded mercapto-modified HNR (HNRSH). The addition of HNRTA or HNRSH into NR/HNR blends (50/50 wt ratio) increased the tensile strength. The improved mechanical properties of the compatibilized blends were confirmed by scanning electron microscopy, indicating a co-continuous morphology. Furthermore, the susceptibility of the vulcanizates to changes in temperature and ozone were also reported.     

Fly‐ash particles and precipitated silica as fillers in rubbers. II. Effects of silica content and Si69‐treatment in natural rubber/styrene–butadiene rubber vulcanizates

This article explored the possibility of using silica from fly‐ash particles as reinforcement in natural rubber/styrene–butadiene rubber (NR/SBR) vulcanizates. For a given silica content, the NR : SBR blend ratio of 1 : 1 (or 50 : 50 phr) exhibited the optimum mechanical properties for fly‐ash filled NR/SBR blend system. When using untreated silica from fly‐ash, the cure time and mechanical properties of the NR/SBR vulcanizates decreased with increasing silica content. The improvement of the mechanical properties was achieved by addition of Si69, the recommended dosage being 2.0 wt % of silica content. The optimum tensile strength of the silica filled NR/SBR vulcanizates was peaked at 10–20 phr silica contents. Most mechanical properties increased with thermal ageing. The addition of silica from fly‐ash in the NR/SBR vulcanizates was found to improve the elastic behavior, including compression set and resilience, as compared with that of commercial precipitated silica. Taking mechanical properties into account, the recommended dosage for the silica (FASi) content was 20 phr. For more effective reinforcement, the silica from fly‐ash particles had to be chemically treated with 2.0 wt % Si69. It was convincing that silica from fly‐ash particles could be used to replace commercial silica as reinforcement in NR/SBR vulcanizates for cost‐saving and environment benefits. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

白炭黑用量对氯丁橡胶/天然橡胶共混物性能的影响

研究了不同用量的沉淀法白炭黑填充质量比75/25的氯丁橡胶/天然橡胶共混物的物理机械性能、耐热老化性能和耐油性能,并用扫描电镜研究了共混物的结构。结果显示,白炭黑的加入改善了共混硫化物的拉伸强度、100%定伸应力和邵尔A硬度。压缩永久变形减小,黏度增大,从而导致在形变的过程中天然橡胶分散相占有率相对减少。相关性能也证明随着白炭黑用量的增加,硫化胶的耐热和耐油性能显著提高。     

Influence of rubber composition on change of crosslink density of rubber vulcanizates with EV cure system by thermal aging

Variation of the crosslink density of a rubber vulcanizate depending on the rubber composition after the thermal aging was studied with single rubber, biblend, and triblend vulcanizates of natural rubber (NR), butadiene rubber (BR), and styrene‐butadiene rubber (SBR). The efficient vulcanization (EV) system was employed to minimize the influence of free sulfur in the vulcanizate on the change of the crosslink density. Thermal aging was performed at 40, 60, and 80°C for 20 days with 5‐day intervals. The crosslink densities of the vulcanizates after the thermal aging increase. For the single rubber vulcanizates, variation of the crosslink density by the thermal aging has the order: SBR > BR > NR. For the biblend vulcanizates, variations of the crosslink densities of the NR/SBR and SBR/BR blends are larger than that of NR/BR blend. Variation of the crosslink density of the vulcanizate increases by increasing the SBR content in the vulcanizate. Variation of the crosslink density of the rubber vulcanizate depending on the rubber composition was explained by miscibility of the blends, combination reaction of the pendent groups, and mobility of the pendent group. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1378–1384, 2000     

Structure and performance of hydrogenated natural rubber prepared by the latex method

Hydrogenated natural rubber (HNR) with different degrees of hydrogenation was prepared by the latex method. The hydrazine hydrate/hydrogen peroxide/boric acid catalytic system could result in the hydrogenation of natural rubber (NR) under the latex state. The NR without hydrogenation contained around 13% of gel, when the hydrogenation degree reached 66.9%, the gel content was 34.4%. The decomposition temperature of HNR kept on increasing, which was all higher than that of NR and the glass transition temperature increased slightly. The cross-linking density of vulcanised rubber rose along with the increasing degree of hydrogenation, the NR cross-linking density was 0.114 mmol cm^?3, when the hydrogenation degree was 34.6%, 42.7% and 66.9%, the cross-linking density was 0.182, 185 and 221 mmol cm^?3, respectively. This further proved decreasing flexibility of the HNR after hydrogenation and weakening crystallisation of HNR along with increasing degree of hydrogenation.     

Mechanical and morphological properties of cellular NR/SBR vulcanizates under thermal and weathering ageing

The effects of addition of two chemical blowing agents in cellular rubber blend of natural rubber (NR) and styrene‐butadiene rubber (SBR) at a fixed blend ratio of 1 : 1 on cure characteristics, and mechanical and morphological properties were invesigated. The chemical blowing agents used in this work were Oxybis (benzene sulfonyl) hydrazide (OBSH) and Azo dicarbonamide (ADC). Three different fillers, fly ash (FA) particles, precipitated silica, carbon black (CB) at their optimum concentrations of 40 phr were used, the FA and silica particles being chemically treated by bis‐(3‐triethoxysilylpropyl) tetrasulphide. The results suggested that the overall cure time decreased with OBSH and ADC contents. The OBSH was more effective in cure‐acceleration of the NR/SBR blend than the ADC. The NR/SBR vulcanized foams produced by OBSH and ADC agents had closed‐cell structures. The specific density and mechanical properties of the blend tended to decrease with increasing blowing agent content. The CB gave NR/SBR foams with smaller cell size, better cell dispersion, and higher mechanical properties than the precipitated silica and FA particles. The heat ageing and weathering resulted in an increase in tensile modulus and hardness, but lowered the tensile strength, ultimate elongation and tear strength. The elastic recovery for cellular NR/SBR vulcanizates with FA was superior to that with CB and silica, the elastic recovery of the blends decreasing with blowing agent content. Resilience property was improved by the presence of gas phases. The optimum concentration of OBSH and ADC to be used for NR/SBR vulcanizates was 4 phr. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Reclaiming of ground rubber tire by a novel reclaiming agent. I. virgin natural rubber/reclaimed GRT vulcanizates

Mechanochemically devulcanized ground rubber tire (GRT) was (re)vulcanized in compositions with virgin natural rubber (NR). The NR/GRT (re)vulcanizates with GRT content from 20 to 60 wt% have been prepared and studied. Reclaiming of GRT was successfully carried out by tetra methyl thiuram disulfide (TMTD) in presence of spindle oil at around ambient temperature. The cure characteristics and mechanical properties of the virgin NR/reclaim GRT blend were studied. The optimum cure time decreases but scorch time remain unaltered with increasing reclaim rubber content in the blend. Effect of carbon black was studied in NR/RR (80/20) blend. Ageing characteristics of different NR/RR blends were evaluated. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the NR/RR vulcanizate. The dynamic mechanical properties and swelling behavior of NR/RR blend vulcanizates were examined. The elastic and storage modulus of the NR/RR vulcanizates become improve with increasing reclaim rubber content. Electrical properties of NR/RR vulcanizates were also studied. POLYM. ENG. SCI., 47:1091–1100, 2007. © 2007 Society of Plastics Engineers     

NR–EPDM covulcanization: A novel approach

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS) was used successfully as a novel coupling agent cum accelerator to co‐vulcanize the elastomer blend comprising highly unsaturated natural rubber (NR) and ethylene propylene diene rubber (EPDM) of low unsaturation content. The blend vulcanizates produced exhibit improved physical properties that can be further enhanced by implementing a two‐stage vulcanization technique, as well as by judicious selection of the NR‐to‐EPDM ratio. The results indicate coherency and homogeneity in the blend composition of two‐stage vulcanizates. The cure‐rate mismatch problem could thus be solved through the formation of rubber‐bound intermediates with a multifunctional rubber additive (i.e., DIPDIS), thereby restricting the curative migration from lower to highly unsaturated rubber. The blend morphology as revealed by SEM studies accounts for significant improvement in physical properties, particularly in two‐stage vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 800–808, 2001     

Effect of Sol-Gel-Derived Nano-silica on the Properties of Natural Rubber-Poly Butadiene Rubber-Reclaim Rubber Ternary Blends/Silica Nanocomposites

Silica incorporation into natural rubber (NR)-polybutadiene rubber (PBR)-reclaim rubber (RR) ternary blend system was carried out by sol-gel technique at different temperatures. The effect of RR on silica reinforcement was studied for NR-PBR-RR blend systems. The physicochemical properties of sol-gel vulcanizates indicates that the reinforcing efficiency of the nanocomposites increases with increasing RR content. Sol-gel vulcanizates prepared at 50°C shows superior mechanical properties than others. The amount of silica incorporated by sol-gel technique was determined through thermogravimetry analysis, which indicates the increasing trend of thermal stability with silica content. SEM studies indicate the coherency and homogeneity in the NR-PBR-RR/SiO ₂ nanocomposites.     

Effect of fillers on morphological properties in NR/SBR blends for OTR tyres

Abstract

The blends of styrene butadiene rubber (SBR) and natural rubber (NR) are prepared using a two-roll mixing mill in the presence of different types of carbon blacks as reinforcing filler. The effects of fillers on cure characteristics and thermal, dynamic–mechanical, morphological properties of the blends are studied. The ISAF N231 type of carbon black shows a significant effect on tensile, tear and modulus properties by reacting at the interface between SBR/NR matrixes. The dynamic characteristics and storage modulus of SBR/NR with SAF N110 and SRF N774 types of carbon black show distinct characteristics in respect to all other blends in this system. The thermal stability of the rubber vulcanizates containing SAF N110 and SRF N774 types of carbon blacks is higher than other blend types. With the increasing percentage of SBR to NR, the thermal stability of the blend is increased. However, the heat buildup of the blends increases with the increase in SBR percentage.     

天然橡胶/再生胶共混胶的交联密度与力学性能

对不同天然橡胶(NR)/再生胶(RR)共混比、不同硫磺及轻质碳酸钙含量的NR/RR共混胶的交联密度和力学性能进行分析测试,并对RR的橡胶烃含量、炭黑含量和无机杂质含量进行热失重测试分析。结果表明,随着RR含量和硫磺含量的增加,硫化胶交联密度上升,轻质碳酸钙含量变化对于硫化胶交联密度没有产生规律性的影响。NR/RR共混比为70/30,硫磺用量为2.5份时NR/RR共混胶综合性能最佳。     

Reinforcing effect of nanosilica on the properties of natural rubber/reclaimed ground rubber tire vulcanizates

In this investigation, incorporation of silica into natural rubber (NR)‐reclaim rubber (RR) blend system was carried out by sol‐gel technique at various sol‐gel reaction temperatures. The effect of RR on silica reinforcement, hitherto unexplored, was studied for different NR/RR blend systems. The degree of reinforcement of sol‐gel vulcanizates by equilibrium swelling method indicates that the reinforcing efficiency of the in situ generated silica by sol‐gel technique increases with increasing reclaim rubber content. The reinforcing efficiency, tensile properties and thermal stability of sol gel vulcanizates (SGV) prepared at 50°C become maxima as compared to SGV prepared at 30°C and 70°C. The amount of silica incorporated by sol‐gel technique was determined by thermogravimetry analysis. It indicates that the thermal stability increases with silica content. Attenuated total reflection study indicates that RR forms bond with silica particles due to the presence of active functional site on RR. Scanning electron microscopy studies further indicate the coherency and homogeneity in the silica filled NR/RR vulcanizates. The microwave diagnosis of different SGVs was also carried out and the frequency dependence of dielectric permittivity (E') and loss (E”) were measured. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Studies on the adhesives for rubber to rubber bonding

Novel adhesive compounds for bonding natural rubber vulcanizates and NR/BR (natural rubber/polybutadiene) blend vulcanizates were developed. It has been shown that reclaimed latex waste can replace natural rubber in the adhesive, either partially or fully. The adhesives were found to retain their bond strength even after 5 weeks of aging at 30°C.     

Novel method for preparation of carboxylated nitrile rubber–natural rubber blends using bis(diisopropyl)thiophosphoryl polysulfides

Bis(diisopropyl)thiophosphoryl trisulfide (DIPTRI) and bis(diisopropyl)thiophosphoryl tetrasulfide (DIPTET) are successfully used as a novel coupling agent and accelerator, respectively, to covulcanize an elastomer blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar natural rubber (NR). These compounds are capable of forming a chemical link between these dissimilar rubbers to produce a technologically compatible blend as judged by a swelling experiment. The blend vulcanizates thus produced exhibit enhanced physical properties that can further be improved by adopting the two‐stage vulcanization technique and also by judicious selection of the NR:XNBR ratio. The blend morphology assessed by scanning electron microcroscopy micrographs accounts for significant improvement in the physical properties of the blend vulcanizates, particularly in two‐stage vulcanization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1725–1736, 2001     

Comparative behavior of in situ silica generation in saturated rubbers: EPDM and hydrogenated natural rubber

Role of carbon‐carbon double (C?C) bonds content and their position in ethylene‐propylene diene ter‐polymer (EPDM), hydrogenated natural rubber (HNR) and natural rubber (NR) on in situ silica formation using tetraethoxysilane (TEOS) as a silica precursor is comparatively investigated. Glass transition temperature (T_g ) reflecting rubber chain flexibility is found as an important factor for in situ silica generation via swelling method. Despite of similar solubility parameters, NR has higher TEOS‐swelling degree resulting in the higher in situ silica content (30.8 phr) than EPDM (3.50 phr) and HNR (10.4–17.6 phr) due to the higher T_g of EPDM and HNR providing the less chain flexibility to be swollen in TEOS solution. The morphological analysis implies that C?C bonds in saturated rubbers may be agglomeration sites for in situ silica particles. For practical applications, saturated rubbers containing in situ silica/NR vulcanizates showed the improvement of mechanical properties and resistance of thermal and ozone degradation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44748.     

NR原位改性炭黑对NR胶料性能的影响

分别采用高温转矩流变仪和常温两辊开炼机制备NR原位改性炭黑(GCB)和NR/炭黑共混物(KCB),并制备GCB/NR和KCB/NR硫化胶,对其性能进行研究.结果表明,与KCB相比,GCB的耐热性能提高,结合橡胶质量分数增大;当炭黑用量相同时,与KCB/NR硫化胶相比,GCB/NR硫化胶的交联密度、定伸应力、压缩永久变形和储能模量较大,拉伸强度和回弹值较小;当炭黑用量小于60份时,GCB/NR硫化胶耐疲劳性能优于KCB/NR硫化胶.     

聚磷酸三聚氰胺/季戊四醇膨胀型阻燃剂在天然橡胶中的应用

研究了膨胀型阻燃剂聚磷酸三聚氰胺（MPP）/季戊四醇（PER）对天然橡胶（NR）硫化胶的阻燃性能、热稳定性能、残炭形貌及力学性能的影响。结果表明,MPP/PER对NR硫化胶具有很好的阻燃效果,能有效提高NR复合材料的极限氧指数和热稳定性能,降低NR硫化胶的热释放速率,使NR硫化胶的燃烧过程变得稳定;当MPP/PER燃烧时可在NR硫化胶表面形成连续、致密且可隔绝氧气和热量的膨胀炭层;增加MPP/PER的总加入量会对NR硫化胶的力学性能造成一定的负面影响。     

液体聚丁二烯橡胶对顺丁橡胶/天然橡胶共混胶加工性能及抗疲劳性能的影响

考察了液体聚丁二烯橡胶Activ-50对顺丁橡胶(BR)/天然橡胶(NR)共混胶加工性能及抗疲劳性能的影响,并采用裂纹增长测试平台结合有限元ABAQUS/CAE,从疲劳裂纹扩展角度对硫化胶的抗疲劳性能进行了考察.结果表明,Activ-50能够降低混炼胶的储能模量和黏度,橡胶共混过程中加入Activ-50能改善体系的加工...     

Natural rubber–ethylene‐propylene‐diene rubber covulcanization: Effect of reinforcing fillers

Filled covulcanizates of elastomer blend comprising natural rubber (NR) and ethylene‐propylene‐diene rubber (EPDM) of commercial importance were successfully prepared by using a multifunctional rubber additive; namely, bis(diisopropyl)thiophosphoryl disulfide (DIPDIS). A Two‐stage vulcanization technique further improved the physicochemical properties of the blend vulcanizates by restricting, through the formation of polar rubber bound intermediates, the migration of curative and filler from lower to highly unsaturated rubber. Scanning electron microscopy studies indicate homogeneity and coherency in the morphology of the two‐stage vulcanizates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1001–1010, 2002; DOI 10.1002/app.10361