Unlubricated sliding and rolling wear of thermoplastic dynamic vulcanizates (Santoprene) against steel

The friction, sliding and rolling wear characteristics of thermoplastic dynamic vulcanizates (TPV; Santoprene^® grades), composed of polypropylene (PP), ethylene/propylene/diene rubber (EPDM) and extender oil, were studied against steel counterparts in dry condition. The composition and basic mechanical properties of the TPV of various hardness (Shore A = 60°, 70° and 80°) were evaluated. The wear performance of the TPVs was investigated in different tribotests, viz. pin-on-plate (POP), cylinder-on-plate (fretting) and rolling ball-on-plate (RBOP), whereby “plate” was always the rubber. From the above tests the coefficient of friction (COF) and specific wear rate were determined. It was established that with increasing hardness usually both COF and the specific wear rate were reduced. Values of the COF and wear rate depended strongly on the configuration and testing parameters of the related tribotests. The wear mechanisms were concluded by inspecting the worn surfaces by white light profilometry and scanning electron microscopy (SEM), respectively, and discussed.     

乙丙橡胶胶液失活洗涤工艺技术探讨

对Ziegle-Natta催化体系催化剂活性中心的结构和乙丙橡胶聚合反应后胶液中催化剂的存在形式进行了介绍,并对其失活反应的特性、洗涤过程中钒和铝化合物存在形式,以及工艺条件对失活洗涤过程的影响进行了探讨。     

A Comparative Study on Curing Characteristics,Mechanical Properties,Swelling Behavior,Thermal Stability,and Morphology of Feldspar and Silica in SMR L Vulcanizates

Abstract

Comparison studies on effects of feldspar and silica (Vulcasil C) as a filler in (SMR L grade natural rubber) vulcanizates on curing characteristics, mechanical properties, swelling behavior, thermal analysis, and morphology were examined. The incorporation of both fillers increases the scorch time, t ₂, and cure time, t ₉₀, of SMR L vulcanizates. At a similar filler loading, feldspar exhibited longer t ₂ and t ₉₀ but lower values of maximum torque, M_HR, and torque difference, M_HR–M_L than did silica-filled SMR L vulcanizates. For mechanical properties, both fillers were found to be effective in enhancing the tensile strength (up to 10 phr), tensile modulus, and hardness of the vulcanizates. However, feldspar-filled SMR L vulcanizates showed lower values of mechanical properties than did silica-filled SMR L vulcanizates. Swelling measurement indicates that swelling percentages of both fillers-filled SMR L vulcanizates decrease with increasing filler loading whereas silica shows a lower swelling percentage than feldspar-filled SMR L vulcanizates. Scanning electron microscopy (SEM) on fracture surface of tensile samples showed poor filler–matrix adhesion for both fillers with increasing filler loading in the vulcanizates. However, feldspar-filled SMR L vulcanizates showed poorer filler–matrix adhesion than did silica-filled SMR L vulcanizates. Thermogravimetric analysis (TGA) results indicate that the feldspar-filled SMR L vulcanizates have higher thermal stability than do silica-filled SMR L vulcanizates.     

Thermal Aging Properties and Molecular Transport of Solvents through Vulcanizates Prepared from Thioglycollic Acid Modified Epoxidized Low Molecular Weight Natural Rubber Blends Filled with Admixtures of Carbon Black and Carbonized Rubber Seed Shell

Physico-mechanical, aging, swelling, solubility, and permeability properties of blends of natural rubber and thioglycollic acid modified epoxidized low molecular weight natural rubber (TGA-ELMWNR) filled with admixtures of carbon black and carbonized rubber seed shell (CRSS) in ketones, alcohols, aldehydes, and petroleum fuels (petrol, kerosene, and diesel) were investigated as a function of different filler composition. The physico-mechanical properties were found reducing as the level of CRSS increases, but were within the accepted level for natural rubber compounds, showing that CRSS can find uses as fillers in materials of low tensile strength. The aging results of all the mixes were nearly of the same magnitude. The swelling and solubility results showed that ketones swell the vulcanizates more and faster than alcohols and than aldehydes. The sorption, diffusion, and permeability of the blends as determined by the gravimetric method confirm the better resistance of blends with higher ratio of carbon black. Petrol was found diffusing through the vulcanizates faster than kerosene and faster than diesel. Above all, replacement of carbon black with 15% carbonized rubber seed shell has not shown any serious deleterious effects on the vulcanizates.     

Modified phosphate pigments as high performance reinforcing materials for rubber vulcanizates

This study is focusing on the synthesis of novel modified micronized phosphate pigments as reinforcing materials for the vulcanizates of styrene-butadiene rubber (SBR), natural rubber (NR) and their blends. The metal phenyl phosphate pigments were prepared via co-precipitation process from the reaction of equimolar ratios of the disodium phenyl phosphate solution and the water soluble salts of the investigated metals. The white prepared phosphate pigments were introduced in the rubber formulations to replace carbon black the highly common and commercial reinforcing material in rubber vulcanizates. The rheometric characteristics, physico-mechanical properties in addition to the accelerated aging properties of the rubber vulcanizates were investigated, discussed and interpreted in the light of previous studies. The results showed that, phenyl phosphate pigments exercised a great effect on the rheological characteristics (scorch time, cure time…etc.), and achieved high performance and pronounced mechanical properties. The stress and strain at yield and at rupture of the loaded rubber with modified phosphates are better than that loaded with carbon black and Hisil e.g. tensile strength data were (20.0–23.4), 18.01 MPa and 15.05 for rubber blend vulcanizates loaded with 30 phr of modified phosphate pigments, carbon black and Hisil, respectively.     

Studies on blends of ethylene vinyl acetate and polyacrylic rubber with reference to their shrinkability

Preferential crosslinking was introduced in the rubber phase of a blend of ethylene vinyl acetate (EVA) and polyacrylic rubber (AR‐801). The heat shrinkability of the polymer blends was measured at room temperature (RT) and at a high temperature (HT) of 150°C. Various parameters were tried for a correlation with shrinkability. Shrinkability goes up with the increase in rubber content and is increased with increasing cure time in blends of a fixed ratio. The crystallinity of an HT (at 150°C) stretched sample was higher than that of a RT stretched sample, which was higher than that of the shrunk and original sample. The continuous cure characteristics, showed that the torque was increased with the rubber content. High temperature DSC demonstrated that the increase in AR‐801 content decreased the stability and further HT processing increased the stability. SEM showed that the rubber phase was more elongated in the HT stretched sample compared to the RT stretched sample. In the shrunk sample the rubber phase was more globular. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2088–2095, 2000     

辅助增塑剂环氧大豆油对丁腈橡胶/聚丙烯热塑性硫化胶性能的影响

研究了辅助增塑剂环氧大豆油对以偏苯三甲酸三辛酯为主增塑剂的丁腈橡胶/聚丙烯热塑性硫化胶的硫化过程、耐油性能及流变性能的影响。结果表明,加入少量环氧大豆油,较单独使用偏苯三甲酸三辛酯可制备出具有更低硬度、高耐油性和流动性好的热塑性硫化胶。环氧大豆油可使丁腈橡胶/聚丙烯热塑性硫化胶制品的表面更加光滑,保护其不被氧化,令其色泽更加鲜艳和透明。     

Effect of fillers and vulcanizing systems on the physicomechanical and electrical properties of EPDM vulcanizates

The physicomechanical and dielectric properties were investigated for ethylene propylene diene terpolymer (EPDM) rubber loaded with different white fillers, namely, kaolin, quartz, polyvinylchloride PVC, and talc. The white fillers were added at a fixed level of 20 phr. Two vulcanizing systems were used, tetramethyl thiuram disulfide (TMTD) and sulfur/N-cyclohexyl-2-benzothiazyl sulfenamide (S/CBS). It was found that the curing systems affect the dielectric properties more than the filler type. The effect of the curing system and type of filler on the physicomechanical properties before and after thermal aging were also investigated, and the data obtained were interpreted.     

Morphological evolution and property changes of acrylate rubber/polyacetal thermoplastic vulcanizates during dynamic vulcanization process

A new type of thermoplastic vulcanizates (TPV) that is resistant to hot oil, high temperature, and aging was prepared using acrylate elastomer (ACM) and polyoxymethylene (POM) as raw materials. The phase transition process and micromorphology development of the blends with the change of dynamic vulcanization (DV) time, and to illustrate the effects of the phase transition and the degree of elastomer phase crosslinking on the macroscopic properties of TPV were investigated. It was shown that ACM crosslinking occurs continuously during 0–8 min of DV, whereas the phase inversion process occurs predominantly during 0–3 min. In contrast, the cross-section of the blends after phase inversion is flat, The constant elongation stress under small deformation, hardness, and permanent deformation after break are reduced, and the elongation at break, nonrelaxable modulus, and aging resistance are improved. The increase in the degree of vulcanization of the ACM phase resulted in a significant increase in the modulus of the blends under large deformation, an increase in the nonrelaxable modulus and relaxable modulus, an increase in the aging resistance, and a decrease in the elongation at tear were observed.