Sorption and diffusion of n-alkanes into bromobutyl rubber membranes

Sorption and diffusion of n-alkanes into bromobutyl rubber membranes were investigated in the temperature interval 25–60°C by a sorption gravimetric method. The Fickian diffusion equation was used to calculate the diffusion coefficients, which were dependent on the size of the alkanes, their interactions with the chain segments of the polymer and temperature. The diffusion coefficients varied from 0.34×10^?7 cm²/s (n-hexadecane) to 9.94×10^?7 cm²/s (n-hexane). The activation energy for diffusion varied from 14kJ/mol (n-hexane) heptane to 2.0kJ/mol for n-hexadecane. The sorption/swelling results are discussed in terms of first and second order kinetic equations. The molar mass between chain-entanglement-crosslinks was estimated from swelling data. The experimental and calculated results showed a systematic dependence on the increasing size of the alkanes. None of the solvents showed any degradative effects on the polymer.     

Sorption/desorption and diffusion kinetics of ketones and nitriles into fluoropolymer membranes

Analysis of sorption/desorption and diffusion kinetics of ketones and nitriles at 25, 44, and 60°C into three Du Pont's VITON fluoropolymer membranes loaded with different amounts of carbon black has been undertaken by use of a sorption/desorption technique. The transport results are affected by the percent loading of carbon blacks. Diffusion coefficients have been calculated from Fick's equation. These results show a decrease with increasing amount of carbon black. Experimental results have been analyzed by considering swelling of the membranes. Sorption/desorption results have been analyzed from a calculation of the concentration profiles, which are obtained from the analytical solution of Fick's equation. These results have been compared with a numerical solution based on the finite difference method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 635–647, 1997     

Sorption and diffusion of aldehydes and ketones through castor oil-based interpenetrating polymer networks of PU–PS

Sorption and diffusion of some aldehydes and ketones into interpenetrating polymer networks (IPNs) of polyurethane–polystyrene (PU–PS) have been investigated in the temperature interval of 25–60°C. Transport data were found to be affected by the nature of the interacting solvent molecule rather than its size. The diffusion coefficient of ketones range from 9.2 × 10⁻⁸ to 645 × 10⁻⁸ cm²/s and for aldehyde from 11.5 × 10⁻⁸ to 154.5 × 10⁻⁸ cm²/s. For all solvents, the polymer remained intact. From the temperature dependence of sorption data, the Arrhenius activation parameter and the thermodynamic parameter, such as entropy and enthalpy for the process of equilibrium sorption, have been estimated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2047–2055, 1998     

Thermal behavior of natural rubber and chlorinated rubber blends

A solid-state chemical reaction occurs when a solvent cast film of a blend of masticated natural rubber and chlorinated natural rubber is heated in the presence of air at 150°C. The thermal behavior of solvent cast films of chlorinated natural rubber, masticated natural rubber, and a 1 : 1 w/w blend (2% w/v in xylene) of these two polymers has been studied using differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, and nuclear magnetic spectroscopy. The results suggest that carbonyl groups are incorporated into the blend on heating and that the vinyl functionality of the isoprene units is modified during this apparent oxidation. Heating for 2 h at 150°C results in a material that no longer contains the rubber-like cis-1,4-polyisoprene units. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1379–1384, 1997     

Sorption,desorption, diffusion,and permeation of aliphatic alkanes into santoprene thermoplastic rubber

The molecular transport characteristics of Santoprene rubber in the presence of n-alkanes, cyclohexane, 2,2,4-trimethylpentane, and 1,2,3,4-tetrahydronaphthalene at 25, 40, 55, and 70°C have been studied using a sorption gravimetric technique. From the sorption and desorption studies, the diffusion coefficients have been calculated and used in the discussion of the transport results. It was observed that these data depend on the size of the penetrants. Furthermore, efforts were made to evaluate the permeation coefficients, molar mass between crosslinks, and the kinetic rate constants. These data showed a systematic dependence on the penetrant size. Activation parameters for the process of diffusion and permeation have been calculated from the temperature dependence of the transport coefficients. © 1995 John Wiley & Sons, Inc.     

活性预处理三元乙丙橡胶/天然橡胶并用胶的性能

采用硫载体硫化剂4,4′-二硫化二吗啉(DTDM)对三元乙丙橡胶(EPDM)进行活性预处理,研究了活性预处理EPDM/天然橡胶(NR)并用胶的性能,并探讨了活性预处理EPDM对并用胶力学性能影响的机理。结果表明,预处理EPDM/NR并用胶的共硫化程度得到改善,并用硫化胶的力学性能提高;并用硫化胶的耐老化性能优于NR硫化胶,但比未处理EPDM/NR并用硫化胶差;并用胶只存在1个玻璃化温度的转变区,两相的相容性得到改善;在高温动态条件下,EPDM与DTDM发生活性反应,但未生成大量凝胶。     

Thermoplastic elastomers-based natural rubber and thermoplastic polyurethane blends

Thermoplastic elastomers based on the blends of thermoplastic polyurethane (TPU) and natural rubber were prepared by a simple blend technique. The influence of the two different types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends was investigated. The main aim of this study was to improve heat resistance and damping properties, and also to prepare the TPU material with low hardness by blending with various amounts of natural rubber. It was found that the TPU/ENR blends exhibited superior modulus, hardness, shear viscosity, stress relaxation behavior and heat-resistant properties compared to the blends with TPU and unmodified NR. This was attributed to higher chemical interaction between the polar functional groups of ENR and TPU by improving the interfacial adhesion. It was also found that the ENR/TPU blends exhibited finer grain morphology than the blends with unmodified NR. Furthermore, lower tension set, damping factor (Tan ??) and hardness, but higher degradation temperature, were observed in natural rubber/TPU blends compared to pure TPU. This proves the formation of TPU material with high heat resistance, low hardness and better damping properties. However, the blends with higher proportion of natural rubber exhibited lower tensile strength and elongation at break.     

Sorption and diffusion of acrylonitrile monomer through crosslinked nitrile rubber

As the first step for the preparation of interpenetrating polymer networks from nitrile rubber and polyacrylonitrile, the sorption and diffusion of acrylonitrile monomer through nitrile rubber crosslinked by three different vulcanization systems—conventional (CV), dicumyl peroxide (DCP), and a mixture consisting of sulfur and peroxide (mixed)—were studied in the temperature interval of 30–70°C. Kinetic curves have been generated for these systems to compute diffusion and sorption coefficients. The equilibrium sorption is found to be maximum for the CV system. The molar mass between crosslinks (M_c) has estimated and compared with affine and phantom models. It was found that the M_c values follow the affine model. The diffusion coefficient values are highest for DCP and lowest for CV. It was observed that the kinetics of liquid sorption followed an anomalous behavior. The temperature dependence of the transport parameters was followed by an Arrhenius relationship, from which the activation energy for diffusion, permeation, and sorption were calculated. It is found that temperature activates diffusion in all cases. The polymer–solvent interaction parameter was determined. The amount of polysulfidic linkages in the rubber network was also estimated. The experimental results were compared with theoretical predictions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 941–952, 2000     

Reactive extrusion of PP/natural rubber blends

Reactive extrusion of polypropylene (PP)/natural rubber (NR) (90/10) blends was conducted in the presence of a peroxide [1,3-bis(t-butylperoxy)benzene] and coagent (trimethylolpropanetriacrylate, TMPTA). Effects of peroxide and coagent content were studied in terms of melt index (MI), melt viscosity, morphology, thermal, and mechanical properties. At a constant content of the coagent, melt viscosity increased at a low and decreased at a high content of the peroxide. On the other hand, melt viscosity increased monotonically with the coagent concentration at constant peroxide content. The increase and decrease of viscosity were interpreted in terms of crosslinking and chain scission of PP, which governed the rubber domain size and mechanical properties of the reactive blends. © 1995 John Wiley & Sons, Inc.     

Viscosity behavior of PVC-modified liquid natural rubber blends

Compatibility of poly(vinyl chloride) (PVC) with liquid natural rubber (LNR) and epoxidized liquid natural rubber (ELNR) has been studied by solution viscometric methods. The relative viscosity versus composition plots for PVC/LNR and PVC/ELNR-20 blends are found to be nonlinear. The corresponding intrinsic viscosity values show negative deviation from ideal behavior when plotted against composition. The modified Krigbaum and Wall parameter, Δb, also shows negative values for all compositions of these blends studied. The results indicate that PVC/LNR and PVC/ELNR-20 blends are incompatible systems. On the other hand, PVC/ELNR-50 blends yielded linear plots when relative viscosity was plotted against composition. The intrinsic viscosity composition plots for this system showed positive deviation from ideal behavior. The δb values are positive for all compositions of these blends studied. These results are characteristic of a compatible blend system. Hence it is concluded that liquid natural rubber can be made compatible with PVC when the former is epoxidized to a sufficient level. © 1996 John Wiley & Sons, Inc.     

Epoxidized natural rubber/dicarboxylic acid self-vulcanized blends

Curing behaviour as well as mechanical properties of binary blends of epoxidized natural rubber (ENR) and dodecanedioic acid (DA) were investigated for development of self-vulcanizable elastomer blends. Cross-linking reaction at 180 °C of reactive functional rubber containing 25 and 10 mol% epoxide groups was followed by rheology. The properties of the cured materials were studied by dynamic mechanical analysis, stress-strain experiments, and DSC measurements. It was shown that a specific ratio ENR/DA gave rise to optimum mechanical properties. This ratio decreases together with the epoxidation level of the rubber. DSC measurements revealed that the glass transition temperature of the cured material increases nonlinearly at high concentrations of cross-linking agent. By comparing cross-linking with DA and reaction with monofunctional lauric acid, this behaviour was attributed to polar interactions due to free carboxylic groups of pending diacid grafts.     

环氧化天然橡胶共混物与复合材料

综述了国内外环氧化天然橡胶(ENR)共混物与复合材料的研究现状和应用发展趋势。介绍了几种环氧化天然橡胶共混物与复合材料的优点及影响其性能的因素。     

Studies on polymer blends: Blending methods for natural rubber and styrene-butadiene rubber

The relations between the properties and the blend ratios of natural rubber (NR) and styrene-butadiene rubber (SBR) blends were studied in comparison with four blending methods. The relations between the properties of unvulcanized and vulcanized blends and the blend ratios of blends prepared by means of solution blending, latex blending, roll blending, and Banbury mixer blending were studied. In practice, such rubber blending methods as roll blending are more effective for obtaining uniform blends than Banbury mixer blending the latter. In roll blending, it is more effective to blend NR and SBR by way of a master-batch in which the ingredients are compounded beforehand than to blend raw rubber. In solution and latex blending, very uniform blends are easily obtained. It was found, however, that the properties of NR/SBR blends prepared carefully showed a direct relation to their blend ratios, regardless of blending method used.     

聚乙烯醇/天然橡胶共混物的制备及其性能研究

利用环氧化天然胶乳作为界面改性剂,采用胶乳共混法将聚乙烯醇（PVA）溶液同天然胶乳进行混溶,制备了PVA/天然橡胶（NR）的共混物,通过电子万能材料试验机、动态热机械分析仪、热老化箱和臭氧老化箱,研究了共混物力学性能、玻璃化转变温度、老化性能以及耐溶剂抽出性。结果表明,PVA的加入明显提高了NR的撕裂强度和硬度,而共混物的拉伸强度和断裂伸长率随着PVA含量的增加都出现下降的趋势;随着PVA含量的增加,NR的玻璃化转变温度呈现先增加后降低的趋势;随着PVA含量增加,共混物各试样对乙醇的耐抽出能力相差不大,对水的耐抽出能力逐步变弱。热空气老化对材料的力学性能影响明显,而臭氧老化由于时间较短,对材料的力学性能影响不明显。老化实验对材料的性能变化率影响显著。     

环氧化天然橡胶共交联改性EPDM/NR共混物的性能

将三元乙丙橡胶(EPDM)与环氧化天然橡胶(ENR)共交联改性后,再与天然橡胶(NR)共混,考察了ENR共交联改性EPDM/NR共混胶的硫化特性、硫化胶的物理机械性能、溶胀指数和耐热空气老化性能,并对该硫化胶进行了差示扫描量热分析。结果表明,EPDM经过ENR共交联改性后与NR共混,ENR共交联改性EPDM/NR共混胶的交联程度明显提高,各相达到了同步交联,硫化胶的综合性能得到了显著改善。     

Rheological behavior of blends of natural rubber and styrene–butadiene rubber latices

The rheological behavior of blends of natural rubber (NR) and styrene–butadiene rubber (SBR) latices has been studied with reference to the effects of blend ratio, shear rate, surface-active agents (casein and sodium carboxymethyl cellulose), and temperature. When the SBR content was less than 50%, the viscosities of the blends appeared to be a nonadditive function of the viscosities of the constituent homopolymers; i.e., a positive deviation was observed. This was due to the structural buildup of the SBR domains. The SBR domains underwent agglomeration and consequently so-called microflocculation took place. The viscosities of all the blends were found to decrease with increase of temperature and shear rate. The increase in temperature and shear rate marginally weakened the structural buildup as evidenced by the lowering of viscosity. As the SBR content in the system increased, the pseudoplasticity of the blend increased. Even in the presence of surface-active agents the blends showed composition-dependent positive deviation. However, surface-active agents marginally reduced the extent of structural buildup by reducing the microflocculation behavior of SBR domains. © 1995 John Wiley & Sons, Inc.     

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。     

Improvement of the compatibility of natural rubber/ethylene–propylene diene monomer rubber blends via natural rubber epoxidation

The longitudinal ultrasonic velocity, longitudinal ultrasonic absorption (attenuation coefficient), glass‐transition temperature, and Mooney viscosity for epoxidized natural rubber/ethylene–propylene diene monomer blends were measured. The variation of the longitudinal ultrasonic velocity with the blend ratios was linear, indicating a compatible system in comparison with the same system without epoxidation (natural rubber/ethylene–propylene diene monomer), which was incompatible. Also, the behavior was confirmed by heat of mixing calculations as well as Mooney viscosity measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2816–2819, 2002     

Quantitative analysis of natural rubber,polybutadiene rubber and styrene/butadiene rubber blends by infra-red spectroscopy

Summary Infra-red spectra of natural rubber (NR), polybutadiene rubber (PBR) and styrene butadiene rubber (SBR) have been studied for the estimation of these polymers in ternary rubber blends. A study of different infra-red active bands suggests that the bands at 1316 Cm^–1, 1379 Cm^–1 and 1493 Cm^–1 are most appropriate for quantitative purpose. A detailed analysis of observed data has been made and based on this analysis, formulae for the estimation of these rubbers have been deduced.IPCL communication No:71Authors acknowledge the experimental assistance rendered by Mr.J.B. Solanki     

液体异戊橡胶对顺丁橡胶/天然橡胶共混胶性能的影响

考察了分别用自制的液体异戊橡胶和液体异戊橡胶LIR-50等量取代顺丁橡胶/天然橡胶共混胶中的天然橡胶部分时对共混胶性能的影响。结果表明,液体异戊橡胶的加入对于共混胶料的抗湿滑性能有所改善,但同时也增大滚动阻力。随着液体异戊橡胶用量(5~15份)的增加,共混硫化胶的拉伸强度、撕裂强度和扯断伸长率稍有下降,磨耗量和生热有所增大。2种液体异戊橡胶的使用效果相当。