The effects of technological compatibility for silicone rubber/fluororubber blends

In this study, silicone rubber (SR) and fluororubber (FKM) blends were prepared and their properties were investigated. The crosslinking rate in the blends was increased with increase of SR content due to the silica filler existing into SR. As the content of FKM in the blends increases, the thermal decomposition temperature of the blends tended to increase and the thermal stability of 25/75 SR/FKM blend was higher than that of any other blends ratios. With the increase of FKM content in the blends, the contact angle of SR/FKM blends decreased and the surface energy increased owing to the change of the polarity of the surface. Dynamic mechanical analysis of 25/75 SR/FKM blend showed two transitions peak at −60.5 and −12.7°C, respectively, indicating the immiscibility. Fourier transform infrared attenuated total reflectance studies showed shifts in the peaks due to specific interactions in the blends, and field emission scanning electron microscopy (FE-SEM) studies revealed that the domain sizes of the blends come to be smaller with increasing FKM content. In the blend with 75 wt % of FKM, we observed that it is technologically compatible due to the increase of physical properties and the decrease of the domain size of FE-SEM in 25/75 SR/FKM blend. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

氟橡胶/甲基乙烯基硅橡胶共混弹性体的性能

通过机械共混法制备了氟橡胶(FKM)/甲基乙烯基硅橡胶(MVQ)弹性体,研究了二者的质量比对共混弹性体力学性能、耐油性能和动态力学性能的影响.结果表明,当FKM/MVQ(质量比,下同)为80/20时,共混弹性体具有较好的综合力学性能.随着FKM所占比例的增加,共混弹性体的耐油性能提高.当振动频率为1 Hz时,共混弹性体中MVQ相的玻璃化转变温度(Tg)比MVQ的Tg提高了约5.0 ℃,而FKM相的Tg改变不大;当FKM/MVQ为60/40时,随着振动频率由1 Hz增大到50 Hz,FKM相的Tg升高了12.9 ℃,而MVQ相的Tg变化不大.     

Effects of waste ground fluororubber vulcanizate powders on the properties of silicone rubber/fluororubber blends

We prepared fluororubber (FKM) vulcanizate powder (FVP) via cryogenic grinding of the FKM commonly used in automobiles and assessed the particle size distribution of the resulting powder. We also prepared silicone rubber (SR)/FKM blends at a ratio of 25/75. Varying amounts of FKM were replaced with equal amounts of FVP within the range of 5–40 wt%, and the physical properties of the resulting SR/FKM/FVP blends were investigated and compared. The TGA curves of the SR/FKM/FVP blends obtained during the thermal property investigations indicated that pyrolysis of SR occurred within two temperature ranges, and that the SR/FKM/FVP blends with 5 wt% FVP demonstrated the highest thermal stability. The storage modulus (E') and loss modulus (E″) of the SR/ FKM/FVP blends increased as the FVP content increased. In the SR/FKM/FVP blends with 5 and 10 wt% FVP, very typical elastic‐deformation behavior was observed. On the contrary, in 40 wt% FVP, the rubber properties disappeared. The mean particle size of FVP was 41.75 μm, and particle size distribution measurements of the SR/FKM/FVP blends suggest particle coexistence such that FVP was condensed and separated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

再生硅橡胶/甲基乙烯基硅橡胶共混物的性能

采用机械剪切破碎法制备再生硅橡胶,并将其掺入到甲基乙烯基硅橡胶中制备再生硅橡胶/硅橡胶共混物,研究了再生硅橡胶含量、硫化促进剂2,5-双(叔丁基过氧化)-2,5-二甲基己烷和沉淀法白炭黑用量对共混物硫化特性和力学性能的影响,通过傅里叶变换红外光谱、动态力学分析仪和扫描电子显微镜对共混物和硅橡胶进行了分析。结果表明,随着共混物中再生硅橡胶含量的增加,共混物的硫化速率变慢,力学性能降低,当再生硅橡胶质量分数为46.9%时,共混物的综合力学性能较好。当2,5-双(叔丁基过氧化)-2,5-二甲基己烷用量为0.5份(质量)且沉淀法白炭黑用量为15份时,共混物具有良好的力学性能。机械剪切破碎法没有引起再生硅橡胶化学性质的变化;共混物的玻璃化转变温度与硅橡胶接近,但其损耗因子峰值下降;共混物中填料的分散均匀性介于再生硅橡胶与硅橡胶之间。     

活化改性废硅橡胶与EPDM共混的研究

采用六亚甲基四胺与氯化铁/氯化亚铁混合物作为废硅橡胶的活化改性剂，以活化改性后的废硅橡胶与EPDM共混，研究活化改性剂添加方式及活化改性废硅橡胶用量对共混物物理性能的影响。结果表明，活化改性剂与废硅橡胶先预炼的活化效果较好，EPDM/活化改性废硅橡胶共混比为90/10时共混物的综合性能较好。     

Thermoplastic elastomers based on high‐density polyethylene,ethylene–propylene–diene terpolymer,and ground tire rubber dynamically vulcanized with dicumyl peroxide

Thermoplastic vulcanizates (TPVs) based on high‐density polyethylene (HDPE), ethylene–propylene–diene terpolymer (EPDM), and ground tire rubber (GTR) were dynamically vulcanized with dicumyl peroxide (DCP). The polymer blend was composed of 40% HDPE, 30% EPDM, and 30% GTR, and the concentration of DCP was varied from 0.3 to 3.6 parts per hundred rubber (phr). The properties of the TPVs were determined by evaluation of the gel fraction content and the mechanical properties. In addition, IR spectroscopy and differential scanning calorimetry analysis were performed as a function of the DCP content. Decreases in the Young's modulus of the blends and the crystallinity of HDPE were observed when the content of DCP was greater than 1.8 phr. The results regarding the gel content indicate that the presence of DCP promoted the crosslinking of the thermoplastic matrix, and optimal properties were obtained with 1.5% DCP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39901.     

Rheological behavior and processability of polypropylene blends with rubber ethylene propylene diene terpolymer

A study of the dynamic complex and steady shear viscosity of isotactic polypropylene (iPP), ethylene–propylene diene terpolymer rubber (EPDM) and three different blends of both polymers are presented over a range of temperatures and frequencies. Moreover, the processability of these materials is studied through torque measurements during blend mixing. The results obtained show that the viscosity gradually increases with rubber content in the blend and decreases with both temperature and frequency. Plots of η″ versus η′ (Cole–Cole plots) show that the blend with the lower rubber content (25%), has a certain rheological compatibility with neat PP. Furthermore, torque curves measured during blend mixing confirm these results, demonstrating that the blend with 25% of elastomer has a similar behavior of iPP during processing. To analyze the morphological structure of the blends, a dynamic mechanical analysis of the solid state is also presented. It is observed that the blends have two distinct values of T_g close to the corresponding values of the pure polymers, confirming that this type of blends based on a semicrystalline polymer and an amorphous elastomer forms a two‐phase system with a limited degree of miscibility between both components. In addition, the polymer present with the higher concentration forms the continuous phase and controls the rheological properties of the blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1–10, 2001     

顺丁橡胶对硅橡胶/丙烯酸酯橡胶并用胶的增容作用

采用偏光显微镜、差示扫描量热仪以及力学性能、热老化性能测试手段,研究了顺丁橡胶(BR)增容的甲基乙烯基硅橡胶(MVQ)/丙烯酸酯橡胶(ACM)共混体系的并用比(质量比)、硫化工艺参数以及BR的加入对并用胶力学性能、耐热老化性能和相容性的影响。结果表明,BR的加入改善了MVQ/ACM并用胶的力学性能和耐热老化性能,当白炭黑用量为30份、BR/MVQ/ACM的并用比为25/45/55时,并用胶的力学性能和耐热老化性能最好;最佳硫化工艺参数为70℃×10 MPa×30 min;加入BR可以改善MVQ/ACM并用胶的相容性,且使其玻璃化转变温度降低,耐低温性能提高。     

Preparation of thermoplastic vulcanizates based on waste crosslinked polyethylene and ground tire rubber through dynamic vulcanization

An environmental‐friendly approach called high‐shear mechanical milling was developed to de‐crosslink ground tire rubber (GTR) and waste crosslinked polyethylene (XLPE). The realization of partial devulcanization of GTR and de‐crosslinking of XLPE were confirmed by gel fraction measurements. Fourier transform infrared spectral studies revealed that a new peak at 1723.3 cm^?1 corresponds to the carbonyl group (? C?O) absorption was appeared after milling. The rheological properties showed that the XLPE/GTR blends represent lower apparent viscosity after mechanical milling, which means that the milled blends are easy to process. Thermoplastic vulcanizates (TPVs) could be prepared with these partially de‐crosslinked XLPE/GTR composite powders through dynamic vulcanization. The mechanical properties of the XLPE/GTR composites increased with increasing cycles of milling. The raw XLPE/GTR blends could not be processed to a continuous sheet. After 20 cycles of milling, the tensile strength and elongation at break of XLPE/GTR (50/50) composites increased to 6.0 MPa and 185.3%, respectively. The tensile strength and elongation at break of the composites have been further improved to 9.1 MPa and 201.2% after dynamic vulcanization, respectively. Re‐processability study confirmed the good thermoplastic processability of the TPVs prepared. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of fluorine interface to the crystallization of poly (vinylidene fluoride)/silicone rubber/fluororubber elastomeric tertiary blends via dynamical curing

ABSTRACT

We demonstrate the influence of fluorine interface to the crystallization of poly(vinylidene fluoride) (PVDF)/silicone rubber (SR)/fluororubber (FKM) tertiary dynamic curing blends. In contrast to PVDF/SR binary blend, the average size of PVDF spherulites turns smaller and the crystallization rate is lower in PVDF/SR/FKM tertiary blend when more fluororubber component was added into the blends at the same crystallization temperature. Incorporation of FKM does not change the crystalline form of PVDF in the blends. The resulting mechanical properties of tensile strength, flexural strength, Izod impact strength and elongation at break for PVDF/SR/FKM tertiary blends are enhanced compared with PVDF/SR binary blend.     

Effects of blend ratio and vulcanizate powders on the processability of silicone rubber/fluororubber blends

While silicone rubber has a much lower shear viscosity than that of fluororubber, the viscosity of silicone rubber/fluororubber blends is closer to that of silicone rubber. All rubber compositions show pseudoplastic behavior. While the viscosity of a 50/50 silicone rubber/fluororubber blend increases on replacement of the silicone rubber by silicone rubber vulcanizate powder (SVP), the effect of fluororubber replacement by the corresponding fluororubber vulcanizate powder (FVP) on the shear viscosity is less pronounced. The difference in viscosity between SVP‐replaced silicone rubber and FVP‐replaced fluororubber becomes less prominent at higher shear rates. Fluororubber exhibits a higher extrudate die swell than that of silicone rubber. The die swell of the silicone rubber/fluororubber blends is higher than are the figures obtained by the additivity rule. Replacement of constituent rubbers in the blend by the corresponding vulcanizate powders causes an increase in the die swell. While the silicone rubber extrudate surface is smooth, the fluororubber extrudate shows melt fracture. The extrudate surfaces of the silicone rubber/fluororubber blends are similar to that of the silicone rubber extrudate. Replacement of constituent rubbers by the corresponding vulcanizate powders increases the roughness of the extrudate surface, which is more prominent in the case of silicone rubber replacement by SVP. SVP can replace 50% of silicone rubber and FVP can replace 75% of fluororubber in the 50/50 silicone rubber/fluororubber blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2377–2387, 2003     

共混比对氟橡胶氟硅橡胶共混胶性能的影响

氟橡胶是一种主链及侧链上的碳上连接有氟原子的一种合成高分子弹性体。氟橡胶具有优异的耐油、耐高温、耐酸碱、耐高真空等性能,同时由于氟原子的存在,使分子链极性增加、耐低温性能变差,这极大限制了氟橡胶的应用范围。笔者拟通过将其与氟硅橡胶共混来改进氟橡胶低温性能。我们选用苏威公司生产型号为PL958的氟橡胶,该规格氟橡胶具有自由基硫化反应位点,可以与氟硅橡胶实现共硫化。结果表明,氟橡胶/氟硅橡胶共混比为8:2时,共混胶具有优异的综合性能。     

Recycling of EPDM waste. II. Replacement of virgin rubber by ground EPDM vulcanizate in EPDM/PP thermoplastic elastomeric composition

Virgin ethylene propylene diene monomer (EPDM) rubber in a thermoplastic elastomeric blend of polypropylene (PP) and EPDM rubber was substituted by ground EPDM vulcanizate of known composition, after which the mechanical properties of the raw EPDM/waste EPDM/PP blends were determined. The ratio of the rubber content in the waste EPDM (r‐W‐EPDM) to the raw EPDM (R‐EPDM) in the blends was varied from 0 : 100 to 45 : 55. Attempts to replace higher amounts (>45%) of R‐EPDM by W‐EPDM failed because of processing difficulty. Although a drop in mechanical properties of the blends was observed at lower loadings of W‐EPDM, the properties showed improvement at intermediate W‐EPDM loadings. The R‐EPDM/W–EPDM/PP blends were found to be reprocessable. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3304–3312, 2001     

硅橡胶/EPDM泡沫合金材料的结构与性能

分别采用电镜和激光共聚焦显微镜研究了硅橡胶／EPDM泡沫合金的结构均匀性和泡孔结构,并进行强伸性能,压缩性能和阻尼减震性能的研究,结果表明,采用硅烷偶联剂后,硅橡胶／EPDM共混物的分散均匀性较好;泡沫合金的密度小于0．55Mg.m^-3,泡孔均匀,平均孔径小于80um,且泡沫合金的拉伸强度,压缩性能和阻尼减震性能优于硅橡胶泡沫。     

Recycling of ethylene propylene diene monomer (EPDM) waste. III. Processability of EPDM rubber compound containing ground EPDM vulcanizates

The rheological behavior of ethylene propylene diene monomer (EPDM) compounds containing ground EPDM waste (W‐EPDM) of known composition was studied by using a Monsanto processability tester in a temperature range of 90–110°C and a shear rate range of 306.7–1533.24 s^?1. It is found that the shear viscosity decreases slightly with increasing W‐EPDM loading because of wall slip that results from the migration of lubricants from the W‐EPDM. The addition of W‐EPDM to raw EPDM results in a decreased die swell at all temperatures and shear rates. SEM photomicrographs of the EPDM extrudate surface show improved surface smoothness and reduced extrudate distortion when EPDM is blended with W‐EPDM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2204–2215, 2003     

Recycling of EPDM waste. I. Effect of ground EPDM vulcanizate on properties of EPDM rubber

Processing, cure characteristics, and mechanical properties of EPDM rubber containing ground EPDM vulcanizate of known composition were studied. Mooney viscosity increases and Mooney scorch time decreases by the addition of the ground vulcanizate. At higher loadings of the ground rubber, the maximum rheometric torque decreases. On addition of ground waste, stress–strain properties and tear resistance increase, whereas heat buildup marginally increases, resilience marginally decreases, low‐strain modulus remains constant, and abrasion resistance decreases. The interplay between the filler effect of the ground EPDM and the crosslink density changes of the EPDM matrix is believed to be the reason for the variation in mechanical properties. It is believed that sulfur migration occurs from the raw EPDM matrix (R‐EPDM) to the ground waste EPDM (W‐EPDM) particle while accelerator migration occurs from W‐EPDM to R‐EPDM. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3293–3303, 2001     

Thermoplastic vulcanizates based on poly(methyl methacrylate)/epoxidized natural rubber blends: Mechanical,thermal, and morphological properties

Epoxidized natural rubbers (ENRs) with epoxide levels of 10, 20, 30, 40 and 50 mol % were prepared. The ENRs were later used to prepare thermoplastic vulcanizates (TPVs) by blending them with poly(methyl methacrylate) (PMMA) using various formulations. Dynamic vulcanization, using sulfur as a vulcanizing agent, was performed during the mixing process. The mixing torque increased as the ENR contents and epoxide molar percentage increased. This was because of an increasing chemical interaction between the polar groups of the blend components, particularly at the interface between the elastomeric and thermoplastic phases. The ultimate tensile strength of the TPVs with ENR‐20 was high because of strain‐induced crystallization. ENRs with epoxide levels >30 mol % exhibited an increase of tensile strength because of increasing levels of chemical interaction between the molecules and the different phases. The hardness of the TPVs also increased with increased epoxide levels but decreased with increased contents of ENRs. Two morphology phases with small domains of vulcanized ENR particles dispersed in the PMMA matrix were observed from scanning electron microscopy micrographs. The TPVs based on ENR‐20 and ENR‐50 showed smaller dispersed rubber domains than those of the other types of ENRs. Furthermore, the size of the vulcanized rubber domain decreased with increasing amounts of PMMA in the blends. The decomposition temperature of the TPVs also increased as both the levels of ENRs in the blends and the epoxide molar percentage increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1251–1261, 2005     

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。     

高密度聚乙烯/硅橡胶热塑性硫化胶的制备与性能

采用动态硫化法制备了高密度聚乙烯（HDPE）/硅橡胶（MVQ）热塑性硫化胶（TPV）,考察了HDPE与MVQ的质量比及压片工艺对TPV的硫化特性、力学性能及表面亲疏水性能的影响。结果表明,随着MVQ用量的增加,TPV的动态硫化程度逐渐升高。随着压片时间的延长,TPV的拉伸强度、撕裂强度和扯断伸长率均大幅提高。随着MVQ用量的增加,TPV与水的接触角逐渐增加,相应的表面张力逐渐减小。     

Effect of ATH content on electrical and aging properties of EVA and silicone rubber blends for high voltage insulator compound

The effect of trihydrated alumina (Al₂O₃, 3H₂O) (ATH) filler in ethylene‐vinyl acetate copolymer (EVA) and silicone rubber blends was investigated by performing a series of laboratory experiments to simulate different natural aging conditions. Samples with varying ATH content in a 50‐50 blend of EVA and polydimethylsiloxane (PDMS) (silicone rubber, MQ) were tested to investigate the tracking resistance, resistance to UV radiation, corona, heat, and water immersion. Changes in surface resistivity, volume resistivity, and hydrophobic characteristics were evaluated for different compounds having ATH content. These exercises were mainly carried out to optimize the filler level. In immersed condition the water absorption increases with ATH content. The recovery of hydrophobicity, after aging by heat, is appreciable at higher ATH levels, than at lower ATH levels. The tracking and erosion resistance decrease as ATH content increases. When compounds containing different ATH content were subjected to corona treatment, the samples with higher ATH levels exhibited better results. All samples changed their color to a darker shade and there was an increase in the hydrophobicity, when subjected to UV radiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3505–3516, 2007