天然橡胶/三元乙丙橡胶并用胶共混改性研究进展

系统总结了天然橡胶和三元乙丙橡胶相容性和共硫化性差的原因,从调节生胶共混比、增加增容剂用量、优选交联剂、改进共混工艺、对生胶进行化学改性和辐射硫化改性等角度较为全面地介绍了近年来在天然橡胶/三元乙丙橡胶并用胶共混改性方面的技术进展,并对天然橡胶和三元乙丙橡胶共混改性领域内未来的发展趋势进行了展望。     

天然橡胶/三元乙丙橡胶合金弹性体的共硫化及耐热氧老化性能

通过将天然橡胶(NR)的低硫高促延迟硫化体系（硫黄/促进剂CZ/促进剂TRA/促进剂MBT/促进剂ZBPD）与三元乙丙橡胶(EPDM)的快速硫化体系（硫黄/促进剂CZ/促进剂TRA/促进剂TDEC/促进剂TMTD）相配合,基于先各自制备母炼胶再合炼的混炼工艺,成功实现了NR/EPDM（质量比60/40）合金弹性体的同步共硫化,有效提升了合金弹性体的力学性能和相容性。当NR母炼胶和EPDM母炼胶的正硫化时间分别为3.43 min和4.11 min时,二者共硫化后所得硫化胶的拉伸强度达到15.8 MPa,在100 ℃经72 h热氧老化后的扯断伸长率保持率从使用半有效硫化体系的44%提高到71%。使用高含量喹啉聚合体的防老剂STMQ可以有效提升NR/EPDM合金弹性体的耐热氧老化性能,在100 ℃经72 h热氧老化后,NR/EPDM合金弹性体的拉伸强度保持率从57%增加至72%。     

天然橡胶／三元乙丙橡胶并用胶料的共硫化

发现由MBTS(二硫化硫醇基苯并噻唑)和DPG(二苯胍)催化之硫黄与过氧化物硫化剂构成的新型硫化体系能改善天然橡胶(NR)与三元乙丙橡胶(EPDM)并用胶料的共硫化性。与传统的硫黄硫化体系相比,这一硫化体系能将NR/EPDM硫化胶的拉伸强度提高一倍、即便在不添加防老剂的条件下也具有优异的防热老化性和优良的静态防臭氧老化性当配入的过氧化物及其它硫化组分之用量和品种合宜时,硫化体系中所含的过氧化物不会对热空气硫化罐中硫化的NR/EPDM硫化胶产生任何有害的影响。     

氟橡胶/三元乙丙橡胶并用胶的性能

研究了不同并用比(质量比)时氟橡胶(FKM)/三元乙丙橡胶(EPDM)并用胶动态硫化和静态硫化后的低温性能、物理机械性能、耐老化性能和热稳定性,并用扫描电子显微镜表征了并用胶.结果表明,当并用比为30/70时,并用胶有较好的相容性;EPDM可以改善FKM的低温性能;随着EPDM用量的增加,并用胶的拉伸强度及邵尔A硬度降低;动态硫化FKM/EPDM并用胶比静态硫化FKM/EPDM并用胶具有更好的耐老化性能,但老化前前者的拉伸强度稍低于后者;FKM/EPDM并用胶的热稳定性优于纯EPDM;静态硫化FKM/EPDM并用胶中片层现象严重,动态硫化FKM/EPDM并用胶的EPDM包覆在FKM中,但相畴偏大.     

用于变压器的丁腈橡胶/三元乙丙橡胶并用胶

为了实现丁腈橡胶(NBR)与三元乙丙橡胶(EPDM)并用作为变压器密封材料,研究了并用比、增容剂及硫化体系种类对NBR/EPDM并用胶的影响。结果表明,NBR/EPDM(质量比)为70/30时并用胶具有良好的耐臭氧性能与最佳的综合物理机械性能;在并用胶中加入增容剂乙华平8784可以改善其物理机械性能;使用过氧化物硫化体系硫化并用胶的物理机械性能比使用硫黄/促进剂硫化体系者更好。     

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。     

Development of hydroxyapatite nanoparticles reinforced chlorinated acrylonitrile butadiene rubber/chlorinated ethylene propylene diene monomer rubber blends

Hydroxyapatite nanoparticles (HA) reinforced polymer blend based on chlorinated nitrile rubber (Cl-NBR) and chlorinated ethylene propylene diene monomer rubber (Cl-EPDM) were prepared. Resulting blend composites were analyzed with regard to their rheometric processing, crystallinity, glass transition temperature (T_g), mechanical properties, oil resistance, AC conductivity, and transport behavior. The decrease in optimum cure time with the addition of HA is more advantageous for the development of products from these blend nanocomposites. The XRD, FTIR, and SEM confirmed the attachment and uniform dispersion of HA nanoparticles in the Cl-NBR/Cl-EPDM blend. The good compatibility between polymer blend and nanoparticles was also deduced by the formation of spherically shaped HA particles in the blend matrix determined by TEM analysis. DSC analysis showed an increase in T_g of the blend with the filler loading. The addition of HA particles to the blend produced a remarkable increase in tensile and tear strength, hardness, AC conductivity, abrasion, and oil resistance. The diffusion of blend composites was decreased with an increase in penetrant size. The diffusion mechanism was found to follow an anomalous trend. Among the blend composites, the sample with 7 phr of HA not only showed good oil and solvent resistance but also a remarkable increase in AC conductivity and mechanical properties.     

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     

Naturally occurring halloysite nanotubes for enhanced durability of natural rubber/ethylene propylene diene monomer rubber vulcanizate

A facile approach of using halloysite nanotubes (HNTs) was proposed to address the durability performance demands of natural rubber (NR)/ethylene propylene diene monomer rubber (EPDM) blends and to protect them from the deleterious effects of the service environment including ozone, chemicals, abrasion, and cyclic loading. The introduction of HNTs substantially improved the stability of NR/EPDM when exposed to ozone (over fourfold enhancement with the addition of 5 phr HNTs). Moreover, the HNT-filled NR/EPDM vulcanizates offered approximately 66% reduction in the solvent-mediated swelling in comparison to the unfilled sample. Fatigue life studies showed that the HNT-reinforced NR/EPDM composite could withstand 30% more cycles to failure than the un-reinforced NR/EPDM blend. The effect of various HNT loading on the morphological, mechanical, physical, and rheological properties of nanocomposite vulcanizates based on NR/EPDM was also investigated. The morphological investigations revealed that the introduction of HNT into the NR/EPDM rubber matrix caused a rough morphology in fracture surface and a well-dispersed structure was obtained with the addition of up to 5 phr of HNTs. These findings were further supported by rheological, mechanical, and thermodynamical results.     

超细全硫化粉末丁苯橡胶/三元乙丙橡胶共混物的结构与性能

制备了超细全硫化粉末丁苯橡胶(UFPSBR)/三元乙丙橡胶(EPDM)共混物,研究了其硫化特性、相态结构、动态力学性能及物理机械性能。透射电镜观察表明,无论UFPSBR与EPDM共混比如何,UFPSBR粒子始终保持为分散相。当UFPSBR用量为10份(质量)时,它在EPDM中的分散相尺寸为200 nm左右;用量较高时其分散相尺寸较大,存在大量的聚集体。动态力学分析结果显示共混物存在2个玻璃化转变温度,说明共混物存在两相结构。加工性能分析结果表明,UFPSBR粒子在EPDM基质中形成了网络结构,对EPDM基质起到了较好的增强作用,当UFPSBR与EPDM的质量共混比为50/50时,共混物的拉伸强度可达13.4 MPa。UFPSBR对EPDM的硫化特性有明显影响。     

A modus operandi toward interfacial enhancement of ethylene propylene diene monomer rubber/ polybenzoxazine blends using EPDM-grafted-vinyltrimethoxysilane copolymer

Compatibilization of polymer blends is performed to obtain synergistic effects in physical and mechanical properties. The present work demonstrates the ability of vinyltrimethoxysilane-grafted-ethylene propylene diene monomer rubber (VTMS-g-EPDM) to improve the compatibility between EPDM and polybenzoxazine (PB). EPDM reacted with 5 phr of VTMS showed the highest grafting efficiency as well as a relatively low gel content, and was added to EPDM/PB blends. The addition of 8 phr of compatibilizer to 70/30 (w/w) EPDM/PB reduced the dispersed PB droplet size from 3.1 μm to 800 nm. Effects of various blend compositions at constant dosage of compatibilizer (8 phr) on the swelling behavior and tensile properties of the samples were also studied. The tensile strength increased from 12 to 14.5 MPa upon adding the compatibilizer at 50/50 blend ratio of EPDM/PB; however, the increase in the PB content had no significant impact on the tensile strength in both compatibilized and non-compatibilized samples.     

Effects of peroxide and gamma radiation on properties of devulcanized rubber/polypropylene/ethylene propylene diene monomer formulation

Mechanical and thermal properties of devulcanized rubber (DR)/polypropylene (PP)/ethylene propylene diene monomer blends (EPDM) were studied at various concentrations of dicumyl peroxide (DCP) and gamma radiation doses. The blends showed improved mechanical properties for vulcanized sample. The coupling of DR/PP/EPDM with different proportions of DCP was investigated by X‐ray diffraction and scanning electron microscopy techniques. Evaluation of the developed blends, unirradiated and gamma irradiated, was carried out using elastic modulus, tensile strength, elongation at break, thermogravimetric analysis, kinetic analysis, and DSC measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40611.     

Thermomechanical devulcanization of ethylene propylene diene monomer rubber and its application in blends with high-density polyethylene

The recycling of ethylene propylene diene monomer (EPDM) rubber remains a challenge, as its cross-linked structure cannot be broken down reversibly. Devulcanization may offer a breakthrough; however, a 100% decrease in cross-link density (CLD) with no chain degradation has never been reported. In this research, sulfur- and peroxide-cured EPDM rubbers of known compositions were devulcanized on a two-roll mill and in an internal mixer. The CLD of both rubber samples decreased by around 85%, while the sol content of the peroxidic devulcanizate was considerably higher than that of the sulfuric devulcanizate (23% vs. 3%). Horikx's theory revealed that sulfur-cured samples showed excellent selectivity for cross-link scission, while peroxide-cured samples suffered degradation. Uncured, cured, and devulcanized rubber samples were mixed into high-density polyethylene at various compositions. Large EPDM rubber contents impaired the mechanical properties of the blends, indicating insufficient adhesion between the two phases. Compounds containing originally uncured rubber mixtures had the most beneficial mechanical properties.     

助交联剂对三元乙丙橡胶过氧化物硫化的影响

分别采用三烯丙基异氰脲酸酯(TAIC)、三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)以及高乙烯基聚丁二烯(HVPBd)作为过氧化物硫化三元乙丙橡胶(EPDM)的助交联剂,研究其对EPDM胶料硫化特性及硫化胶力学性能的影响。结果表明,3种助交联剂的添加能明显促进硫化程度,硫化胶的硬度和定伸应力均明显提高,添加TAIC的EPDM混炼胶硫化程度最高,但添加TMPTMA使胶料的焦烧安全性变差,而添加HVPBd的EPDM胶料降解程度最低。通过一级动力学模型及自催化反应模型研究EPDM硫化动力学行为时发现,助交联剂类型影响胶料的硫化反应速率,其中TMPTMA能明显促进硫化反应速率,TAIC次之,而HVPBd几乎没有影响,但硫化反应表观活化能由于助交联剂的添加均出现降低,其中添加TAIC胶料的表观活化能最低。