Study on characterization and properties of nanosilica‐filled thermoplastic vulcanizates

Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomer, produced by simultaneously mixing and cross‐linking a rubber with a thermoplastic at elevated temperature. Dicumyl peroxide‐cured TPVs based on blends of maleated ethylene propylene rubber (m‐EPM) and polypropylene (PP) thermoplastic using maleated‐PP as a compatibilizer have been developed. To reinforce the properties of these TPVs, nanosilica was added at different levels. With the increase of nanosilica concentrations, significant improvement in tensile strength, modulus, and impact strength of TPVs have been achieved. Morphology study shows that nanosilica is uniformly dispersed in the polymer matrices. Dynamic mechanical analysis shows that tan δ value at low temperature decreases with increasing nanosilica concentration indicating less damping characteristics. Thermogravimetric study revealed that thermal stability of TPVs is improved in presence of nanosilica. Equilibrium swelling study confirms that solvent resistance of TPVs could be improved by nanofiller incorporation. Rubber process analyzer found a very useful tool to understand the melt rheology of nanosilica filled TPVs in terms of dynamic functions over a wide range of strain amplitude and frequency. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Preparation and properties of carbon black filled EPDM/POE thermaplastic vulcanizates

TPVs filled with different amounts (0–50 phr) of carbon black were prepared via melt mixing by dynamic vulcanization in Haake plasticorder at 150°C and 40rpm and then the properties of them were studied. Torque-time curves showed that the curing degree reached a biggest value at 10 phr and then decreased with the increase of filling content while the curing rate was always rising. Mechanical properties such as tensile strength, tear strength, modulus as well as hardness increased with the increment of carbon black content while the tension set at break was reduced dramatically. Two phase morphology was observed by SEM photographs and the effect of carbon black on curing extent was testified. To illuminate the effect of carbon black, curometer curves and carbon black dispersion pictures were also analyzed. Rubber processing analyzer (RPA) experiments proved that there was a progressive nonlinear behavior, which was more and more clearly expressed with the increment of carbon black content and could be explained via the Payne effect. But the TPVs containing highest carbon black exhibited the fastest drop of G′ with increasing strain amplitude as obtained from the value of G₀′ − G_∞′. The order of tanδ at different carbon black content was tanδ (10 phr) < tanδ (0 phr) < tanδ (30 phr) < tanδ (50 phr) at lower strain amplitude. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

杜仲胶/聚乳酸形状记忆热塑性硫化胶的制备及性能

将生物基高分子材料杜仲胶（EUG）和聚乳酸（PLA）通过动态硫化技术制备了具有形状记忆性能的热塑性硫化胶（EUG/PLA TPV）。通过扫描电子显微镜、差示扫描量热、动态力学和力学性能测试及热机械循环分析等手段分别考察了EUG/PLA TPV的微观形貌、相容性、热性能、动态力学和力学性能及形状记忆性能。结果表明,增容剂腰果酚有效改善了EUG相与PLA相之间的相容性,从而提高了EUG/PLA TPV的力学性能。当橡塑质量比为5/5时,拉伸强度为10.5 MPa,扯断伸长率达到286%,是纯PLA的约48倍。EUG/PLA TPV具备特殊的双连续相结构,可以赋予其良好的形状记忆性能,形状固定率最高达到93%左右,形状回复率最高达到98%左右。     

偶联剂与混炼工艺对炭黑填充NBR胶料性能的影响

研究偶联剂Si69和KH-550与混炼工艺对炭黑填充NBR胶料硫化特性、表观交联密度、物理性能和动态性能的影响。结果表明,偶联剂的加入能够延长胶料的t90,经高温混炼后的NBR胶料的焦烧时间缩短,t90延长;偶联剂能够增大NBR胶料的表观交联密度和炭黑-橡胶间的相互作用,经高温混炼后作用更加明显,硫化胶的物理性能提高;加入偶联剂KH-550并经高温辊改性后的NBR硫化胶具有更好的耐热老化性能。偶联剂Si69或KH-550能够改善NBR硫化胶的动态性能,加入偶联剂KH-550并经高温改性后性能较佳。     

硫化硅橡胶交联结构与物理性能关系研究

研究硫化体系、硫化剂用量、基体硅橡胶相对分子质量和交联密度对硫化硅橡胶硬度、压缩应力和柔顺性的影响。结果表明,随着硫化剂用量的增大,硫化硅橡胶的硬度和压缩应力增大;当基体硅橡胶相同时,采用加成硫化体系制备的硫化硅橡胶柔顺性较采用过氧化物硫化体系更好;当采用加成硫化体系时,基体硅橡胶相对分子质量和硫化胶交联密度越小,硫化硅橡胶的柔顺性越好。     

Improvement of the mechanical and thermal properties of silica‐filled polychloroprene vulcanizates prepared from latex system

In this work, well‐dispersed silica suspension having excellent storage stability was prepared by using an ultrasonic probe. The obtained silica suspension and curatives were added into the polychloroprene (CR) latex for preparing silica‐filled CR latex compounds having various silica loadings. Then, the silica‐filled CR vulcanizates were prepared via a dipping process. The thermal and mechanical properties of the dipped CR vulcanizates containing silica dispersed by using an ultrasonic probe were compared with those of the dipped CR vulcanizates containing silica dispersed by using a mechanical stirrer. By using thermogravimetric analysis, it could be seen that thermal resistance of the dipped CR films having silica prepared by ultrasonic probe is greater than that prepared by using the mechanical stirrer. This result corresponds well with their tensile strength after aging in the hot‐air oven. In addition, modulus, tensile strength, and tear strength of the vulcanizates prepared from CR latex compounds containing silica prepared by using the ultrasonic probe are obviously greater than those prepared by using the mechanical stirrer, especially at high silica loading. This is because the silica prepared using the ultrasonic probe is uniformly distributed and dispersed throughout the CR matrix, as can be observed in the scanning electron microscope micrographs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bis(N‐benzyl piperazino) thiuram disulfide and dibenzothiazyl disulfide as synergistic safe accelerators in the vulcanization of natural rubber

Some investigation regarding the effect of binary system of accelerators comprising one safe thiuram disulfide, namely bis(N‐benzyl piperazino) thiuram disulfide (BPTD) and dibenzothiazyl disulfide (MBTS), on the vulcanization of NR is carried out. The results are compared with those obtained with conventional tetra methyl thiuram disulfide (TMTD) presently considered as unsafe. The vulcanizates obtained from safe synergistic pair of accelerators (BPTD‐MBTS) possess comparable mechanical properties [modulus, tensile strength, and elongation at break (%)] and exhibits some improvement in heat resistant behavior when compared with those obtained with TMTD‐MBTS system. In the light of mechanical properties, safe BPTD‐MBTS system introduces the safe noncarcinogenic rubber accelerator in the vulcanization of rubber. Same type of synergistic activity may be due to comparable activation energy for both the TDs with the combination of MBTS. Although rate constant values are low for BPTD‐MBTS (6 : 3) compared to TMTD‐MBTS (6 : 3) in the high temperature vulcanization, the crosslinking efficiency of former is very large compared to later. This may be responsible for improvement in heat resistance behavior of the novel accelerator in the combination with MBTS. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

氧化亚铁硫杆菌脱硫天然橡胶粉及其填充胶的性能

从铁矿土壤中分离出1株氧化亚铁硫杆菌,比较了其在不同Fe2+质量浓度的改进9 K培养基中的生长情况,确定最佳的天然橡胶胶粉加入时间为培养开始后的第30 h。利用氧化亚铁硫杆菌在较低Fe2+质量浓度的改进9 K培养基中进行脱硫实验,脱硫橡胶表面的傅里叶变换红外光谱、X射线光电子能谱分析和培养液中SO42-的浓度变化都表明氧化亚铁硫杆菌是通过氧化硫黄的代谢途径来断裂橡胶中的硫黄交联键。用该脱硫胶粉填充天然橡胶硫化胶的力学性能有一定程度的提高;通过扫描电子显微镜可以看出脱硫胶粉与天然橡胶基质的界面结合较好,应力集中点较少,脆断面的断裂线均匀。     

Cure characteristics and physical properties of ground‐rubber‐filled natural rubber vulcanizates: Effects of the curing systems of the ground rubber and rubber matrix

Recycling discarded rubber is important for both environmental and economic reasons. One of the most attractive methods of recycling rubber waste is to use ground rubber (GR) as a compounding ingredient or as a replacement for raw polymers. In this study, ground natural rubber was prepared with different curing systems and compounded into the parent compounds. The cure behaviors and physical properties of the GR‐filled vulcanizates were investigated, and they were largely affected by the curing systems of the rubber matrix and GR. GR‐filled vulcanizates with GR and the rubber matrix, having a conventional curing system, showed the largest changes in the cure characteristics. The greatest decrease in the physical properties was observed for peroxide‐cured‐GR‐filled vulcanizates. The addition of GR decreased the crosslink density of the GR‐filled vulcanizates. This was thought to be the main reason for the reduction of the mechanical properties of the GR‐filled vulcanizates. However, the adhesion between the GR and rubber matrix may also have caused the differences in the physical properties of the GR‐filled vulcanizates with respect to the curing systems of the rubber matrix and GR. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Conducting carbon black filled NR/ IIR blend vulcanizates: Assessment of the dependence of physical and mechanical properties and electromagnetic interference shielding on variation of filler loading

A series of natural rubber/ butyle rubber NR/ IIR (70/30) loaded with general purpose furnace (GPF) carbon black have been produced on a laboratory scale, and their electrical and mechanical properties were investigated. The percolation threshold concentration has been described using Kirkpatrick and Zallen model. The percolation model gives a suitable explanation, within the experimental data of the studied samples. The thermal stability of composites was also investigated. It was found that the stability of high filler content blend was better than that of low filler content, due to strong polymer-filler interaction at high filler concentrations. Variation of mechanical properties of carbon black-filled compounds with the filler content was also investigated. Electromagnetic interference (EMI) shielding characteristics of these composites were studied. The measurements of shielding effectiveness (SE) were carried out in different frequency ranges from 0.5–5 GHz and it increases with the increase in filler loading. SE values were in the range of 7–30 dB.     

Mechanical properties of deproteinized natural rubber in comparison with synthetic cis‐1, 4 polyisoprene vulcanizates: Gum and black‐filled vulcanizates

Gum and black‐filled vulcanizates having various crosslink densities were prepared from 2 types of rubber, namely, deproteinized natural rubber (DPNR) and synthetic cis‐1, 4 polyisoprene vulcanizates (IR). Their mechanical properties, such as tensile strength, tear strength, abrasion loss, and heat buildup resistance, at various crosslink densities as well as at similar optimum crosslink density were compared. For both gum and black‐filled systems, IR possessed a higher crosslink density than that of DPNR at a fixed curative content. Tensile and tear strength of all vulcanizates passed through a maximum with increasing crosslink density. For gum vulcanizates, tensile and tear strengths of DPNR and IR below the maximum were not much different. However, IR had a narrower tear strength peak relative to DPNR. At a comparable optimum crosslink density, DPNR exhibited higher tensile strength and crack growth resistance than IR. For black‐filled vulcanizates, tensile and tear strengths, and heat buildup resistance of DPNR and IR at a given crosslink density were similar. The results revealed that the properties of gum samples were more dependent upon crosslink density than the black‐filled ones because the reinforcement by carbon black overshadowed the intrinsic properties of the rubbers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1139–1144, 2005     

Physico‐mechanical,dynamic mechanical,and swelling properties of sodium chloride filled chlorobutyl vulcanizates

The effect of addition of rigid, nonreinforcing, and noninteracting filler viz. finely ground NaCl in chlorobutyl vulcanizates on properties such as physicomechanical, dynamic mechanical, and swelling has been studied. The nonreinforcing effect of NaCl in the system was studied by Russel and Cunnenn analysis and Kraus plots. Mechanical measurements of stress and strain at the break of filled and unfilled samples showed no appreciable change in the mechanical behavior of the system. The dynamic mechanical analysis showed that there is no change at all in the glass transition temperature with addition of NaCl filler. The damping properties showed an increase with increase in filler loading because of the filler–filler friction. The swelling behavior of NaCl‐filled CIIR was studied for a period of 60 days in four different solvents of varying chemical energy potential viz. water, chloroform, acetone, and tetrahydrofuran (THF). The degree of swelling was found to increase continuously with time in water, which is a good solvent for the filler, and in THF, which is a good solvent for the polymer matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 707–714, 2006     

Effect of tackifiers on mechanical and dynamic properties of carbon‐black‐filled NR vulcanizates

This work focuses on the effect of tackifiers on mechanical and dynamic properties of carbon‐black‐filled vulcanizates. Three types of tackifiers with difference in softening points are selected for study including petroleum resin, phenolic resin, and gum rosin. The effect of tackifiers on the retardation of vulcanization is observed and the changes in mechanical properties due to the reduction in crosslink density are correlated. Good compatibility between natural rubber and all three tackifiers is verified by a single tan‐delta peak detected for each vulcanizate in temperature ramp test. A similar behavior to the Payne effect which usually found in the case of particulate‐filled rubbers is observed for the tackifier‐filled counterparts. The variation of temperature plays a crucial role in the dynamic behavior of tackified vulcanizates since the state of tackifiers determines its function during dynamic straining. As temperature passed through the softening point of a particular tackifier, substantial reduction in elastic response is observed; however, its relative damping to the untackified may still be maintained. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.     

酵母菌生物脱硫胎面胶粉及其填充天然橡胶的力学性能

用酵母菌对胎面胶粉(GTR)进行了生物脱硫实验,考察了酵母菌与GTR共培养脱硫过程中酵母菌的生长情况,对比了GTR和脱硫GTR(DGTR)填充天然橡胶(NR)硫化胶的交联密度、表面元素含量和力学性能.结果表明,在共培养脱硫过程中酵母菌依然可以保持较高的生物量,脱硫6 d后可获得生物脱硫的GTR.随着胶粉用量的增加,填充NR硫化胶的交联密度和力学性能逐渐降低.相比较GTR/NR硫化胶,DGTR/NR硫化胶的表面硫元素含量和交联密度更低,力学性能明显提高.     

不同秋兰姆类促进剂TRA对NBR发泡胶硫化特性及物理机械性能的影响

本文使用密炼机,探索了不同秋兰姆类促进剂TRA对NBR发泡胶硫化特性及物理机械性能的影响,结果表明:无论秋兰姆的用量怎样变化,胶料的硫化速度始终大于胶料的发泡速度;TRA具有延迟AC发泡剂发泡的作用;随着秋兰姆类促进剂TRA用量的增大,发泡胶料的扯断强度逐渐增大,发泡胶料的断裂伸长率逐渐下降,发泡胶料的密度呈现先减少后...     

Improving oxidation stability and mechanical properties of natural rubber vulcanizates filled with calcium carbonate modified by gallic acid

A novel technique to modify the surface of calcium carbonate (CaCO₃) nanoparticles, used as an antioxidant and reinforcing filler, by gallic acid is disclosed. The new properties of the modified CaCO₃ could make it more useful and practical for the rubber industry. Thermal gravimetric (TGA), Fourier transform infrared spectroscopy, and transmission electron microscopy analyses showed that the gallic acid was bound onto the surface of CaCO₃. The gallic acid modified CaCO₃ exhibited a significant antioxidation property, as revealed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) analysis. The mechanical properties of natural rubber vulcanizates filled with the gallic acid modified CaCO₃ showed an enhanced reinforcement with increasing loading levels, and increased resistance to ozonolysis over that seen with the unmodified CaCO₃ mixed with Irganox 1010 as the commercial antioxidant.     

Effects of hygrothermally decomposed polyurethane on the curing and mechanical properties of carbon black‐filled epoxidized natural rubber vulcanizates

Hygrothermally decomposed polyurethane (HD‐PUR) was mixed up to 20 phr in epoxidized natural rubber (with 50 mol % epoxidation; ENR50) recipes, and the curing and mechanical behaviors were studied. Mechanical testing of the ENR50/HD‐PUR vulcanizates determined the tensile, tear, compression‐set, hardness, abrasion, hysteresis, and resilience properties. No significant changes were observed in the tensile properties with the incorporation of HD‐PUR. The ENR50 compounds showed an increase in compression set with increasing HD‐PUR content. Rubbers cured by a semi‐efficient vulcanization system gave the best overall performance. A further improvement in curing and mechanical properties was achieved by the carbon black grade N330 being replaced with a more active grade (N375). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2265–2276, 2002     

A study of sulfur bridges in filled natural rubber vulcanizates by pyrolysis gas chromatography with flame-photometric detection

Natural rubber vulcanizates of two formulations, with sulfur/N-cyclohexyl-2-benzothiazolesulfenamide (CBS) and tetramethylthiuram disulfide (TMTD), respectively, were analyzed by pyrolysis gas chromatography. A sulfur-selective flame-photometric detector was utilized. The main pyrolysis products were identified as CS₂ and some thiophenes. The yields of the pyrolysis products from the two types of rubber were very different. The yields also varied with the curing time of the rubbers.     

Characterization and physical properties of CoCl2 filled polyethyl‐methacrylate films

Pure polyethyl‐methacrylate (PEMA) and PEMA filled with CoCl₂ films were prepared by casting method. The structure and characterization of these film composites were investigated using Fourier transform infrared analysis (FTIR), optical spectra (UV), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and DC electrical conductivity. FTIR was used to identify the structural variations due to changing CoCl₂ concentration. The assigned conjugated double bonds suggested the presence of polarons and bipolarons in the polymeric matrix. The shift of some bands manifested the specific interaction in PEMA matrixes and the filler. XRD reveals the presence of some crystalline phase in PEMA matrixes. The degree of crystallinity increase with increasing CoCl₂ and there is no significant change on the halos center but it has become less obvious. Optical absorption measurements reveal that CoCl₂ filler influences the optical energy gap. TGA data clarified that addition of CoCl₂ to PEMA films enhances the thermal stability of PEMA. The activation energy decreases with increase in CoCl₂ content. The electrical properties were studied using DC electrical conductivity. The electrical measurements revealed a nearly monotonic behavior of electrical conductivity as CoCl₂ content increased. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Effects of types of fillers on the molecular relaxation characteristics,dynamic mechanical,and physical properties of rubber vulcanizates

The dynamic mechanical, and physical properties of bromobutyl rubber were investigated to determine the effect of particle size and of the structure of carbon black and silica. Filler loading was so adjusted that all the experimental compositions had the same hardness level. The results indicate that the type and loading of filler have no significant effect on the molecular relaxation transition. However, elastomer having a desirable storage modulus with low sensitivity to temperature change can be developed using filler with smaller particle size. Higher elongation at break, and better tensile strength, energy density at break, and fatigue life could be obtained by using finer particle or high structure black than with the low structure and higher particle size black. Finer particle size filler loaded systems exhibit pronounced strain dependence, higher thixotropic change, and delayed recovery in dynamic mechanical properties compared to that exhibited by large particle size filler.