Physico-Mechanical,Aging Properties,and Permeability of Ketones Through Vulcanizates Prepared by Different Mixing Schemes

This article reports on the physico-mechanical properties, chemical resistance, aging properties, sorption, diffusion, and permeability of ketones (cyclohexanone and acetone) through vulcanizates from blends of natural rubber (NR) and epoxidized low molecular weight natural rubber (ELMWNR) compounded by three different mixing schemes. The compounding ingredients were mixed with the two mentioned rubbers using three different mixing schemes by adopting a semi-efficient sulphur vulcanization compounding formulation. In Scheme 1, the natural rubber and ELMWNR were first mixed before adding the compounding ingredients. In Scheme 2, the compounding ingredients were first mixed with the NR before adding the ELWMNR and in Scheme 3, the compounding ingredients were first mixed with the ELMWNR before adding the NR. The physico-mechanical results of the vulcanizates showed that changes in the mixing schemes significantly influence the tensile properties of the vulcanizates. The tensile strength of the vulcanizates prepared with mixing Scheme 2 were 4.3 MPa lower than vulcanizates from Scheme 1, whereas Scheme 3 was lower than Scheme 1 with 8.5 MPa. The aging results of the vulcanizates from all the mixing schemes were found impressing. The activation energy and free energy change were highest for Scheme 1 whereas the extent of cyclohexanone and acetone penetrations were the lowest with Scheme 1, signifying well crosslinked and ketone resistant vulcanizates.     

Investigation of the degradation properties of low molecular weight natural rubber blends in oven,oxygen, ozone,water, and some organic solvents

Studies into how heat, oxygen, ozone, water, and some organic solvents affect the physico‐mechanical properties of vulcanizates prepared from blends of natural rubber (NR) and low molecular weight natural rubber (LMWNR) were investigated. Various ratios of NR and LMWNR (100:0, 95:5, 90:10, 80:20, 50:50, 25:75 10:90, 5:95, and 0:100 w/w) were mixed and labeled as mixes A to I. The physico‐mechanical properties of all the vulcanizates before and after ageing in oven, oxygen, ozone, and water were measured and compared while the resistance of the vulcanizate in toluene, carbon tetrachloride, acetone, ethanol, cyclohexane, mineral oil, and brake fluid were determined in terms of swelling and solubility measurements. From the unaged results, mix A with 100% NR has the best physico‐mechanical properties. After degradation, mix C with 10% LMWNR showed the best ageing resistant. Similarly, mix D with 20% LMWNR showed more resistance in most of the solvents used, and this was closely followed by mix C. The results generally have proven that LMWNR is capable of improving the ageing properties and solvent resistance of NR. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Interfacial Interactions of Silica and Natural Rubber Enhanced by Hydroxyl Telechelic Natural Rubber as Interfacial Modifier

The incompatibility between hydrophilic silica and hydrophobic rubber is an important problem on using silica in nonpolar rubber. In this study, hydroxyl telechelic natural rubber (HTNR) that contains hydroxyl‐terminated groups was introduced into silica‐reinforced natural rubber (NR) in order to improve the bonding strength between rubber and silica. The properties of silica‐reinforced NR compounds and vulcanizates as a function of varying silica contents were evaluated at a fixed HTNR concentration at 8% wt/wt of silica content. The results show that the improvement of silica dispersion and decreasing of filler–filler interactions (Payne effect) were obtained in the NR compounds and vulcanizates with HTNR addition. The enhancements in tensile properties, crosslink density, abrasion resistance, heat build‐up, and thermal properties of the silica‐reinforced NR vulcanizates with added HTNR confirmed that HTNR performed good as interfacial modifier of silica. In the study, the optimum properties of silica‐reinforced NR vulcanizate were achieved at 30 phr silica with 2.4 phr HTNR. However, HTNR still showed poorer efficiency than the synergy between commercial silane coupling agent, bis [3‐(triethoxysilyl) propyl] tetrasulphide (TESPT) and diphenylguanidine (DPG) when used in silica‐reinforced NR vulcanizate. J. VINYL ADDIT. TECHNOL., 26:291–303, 2020. © 2019 Society of Plastics Engineers     

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.     

Evaluation of Some Diphenylamine Derivatives as Thermal Stabilizers and Antifatigue Agents in Natural Rubber Vulcanizates

ABSTRACT

Four compounds of diphenylamine derivatives were prepared and evaluated as thermal stabilizers and antifatigue agents in natural rubber (NR) mixes. The efficiencies of these compounds were compared with phenyl-B-naphthylamine, which is widely used in rubber industry. The rheological characteristics were determined using an oscillating disc rheometer. The physico-mechanical properties of the rubber vulcanizates were measured before and after exposure to accelerated thermooxidative ageing. The results revealed that the prepared compounds were good antioxidants and antifatigue agents for rubber vulcanizates. In addition, it was found that the chemical structure of the compounds has a great effect on their efficiency as stabilizers, that is, the presence of electron donating group increases their efficiency, whereas the presence of electron withdrawing group decreases it.     

甲基丙烯酸固态原位接枝改性炭黑对天然橡胶和顺丁橡胶性能的影响

考察了固态原位接枝改性制备的甲基丙烯酸接枝改性炭黑对天然橡胶(NR)和顺丁橡胶。(BR)静态力学性能、动态力学性能的影响。结果表明。甲基丙烯酸改性炭黑比普通商品炭黑填充的NR硫化胶具有更好的静态力学性能;甲基丙烯酸改性炭黑曼有利于降低NR和BR硫化胶的滚动阻力。同时,有利于提高NR硫化胶的抗湿滑性。     

Interaction Between Fumed-Silica and Epoxidized Natural Rubber

Epoxidized natural rubber (ENR)/fumed silica vulcanizates were prepared by mechanical mixing method. Fumed silica content can affect mechanical properties of the composites, and ten parts per hundreds of rubber (phr) fumed silica lead to the best tensile strength. The interaction between ENR and fumed silica was characterized by Kraus equation, crosslink density (tested by NMR), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and scanning electron microscope (SEM). The results showed that the dispersion of silica in ENR was better than in natural rubber (NR), hydrogen bond was produced between ENR and fumed-silica in ENR/silica blends, and glass transition temperature of ENR/silica vulcanizate was higher than pure ENR vulcanizate. TGA and DMA confirmed that there was intense interaction between ENR and silica.     

Bis(trifluoromethylsulfonyl)imide Ionic Liquids Applied for Fine-Tuning the Cure Characteristics and Performance of Natural Rubber Composites

The goal of this work was to apply ionic liquids (ILs) with bis(trifluoromethylsulfonyl)imide anion (TFSI) for fine-tuning the cure characteristics and physico-chemical properties of elastomer composites based on a biodegradable natural rubber (NR) matrix. ILs with TFSI anion and different cations, such as alkylpyrrolidinium, alkylammonium, and alkylsulfonium cations, were applied to increase the efficiency of sulfur vulcanization and to improve the performance of NR composites. Thus, the influence of ILs on the vulcanization of NR compounds, as well as crosslink density and physical properties of NR vulcanizates, including tensile properties, thermal stability, and resistance to thermo-oxidative aging was explored. The activity of ILs seems to be strongly dependent on their cation. Pyrrolidinium and ammonium ILs effectively supported the vulcanization, reducing the optimal vulcanization time and temperature of NR compounds and increasing the crosslink density of the vulcanizates. Consequently, vulcanizates with these ILs exhibited higher tensile strength than the benchmark without IL. On the other hand, sulfonium ILs reduced the torque increment owing to the lower crosslinking degree of elastomer but significantly improved the resistance of NR composites to thermo-oxidation. Thus, TFSI ILs can be used to align the curing behavior and performance of NR composites for particular applications.     

表面改性碳纳米管/天然橡胶复合材料的制备及性能研究

采用多巴胺对多壁碳纳米管(MWCNTs)进行非共价改性,得到多巴胺改性MWCNTs(简称PCNT)。将PCNT作为填料加入天然胶乳中制备PCNT/天然橡胶(NR)复合材料,并研究其性能。透射电子显微镜(TEM)分析结果表明MWCNTs经过多巴胺改性后在水中的分散效果明显改善。PCNT/NR复合材料的拉伸强度和撕裂强度明显提高,拉伸强度由22.7 MPa升至28.4 MPa,撕裂强度由26 kN·m^-1升至40 kN·m^-1。多巴胺用量适当的PCNT在NR基体中分散更均匀,填料与橡胶的相互作用较强,能够形成较好的填料网络结构,PCNT/NR复合材料的表面电阻显著降低。     

A comparative study of aging characteristics and thermal stability of oil palm ash,silica, and carbon black filled natural rubber vulcanizates

Filler‐filled natural rubber (NR) vulcanizates were prepared by conventional laboratory‐sized two roll mills and cured using sulfuric system. The effect of thermal aging on physical properties and thermogravimetric analysis (TGA) of oil palm ash (OPA) and commercial fillers (i.e., silica vulkasil C and carbon black N330)‐filled NR vulcanizates at respective optimum loading and equal loading were studied. Before aging, the OPA‐filled vulcanizates showed comparable optimum strength as carbon black‐filled vulcanizates. The hardening of aged filler‐filled NR vulcanizates happened after aging, thereby tensile strength and elongation at break reduced while the modulus increased. Fifty phr carbon black‐filled vulcanizates showed better retention in tensile properties as compared to silica (10 phr) and OPA (1 phr). This was attributed to the addition of different filler loading and this finding was further explained when equal loading of filler‐filled vulcanizates was studied. Fourier transform infra‐red analysis showed chemical structure had changed and tensile fractured surface exhibited smooth appearance due to the deterioration in tensile properties after aging. TGA also denoted the thermal stability was depending on the amount of filler loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4474–4481, 2013     

Effects of antimicrobial agents on the processing and performance properties of rubber material formulations with no cytotoxicity

The present work aims to develop antimicrobial rubber for safe industrial toys. For this purpose, natural rubber (NR) and synthetic rubber as styrene butadiene rubber (SBR) and ethylene propylene diene monomer (EPDM) were examined. Rubber and their ingredients as well as antimicrobial agents (doxycycline and cephalexin) were mixed in a rubber mixer. The rheological properties of compounded rubber were studied, and the curing time was determined. Mechanical properties and cytotoxicity were evaluated at optimally cured rubber compounds. Scanning electron micrographs of vulcanizates showed good dispersion of ingredients throughout the investigated matrices. Rheology study for the investigated vulcanizates in presence of tested antimicrobial species exhibited no significant change in their flow behaviors. It is significant to remember that the desired physical characteristics of rubber products, including their chemical and mechanical characteristics (elongation at break and tensile strength) enhanced when doxycycline and cephalexin are present, depending on their nature and concentration. Similar results were obtained for both the SBR and EPDM rubber vulcanizates. The cytotoxicity of the prepared vulcanizates towards human normal retina cell line (RPI-1) indicated good safety of these rubber products. Furthermore, developed rubber vulcanizates showed good antimicrobial efficacy towards the test bacteria and fungi strains.”     

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 (NR) and thioglycollic acid modified epoxidized low molecular weight natural rubber (TGA-ELMWNR) filled with admixtures of carbon black (CB) 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 compositions. The physico-mechanical properties were found decreasing 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 aldehydes. The sorption, diffusion, and permeability of the blends as determined from 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.     

铁系乙烯基丁二烯橡胶/天然橡胶共混物的性能

研究了铁系乙烯基丁二烯橡胶(FVBR)与天然橡胶(NR)以50/50(质量比)共混硫化胶的物理机械性能和黏弹特性,并与溶聚丁苯橡胶(SSBR)与NR共混胶进行了对比。结果表明,FVBR与NR有良好的相容性,共混胶只存在1个玻璃化转变温度。FVBR/NR的混炼行为良好,但必需添加操作油,否则难以获得理想的硫化胶性能。FVBR/NR与SSBR/NR相似,不仅具有良好的拉伸和撕裂性能,而且具有高抗湿滑性;其生热和滚动阻力以及热老化性能优于后者,但耐磨性略逊于SSBR/NR。     

Blends of Natural Rubber with Unsaturated Polyester Resin

The effect of modifying natural rubber (NR) using unsaturated polyester resin (UPR), by compounding on a two-roll mill, is investigated in this study. Both commercial resin and resins prepared in the laboratory under controlled conditions have been employed. After testing several possible catalyst systems, the benzoyl peroxide/dimethyl aniline (BPO/DMA) system was identified as a suitable catalyst system for UPR for blending with NR. The extent of unsaturation in the UPR influences the physical properties of the blend negatively. The UPR is found to have a positive effect on the aging properties of natural rubber.     

硅藻土/天然橡胶复合材料的性能研究

利用环氧化天然胶乳作为硅藻土的界面改性剂,制备了硅藻土/天然橡胶复合材料,通过无转子流变仪、电子万能材料试验机和橡胶动态压缩生热仪,研究了复合材料的硫化特性,物理机械性能和温升特性。结果表明,硅藻土/天然橡胶复合材料的焦烧与正硫化时间随着硅藻土含量的增加,先增后减;最大与最小扭矩随硅藻土含量的增加而增加;硅藻土/天然橡胶复合材料的拉伸与撕裂强度均有提高,当硅藻土含量为4phr时,拉伸强度最高,为28.5MPa;当硅藻土的含量为2phr时,撕裂强度最高,为37.9N/mm;由于硅藻土的加入,材料的内生热显著降低。     

Effect of triblock copolymers on homogeneity,mechanical properties and swelling behavior of IIR/SBR rubber blends

The present research concerns with the preparation and characterization of isobutylene isoprene/butadiene–styrene rubber (IIR/SBR) blends with different blend ratios, in the presence and absence of styrene–isoprene–styrene (SIS) and styrene–isobutylene–styrene (SiBS) triblock copolymers to be tested as compatibilizers. Effect of the triblock copolymers on the blend homogeneity was investigated with the aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. Characterization of the rubber blends was conducted by measuring the physico-mechanical properties after and before thermal aging, in presence and absence of the triblock copolymers. In addition, weight swell % in toluene, motor oil and brake fluid of the rubber blend vulcanizates was assessed. The incorporation of SIS and SiBS triblock copolymers improved the homogeneity of IIR/SBR blends as well as increased both tensile strength and elongation at break of the rubber blend vulcanizates. Of the entire blend ratios examined, IIR/SBR (25/75) blend containing SIS compatibilizer possessed the best physico-mechanical properties (12.6 MPa tensile strength and 425 % elongation at break) and (14 MPa tensile strength and 555 % elongation at break) after and before thermal aging, respectively. Utilization of SIS and SiBS triblock copolymers enhanced the thermal stability of IIR/SBR blend vulcanizates. Moreover, IIR/SBR blends of different blend ratios showed superior swelling resistance in the brake fluid. IIR/SBR (25/75) blend containing SIS compatibilizer and cured with CBS/ZDEC/S vulcanizing system possessed the best physico-mechanical properties (14.4 MPa tensile strength and 440 % elongation at break) and (16.5 MPa tensile strength and 610 % elongation at break) after and before thermal aging, respectively.     

加料顺序对炭黑/NR相互作用及性能的影响

研究了加料顺序对炭黑/NR间相互作用及胶料性能的影响。结果表明,配方相同时,采用先加小料后加炭黑的加料顺序可使混炼过程能耗最低,混炼胶加工性能较好,综合物理机械性能较好;加料顺序对交联密度基本没有影响;在混炼过程中,加入小料会迅速降低胶料扭矩值,起到增塑作用,有利于分散;提前加入炭黑会增强炭黑/NR间相互作用,生成较多结合橡胶。     

White Rice Husk Ash-Filled Natural Rubber Compounds: The Effect of Bonding Agents

White rice husk ash (WRHA)-filled natural rubber compounds were prepared by using a laboratory-size two-roll mixing mill. Curing using a conventional vulcanization system was used and cure studies were carried out on a Monsanto rheometer. The mechanical testing of the vul-canizates involves the determination of tensile properties, tear strength, hardness, and resilience. Scanning electron microscopy (SEM) and swelling measurement were also done. The effects of bonding agents on the curing and mechanical properties have been investigated using re-sorsinol formaldehyde and hexamethylene tetramine as the bonding agents. Results show that the bonding agents prolonged the cure time t ₉₀ and scorch time t ₂ and, at the same time, improved the mechanical properties of the natural rubber vulcanizates. SEM and swelling studies indicate that the rubber-filler interaction is improved with the addition of bonding agents.     

Blending of NR/BR/EPDM by reactive processing for tire sidewall applications. I. Preparation,cure characteristics and mechanical properties

EPDM incorporated into blends of natural rubber/butadiene rubber (NR/BR) improves ozone resistance. In this work, the inferior mechanical properties of NR/BR/EPDM blends generally obtained by conventional straight mixing are overcome by utilizing a reactive processing technique. The entire amount of curatives, based on a commonly employed accelerator N‐cyclohexyl‐2‐benzothiazole sulfenamide (CBS) and sulfur, is first added into the EPDM phase. After a thermal pretreatment step tuned to the scorch time of the EPDM phase, the modified EPDM is mixed with premasticated NR/BR. The reactive blend vulcanizates show a significant improvement in tensile properties: tensile strength and elongation at break, as compared to those prepared by straight mixing, in both gum and carbon black‐filled blends. The increase of tensile properties in gum and filled reactive blend vulcanizates does suggest that the reactive processing technique leads to more homogeneous blends due to, either a better crosslink distribution, or more homogeneous filler distribution, or both. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:2538–2546, 2007     

国产脱蛋白天然橡胶的性能及应用

研究国产脱蛋白天然橡胶（DPNR）的性能及其在减震橡胶制品中的应用。结果表明：与普通天然橡胶（NR）相比,DPNR的氮含量较小,压缩生热较低,压缩永久变形较小,弹性和电绝缘性能较好,拉伸强度和拉断伸长率略低,耐老化性能稍差;用国产DPNR为主体材料试制的机车弹性旁承的强化疲劳性能、尺寸稳定性和弹性好,压缩永久变形小。