Adhesive tack and green strength of EPDM rubber

Measurement of tack of EPDM (ethylene-propylenediene terpolymer) rubber with natural rubber (NR) of four different molecular weights, styrene-butadiene rubber (SBR), butadiene rubber (BR), bromobutyl rubber (BIIR), and polychloroprene rubber (CR) was done over a range of rates of testing, contact times, and temperatures of contact. The effect of different additives, namely carbon black, phenol-formaldehyde resin, coumarone-indene resin, and methyl methacrylate is also reported. Green strength of all the rubbers was measured. Tack strength increases with increase in contact time for all the rubbers. Adhesive tack between EPDM and low-molecular-weight NR is much higher than that between EPDM and NR of high molecular weight. Tack strength of EPDM with BIIR is the highest among the tack values obtained for synthetic rubbers. The adhesive tack between EPDM and natural/ synthetic rubber passes through a maximum when plotted against temperature of contact. It increases with testing rate. All these phenomena could be explained in terms of interdiffusion of rubber chains under different conditions and solubility parameter of two contacting rubbers. It was observed that tack strength varies with (contact time)^1/2 and (rate)^1/2 in accordance with the reptation theory. Phenol-formaldehyde resin (PF) or coumarone-indene (CI) resin in EPDM improves the tack strength quite significantly. The resin in the NR phase does not have a marked effect. The presence of carbon black decreases adhesive tack strength between EPDM and NR. The surface of EPDM, however, becomes smoother with the addition of the additives. Peel tests and commercial tack tests give similar results in the tack strength between EPDM/NR and EPDM/SBR.     

Carbon black filled powdered natural rubber: Preparation,particle size distribution,mechanical properties,and structures

Carbon black (HAF) filled powdered natural rubber (P(NR/HAF)) was prepared and the particle size distribution, mechanical properties, and micromorphology of P(NR/HAF) were studied. A carbon black–rubber latex coagulation method was developed for preparing carbon black filled free‐flowing, noncontact staining NR powders with particle diameter less than 0.9 mm. A powdering mechanism model was put forward to describe the powdering process, which shows that the key technical points consist in the surfactant with good emulsification properties and the polymer coating resin with good film forming properties. SEM analysis shows that carbon black and rubber matrix have formed a macroscopic homogenization in the P(NR/HAF) particles without contact staining, and carbon black particles are well dispersed in rubber matrix with diameter of about 50–150 nm. P(NR/HAF) vulcanizate showed better mechanical properties than bale natural rubber/carbon black blends (NR/HAF) and simple NR latex/carbon black blends (NRL/HAF), which depends primarily upon the absence of free carbon black, the fine dispersion of filler on the rubber matrix, and the better interaction between carbon black and rubber matrix due to the proper preparation condition of noncontact staining carbon black filled powdered NR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1763–1774, 2006     

Study on polypropylene/natural rubber blend with polystyrene‐modified natural rubber as compatibilizer

Polystyrene‐modified natural rubber (SNR) was prepared in the laboratory and subsequently used as compatibilizer in polypropylene/natural rubber (PP/NR) blends. The effect of SNR (at 5%, 10%, 15% and 20% by volume) in PP/NR (70/30) blend was studied by maintaining the rubber volume while PP volume was replaced by SNR accordingly. The sequence of mixing was found to affect the blend morphology and tensile properties. The effect of curatives on the tensile properties of the blends was also investigated. The addition of curatives into the rubbers in PP/NR/SNR improved the tensile properties significantly compared with the PP/NR reference blend. For a semi‐efficient curative system, SNR loading at 10% gave the best overall tensile properties, while for an efficient curative system, 5% SNR loading resulted in improvements in tensile strength and stiffness of over 20% and 40%, respectively, compared with the reference. © 2002 Society of Chemical Industry     

Studies on oil distribution in polymer blends

Oils and resins are widely used in rubber industries to improve or control the mechanical properties, viscoelastic behavior, processability, and tackiness of a rubber compound. Very few fundamental studies have been reported on the function and the mechanism of oils and resins in a rubber mixture. In this article oil or resin distribution to each phase in an immiscible binary elastomer blend was studied by measuring the change of thermodynamical parameters, such as glass transition temperature, melting point of crystallines, and heat at melt of each polymer component. Several independent approaches give consistent results. It was found that aromatic oil was favorably distributed to the polystyrene-butadiene (SBR) phase of an SBR/natural rubber (NR) blend. Similarly, unequal distribution of resin in a blend was observed for a natural resin (rosin) and a petroleum resin. © 1996 John Wiley & Sons, Inc.     

环氧树脂增强天然橡胶/顺丁橡胶并用胶的性能

采用低相对分子质量的液体环氧树脂(EP)与固化剂混合作为增强体的前驱体,比较了其填充天然橡胶(NR)、顺丁橡胶(BR)及两者并用胶的物理机械性能,考察了EP用量对并用胶及炭黑增强并用胶物理机械性能的影响,并通过扫描电子显微镜表征了填充后的NR、BR及并用胶的微观相态结构。结果表明,EP的加入均可提高NR、BR、NR/BR并用胶的物理机械性能,其中并用胶的拉伸强度提高幅度最大;当EP用量约为24份时,NR/BR并用胶的综合性能最佳;EP可以提高炭黑增强NR/BR并用胶的物理机械性能,但提高幅度不大;EP在NR/BR并用胶中呈现规整的圆球形状,直径为1.0～2.5μm。     

Compatibilization of natural rubber–polyolefin thermoplastic elastomeric blends by phase modification

Natural rubber–polyolefin (70/30) blends have been studied by incorporation of modified rubber and plastic phases with a view to make the heterogeneous phases compatible. The modified rubbers used were epoxidized natural rubber (ENR) and sulfonated ethylene–propylene diene rubber (S-EPDM) at a level of 20 parts. Other rubbers such as chlorinated polyethylene (CPE) and ethylene propylene diene rubbers (EPDM) were also used at a level of 20 parts in the natural rubber–polyethylene (NR/PE) systems. The plastic phase was chemically modified with maleic anhydride (MA) in presence of benzoyl peroxide (BPO) and used at a concentration of 10% of PE, i.e., PEm. The tensile properties such as the modulus, elongation at break, tensile strength, and hysteresis were studied. NR/ENR/PEm/PE shows the greatest improvement in tensile strength (45% over control NR/PE). NR/S-EPDM/PEm/PE also shows similar improvement, although the hysteresis loss decreases. The change in these properties could be related to the adhesive strength. This was found to be improved by the incorporation of modified rubber and modified plastic phases. The best adhesion values have been obtained with NR/ENR/PEm/PE and NR/S-EPDM/PEm/PE. Thus, a correlation between tensile and adhesive strength was obtained for all the systems. The increase in adhesive strength is due to chemical reactions between the various phases. Probable chemical reactions have been suggested. Morphological observations show that the phases are interpenetrating, and this is consistent with the increased tensile strength. The natural rubber–polypropylene (NR/PP) systems do not offer good strength properties with the modified PP and modified rubbers. The adhesive strength also decreases with the incorporation of the modified system. The hysteresis properties show some improvement.     

Hydrogenated natural rubber blends: Aspect on thermal stability and oxidative behavior

Hydrogenated natural rubber (HNR) prepared from natural rubber (NR) is a new sustainable elastomer with excellent thermal properties. This study reports on the effect of vulcanization system and blend ratio on the thermal and oxidative resistance of HNR/NR vulcanizates. The various HNR/NR ratios vulcanized by peroxide and sulfur donor system exhibited the highest retention of tensile strength after thermal aging due to the formation of zinc‐dimethyldithiocarbamate (ZDMDC) which is an efficient antioxidant. The results from thermogravimetric analysis (TGA) indicated that the saturated structure of HNR had higher decomposition temperature and activation energy to enhance the thermal stability of HNR/NR vulcanizates. The initial and maximum decomposition temperatures of NR and HNR phases in vulcanizates were not affected by rubber blend ratio. This suggests that the decomposition pattern of HNR has no influence on another constituent. The increase in HNR content in the blends could retard the ozonolysis resulting in the surface cracking attacked by ozone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PROPERTIES OF POLYPROPYLENE/NATURAL RUBBER/RECYCLE RUBBER POWDER BLENDS

Thermoplastic elastomers have been prepared by blending polypropylene (PP), natural rubber (NR), and recycle rubber powder (RRP). The blends were melt-mixed using a Brabender Plasticorder torque rheometer at 190°C and 50 rpm. A fixed 70:30 blend ratio (wt%) of PP and rubber was prepared. The effect of partial replacement of NR with RRP at a fixed rubber content (NR+RRP), 30 wt% on mechanical properties, swelling behavior, torque development, and morphological properties of PP/NR/RRP blends was studied. Results show that the tensile strength, Young's modulus, and swelling resistance increase with increasing RRP content in the PP/NR/RRP blends whereas the stabilization torque and elongation at break exhibit opposite trend.     

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。     

Effect of surface modification of silicon carbide nanoparticles on the properties of nanocomposites based on epoxidized natural rubber/natural rubber blends

Improvement of the properties of rubber nanocomposites is a challenge for the rubber industry because of the need for higher performance materials. Addition of a nanometer‐sized filler such as silicon carbide (SiC) to enhance the mechanical properties of rubber nanocomposites has rarely been attempted. The main problem associated with using SiC nanoparticles as a reinforcing natural rubber (NR) filler compound is poor dispersion of SiC in the NR matrix because of their incompatibility. To solve this problem, rubber nanocomposites were prepared with SiC that had undergone surface modification with azobisisobutyronitrile (AIBN) and used as a filler in blends of epoxidized natural rubber (ENR) and natural rubber. The effect of surface modification and ENR content on the curing characteristics, dynamic mechanical properties, morphology and heat buildup of the blends were investigated. The results showed that modification of SiC with AIBN resulted in successful bonding to the surface of SiC. It was found that modified SiC nanoparticles were well dispersed in the ENR/NR matrix, leading to good filler‐rubber interaction and improved compatibility between the rubber and filler in comparison with unmodified SiC. The mechanical properties and heat buildup when modified SiC was used as filled in ENR/NR blends were improved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45289.     

用作载重子午线轮胎胎面胶的炭黑填充粉末NR结构与性能研究

以天然胶乳和炭黑N234为原料,采用凝聚共沉法制备炭黑填充型粉末NR[P(NR/CB)],研究炭黑用量和不同配方对胶料硫化特性、物理性能、交联密度、微观结构、Payne效应及动态力学性能的影响,并与采用传统机械混炼法制备的炭黑/NR(CB/NR)进行对比.结果表明,与CB/NR硫化胶相比,P(NR/CB)硫化胶具有较高的拉伸强度、撕裂强度、回弹值和抗湿滑性能以及较低的滚动阻力,耐屈挠性能和耐磨性能大致相当,而动态压缩生热和压缩永久变形则降低了近50%.     

不饱和聚酯树脂改性研究进展

综述了不饱和聚酯树脂(UPR)改性的研究进展。介绍了收缩率控制机理,低收缩研究发展的4个阶段,低收缩剂LSA的典型代表——聚苯乙烯(PS),聚甲基丙烯酸甲酯(PMMA),聚醋酸乙烯(PVAc),PVAc-PS共聚物。讨论了UPR增韧改性方法,提高分子主链对称性,在分子结构中引入长链醇与长链酸,长链醇包括一缩二乙二醇、二缩三乙二醇及聚乙二醇;长链二元酸如己二酸等。此外还可加入热塑性弹性体,如液体橡胶、液体聚氨酯等以形成互穿网络结构增韧UPR。论述了提高UPR阻燃性的2种途径,即选用本质阻燃性树脂和向UPR中添加阻燃剂。介绍了含卤有机阻燃剂、无机阻燃剂、主链或主链与侧链均含磷的阻燃剂和赋予阻燃性的影响因素。介绍了部分采用可降解的植物纤维——竹纤维制备的UP复合材料和木粉改善UPR的性能。这些方法使不饱和聚酯树脂在低收缩性能、力学性能、阻燃性能等方面得到了改善,扩展了其应用范围。     

Mechanical properties of thermoplastic elastomeric blends of chitosan and natural rubber latex

Thermoplastic chitosan/natural rubber blends (Cs/NR) were prepared from natural rubber latex and chitosan by solution casting technique. The blends were characterized by mechanical analysis (stress–strain) and the mechanical properties were found to vary with chitosan/natural rubber ratios. Experimental values were compared with different theoretical models. Effect of thermal aging on mechanical properties was also investigated. Dicumyl peroxide was used as the crosslinking agent. The effect of crosslinking on mechanical properties of Cs/NR has also been studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Natural rubber and butadiene rubber blend using diblock copolymer of isoprene–butadiene as compatibilizer

Blends of natural rubber (NR) and butadiene rubber (BR) have been studied with or without diblock copolymers of isoprene–butadiene (BIR). It was found that NR/BR blends displayed the optimal properties at about 4 wt % of BIR from the tensile measurements of NR/BR blends. Increase of molecular weight of BIR resulted in the decrease of tensile properties, but had no significant effect on their hardness. Abrasion resistance of rubber blends containing BIR was about 30% higher than that without BIR. The molecular weight of BIR did not show a remarkable effect on the abrasion index. Differential scanning calorimetry and dynamic mechanical analyses of rubber blends suggested a two-phase structure even in the presence of BIR. © 1993 John Wiley & Sons, Inc.     

Silica nanoparticles reinforced natural rubber latex composites: The effects of silica dimension and polydispersity on performance

The nano-size autonomous monodisperse silica (AS) particles were prepared by hydrolysis and condensation of tetraethoxysilane using l -lysine as catalyst. The silica/natural rubber (NR) masterbatches were then produced via latex compounding, in which NR latex was mixed with the above AS dispersion. The commercial precipitated silica (PS) was introduced as a control. The effects of both AS and PS particles on the interfacial and mechanical properties of composites were systematically examined. It was found that the AS formed bead-like morphology wherein the clear particle edges can be distinguished in rubber matrix. Compared with PS/NR, the AS/NR composites were proved to possess more bound rubber and weaker filler–filler interaction resulting in higher tensile strength, abrasive resistance, and resilience. Meanwhile, the efficiency of premodified AS and PS surfaces using bis-(3-triethoxysilylpropyl) tetrasulfide on reinforcing the properties of silica/NR composites was studied. The results presented that the overall properties of modified silica/NR vulcanizates were improved significantly. In special, the values of heating building-up and compression set showed an evident decline which was of great significance for tire tread or other rubber products. For the dynamic properties, the magic angle spinning/NR composites had lower rolling resistance. In short, AS may be applied as an ideal substitution of PS in rubber. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47449.     

Preparation,structure, and properties of montmorillonite/cellulose II/natural rubber nanocomposites

In this work, sodium montmorillonite clay was added, as filler, to nanocomposites of natural rubber (NR) and cellulose II (regenerated cellulose) in amounts varying from 0 to 5 phr (per hundred resin). Natural rubber (NR)/cellulose II/montmorillonite nanocomposites were prepared by co‐coagulating NR latex, montmorillonite aqueous suspension and cellulose xanthate. The clay was previously exfoliated in water, and the resulting suspension was then added to the mixture of NR latex with cellulose xanthate. Morphological, rheometric, mechanical, and dynamic mechanical properties were evaluated, and an increase in these properties was observed upon the addition of cellulose and clay nanomaterials to the rubber matrix. The results show the advantage in using cellulose as a nanopolymer as well as MMT as nanofiller. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphology and tensile properties of high-density polyethylene/natural rubber/thermoplastic tapioca starch blends: The effect of citric acid-modified tapioca starch

The effect of citric acid on the tensile properties of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends was investigated. The ratio between HDPE/NR was fixed at 70/30 and used as the matrix system. TPS loadings, after modification with citric acid (TPSCA) and without modification (TPS), were varied from 0 to 30 wt %. The morphologies and tensile properties of HDPE/NR blends were evaluated as a function of TPS loadings. The tensile strength, Young's modulus, and elongation at break were found to decrease with increasing TPS loading. However, a slight improvement in the tensile strength of HDPE/NR/TPSCA blends at 5 and 10 wt % TPS loadings were observed. TPS can be partly depolymerised to produce a low viscosity product when processed with citric acid. TPS with low viscosity can easily disperse in the thermoplastic natural rubber (TPNR) system and reduce the surface tension at the interphase of TPS-HDPE/NR as shown by scanning electron microscopy (SEM). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

聚磷酸三聚氰胺/季戊四醇膨胀型阻燃剂在天然橡胶中的应用

研究了膨胀型阻燃剂聚磷酸三聚氰胺（MPP）/季戊四醇（PER）对天然橡胶（NR）硫化胶的阻燃性能、热稳定性能、残炭形貌及力学性能的影响。结果表明,MPP/PER对NR硫化胶具有很好的阻燃效果,能有效提高NR复合材料的极限氧指数和热稳定性能,降低NR硫化胶的热释放速率,使NR硫化胶的燃烧过程变得稳定;当MPP/PER燃烧时可在NR硫化胶表面形成连续、致密且可隔绝氧气和热量的膨胀炭层;增加MPP/PER的总加入量会对NR硫化胶的力学性能造成一定的负面影响。     

Nanoclay distribution and its influence on the mechanical properties of rubber blends

The distribution of modified and unmodified nanoclays inside the rubber phases of immiscible rubber–rubber blends composed of nonpolar–polar natural rubber (NR)/epoxidized natural rubber (ENR) and nonpolar–nonpolar NR/polybutadiene rubber (BR) was investigated for the first time. The distribution of clays at various loadings in the blends was calculated from the viscoelastic properties of the blends. For example, in the 50 : 50 NR/ENR blend, 42% Cloisite 30B migrated to the NR phase, and 58% went to the ENR phase. However, in the same blend, only 7% Cloisite Na⁺ was found in the NR phase, and 93% was found in the ENR phase. Again, in the 50 : 50 NR/BR blends, the NR phase contained 85% Cloisite 30B, whereas 55% Cloisite Na⁺ migrated to the NR phase. All these observations were explained with the help of viscosity, X‐ray diffraction, and morphology analyses. The effect of the distribution of the clay on the mechanical properties was also discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010