Improved mechanical properties and special reinforcement mechanism of natural rubber reinforced by in situ polymerization of zinc dimethacrylate

The peroxide‐cured natural rubber (NR) was reinforced by in situ polymerization of zinc dimethacrylate (ZDMA). The experimental results showed NR could be greatly reinforced by ZDMA. The tensile strength and the hardness of NR/ZDMA composites increased with the content of ZDMA. The reinforcement mechanism was studied further. Both high crosslinking density provided by ionic crosslinking and strain‐induced crystallization improved the mechanical properties. The crosslinking density was determined by an equilibrium swelling method and the crystallization index was measured by Wide‐angle X‐ray diffraction (WXRD). When the amount of ZDMA was high, the ability of strain‐induced crystallization decreased, due to the strong interactions between the rubber phase and the hard poly‐ZDMA (PZDMA) nanodispersions. At the moment, the increasing ionic crosslinking density made up for the effect of the drop of the strain‐induced crystallization, and played a more important role in the reinforcement. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on wear,cutting and chipping behaviors of hydrogenated nitrile butadiene rubber reinforced by carbon black and in‐situ prepared zinc dimethacrylate

In this study, the wear (Akron and DIN) and the cutting and chipping (C&C) behaviors of hydrogenated nitrile butadiene rubber (HNBR) reinforced by carbon black (N115) and in‐situ prepared zinc dimethacrylate (ZDMA) were investigated. It was validated that ZDMA was more effective than N115 to enhance the wear and C&C resistance of HNBR composites. The Akron wear resistance of the HNBR/N115 composites increased with the content of ZDMA, and the Schallamach ridges observed on the abraded surfaces became less and less clear. With increasing content of ZDMA, the failure mode of the DIN abraded surface underwent the transition from craters to Schallamach ridges, and finally to scratches. The HNBR/N115 composite reinforced by 10 phr ZDMA had the best DIN wear resistance when Schallamach ridges were the dominant failure mode. The use of 30 phr ZDMA can dramatically enhance the C&C resistance of the HNBR/N115 composites. The C&C resistance was suggested to be related to both the variation of the morphology of the C&C ridges and the direction of crack propagation as a function of the content of ZDMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of graphene functionalized with zinc dimethacrylate on the mechanical and thermal properties of natural rubber nanocomposites

An effective approach is developed to synthesize zinc dimethacrylate functionalized graphene (ZDMA‐GE) as reinforcing nanofiller for natural rubber (NR). The morphology and structure of ZDMA‐GE were characterized to confirm the exfoliation and functionalization of GE. The as‐prepared nanocomposites were investigated by transmission electron microscopy, mechanical analysis, crosslinked network analysis, and the analysis of thermal conductivity. The results demonstrated that there is strong interfacial interaction between GE and rubber matrix due to good dispersion and special two‐dimensional structure of GE. The crosslink density of the nanocomposites is greatly improved with the introduction of ZDMA‐GE because of the homopolymerization and graft polymerization of ZDMA. It is also noticed that the tensile strength, tear strength, and modulus at 300% elongation of NR nanocomposites with 15 phr ZDMA‐GE have been improved by 133, 42, and 174%, respectively. The thermal conductivity of nanocomposites with 40 phr ZDMA‐GE is enhanced 1.3 times as that of the pure NR. This remarkable improvement is attributed to the formation of covalent crosslinked network and ionic crosslinked network, good dispersion of GE, and efficient interfacial interaction between GE and NR matrix. This method provides the potential applications of functionalized GE in the polymer composites. POLYM. COMPOS., 36:1775–1785, 2015. © 2014 Society of Plastics Engineers     

Crosslink network evolution of nature rubber/zinc dimethacrylate composite during peroxide vulcanization

In this article, we investigated the evolution of the crosslink networks in nature rubber (NR) which is filled with in situ zinc dimethacrylate (ZDMA) during vulcanization. The results revealed that a primary network dominated by the ionic bond could be formed in the first 1 min, while the backbone of the covalent crosslink network was not formed. The ionic crosslinks, cooperating with some other physical crosslinks and some primary covalent crosslink points, play an important role in supporting the crosslink backbone of the composite in this period. This primary network was strong enough to bear the force exerted by the moving die of the Rheometer and to enable the composite that do not dissolve in toluene. After that, both the covalent crosslinking of NR molecules and polymerization of ZDMA react rapidly to give a birth to the fundamental network of the composites. Fourier transform infrared spectroscopy and differential scanning calorimeter were also used to investigate the curing reaction of the NR/ZDMA compounds. After ZDMA reaching a considerable conversion, the substantial covalent crosslinking reaction starts to be initiated. These results support the primary network dominated by the ionic bond formed in the first 1 min. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Reinforcement of EPDM by in situ prepared zinc dimethacrylate

The mechanical properties and crosslink density of peroxide‐cured ethylene‐propylene‐diene rubber (EPDM) reinforced with zinc dimethacrylate (ZDMA) were studied. ZDMA was in situ prepared in EPDM matrix through the neutralization reaction of zinc oxide (ZnO) and methacrylate acid (MAA). The effect of ZnO/MAA amount and molar ratio of ZnO/MAA on the properties of the EPDM vulcanizate were investigated in detail. The experimental results showed that EPDM can be greatly reinforced by ZDMA. The excess amount of ZnO considerably increases the tensile strength of the EPDM vulcanizate to reach as high as 37 MPa, whereas its elongation at break keeps over 350%. The process of in situ formation of ZDMA in the EPDM compound was verified by WAXD. Such vulcanizate contains both covalent crosslinks and ionic crosslinks. Crosslink density was determined by an equilibrium swelling method. Dependence of crosslink density on the amount and molar ratio of ZnO/MAA was studied and the extraordinary high tensile strength of the EPDM/ZDMA vulcanizate was related to ionic crosslink density. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1339–1345, 2002; DOI 10.1002/app.10112     

ZDMA补强EVA/CPE/NBR共混型热塑性硫化胶的Payne和Mullins效应研究

采用动态硫化法制备乙烯-醋酸乙烯酯共聚物(EVA)/氯化聚乙烯(CPE)/丁腈橡胶(NBR)共混型热塑性硫化胶(TPV),研究TPV的应力-应变行为、微观相结构、Payne和Mullins效应。结果表明:甲基丙烯酸锌(ZDMA)补强TPV的储能模量随应变的增大而显著下降,表现出典型的Payne效应;TPV存在明显的Mullins效应,相同拉伸比下,与EVA/CPE/NBR TPV相比,ZDMA补强TPV的最大应力、瞬时残余应变、内耗、损耗因子和软化因子均有所提高。     

Effect of carbon black loading on curing characteristics and mechanical properties of waste tyre dust/carbon black hybrid filler filled natural rubber compounds

Curing characteristics, tensile properties, fatigue life, swelling behavior, and morphology of waste tire dust (WTD)/carbon black (CB) hybrid filler filled natural rubber (NR) compounds were studied. The WTD/CB hybrid filler filled NR compounds were compounded at 30 phr hybrid filler loading with increasing partial replacement of CB at 0, 10, 15, 20, and 30 phr. The curing characteristics such as scorch time, t₂ and cure time, t₉₀ decreased and increased with increment of CB loading in hybrid filler (30 phr content), respectively. Whereas maximum torque (M_HR) and minimum torque (M_L) increased with increasing CB loading. The tensile properties such as tensile strength, elongation at break, and tensile modulus of WTD/CB hybrid filler filled NR compounds showed steady increment as CB loading increased. The fatigue test showed that fatigue life increased with increment of CB loading. Rubber–filler interaction, Q_f/Q_g indicated that the NR compounds with the highest CB loading exhibited the highest rubber–filler interactions. Scanning electron microscopy (SEM) micrographs of tensile and fatigue fractured surfaces and rubber–filler interaction study supported the observed result on tensile properties and fatigue life. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of Carbon Black on the Properties of HNBR Reinforced by in-situ Prepared ZDMA

Hydrogenated nitrile rubber (HNBR) filled with carbon black (CB) and in-situ prepared zinc dimethacrylate (ZDMA) was prepared by mechanical mixing method. The effects of carbon black on the vulcanization characteristics, physical and dynamic mechanical properties, thermal stability and the fracture surface morphologies of HNBR reinforced by in-situ prepared ZDMA (HNBR/ZDMA) were investigated. The results showed that, for given ZDMA loading (50 phr), with the increasing CB content, the scorch time extended, tensile strength, tear strength and elongation at break increased at first and then decreased, while the modulus at 100% and hardness increased. The comprehensive properties of the HNBR/ZDMA/CB was optimal, when the content of CB was 10 phr. DMA analysis showed that the addition of CB could enhance the storage modulus (E’) & loss modulus (E”), and decreased the glass transition temperature (Tg) of HNBR/ZDMA. TGA analysis revealed that the addition of CB could improve the thermal stability of HNBR/ZDMA. SEM analysis showed that the CB dispersed well in the HNBR/ZDMA, and the CB could improve the dispersion of ZDMA effectively.     

Curing characteristics and mechanical properties of rattan‐powder‐filled natural rubber composites as a function of filler loading and silane coupling agent

Curing characteristics, tensile properties, morphological studies of tensile fractured surfaces using scanning electron microscopy (SEM), and the extent of rubber filler interactions of rattan‐powder‐filled natural rubber (NR) composites were investigated as a function of filler loading and silane coupling agent (CA). NR composites were prepared by the incorporation of rattan powder at filler loading range of 0–30 phr into a NR matrix with a laboratory size two roll mill. The results indicate that in the presence of silane CA, scorch time (t_s2), and cure time (t₉₀) of rattan‐powder‐filled NR composites were shorten, while, maximum torque (M_H) increased compared with NR composites without silane CA. Tensile strength and tensile modulus of composites were enhanced whereas elongation at break reduced in the presence of silane CA mainly due to increase in rubber‐filler interaction. It is proven by SEM studies that the bonding between the filler and rubber matrix has improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

ZDMA/NR复合材料的性能研究

以甲基丙烯酸锌（ZDMA）为补强剂,研究硫化剂DCP用量、ZDMA用量和硫化时间对ZDMA/NR复合材料物理性能的影响.结果表明,在硫化剂DCP存在的情况下,ZDMA对NR具有明显的补强作用,ZDMA/NR复合材料的物理性能和耐热空气老化性能明显改善;当ZDMA和硫化剂DCP的用量分别为15和1.5份、硫化时间为1.5t90时,ZDMA/NR复合材料具有较好的综合物理性能.     

原位生成甲基丙烯酸锌对填充天然橡胶力学性能的影响

考察了氧化锌用量和碳酸钙用量对原位生成甲基丙烯酸锌增强天然橡胶的力学性能的影响,以及甲基丙烯酸锌对白炭黑填充天然橡胶和胶粉填充天然橡胶力学性能的影响。研究表明,原位生成甲基丙烯酸钙的增强作用比甲基丙烯酸锌差,与前者的交联反应热很小有关;甲基丙烯酸锌能够大大加快白炭黑填充天然橡胶的硫化速度,对胶粉填充天然橡胶具有明显的增强作用。     

Effects of quasi‐nanogel particles on the rheological and mechanical properties of natural rubber: A new insight

The influence of sulfur‐crosslinked, quasi‐nanosized gels on the rheological and mechanical properties of raw natural rubber (NR) was investigated. Latex gels with different crosslink densities were prepared through the variation of the sulfur‐to‐accelerator ratio. These gels were characterized by dynamic light scattering, solvent swelling, and mechanical properties. The gels were mixed with raw NR latex at concentrations of 2, 4, 8, and 16 phr, and their effect on the rheological properties of NR was studied by Monsanto processability tester. The presence of gel in raw NR reduced the apparent shear viscosity and die swell considerably. Initially, the viscosity decreased up to a 8 phr gel loading and then increased with an increase in the gel loading. However, the change in the viscosity was related to the crosslink density of the gels. A new empirical equation relating the viscosity, volume fraction of the gels, and crosslink density was proposed. The die swell of gel‐filled raw NR was at least 10% lower than that of unfilled raw NR and decreased with an increase in the gel loading. The effect of the gels on the die swell properties was explained through the calculation of the principal normal stress difference of gel‐filled NR systems. Scanning electron photomicrographs of the extrudates revealed much better surface smoothness for the gel‐filled virgin rubber systems than for the unfilled rubber. The addition of the gels to raw NR increased the modulus and tensile strength, whereas the elongation at break decreased. The effect of the gels on the dynamic mechanical properties of NR was also investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and dynamic mechanical properties of natural rubber blended with waste rubber powder modified by both microwave and sol–gel method

Waste rubber powder (WRP) was modified by microwave, sol–gel method, and both microwave and sol–gel method, respectively. The mechanical and dynamic mechanical properties of natural rubber (NR)/modified WRP composite were investigated. The influence of bis‐(3‐(triethoxysilyl)‐propyl)‐tetrasulfide (TESPT) content on curing characteristics and mechanical properties of vulcanizate was also studied. The results showed that NR/WRP modified by both microwave and sol–gel method composite owned the best mechanical properties. Rubber processing analyzer was used to characterize the interaction between silica and rubber chains and the dispersion of silica. With increase of TESPT content, the Payne effect decreased. Scanning electron microscopy indicated the coherency and homogeneity of in situ generated silica filled vulcanizate. Dynamic mechanical analyzer showed that NR/WRP modified by both microwave and sol–gel method composite with 5 phr TESPT exhibited the lower tan δ at temperature range of 50–80°C, compared with composite without TESPT and the higher tan δ at temperature of 0°C, compared with the conventional modification of WRP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Viscoelasticity behaviors of lightly cured natural rubber/zinc dimethacrylate composites

Zinc dimethacrylate (ZDMA) can be polymerized during peroxide curing to form the polymerized ZDMA (PZDMA) at nanoscales. At the same time, the covalent crosslink of the rubber matrix and ionic crosslink introduced by the graft‐PZDMA also are formed. The structure evolution of this type of composites is complex. In this article, the dynamic viscoelasticity characteristics of lightly cured ZDMA/natural rubber (NR) composites were investigated using a Rubber Process Analyzer 2000 (RPA2000). Our goal was to study the internal structures of this type of composites in an early curing stage. The dynamical viscoelasticity of the composites cured for 1 min was focused. The results of RPA2000 indicated that the PZDMA could act as particles to form a strong filler–filler structure which resulted in apparent Payne effect. A “primary network” structure might be formed which contained covalent crosslink points, ionic crosslinks, physical adsorption, and PZDMA. The stress‐softening behavior was also investigated. At last, the scanning electron microscope analysis verified that most of the ZDMA had been polymerized to form PZDMA “nanoparticle” when the composites were cured for 1 min. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene–butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively increased at PSi loadings of 30–75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate properties of the FASi‐filled vulcanizates appeared to be very similar to those of the PSi‐filled vulcanizates at silica contents of 0–30 phr. Above these concentrations, the properties of the PSi‐filled vulcanizates improved, whereas those of the FASi‐filled compounds remained the same. In the SBR system, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler–filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0–30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119–2130, 2004     

Dramatic influence of curing temperature on micro–nano structure transform of HNBR filled with zinc dimethacrylate

The influence of the curing temperature on micro‐nano structure transform of hydrogenated nitrile‐butadiene rubber (HNBR) reinforced by zinc dimethacrylate (ZDMA) through in situ polymerization was studied by means of Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. The results showed that both the amount and diameter of the poly‐ZDMA aggregates increased and the graft ratio of poly‐ZDMA decreased with the increase of curing temperature. Meanwhile, with the increase of curing temperature, the maximum torque of the curing curve, the crosslinking density (especially for the ionic crosslinking density), and the mechanical properties of HNBR/ZDMA composite decreased significantly. We put forward a possible mechanism that can well explain the phenomenon observed in this work. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical,thermal, morphological,and curing properties of geopolymer filled natural rubber composites

The main objective of this work was to investigate influence of natural rubber (NR) types on mechanical, thermal, morphological, and curing properties together with relaxation behavior of geopolymer filled NR composites with and without bis(triethoxysilylpropyl) tetrasulfide (TESPT) silane coupling agent. Three alternative types of NR: unmodified NR, and epoxidized NR with 25 (ENR-25) or 50 mol % epoxide (ENR-50) were exploited. Rubber compounds filled with GP particles were prepared in an internal mixer at 60 °C and 130–150 °C for the ones with and without TESPT, respectively. It was found that incorporation of GP significantly affected cure characteristics and mechanical properties of the rubber composites. That is, decreasing cure time was observed from 11.6, 3.2, and 7.0 min in gum NR, ENR-25, and ENR-50 to 6.9, 2.1, and 5.0 min in NR/GP, ENR-25/GP, and ENR-50/GP compounds, respectively. Furthermore, the ENR-25/GP and ENR-50/GP composites showed finely dispersed GP particles which indicate high filler–rubber interactions. The in situ silanization with TESPT in rubber composites enhanced the mechanical properties of NR/GP and ENR-25/GP composites but no such enhancement was found in the ENR-50/GP composite. This matched the observations of Payne effect, maximum tan δ, and stress relaxation properties of the composites. We found that the ENR-25/GP composites exhibited the best overall properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47346.     

Enhanced mechanical properties of graphene/natural rubber nanocomposites at low content

Graphene/natural rubber (GE/NR) nanocomposites were prepared by a modified latex mixing method combined with in situ chemical reduction. It was found that the GE nanosheets are well dispersed and have strong interfacial interaction with NR. Thus, adding a low content of GE can remarkably increase the tensile strength and the initial tensile modulus of NR. With incorporation of as low as 0.5 phr of GE, a 48% increase in the tensile strength and an 80% increase in the initial tensile modulus are achieved without sacrificing the ultimate strain. But further increasing the GE loading degrades the tensile strength and the ultimate strain. Dynamic mechanical measurement indicates that the storage modulus of the nanocomposites is greatly enhanced with addition of GE, while the loss tangent peak is depressed due to the reduced mobility of the rubber molecules. The reinforcement effect of GE on NR is interpreted as a change in the strain induced crystallization and network structure of the nanocomposites, based on the analysis of Mooney ? Rivlin plots and the tube model.© 2013 Society of Chemical Industry     

Dispersion and properties of natural rubber‐montmorillonite nanocomposites fabricated by novel in situ organomodified and latex compounding method

Natural rubber (NR)‐montmorillonite (MMT) nanocomposites were prepared by a novel in situ organomodified and latex compounding method, followed by melt compounding technique. Effects of cationic surfactant on MMT dispersion, curing characteristic, mechanical, and dynamical properties were investigated. The number of layers in the layered MMT stack was determined by Small‐Angle X‐Ray Scattering (SAXS). The dispersion of MMT tends to form high ordered structure in NR‐MMT masterbatch when cationic surfactant of more than 4 phr was used. The morphology of Na‐MMT shows partly intercalated and exfoliated structure in the matrix after mixing and hot pressing process with reduced number of layers compared to the pristine MMT. The use of cationic surfactant over 4 phr introduces a plasticizing effect resulting in the reduction of crosslink density, hardness and modulus, but increase in tensile strength due to higher interfacial adhesion between NR and MMT as determined by Maeir‐Goritz model and Field Emission Scanning Electron Microscopy (FESEM). The optimum cationic surfactant loading is observed at 4 phr with the highest stable bonds, which result in the highest crosslink density, tear strength and storage modulus while the lowest Payne effect and tan delta at 60°C. POLYM. ENG. SCI., 59:1830–1839, 2019. © 2019 Society of Plastics Engineers     

Natural rubber/ethylene propylene diene blends for high insulation iron crossarms

This research studied the composition and behavior of natural rubber (NR) and ethylene propylene diene monomer (EPDM) blends at various carbon black concentrations (0–30 phr) in terms of electrical resistivity, dielectric breakdown voltage testing, and physical properties. The blends having electrical properties suitable for application in high‐insulation iron crossarms were selected for investigation of compatibility and increased physical properties. The effect of the homogenizing agent concentration on improvement of compatibility of blends was studied by scanning electron microscopy, pulsed nuclear magnetic resonance spectroscopy, and rheology techniques. We also examined mechanical properties such as tensile strength, tear strength, elongation at break, and hardness. The NR/EPDM blends filled with a fixed concentration of silica were investigated for ozone resistance. A carbon black content as high as 10 phr is still suitable for the insulation coating material, which can withstand electrical voltage at 10 kVac. Addition of the homogenizing agent at 5 phr can improve the mechanical compatibility of blends, as evidenced by the positive deviation of shear viscosity of the rubber blend, that is, the calculated shear viscosity being higher than that of experimental data. Moreover, the pulsed NMR results indicated that the spin‐spin relaxation (T₂) of all three components of the rubber blend was compressed upon the addition of the homogenizing agent. The ratio of NR/EPDM in the blend to best resist the ozone gas is 80/20 with the addition of silica of 30 phr into the blend. Also, the NR/EPDM filled with silica had a decreased change in thermal and mechanical properties of blends after thermal aging. The synergistic effect of silica content and high NR content (80) in 20 phr EPDM could improve antioxidation by ozone in the absence of a normal antioxidant for natural rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3401–3416, 2004