Natural rubber-graft-poly(2-hydroxyethyl acrylate) on cure characteristics and mechanical properties of silica-filled natural rubber composites

The grafting of poly(2-hydroxyethyl acrylate) onto natural rubber (NR-g-PHEA) was used to compatibilize NR composites with silica filler. The NR/silica compounds were prepared with various grafting percentages of NR-g-PHEA (0, 6.5, 10.5, and 14.5%) and fixed amounts of 3 parts per hundred of rubber (phr) NR-g-PHEA and 20 phr silica. The cure characteristics were examined using a moving die rheometer. The physicomechanical properties of NR/silica composites were determined in terms of tensile strength, bound rubber content, and dynamic mechanical analysis. Thermal properties were assessed with thermogravimetric analysis. The results showed that scorch time and cure time tend to decrease with the level of grafting in NR-g-PHEA. The NR-g-PHEA decreased tan δ, whereas bound rubber content in NR/silica compounds increased, which indicates improved silica dispersion in the NR matrix. The mechanical properties improved with level of grafting in NR-g-PHEA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48738.     

The influence of surface structure of low industrial grade seaweed and semi‐refined carrageenan on mechanical and physical properties of natural rubber latex composites

Composites consisting of natural rubber (NR) latex as their matrix and low industrial grade seaweed (LIGS) and its extractive (semirefined carrageenan, SRC‐LIGS) as the filler were prepared via normal prevulcanization process. An analysis regarding the particle size and morphology of seaweed (LIGS and SRC‐LIGS), as well as surface properties and mechanical properties (tensile and tear properties) of NR latex composites, was consequently generated. Furthermore, post‐processing treatment for NR latex composites have also been studied, specifically involving leaching, heat aging, water absorption, and soil burial. The particle size of LIGS and SRC‐LIGS obtained was recorded to be lower than 100 μm. Thus, the results are indicative of SRC‐LIGS's role in improving the thermal properties of NR latex composites. After 8 weeks of soil burial, the incorporation of LIGS and SRC‐LIGS into the NR latex composites has accelerated biodegradation processes, thus highlighting their advantage as biodegradable fillers. These properties have consequently contributed to SRC‐LIGS/NR latex composites as a potential composite for use in biodegradable applications, such as polybag for pottery and plants. J. VINYL ADDIT. TECHNOL., 25:278–286, 2019. © 2018 Society of Plastics Engineers     

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。     

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.     

Structure–property relationships of silica/silane formulations in natural rubber,isoprene rubber and styrene–butadiene rubber composites

The mechanical performance of natural rubber (NR), synthetic poly-isoprene rubber (IR), and styrene–butadiene rubber (SBR) composites filled with various silica/silane systems is investigated. The results are analyzed by referring to micro-mechanical material parameters, which quantify the morphological and structural properties of the polymer and filler network. These are obtained from fits with the dynamic flocculation model (DFM) describing the strongly nonlinear quasi-static stress–strain response of filler-reinforced elastomers as found from multihysteresis measurements of the investigated compounds. We focus on the reinforcement mechanisms of silica compounds with coupling and covering silane, respectively. The fitted material parameters give hints that the coupling silane provides a strong chemical polymer–filler coupling, which is accompanied by improved strength of filler–filler bonds for all three rubbers types. This may result also from the chemical coupling of short chains bridging adjacent silica particles. It implies larger stress values for the coupling silane and, in the case of NR and IR, a more pronounced “Payne effect” compared to the covering silane. In contrast, for SBR, the coupling silane delivers a lower Payne effect, which is explained by differences in the compatibility between rubber type and silane-grafted silica surface. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48435.     

Simultaneous reduction and surface functionalization of graphene oxide and the application for rubber composites

The simultaneous reduction and functionalization of graphene oxide (GO) was realized through a chemical grafting reaction with a functionalization agent N,N-bis(3-aminopropyl)methylamine (APMEL). The reduced and functionalized reduced GO (rGO-APMEL) sheets can be well dispersed in water without any added surfactant and the formed stable rGO aqueous dispersion can be kept for a long time, which can be used for the preparation of rubber–graphene (GE) composites by latex mixing. The electrostatic interaction between rGO–APMEL (positively charged) and natural rubber latex particles (negatively charged) leads to the formation of NR/rGO–APMEL composites with strong interaction. Compared with blank NR, the tensile strength and modulus for NR/rGO–APMEL increase with the rGO–APMEL loading. Especially, when the filler content is 5 phr, the tensile strength of NR/rGO–APMEL-5 increases by 32.7%, as a control the tensile strength of NR/GO-5 and NR/rGO-5 decrease by 20.1 and 15.6%, respectively. The entanglement-bound rubber tube model was used to analyze the reinforcing effect of GE on NR/rGO–APMEL nanocomposites at a molecular level. This study may provide us a novel approach to prepare well dispersed and exfoliated rGO–polymer nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47375.     

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     

Preparation and performance of oleylamine modified silica-reinforced natural rubber composites

Oleylamine (OA) modified silica (SiO₂-g-OA) was prepared using γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) and OA, silica/natural rubber (NR) and SiO₂-g-OA/NR composites were prepared by mechanical blending in an internal mixer, and SiO₂-g-OA was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analyzer, and contact angle analyzer. The mechanical properties, abrasion resistance, curing characteristics, Payne effect, and morphology of silica/NR and SiO₂-g-OA /NR composites were investigated using universal testing machine, Akron abrasion tester, rubber processing analyzer, and scanning electron microscope, respectively. The results showed that SiO₂-g-OA became more hydrophobic and had better compatibility with NR. Moreover, SiO₂-g-OA/NR had weaker Payne effect, better vulcanization performance, and more excellent mechanical properties. As the content of filler was more than 30 phr, SiO₂-g-OA/NR had lower rolling resistance and higher wet skid resistance. Compared with silica modified by other coupling agents, SiO₂-g-OA had the best reinforcement effect on NR.     

ABS modified with hydrogenated polystyrene‐grafted‐natural rubber

Natural rubber (NR) latex was grafted by emulsion polymerization with styrene monomer, using cumene hydroperoxide/tetraethylene pentamene as redox initiator system. The polystyrene‐grafted NR (PS‐g‐NR) was hydrogenated by diimide reduction in the latex form using hydrazine and hydrogen peroxide with boric acid as a promoter. At the optimum condition for graft copolymerization, a grafting efficiency of 81.5% was obtained. In addition, the highest hydrogenation level of 47.2% was achieved using a hydrazine:hydrogen peroxide molar ratio of 1:1.1. Hydrogenation of the PS‐g‐NR (H(PS‐g‐NR)) increased the thermal stability. Transmission electron microscopy analysis of the H(PS‐g‐NR) particles revealed a nonhydrogenated rubber core and hydrogenated outer rubber layer, in accordance with the layer model. The addition of H(PS‐g‐NR) at 10 wt % as modifier in an acrylonitrile–butadiene–styrene (ABS) copolymer increased the tensile and impact strengths and the thermal resistance of the ABS blends, and to a greater extent than that provided by blending with NR or PS‐g‐NR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Bentonite as a reinforcing and compatibilizing filler for natural rubber and polystyrene blends in latex stage

Bentonite clay was used as a reinforcing and compatibilizing filler for natural rubber/polystyrene (NR/PS) blend via latex blending process. The reinforcing and compatibilizing performance of bentonite clay in the NR/PS blends were evaluated. The improvement of the mechanical properties of NR/PS blends with the weight ratios of 90/10, 80/20, and 70/30 was found with the addition of 3 and 5 parts per hundred rubber (phr) clay. The characterization by using Fourier transform infrared spectroscopy and X‐ray diffraction (XRD) gave the evidence that the silicate layer was intercalated by NR and PS molecular chains. The morphology of tensile fracture surface by scanning electron microscope showed the separated phase boundaries of PS and NR blend and gradual disappearance with the bentonite content. This could be implied that the bentonite contributes to the compatibilization between PS and NR. The compatibilization action of the bentonite clay was also reflected by the shift of glass transition temperature (T_g) of NR to higher temperatures than those of the blends. These results suggested that the tensile and tear properties of the blends were controlled by compatibility between NR and PS. The most enhanced properties of blends were found with the addition of 3 phr bentonite clay. POLYM. ENG. SCI., 54:1436–1443, 2014. © 2013 Society of Plastics Engineers     

硅藻土/白炭黑复合填料的补强性研究

为拓展硅藻土在高分子复合材料中的应用,将硅藻土/白炭黑填充到天然橡胶/丁苯橡胶/顺丁橡胶中制备了复合材料。通过RPA2000和扫描电镜分析了复合填料的Payne效应和分散性,考察了硅藻土用量对复合材料工艺性能、力学性能、耐磨耗性能影响。结果表明:少量硅藻土的加入有利于白炭黑在橡胶中的分散,能降低复合材料的门尼粘度和Payne效应,提高复合材料的硫化速度,缩短硫化时间,复合填料的补强效果较好;随着硅藻土用量的增加,复合填料容易聚集,其力学性能呈下降趋势,而磨耗性能变化不大;当硅藻土用量10~20份时,复合材料的综合性能最好。     

Properties of natural rubber composites reinforced with silica or carbon black: influence of cure accelerator content and filler dispersion

Filler dispersion is a critical factor in determining the properties of filled rubber composites. Silica has a high density of silanol groups on the surface, which lead to strong filler–filler interactions and a poor filler dispersions. A cure accelerator, N‐tert‐butyl‐2‐benzothiazole sulfenamide (TBBS), was found to improve filler dispersion in silica‐filled natural rubber (NR) compounds. For the silica‐filled NR compounds without the silane coupling agent, the reversion ratio generally increased with increase in TBBS content, whereas those of the silica‐filled NR compounds containing the silane coupling agent and carbon black‐filled NR compounds decreased linearly. The tensile strength of the silica‐filled NR vulcanizate without the silane coupling agent increased as the TBBS content increased, whereas carbon black‐filled samples did not show a specific trend. The experimental results were explained by TBBS adsorption on the silica surface and the improvement of silica dispersion with the aid of TBBS. Copyright © 2003 Society of Chemical Industry     

Preparation and morphological characterization of two- and three-component natural rubber-based latex particles

Different emulsion polymerization processes allowed variation in the microstructure of composite natural rubber (NR)-based latex particles. A prevulcanized and a not-crosslinked natural rubber latex were coated with a shell of crosslinked poly(methyl methacrylate) (PMMA) or polystyrene (PS). The bipolar redox initiating system tert-butyl hydroperoxide/tetraethylene pentamine promoted a core–shell arrangement. Furthermore, PS subinclusions were introduced into the NR core. The initiators used for the subinclusion synthesis were azobisisobutyronitrile at high temperature and a redox initiation system consisting of tert-butyl hydroperoxide/dimethylaniline at low temperature. The morphology of the resulting latex interpenetrating networks (IPN) was characterized by transmission electron micros-copy (TEM) and scanning electron microscopy (SEM). Different staining methods allowed us to increase the contrast between the NR phase and the secondary polymers in the composite latex particles. A semicontinuous feeding process decreased the PS subinclusions size by a factor of 6 in comparison with a batch reaction. Depending on the NR/styrene swelling ratio, the crosslinking degree, and the polymerization temperature used, distinct differences of the phase arrangement of polymers in the latex particles were revealed. © 1996 John Wiley & Sons, Inc.     

Effect of the composition of structured rubber particles on the toughness of poly(methylmethacrylate)

Composite natural rubber (NR) and monodisperse poly(n-butylacrylate) (PBuA) based latex particles were tested as possible impact modifiers for a poly(methylmethacrylate) (PMMA) matrix. A continuous extrusion process was used for the incorporation of wet latexes directly into a twin-screw extruder. All latexes had been coated by a PMMA shell. Furthermore, polystyrene (PS) subinclusions were introduced into the NR core. The impact resistance of the prepared PMMA blends can be most effectively improved by NR particles containing a large weight fraction of compatibilising PMMA in the shell. The degree of crosslinking of the shell polymer has to be restricted. PBuA based latex particles of 180 nm in size are ineffective to toughen the PMMA matrix. The degree of grafting of the NR phase in core–shell particles containing PS subinclusions is not crucial. Scanning electron microscopy was used to analyse the failure processes in composite rubber particle toughened PMMA blends at fast (impact conditions) and slow (tensile testing) deformation speeds.     

Effect of NaOH and Si69 treatments on the properties of fly ash/natural rubber composites*

Natural silica in fly ash (FA) particles of 30 and 60 phr were incorporated as reinforcing filler in natural rubber (NR) compounds. Improvements of cure characteristics and mechanical properties of the FA/NR composites were expected by surface treatment of the FA particles, this being carried out using various contents of bis‐(3‐triethoxysilylpropyl) tetrasulfane (Si69), as a chemical silane coupling agent, and sodium hydroxide (NaOH) solution. The results suggested that the Si69 coupling agent was a satisfactory property promoter in the FA/NR composites through C S bonding with rubber molecules and siloxane linkages with FA particles. Using NaOH solution did not improve the mechanical properties of the composites. The mechanical properties of the FA/NR composites appeared to increase at low Si69 concentrations of 2.0–4.0 wt%, but decreased at high Si69 loadings of 6.0–8.0 wt%. The decrease in mechanical properties resulted from a reduction of crosslink density and a formation of flexible polysiloxane from the self‐condensation reaction of the Si69. The presence of Si69 was observed to interfere with the sulphur crosslink formation. No synergetic effect on the properties of the rubber composites was observed when using a mixture of NaOH and Si69. This article recommends concentrations of 2.0–4.0 wt% Si69 to be introduced into the FA/NR composites to achieve the optimum properties. POLYM. COMPOS., 27:30–40, 2006. © 2005 Society of Plastics Engineers     

Study on Tensile,Electrical, and Thermal Properties of Aluminium Particle Filled Natural Rubber (NR) and Ethylene-Propylene-Diene Terpolymer (EPDM) Composites

Comparative studies on the effect of aluminium particles in natural rubber (NR) and ethylene-propylene-diene terpolymer (EPDM) were conducted. The incorporation of aluminium particles in NR or EPDM composites increased the cure time, t ₉₀, and scorch time, t _S2 . At a fixed filler loading, EPDM composites exhibited longer t ₉₀ and t _S2 than NR composites. The results also indicate that the maximum torque, M _H of aluminium filled NR and EPDM composites increase with increasing filler loading. For tensile properties, EPDM composites show lower tensile properties than NR composites. Thermogravimetric analysis (TGA) results show that aluminium filled EPDM composites have better thermal stability than aluminium filled NR composites.

The results for electrical properties indicate that the electrical properties of aluminium filled NR and EPDM composites increase with increase in filler loading.     

Interfacial interactions and properties of natural rubber–silica composites with liquid natural rubber as a compatibilizer and prepared by a wet‐compounding method

Natural rubber–silica [W(NR–SiO₂)] composites were prepared by wet‐compounding technology with liquid natural rubber (LNR) as a compatibilizer. The effects of the LNR content and wet‐compounding technology on the filler dispersion, Payne effect, curing characteristics, mechanical properties, and interfacial interactions were investigated. The results show that the incorporation of LNR promoted vulcanization and decreased the Payne effect of the W(NR–SiO₂) composites. With the addition of 5 phr LNR, the remarkable improvements in the mechanical properties of the W(NR–SiO₂) vulcanizates were correlated with the improved silica dispersion and strengthened interfacial bonding. Furthermore, the W(NR–SiO₂) vulcanizates containing LNR exhibited improvements in both the wet‐skid resistance and rolling‐resistance performance. The interfacial interactions, quantitatively evaluated by the Mooney–Rivlin equation and Lorenz–Park equation on the basis of the rubber elasticity and reinforcement theory, were strengthened in the presence of LNR. Accordingly, an interfacial structural model was proposed to illustrate the improvements in the mechanical properties of the W(NR–SiO₂) composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46457.     

The effect of epoxidized natural rubber on mechanical properties of siliceous earth/natural rubber composites

Siliceous earth (SE) is a kind of mineral consisting of lamellar kaolinite, muscovite (aluminum silicate) and corpuscular silica. Natural rubber (NR) composites containing NR as matrix, epoxidized natural rubber (ENR) as compatibilizer and SE as filler were produced by latex coagulating process and cured using a conventional sulfuric system. Monsanto measurements have shown that the ENR accelerates the vulcanization reaction and gives rise to a marked increase of the torque. The results of physico-mechanical properties of NR vulcanizates show that, when SE modified by silane coupling agent and in the meanwhile adding 4 phr of ENR as compatibilizer, maximum tensile strength, elongation at break, reinforcing index (M300/100) of NR/SE vulcanizates were obtained. The dynamic-mechanical properties exhibit the addition of ENR can enhance wet grip characteristics and reduce rolling resistance by lowering tan δ values at 60 °C and increasing tan δ values at 0 °C of NR compounds. The overall results show that properties of SE-reinforced NR substantially improved by adding ENR as compatibilizer. The addition of silane coupling agent and combining an appropriate amount of ENR would be better choice to improve the properties of NR/SE compounds.     

Effect of carbon nanotubes decorated with silver nanoparticles as hybrid filler on properties of natural rubber nanocomposites

Decoration of carbon nanotube (CNT) surfaces with silver nanoparticles (AgNPs) was performed using N,N-dimethylformamide reducing agent. The CNT-decorated with AgNP (CNT-AgNP) was then used to prepare natural rubber (NR) nanocomposites via latex mixing method. Cure characteristics, mechano-thermal relaxation, electrical conductivity, and thermal properties of the composites were investigated. It was found that the CNT-AgNP gave cure properties improved over plain NR compounds in terms of scorch time, degree of vulcanization, and activation energy. In addition, temperature scanning stress relaxation measurement revealed stronger network formation after incorporation of AgNP into the NR matrix due to the interaction among CNT and AgNP particles. This also provided high conductivity and low percolation threshold concentration for the CNT-AgNP filled NR, relative to plain CNT filled NR composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47281.     

Novel CNC/silica hybrid as potential reinforcing filler for natural rubber compounds

This work describes the development of a low-density, renewable, and high reinforcing filler for natural rubber (NR) compounds. The cellulose nanocrystal (CNC)-based hybrid filler was synthesized by decorating the surface of CNCs with silica using a simple and efficient coprecipitation method. The properties of the prepared hybrid were investigated by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen physisorption measurements, and Thermogravimetric analysis. Then, the prepared hybrid was incorporated in NR using two different approaches, namely, dry mixing and coprecipitation. The dynamic and tensile mechanical properties of the hybrid/NR compounds were evaluated indicating that: the coprecipitation method was found much more effective for homogeneous dispersion and the CNC/silica hybrid provided quite higher reinforcement to NR than reference silica; however, much lower density of the final compounds was obtained. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48332.