Synthesis and Application of Epoxidized Natural Rubber

Abstract

North Vietnamese NR latexes were successfully epoxidized using peracetic acid at moderate temperature and pH range. The epoxide contents of pure epoxidized natural rubber (ENR) are from 5 to 70 mol%. The ENR products were characterized and determined by spectral and thermal analysis besides the chemical titration. Conditions of longlasting or excessive temperature, or high acidic pH led to side ring opened products, proved easily by IR, ¹H-NMR, and DSC analysis. The ENR were vulcanized using a semiefficient system. The epoxidation increased the adhesion between rubber and tire cord and metal. This effect becomes stronger beyond 25 mol% and tends to be limited at over 60 mol%. The ENRs were used to formulate special-purpose adhesives. The shear strength of the adhesive ranges from 32 to 45 kg/cm² for bonding rubber to nylon and rubber to metal, respectively.     

Effects of epoxidized natural rubber as a compatibilizer in melt compounded natural rubber-organoclay nanocomposites

Nanocomposites containing natural rubber (NR) as matrix, epoxidized natural rubber (ENR) as compatibilizer and organophilic layered clay (organoclay) as filler were produced in an internal mixer and cured using a conventional sulphuric system. The effects of ENR with 25 (ENR 25) and 50 mol% epoxidation (ENR 50), respectively, were compared at 5 and 10 parts per hundred rubber (phr) concentrations. The organoclay content was fixed at 2 phr. Cure characteristics, clay dispersion, (thermo)mechanical properties of the nanocomposites were determined and discussed. Incorporation of ENR and organoclay strongly affected the parameters which could be derived from Monsanto MDR measurements. Faster cure and increased crosslink density were attributed to changes in the activation/crosslinking pathway which was, however, not studied in detail. The organoclay was mostly intercalated according to X-ray diffraction (XRD) and transmission electron microscopic (TEM) results. The best clay dispersion was achieved by adding ENR 50. This was reflected in the stiffness of the nanocomposites derived from both dynamic mechanical thermal analysis (DMTA) and tensile tests. The tensile and tear strengths of the ENR 50 containing nanocomposites were also superior to the ENR 25 compatibilized and uncompatibilized stocks.     

Influence type of natural rubber on properties of green biodegradable thermoplastic natural rubber based on poly(butylene succinate)

Green biodegradable thermoplastic natural rubber (GB‐TPNR) based on simple blend of natural rubber (NR) and poly(butylene succinate) (PBS) was prepared using three NR alternatives: unmodified NR and epoxidized NR with 25‐ or 50‐mol% epoxide (ie, ENR‐25 or ENR‐50). It was found that ENR‐50/PBS blend showed the best compatibility, which resulted in superior mechanical and thermal properties with the highest crystallinity of the PBS phase, on comparing with the ENR‐25/PBS and NR/PBS blends. This might be attributed to stronger chemical interactions between the epoxide groups in ENR‐50 and the polar functional groups in PBS, which were confirmed by Fourier transform infrared (FTIR). Furthermore, scanning electron microscopy (SEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM) micrographs of ENR‐50/PBS blend revealed phase separation with finer‐grained cocontinuous structure than in ENR‐25/PBS and NR/PBS simple blends. Furthermore, the chemical interactions in ENR‐50/PBS blend enhanced the resistance to accelerated weathering.     

Effect of epoxidation of natural rubber on the pervaporation separation of acetone–chlorinated hydrocarbon mixtures

The pervaporation separation and the swelling behavior of chlorinated hydrocarbon/acetone mixtures were investigated using natural rubber (NR) and epoxidized natural rubber (ENR) membrane with 25 and 50 mol% epoxidation, respectively. The swelling degree increases with increase in the epoxidation level. The flux and separation factor of the membranes were determined both as a function of mole percent epoxidation and of the feed mixture composition. The membranes were found to be permselective to chlorinated hydrocarbons from acetone–chlorinated hydrocarbon mixtures. The flux decreases with increase in epoxidation level, whereas the separation factor increases. The permeation decreases and separation factor increases with increase in the acetone feed concentration. The availability of raw materials, low cost of implementation and easy processability of the system makes this method of separation highly applicable and recommendable.     

High-performance natural rubber nanocomposites with marine biomass (tunicate cellulose)

Due to the importance in economic and environmental benefits, marine biomass has gained increasing attention in recent years. In this work, marine biomass-based materials were prepared and characterized. Highly reinforcing cellulose nanocrystals (CNCs) with length of 1–2 μm and aspect ratio of ~75 were extracted from tunicates (t-CNCs), and CNCs with length of 100–300 nm and aspect ratio of ~15 from cotton (c-CNCs) were presented for comparison. In order to enhance interfacial interactions between CNCs and rubber, modification of natural rubber (NR) was conducted via epoxidation reaction to obtain epoxidized NR (ENR). Fully bio-based rubber nanocomposites were produced by latex mixing. Compared with NR nanocomposites, hydrogen bonding formed between ENR and CNCs, which led to homogeneous dispersion of CNCs and enhanced interfacial adhesion between them. Moreover, t-CNCs with longer length and larger aspect ratio facilitate filler entanglements, which led to higher reinforcing efficiency. Consequently, both hydrogen bonding and filler entanglements contributed to the improved mechanical properties of ENR/t-CNCs nanocomposites.     

Styrene butadiene rubber/epoxidized natural rubber blends: dynamic properties, curing characteristics and swelling studies

The dynamic properties, curing characteristics and swelling behaviour of styrene butadiene rubber (SBR) and epoxidized natural rubber (ENR) blends were studied. The incorporation of ENR 50 in the blends improved processability, stiffness, resilience and reduced the damping property. In terms of curing characteristics, the scorch time, t₂ and curing time, t₉₀ of the SBR/ENR blends decrease with increasing ENR content. At room temperature (23°C) and at 100°C the swelling degree of the SBR/ENR blends decreases with increasing ENR content.     

Reinforcement of compatibilized NR/NBR blends by fly ash particles and precipitated silica

Effects of precipitated silica (PSi) and silica from fly ash (FA) particles (FASi) on the cure and mechanical properties before and after thermal and oil aging of natural rubber (NR) and acrylonitrile–butadiene rubber (NBR) blends with and without chloroprene rubber (CR) or epoxidized NR (ENR) as a compatibilizer have been reported in this paper. The experimental results suggested that the scorch and cure times decreased with the addition of silica and the compound viscosity increased on increasing the silica content. The mechanical properties for PSi filled NR/NBR vulcanizates were greater than those for FASi filled NR/NBR vulcanizates in all cases. The PSi could be used for reinforcing the NR/NBR vulcanizates while the silica from FA was regarded as a semi‐reinforcing and/or extending filler. The incorporation of CR or ENR enhanced the mechanical properties of the NR/NBR vulcanizates, the ENR being more effective and compatible with the blend. The mechanical properties of the NR/NBR vulcanizates were improved by post‐curing effect from thermal aging but deteriorated by the oil aging. Copyright © 2008 John Wiley & Sons, Ltd.     

Properties of Natural Rubber/Recycled Chloroprene Rubber Blend: Effects of Blend Ratio and Matrix

The present study investigated the effects of two types of natural rubber and different blend ratios on the cure, tensile properties and morphology of natural rubber/recycled chloroprene rubber blends. The blends of natural rubber/recycled chloroprene rubber were prepared by using laboratory two-roll mill. The result showed that the cure time prolonged with the addition of recycled chloroprene rubber (rCR). Comparability, natural rubber/recycled chloroprene rubber (SMR L/rCR) blendcured rapidly than epoxidized natural rubber/recycled chloroprene rubber (ENR 50/rCR) blend. The addition of rCRalso caused a decrement in the tensile strength and elongation at break for both rubber blends. The SMR L/rCR blendsshowed higher tensile strength and elongation at break compared to those of ENR 50/rCR blends at any blend ratios.     

Depolymerization and ionic conductivity of enzymatically deproteinized natural rubber having epoxy group

Preparation of liquid epoxidized natural rubber (ENR) was made by oxidative depolymerization of ENR in latex stage without loss of epoxy group. Epoxidation of fresh natural rubber latex, which was purified by deproteinization with proteolytic enzyme and surfactant, was carried out with freshly prepared peracetic acid. The glass transition temperature (T_g) and gel content of the rubbers increased after the epoxidation, both of which were dependent upon an amount of peracetic acid. The gel content was significantly reduced by oxidative depolymerization of the rubber with (NH₄)₂S₂O₈ in the presence of propanal. The resulting liquid epoxidized rubber (M_n≈10⁴) was found to have well-defined terminal groups, i.e. aldehyde groups and α-β unsaturated carbonyl groups. The novel rubber was applied to transport Li⁺ as an ionic conducting medium, that is, solid polymer electrolyte.     

Hydrogenation of natural rubber having epoxy group

Hydrogenation of epoxidized natural rubber (ENR) was performed to introduce hydroxyl group to hydrogenated natural rubber. The ENR was prepared by epoxidation of deproteinized natural rubber (DPNR) with peracetic acid in latex stage. Hydrogenation of epoxidized DPNR (EDPNR) was performed with p-toluenesulfonylhydrazide in p-xylene. The resulting product, hydrogenated EDPNR (HEDPNR), was characterized by nuclear magnetic resonance spectroscopy with various pulse sequences, i.e., two-dimensional correlation spectroscopy, two-dimensional heteronuclear correlation measurements. Carbons linking up to hydroxyl group were assigned to be quaternary and tertiary groups. The HEDPNR was proved to be a polyolefine elastomer through differential scanning calorimetry.     

Morphology and fracture behavior of toughening‐modified poly(vinyl chloride)/organophilic montmorillonite composites

Toughening‐modified poly(vinyl chloride) (PVC)/organophilic montmorillonite (OMMT) composites with an impact‐modifier resin (Blendex 338) were prepared by melt intercalation, and their microstructures were investigated with wide‐angle X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. The mechanical properties of the PVC composites were examined in terms of the content of Blendex and OMMT, and the fracture toughness was analyzed with a modified essential work of fracture model. Intercalated structures were found in the PVC/OMMT composites with or without Blendex. Either Blendex or OMMT could improve the elongation at break and notched impact strength of PVC at proper contents. With the addition of 30 phr or more of Blendex, supertough behavior was observed for PVC/Blendex blends, and their notched impact strength was increased more than 3319% compared with that of pristine PVC. Furthermore, the addition of OMMT greatly improved both the toughness and strength of PVC/Blendex blends, and the toughening effect of OMMT on PVC/Blendex blends was much larger than that on pristine PVC. Blendex and OMMT synergistically improved the mechanical properties of PVC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 286–295, 2004     

Property correlations for dynamically cured rice husk ash filled epoxidized natural rubber/thermoplastic polyurethane blends: Influences of RHA loading

Novel thermoplastic vulcanizates based on thermoplastic polyurethane (TPU) and epoxidized natural rubber (ENR) were prepared with rice husk ash (RHA) filler. Therefore, two major renewable resource materials (i.e., ENR and RHA) were exploited. Influences of RHA loading on mechanical, morphological, thermal and dynamic properties of dynamically cured ENR/TPU blends were investigated. It was found that the RHA showed good dispersion and was mainly localized in the ENR phase. Increasing the RHA loading led to the formation of larger ENR domains dispersed in the TPU matrix. Also, migration of the RHA particles from ENR to TPU phases was observed, resulting in reduced strength properties. It was found that the RHA acted as a nucleating agent in the TPU matrix and could accelerate the crystallization of TPU. Additionally, stress relaxation of the blends was evaluated by temperature stress scanning relaxation (TSSR). Higher relaxation stresses or raised relaxation curves were observed with increased RHA loadings in the dynamically vulcanized ENR/TPU blends.     

不同结构氧化锌对CIIR/ENR共混胶的气体阻隔性能和力学性能的影响

以重量比为90∶10的氯化丁基橡胶/环氧天然橡胶共混胶为基体,用密炼法将三种不同结构的氧化锌（普通条状氧化锌、片状氧化锌和纳米结构氧化锌）分散到基体中,研究不同结构的氧化锌对共混胶力学性能和气体阻隔性能的影响.结果表明片状氧化锌和纳米氧化锌复合胶比普通氧化锌复合胶强度下降,伸长率提高.片层氧化锌复合体系硫磺用量提高到2.0份,综合力学性能达到最好,且片状氧化锌能够赋予复合胶最佳的气体阻隔性能,比普通氧化锌体系提高了50％.     

Effect of polyvinylchloride on the properties of rubber vulcanizates

Natural rubber (NR) and styrene-butadiene rubber (SBR) were compounded with polyvinylchloride (PVC). Some physico-mechanical and dielectric properties of resulting rubber vulcanizates were measured. It was found that the addition of PVC to both NR and SBR results in slight decreases in tensile strength and elongation at break but a marked increase in oil-resistance of the vulcanizates. Moreover, the addition of PVC to NR slightly increases both dielectric constant and dielectric losses while the addition of PVC to SBR loaded with 50 phr carbon black (HAF) lowers these parameters. Both rubber blends, especially NR, show a reasonable stability with ageing.     

Natural Phenolic Compounds as Modifiers for Epoxidized Natural Rubber/Silica Hybrids

Silica is a popular filler, but in epoxidized natural rubber, can act as a cross-linking agent. Unfortunately, a high amount of silica is necessary to obtain satisfactory tensile strength. Moreover, a high amount of silica in ENR/silica hybrids is associated with low elongation at break. In our paper, we propose natural phenolic compounds, including quercetin, tannic acid, and gallic acid as natural and safe additional crosslinkers dedicated to ENR/silica hybrids to obtain bio-elastomers with improved mechanical properties. Therefore, toxic crosslinkers, such as peroxides or harmful accelerators can be eliminated. The impact of selected natural phenolic compounds on crosslinking effect, mechanical properties, color, and chemical structure of ENR/silica composite have been analyzed. The obtained results indicated that only 3 phr of selected natural phenolic compounds is able to improve crosslinking effect as well as mechanical properties of ENR/silica hybrids. Moreover, some of the prepared materials tend to regain mechanical properties after reprocessing. Such materials containing only natural and safe ingredients have a chance of becoming novel elastomeric biomaterials dedicated to biomedical applications.     

Strikingly improved toughness of nonpolar rubber by incorporating sacrificial network at small fraction

It poses a huge challenge to create nonpolar rubber with high fracture toughness. In the present letter, inspired by the concept of sacrificial bonding associated with many biological materials, we propose that a small fraction of additional sacrificial network can strikingly improve the fracture toughness of nonpolar rubbers. As a proof of concept, we created the additional “fragile” epoxidized natural rubber (ENR) network in commercially available SBR rubber in a facile process. With addition of only 10 phr ENR, the SBR/ENR double network (DN) exhibits a fracture energy nearly fourfold higher than that for the neat SBR. The formation of DN formation and the correlation between the high toughness and presence of the second brittle network have been fully discussed. This is the first time sacrificial networks are created in diene‐based rubber towards high toughness elastomers in a facile and efficient way. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 781–786     

In situ reactive compatibilization of polypropylene/epoxidized natural rubber blends by electron induced reactive processing: novel in‐line mixing technology

Blends of polypropylene (PP) and epoxidized natural rubber (ENR) were prepared by an in‐line electron induced reactive processing technique. The mixing was done in a Brabender mixing chamber coupled with an electron accelerator. The effect of sequence of electron treatment on the compatibilization of non‐polar PP and polar ENR was investigated in the presence of triallyl cyanurate (TAC). Finally, the resulting blends were characterized by different techniques, namely, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile tests, and rheological studies. Generation of phase coupling and chemical compatibilization were observed from FTIR analysis. DMA studies showed enhanced high‐temperature modulus (above the glass transition temperature of both components) followed up by lowering in the tan δ peak. Rheological studies showed increase in modulus at low frequencies. Electron treatment and incorporation of rubber phase into PP showed significant effect on the degree of crystallinity of the blends, which was characterized by DSC study. The results obtained from FTIR, DMA, SEM, rheological studies, and tensile tests strongly affirmed that electron induced reactive processing of PP in presence of TAC before adding of ENR performed the best amongst all samples modified with electrons investigated in this study. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and characterization of acidified chitosan immobilized in epoxidized natural rubber

Biocomposites comprising chitosan (CTS) trapped in an epoxidized natural rubber (ENR) was prepared by homogenizing CTS in ENR50 (ENR with about 50% epoxy content) latex in the presence of curing agents and acetic acid. Micrographs of CTS-t-ENR reveal no phased-out entity. Infrared spectra of CTS-t-ENR show only vibrational bands belonging to CTS and ENR, affirming that the former was not bonded but immobilized in the matrix of the latter. CTS loading up to 5 phr resulted in the increase in the tensile strength and elongation at break, modulus of the CTS-t-ENR. Thermal stability of CTS-t-ENR is higher than that of CTS but lower than that of ENR. Increase in CTS loading from 2.5 to 20 phr resulted in the decrease in toluene absorbency but increase in water uptake of CTS-t-ENR.     

聚合物共混物脆韧转变性能研究 V.橡胶粒子的分布对聚氯乙烯/丁腈橡胶共混物韧性刚性关系的影响

聚合物共混物脆韧转变性能研究Ｖ．橡胶粒子的分布对聚氯乙烯／丁腈橡胶共混物韧性刚性关系的影响刘浙辉朱晓光张学东漆宗能（中国科学院化学研究所工程塑料国家重点实验室北京１０００８０）蔡忠龙（香港理工大学应用物理系香港九龙）王佛松（中国科学院北京...     

Evaluation of air permeability characteristics on the hybridization of carbon black with graphene nanoplatelets in bromobutyl rubber/epoxidized natural rubber composites for inner‐liner applications

Nanotechnology has been explored recently as a means of enhancing the properties of conventional elastomers for engineering applications. In the current study, the effect of nanofillers on air impermeability properties of Brominated isobutylene‐isoprene rubber (BIIR)/Epoxidized natural rubber (ENR) blend has analyzed for automotive applications. The ENR chosen is ENR 25 and ENR 50 (25 and 50% epoxidation) and prepared the blends in a ratio of 75:25 (BIIR:ENR), and from both blend based composites, a part of carbon black replaced with graphene nanoplatelets (GNP). The physical and thermal properties were compared for both binary blend nanocomposites to study the level of exfoliation and reinforcement behavior of GNP. Morphology studies were employed to reveal the level of interaction between GNP and carbon black in both blends. The influence of epoxidation in the formation of nanostructures in both blends have been evaluated, and the effect of nanostructures on air permeability properties was studied. The air impermeability of BIIR‐ENR 50 nanocomposites were improved with increasing platelet concentration, a 30% improvement in air permeability is obtained for BIIR‐ENR 50 composites over BIIR ‐ENR 25.