Epoxidized Natural Rubber Latex Research Articles

Enhanced Performance of Epoxidized Natural Rubber Nanocomposites for Strain Sensor Application

In this study, the major objective was to investigate the mechanical and electrical properties, and strain sensibility of the carbon nanotube (CNT) filled epoxidized natural rubber (ENR) nanocomposite. The second filler, cellulose nanofibers (CNFs), at various proportions was incorporated into the CNT-filled ENR nanocomposites. The preparation of ENR nanocomposite was carried out using a latex mixing process. The CNT:CNF hybrid filler was pre-dispersed in deionized water before being added to the ENR latex. The ratios of CNTs to CNFs varied from 1:0 to 1:0.05, 1:0.5, 1:1, 1:1.25, and 1:1.5. Although the presence of CNFs enhanced the stiffness of the substance, its negative effect on the tensile strength was noted. From the evaluated electrical properties, the outcomes demonstrated that the presence of CNFs with suitable proportions can have a positive effect on the performance of the substance when used as a stain-sensitive substance. The electrical conductivity of the hybrid ENR nanocomposite initially increased with the increase of CNF proportion up to 0.5. Beyond this proportion, the conductivity declined gradually. Moreover, the CNT:CNF1:0.5 filled ENR nanocomposite had the highest recoverable piezoresistive property. From this finding, it can be inferred that the CNT:CNF1:0.5 filled ENR nanocomposite is suitable to be used as a strain sensor device.

Effect of Diethylenetriamine on Mechanical and Electrical Properties of Epoxidized Natural Rubber Thin Films

A novel thin film material was fabricated from epoxidized natural rubber latex (ENRL) and chemicals for rubber. The effects of different diethylenetriamine (DETA) contents filled composition on ENRL compounds were investigated on mechanical properties, such tensile strength, water absorption dielectric properties and morphology analysis. The method ENRL thin films were prepared by using solution casting technique and diethylenetriamine as a hardener. The optimal diethylenetriamine content was found to be 6 phr which demonstrated the highest tensile strength due to crosslinking between the epoxy molecules and the water absorption of thin film of increased with the increase of diethylenetriamine content due to the highly porous and hydroxyl groups in the structure. Furthermore, dielectric properties increased with the diethylenetriamine content, it is shown that the conductivity of DETA without supporting electrolyte was very low. The phase morphology of homogeneous compatibility in ENRL phase can be regulated by the crosslinking degree of ENRL and DETA.

Three‐dimensional hierarchical nanostructured porous epoxidized natural rubber latex/poly(vinyl alcohol) material for oil/water separation

AbstractIn the past few decades, many interesting biomaterials with unforeseen properties have attracted considerable attention due to its unique micro‐nano structure. In this work, a bio‐inspired design was proposed to develop the epoxidized natural rubber latex (ENRL)@polyvinyl alcohol (PVA) three‐dimensional (3D) porous material. Herein, the obtained epoxidized natural rubber/polyvinyl alcohol (ENR@PVA) exhibits a “grapevine‐grape” like networks with robust PVA as “grapevine” and soft latex particles as “grape”. Owing to the synergistic effect of those hierarchical micro‐nano structures and abundant hydrophilic oxygen‐containing groups, the ENR@PVA exhibits superhydrophilic and underwater superoleophobic functionality. Accordingly, benefiting from the superwettability features, the ENR@PVA shows superior separation (oil rejections are all above 99.5%) and anti‐fouling performances. More importantly, the integration of excellent flexibility and mechanical robustness guarantees a superior mechanical stability for sustainable reusability and oil recovery in the practical applications. Therefore, the research findings might promote the development of the 3D porous material and its future application for high performance oily wastewater remediation.

Enhanced interfacial interaction between modified cellulose nanocrystals and epoxidized natural rubber via ultraviolet irradiation

This study aims at evaluating the reinforcement of cellulose nanocrystals (CNCs) in epoxidized natural rubber (ENR). Both CNCs and maleic anhydride-modified CNCs (M-CNCs) were prepared from Napier grass stems and characterized by various techniques (e.g., TEM, FTIR, TGA, etc.). They were incorporated into ENR latex at various loadings prior to casting, and then curing by ultraviolet (UV) irradiation. Mechanical properties of the ENR vulcanizates were finally investigated. Results revealed that the prepared CNCs had an average diameter and length of 5 nm and 428 nm, respectively. After modification, M-CNCs contained double bonds in maleate units, which could react with ENR to form covalent bonds under UV irradiation through a proposed mechanism. Regardless of the filler type, mechanical properties including hardness, modulus, and tensile strength, increased considerably with increasing filler loading. At the same filler loading, M-CNCs exhibited greater reinforcement than CNCs due to the enhanced rubber–filler interaction.

PREPARATION AND CHARACTERIZATION OF SPECIALTY NATURAL RUBBER LATEX CONCENTRATE

ABSTRACT Conventionally, specialty natural rubber (SpNR) latex, namely, deproteinized natural rubber (DPNR) latex and epoxidized natural rubber (ENR) latex, are prepared from low ammonia latex (LATZ) causing high material cost. To address this issue, the objective of this study is to prepare SpNR latex directly from freshly tapped NR latex. In this work, DPNR latex is prepared via a heat enzymatic hydrolysis process, while ENR latex is prepared via in situ epoxidation chemical modification process. In addition, both DPNR and ENR latex were concentrated to 60% total solid content via ultrafiltration process using membrane separation technology. Physiochemical properties of DPNR, ENR, and LATZ latex were compared. Results show that the total solid content, dry rubber content, and alkalinity level of the latexes achieved the targeted value. This study also found that nitrogen content of DPNR latex, LATZ latex, and ENR latex were at 0.11%, 0.29%, and 0.25%, respectively, indicating successful deproteinization of the DPNR latex. On the other hand, the epoxidation level of ENR latex produced in this study was at 46.3%, which is slightly lower than the targeted level of 50%. Rheological studies found that ENR latex exhibits the highest viscosity, followed by DPNR and LATZ, but all show characteristic shear-thinning behavior. This study also found that LATZ and DPNR latex are more liquid-like in nature, while ENR latex behaves more like an elastic solid. Non-ionic surfactants play a major role in influencing flow and deformation behavior of the ENR and DPNR latex.

SPECIALTY NATURAL RUBBER LATEX FOAM: FOAMABILITY STUDY AND FABRICATION PROCESS

ABSTRACT Specialty natural rubber (SpNR) latex, namely, deproteinized natural rubber (DPNR) latex and epoxidized natural rubber (ENR) latex, has been produced to meet specific product's requirements. However, SpNR is normally used in the form of block rubber to manufacture dry rubber products such as tires and automotive parts. The applications of SpNR latex into latex foam products will be diversified. Findings indicate that foamability of SpNR latex is lower compared to normal latex (LATZ) but shows longer stability time after foamed. Findings also indicate that foam collapse and foam coagulate are two main challenges in the fabrication process of SpNR latex foam. Despite these challenges, SpNR latex foam can be fabricated at different density levels. During the foaming process, additional foaming agent is required to fabricate a SpNR latex foam, which is different from fabricating a normal NR latex foam, especially at low latex foam density. Consequently, a higher level of sodium silicofluoride, used as the gelling agent, is required to set the cell structure of the foam. Findings also indicate that foam density influenced the gelling time and volume shrinkage of the SpNR latex foam. An ideal compounding, foaming, and gelling formulation to fabricate SpNR latex foam via Dunlop batch foaming process has been developed. Morphological study showed that all latex foams are open-cell structure, with lower density foam exhibiting higher porosity and mean pore size. Comparison on hysteresis behavior between DPNR and ENR latex foam indicated that ENR latex foam exhibits higher hysteresis loss ratio compared to DPNR latex foam.

Flexible, stretchable and magnetic Fe3O4@Ti3C2Tx/elastomer with supramolecular interfacial crosslinking for enhancing mechanical and electromagnetic interference shielding performance

Electromagnetic interference (EMI) and radiation of electronic devices are ubiquitous, which are potentially hazardous to the normal operation of electronic equipment and human health. MXenes are extremely attractive in the preparation of EMI shielding materials due to their excellent metallic conductivity and tunable surface chemistry. Herein, by virtue of the designed nanostructure and regulation of interface interactions, we fabricated flexible Fe3O4@Ti3C2Tx MXene/3,4-dihydroxyphenylacetic acid (DOPAC)-epoxidized natural rubber (ENR) elastomers (FMDE) with 3D segregated interconnected structures. The elaborately designed metal-ligand coordination crosslinking between Fe3O4 nanoparticles and DOPAC ligand molecules provides strong interfacial interactions, resulting in significantly reinforced mechanical properties. Compared with Ti3C2Tx/ENR elastomers, the maximum tensile strength and toughness of FMDE are elevadted by ~306% and 475%, respectively. Moreover, the 3D segregated conductive network constructed by Fe3O4@Ti3C2Tx nanoflakes resulted from volume exclusion effect of ENR latex and the introduction of magnetic Fe3O4 nanoparticles with enhanced electromagnetic wave absorption greatly improved the EMI shielding performance of FMDE, exhibiting an excellent EMI shielding effectiveness of up to 58 dB in the X band (8.2–12.4 GHz) and stable EMI shielding capability during repeated deformations. This work provides a promising strategy for the design and manufacture of novel flexible EMI shielding materials.

Epoxidised natural rubber (ENR) latex: an alternative raw material for latex dipped products

The utilisation of epoxidised natural rubber (ENR) for latex products is limited due to the inability of the ENR latex to form film through typical coagulant dipping processes. This is due to the low total solid content (TSC) and the presence of the non-ionic surfactant in the ENR latex. To use the ENR latex for dipping applications, concentration process via membrane technology is used to reduce the surfactant level in the latex and increase the TSC of the ENR latex material. The current study focuses on two grades: 25% and 50% epoxidation levels of concentrated ENR latex as starting materials and the typical latex compounding behaviour, such as pH, zeta potential, particle size and viscosity, was also analysed to understand its characteristic. Results, such as pH, zeta potential, and particle size, were acceptable and suitable to be used for dipping purpose and it passed the general latex properties of compounding. The cure measurement, such as chloroform number and total swelling index, showed ENR latex is fully vulcanised after 2 days of maturation. On the aspect of physical characteristics of the ENR 25 and 50 films, it resulted with high tensile strength (23.7 MPa) and met the specification of Standard Malaysian glove (SMG). The ability for dipping was satisfactory as smooth continuous film was formed. Aside from that, oil-resistance test and contact angle were also analysed to understand its resistance to oil upon time and wettability parameter of the ENR films.

Strengthened, Self-Healing, and Conductive ENR-Based Composites Based on Multiple Hydrogen Bonding Interactions

Endowing conductive composites with good self-healing properties is of great significance for improving the stability and extending the service life of the material. However, it is still a challenge to prepare conductive composites that exhibit both desirable mechanical strength and excellent self-healing properties. Herein, we report a simple method to fabricate a kind of material with excellent self-healing properties and satisfactory mechanical strength and conductivity performance. Nanochitin (CNC), carboxymethyl chitosan (CMCS), and carbon nanotubes (CNTs) were used as reinforcing fillers and filled into epoxidized natural rubber (ENR) through latex mixing. In particular, CNCs, CMCS, and CNT fillers were selectively dispersed among ENR latex particles. A filler frame network structure based on multiple hydrogen bonding interactions was constructed in the rubber matrix, which significantly improved the mechanical and electrical properties of the composites. Furthermore, the formation of multiple hydrogen bonds in the composites endowed the rubber with excellent self-healing properties, achieving the highest healing efficiency of 91%. This work provides a novel and simple strategy to prepare conductive composites with excellent mechanical and self-healing properties.

Strengthened, Recyclable, Weldable, and Conducting-Controllable Biobased Rubber Film with a Continuous Water-Soluble Framework Network

At present, achieving recycling of rubbers is the main method for their sustainable development. However, it is a challenge to recycle rubbers without retained pristine reinforcing-fillers. Herein, we report fully bio-based rubber films prepared by mixing epoxidized natural rubber (ENR) latex and carboxymethyl chitosan (CMCS) solution. CMCS was regenerated and selectively located in the interstitial space between the ENR latex particles during film-forming process, forming a CMCS framework network in the films. The special CMCS network with hydrogen bonding interactions with ENR endowed rubber films with improved mechanical properties. At the same time, the self-sticky characteristic of ENR with the assistance of chain diffusion and reversible hydrogen bonding interactions made the cut films to be welded. Because the water-soluble CMCS is a continuous phase, the ENR could be perfect recycled by soaking films in water to remove the CMCS. Furthermore, the CMCS framework running through the whole films, whic...

Colloidal properties of epoxidized natural rubber latex prepared via membrane separation technology

To date, epoxidized natural rubber (ENR) latex is still far from being commercially available for the production of dipped latex goods although the process was reported in 1922. Therefore, the objective of this work is to establish an understanding on the colloidal properties of ENR latex and relate them to coagulation and film formation. To do so, ENR latex was first prepared from low ammonia preserved natural rubber (LATZ) latex and then concentrated (C-ENR) using a patented process via membrane separation technology. NMR was used to determine the epoxidation level and ring opening in the ENR latex. The LATZ latex and both epoxidized latexes (ENR and C-ENR) were characterized for their particle size distribution, morphology, zeta potential and rheological properties. NMR analysis revealed an epoxidation level of 26% with < 2% ring opening. Particle size analysis showed C-ENR latex to have a narrow size distribution with no flocculation upon sonication. Zeta potential analysis as a function of pH showed a lower isoelectric point for C-ENR latex compared to LATZ latex. Zeta potential was also low for C-ENR latex compared to LATZ latex above pH 5 indicating an outward shift in the shear plane of the latex particle due to adsorption of the nonionic surfactant. Rheology of the latexes was studied using steady-state and oscillatory measurements. Elastic overshoot was observed for C-ENR latex at volume fraction (ϕ) of 0.490–0.584 indicating strong particle–particle interaction. The calculated maximum packing fraction (ϕp) of C-ENR latex was 0.721 compared to the ϕp of 0.815 for LATZ latex. The lower ϕp was attributed to the adsorbed nonionic surfactant layer on C-ENR latex particles. Oscillatory measurements showed that C-ENR latex behaved as dominantly elastic material from ϕ of 0.4975–0.584. At ϕ of 0.497 (= 48.5 wt%), the adsorbed polymer layers start to interact with each other. At this ϕ, the calculated adsorbed nonionic surfactant layer thickness (Δ) was 35 nm. As the latex concentration was increased, the latex became more elastic due to the interpenetration and compression of the surfactant layers. At the highest latex ϕ of 0.584 (= 57.6 wt%), tan δ was 0.3 resulting in an Δ of 20 nm. This thick layer of adsorbed surfactant hinders the coagulation of particles by salt during dipping thereby prohibiting the film formation process required to make the latex dipped products.

Preparation of Water-suspensible Carbon Nanoparticles and Their Influence on the Properties of Epoxidized Natural Rubber Latex

ABSTRACTA new kind of water-suspensible carbon nanoparticle was prepared by oxidizing carbon black (CB) using aqueous ammonium persulfate (APS) as an oxidant. The obtained water-suspensible carbon nanoparticles (APS-CBs) were still homogeneously distributed in water three weeks after sonication. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the changes of the oxygen containing functional groups on the surfaces of the APS-CBs. Furthermore, a high performance of an epoxidized natural rubber latex (ENRL)/APS-CBs composite was obtained by a liquid latex blending method. The carbon nanoparticles were homogeneously distributed in the matrix. In comparison with the ENRL/pristine CBs composites, the APS-CBs improved the mechanical properties of the ENRL/APS-CBs composites. The dynamic rheological properties were also studied.

Synthesis and properties of a novel epoxidised natural rubber-g-cassava starch polymer and its use as an impact strengthening agent

The polarity of epoxidised natural rubber (ENR) was improved by grafting it with cassava starch (CSt). A graft copolymer between ENR and CSt (ENR-g-CSt) was synthesised from CSt solution and ENR latex by using K2S2O8 as an initiator. The highest percentage efficiency of grafting was obtained with 10 parts per hundred (phr) CSt. The swelling ratio of the ENR-g-CSt particles also decreased as a function of the CSt in the sample due to the polarity of the incorporated CSt. After synthesis, it was used as an impact strengthening agent for a polymer blend. Chemically modified NR polymers can form the basis of many value-added NR products that are environmentally friendly and cost effective for use as biopolymers in the future.

“Green synthesis” and characterization of a maleated epoxidized natural rubber latex

The objective of this present work was to prepare the epoxidized natural rubber (ENR)-g-maleic anhydride (MA) (ENR-g-MA) polymer, from ENR latex using K2S2O8 as an initiator. The chemical structure of the ENR-g-MA was confirmed by FTIR. The evidence for formation of a graft copolymer was found at 1,790 cm−1 owing to the chemical reaction between the ENR and the MA carbon atom. With an increase in the MA content, the particle size and zeta potential of the maleated ENR particle increased due to the change in the chemical composition on the surface of the ENR particles. The swelling ratio decreased with an increase of the MA content due to both the crosslinking and the hydrophilic group from the grafting between the ENR and MA. However, the percentage grafting decreased with an increase of the MA content. This was due to the many side reactions such as chain scission and chain transfer reactions.

Reinforcement of NR with ENR Modified RHA

The rice husk ash (RHA) was first modified with epoxidized natural rubber latex (ENRL) and then blended with natural rubber latex (NRL) to prepare NR/RHA composite. The morphological structure, thermal stability and dynamic properties were studied with multiple instruments. FTIR and TGA analysis showed that ENR was grafted onto the surface of RHA. The composite prepared with modified RHA showed better dispersity and reinforcement compared to the composite with unmodified RHA, and the glass-transition temperature tended to be higher.

Surface Modification of Silica Nanoparticles for Reinforcement of Epoxidized Natural Rubber

Epoxidized natural rubber (ENR) based nanocomposites were prepared by mixing ENR latex (epoxide content of 35 mole%) with silica nanoparticles (SiO2). SiO2 were previously treated with 3-aminopropyltriethoxysilane (APS) and 3-methacryloxypropyltrimethoxysilane (MPS). Morphological and mechanical properties of ENR/SiO2 composites were investigated. The dispersion of SiO2 in ENR matrix, which was characterized by SEM, indicated that the treated SiO2 exhibited better dispersion than that of the untreated SiO2. Moreover, it has been found that the modified SiO2 with either APS or MPS gave much significant reinforcing effect than the untreated one. However, the treatment of SiO2 nanoparticles with MPS resulted in better interfacial interaction when the APS treatment was compared.

Modification of epoxidised natural rubber film surface by polymerisation of methyl methacrylate

Epoxidised natural rubber (ENR) latex, having 25% of epoxide content, was prepared by in situ epoxidation reaction using performic acid. The ENR latex film surface was modified by immersing into methyl methacrylate (MMA) emulsion and then alkaline aqueous solution of ferrous ion/fructose for redox-initiated polymerisation. Increasing polymerisation time caused an increase in percent conversion of MMA swelled in ENR sheet. The presence of poly(methyl methacrylate) on the ENR surface was examined by attenuated total reflection-Fourier transform infrared spectroscopy. The nano-scale indentation experiment performed on the cross-section of the modified ENR sheet indicated that MMA polymerisation occurred mainly near the rubber’s surface. The surface morphology observed under scanning electron microscopy and atomic force microscopy revealed a pronounced roughness which, consequently, decreased the friction coefficient of ENR surface.

Epoxidized natural rubber‐bonded para rubber wood particleboard

AbstractPara rubber wood particleboard (PB) was prepared using NR based adhesives and hot pressing processes. Two types of NR based adhesives were used; epoxidized natural rubber (ENR) and unmodified NR. The ENR latex was prepared using in situ performic epoxidation. Molecular weight of the ENR molecules was then reduced by incorporating of a reducing agent; sodium nitrite solution. A chain scission reaction and epoxidation simultaneous occurred via a chain‐scission parallel epoxidation mechanism. Sulphur and multifunctional amine (i.e., hexamethoxymethylmelamine) curing systems were used to cure the adhesives. It was found that the hexamethoxymethylmelamine gave the PB with higher tensile strength than that of the sulphur vulcanization system. Furthermore, the tensile strength increased with increasing concentration of citric acid in the compounding formulation. Adhesion of the ENR adhesive with Parawood sawdust was observed to imporve by reducing molecular weight of the ENR molecules. That is, the highest tensile strength of the PB was observed for the ENR adhesive with the lowest $ {\overline {M}_{n}} $ (i.e., 1.10 × 105). This may be attributed to the adhesive with lower molecular weight exhibited greater ability to wet or cover the wood particle surfaces. As a consequence, greater chemical interaction between the adhesive and the wood particles was observed. POLYM. ENG. SCI., 47:421–428, 2007. © 2007 Society of Plastics Engineers.

Latex interpenetrating polymer networks of epoxidised natural rubber/poly(methyl methacrylate): an insight into the mechanism of epoxidation

Composite latex particles consisting of epoxidised natural rubber (ENR) and poly(methyl methacrylate) (PMMA) were synthesised to obtain interpenetrating polymer networks. Among the ENR latices having 9 to 36 mol% epoxide, prepared by in situ reaction using performic acid, the ENR latex with 25 mol% epoxide was selected for prevulcanisation by sulphur or γ-radiation system. The swelling ratios of sheets cast from the sulphur-prevulcanised ENR (SPENR) latices decreased with increasing prevulcanisation time while those cast from the γ-radiation-prevulcanised ENR latices were also inversely proportional to the irradiation dose. By applying the phase transfer/bulk polymerisation/transmission electron microscopy (TEM) technique, a homogeneous network structure in each of the SPENR particles and also a relative dense network near the surface in γ-radiation (RV) ENR particle were noticed. When 10 to 30 wt% of MMA swollen in ENR particles was polymerised, the mesh structure was observed in each particle. The dense network near the RVENR particle surface might be used as additional evidence that the degree of epoxidation and, hence, the presence of swollen n-butyl acrylate in the outer zone were higher than in the internal region.

Composite natural rubber based latex particles: a novel approach

The oil resistance of natural rubber (NR) film could be effectively improved by using the heterocoagulation of large NR particle with small polychloroprene (CR) particles. In the preparation of NR/CR composite particle with a core-shell structure, a nonionic surfactant whose molecule bears poly(ethylene oxide) (PEO) was adsorbed on CR particles and allowed to form complexes between PEO and indigenous surfactant (protein–lipid) on the NR particle surface. Composite latex particle obtained was characterised by particle size, zeta potential and glass transition temperature measurements and the data indicated the presence of CR on the outer layer of composite particle. Better oil resistance of film casted from heterocoagulated latex when compared to that of NR film confirmed the NR/CR core-shell structure. The epoxidised natural rubber (ENR), crosslinked ENR and/or skim latex particles were investigated in order to replace the use of CR in the heterocoagulation process.