Radiation-vulcanized Natural Rubber Latex Research Articles

COMPARISON OF TECHNOLOGY OF RADIATION VULCANIZED NATURAL RUBBER LATEX USING UV-MERCURY LAMP, UV-LED LAMP, AND PLASMA CATHODE-BASED EBM IRRADIATORS

The electron beam machine (EBM) irradiators based on plasma cathode that emit pulse electron beam for radiation vulcanized natural rubber latex (RVNRL) have been developed in Tomsk, Russia. Meanwhile, a prototype of an ultraviolet light-emitting diode (UV-LED) irradiator for RVNRL has been developed by the Research Technology Center for Accelerator and the ATK Polytechnic in Yogyakarta, Indonesia. This research aims to compare the irradiator prototype technology for RVNRL. The RVNRL technology comparison method is carried out by assessing the specifications and performance of the equipment, costs (investment, operational, maintenance), hazard, and operability. The results of the comparison of irradiator technology for RVNRL show that the UV-LED irradiators are superior to the UV-mercury irradiators and the plasma cathode-based EBM irradiators which gives a total value of 476, 412, and 248, respectively. Thus, it can be concluded that the UV-LED irradiators technology for RVNRL is simpler, more practical, economical, and environmentally friendly compared to the UV-mercury irradiators and the plasma cathode-based EBM irradiators.

Transport properties of radiation vulcanized natural rubber latex nanocomposites

Radiation vulcanized natural rubber latex (RVNRL) nanocomposites were prepared by the incorporation of aqueous dispersions of nanosilica and nanoclay in RVNRL latex. The sorption, diffusion, and permeation coefficients of the composites were measured at 303 K. The magnitude of the diffusion coefficient showed a decreasing trend in RVNRL/nanosilica composites followed by nanoclay and china clay composites. The diffusion of solvent through rubber followed a first-order kinetics. The transport phenomenon was found to follow an anomalous behaviour. XRD analysis showed that nano silica particles were homogeneously distributed in the rubber matrix. The particle size of the nano silica is 10 nm as confirmed from TEM analysis. RVNRL/nano silica composites showed better dispersion of filler particles in natural rubber.

Roles of Chitosan as Bio-Fillers in Radiation-Vulcanized Natural Rubber Latex and Hybrid Radiation and Peroxide-Vulcanized Natural Rubber Latex: Physical/Mechanical Properties under Thermal Aging and Biodegradability.

Although natural rubber was regarded as biodegradable, the degradation is a time-consuming process that could take weeks or months for any degradation or substantial weight loss to be observable, resulting in the need for novel processes/methods to accelerate the rubber degradation. As a result, this work investigated the potential utilization of chitosan (CS) as a biodegradation enhancer for radiation-vulcanized natural rubber latex (R-VNRL) and hybrid radiation and peroxide-vulcanized natural rubber latex (RP-VNRL) composites, with varying CS contents (0, 2, 4, or 6 phr). The R-VNRL samples were prepared using 15 kGy gamma irradiation, while the RP-VNRL samples were prepared using a combination of 0.1 phr tert-butyl hydroperoxide (t-BHPO) and 10 kGy gamma irradiation. The properties investigated were biodegradability in the soil and the morphological, chemical, mechanical, and physical properties, both before and after undergoing thermal aging. The results indicated that the biodegradability of both the R-VNRL and RP-VNRL composites was enhanced with the addition of CS, as evidenced by increases in the percentage weight loss (% weight loss) after being buried in soil for 8 weeks from 6.5 ± 0.1% and 6.4 ± 0.1% in a pristine R-VNRL and RP-VNRL samples, respectively, to 10.5 ± 0.1% and 10.2 ± 0.1% in 6-pph CS/R-VNRL and 6-pph CS/RP-VNRL composites, respectively, indicating the biodegradation enhancement of approximately 60%. In addition, the results revealed that the addition of CS could increase the value of tensile modulus by 119%, while decrease the values of tensile strength and elongation at break by 50% and 43%, respectively, in the specimens containing 6-phr CS. In terms of the color appearances, the samples were lighter and yellower after the addition of CS, as evidenced by the noticeably increased L* and b* values, based on the CIE L*a*b* color space system. Furthermore, the investigation into the effects of thermal aging showed that the overall tensile properties for both curing systems were reduced, while varying degrees of color change were observed, with the pristine R-VNRL and RP-VNRL samples having more pronounced degradation/changes for both properties. In conclusion, the overall results suggested that CS had great potential to be applied as a bio-filler in R-VNRL and RP-VNRL composites to effectively promote the biodegradability, environmental friendliness, and resistance to thermal degradation of the composites.

Enhancing electromagnetic interference shielding effectiveness for radiation vulcanized natural rubber latex composites containing multiwalled carbon nanotubes and silk textile

AbstractThis work investigated the electromagnetic interference shielding effectiveness (EMI SE), electrical conductivity (σ), and mechanical properties of radiation vulcanized natural rubber latex (RVNRL) with varying amounts of multiwalled carbon nanotube (MWCNT) and silk textiles for use as flexible EMI shielding materials. The results indicated that 14‐kGy gamma irradiation on NRL successfully initiated crosslinking between NR chains. The results also indicated the increases in MWCNT content increased σ, EMI SE, and hardness, but decreased tensile strength and elongation at break of the composites. Furthermore, silk textile inserted in MWCNT/RVNRL composites could further enhance both σ and EMI SE, while maintaining the strength of the materials at higher MWCNT contents, which previously tended to decrease with increasing MWCNTs. Specifically, the maximum EMI SE in this work was obtained by using 6‐phr MWCNT content and the insertion of silk textile in RVNRL composites (~8 [19] dB for a 2‐mm [8‐mm] thickness at 300 MHz).

Low-temperature exfoliated graphene oxide incorporated with different types of natural rubber latex: Electrical and morphological properties and its capacitance performance

A simple with cost-effective method in the production and fabrication of graphene-based rubber nanocomposites as electrode materials is still remain a global challenge. In this work, we proposed one- and two-step approaches to fabricate an exfoliated graphene oxide (GO) as nanofiller in three different types of rubber latex polymer, namely, low ammonia natural rubber latex (NRL), radiation vulcanized NRL (RVNRL), and epoxy NRL 25 (ENRL 25). The electrical conductivity and capacitive behavior of nanocomposite samples were investigated under a four-point probe and cyclic voltammetry measurements, respectively. Meanwhile, the morphological properties were observed using field emission scanning electron microscopy, energy dispersive X-ray, optical polarization microscope, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The thermal stabilities of the nanocomposites were also investigated by thermogravimetric analysis. Among all, the GO/RVNRL polymer nanocomposite samples performed a better homogeneity with an improved electrical conductivity (~8.6 × 10−4 Scm−1) as compared with the GO/ENRL 25 (~3.1 × 10−4 Scm−1) and GO/NRL (~2.6 × 10−4 Scm−1) polymer nanocomposite samples. In addition, the GO/RVNRL polymer nanocomposite electrodes showed acceptable specific capacitance (5 Fg-1). The successfully fabricated conductive GO-based rubber nanocomposites are suitable for new supercapacitor electrodes.

Mechanical and electrical properties of radiation-vulcanized natural rubber latex with waste eggshell powder as bio-fillers

ABSTRACTThis work investigated the mechanical, physical, morphological, and electrical (volume) resistivity properties of radiation-vulcanized natural rubber latex (RVNRL) with additions of waste eggshell (WES) powder, which contained primarily CaCO3 (calcite). The results showed that increasing gamma irradiation doses from 0 to 30 kGy in 10-kGy increments led to decreases in the swelling ratio and elongation at break but increases in the crosslink density, tensile modulus at 500% elongation, and tensile strength of the composites. The results also suggested that increasing the WES contents from 0 to 2, 4, or 6 parts per hundred parts of rubber by weight (phr) in the composites improved the tensile modulus at 500% elongation, tensile strength, hardness (Shore A), and electrical (volume) resistivity. In addition, after undergoing thermal aging at 70°C for 96 h, the tensile modulus and hardness (Shore A) increased, while the tensile strength and elongation at break decreased. This work also compared the properties of WES/RVNRL with commercial CaCO3/RVNRL samples at the same 4-phr content. The results indicated that both composites had similar tensile properties, implying possible replacement of commercial CaCO3 with WES powder as an effective reinforcing filler in RVNRL.

Enhancing mechanical properties of prevulcanized natural rubber latex via hybrid radiation and peroxidation vulcanizations at various irradiation doses

ABSTRACTAt present, there are three popular vulcanization processes being used in natural rubber latex industries, which are sulfur, radiation and peroxide vulcanization. Sulfur vulcanization produced products with superior mechanical properties compared to radiation and peroxide vulcanization. This paper discussed the effect of gamma irradiation dose on hybrid radiation and peroxidation vulcanizations in improving the mechanical properties of radiation vulcanized natural rubber latex (RVNRL). Latex compounding formulations are developed based on 2.5 parts per hundred rubber (phr) of hexanediol diacrylate (HDDA) as the sensitizer, 0.1 phr of tert-butyl hydroperoxide (t-BHPO) as the co-sensitizer and 2.5 phr of Aquanox LP antioxidant. The RVNRL was prepared and irradiated at various gamma radiation doses of 2, 4, 6, 8, 10 and 12 kiloGray (kGy). The rubber film obtained from irradiation at 6 kGy had tensile strength, modulus @ 500% and modulus @ 700% of 27.0, 3.0 and 11.0 MPa, respectively, which is more than 37% increment compared to the control film. Besides, the crosslink percentage of the rubber film showed 4% increment from 90% to 94%.

Electrical enhancement of radiation-vulcanized natural rubber latex added with reduced graphene oxide additives for supercapacitor electrodes

An insulating polymer, radiation vulcanization natural of rubber latex (RVNRL), was successfully converted into electrically conductive nanocomposite by the addition of reduced graphene oxide (rGO) assisted by sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulfonate (TC14) surfactant. The starting material, graphene oxide (GO), was initially synthesized by electrochemical exfoliation assisted by TC14 surfactant. Then, GO/RVNRL nanocomposite was fabricated by latex technology. For rGO/RVNRL nanocomposite, the synthesized GO was further reduced to rGO using hydrazine hydrate and showed electrical enhancement up to 1.32 × 10−3 S cm−1 compared with GO when composited with RVNRL (8.64 × 10−4 S cm−1). For comparison, rGO/RVNRL nanocomposite assisted by the commercially available surfactant sodium dodecyl sulfate was prepared, and its electrical conductivity was found to be 1.79 × 10−5 S cm−1, which was several orders of magnitude lower than those of GO/RVNRL and rGO/RVNRL nanocomposites prepared with TC14 surfactant. C–V measurements taken for TC14-rGO/RVNRL and TC14-GO/RVNRL nanocomposites showed specific capacitances of 95 and 63 F g−1, respectively. The structural properties of nanocomposites were characterized using FESEM, HRTEM, UV–Vis, micro-Raman, XRD, FT-IR spectroscopy, and TGA studies. This study was the first to report on the success of converting the insulator polymer RVNRL into a conductive nanocomposite assisted by TC14 surfactant. The nanocomposite can be a new electrode material for supercapacitor application.

Investigation of polymer degradation by addition of magnesium

ABSTRACTThe effect of alkali metal magnesium on polymer degradation of physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of Mg of different concentrations (0–30 ppm) to natural rubber latex and irradiation with various radiation doses (0–20 kGy). The radiation doses were optimized (12 kGy), and the adverse effect of Mg was studied against a reference film prepared without metal. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films were decreased with increasing metal ion concentrations and decreasing radiation doses. The mechanical properties of the films were reduced by nearly 10% for 30 ppm Mg ions and at the optimum dose. In contrast, elongation at break, permanent set, and swelling ratio of the films were increased at the same conditions. The maximum tensile and tear strengths of irradiated rubber films without additive were 29.33 MPa and 47.95 N/mm, respectively, at a radiation dose of 12 kGy, and these values were about six times higher than those of blank samples. With the addition of Mg, the corresponding values decrease continuously, and the minimum values were found to be 26.35 MPa and 42.675 N/mm, respectively. The effect of divalent alkali metal on polymer chain scission can be explained by the classical electron concept reported in this article.

Effect of Manganese on Radiation Vulcanization of Natural Rubber

Manganese was added as a promoter to investigate physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films. RVNRL films were prepared by the addition of Mn with the concentration range 0–30 ppm to natural rubber latex and irradiated with various radiation doses (0–20 kGy). Tensile strength, tear strength, and cross-linking density of the irradiated rubber films increased with increasing the concentration of Mn ions as well as radiation doses. In contrast, elongation at break, permanent set, and swelling ratio of the films were decreased under the same conditions. The concentration of Mn ions and radiation doses were optimized and found to be 20 ppm and 12 kGy, respectively. The maximum tensile and tear strengths of irradiated rubber films were observed as 29.12 MPa and 44.78 N/mm, respectively at the optimum conditions. The mechanical properties of the films increased markedly with the addition of Mn until they attained the highest values of 33.88 MPa and 54.77 N/mm, respectively. These enhancements, which reached approximately 20% at the most favorable conditions, can be explained by the effect of transition metals in view of Fajan’s rules regarding the covalent character of ionic bonds and suggest that the higher the difference in charges between cation and anion, the higher the ability to form distortion or polarization of ions.

Role of Divalent Metals in Polymer Degradation

The role of divalent metals in the degradation of the physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of metals (Cu, Mg, etc.) of different concentrations (0–30ppm) to natural rubber latex and irradiated with various radiation doses (0–20kGy). The radiation doses were optimized (12kGy), and the adverse effect of metal ions was studied against a reference film prepared with no metal ions. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films decreased with increasing metal ion concentrations and decreasing radiation doses. The mechanical properties of the films were reduced by 10–15% for 30ppm metal ions and at the optimum dose. In contrast, elongation at break, permanent set, and swelling ratio of the films increased at the same conditions. The relative effect of metal ions can be explained by the classical electron concept, reported in this article.

Addition of Transition Metals to Improve Physico-Mechanical Properties of Radiation-Vulcanized Natural Rubber Latex Films

The effect of transition metals as a promoter of physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of transition metals (Fe, Mn, etc.) of different concentrations (0–30 ppm) in natural rubber (NR) latex and irradiated with various radiation doses (0–20 kGy). The concentrations of metal ions and radiation doses were optimized and found to be 20 ppm and 12 kGy, respectively. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films were increased with increasing concentration of metal ions as well as radiation doses. The mechanical properties of the films were enhanced by approximately 20% at the optimum conditions. In contrast, elongation at break, permanent set, and swelling ratio of the films were decreased under the same conditions. The comparative effect of metal ions can be explained by Fajan's rules, reported in this article.

Studies on radiation grafting of methyl methacrylate onto natural rubber for improving modulus of latex film

Methyl methacrylate (MMA) can be grafted onto natural rubber (NR) in latex by gamma irradiation for improving the mechanical properties of the dry films. Physical blending of MMA-grafted NR latex with radiation vulcanized natural rubber latex (RVNRL) or simultaneous radiation grafting and crosslinking are found to be useful techniques for improving the properties of latex films. Moduli of the films are improved with increasing MMA content; however, tensile strength is reduced. High modulus without much reduction in tensile strength can be achieved if the MMA content is 50–60 parts per hundred rubber.

Natural antioxidants for radiation vulcanization of natural rubber latex

The anti-oxidant properties of some non-water soluble amino acids were tested on radiation vulcanized natural rubber latex (RVNRL). Among these were cystine, tyrosine, asparagine phenyl alanine and alanine. The results indicate that all of these amino acids have anti-oxidant properties with cystine, alanine and asparagine, phenyl alanine exhibiting higher anti-aging properties on RVNRL. Combinations of these amino acids improved the antioxidant properties in RVNRL. Keratin from chicken feathers was also tested for its antioxidant properties in RVNRL. Different methods of extraction of keratin gave different aging effects on RVNRL. Reduction of keratin with sodium bisulfite initiated antioxidant activity in RVNRL. Extraction of keratin with alkaline solution however caused pro-oxidant properties in RVNRL.

Hydrogel coating of RVNRL film by electron-beam irradiation

The tackiness properties of radiation-vulcanized natural rubber latex (RVNRL) film surfaces coated by various monomers were investigated in order to define the suitable hydrogels which reduce the tackiness of the film. In this context, different types of monomers, namely, N-vinyl-2-pyrrolidone (NVP), N,N-dimethylaminoethylamide (DMAEA), acrylic acid (AAc), n-butyl acrylate (n-BA), and 2-hydroxyethyl methacrylate (HEMA) as well as the monomer mixtures were tried with varying degrees of success. Coating the RVNRL film with 80% HEMA/20% n-BA by irradiation at 80 kGy using a low-energy electron beam gave a remarkable reduction in the surface tackiness of the RVNRL film. Several other attempts were made such as priming the RVNRL film with acid and aluminum sulfate prior to coating, mixing the aluminum sulfate into the monomer mixtures, and dipping the partially wet RVNRL film into the monomer to enhance the wettability of the monomers with the film. The photomicrographs taken illustrate that the decrease in tackiness with the coating is due to the increase of the surface roughness at an 80-kGy irradiation dose. The studies also revealed that the reduction in the contact angle and the increase in water absorption of the RVNRL film after irradiation are due to the formation of the hydrogel layer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1421–1428, 1999

Degradability testing of radiation‐vulcanized natural rubber latex films

AbstractThe degradability under various conditions of five kinds of radiation‐vulcanized natural rubber latex (RVNRL) films was studied. The treatments were leaching in methanol, leaching in 1% ammonia solution, mixing with tris(nonylated phenyl)phosphite (TNP) antioxidant, blending with poly(methyl methacrylate) (PMMA), and grafting with PMMA, Comparisons were made with sulfur‐vulcanized natural rubber latex (SVNRL) film. RVNRL films SVNRL film can be kept for a long time when indirectly exposed to sunlight at room temperature. However, the former degraded much more rapidly than did the latter. TNP was found to be very suitable as an antioxidant to prolong the life of RVNRL films under dry conditions. PMMA, either blended or grafted with RVNRL, was ineffective in the prevention of deterioration of RVNRL films. The rapid degradation of RVNRL products could be an advantage over SVNRL products in environmental and wildlife conservation. © 1994 John Wiley & Sons, Inc.

In vivo tissue/biomaterials toxic responses: Correlation with cytotoxic potential but not cell attachment

The relationships between cell attachment, cytotoxicity and in vivo tissue response such as muscle inflammation and eye irritation were investigated using lens materials, radiation vulcanized natural rubber latex (RVNRL) and standard reference materials (SRM). Five RVNRL materials, which induced muscle tissue inflammation, were cytotoxic and also significantly decreased cell attachment activities. The cytotoxic potential of a SRM made of segmented polyurethane correlated well with the decrease in cell attachment activity. However, among lens materials, cytotoxicity was detected in fluorosilicone acrylate but not in poly(methylmethacrylate) (PMMA), although the cell attachment activity of PMMA was the lowest. Eye irritation induced by wearing various kinds of lenses correlated with cytotoxic potential ( r = −0·90) but not with cell attachment activities. In conclusion, in vivo toxic tissue responses correlated well with cytotoxic potentials but not always with cell attachment activity. Our experimental results also showed that direct contact colony formation was mainly inhibited by cytotoxicity, but not the low activity of cell attachment.

Improvement of ageing properties of rubber films prepared from radiation‐vulcanized natural rubber latex

AbstractRadiation‐vulcanization of natural rubber latex (NRL) with n‐butyl acrylate gives a higher tensile strength for films obtained after casting. The ageing properties of radiation‐vulcanized natural rubber in the presence of various antioxidants have been investigated. In order to find out suitable antioxidants for radiation‐vulcanized natural rubber latex (RVNRL) films, extraction of the gel fraction was carried out in xylene with 1 wt.‐% antioxidant and air bubbling. Antioxidants which give less reduction in gel fraction due to oxidative degradation during extraction are effective for ageing tests of RVNRL films. It was found that tris(nonylated phenyl) phosphite (Nonflex TNP) and 2,5‐di‐tert‐amylhydroquinone (Antage DAH), among 12 different antioxidants tested, were the most effective antioxidants for RVNRL films.

Toxicological evaluation for biomaterials: Examinations of radiation vulcanized natural rubber latex

Our studies indicated that the thickness of the inflammatory layer was the most useful parameter to evaluate tissue response among 13 histological parameters. There was good correlation between the cytotoxicity and the thickness of inflammatory layer. Histological findings showed that the inflammatory layer of radiation vulcanized natural rubber latex (RVNRL) films involved a slightly higher response than the negative implant at the 3rd post operative day although the inflammatory layer showed almost the same degree as the negative controls at the 7th day. The cytotoxic potential of the extracts prepared from RVNRL films was found to be weak by the colony assay. The hemolytic activity was also detected in the extracts of RVNRL films. The lysis of red blood cells and the release of haemoglobin was clearly caused by RVNRL film. Though the cytotoxic and tissue irritative activities of RVNRL are considered much weaker then sulfur-vulcanized latices, it was suggested that RVNRL contains some unknown substances showing weak toxicities including hemolysis.

Development of optical laser balloon and drainage from radiation vulcanized natural rubber latex

Rubber film made of radiation vulcanized natural rubber latex (RVNRL) has better transparency and lower toxicity compared with sulfur-vulcanized latex film. Optical laser balloon (optical endoscopical balloon) and drainage were developed by using RVNRL. An endoscope was equipped with a saline-filled latex rubber balloon at its tip to displace contaminating blood, bile, or gastric contents during operative portoscopy, biliary endoscopy, or upper gastrointestinal endoscopy. The transmission of Nd-Yag laser through the balloon is 98%, higher than the sulfur-vulcanized latex rubber (75%). High transparency of the drainage bag facilitated easy observation of discharged fluids without detaching the bag from the tube.