NR Films Research Articles

Optimizing natural rubber blends for examination gloves: Vacuum radiation for mechanical strength and solvent barrier

AbstractNatural rubber (NR) is emblematic of sustainability compared to synthetic rubber. However, the tradition of adding sulfur as a vulcanization ingredient results in the release of toxic substances and the potential for health issues. In this study, a feasible strategy was proposed to replace sulfur and discover a safe bulk modification process for NR films. The results have shown that the NR particle size was disintegrated to below 10 nm by gamma irradiation. High tension strength up to 24.45 MPa was observed in the vulcanized NR blend film, which could be elongated up to 800% strain after exposure to an optimum dose of 14 kGy. In comparison to commercial NR latex and nitrile gloves, the vulcanized NR/ SIS films exhibited better chemical resistance ability against hexane, methanol, toluene, and acetone, as revealed by the permeation test. The appearance of amorphous regions and highly oriented NR crystallites was observed through transmission electron microscopy. Findings from this study propose the vacuum radiation strategy that can replace conventional vulcanization methods, resulting in NR films with high mechanical and barrier performance. Furthermore, the emission of toxic substances is reduced by this green process, making it practically useful for potential chemical‐resistant examination glove applications.

Controllable synthesis of Sn:ZnO/SnO2 nanorods: pH-dependent growth for an ethanol gas sensor

Tin-doped zinc oxide/tin oxide nanorod (Sn:ZnO/SnO2 NR) films were successfully synthesized using a solution immersion method by manipulating the pH concentration of the solutions to fabricate an ethanol gas sensor. Sn:ZnO/SnO2 NR films were prepared at constant Sn:ZnO solution pH (5.5), while the pH of the SnO2 solutions was varied between 4.5 and 6.5. In this study, the structural, morphological, and optical properties of Sn:ZnO/SnO2 NR films were investigated. The diameter and thickness of Sn:ZnO/SnO2 NR films were found to increase with the SnO2 pH. Interestingly, the Sn:ZnO/SnO2 NR sample that was prepared at SnO2 solution pH 5.5 showed the highest relative peak intensity along the c-axis plane orientation, which enhanced the sensor performance due to the shorter carrier pathway. In addition, this sample indicated a higher level of surface donor-related defects, which are favorable for sensing device performance. The samples were exposed to ethanol gas to measure their gas-sensing properties. Sn:ZnO/SnO2 NR films prepared at SnO2 solution pH 5.5 showed the highest sensing performance with short response/recovery times.

Infrared Thin Film Detectors Based on Thermoresponsive Microgels with Linear Shrinkage Behavior and Gold Nanorods.

To overcome the drawbacks of existing infrared detectors, infrared thin film detectors based on microgels and gold nanorods (Au NRs) are investigated. The microgels with a linear shrinkage of the hydrodynamic diameter between 10 and 55 °C are copolymerized by monomers di(ethylene glycol) methyl ether methacrylate, oligo(ethylene glycol) methyl ether methacrylate, and acrylic acid with a molar ratio of 1:1:1. Homogenous thin films are obtained by spin coating from an aqueous solution on silicon substrates. Upon heating in a water vapor atmosphere, the film thickness of the hybrid films linearly decreases. Heat generation from a plasmon resonance enhanced absorption of the infrared radiation by the Au NRs triggers a linear shrinkage in the hybrid microgel-Au NR films as well. A linear correlation between the film thickness and the applied infrared power density is observed. The sensitivity is enhanced by a slight increase in the amount of Au NRs in the films. Infrared detectors are constructed from the hybrid microgel-Au NR films by adding two electrodes via deposition of two silver layers at the film ends. By monitoring the ohmic resistance, the intensity of the incident infrared light can be obtained. The detectors not only possess a good reversibility and fast response rate but also show a high stability after the resistance measurements. Compared with the traditional infrared detectors, the infrared thin film detectors based on microgels are sensitivity adjustable. Thus, they can be promising candidates for replacing expensive inorganic infrared detectors in areas of daily life applications.

Energy dissipation in natural rubber latex films: The effect of stabilizers, leaching and acetone‐treatment

AbstractNatural rubber (NR) is a versatile material possessing outstanding mechanical properties, which can be used in multiple applications including the rapidly developing dielectric elastomer generators (DEGs). One of the drawbacks of the existing DEGs is their low efficiency, which can be improved by lowering the dielectric and mechanical losses originating from the material. Therefore, the present research was focusing on assessing the ways to minimize the dielectric and mechanical losses of NR films rather than developing a DEG. In this article, the effect of natural proteins and the rubber stabilizers on energy dissipation of NR films was evaluated. Moreover, the effect of sample posttreatment (with water and acetone), curing and time after cure was discussed. As a result, deproteinized NR stabilized by ammonium caseinate outperformed unmodified NR due to reduced dielectric losses, mechanical hysteresis and stress relaxation. Moreover, the posttreatment methods were found to moderately reduce the material‐relates losses.

Lactic Acid Modified Natural Rubber–Bacterial Cellulose Composites

Green composite films of natural rubber/bacterial cellulose composites (NRBC) were prepared via a latex aqueous microdispersion process. The acid modified natural rubber/bacterial cellulose composites (ANRBC), in which lactic acid was used, showed significant improvement in mechanical properties, melting temperature, and high resistance to polar and non-polar solvents. The ANRBC films exhibited improved water resistance over that of BC and NRBC films, and possessed a higher resistance to non-polar solvents, such as toluene, than NR and NRBC films. The modification had a slight effect on the degradability of the composite films in soil. The NRBC and ANRBC films were biodegradable; the NRBC80 and ANRBC80 films were degraded completely within 3 months in soil. NRBC and ANRBC showed no antibacterial activity against Escherichia coli and Staphylococcus aureus and did not show cytotoxic effects on the HEK293 and HaCaT cell lines.

THE Effect of Azido-Starch as Filler on Tensile and Tear Properties of Natural Rubber Latex Films

The azido starch/Natural Rubber (azo-starch/NR) latex films were prepared with control (0), 0.5, 1.0, 1.5 and 2.0 phr of azido-starch loadings. The azido starch functional groups were characterized by Fourier Transform Infra- Red (FTIR) analysis to observe the presence of significant peaks of azide (N3).The control and azido starch-filled NR films were subjected to tensile test and tear test in order to investigate the effect of the addition of azido-starch on the mechanical properties of azo-starch/NR latex films. The tensile strength of azo-starch/NR latex films was increased with increasing azido-starch loading and slightly decreased after 1.0 phr loading. The optimum tensile strength of azo-starch/NR latex films is obtained at 1.0 phr loading. The moduli (M100 and M300) and tear strength also increased with increasing azido-starch loading. However, the elongation at break (EB) was almost similar with increasing azido-starch loading. The swelling test was done to determine the swelling index, crosslink density and rubber-filler interaction of azo-starch/NR films. The swelling index was decreased but the crosslink density increased with increasing azido-starch loading indicating the formation of crosslinks between azido-starch and rubber macromolecules.

Electrical transport mechanisms and photovoltaic characteristics of Au/neutral red/p-Si/Al heterojunction solar cell

Uniform thin films of neutral red, NR, have been successfully prepared by thermal evaporation technique. X-ray diffraction patterns showed that the structure of NR film consists of nanocrystallites dispersed in amorphous matrix. Increasing annealing temperature influences crystallite size and quantity of amorphous phase. The high absorption of NR films in visible region of spectra supports the application of NR film as an absorber in photovoltaic devices. Hybrid organic–inorganic heterojunction solar cell, Au/NR/p-Si/Al, was fabricated. The current–voltage characteristics of the heterojunction diode have been studied in the temperature range of 300–355K and in the voltage range (−2 to 2V). The device showed a series resistance of 2.64kΩ, shunt resistance of 237kΩ, rectification ratio of 106 at ±1V and ideality factor of 1.8 at room temperature. It was found that the conduction mechanisms of the diode are controlled by the thermionic emission at forward voltage bias ≤0.2V and space charge limited current (SCLC) conduction in the voltage range 0.2<V≤2V. The capacitance–voltage characteristics of the NR/p-Si device were studied at room temperature in dark condition. Energy band diagram for NR/p-Si device was constructed. The device under illumination with light of intensity 20mW/cm2 gives values of photovoltaic parameters as: open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and power conversion efficiency (η) are 0.46V, 1.78mA, 0.29 and 2.37%, respectively.

Influence of pyrolytic seeds on ZnO nanorod growth onto rigid substrates for photocatalytic abatement of Escherichia coli in water

ZnO nanorods (ZnO NRs) were grown on ZnO seeded fluorine doped tin oxide (FTO) substrates at low temperatures (90 °C) from Zn2+ precursors in alkaline aqueous solution. The ZnO seeds were deposited on the FTO substrate heated at 350 °C by spray pyrolysis of a zinc acetate solution in a water ethanol mixture. The structure of seeds was tuned by the ethanol water ratio, Γ, which controls the solvent evaporation rate of drops impinging the substrate. The relationship between the microstructure and optical properties of the ZnO NR films and the photocatalytic antibacterial activity for Escherichia coli abatement, was determined through a detailed characterization of the material. The higher photocatalytic antibacterial activity was performed by ZnO NR films grown on seeds deposited from solutions with Γ in the 0.0–0.03 range. With these films, the population of viable E. coli dropped more than six orders, from 8 × 108 to 4 × 102 CFU. These results show the potential of these materials in water disinfection.

Studies on the Physicochemical Properties of Natural Rubber/Polyethylene Blends and the Impact of Radiation on Their Properties

NR and Polyethylene (PE) were blended at different compositions of PE, like 00, 35, 50, 65, 85 and 100% by extrusion method and then the blend films were made by hot press. The blends, NR and PE films were irradiated and their mechanical properties were investigated before and after leaching. Blend compositions were optimized and found that the 50–65% PE blends give the best quality. It is also found that 5–8 kGy radiation doses are optimal for improved properties of blends. Leaching enhances mechanical properties and lower radiation doses give more enhanced mechanical properties compared to unleached one.

Silver nanoparticles in polyvinylpyrrolidone grafted natural rubber

Abstract Polyvinylpyrrolidone grafted natural rubber (PVP- g -NR) latex was used as matrix to synthesize silver nanoparticles. The average diameter of the silver nanoparticles is 4.1 nm. The modified natural rubber was previously formed via in situ polymerization of N-vinyl-2-pyrrolidone (NVP) in natural rubber latex (NRL) using cumene hydroperoxide (CHP) and tetraethylenepentamine (TEPA) as a redox initiator. The evidence of PVP grafted rubber particles was demonstrated by extraction as well as gravimetric and FTIR studies. Transmission electron microscopy (TEM) studies of the Ag + /PVP- g -NR films after exposure to UV light, revealed distinct layers comprised of PVP-stabilized silver particles surrounding the rubber particle. This confirms the grafting of PVP, which stabilizes the silver particles as well as the rubber particles in a role that is similar to that of the protein in our previous work.

Biaxial Orientation in Triple Centrifuged Natural Rubber

AbstractNatural rubber (NR) latex was purified through triple centrifugation process and film samples were prepared. The strain‐induced crystallization was studied during the uniaxial elongation of the NR samples at room temperature. Crystalline orientation was detected by wide angle x‐ray diffraction (WAXD) measuring the intensity of 200 and 120 reflections. The WAXD patterns were compared with the aspect ratio (width/length) of the original NR films. The results indicate that the induced crystals have a biaxial orientation (BO), where the c‐axis is parallel to the draw direction and the a‐axis is parallel to the film surface. Using the WAXD through patterns, we distinguish the highly oriented BO region in the samples. In order to analyze the structure and properties of the NR, the effect of BO is an essential factor.

Photo-degradation of synthetic and natural polyisoprenes at specific UV radiations

Synthetic and natural polyisoprenes (PI) films were exposed to different UV light sources and then analyzed by Fourier transform infrared (FTIR) and UV spectroscopy, before and after exposure to the UV source. Films of PI standards were separately irradiated by UV sources of different wavelengths: 253, 300, and 350 nm. The photo-oxidation was monitored by looking at the dependence of the IR absorbances of the C C, C O, and O–H stretching and the C–H wagging modes of cis- and trans-PI. Irradiation at 253 nm leads to cross-linking and polymer reticulation avoiding the complete oxidation of the polymer film. Under 300 nm irradiation, the chain-scission reactions occur preferentially leading to the complete oxidation of the film. Irradiation at 350 nm leads to photo-oxidation only for exposure times larger than 12 h. The natural PI rubbers, Hevea brasilienses (HB), Hancornia speciosa (HS), and Mimusops globosa (MG) were characterized by DSC and FTIR as being high cis-1,4-PI (HB and HS) and high α- trans-1,4-PI (MG). The photo-oxidation of NR presented different kinetics, with induction times smaller than those observed for the cis- and trans-PI standards. The faster photo-degradation process observed for NR films was assigned to the presence of impurities characterized by the presence of O–H and C O str bands in the FTIR spectra, even before UV irradiation.

Characterization and Performance Testing of Guayule Latex

Abstract Physical and biological properties were determined for a preliminary production run of low-ammonia latex from guayule (GR latex). GR latex, and dipped films produced from compounded GR latex, contain none of the Hevea allergens known to elicit Type I systemic allergic reactions. The polymer phase of GR latex has a lower bulk viscosity and a higher resin content than that of NR. In addition, GR latex serum and rubber lack the activating components present in NR latex. As a result, GR latex cures more slowly and reaches a lower state of cure. The aged stress-strain properties of cured GR films are nonetheless similar to those of NR films.