Natural Rubber Latex Films Research Articles

Antibacterial Polyelectrolytic chitosan derivatives conjugated natural rubber latex films with minimized bacterial adhesion

AbstractWater soluble polyelectrolytic derivatives of chitosan (CDs) with carboxyl (COO−) and quaternary ammonium (NH4+) groups were synthesized and characterized by NMR, FT‐IR, TGA and zeta potential analyses; while degree of substitution was determined by potentiometric titrations. Both CDs in the as‐synthesized form exhibited antibacterial zones against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The CD conjugated vulcanized natural rubber latex (NRL) films were investigated for understanding the level of bacterial adhesion and bactericidal properties as a function of the polyelectrolytic groups present. NRL Films modified at ambient conditions were found effective against Pseudomonas aeruginosa (P. aeruginosa). The biofilm assay results demonstrate that CD conjugated samples exhibit significantly reduced adhesion (63.8%) against P. aeruginosa. Further, alterations observed in cellular morphology of attached bacteria indicate that the modified surface of films is bacteriocidal while presence of significantly higher level of extra cellular polymer substances (EPS) were detected on control NRL films.

Effect of vulcanization systems on the properties of natural rubber latex films

Natural rubber latex (NRL) films have high elasticity and flexibility and are excellent protection barriers against micro-organisms. For this reason, NRL is often used in the manufacture of medical products, such as gloves, condoms, blood transfusion tubes and catheters. The objective of this study was to evaluate the effect of two accelerators, ZDEC and TMTD, of the sulphur-based curing system, on the rheometric, crosslink density, thermal and mechanical properties. For this purpose, the compositions of NRL films were designed using two-level factorial design with a centre point, considering the variation from − 1 to + 1 of the levels of sulphur and accelerators. The results indicated that the delta torque was influenced by the addition of sulphur only. Scorch time (Ts1) and optimum vulcanization time (T90) decreased as TMTD was added to the formulations. TMTD only contributed to the crosslink density when low amounts of sulphur were used. Higher values of tensile strength were observed for sulphur, ZDEC and TMTD amounts, but it was close to the centre point experiments. SEV and EV vulcanization systems did not necessarily produce crosslinks that require higher energy to brake when compared to CONV system.

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.

Natural rubber latex film in the presence of renewable vegetable oil nanoemulsion

Vegetable oil with the advantages of biodegradability and low cost has been used as a plasticizer in the rubber industry. This study investigates the conditions of vegetable oil nanoemulsion as a plasticizer in natural rubber (NR) latex. Vegetable oil nanoemulsion with the particle size of 10.4 nm is prepared from blending coconut kernel oil/soybean oil, Tween 80 and water using phase inversion temperature method. The vegetable oil nanoemulsion is then added to NR latex. During the initial three days, latex particles have swollen, but subsequently they shrunk from 2673 to 1511 nm due to phase inversion. The result indicates that the tensile strength of latex films could be improved significantly with both higher incubation and vulcanization temperatures at 50 °C and 120 °C, respectively. Contact angle on the film surface is less than 90°, showing that there is no oil blooming onto the surface.

Physical and mechanical properties of natural rubber latex film (Rubber Dam) products with filler nanocrystal cellulose from peanut shell (Arachis hypogea L.) and synthetic dyes

Rubber dam is considered as an ideal device for tooth isolation. Rubber dam is one of example product from natural rubber latex. Peanut shell is one of the industrial waste containing 35,7% of cellulose. Nanocrystal cellulose from peanut shell can be an alternative waste utilization and have potential as filler in natural rubber latex films. Studies about effect of loading nanocrystal crystal as filler on natural rubber latex films with polyvinyl pyrrolidone (PVP) and using synthetic dyes have been carried out on crosslink density and mechanical properties such as tensile strength, elongation at break and tensile modulus. The process begins with pre-vulcanization of natural rubber latex at temperature 70°C with 0, 2, 4, 6, 8 gram of filler loading and followed by vulcanization at 120°C for 10 minutes. The results obtained with loading nanocrystal crystal filler using synthetic dyes for physical properties, crosslink density, will increase with the increase of filler loading. For mechanical properties, tensile strength and tensile modulus will increase with greater filler loading, while elongation at break will decrease. The best results are obtained for mechanical properties of natural rubber latex film products using synthetic dye on 6 gram nanocrystal cellulose of filler loading.

Comparison of weight loss in natural rubber latex film (rubber dam) filled nanocrystal cellulose and synthetic dyes with soil burial methods

Biodegradation of natural rubber latex products filled with nanocrystal cellulose from peanut shell is carried out by soil burial methods with and without using fertilizer. Testing is done by calculating the loss of sample weight for 5 weeks with observation every 1 week. Samples were tested the morphology using Scanning Electron Microscope (SEM) and Fourier Transform Infra Red (FTIR). Natural rubber latex film samples showed that the loading of nanocrystal cellulose fillers from peanut shells was biodegradable faster in soil burial method with addition of fertilizer in soil compared to no addition of fertilizer.

Reinforcement of Natural Rubber Latex Using Jute Carboxycellulose Nanofibers Extracted Using Nitro-Oxidation Method.

Synthetic rubber produced from nonrenewable fossil fuel requires high energy costs and is dependent on the presumed unstable petroleum price. Natural rubber latex (NRL) is one of the major alternative sustainable rubber sources since it is derived from the plant ‘Hevea brasiliensis’. Our study focuses on integrating sustainably processed carboxycellulose nanofibers from untreated jute biomass into NRL to enhance the mechanical strength of the material for various applications. The carboxycellulose nanofibers (NOCNF) having carboxyl content of 0.94 mmol/g was prepared and integrated into its nonionic form (–COONa) for its higher dispersion in water to increase the interfacial interaction between NRL and NOCNF. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses of NOCNF showed the average dimensions of nanofibers were length (L) = 524 ± 203 nm, diameter (D) 7 ± 2 nm and thickness 2.9 nm. Furthermore, fourier transform infra-red spectrometry (FTIR) analysis of NOCNF depicted the presence of carboxyl group. However, the dynamic light scattering (DLS) measurement of NRL demonstrated an effective diameter in the range of 643 nm with polydispersity of 0.005. Tensile mechanical strengths were tested to observe the enhancement effects at various concentrations of NOCNF in the NRL. Mechanical properties of NRL/NOCNF films were determined by tensile testing, where the results showed an increasing trend of enhancement. With the increasing NOCNF concentration, the film modulus was found to increase quite substantially, but the elongation-to-break ratio decreased drastically. The presence of NOCNF changed the NRL film from elastic to brittle. However, at the NOCNF overlap concentration (0.2 wt. %), the film modulus seemed to be the highest.

Chitin nanocrystals reticulated self‐assembled architecture reinforces deproteinized natural rubber latex film

AbstractNatural rubber (NR) latex was initially deproteinized, then, the interactions between chitin nanocrystals (ChNCs) and deproteinized natural rubber (DNR) latex particles in an aqueous system and the properties of DNR/ChNCs composites were investigated. Composite films were obtained by casting and evaporating off the prevulcanized DNR/ChNCs complexation rather than simply mixing of DNR latex and ChNCs suspension. The results of DLS and TEM confirmed that this kind of complexation was formed between negative charged DNR and positively charged ChNCs by self‐assembly. The tensile strength of composite films containing 4 wt% ChNCs was 25.00 ± 1.42 MPa, which was 3.11 multiples of the pure pre‐vulcanized DNR. DNR/ChNCs composite films could provide excellent mechanical properties and avoid allergies caused by proteins in NR latex.

Effects of post-gamma irradiation on swelling and mechanical properties of gamma vulcanized natural rubber latex (GVNRL) films

Gamma vulcanized natural rubber latex (GVNRL) films have shown promising properties for various applications that require less hazardous chemicals used or released during manufacturing and/or utilization. Examples of potential applications include the uses as chemical-free latex gloves in medical or food-related facilities and as stretchable latex covers for food and agricultural products. However, due to possible degradation on swelling and mechanical properties of these films from post-gamma irradiation used for sterilization, thorough investigations are required in order to fully understand their possible changes and/or degradations in properties of interest. As a result, this work investigated on effects of post-gamma irradiation on swelling and mechanical properties of natural rubber latex (NRL) films, which were pre-vulcanized using 12-kGy and 24-kGy gamma irradiation. The properties of interest in this work included tensile modulus at 300% elongation, tensile strength, and elongation at break, as well as other related physical properties such as swelling ratios and crosslink densities. The results showed that, for samples before post-gamma irradiation, the GVNRL films with 24-kGy vulcanizing dose had higher tensile modulus, tensile strength, and crosslink density, but lower elongation at break and swelling ratio, than the films with 12-kGy vulcanizing dose. However, after post-gamma irradiation at the accumulated dose of 24 kGy, the films with 12-kGy vulcanizing dose showed significant improvements in the values of tensile modulus, tensile strength, and crosslink density, whereas the films with 24-kGy vulcanizing dose showed noticeably degradation in these properties. Hence, the overall results suggested that, while higher gamma vulcanizing doses could initially produce NRL films with higher mechanical strength, they were more negatively affected by post-gamma irradiation such that mechanical degradation could be observed.

Synergistic Cross-linking and Reinforcing Enhancement of Rubber Latex with Cellulose Nanocrystals for Glove Applications

The effect of cellulose nanocrystals (CNCs) on the reinforcing, cross-linking, and solvent barrier properties of lightly cross-linked natural rubber (NR) latex films for dipped goods applications w...

Efficient stoneware hand mold for slip casting in natural rubber latex glove preparation

Disposal medical gloves are an important product to maintain hygienic conditions, ensuring security for patients and safeguarding against infections. They are used in many fields, such as dental and medical, beauty and cuisine, food and pharmaceutical industries. Presently, aging populations and an emerging middle class in developing countries require medical gloves at a higher volume. Therefore, the demand for medical gloves increases continuously. In this work, two types of hand molds were prepared from stoneware clay and plaster to be used in the natural rubber glove preparation. The ceramic stoneware and plaster hand molds were prepared by the slip casting. The obtained stoneware hand molds were found to be superior to the commercial hand molds. Natural rubber latex (NRL) gloves were fabricated by dipping the stoneware hand mold coated with a coagulant into the NRL compound using the sulfur curing system at 120°C for 30 min. The latex solid:water weight ratio, drying and firing temperatures, and firing time used to prepare stoneware hand molds were found to affect the adsorption–adhesion properties between the mold surface and the NRL films. The obtained NRL films were further characterized for the physical properties such as appearance, film thickness, tackiness, and effusion of the phase formation by X-ray diffraction, the microstructure by scanning electron microscope, and the mechanical properties. The NRL glove films prepared by the stoneware hand mold possessed the high percentage elongation at break and the maximum load stress equal to 1343.30 ± 78.36% and 12.74 ± 2.34 MPa, respectively. On the other hand, the latex glove films prepared by the plaster hand mold with 80 consistency provided the percentage of elongation at break and the maximum load stress equal to 531.76 ± 2.54 and 21.01 ± 0.08 MPa, respectively.

Relationships between swelling temperature and shape memory properties of palmitic acid-based shape memory natural rubber

This article investigates the effect of swelling temperature on palmitic acid-based shape memory natural rubber (SMNR). SMNR has high storage modulus and excellent energy absorption capability which is suitable to replace the electronic parts in the lightweight machine. Although the swelling process increased the trigger temperature of palmitic acid-based SMNR, high thermal energy in swelling process might accelerate the degradation of the SMNR. To verify the swelling effect, two rubber sources were adopted in the sample preparation and immersed into molten palmitic acid. A custom-made elongation device which is introduced in the methodology section was used to measure the shape memory parameters under different deformation strains (100%, 200% and 300%). It was found that both swollen rubber sources stood their own beneficial shape memory parameters. For example, high shape fixation ($$>90\%$$) was found in natural rubber latex film (NRLF) specimen, while natural rubber (NR) specimens had outstanding shape recovery (100%). Swelling experiment revealed that the solvent diffusion rate was increased in higher swelling temperature, but crosslink density of rubber specimen limited the penetration of palmitic acid and maximum solvent uptake amount. Strain control mode test indicated that the swelling temperature accelerated the chain scission process which decreased the crosslink density of rubber specimens, but shape fixation was increased by high void formation. The DSC test clearly showed that trigger temperature varied with the solvent contents in the rubber specimens. Scanning electron microscopy images illustrated that the precoated palmitic acid was formed on the rubber molecules. The relationship between the swelling temperature and shape memory parameters of SMNR was established and the trigger temperature of SMNR was successfully increased near the melting temperature of fatty acid.

Knotty Tear Phenomena and Effect of Maturation Time on Knotty Tear in Filled Natural Rubber Latex Films

Knotty tearing is a phenomena normally observed in reinforced black-filled natural rubber (NR) vulcanizate but not in gum NR vulcanizate. Unfortunately the underlying cause of knotty tear is still not fully understood and need to be unraveled. Many factors contribute to knotty tear behavior which include suppression of strain-induce crystallization, protein content of latex, vulcanization temperature and pre-vulcanization and post-vulcanization of latex. In this study, we concentrate on varying the maturation time during compounding process in filled NR latex (NRL) to study knotty tear behavior. The maturation time were varied in the range (0 – 72) hrs; and the tear deviation were measured to determine the extent of knotty tear phenomena. It was found that at the optimum maturation time of 24 hrs samples show highest tearing energy and show knotty tear phenomena with the least angle of tear deviation.

Ultrafine calcium carbonate-filled natural rubber latex film: mechanical and post-processing properties

This study aims to improve the dispersion of treated calcium carbonate (CaCO3) in natural rubber latex (NRL) films. Ball mill and ultrasonic methods were used to break down the particle size of CaCO3, and the combined effect of ball mill/ultrasonic and ultrasonic/ball mill methods with their optimum processing times was applied to re-agglomerate and further break down the particle size of CaCO3. The particle size and dispersibility of treated CaCO3 were characterized by particle-size analysis, transmission electron microscopy (TEM), and Zeta-potential measurement. The particle-size analysis and TEM results revealed that the particle size of CaCO3 reduced down to 1.4 µm with less agglomeration using ultrasonic for 120 min and ball mill for 72 h. Zeta--potential measurement also indicated that the ultrafine-treated CaCO3 with a broad particle-size distribution was compatible with NRL particles. The treated CaCO3 loadings from 5 to 20 phr were filled in the NRL compounds. NRL/CaCO3compounds showed decrease in viscosity and cross-link density, but increase in swelling index. It was found that tensile strength, modulus at 100% elongation, elongation-at-break, swelling index, and cross-link density of the films were improved with addition of 10 phr of CaCO3. At 20 phr of filler loading, the increment rate of tensile strength of NRL/CaCO3 films was 44% after leaching, and their retention percentage was 62% after heat aging. Therefore, ultrafine CaCO3-incorporated NRL can withstand under accelerated heat-aging condition.

The potential use of immobilized Bacillus cereus ATCC 14579 for biodegradation of natural rubber latex film added with Metroxylon Sagu pith form

The previous study reported that Bacillus cereus ATCC 14579 able to degrade natural rubber latex films added with Metroxylon Sagu pith waste form (MSPW/NR) and natural rubber (NR) latex films as main source of carbon and energy. Some attempts have been made to degrade them in the newly batch systems rather than disposing of them in landfill. Immobilization technique was performed to adsorb Bacillus cereus onto modified activated carbon. This work aims to study the potential of immobilized Bacillus cereus for biodegradation of MSPW/NR. The results revealed that 30% nitric acid for 2 hours impregnation time showed significant influence on Bacillus cereus adsorption. The highest adsorption capacity of Bacillus cereus was found to be 72.8% under its optimum conditions. The weight loss of MSPW/NR by 12.843 % were obtained after 14th days biodegradation period. Thus, immobilization of Bacillus cereus ATCC 14579 has potency to provide a biotechnological solution to the waste rubber and latex disposal problem.

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.

Effect of Bio Fillers on Mechanical Properties of Natural Rubber Latex Films

Rubber industry is one of major raw material for many industries around the world. Therefore, supplying quality raw material is major concern among the market player. The objectives of this paper is to formulate natural rubber latex (NRL) by addition of bio fillers and to determine the impact of bio fillers (rice husk ash and tacca starch) towards the tear strength and tensile strength of the film samples. Normally, filler compounded in NRL named carbon black filler is chemical based, expensive and difficult to handle. Blending method was applied whereby named as compounding process. The vulcanized NRL was blended with the bio fillers before manual dipping process applied to obtain the film. The bio filler loaded was 10 phr and 30 phr. The optimum concentration was found to be 10 phr of tacca starch, producing tensile stress at maximum load was 18 Mpa while elongation at break was 650%. In addition, tensile stress at 300 mm elongation was 2 Mpa and tear strength is 15 N/mm.

Colloidal properties of precipitated calcium carbonate dispersion and its effect on prevulcanised natural rubber latex rheology and film tensile properties

In this work, the interaction between PCC in NR latex and physical properties of the resulting films were studied. PCC dispersion was first prepared and its colloidal properties together with the colloidal properties of prevulcanised natural rubber (PV-NR) latex were investigated using particle size analysis, zeta potential and rheology. PCC dispersion and PV-NR latex were then mixed together and their interaction was followed by rheology. Next, the dipped films were prepared and the resulting film thickness and tensile properties were determined. PCC dispersion showed an average particle size of 4.2 µm with a wide particle distribution whereas PV-NR latex showed an average particle size of 0.74 µm with a much narrower particle distribution. Viscoelastic studies showed PCC dispersion to be an elastic material whereas PV-NR latex was observed to be a viscous material. Mixing of the two materials produced a change in the rheological behaviour. Up to 30 phr PCC loading, flow studies revealed the mixtures to behave as Bingham materials but above that, the mixtures behaved as Herschel–Bulkley materials. Viscoelastic measurements showed that the initially viscous PV-NR latex became more elastic with increasing PCC loading. A shift from dominant viscous to dominant elastic behaviour was observed with the addition of 80 phr PCC in the latex. Thickness and tensile stress of the dipped films increased with increasing PCC loading. However, both tensile strength (TS) and elongation at break (EB) of the films reduced with increasing PCC loading. Ageing caused reduction in tensile stress but EB and TS increased. The increase in TS was, however, only observed to occur up to 15 phr PCC loading.

The Influence of Sago Starch Dispersion on Mechanical Properties of Biodegradable Natural Rubber Latex Films

Abstract The biodegradability of natural rubber (NR) latex films can be improved by the addition of starch dispersion, which commonly prepared using anchoid as a dispersing agent. The purpose of this study was to investigate the influence of different types of dispersing agent; sodium alginate and carboxymethyl cellulose (CMC) in preparation of sago starch dispersions. The effect of different types of sago starch dispersions on mechanical properties (tensile and tear strength), swelling index and crosslink density of NR latex films were investigated. The results revealed that a good dispersion stability of sago starch sodium alginate gave better swelling index and mechanical properties, and higher crosslink density compared to NR latex with sago starch CMC. Based on the results obtained, the utilization of sodium alginate can be used as a replacement of anchoid in preparing the sago starch dispersions which gives comparable mechanical properties of biodegradable NR latex films.

PMMA particles coated with chitosan-silver nanoparticles as a dual antibacterial modifier for natural rubber latex films

The antibacterial activity in sulphur prevulcanized natural rubber (SPNR) latex film was effectively improved by deposition of poly(methyl methacrylate) (PMMA) particles encircled with chitosan-coated silver nanoparticles (AgNPs-CS). With the focus on a green process, CS was selected as a safe reducing and stabilizing agent for the one-step synthesis of AgNPs-CS (38 nm, +40.4 mV) in an autoclave. The adsorption of small-sized AgNPs-CS directly onto rubber film did not provide an inhibitory effect on S. aureus. It also had a low antibacterial effect on E. coli. This is because of the particles becoming completely/partially submerged into the soft rubber matrix upon drying. Hence, the AgNPs-CS were fabricated as a shell surrounding a rigid PMMA core (496 nm, -30.9 mV). This was done using a heterocoagulation technique prior to coating on SPNR film. The presence of PMMA/AgNPs-CS on the surface of SPNR film effectively increased the surface roughness from ca. 44 to 150 nm. This substantially promoted the antibacterial activity against E. coli and S. aureus by way of contact killing and repelling mechanisms. The cytotoxicity on L-929 fibroblasts was also suppressed. This study would be, therefore, applicable to the development of antibacterial SPNR film with high surface roughness, low cytotoxicity. It could also be applied for other soft substrates.