Natural Rubber Latex Films Research Articles

A relationship between cross-link concentration and physical properties in natural rubber latex films at different calcium carbonate loadings

A relationship between cross-link concentration and physical properties in natural rubber latex films at different calcium carbonate loadings

Understanding the role of TEMPO-oxidized cellulose nanofiber on natural rubber latex nanocomposites

Cellulose nanofibers (CNF) were isolated from raw cotton fibers via 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation process. The isolated CNF were morphologically characterized using Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Entangled fibrous morphology with diameter in nano regime (15–20 nm) has been observed for the isolated nanofibers. X-ray diffraction (XRD) analysis confirms the high crystallinity of the isolated CNF. Further, the isolated CNF was used to reinforce natural rubber (NR) latex films. The crystallographic, morphological, and spectroscopic analysis of the NR/CNF nanocomposites was carried out. A strong interaction between the CNF and NR matrix has been identified and which reflects in the thermal stability and swelling behavior of NR/CNF nanocomposite films in toluene. The uniform dispersion and tangling effect of CNF along with strong NR-CNF interaction restrict the uptake of solvent through NR matrix.

Wearable Natural Rubber Latex Gloves with Curcumin for Torn Glove Detection in Clinical Settings.

Glove tear or perforation is a common occurrence during various activities that require gloves to be worn, posing a significant risk to the wearer and possibly others. This is vitally important in a clinical environment and particularly during surgical procedures. When a glove perforation occurs (and is noticed), the glove must be replaced as soon as possible; however, it is not always noticeable. The present article is focused on the design and development of a novel fluorescence-based sensing mechanism, which is integrated within the glove topology, to help alert the wearer of a perforation in situ. We hypothesized that natural rubber gloves with curcumin infused would yield fluorescence when the glove is damaged, particularly when torn or punctured. The glove design is based on double-dipping between Natural Rubber Latex (NRL) and an inner layer of latex mixed with curcumin, which results in a notable bright yellow-green emission when exposed to UV light. Curcumin (Cur) is a phenolic chemical found primarily in turmeric that fluoresces yellowish-green at 525 nm. The tear region on the glove will glow, indicating the presence of a Cur coating/dipping layer beneath. NRL film is modified by dipping it in a Cur dispersion solution mixed with NRL for the second dipping layer. Using Cur as a filler in NRL also has the distinct advantage of allowing the glove to be made stronger by evenly distributing it throughout the rubber phase. Herein, the optimized design is fully characterized, including physicochemical (fluorescence emission) and mechanical (tensile and tear tests) properties, highlighting the clear potential of this novel and low-cost approach for in situ torn glove detection.

Development and characterization of natural rubber latex wound dressings enriched with hydroxyapatite and silver nanoparticles for biomedical uses

Skin injuries are some of the most common problems faced by those with trouble healing. Medicine currently searches for multifunctional biomaterials that can enhance healing, while providing surface features favorable to human skin and unfavorable to microorganisms. In this context, this work aims to produce natural rubber latex (NRL) dressings enriched with hydroxyapatite - Ca10(PO4)6(OH)2 - and silver nanoparticles through magnetron sputtering. These dressings are provided with specific properties such as wettability, roughness and bacteriostatic activity to prevent cell adhesion and allow tissue regeneration without contamination by microorganisms. Modified NRL films showed hydrophilic character, along with an increase in roughness and Ca/P molar ratio of 0.7. The rate of fluid absorption of the films with (phosphate-buffered saline) solution demonstrates that the dressings will retain a certain amount of exudate. Also, silver, which is most likely in the form of nanoclusters, was leached in a proper quantity into a fluid medium. Biological assays proved that the dressings did not present cytotoxic effects in contact with fibroblasts and displayed bacteriostatic activity against S. aureus and E. coli. Fibroblast cells did not adhere over the samples, but proliferation was improved with time. This work successfully joined the benefits of calcium phosphate with silver-enrichment against bacteria using surface engineering techniques on the modification of NRL. Ultimately, the dressings produced in this study are promising for application in wound healing.

Cement – natural rubber latex stabilised recycled concrete aggregate as a pavement base material

This research investigated the influence of natural rubber latex (NRL) on the performance of cement stabilised recycled concrete aggregate (RCA) as a pavement base material. The influence factors studied included different cement at contents and dry rubber to cement (r/c) ratios. The NRL replacement enhanced the unconfined compressive strength (UCS) and indirect tensile strength (ITS) of cement stabilised RCA. The highest UCS and ITS of cement-NRL stabilised RCA were found at the optimum r/c ratios. Beyond these optimum r/c ratios, the UCS and ITC values decreased although all UCS values were still greater than the minimum requirement for base material. Microstructural analyses indicated the detected cement hydration products and NRL films, which NRL films were found to improve the adhesion and interparticle bonds of RCA particles. However, the excessive NRL additive retarded the cement hydration, whereby the UCS and ITS development was low when the r/c was greater than the optimum value.

Natural Rubber (NR) Latex Films with Antimicrobial Properties for Stethoscope Diaphragm Covers.

Systematic disinfection of the stethoscope diaphragm is required to ensure that it does not act as a vector for cross-transmission of health-related diseases. Thus, an antimicrobial latex film could be used as a cover to inhibit pathogenic bacteria from growing on its surface. The aim of this work is to determine the antimicrobial activity and mechanical properties of antimicrobial natural rubber (NR) latex films with different types of antimicrobial agents (mangosteen peel powder (MPP), zinc oxide nanoparticles (ZnO NP), and povidone-iodine (PVP-I)). The antimicrobial loading was varied from 0.5, to 1.0, and 2.0 phr to monitor the effective inhibition of Gram-negative bacteria and fungi growth. For MPP and PVP-I antimicrobial agents, a loading of 2.0 phr showed good antimicrobial efficacy with the largest zone of inhibition. Simultaneously, ZnO NP demonstrated excellent antimicrobial activity at low concentrations. The addition of antimicrobial agents shows a comparable effect on the mechanical properties of NR latex films. In comparison to control NR latex film (29.41 MPa, 48.49 N/mm), antimicrobial-filled films have significantly greater tensile and tear strengths (MPP (33.84 MPa, 65.21 N/mm), ZnO NP (31.79 MPa, 52.77 N/mm), and PVP-I (33.25 MPa, 50.75 N/mm). In conclusion, the addition of antimicrobial agents, particularly ZnO NP, can be a better choice for NR latex films because they will serve as both an activator and an antimicrobial. In a clinical context, with regard to frequently used medical equipment such as a stethoscope, such an approach offers significant promise to aid infection control.

Development of<i> In Situ</i> Cooling Natural Rubber Film

Natural rubber latex (NRL) with the deproteinized process was interesting for cosmetic and transdermal drug delivery systems because of its notable characteristics. The purpose of this study was to develop in situ cooling films from deproteinized natural rubber latex (DNRL). Menthol, camphor, and volatile oils were added into DNRL emulsions for cooling effect and pain relief. The pH, rheological properties, particle size, and zeta potential of emulsions were examined. Then, the time of film-formation, morphology, and mechanical properties of the cooling NRL films were evaluated. The resultant emulsions revealed that their pH was about 5.7 - 6.3. The viscosity was in the range of 1000 – 3000 cps and indicated the pseudoplastic flow. The increasing amount of olive oil reduced the particle size and increased the negatively zeta potential of those emulsions. The film formation time of specimens was about 4.5 - 6.5 mins. The cooling films demonstrated smoothness and homogeneity. The presence of olive oil increased the softness of films. The increasing of oil volume increased the elasticity; however, it decreased the ductility of the films. This in situ cooling DNRL film was also effective forward for the development of a transdermal drug delivery system.

Improving reinforcement of natural rubber latex by introducing poly‐zinc dimethacrylate and sulfur vulcanizing system

AbstractIn this work, zinc dimethacrylate (ZDMA) was employed to reinforce natural rubber latex (NRL) and a new process was introduced. Polymethacrylic acid was prepared by emulsion polymerization of methacrylic acid (MAA), then mixed with ZnO in a different mole ratio (ZnO/MAA) and the mixture was noted as PZDMA. It was added to NRL and a traditional sulfur vulcanizing system was adopted simultaneously. The mechanical test results show that compared with the sample “NR,” the tensile and tear strength are significantly improved by the addition of PZDMA. When 7 phr ZnO (NR‐7A) are loaded, it can reach 25.1 MPa and 62.8 N/mm, which are higher than “NR” by 52.0% and 104.6%, respectively. While the strength of the NRL film reinforced only with PZDMA is quite limited. Detailed analysis by Fourier‐transforms infrared spectroscopy, X‐ray diffractometers, scanning electron microscopy, thermogravimetric, and dynamic mechanical analysis revealed that PZDMA is successfully formed and dispersed uniformly in NRL, PZDMA acts as a nanoparticle and ionic cross‐linking agent, and the covalent cross‐linking network is formed by a sulfur vulcanizing agent. The dual cross‐linking network shows a synergistic effect on the reinforcement of NRL. The present work provides a process to reinforce NRL with adjustable mechanical properties.

Guayule Natural Rubber Latex and Bi2O3 Films for X-ray Attenuating Medical Gloves

Existing natural latex radiation-attenuating gloves (RAGs) contain a high loading of radiation attenuation filler that reduces their mechanical properties to below Food and Drug Administration (FDA) medical glove requirements. RAGs are commonly formulated using Hevea natural rubber latex and lead-based fillers. The former can cause life-threatening allergic responses and the latter are known for their toxicity. In this work, a new lead-free RAG formulation based on circumallergenic guayule natural rubber latex (GNRL) and non-toxic radiation attenuation filler bismuth trioxide (Bi2O3) was developed. GNRL films with Bi2O3 loadings ranging from 0 to 300 PHR at different thicknesses were prepared. Radiation attenuation efficiencies (AE) at 60, 80, 100, and 120 kVp were determined and attenuation isocontour curves predicted film thickness and Bi2O3 loading required to meet or exceed the radiation attenuation requirements of ASTM D7866 and commercial RAGs. Optimal curing conditions for GNRL/Bi2O3 films with 150 PHR Bi2O3 were investigated by varying curing temperatures and time from 87 °C to 96 °C and 65 min to 90 min, respectively. In general, as the loading of the filler increased, the density of the films increased while the thickness decreased. GNRL/Bi2O3 films with 150 PHR Bi2O3 and 0.27 mm provided 5% more AE than RAG market average attenuation at the same thickness. The films with 150 PHR Bi2O3 cured under near-optimal conditions (90 °C/85 min, and 87 °C/65 min) met both the radiation attenuation standard (ASTM D7866) and the natural latex surgeon and examination glove standards (ASTM D3577 and D3578, respectively). Thus, gloves made using our formulations and protocols demonstrated potential to meet and surpass medical natural latex glove standards, offer a single product for both infection control and radiation protection instead of double-gloving, provide a greater degree of comfort to the user, and simultaneously reduce contact reactions and eliminate potential latex allergic reaction.

Antibacterial natural rubber latex films with surface-anchored quaternary poly(4-vinylpyridine) polyelectrolyte

Device-associated biofilms and infections generated thereby are of important concern in healthcare sector wherein efficacious antimicrobial surfaces are of extreme relevance. Natural Rubber is widely used for diverse biomedical applications; however, is inherently inactive against most of the pathogens. A facile and effective approach is presented herein to transform Natural Rubber latex (NRL) film surfaces into sufficiently antibacterial via surface conjugation of a cationic polyelectrolyte, quaternized Poly(4-vinylpyridine), QP4-VP through amide linkage using Chloroacetic acid. 1H NMR, FT-IR, TGA and zeta potential measurements affirmed quaternization and functionalities of QP4-VP while antibacterial efficacy is certified by significant zones of inhibition against standard strains, Escherichia coli and Staphylococcus aureus using Ciprofloxacin as positive control. Chloroacetic acid reacts with –OH group of surface-oxidized NRL establishing ester linkage which facilitates anchoring of QP4-VP onto NRL film surface through amide linkage; authenticated by ATR spectra and contact angle measurements. Accelerated leaching (50 °C for 4 days) demonstrated minimal weight loss for the conjugated films and assuring stability of the conjugate. Contact killing assay results indicated significant bacterial killing rate (99.99%) against the tested clinical strains; P. aeruginosa PAO1 and Acinetobacter baumannii C80 validate the antibacterial efficacy of the films.

Antimicrobial natural rubber (NR) latex films for stethoscope diaphragm cover application

A stethoscope diaphragm without regular disinfection could be a potential vector for cross-transmission of healthcare-associated infections. Therefore, an antimicrobial latex film could be used as a cover to inhibit the growth of pathogenic microorganisms on its surface. This research was conducted to investigate the antimicrobial activity and mechanical properties of antimicrobial natural rubber (NR) latex films with the addition of different types of antimicrobial agents (mangosteen peel powder (MPP), zinc oxide nanoparticles (ZnO NP), povidone-iodine (PVP-I)) with loading 2.0 phr. The addition of antimicrobial agents showed an optimal inhibition against the growth of Gram negative bacteria and fungi. They exhibited good antimicrobial efficacy with the largest zone of inhibition for MPP and PVP-I antimicrobial agents. The mechanical properties of the NR latex films with antimicrobial agents were still on par with the unfilled NR latex films. There was no significant drop in mechanical properties after adding the antimicrobial agents. In summary, the addition of antimicrobial agents, mainly ZnO NP can be a better choice for NR latex films as it will have dual functions as an activator and antimicrobial properties.

Preparation and characterization of self-healing natural rubber latex film

The objective of this study was to prepare and characterize the self-healing natural rubber latex films with different zinc thiolate (ZT) content. In this work, ZT was introduced into high ammonia natural rubber latex (HANRL) through a peroxide vulcanization system at different ZT content (0, 15, 30, 45 phr). The self-healing strategy is based on reversible ionic interaction between Zn2+ ion and S- ion in ZT cross-linker. Evidence for the presence of reversible ZT ionic networks was provided by Fourier-transform infrared spectroscopy (FTIR) analysis. The results revealed that HNRL/DCP/30ZT able to recover its initial properties after the broken sample was brought in contact with each other. The healing efficiency for tensile strength, elongation at break and tear strength were obtained at 93.77%, 98.77% and 89.50%, respectively.

Deodorizing effects of sepiolite on odorous volatile organic compounds of natural rubber latex films

AbstractThis study reports the efficiency of sepiolite in reducing odorous volatile organic compounds (VOCs) from natural rubber. Natural rubber latex (NRL) films with various content of sepiolite were prepared, ranging from 0 to 2.0 parts per hundred rubbers. The presence of odous VOCs in neat NRL films and NRL/sepiolite films has been confirmed by using gas chromatography‐mass spectrometry. Most of odorous VOCs with odor detection threshold (ODT) of less than 0.1 ppm were significantly reduced in the presence of sepiolite. The result of dynamic olfactometry analysis also shows a negative correlation between odor concentration and the sepiolite content. The addition of 2.0 phr sepiolite in NRL/sepiolite‐T and NRL/sepiolite‐C reduced the odor concentration of NRL films by 69.1% and 59.4%, respectively. This proves that the mesoporous sepiolite‐T adsorbed more odorous VOCs in the NRL films, as compared to macroporous sepiolite‐C. Thus sepiolite‐T is a promising deodoriz er for NRL films due to its higher odorous VOCs adsorption potentials.

Improving the Hydrophilic Properties of Deproteinized Natural Rubber Latex Films for Lidocaine Transdermal Patches by Starch Blending

Improving the Hydrophilic Properties of Deproteinized Natural Rubber Latex Films for Lidocaine Transdermal Patches by Starch Blending

Optimisation of Tensile Strength and Weight Loss via Taguchi and Response Surface Method for Natural Rubber Latex Film Consisting Cassava Peel as a Bio-Based Filler

Disposal latex and synthetic rubber gloves is troublesome such that disposal via incineration and land fill may release poisonous gasses and contaminate soil and water, respectively. As solution to latex and synthetic rubber, biodegradable glove is extensively studied. A bio-based filler is extracted from food waste and blended into natural rubber latex (NRL) as a composite NRL. The effect of biodegradability of composite NRL was studied by varying the loading of bio-based filler in a form of starch dispersion and blended into NRL mixture. Herein some amount of starch can be extracted from cassava peel to be incorporated in NRL for a sustainable and yet biodegradable glove. Previous work on incorporation of cassava-peel filler in NRL has shown a biodegradability without compromising the pristine strength of NRL film at 50% loading starch. In this project, tensile strength and weight loss of prepared composite NRL films were optimised via Taguchi and Response Surface Method (RSM) by means of Design Expert software by varying starch/filler loading, curing temperature and curing drying duration. Due to inadequate data, the optimisation from that previous prepared composite NRL was compared with similar work which utilising NRL and bio-based filler. For Pulungan (2020) study, it can be concluded that the tensile strength of cassava peel starch biodegradable film has the best condition at 50°C to 60°C at approximately 5.5 hours. Elongation optimum conditions shows contrast value of temperature and time. Meanwhile, for Wendy (2020) study, it shows the best percentage loading of cassava-peel starch is at 20% to achieve high stress and strain at break. The optimised mechanical properties via Taguchi and RSM are rather different and hence validation on mechanical properties at above mentioned conditions need to be performed experimentally.

Effects of Sm3+/PMAA on mechanical and thermal properties of natural rubber latex film

AbstractSamarium carbonate [Sm2(CO3)3] was taken as the source of Sm3+, and methyl acrylic acid (MAA) was employed as the precursor to prepare polymethacrylic acid (PMAA). The mixture of Sm2(CO3)3 and PMAA was marked as “SmP.” The SmP prepared under different conditions was added to natural rubber (NR) latex to prepare NR/SmP films. The influence of the polymerization temperature of MAA and the amount of SmP on the mechanical properties and structure of NR/SmP films were analyzed. The results show that polymerization temperature has significant effect on the mechanical properties of NR/SmP film; lower temperature is benefit to improve modulus and rigidity, whereas higher temperature helps maintain good elasticity. Compared with neat NR, addition of 5‐phr Sm2(CO3)3 results in a 30%–37% increase of tensile strength. Furthermore, the glass transition temperature (Tg) can also be increased by the addition of SmP; and the tan δ curves of all samples exhibit only one transition peak and indicate no phase separation between SmP and NR matrix. The influence of SmP on the structure and morphology of NR was explored by Fourier transform infrared, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy analysis; and the results show that SmP can be dispersed uniformly in the NR latex when loading of Sm2(CO3)3 is lower than 20 phr.

Effect of Maillard reaction in ammonia preserved natural rubber latex using reducing sugars

Investigation of Maillard reaction in natural rubber (NR) latex was carried out using two reducing sugars, glucose and ribose. Both reducing sugars together with a 1:1 mixture were added as 5 wt% solution to concentrated NR latex preserved with ammonia in a 1:1 ratio and preheated at 27, 70 and 90 °C for 2 h. The changes in the latex due to the reaction were characterised using pH and L values for 216 h (9 days). Cast latex films were then prepared and investigated for their swelling index (SI), gel content and tensile properties. Results obtained showed reduction in both pH and L values with time for the latexes with reducing sugars indicating progress of the Maillard reaction. For the Maillard reacted films, SI reduced whereas gel content, tensile stress and tensile strength increased. However, no significant changes were observed for the elongation at break of the reacted samples compared to the unreacted samples. Increasing the preheating temperature of the latex and reducing sugar mixtures to 70 and 90 °C from 27 °C increased the Maillard reaction which further improved the film properties. Although both reducing sugars improved the film properties, the improvements brought by reacting NR latex with ribose were more significant compared to reacting NR latex with glucose. From the current findings, it is evident that reducing sugars could be used to enhance the physical properties of natural rubber latex films. This technique will benefit the latex industry as it is environmentally friendly, easily applicable and cheaper compared to currently available techniques.

Enhancement of hydrophobicity of natural rubber latex films using diatomaceous earth

ABSTRACTEnhancement of the hydrophobic nature of natural rubber latex (NRL) films will open up a wide range of applications for them. Incorporating hexadecyltrimethoxysilane treated superhydrophobic diatomaceous earth (DE) in NRL, resulted in films with increased hydrophobicity. The nano‐scale surface roughness for the superhydrophobic surface was provided by DE and low surface energy was achieved by treating DE with hexadecyltrimethoxysilane (treated DE). Surface wettability and morphology were analyzed by water contact angle (WCA) measurements and scanning electron microscopic analysis, respectively. About 38% wt/wt hexadecyltrimethoxysilane to DE ratio could make superhydrophobic DE with WCAs larger than 150°. A dispersion of treated DE was incorporated into NRL resulting in hydrophobic NRL films possessing WCAs greater than 110° with 41% treated DE particle loading. The resulting NRL films were harder and had smaller tensile strength compared to normal NRL film.

Mechanical Strength Improvement of Cement-Stabilized Soil Using Natural Rubber Latex for Pavement Base Applications

Thailand is an agricultural country, ranked as the top in the world for the production and export of natural rubber. This study investigated the influence of natural rubber latex (NRL) replacement on the mechanical strength improvement of cement-stabilized soil. Cement contents of 3%, 5%, and 7% by weight of dry soil and NRL replacement ratios of 10%, 15%, 20%, 25%, and 30% by weight of compacting water were used in this research study. The mechanical strengths were investigated via unconfined compressive strength (UCS) and flexural strength (FS) tests. The mechanical strengths improvements were examined through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses. NRL replacement was found to significantly enhance the mechanical strengths of cement-NRL stabilized soil. The optimum NRL replacement ratios providing the highest density, compression, and flexural strengths were found at 20%, 15%, and 10% for 3%, 5%, and 7% cement contents, respectively. At the optimum NRL replacement ratio, the UCS was improved up to 30%, 21%, and 18% for 3%, 5%, and 7% cement contents. While, FS was improved up to 78%, 40%, and 29% for 3%, 5%, and 7% cement contents. Even though the NRL films within the soil-cement matrix improved the cohesion of the soil matrix, it was found to retard cementation bonding. As such, the excessive NRL replacement not only reduced the compactability but also retarded the cement hydration and, hence, the strength reduction. The outcome of this research will promote the usage of NRL as a sustainable alternative to imported synthetic latexes for improving the mechanical strength of cement-stabilized soil for pavement bases.

Effect of filler on the total protein content and mechanical properties of natural rubber latex films at different filler loadings

Calcium carbonate (CaCO3) is an important filler, widely used rubber industries, particularly in natural rubber latex dipped such as gloves. The main advantages are cost reduction and product improvement. With the development of technology in superfine filler production, the use of CaCO3 as a non-reinforcing filler has gained much attention as it could help to improve natural rubber (NR) product properties. In this study, mixed clones of natural rubber field latex (MCFL) were prepared before further processing into mixed clones’ natural rubber latex concentrate (MCLC). The properties of MCLC were evaluated before compounds with CaCO3 and other rubber chemicals. The MCLC films were prepared from the MCLC added with CaCO3 varied from 10 to 40 parts per hundred rubber (pphr) and rubber chemicals. The total protein contents for unaged and aged latex films before and after acetone extraction was determined, respectively, according to total nitrogen (N) and extractable protein (EP) contents. The content of CaCO3 in MCLC films at different loadings was characterised by a Thermogravimetric analyser (TGA). Meanwhile, mechanical properties such as tensile and tear strengths were also determined. It was found that the total protein contents for the unaged MCLC films at different filler loadings were higher as compared to the aged samples. It is also proposed that the chemicals’ interference for MCLC films have occurred from 25 pphr until 40 pphr filler loadings. The tensile strength of MCLC films decreased as the filler loading increased. However, the tear strength of MCLC films increased as the filler loading increased.