Natural Rubber Films Research Articles

Application of Low Cost Natural Rubber Films for Water Remediation

Application of Low Cost Natural Rubber Films for Water Remediation

Dielectric response of vulcanized natural rubber containing BaTiO3 filler: The role of particle functionalization

Natural rubber (NR) nanocomposites have been prepared with hydroxylated barium titanate filler (BaTiO3-OH), employing emulsion polymerization followed by vulcanization process. The addition of barium titanate, a compound with high dielectric permittivity, was envisaged to increase the insulating properties of NR films, thereby reducing the electrical stress and the possibility of undesired arcing on their surfaces. The content of perovskite particles greatly affected both, the mechanical and the electrical properties, of the vulcanized films. It was observed that the optimum functionalized nanoparticle concentration is around 0.25–0.50 phr, range in which the elongation of break was maintained between 874–935% and the tensile strength was between 4.40–4.80 MPa; whereas the dielectric permittivity (ɛ′) is slightly lower than the pristine NR or the NR compounded with high content of BaTiO3 nanoparticles. The dielectric study revealed the presence of two dielectric relaxation modes: (i) glass to rubber transition (α-relaxation) and (ii) interfacial polarization (IP), known as Maxwell−Wagner−Sillars (MWS) polarization. The comparison between small concentrations of non-functionalized and functionalized BaTiO3 inside NR polymeric films lead to the conclusion that the dielectric breakdown strength is high for non-functionalized fillers, supposedly due to less IP polarization phenomena.

Sulfur-Free Prevulcanization of Natural Rubber Latex by Ultraviolet Irradiation in the Presence of Diacrylates

Natural rubber (NR) latex was prevulcanized by ultraviolet (UV) irradiation in the presence of different diacrylate coagents. Prevulcanization was affected by the aliphatic hydrocarbon chain length of the coagents. The following diacrylate coagents with increasing aliphatic hydrophobic chain lengths were used: 1,4-butanediol diacrylate (BTDA), 1,6-hexanediol diacrylate (HDDA), and 1,9-nonanediol diacrylate (NDDA). Oxygen inhibition of the free-radical reactions of prevulcanization and the effects of the inert CaCO3 filler (concentration range = 0–40 parts per hundred rubber) on properties of the prevulcanized NR films were investigated. The hydrocarbon chain length of the coagent influenced its hydrophobicity and therefore its affinity toward NR, and this affected the prevulcanization outcomes. HDDA showed the greatest affinity for NR and thus was the most suitable coagent for prevulcanization of NR. Prevulcanization via UV irradiation was insensitive to oxygen and the filler tested. The CaCO3 filler prov...

Sericin-binded-deprotenized natural rubber film containing chitin whiskers as elasto-gel dressing

Here, we aims to demonstrate a simple concept in biomaterials design by using natural resources solely as raw materials to fabricate elastic wound care dressing. Elasto-gel films comprise of silk sericin (SRC), natural rubber (NR), and chitin whisker (CTW) were developed. A glue-like protein SRC found in silk cocoons is beneficial for the treatment of wounds due to its superior skin moisturizing ability. However, the pure SRC film is generally difficult to be fabricated because of its weak structural feature. This limitation was overcome by using NR as a binder which consecutively rendered elasticity and strength of the films. CTW was chosen as another component to promote ability of the films for tissue restoration. Before the film formation, protein in the natural rubber latex (NRL) was removed to avoid allergic and cytotoxic problems. The enzyme-treated NR/SRC (ETNR/SRC) films having different blend compositions were fabricated by solution casting technique. The highest amount of the SRC to gain an easy to handle ETNR/SRC film was 30%. The ETNR/SRC/CTW films having 20% SRC were fabricated and studied in comparison. Essential properties of the films as elastic wound care dressings were investigated and effect of the materials chemistry on the observed properties were discussed.

Understanding the strain-dependent dielectric behavior of carbon black reinforced natural rubber – An interfacial or bulk phenomenon?

Filler-polymer interactions are one of the keys to understanding the physical properties of polymer composites. These interactions give rise to an interface with specific properties that may have a nontrivial effect on the macroscopic properties of composites. Direct measurement of the interface properties at nanometer scale is usually unavailable. Thus, interface properties are often back calculated from the bulk response using a computational model. However, if the model does not take into account the morphology of the filler dispersion, the results can be misleading. Recently it has been found that the dielectric response of a carbon black filled natural rubber film can change dramatically upon stretching [M. Huang, Macromolecules49, 2339 (2016)]. In this paper, we will show that this phenomenon can be largely explained by changes in filler cluster connectivity due to strain and is probably not caused by changes in the interfacial interactions. To support the argument, the polarization mechanism of the composites in the measured frequency range is analyzed and numerical models are developed to virtually reproduce the physical phenomenon as a function of strain. A power-law dependence of dielectric permittivity with strain is derived, which matches closely with the experimental results.

Reinforcement of Natural Rubber with Bacterial Cellulose via a Latex Aqueous Microdispersion Process

Natural rubber (NR) composites were reinforced with bacterial cellulose (BC) to improve mechanical and physical properties. The natural rubber bacterial cellulose (NRBC) composite films were prepared via a latex aqueous microdispersion process by a thorough mixing of BC slurry with natural rubber latex (NRL). The structural morphology and chemical and physical properties of NRBC composites were investigated. The hydrophilicity, opacity, and crystallinity of the NRBC composites were significantly enhanced because of the added BC. By loading BC at 80 wt.%, the mechanical properties, such as Young’s modulus and tensile strength, were 4,128.4 MPa and 75.1 MPa, respectively, which were approximately 2,580 times and 94 times those of pure NR films, respectively, whereas the elongation at break of was decreased to 0.04 of that of the NR film. Because of its high mechanical strength and thermal stability, the NRBC composites have potential uses as high mechanical strength rubber-based products and bioelastic packaging in many applications.

Gentamicin sulfate-loaded porous natural rubber films for wound dressing

Antimicrobial wound dressings have been developed for effectiveness of wound therapy. In this study, gentamicin sulfate was loaded into modified porous natural rubber films. The hydrophilic porous structure in natural rubber films was formed when the polar liquid such as glycerin or triethyl citrate and hydrophilic xanthan gum were blended. Film properties including morphology, drug release, water sorption and erosion, mechanical property, adhesive property, surface free energy, water vapor transmission rate, oxygen permeation, and antimicrobial activity were determined. The angiogenesis activity of films was investigated using chick chorio-allantoic membrane assay. For the system containing triethyl citrate, bi-layers comprising of a dense-top layer and a high porous-bottom layer were observed. Xanthan gum enhanced the water sorption capacity and modified to obtain the optimum rate of the drug release from the film. The developed film topography with dense-top layer induced the low adhesive property, water vapor and oxygen permeability whereas demonstrated good antimicrobial activities against Staphylococcus aureus and Pseudomonas aeruginosa with angiogenic activity. Therefore it had the potential use for medicated wound dressing.

Silver Nanoparticles Embedded in Natural Rubber Films: Synthesis, Characterization, and Evaluation ofIn VitroToxicity

Natural rubber (NR) films can reduce silver metal ions forming embedded metal nanoparticles, a process that could be described as green synthesis. The NR films acting as a reactor generate and incorporate silver nanoparticles (AgNPs). Organic acids and amino acids play a crucial role in the formation of AgNPs. The plasmon extinction obtained in the UV-visible spectrum shows the presence of nanoparticles in the film after dipping the NR film into a solution of silver nitrate at 80°C. Electron microscopic analysis confirms the presence of AgNPs in the NR film and characterization by atomic force microscopy shows a change in the roughness of the NR film with AgNPs. In addition, our preliminary results fromin vitrotoxicity studies (MTT and comet assays) of the NR films and NR films with silver nanoparticles (NR/Ag) show that they are not toxic to cell lineage CHO-K1 (cells from the ovary of a Chinese hamster), an important result for potential medical applications.

The Occurrence of Phase Separation in Microcrystalline Cellulose Filled Natural Rubber Films

This paper describes the use of microcrystalline cellulose (MCC) as hydrophilic filler in two types of natural rubber latexes which are high ammonia natural rubber (HA) and epoxidised natural rubber latex (ENR). Light microscopy (LM), Scanning electron microscopy (SEM) and tensile strength measurements were then conducted on the resulting films. The light microscopy analysis revealed that more MCC particles appeared at the air–facing (AF) surfaces relative to the substrate-facing (SF) surfaces of the HA films with increasing MCC content. In contrary, the ENR25 films showed more or less similar MCC particles appearing at both air-facing surfaces and substrate-facing surfaces. Further SEM cryo-fracture analysis at the cross sections of the MCC filled ENR25 films indicated that the MCC particles were randomly dispersed in the rubber matrix. It can be suggested that the phase separation of MCC particles to the films surfaces occurred due to the incompatibility of MCC with the rubber matrix. Thus, it can be inferred that the occurrence of phase separation is minimised in the MCC filled ENR films in comparison to the MCC filled HA films.

Preparation and Properties of Biocomposite Based on Natural Rubber and Bagasse Nanocellulose

Biocomposite based on natural rubber (NR) and bagasse nanocellulose (BNC) was prepared in latex state. The mechanical, morphological and thermal properties of NR/BNC biocomposite were investigated. It was found that the addition of 3 wt% of BNC in NR film caused significant increase in modulus at 100% and 300% elongations and improved thermal stability of NR/BNC biocomposite. However, the strength at break and elongation at break of the biocomposite were not enhanced correlating to the morphological result obtained from scanning electron microscope (SEM).

Novel nonammonia preservative for concentrated natural rubber latex

ABSTRACTA derivative of sym‐triazine (HTT) was chosen as a new nonammonia preservative for concentrated natural rubber latex (CNRL) in place of NH3–TT/zinc oxide (ZnO). The preservation effects of the HTT for CNRL, drying characteristics, mechanical properties, and cytotoxicity of the vulcanized natural rubber (NR) film were investigated. The results show that the CNRL was preserved steadily for more than 6 months with 0.3% HTT, and the volatile fatty acid number, viscosity, and mechanical stability of CNRL all met the requirements of ISO 2004:2010(E). The drying characteristics of the vulcanized NR film preserved by HTT retained no change compared with those of the film preserved by NH3–TT/ZnO. The tensile strength and elongation at break of the vulcanized NR film preserved by HTT were 32.17 MPa and 853.80%, respectively; these were very similar to those of the film preserved by NH3–TT/ZnO, whereas the tear strength reached 68.43 kN/m, and this was much higher than that by NH3–TT/ZnO. The results of the cytotoxicity and dermal irritation tests prove that HTT is not especially harmful to humans. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41749.

Toughening mystery of natural rubber deciphered by double network incorporating hierarchical structures.

As an indispensible material for modern society, natural rubber possesses peerless mechanical properties such as strength and toughness over its artificial analogues, which remains a mystery. Intensive experimental and theoretical investigations have revealed the self-enhancement of natural rubber due to strain-induced crystallization. However a rigorous model on the self-enhancement, elucidating natural rubber's extraordinary mechanical properties, is obscured by deficient understanding of the local hierarchical structure under strain. With spatially resolved synchrotron radiation micro-beam scanning X-ray diffraction we discover weak oscillation in distributions of strain-induced crystallinity around crack tip for stretched natural rubber film, demonstrating a soft-hard double network structure. The fracture energy enhancement factor obtained by utilizing the double network model indicates an enhancement of toughness by 3 orders. It's proposed that upon stretching spontaneously developed double network structures integrating hierarchy at multi length-scale in natural rubber play an essential role in its remarkable mechanical performance.

Determination of the viscoelastic interfacial properties between silica and SNR-based materials via a semi-empirical approach

The properties of the surface and rubber–filler interface of a rubber-based material may be different from those of the bulk. The time-dependent relaxation modulus and creep compliance function of surface can be obtained through an indentation test involving the influences of both localized creep and surface adhesion. This paper reports an approach to obtain localized surface and interfacial properties for synthetic natural rubber (SNR) films by means of a newly developed semi-empirical method. The rubber–silica interface is simulated by rubber indented by a silica tip. The SNR films with several different crosslink densities were prepared utilizing the solution casting method. Indentation tests were performed following a step loading-holding and a ramp loading-holding–unloading procedure. Fused silica balls of 500μm radius were used as tips in the experiments. The indentation time, penetration depth, and applied load data were recorded during each test. The localized creep compliance and work of adhesion between the tip material and the rubber surface were obtained, using the semi-empirical method, from the experimental data. The results show an inverse relationship between the crosslinking density of the SNR and the creep compliance. The same trend is also found in the work of adhesion, which is defined based on the Dugdale cohesive zone model for describing the interface between the silica tip and the SNR sample surface.

Electrical, mechanical, and thermal analysis of natural rubber/polyaniline-Dbsa composite

A composite of natural rubber (NR) with polyaniline (PANI) was obtained by mixing an aqueous dispersion of dodecylbenzenesulfonic acid (DBSA)-doped PANI with NR latex in different concentrations. Films were obtained by the casting method and characterized by ultraviolet visible near-infrared (UV-Vis-NIR) spectroscopy, thermogravimetry/differential thermogravimetry (TG/ DTG), stress-strain testing, differential scanning calorimetry (DSC), and DC electrical conductivity measurements. The UV-vis-NIR spectrum showed that PANI remained doped in the composite, and this improved the mechanical and electrical proprieties of NR films and afforded them good thermal stability up to ~200°C. The percolation threshold did not follow the universal critical exponent, and in this case, conduction preferentially occurs by hopping and tunneling.

PMMA-N,N,N-trimethyl chitosan nanoparticles for fabrication of antibacterial natural rubber latex gloves

This paper presents one-pot synthesis of N,N,N-trimethyl chitosan (TMC) stabilized poly(methyl methacrylate) (PMMA) latex particles via the miniemulsion polymerization technique. From 1H NMR, synthesized TMC contains 52% degree of quaternization. Compared to native biopolymer chitosan, TMC possesses permanently positive charges as well as provides greater antibacterial activity. Combining properties of PMMA and TMC, PMMA–TMC latex nanoparticles (hydrodynamic size ≈282nm) could be used in place of inorganic lubricating powder in fabrication of latex gloves at pH ≥7. After immersing sulphur prevulcanized natural rubber (SPNR) film into 3wt% of PMMA–TMC latex at pH 7, significant amount of nanoparticles uniformly deposited onto SPNR film was observed under SEM. A number of nanoparticles present on film surface would increase surface roughness of the rubber film and potentially inhibit the bacterial (Escherichia coli and Staphylococcus aureus) growth, which would be useful for fabrication of special gloves with antibacterial property.

Surface Modification of Natural Rubber Film with PMMA Nanoparticles Stabilized by Chitosan or its Derivative

Poly(methyl methacrylate) (PMMA) latex particles stabilized by chitosan (CS) or N,N,N-trimethylated chitosan (TMC) (50% degree of quaternization) were prepared via the miniemulsion polymerization. The spherical PMMA-CS nanoparticles (342 nm) were then deposited onto sulphur-prevulcanized natural rubber (SPNR) film via the Layer-by-Layer (LbL) technique. The aims were to reduce the surface friction of rubber film and to avoid the direct contact between SPNR and human skin which might cause the allergic problem for some hypersensitive users. Results confirmed the presence of PMMA-CS particles which caused an increase in the surface roughness of SPNR from 46 to 57. However, the PMMA-CS did not exhibit the antimicrobial activity. Therefore, the antimicrobial activity against E.coli and S.aureus of the SPNR film coated with PMMA-TMC particles is investigated.

Cast Natural Rubber Films Comprising Triethyl Citrate

The various triethyl citrate-loaded natural rubber (NR) films were prepared by casting technique employing dichloromethane (DCM) as solvent. The wettability, mechanical properties and topology of prepared dry films were determined. The contact angle of distilled water onto the cast films was measured using the goniometer. Triethyl citrate-loaded NR films exhibited the continuous porous structure. The presence of triethyl citrate in NR films promoted wettability and surface free energy whereas the tensile strength decreased. The unique porous topography of triethyl citrate-loaded NR film exhibited the potential for applying this material as the scaffold or controlled drug delivery devices in the future.

Highly Glycerin-Loaded Natural Rubber Films Prepared by Casting Technique Using Different Solvents

The highly glycerin-loaded natural rubber (NR) films were fabricated by casting technique with different solvents including dichloromethane (DCM), diethyl ether and tetrahydrofuran (THF) with an addition of 75 phr glycerin. Their mechanical properties, wettability and topography were determined. The highly glycerin-loaded NR films exhibited the continuous porous structure which their tensile strength values decreased whereas their wettability was enhanced. Pore size of the glycerin-loaded NR films prepared by using DCM as a solvent was greatly larger than those of the systems prepared by using diethyl ether and THF, respectively. Some active compounds might be loaded into these modified porous structures of NR films and applied for controlled drug delivery systems.

Modulation of Drug Release from Natural Rubber Coated Capsule Loaded with Sodium Bicarbonate and Camphor

Natural rubber (NR) has the distinguished film forming and hydrophobic properties. If it could be reformed by an addition of some pore forming agents, the porous topography of this produced material would be interesting for applying in controlled release system. The purpose of this study is to investigate on characterization of film coat and release of propranolol hydrochloride (P) from capsules coated with NR latex. The experimental methods involved the preparation of NR film which was optimally prepared by dipping technique followed by drying onto hard gelatin capsule. The drug release was determined for coated systems fabricated with two different techniques (the dissolving of sodium bicarbonate and the sublimation of ammonium carbonate or camphor). It indicated that ammonium carbonate was incompatible with NR latex. The extent of overall in vitro release of P into HCl buffer pH 1.2 from plain NR film coated capsule at 8 h was approximately 1%. However, the decrease concentration of NR latex or addition of sodium bicarbonate or camphor could enhance the extent of drug release. Scanning electron microscopy (SEM) exhibited the micro porous nature for systems loaded with sodium bicarbonate or camphor. Therefore the hydrophobic nature of NR was proper for sustainable drug release which an incorporation of some poring agent could modulate the release of active compounds.

Pore Formation of Natural Rubber Film Comprising Different Liquids

Typical natural rubber (NR) foam could be produced by an addition of some blowing agents in dry NR. The porous topography of this produced material is interesting for applying in field of pharmaceutical science and related. For this study, the porous natural rubber structure was attempted to be fabricated by casting technique. The addition of various grades of polyethylene glycol into NR solution was performed before casting however there was no apparent pore formation. Olive oil and distilled water could not induce the pore formation whereas propylene glycol, triethyl citrate and NMP addition exhibited the ability to induce the pore formation in NR matrix film. This obtained structure will be tested and used as controlled drug delivery.