Rubber Films Research Articles

Nano-micro structured superhydrophobic zinc coating on steel for prevention of corrosion and ice adhesion

Thin films of zinc have been deposited on steel substrates by electrodeposition process and further functionalized with ultra-thin films of commercial silicone rubber, in order to obtain superhydrophobic properties. Morphological feature, by scanning electron microscope (SEM), shows that the electrodeposited zinc films are composed of micro-nano rough patterns. Furthermore, chemical compositions of these films have been analyzed by X-ray diffraction (XRD) and infra-red (IRRAS). An optimum electrodeposition condition, based on electrical potential and deposition time, has been obtained which provides superhydrophobic properties with a water contact angle of 155±1°. The corrosion resistance properties, in artificial seawater, of the superhydrophobic zinc coated steel are found to be superior to bare steel. Similarly, the measured ice adhesion strength on superhydrophobic surfaces, using the centrifugal adhesion test (CAT), is found to be 6.3 times lower as compared to bare steel. This coating has promising applications in offshore environment, to mitigate corrosion and reduce ice adhesion.

Radiation-grafting of acrylamide onto silicone rubber films for diclofenac delivery

Abstract This work focuses on the pre-irradiation grafting of acrylamide (AAm) onto silicone rubber films (SR) and evaluates the effect of gamma-ray radiation conditions on the grafting yield, which in turn may influence the performance of the grafted materials as components of drug-eluting devices. Pristine and modified SR were characterized using FTIR-ATR, DSC, TGA, swelling, and water contact angle analysis in order to elucidate the effects of AAm grafting onto SR. Grafted films with content in AAm ranging from 0.81% to 22.20% showed excellent cytocompatibility against fibroblasts, and capability to uptake the anti-inflammatory drug diclofenac. Amount of drug loaded directly correlated with the grafting degree of the films. Drug release studies were performed at pH 7.4 and 37 °C (physiological conditions). Most grafted films released the drug in a sustained way for at least three hours.

Transparent and robust siloxane-based hybrid lamella film as a water vapor barrier coating.

Water vapor barriers are important in various application fields, such as food packaging and sealants in electronic devices. Polymer/clay composites are well-studied water vapor barrier materials, but their transparency and mechanical strength degrade with increasing clay loading. Herein, we demonstrate films with good water vapor barrier properties, high transparency, and mechanical/thermal stability. Water vapor barrier films were prepared by the solution crystallization of siloxane hybrid lamellae. The films consist of highly crystallized organic/inorganic hybrid lamellae, which provide high transparency, hardness, and thermal stability and inhibit the permeation of water vapor. The water permeability of a 6 μm thick hybrid film is comparable to that of a 200 μm thick silicon rubber film.

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.

Modification of unsaturated rubbers in low-temperature plasma as a method to improve their adhesion properties

The change in the contact-surface properties of the films of unsaturated rubbers under the effect of a direct-current discharge has been investigated in case of the placement of the samples at the anode. It has been demonstrated that the modification in plasma leads to a substantial improvement in the contact properties of rubber films.

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.

Role of Divalent Metals in Polymer Degradation

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

Radiation-grafting of thermo- and pH-responsive poly(N-vinylcaprolactam-co-acrylic acid) onto silicone rubber and polypropylene films for biomedical purposes

This work focuses on the effects of gamma-ray irradiation conditions on the stimuli-responsiveness of polypropylene (PP) films and silicone (SR) rubber substrates grafted with N-vinylcaprolactam (NVCL) and acrylic acid (AAc). PP films and SR rubber were modified by simultaneous polymerization and grafting of NVCL and AAc, using pre-irradiation oxidative method at a dose rate of 12.23kGyh−1 and doses ranging from 5 to 70kGy. NVCL and AAc solutions (1/1, v/v) at 50% monomer concentration (v/v) in toluene were added to the sample substrates, degassed, sealed and heated at 60 and 70°C for 12h. After grafting, the samples were soaked in ethanol and distilled water for 24h successively, followed by drying under vacuum. Samples were characterized by FTIR-ATR, DSC and swelling measurements. Critical points (pH critical or LCST) of grafts were obtained in a pH-environment (pH ranges from 2.2 to 9) and in a thermo-environment (temperature ranges from 22 to 50°C). Cytotoxicity evaluation was performed using fibroblast BALB/c 3T3 cells. The relationship between NVCL-co-AAc grafting and radiation dose was different for each substrate, PP and SR. At 50% NVCL/AAc concentration in toluene, grafting values were higher for SR than for PP. Despite the fact that PP-g-(NVCL-co-AAc) membrane presented a cytotoxic profile at the highest experimental concentration assayed, cytotoxicity evaluation revealed noncytotoxic profiles for the membranes synthesized highlighting their applications for biomedical purposes.

Three-dimensional modeling of chloroprene rubber surface topography upon composition

In this study the effect of polymer blend composition on the surface roughness has been investigated and simulated. Three-dimensional modeling of chloroprene rubber film surface upon piperylene-styrene copolymer content was conducted. The efficiency of various surface roughness modeling methods, including Monte Carlo, surface growth and proposed method, named as parabolas, were compared. The required parameters for modeling were obtained from atomic force microscopy topographical images of polymer films surface. It was shown that experimental and modeled surfaces have the same correlation function. The quantitative comparison of function parameters was made. It was determined that novel parabolas method is suitable for three-dimensional polymer blends surface roughness description.

Erasable and Reversible Wrinkling of Halogenated Rubber Surfaces

Few surfaces can exist at rest in either wrinkled or unwrinkled states and switch reversibly between these states. Here, we report a new approach to creating reversibly wrinkling systems using the halogenation of rubber to induce a local increase in the glass-transition temperature within a thin layer at the surface. Such systems are obtained by the bromination of molded rubber films. By means of thermomechanical experiments and in situ observations, we show that microscopic wrinkles are produced by unstretching a stretched film below the glass-transition temperature of the brominated layer. These surface patterns are erased within seconds when the wrinkled layer is heated to above its glass transition and recovers its initial equilibrium dimensions. New wrinkles can be produced and erased repeatedly on the same surface. A model is proposed that takes into account the existence of a gradient in bromine content along the thickness of the modified layer. It describes the viscoelastic behavior of these brominated films and captures the temperature dependencies of the thickness of the glassy layer and of the wrinkle wavelength.

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.

Mesostructure Evolution during Storage of Rubber Films from Washed Cream Latex and Skim Latex

Fresh field latex (FL) of Hevea brasiliensis was centrifuged to separate the major compartments: (i) the cream, (ii) the skim plus the C-serum, and (iii) the bottom fraction. Cream was dispersed in distilled water to prepare cream washed latex or CL sample. Skim was collected together with C-serum to prepare the skim latex or SKL sample. Then, films were made from FL, CL and SKL. The mesostructure (macromolecular structure and aggregates or gel) of the natural rubber films was studied by size exclusion chromatography coupled to a multiangular light scattering detector (SEC-MALS). The mesostructure was analyzed on fresh films and on films stored in the laboratory for three months (slow structuring). This study showed that FL and CL films had bimodal elution profiles of long and short polyisoprene chains as revealed by the two peaks on the chromatograms at low and high elution volumes, respectively. On the contrary, SKL films exhibited unimodal elution profiles at low elution volume and a highly abnormal molar masses elution profiles. After 3 months storage, the mesostructure of FL evolved dramatically especially the number-average molar masses (Mn), which increased by 60%. The mesostructure of CL films evolved at a lesser extent and, the mesostructure of SKL films exhibited no significant change. These results indicated (i) the skim rubber particles are not prone to slow structuring during storage in presence of serum and (ii) some constituents either in the serum or/and in the bottom fraction could still be present with cream and be involved in the slow structuring of cream particles latex.

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.

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

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

Piezoelectric rubber films for autonomous physiological monitoring systems

We have successfully demonstrated the fabrication of piezoelectric rubber films and their applications in heartbeat sensing and human energy harvesting. To realize the desired stretchability and electromechanical sensitivity, cellular polydimethylsiloxane (PDMS) structures with micrometer-sized voids are internally implanted with bipolar charges, which function as dipoles and respond promptly to diverse electromechanical stimuli. The resulting composite structures behave like rubber (with an elastic modulus about 300kPa) and show strong piezoelectricity (with a piezoelectric coefficient d33 higher than 1500pC/N). In the prototype demonstration, an autonomous heartbeat monitoring system utilizing stacked piezoelectric PDMS films is demonstrated. While integrated with a 12-μAh solid-state energy storage device and a 552-nW nano-power charge amplifier, the energy harvested from human body is stored and employed to monitor heartbeat. With a working area of 10cm2 and a compressive load of 10kg, it is estimated that a charge of 0.1μC/cycle can be collected using a single-layered piezoelectric rubber film. Furthermore, multiple layers can be stacked and connected in parallel to magnify the charge output. As such, the demonstrated piezoelectric rubber films, which function as both stretchable energy harvesters and highly-sensitive impact sensors, possess a great potential for the realization of wearable and implantable human physiological monitoring systems.

Orientational motions of chain segments in natural rubber crosslinked under uniaxial deformation

Natural rubber (NR) film was crosslinked by γ-irradiation under uniaxial extension. The degree of deformation defined as λ′=l′/l0′ (l0′ and l′ being the lengths of relaxed and uniaxially deformed sample, respectively) was constant and equal to 1.50, and the total irradiation dose was 300kGy. Deuterium NMR spectroscopy, known as an extremely sensitive method to detect anisotropic molecular motions, was applied for the study of dynamic behaviour of polyisoprene chain segments. Perdeuterated cyclohexane was used as deuterium probe. NMR spectra indicate that segmental motions in NR films crosslinked under deformation are anisotropic. Moreover, spectra of NR films stretched in the direction parallel and perpendicular to the direction of deformation applied during the crosslinking process show an intrinsic difference in orientational behaviour of chain segments.

Dielectric relaxation studies on nanocomposites of rubber with nanofibrillated cellulose

In this work we present a study in nanocomposite rubber films with different amounts of nanofibrillated cellulose (NFC), extracted from the rachis of date palm tree. The nanocomposite films were investigated using impedance spectroscopy. The pure matrix presents three processes: α relaxation corresponding to the glass transition, a water polarization relaxation and an ionic conduction phenomenon. The incorporation of NFCs increases the dielectric losses and is responsible for other relaxation processes, directly related to the filler. A first phenomenon is associated to the presence of residual lignin and extractive substances at the surface of the filler, and a second one is due to an interfacial polarization. A dual effect of adding nanofillers in the Tg behavior was observed. The effect of water is becoming increasingly important with NFC content. The dielectric relaxation strength increases as a function of the filler concentration up to a threshold value.

Characterization of a non-thermal plasma torch in streamer mode and its effect on polyvinyl chloride and silicone rubber surfaces

In this study, a non-thermal plasma torch in steamer mode was characterized to apply for surface modification in ambient air. The plasma source is a central rod-ring configuration based on DBD operation. Mixture of Ar/air gases was passed through the hollow Copper rod. A home-built high voltage generator at 18.8 kHz was employed to ignite the plasma. Electrical features of plasma torch were studied and different regions of plasma were examined using optical emission spectroscopy to explore the reactive species that result in efficient treatment. The surfaces of polyvinyl chloride (PVC) and silicone rubber (SIR) films were treated by the cold plasma torch. Contact angle measurement shows the improvement of surface hydrophilicity and wettability. Analysis revealed that the surface energy of the films increases indicating their activation after plasma treatment. This process is attributed to increasing the polar component of the surface energy. • The cold plasma torch used is Inexpensive, efficient and easy to use. • OES revealed the plasma reactive species resulted in the surfaces activation. • Plasma treatment improves PVC and SIR wettability and makes them more efficient.