Poly Vinyl Acetate Films Research Articles

Application of the Ion Beam Graft Polymerization Method to the Thin Film Diagnosis

The ion beam graft polymerization (IBGP) method was applied to diagnosis of thin film of several tens μm or less thickness. After a sample stacked on polyethylene film was irradiated with proton beam, polyethylene was graft-polymerized with acrylic acid monomer. From observation of the graft-polymerized polyethylene, information inside the sample are obtained. Demonstrations of the diagnosis method were conducted for a leaf sample and a polyvinyl acetate film contained some voids. Using imitation samples made of metal and polymer sheets, some characteristics of this method was obtained. This method is useful for diagnosis for voids in thin film.

Physiological relevant in vitro evaluation of polymer coats for gastroretentive floating tablets

Gastroretentive drug delivery systems are retained in the stomach for a sufficient time interval, releasing the drug in a controlled manner. According to literature, the floating principle is the most frequently used formulation approach for gastric retention. However, many publications lack information of the floating forces, the impact of different pH-values and almost no information exist concerning the resistance of the floating performance against physiological relevant stress. Therefore, we evaluated the performance of CO2-generating floating bilayer (drug and floating layer) tablets with respect to robustness, drug release profile, pH dependence and floating behaviour. Bilayer tablets were coated with a flexible and water permeable, but CO2-retaining polymer film of either polyvinyl acetate or ammonio-methacrylate copolymer type A. Metformin-HCl was used as a relevant model drug due to its dose-dependent and saturable absorption from the proximal part of the small intestine. To mimic physiological relevant mechanical stress conditions, recently developed dissolution stress tests with pulsed pressures were applied in addition to release studies according to the pharmacopeia.Bilayer tablets coated with polyvinyl acetate showed short floating lag times, reasonable floating strength values, floating durations of more than 24h in simulated gastric fluid and a robust and pH independent release of Metformin-HCl. Tablets coated with ammonio-methacrylate copolymer type A showed a higher permeability for the active ingredient combined with a decreased robustness of the inflated tablets. Both polymers can be used for balloon-like floating devices. The appropriate polymer has to be chosen dependent from the properties of the active ingredient and requested application of the delivery device. Furthermore, the dissolution stress test analysis is able to indicate possible safety issues of gastroretentive formulations as well as to characterise the robustness of formulation principles towards mechanical stresses of bio-relevant intensity.

Nanocrystalline cellulose (NCC): A renewable nano-material for polyvinyl acetate (PVA) adhesive

In this study nanocrystalline cellulose (NCC) was used to improve the performance of polyvinyl acetate (PVA) as a wood adhesive. NCC was added to PVA at different loadings (1%, 2% and 3%) and the blends were used as binder for wood. Block shear tests were done to evaluate bonding strength of PVA at different conditions; dry and wet conditions, at the elevated temperature (100°C). The mechanical properties of PVA film and its composites with NCC were measured by nanoindentation technique. Thermal stability and structure of nanocomposites were studied by thermogravimetric analysis and atomic force microscopy (AFM). The block shear tests demonstrate that NCC can improve bonding strength of PVA in all conditions. Hardness, modulus of elasticity (MOE) and creep of PVA film were also changed positively by the addition of NCC. Thermal stability of PVA was significantly improved as NCC was added to PVA. Structural studies revealed that variations in shear strength and other properties can be related to the quality of NCC dispersion in the PVA matrix.

Improving spectral response of monocrystalline silicon photovoltaic modules using high efficient luminescent down‐shifting Eu3+ complexes

ABSTRACTOne way to improve the spectral response of solar cells in the ultraviolet (UV) region is to convert high energy photons into lower energy ones via luminescent down‐shifting (LDS) technique. Eu3+ complexes are excellent LDS species because of their high luminescence quantum efficiency and large Stokes‐shift. In this paper, we aim to optimize the LDS property of Eu3+ complexes for monocrystalline silicon (c‐Si) photovoltaic (PV) modules by chemical modification of the UV absorbing antenna ligands. Our results show that the LDS performances of Eu3+ complexes are strongly dependent on their absorption and emission properties. By carefully modifying the absorption and emission features, the LDS performances of Eu3+ complexes can be significantly improved. The spectroscopic features of the Eu3+ complex with a bispinene‐containing bipyridyl ligand match well with the requirement of ideal LDS species for the c‐Si PV module. Simple coating of polyvinyl acetate film doped with this complex onto the surface of c‐Si PV module leads to increase of the external quantum efficiency in the UV region and enhancement of the PV module efficiency η (from 16.05% to 16.37%). Copyright © 2012 John Wiley & Sons, Ltd.

Performances of Polyvinyl Acetate Hybrid Emulsions with Nanoparticles SiO<sub>2</sub>

Polyvinyl acetate（PVAc）hybrid emulsions with nanoparticles SiO2 were prepared by the semi-continuous seeding emulsion polymerization. The micro-morphologies of the hybrid emulsions, the diameters and distributions of the latex particles were characterized with the aid of scanning electron microscope (SEM) and diameter analyzer. Adhesive properties of hybrid emulsions and the properties of the emulsion films were determined by mechanical properties tester and dynamic mechanics analyzer (DMA). And the rheological behaviors of hybrid emulsions were measured via rheometer. SEM and diameter analysis showed that the process of the nanoparticles SiO2 by ultrasonic made a good dispersibility of latex particles in emulsions, diameters of the latex particles were 0.68~0.89μm with the content of SiO2 from 0 to 1.0% (% in relation to the total mass VAc), and indexes of distributions of particle size were increased with the increasing of the content of SiO2 from 0 to 1.0%. Adhesion strengths of PVAc emulsions modified with nanoparticles SiO2 were improved. DMA results indicated that the films of PVAc/SiO2 hybrid emulsions had the higher storage modulus than the film of PVAc, the temperatures of glass transition of the films of PVAc/SiO2 hybrid emulsions were not changed obviously, and the water absorptions of films were decreased. Rheological results revealed that flow consistency indexes were increased then decreased with the increasing of the content of SiO2 from 0 to 1.0%, and PVAc/SiO2 hybrid emulsions were typical pseudoplastic fluid.

Effect of Transdermally Delivered Aspirin on Blood Coagulation Parameters

The efficacy of oral aspirin treatment in the secondary prevention of cardio and cerebro vascular disease is well known. However oral administration is often associated with abdominal discomfort. The feasibility of delivering aspirin transdermally from eudragit and polyvinyl acetate (PVA) matrix-type patches to enhance its antithrombotic efficiency of aspirin was investigated. Transdermal films containing mixture of eudragit RL: eudragit RS and polyvinyl acetate were fabricated. Eudragit RL: eudragit RS (5:1) films containing 30 mg/ transdermal patch aspirin showed maximum release (11.891.1g/cm 2 ) after 24 hrs as compared to PVA films. With regards to appearance eudragit films were also wrinkle free, uniform, flexible and transparent with good adhesion property to skin. The effect of turpentine oil and lemon oil at different concentrations on the in vitro percutaneous absorption of aspirin from eudragit copolymer patches through rat skin was investigated. Two formulation containing 50 mg/transdermal patch ASA with 0.042 ml turpentine oil and 0.042 ml lemon oil showed a significantly higher flux of ASA 4.22 g/cm 2 /hr and 38.52 g/cm 2 /hr respectively. The optimized formulations influenced the blood coagulation parameters (bleeding time, prothrombin time, Activated partial prothrombin time) significantly by means of affecting both the extrinsic coagulation system and the intrinsic coagulation system as compared to orally administered and control gel formulations.

Characterization of polymeric films for transdermal drug delivery

Drug-free films of different polymers were prepared by casting solventtechnique employing mercury as a substrate. The physical and chemical properties of the films were evaluated for their potential transdermal use. The films were found to be stable and intact at ambient temperature and humidity conditions. The results indicate that the polymeric films of hydroxypropyl methyl cellulose (HPMC), polyvinyl acetate (PVA), carboxymethyl cellulose (CMC), cellulose acetate (CA), ethyl acetate (EC) and Eudragit RL100 & S100 along with those of polyvinyl pyrrolidone (PVP), and propylene glycol (PPG) as plasticizer appear promising for the development of suitable transdermal drug delivery systems (TDDS).

The Emulsion Polymerization of Each of Vinyl Acetate and Butyl Acrylate Monomers Using bis (2-ethylhexyl) Maleate for Improving the Physicomechanical Properties of Paints and Adhesive Films

Improving the water sensitivity of polyvinyl acetate PVAc films as well as pressure sensitivity, adhesion and washability of polybutyl acrylate were achieved by using bis (2-ethylhexyl) maleate (BEHM). The emulsion polymerization kinetics of vinyl acetate and butyl acrylate in presence of BEHM was studied. The order of the polymerization reaction with respect to the BEHM in presence of each of vinyl acetate and butyl acrylate was studied. The physicomechanical properties of the polyvinyl acetate films and vinyl acetate-butyl acrylate copolymer films were studied in presence of BEHM and the obtained results were matched with those prepared in the presence of pluronic F 108 and showed superior values. The obtained mean average molecular weights were found to be smaller in presence of BEHM assuring the presence of chain transfer reaction.

Polymer coating of paramagnetic particulates for in vivo oxygen-sensing applications

Crystalline lithium phthalocyanine (LiPc) can be used to sense oxygen. To enhance biocompatibility/stability of LiPc, we encapsulated LiPc in Teflon AF (TAF), cellulose acetate (CA), and polyvinyl acetate (PVAc) (TAF, previously used to encapsulate LiPc, was a comparator). We identified water-miscible solvents that don't dissolve LiPc crystals, but are solvents for the polymers, and encapsulated crystals by solvent evaporation. Oxygen sensitivity of films was characterized in vitro and in vivo. Encapsulation did not change LiPc oximetry properties in vitro at anoxic conditions or varying partial pressures of oxygen (pO2). EPR linewidth of encapsulated particles was linear with pO2, responding to pO2 changes quickly and reproducibly for dynamic measurements. Encapsulated LiPc was unaffected by biological oxidoreductants, stable in vivo for four weeks. Oximetry, stability and biocompatibility properties of LiPc films were comparable, but both CA and PVAc films are cheaper, and easier to fabricate and handle than TAF films, making them superior.

Study on Different Solution-Cast Films of PMMA and PVAc

Transparent films of PMMA (poly methyl methacrylate) and PVAc (polyvinyl acetate), previously dissolved in chloroform, toluene and tetrahydrofuran (THF), were prepared by using solution-cast technique. FT-IR transmission spectra were obtained from the samples. Also, different concentrations of PMMA/PVAc blend, dissolved in chloroform, were prepared by the same method. From absorption, transmission and specular reflection spectra, the absorption coefficient (α) and refractive index (n) have been calculated at room temperature and also after heating. The values of the optical band gap (Eg) have been obtained from the direct allowed transitions in k-space. In addition, the values of width of the tails of localized states in the band gap (Eu) were evaluated from Urbach edges.

Spectroscopic and thermal studies of PS/PVAc blends

Polystyrene and polyvinyl acetate (PS/PVAc) films were blended with different contents using casting method. The effect of PS content on PVAc blends was investigated by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Ultra violet and visible studies (UV/VIS), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Significant changes in FT-IR, XRD and DSC analysis are observed which reveals an interactions between the two polymers and PS/PVAc blends had good or certain miscibility. XRD scans show some changes in the intensity and the height of the amorphous halos with increased PS. UV/VIS analysis revealed that the optical band gap decreases with increasing content of PS from 5 to 4.11 eV. A single glass transition temperature for each blend was observed, this DSC results supported that the miscibility existed in the blend. The apparent activation energy (E) of the blends was evaluated using TGA analysis. The value of E was increased with the increase of PS content.

Development of a 1‐Methylcyclopropene (1‐MCP) Sachet Release System

ABSTRACT The partitioning of 1‐methylcyclopropene (1‐MCP) between the gas/polymer matrix was determined for 2 adsorbing agents and 4 sachet materials to estimate the adsorption potential of 1‐MCP at 23°C. The release study was performed using a closed system under 2 different environmental conditions, dry air (0% RH) and 90% RH. Sachets made from Tyvek®, paper, low‐density polyethylene (LDPE), and polyvinyl acetate (PVA) materials were fabricated to contain silica gel and activated carbon. Activated carbon sachets did not release 1‐MCP at either testing condition. Activated carbon had a very strong affinity for 1‐MCP. The permeability coefficients of 1‐MCP and water in polyethylene and polyvinyl acetate films were determined using a quasi‐isostatic method. LDPE sachets containing silica gel had similar 1‐MCP release rates at both 0% and 90% RH. PVA sachets containing silica gel had slow release of 1‐MCP. The amount of 1‐MCP released from PVA sachets containing silica gel at 90% RH was larger than the amount of 1‐MCP released at 0% RH. Release of 1‐MCP from paper and Tyvek sachets was largely dependent on the sorbate‐absorbing ability of the adsorbing agents.

Photovoltaic quantum efficiency enhancement by light harvesting of organo-lanthanide complexes

An increase of about 1% of the delivered power by a mono-crystalline commercial silicon solar cell has been obtained by coating the cell with an active poly-vinylacetate film doped with a light harvesting phenanthroline– Eu 3 + complex. The dopant absorbs the UV component of the solar spectrum, where the silicon-based cells are almost blind, and emits red light that can be converted with an efficiency close to the maximum. This effect, achieved by a low cost encapsulation process, has been proven for the case of Air Mass 0 lighting conditions, and could be exploited also for terrestrial applications with the proper choice of the organic ligand.

Protection of stainless steel by polyaniline films against corrosion in aqueous environments

Polyaniline (PANI) thin films were electrochemically deposited by cyclic voltammetry on stainless steel electrode previously covered by a thin film of polyvinyl acetate (PVAc). The corrosion resistance of PANI covered stainless steel substrates was estimated by using potentiodynamic polarization curves and its linear polarization resistance (LPR) was measured in 0.5 M H2SO4, 0.5 M NaCl and 0.5 M NaOH aqueous solutions at room temperature. The results indicate that the PANI-PVAc films did improve the corrosion resistance of the stainless steel in NaOH, behaving even worst, in the case of PANI film, than the uncoated substrate. In H2SO4 both PANI and PANI-PVAc coatings gave good protection for the stainless steel electrode, with a slightly better performance of PANI-PVAc than PANI. In NaCl solution both PANI and PANI-PVAc films provided a good protection against corrosion. The better performance of PANI-PVAc coatings for corrosion protection in basic media may be due to its major chemical stability compared to simple PANI films, which lose their conductivity in high pH solutions. The Ecorr (free corrosion potential) value of the coated substrate was in the passive region of the uncoated substrate in acidic environment but in the active region in neutral or basic environment.

Ophthalmic Delivery of Ciprofloxacin Hydrochloride from Different Polymer Formulations: In Vitro and In Vivo Studies

Reservoir-type ocular inserts were fabricated using sodium alginate containing ciprofloxacin hydrochloride as the core (drug reservoir) that was sandwiched between the Eudragit and/or polyvinylacetate films. Ocular inserts were packaged in aluminium foil and sterilized by gamma radiation. These were tested for sterility as per British Pharmacopoeia (BP). Ocular inserts were evaluated for in vitro release rate studies, microbial efficacy, in vivo release studies, efficacy against induced bacterial conjunctivitis in rabbit's eyes, concentration in the aqueous humor, and stability studies as per the International Conference on Harmonization (ICH) guidelines. Ocular inserts passed the test for sterility. They showed zero-order release of the drug in the in vitro and in vivo release studies over a period of 120 hr. The drug was found to be active against selected microorganisms as was proved by microbial efficacy studies. A high correlation coefficient was found between in vitro and in vivo release rate studies. Better improvement was observed in artificially induced bacterial conjunctivitis in rabbit's eyes, compared with marketed eye drops and placebo. Drug concentration in the aqueous humor was found above Minimum Inhibitory Concentration (MIC-90) against selected microorganisms. Shelf-life of the product was found to be more than 2 years.

Study of electrical and optical frequency response of neutron irradiated polyvinyl acetate thick films

Electrical and optical frequency response of polyvinyl acetate (PVAc) polymer has been studied by making capacitors, using PVAc film irradiated with neutron, and unirradiated, as their dielectric. It has been observed that the neutron irradiation induces crystallinity in the virgin sample of PVAc. The UV absorption studies of this polymer show an increase in its absorption after neutron irradiation which is in agreement with the increase in dielectric constant in the capacity measurements. It also reflects the possibility of 16% increase in the crystallinity of the sample which is supported by X-ray diffraction analysis of both the virgin and the irradiated polymer.

Mesoscopic-scale dielectric relaxation at the glass transition

Using scanning-probe-microscopy techniques, we have measured dielectric relaxation on ultrasmall, mesoscopic, length scales in a glassy polymer (polyvinyl acetate) film near its glass transition. The effective length scale sampled by these techniques is \ensuremath{\sim}50 nm. This is large enough to probe subsurface properties, but small enough to observe deviations from bulklike behavior in the form of fluctuations in the shape of the relaxation function near the glass transition. These fluctuations are argued to arise from cooperative dynamics and intrinsic heterogeneities on somewhat smaller length scales.

Study on the properties of a polyvinylacetate film at the air-water interface

Isotherms of surface pressure against surface area for a polyvinylacetate (PVAc) film at the air-water interface were determined at 20.52°C. Measurements of surface moment, hysteresis, and pressure relaxation in a constant area were subsequently conducted at appropriate area regions for elucidation of the correlation of properties and conformations of PVAc film. It is concluded that the film is stable and exhibits a perfectly reversible compression in the areas larger than 13 A2/repeat-unit but assumes three different conformations for three regions (70-42), (42-25), and (25-13) A2/repeat-unit, respectively. Finally, a twisting chain loop model is proposed for the interpretation of hysteresis and pressure relaxation occurring in the areas near and in the collapse region.

MOISTURE MEASUREMENT BY FT-IR-SPECTROSCOPY

ABSTRACT This contribution reports on the use of a FT-IR-spectrometer for measuring concentrations during the drying of thin films of Polyvinyl acetate (PVAc) and Methanol. Calibration was carried out by differential weighing. The spectra were taken in transmission mode while dried air was blown over the liquid films. The obtained accuracy was +/− (5% + 0,8 g/m2) for small contents of Methanol and +/− (10 % 2 g/m2) for higher Methanol contents. The content of PVAc could be measured with 5% accuracy. The experiments were carried out at room temperature; the examined films had a thickness of about 30 to 60 microns when completely dry.

Calcium density measurement in histological samples of trabecular bone of normal subjects: Relationship with aging

It is well-known that bone volume decreases with age both in normal subjects and particularly in osteoporotic patients. It is not well demonstrated, however, whether bone loss is associated with changes in the composition of bone tissue and especially with altered concentration of mineral elements. To verify whether calcium density changes with aging, autoptic specimens, of iliac crest trabecular bone from 20 normal subjects between 21 and 66 years, 10 males and 10 females were analyzed by using a new method which allows the measurement of calcium density in a non-destructive way, on entire histologic sections of the bone. Bone specimens were embedded in araidite and tissue sections, about 3 microm thick and 4x4 mm size, were mounted onto polyvinyl acetate films and analyzed by PIXE (proton induced X-ray emission) using the CISE setup for calcium content determination. The same bone tissue sections were then mounted on glass slides, stained with the Von Kossa method and the volume of calcified bone was measured with a semiautomatic image analyzer (Videoplan). 3 to 4 sections from each subject were analyzed and the values of calcium concentration were derived in microg/microl. Similar values of calcium density were found in males and females (535.6+77.1 and 539.2+74.1 microg/microl, respectively). No significant correlation between calcium density and age was observed either in all cases (r=0.0925) or in males (r=-0.0687) and in females (r=0.2676) separately. The unchanged calcium density during aging obtained by combining PIXE and histomorphometric techniques demonstrates that the skeletal calcium reduction observed in old age and probably during osteoporosis, is mainly due to the decrease of bone volume.