Papers by Keyword: Polyvinyl Acetate

Abstract: Synthesis of Polyvinyl Acetate (PVAc) through the conversion of Vinyl Acetate Monomer (VAM) was carried out by emulsion polymerization method assisted by thermal initiator Ammonium persulfate (APS) under reaction temperature was kept at 70 °C – 80 °C with 5 hours of reaction time and agitation speed at 300 rpm. The polymerization reaction was running used batch process technique where is all components were mixed all together simultaneously. A set of polymerization reactions was conducted when the absence of surfactant and cationic and amphoteric surfactant presence. The monomer chain's double bond was found at 1645 cm^-1 was measured by FTIR Spectrophotometer did not disappear after polymerization reaction was utterly done. The spectrum FTIR of Polyvinyl acetate did not explicitly found at 1644 cm^-1. During the reaction, characterization was conducted by measuring the solid content value where the maximum solid content was achieved was 6,1 % when using Amphoteric surfactant while the lowest solid content was obtained when the absence of surfactant. Other parameters were conducted to observe the acidity value by pH Meter.

Abstract: During the last decades, biomaterials have been deeply studied to perform and improve coatings for biomedical devices. Metallic materials, especially in the orthopedic field, represent the most common material used for different type of devices thanks to their good mechanical properties. Nevertheless, low/medium resistance to corrosion and low osteointegration ability characterizes these materials. To overcome these problems, the use of biocoatings on metals substrate is largely diffused. In fact, biocoatings have a key role to confer biocompatibility properties, to inhibit corrosion and thus improve the lifetime of implanted devices. In this work, the attention was focused on Hydroxyapatite-Chitosan (HA/CS) and Hydroxyapatite-Polyvinylacetate (HA/PVAc) composites, that have been studied as biocoatings for 304 SS based devices. Hydroxyapatite was selected for its osteoconductivity thanks to its chemical structure similar to bones. Furthermore, Chitosan and Polyvinylacetate are largely used yet in medical field (e.g. antibacterial agent or drug deliver) and in this work were used to create a synergic interaction with hydroxyapatite to increase the strength and bioactivity of coating. Biocotings were obtained by galvanic deposition process that does not require an external power supply. It is a spontaneous electrochemical deposition in which materials with different standard electrochemical potential were short-circuited and immersed in an electrolytic solution. Electrons supply for the cathodic reaction in the noblest material comes from oxidation of the less noble material. SEM, EDS, XRD and RAMAN were performed for chemical-physics characterization of biocoatings. Polarization and impedance measurements have been carried out to evaluate corrosion behavior. Besides, in-vitro cytotoxicity assays have been done for the biological features.

Abstract: Nanocomposite films from polyvinyl acetate (PVAc) dispersion and multi walled carbon nanotubes (MWCNTs) were prepared by solution casting technique. Stress-strain properties showed increase in elastic modulus and yield strength. Mechanical properties characterized by dynamic mechanical thermal analysis represented increase in storage modulus below glass transition temperature. Studied dielectrical properties of PVAc/MWCNT nanocomposites revealed formation of conductive MWCNT network in PVAc matrix.

Abstract: The article presents the wood composite materials based on biodegradable component of polyvinyl acetate with the filler in a form of wood flour of pine trees of two types: unmodified and thermally modified pine. The sorption properties of composite of both species, namely the ability of a material to absorb moisture depending on the quantity and nature of wood filler were studied. The strength characteristics of composite materials with non-modified and modified wood fillers were investigated and revealed. The research of the loss of relative weight of both types of composite materials while standing in soil was conducted.The expediency of preliminary heat treatment of wood filler on politely if necessary some increase in biostability of the composite is found.

Abstract: Wood, a potentially good construction material in terms of sustainability, has less structural use now in India. Due to easy availability, low cost and good working quality there is a scope for the value addition of rubber wood in the Country. Finger jointing technology benefits high economic advantage by upgrading rubber wood. There is a dearth of information for the influence of adhesive on the mechanical properties of jointed rubber wood in India. This study was conducted to evaluate the effects of adhesive type on the end jointing and face gluing of rubber wood. The end jointing adopted for the study was the most common finger joint configuration of the wood industry in Kerala, the largest producer of rubber wood in the Country. The adhesives were polyvinyl acetate (PVAc) and phenol resorcinol formaldehyde (PRF). The face gluing evaluation was done based on the adhesive bond strength and percentage wood failure. The integrity of glue types to delamination was also tested .The results of the study have indicated glue type has no statistically significant effect on modulus of rupture, modulus of elasticity of finger joints and the shear strength of adhesive bond in the dry stage with the same wood failure percentage. The joint efficiency of PRF adhesive was superior to PVAc in tension and compression of finger joints. The PRF adhesive exhibited excellent performance in the exterior exposure condition durability test.

Abstract: VAc/Veova10/MAA copolymer latex containing carboxyl groups was synthesized by the semi-continuous seed emulsion polymerization with vinyl acetate (VAc), vinyl ester of versatic acid (Veova10) and methacrylic acid (MAA). Alkali-thickening characteristics of VAc/Veova10/MAA copolymer latex containing carboxyl groups, adjusted from pH 5.5 to 6.4, 8.9, 9.8 with NaOH aq., were investigated by DSC. The results showed that the viscosities of VAc/Veova10/MAA copolymer latex were increased with the inceasing of pH, The frozen temperature peaks were observed to increase with the increasing of pH, the thawed temperature peaks were shifted to lower temperature, and the state of water in latexes were different. The partial morphologies of latexes were irregular and latexes were pseudoplastic fluid. And water absorption of films were increased with the increasing of pH in latexes and dry and wet shear strengths were also decreased.

Abstract: The use of starch on polyvinyl acetate emulsion blend modified in order to achieve improved film toughness, which aims to improve water resistance and film-forming emulsion adhesive performance. Dynamic mechanical properties (DMA), scanning electron microscopy (SEM) method was used to analyze the dynamics of film emulsion blend composite mechanics, the distribution of latex particles and glass transition temperature. The results show that: with pure polyvinyl acetate (PVAc) compared to starch-modified film-forming emulsion film distribution, glass transition temperature of the homopolymer emulsion up to 30°C.

Abstract: In this paper, reverse atom transfer radical polymerization (RATRP) was used to prepare polyvinyl acetate (PVAc) with lower polydispersity index (PDI). The different ligands such as bpy and PMDETA were studied separately to control the polymerization of VAc. The results show that RATRP is not controlled with bpy as ligand, but it is possible to obtain PVAc with low PDI when PMDETA was used as ligand.

Abstract: 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.

Abstract: Intensive research is currently underway to exploit the highly interesting properties of nano-sized particles and organic molecules for optical, electronic and other applications. Recently, it has been shown that nano-sized particles and small organic molecules embedded in polymer matrices can be used to realise memory devices. Such memory devices are simple to fabricate via the spin-on technique. This work presents an attempt to use sea salt, embedded in polyvinyl acetate, in the making of the memory devices. A polymer blend of polyvinyl acetate and sodium chloride (NaCl) was prepared in methanol and spin coated onto a glass substrate marked with thin Al tracks and a top contact was evaporated onto the blend after drying - this resulted in a metal-organic-metal (MOM) structure. The current-voltage (I-V) behaviour of MOM devices shows that the devices can be switched from a high conductivity state to a low conductivity state, by applying an external electric field - this property can be exploited to store data bits. The possible charging mechanism, based on the electric dipole formation, is presented in this work. Polymer blends of polyvinyl acetate with nano-particles of BaTiO3 are also investigated to further our understanding of charging mechanism(s).