Tejraj M. Aminabhavi

POLYMERS DERIVED FROM HEXAFLUOROACETONE

Abstract The continuing demand for polymeric materials with a unique combination of properties has brought forth a sizable research effort concerning the use of trifluoromethyl substituents, particularly the 1,1,1,3,3,3-hexafluoroisopropylidene (HFIP) function derived from the incorporation of hexafluoroacetone (HFA) into the monomer. This work had its beginnings approximately 25 years ago when Rogers briefly reported in a patent the preparation of polyimides (PIs) from an hexafluoroisopropylidenebrideged diamine [1,2]. Since then numerous efforts have been made toward the synthesis, characterization, and evaluation of CF3-containing polymers. Much of this information is found in patents, indicating the importance of these polymers to industry. At the present time, at least 11 known classes of polymers containing pendant or backbone-incorporated bis-trifluoromethyl groups have been reported. These polymers show promise as film formers, gas separation membranes, seals, soluble polymers, coatings, and in ot...

Use of Polymers in Concrete Technology

Abstract The technology of composite materials has spread for the past two decades to concrete, one of the most common structural materials. A concrete-polymer composite combines the advantages of both materials to produce properties superior to either single component [1–20]. Traditional construction material, namely portland cement concrete, suffers from serious drawbacks of little or no resistance to chemical attack; rapid freeze–thaw deterioration; low tensile, shear, and bond strengths; and inherent microstructural problems such as air voids and shrinkage cracks [12, 17, 21].

Polymers derived from 2-phenyl-1,1,1,3,3,3-hexafluoropropan-2-ol and its derivatives

Abstract Over the past 25 yr several classes of polymers (epoxy resins, polyurethanes, polyacrylates etc.) derived from aromatic monomers bearing —C(CF 3 ) 2 OH groups have been developed. These materials have exceptional heat, light and chemical resistance in addition to low surface energy, low water absorption and low dielectric constant. They have been suggested for use in a variety of ways such as biological anti-fouling materials, dental composites, cladding for optical fibers, textile impregnants and marine coatings.

Versatile Lightweight Polymer Composites

Abstract Knowledge of polymer composites goes back to antiquity, yet their most spectacular boom, from a scientific point of view, began during the 1960s when their microstructure was studied as it relates to their properties. Modern technology demands newer materials in place of conventional engineering materials. Although concrete is an excellent building material, its use is subject to certain limitations. These include its relatively low tensile strength, a tendency to crack with changes in temperature coupled with moisture absorption, and deterioration due to chemical and physical attack under various environmental conditions. Polymer composites, on the other hand, have outstanding strength and durability which offer several advantages over those of conventional materials.

Water permeation through elastomer laminates: 3. Neoprene/styrene-butadiene rubber

Abstract Permeation rates and activation parameters for the transport of water and 3.5% sodium chloride solution through laminates comprised of Neoprene (CR) and styrene-butadiene rubber (SBR) have been measured at 23°C, 40°C and 60°C. Sodium chloride solution exhibited higher permeation rates than distilled water and the laminates showed a slight directional character with salt water. Also for salt water a reduction of permeation rates compared with the calculated average was observed. However, for the distilled water, essentially no directional behaviour (valving) was observed and no significant differences from calculated averages occurred, except at 60°C. These findings for distilled water are contrary to those found for other laminates. The temperature dependence of permeation rate had an Arrhenius behaviour. Observed activation energies were found to be lower for membranes which exhibited high permeation rates. Furthermore, the measured permeation rates are satisfactorily explained in the light of free volume concepts of diffusion.

POLYIMIDINES - A NEW CLASS OF POLYMERS

Intensive research has occurred in the last twenty years concerning the synthesis and processing of thermally stable polymers1–3. Early explorations in this area can be traced back to the late fifties impelled by the discovery of heterocyclic and aromatic amide polymers, which had the ability to withstand extreme temperatures.

New routes to poly(benzylenebenzimidazoles)

Abstract Reaction of 3,3′-diaminobenzidine with either 3,3,7,7-tetraphenyltetrathiopyromellitide or α , α ′-dibromo-2,5-dicyano- p -xylene produced new polymers which are stable up to 350°C. In the latter case, the solution polymerization was completed in 24 h at reflux temperature in quantitative yields with inherent viscosity of 0.66 dl g −1 ; the dark coloured polymer would dissolve only in formic or sulphuric acid. In the former case, however, an orange coloured solid having inherent viscosity of 0.09 dl g −1 was obtained in quantitative yields; this polymer was soluble in a number of solvents such as chloroform, ethanol, benzene and DMF.

PREPARATION OF POLYURETHANE CATIONOMER BASED AQUEOUS DISPERSIONS

ABSTRACT Polyurethane ionomers have been prepared using different diisocyanates (toluene diisocyanate and hexamethylene diisocyanate) and polyols (polyether and polyesters). These were chain extended with different chain extenders (N-methyl diethanol amine and 1,4-butanediol) followed by quaternization with dimethylsulfate to get the polyurethane cationomers. These ionomers were further dispersed in water to get aqeous polyurethane dispersions. These dispersions were sprayed on leather and physical properties of these leathers were studied.