Browsing by Author "RAMANI, AV"

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    CHITRA HEART-VALVE PROSTHESIS
    (ARTIFICIAL ORGANS, 1987) BHUVANESHWAR, GS; VALIATHAN, MS; RAMANI, AV; LAL, GAV; KUMAR, RS
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    EVALUATION OF MATERIALS FOR ARTIFICIAL-HEART VALVES
    (BULLETIN OF MATERIALS SCIENCE, 1991) BHUVANESHWAR, GS; Muraleedharan, CV; RAMANI, AV; VALIATHAN, MS
    The heart of a normal human being beats about 38 million cycles every year. An artificial heart valve, to perform at this rate in the adverse conditions inside the heart for 20 years or more, should be highly wear-resistant with excellent fatigue strength. Thus, the study of mechanical and physical properties of the materials intended for use in artificial valves becomes an inseparable part of the valve development process itself. The physical and mechanical requirements of the materials used in the Chitra heart valve have been evaluated by studying their water absorption, adhesive wear and abrasive properties. The mechanical durability of the device has been assessed by accelerated life cycle testing. The test systems developed for the above are described here. The results show UHMW-PE to be a highly wear-resistant material suitable for the occluder. The accelerated wear tests show that the valve with Haynes-25 alloy cage and UHMW-PE disc has durability in excess of 50 years.
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    GAS-PERMEABILITY STUDIES ON POLY(VINYL CHLORIDE) BASED POLYMER BLENDS INTENDED FOR MEDICAL APPLICATIONS
    (JOURNAL OF APPLIED POLYMER SCIENCE, 1992) PAL, SN; RAMANI, AV; SUBRAMANIAN, N
    Plasticized PVC finds applications in a wide range of medical products. However, plasticizer leaching, known to take place from these conventional materials, is not desirable. A number of approaches to overcome this problem are mentioned in the literature. We suggest pursuing the polyblend approach. Plasticized PVC containing different amounts of plasticizer, binary polyblends of plasticized PVC (PPVC) with acrylonitrile-butadiene rubber (NBR1), and compounded graft polymer of vinyl chloride and ethylene-vinyl acetate copolymer (EVAPVC), and ternary blends of PPVC, NBR1, and EVAPVC, were formulated. In this article, we report our results of studies on water vapor, O2, CO2, and N2 permeabilities. Increased plasticization for PVC was found to increase permeability for water vapor, O2, CO2, and N2. Rise in temperature increased the permeability for water vapor and the change became faster as the materials crossed the region of T(g). A simple model suggested for permeability worked satisfactorily. The binary and ternary blends, based on PPVC, had lower O2, CO2, and N2 permeability. This improvement in property is of great practical significance and interest and the results indicate that PVC-based polyblends can be investigated further for potential applications in medicine.
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    PRODUCTION AND USE OF BIO-MEDICAL DEVICES - ITS RELEVANCE TO INDIA
    (CURRENT SCIENCE, 1991) RAMANI, AV
    To achieve 'Health for All by 2000 AD.' India needs massive inputs of science and technology. Rupees 60,000 millions worth of medical supplies will be needed in India by 2000 AD. The supplies cover biomedical devices made from all classes of materials using precision light engineering techniques. Indian industry is wary of entering this field because of low perceived demand, unfair competition from imports, need for a strict Good Manufacturing Practice, and unrestricted availability of low cost, poor quality 'look-alikes'. Education of manufacturers and users, enactment of statutes regulating the making and use of these devices could be the answer.
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    STUDIES ON POLY(VINYLCHLORIDE)-BASED POLYMER BLENDS INTENDED FOR MEDICAL APPLICATIONS .2. MECHANICAL-PROPERTIES
    (POLYMER ENGINEERING AND SCIENCE, 1992) PAL, SN; RAMANI, AV; SUBRAMANIAN, N
    Binary polyblends of plasticized poly(vinylchloride) (PPVC1) with acrylonitrile-butadiene rubber (NBR1), compounded graft polymer of vinyl chloride and ethylene-vinyl acetate copolymer (EVAPVC) and ternary blends of PPVC1, NBR1, and EVAPVC were formulated to study mechanical proper-ties. For the "pure" components, elongation at break was found to be in the order PPVC1 < EVAPVC < NBR1. Addition of both EVAPVC and NBR1 resulted in improvement of ultimate elongation and tensile energy to break. PPVC1-NBR1 binary blends exhibited synergistic behavior for both ultimate tensile stress and elongation at break, indicating the presence of appreciable specific interactions between the polymers. About 30% replacement of PPVC1 by NBR1 or EVAPVC resulted in marginal fall in modulus and significant improvement in elongation at break. EVAPVC or blends containing EVAPVC had a tendency to creep. A simple generalized equation suggested for various mechanical properties works satisfactorily. The results obtained have practical implications and indicate that PVC-based polyblends can be investigated further for potential applications in medicine.