http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/876 2013-05-25T00:33:25Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/907 Thermal degradation of short kevlar fibre thermoplastic polyurethane composite Sunil K Narayanankutty The thermal degradation of short kevlar fibre-thermoplastic polyurethane (TPU) composites has been studied by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). TGA showed that the thermal degradation of TPU takes place in two steps with peak maxima (T1max and T2ma,) at 383°C and 448°C, respectively. In the presence of 10-40 phr of short kevlar fibres, T1_ and T2max were shifted to lower temperatures. The temperature of onset of degradation was increased from 245 to 255°C at 40 parts per hundred rubber (phr) fibre loading. Kinetic studies showed that the degradation of TPU and kevlar-TPU composite follows first-order reaction kinetics. The DSC study showed that there is an improvement in thermal stability of TPU in the presence of 20 phr of short kevlar fibres. 1991-08-29T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/906 Thermal degradation of short polyester fiber polyurethane elastomer composite Sunil K Narayanankutty The thermal degradation of short polyester fiber reinforced polyurethane composites with and without different bonding agents has been studied by thermogravimetric analysis . It was found that degradation of the polyurethane takes place in two steps and that of the composites takes place in three steps. With the incorporation of 30 phr of fiber in the matrix , the onset of degradation was shifted from 230 to 238 ° C. The presence of bonding agents in the virgin elastomer and the composite gave an improved thermal stability . Results of kinetic studies showed that the degradation of polyurethane and the reinforced composites with and without bonding agents follows first -order reaction kinetics 1997-05-17T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/905 Studies on the curing of short polyester fiber-polyurethane elastomer composite with different interfacial bonding agents Sunil K Narayanankutty The cure characteristics of short fiber-polyurethane elastomer were studied with respect to different fiber-matrix bonding agents. A hexamethylenetetramine- resorcinol -hydrated silica based bonding agent was found to affect the stability of the composite. A new bonding agent, TP resin, based on polymeric toluenediisocyanate and polypropylene glycol has been developed. Cure characteristics of the composite with and without TP resin at different fiber loadings were also compared. Minimum torque, scorch time and optimum cure time increased with fiber content. Maximum torque was consistently higher with TP resin at all fiber loadings. 1995-02-07T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/904 Stress Relaxation of Polyester Fiber-Polyurethane Elastomer Composite with Different Interfacial Bonding Agents Sunil K Narayanankutty The stress relaxation behavior of polyurethane elastomer and short polyester fiber filled elastomer composites with and without bonding agents at different strain levels and strain rates was studied. It was found that these compounds exhibit a multistage relaxation mechanism and that the rate of relaxation and cross-over time depend on the strain level and strain rate. The incorporation of fibers reduced the stage-I relaxation rate and increased the cross-over time of the gum vulcanisate. A higher rate of relaxation (first stage) was shown by the composites with longitudinal fiber orientation and composites with bonding agents. 1998-04-01T00:00:00Z