Rajnish Kumar | Gautam Buddha University (original) (raw)
Papers by Rajnish Kumar
VBRI Press, Sweden, 2018
Environment friendly electrical insulation material was developed using bio based rectangular cro... more Environment friendly electrical insulation material was developed using bio based rectangular cross sectioned sisal fibrils as reinforcement. High content cellulose base fibrils fibrillated by mechanical disintegration method into macro and micro fibrils from coarse sisal fibre. This fibrils were randomly distributed in polymer matrix. These composites were characterized in term of electrical, mechanical and thermal properties to investigate the stability for high strength electrical insulation materials. Excellent mechanical properties were observed. Tensile, flexural and impact strength of composites at 40 wt. % fibril loading improved by 151.34, 197.43 and 360.07 % as compared to unsaturated polyester resin. A few micro-mechanical models were compared with the experimental values. Nielson-Chen Model predicted the experimental data most accurately. The electrical properties of surface modified sisal fibril composites improved significantly in higher frequency. DSC analysis showed that the decomposition temperature of composite was higher, around 22°C than that of the polyester resin. Thermal degradation reduced and was observed in the range of 83-87% of fibril composites as compared to 97% of resin. Fibril composites are highly sensitive to electrical frequency and exhibit excellent electrical insulation property at 20 kHz. Alkali treated fibril based composites resulted an environment friendly thermally stable, high strength insulation material. Copyright © 2018 VBRI Press.
Wiley- Polymer composites, 2017
A novel hybrid composition of sisal fibrils and kenaf fibers has been introduced first time as re... more A novel hybrid composition of sisal fibrils and kenaf fibers has been introduced first time as reinforcement in composite preparation for the environmental friendly high strength electrical insulation applications. Hybrid reinforcement was increased from 10 to 40 wt% in unsaturated polyester resin. The sisal fibril used in this study was extracted from sisal fiber. Alkali treatment was employed and FTIR analysis was done to study its effect on sisal fibrils and kenaf fibers. A positive hybridization effect was observed for the composites. Hybrid composite showed 24 and 18% increase in tensile strength, 30 and 36.4% increase in flexural strength, and 196.3 and 196% increase in impact strength as compared to the composites having same loading of 40 wt% with sisal fibrils and kenaf fibers, respectively. Scanning electron microscopy of the fractured mechanical testing samples was carried out to understand the nature of fibril/fiber/matrix interface. Electrical characterization showed high electrical insulation capability of the hybrid composites. Thermal stability of hybrid composites was also found higher than sisal fibrils and kenaf fibers reinforced composites. A comparative study of properties of sisal fibril/kenaf fiber reinforced hybrid polyester composites with various single and hybrid fiber composites is done. It has been concluded that the developed novel hybrid composite has the potential to replace various existing natural and synthetic fiber composites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers
VBRI Press, Sweden, 2017
Randomly distributed kenaf fibre with varying length (5-50mm) and weight fractions (25-40%) were ... more Randomly distributed kenaf fibre with varying length (5-50mm) and weight fractions (25-40%) were used to reinforce epoxy resin to prepare environment friendly composites. Effect of fibre length with constant fibre loading on dynamic mechanical properties was studied and its effect on storage modulus, loss modulus and damping factor were investigated. Kenaf fibres were also subjected to alkali treatment to improve interaction with the epoxy resin. The mechanical properties of composites improved with the length and loading of fibres. Tensile strength, flexural strength and impact strength of composites at 40 wt% of fibre reinforcement improved by 46, 51 and 97% as compared to the composites containing 25 wt% of kenaf fibre. It was also observed that fibre folds developed during mixing became significant factor which limited the improvement in mechanical strength of kenaf epoxy composites. A few important predictive models namely rule of mixture, Haplin-Tsai, Nielson Chen and Manera models were compared with the experimental values obtained in this present study. Manera model predicted the experimental data most accurately. Alkali treatment improved the interface and its outcome reflected in the improved modulus that increased 21.76% in samples having 10mm length of kenaf fibre.
Wiley- Polymer composites, 2017
Environment friendly high strength electrical insulating material was developed using fibrillated... more Environment friendly high strength electrical insulating material was developed using fibrillated sisal and epoxy resin. Coarse sisal fibers were fibrillated into fibrils using mechanical disintegration. Fibrillated fibers provided a high strength, renewable, light weight dielectric variant reinforcement to epoxy resin. Different weight fractions (10–35%) of Agave sisalana fibrils were thoroughly mixed with epoxy resin system to develop composites. Chemical treatment was employed to improve the surface as well as chemical composition of sisal fibril to enhance mechanical strength and electrical insulating properties of composite. Chemical treatment of fibrils improved the tensile strength from 47.4 to 51.99 MPa at 35 wt % loading of sisal fibril in epoxy composite. A few important predictive models namely rule of mixture, Halpin–Tsai, Nielson Chen and Manera model were compared with the experimental values obtained in this present study. Nielson Chan model predicted the experimental data most accurately with an average relative error of 15.82%. Similarly the dissipation factor touched a level of 0.097, thereby indicating good insulation properties of composite. The tests were conducted at lower frequency range to higher frequency range 1– 10 kHz and the composite material exhibited stability at high frequency range as compared to low frequency range. POLYM. COMPOS., 2017.
VBRI Press, Sweden, 2018
Environment friendly electrical insulation material was developed using bio based rectangular cro... more Environment friendly electrical insulation material was developed using bio based rectangular cross sectioned sisal fibrils as reinforcement. High content cellulose base fibrils fibrillated by mechanical disintegration method into macro and micro fibrils from coarse sisal fibre. This fibrils were randomly distributed in polymer matrix. These composites were characterized in term of electrical, mechanical and thermal properties to investigate the stability for high strength electrical insulation materials. Excellent mechanical properties were observed. Tensile, flexural and impact strength of composites at 40 wt. % fibril loading improved by 151.34, 197.43 and 360.07 % as compared to unsaturated polyester resin. A few micro-mechanical models were compared with the experimental values. Nielson-Chen Model predicted the experimental data most accurately. The electrical properties of surface modified sisal fibril composites improved significantly in higher frequency. DSC analysis showed that the decomposition temperature of composite was higher, around 22°C than that of the polyester resin. Thermal degradation reduced and was observed in the range of 83-87% of fibril composites as compared to 97% of resin. Fibril composites are highly sensitive to electrical frequency and exhibit excellent electrical insulation property at 20 kHz. Alkali treated fibril based composites resulted an environment friendly thermally stable, high strength insulation material. Copyright © 2018 VBRI Press.
Wiley- Polymer composites, 2017
A novel hybrid composition of sisal fibrils and kenaf fibers has been introduced first time as re... more A novel hybrid composition of sisal fibrils and kenaf fibers has been introduced first time as reinforcement in composite preparation for the environmental friendly high strength electrical insulation applications. Hybrid reinforcement was increased from 10 to 40 wt% in unsaturated polyester resin. The sisal fibril used in this study was extracted from sisal fiber. Alkali treatment was employed and FTIR analysis was done to study its effect on sisal fibrils and kenaf fibers. A positive hybridization effect was observed for the composites. Hybrid composite showed 24 and 18% increase in tensile strength, 30 and 36.4% increase in flexural strength, and 196.3 and 196% increase in impact strength as compared to the composites having same loading of 40 wt% with sisal fibrils and kenaf fibers, respectively. Scanning electron microscopy of the fractured mechanical testing samples was carried out to understand the nature of fibril/fiber/matrix interface. Electrical characterization showed high electrical insulation capability of the hybrid composites. Thermal stability of hybrid composites was also found higher than sisal fibrils and kenaf fibers reinforced composites. A comparative study of properties of sisal fibril/kenaf fiber reinforced hybrid polyester composites with various single and hybrid fiber composites is done. It has been concluded that the developed novel hybrid composite has the potential to replace various existing natural and synthetic fiber composites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers
VBRI Press, Sweden, 2017
Randomly distributed kenaf fibre with varying length (5-50mm) and weight fractions (25-40%) were ... more Randomly distributed kenaf fibre with varying length (5-50mm) and weight fractions (25-40%) were used to reinforce epoxy resin to prepare environment friendly composites. Effect of fibre length with constant fibre loading on dynamic mechanical properties was studied and its effect on storage modulus, loss modulus and damping factor were investigated. Kenaf fibres were also subjected to alkali treatment to improve interaction with the epoxy resin. The mechanical properties of composites improved with the length and loading of fibres. Tensile strength, flexural strength and impact strength of composites at 40 wt% of fibre reinforcement improved by 46, 51 and 97% as compared to the composites containing 25 wt% of kenaf fibre. It was also observed that fibre folds developed during mixing became significant factor which limited the improvement in mechanical strength of kenaf epoxy composites. A few important predictive models namely rule of mixture, Haplin-Tsai, Nielson Chen and Manera models were compared with the experimental values obtained in this present study. Manera model predicted the experimental data most accurately. Alkali treatment improved the interface and its outcome reflected in the improved modulus that increased 21.76% in samples having 10mm length of kenaf fibre.
Wiley- Polymer composites, 2017
Environment friendly high strength electrical insulating material was developed using fibrillated... more Environment friendly high strength electrical insulating material was developed using fibrillated sisal and epoxy resin. Coarse sisal fibers were fibrillated into fibrils using mechanical disintegration. Fibrillated fibers provided a high strength, renewable, light weight dielectric variant reinforcement to epoxy resin. Different weight fractions (10–35%) of Agave sisalana fibrils were thoroughly mixed with epoxy resin system to develop composites. Chemical treatment was employed to improve the surface as well as chemical composition of sisal fibril to enhance mechanical strength and electrical insulating properties of composite. Chemical treatment of fibrils improved the tensile strength from 47.4 to 51.99 MPa at 35 wt % loading of sisal fibril in epoxy composite. A few important predictive models namely rule of mixture, Halpin–Tsai, Nielson Chen and Manera model were compared with the experimental values obtained in this present study. Nielson Chan model predicted the experimental data most accurately with an average relative error of 15.82%. Similarly the dissipation factor touched a level of 0.097, thereby indicating good insulation properties of composite. The tests were conducted at lower frequency range to higher frequency range 1– 10 kHz and the composite material exhibited stability at high frequency range as compared to low frequency range. POLYM. COMPOS., 2017.