Mathew Abraham

Influence of surface activated carbon nano fiber on thermo-mechanical properties of high performance polymeric nano composites

This investigation highlights the influence of plasma modified carbon nano fiber (CNF) on the various properties of poly ether ketone (PEK). CNFs were modified with oxygen plasma under low pressure to enhance the interfacial adhesion between the reinforcement and matrix. Significant changes are evident in the elemental composition of oxygen and carbon on the plasma modified CNFs as observed by X-ray photo electron spectroscopy. Based on results from compression and tensile strength, significant change in the mechanical properties of the composites is observed. Dynamic mechanical thermal analysis (DMTA) reveals that the storage modulus increases on reinforcing modified CNF in PEK. The increase in modulus is noticeable only up to 1.5% wt reinforcement of CNF, while higher percentage of reinforcement leads to decline in properties. DMTA studies also clearly shows that the dispersion of CNF is not uniform after 1.5% of CNF reinforcement. However, differential scanning calorimeter and thermo gravimetric analysis studies reveal that the thermal properties of the CNF reinforced composite do not vary significantly. Thermal conductivity results show a substantial increase in the thermal conductivity of polymeric composites on increasing the reinforcements. Transmission electron microscopy (TEM) analysis reveals that there is uniform dispersion of CNF in PEK. TEM also clearly shows that higher percentage of CNF leads to agglomeration. Physico-chemical analysis indicates that the contact angle increases on increasing the reinforcements. These findings would be highly useful to make way for PEK composites for high temperature and high strength application.

Hybrid nanocomposites based on poly aryl ether ketone, boron carbide and multi walled carbon nanotubes: Evaluation of tensile, dynamic mechanical and thermal degradation properties

Abstract In this study an attempt has been made to incorporate a radiation resistant filler like boron carbide (B4C) nanopowder along with multi walled carbon nanotubes (MWCNT) in a high performance polymer namely poly aryl ether ketone (PAEK) for potential applications in the nuclear industry. The dispersion of nanofillers in PAEK was established by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Infra red (IR) spectroscopy indicated the interaction between functionalized MWCNT (F-MWCNT) and PAEK. The optimum combination of B4C and F-MWCNT was obtained from the tensile property analysis. It was found from the dynamic mechanical analysis that the storage modulus of the composite at elevated temperature was enhanced by B4C inclusions. Mechanical damping factor spectra showed the shift of PAEK glass transition temperature to higher values due to the presence of B4C and F-MWCNT. Thermogravimetric analysis (TGA) presented the resistance offered by B4C to the degradation of PAEK especially at elevated temperatures.

Microstructure Development, Wear Characteristics and Kinetics of Thermal Decomposition of Hybrid Nanocomposites Based on Poly Aryl Ether Ketone, Boron Carbide and Multi Walled Carbon Nanotubes

In the present study a high performance polymer poly aryl ether ketone (PAEK) is reinforced with micro and nano boron carbide (B4C) and functionalized multi walled carbon nanotubes (F-MWCNT) to investigate the individual and hybrid effect of the fillers. Optical microscopy and transmission electron microscopy suggested the dispersion of micro and nano fillers respectively in PAEK matrix. The inclusion of B4C nano fillers increased the hardness of the composites which aided the wear resistance of the composites. The morphological features of the worn surface of the samples are analyzed using scanning electron microscopy. It is found from the izod impact test analysis that the impact strength of the composite enhanced by the F-MWCNT inclusion. The thermal properties of PAEK in the composites are studied using differential scanning calorimetry and it revealed dominant effect of F-MWCNT influencing the thermal transitions than the B4C particles. The kinetics of thermal degradation of various composites is analyzed using Coats–Redfern method. The positive influence of B4C in the matrix indicates that the thermal degradation is delayed due to the higher activation energy it possesses. The overall results shows that the hybrid nanocomposite exhibits better properties compared to individual micro and nano composites.

High-performance fire-resistant polymeric nanocomposite for aerospace applications:

This investigation essentially highlights development of novel high-performance fire-resistant polymeric nanocomposite with respect to its orientation towards future generation aviation. Therefore, an attempt has been made to increase thermal stability and fire resistivity of phenolic/cotton fabric reinforced polymer composite, which is desirable for aircraft interiors. There is considerable increase in adhesion characteristics of phenolic fabric reinforced polymer composite due to atmospheric pressure plasma treatment. The phenolic fabric reinforced polymer is subsequently coated with nanosized calcium silicate reinforced polybenzimidazole composite in order to increase thermal stability and fire resistance property. Thermogravimetric analysis reveals that polybenzimidazole-coated fabric reinforced polymer shows significantly better thermal stability than the uncoated phenolic fabric reinforced polymer. There is a significant increase in the limiting oxygen index characteristics of polybenzimidazole-coated fabric reinforced polymer when compared to the uncoated phenolic composite resulting in considerable improvement in fire resistivity of the polymers.

Effects of high energy radiation and thermo-chemical environments on polyetherimide composites: futuristic approach to nuclear waste storage

This research highlights the effect of radiation, chemical and thermal environments on mechanical and thermal properties of polyetherimide (PEI) composites. The tests are conducted on specimens made from PEI and PEI reinforced with modified Carbon Nano Fibre (CNF). The specimens are subjected to gamma radiation doses of 5 MGy, which is equivalent to the cumulative dose of radiation from spent nuclear fuel until the end of complete radioactivity. The exposed samples are further subjected to highly corrosive and thermal environments. Studies under transmission electron microscopy reveal that there is a uniform dispersion of modified CNF in PEI. Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA) indicate that there are no significant changes in thermal properties of PEI and PEI composite when exposed to aggressive environments. It is observed that there is a marginal loss in the tensile strength of polymeric samples when exposed to gamma radiation and thermal environments. PEI samples when subjected to alkaline corrosive environments show significant loss in the tensile strength. There is a significant decrease in the molecular weight of PEI under alkaline corrosive environments as seen from Gel Permeable Chromatography (GPC).

Feasibility of polyetherketone (PEK) composites: a solution for long-term nuclear waste storage

This investigation highlights the effect of radiation, chemical and thermal environments on mechanical and thermal properties of polyetherketone (PEK) composites and its rationale for long-term nuclear waste storage. The tests are conducted on samples manufactured using PEK and PEK reinforced with modified carbon nano fibre (CNF). The specimens are subjected to gamma radiation doses of 5 MGy, which is equivalent to the cumulative dosage of radiation from spent nuclear fuel until the radioactivity neutralises completely. Studies under transmission electron microscopy (TEM) reveal that there is a uniform dispersion of modified CNF in PEK. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicate that there are no significant changes in thermal properties of PEK and PEK composite when exposed to aggressive environments. It is observed that tensile strength of polymeric samples remains unchanged when exposed to gamma radiation and thermo-chemical environment.