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Dwivedi M.,Indian Institute of Technology Delhi | Dwivedi M.,Defence Research and Development Organisation | Alam S.,Defence Materials and Stores Research | Ghosh A.K.,Indian Institute of Technology Delhi
Journal of Thermoplastic Composite Materials | Year: 2011

Organoclay (Cloisite 30B)-reinforced polyetherimide (PEI) and pristine nanoclay (K10)-reinforced PEI nanocomposite films were made by solution casting process with 0.5, 1.0, 2.0, and 3.0 wt% values of nanoclay. Scanning electron micrographs showed that Cloisite 30B was uniformly dispersed in PEI/Cloisite 30B nanocomposites. Glass transition temperature (T g) of PEI/Cloisite 30B nanocomposites was observed to be higher than those of neat PEI and PEI/K10 nanocomposites. T g remained unchanged for all wt% values of Cloisite 30B, whereas T g of PEI/K10 kept on reducing with increasing values of the content of K10. Wide angle X-ray diffraction and transmission electron micrographs showed intercalation and exfoliation, of Cloisite 30B, which restricted the diffusion of heat through silicate layers to achieve high thermal stability of PEI/Cloisite 30B nanocomposites over PEI/K10 nanocomposites in thermogravimetric analysis and isothermal aging. © 2010 The Author(s). Source


Dhanalakshmi J.P.,k-Technology | Pitchaimari G.,k-Technology | Alam S.,Defence Materials and Stores Research | Vijayakumar C.T.,k-Technology
High Performance Polymers | Year: 2014

Structurally diverse bispropargyl ethers (BPEs) using resorcinol, quinol, 4,4-dihydroxy biphenyl, bisphenol-A, 4,4-dihydroxy diphenyl ketone, 4,4-dihydroxy diphenylsulphone, trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were synthesized, and it was separately blended with 4,4-bismaleimido diphenyl methane (BMIM) in mole ratios (0.5:0.5). The structural characterizations of the materials are carried out using Fourier transform infrared and nuclear magnetic resonance studies. Differential scanning calorimetric analysis shows that the difference in the melting characteristics and decrease in the curing window for different BPEs were caused by the incorporation BMIM. Addition of BMIM to BPEs reduces the heat liberated during the thermal curing. The curing kinetics is investigated using Flynn-Wall-Ozawa, Vyazovkin and Friedman methods. Amongst the various BPEs investigated, the activation energy (Ea) values obtained from spirobiindane BPE (SPIPE) behaves entirely in a different manner compared to all other materials investigated. The apparent Ea values for SPIPE was observed to increase with increasing extent of reaction up to 0.2-0.5 and then the Ea values decrease with increasing extent of reaction up to 0.55-0.8. The Ea for the polymer blends obtained by the incorporation of BMIM with different BPEs shows nearly linear increase in the Ea value, and the rate of increase is influenced by the structure of the aromatic spacer present in between the propargyl groups. © The Author(s) 2014. Source


Kurahatti R.V.,Basaveshwar Engineering College | Surendranathan A.O.,National Institute of Technology Karnataka | Srivastava S.,Defence Materials and Stores Research | Singh N.,Defence Materials and Stores Research | And 2 more authors.
Materials and Design | Year: 2011

This paper discusses the friction and dry sliding wear behaviour of nano-zirconia (nano-ZrO2) filled bismleimide (BMI) composites. Nano-ZrO2 filled BMI composites, containing 0.5, 1, 5 and 10wt.% were prepared using high shear mixer. The influence of these particles on the microhardness, friction and dry sliding wear behaviour were measured with microhardness tester and pin-on-disc wear apparatus. The experimental results indicated that the frictional coefficient and specific wear rate of BMI can be reduced at rather low concentration of nano-ZrO2. The lowest specific wear rate of 4×10-6mm3/Nm was observed for 5wt.% nano-ZrO2 filled composite which is decreased by 78% as compared to the neat BMI. The incorporation of nano-ZrO2 particles leads to an increased hardness of BMI and wear performance of the composites shows good correlation with the hardness up to 5wt.% of filler loading. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms. © 2011 Elsevier Ltd. Source

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