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dc.contributor.authorBashir, Farrukh-
dc.description.abstractPolymer composites with excellent electrical conductivity and dielectric properties are considered as potential candidates for energy storage devices and given preference over their ceramic counter part because of ease in processing, enhanced flexibility, low cost and high breakdown voltage. Composites of poly methyl methacrylate (PMMA) were prepared by solution casting method using pristine MWCNTs and modified MWCNTs, respectively. The composite of pristine MWCNTs with PMMA was named as MWCNTs/PMMA. The surface modification of MWCNTs was carried out by four different reagents to obtain four types of fillers. In the first type of modification, 3-(N, N-dimethyloctadecyl ammonio) propanesulfonate known as Zwitterionic surfactant (ZIS) was attached at surface of MWCNTs to have ZIS-MWCNTs and this filler was used to prepare composite with PMMA i.e., ZIS-MWCNTs/PMMA. In second type, 3-aminopropyltriethoxysilane (APTES), a cross linker, was attached with MWCNTs to yield APTES-MWCNTs which was combined with PMMA to obtain APTES-MWCNTs/PMMA. In the third case, dodecyl benzene sulphonic acid (DBSA), an anionic surfactant, was adsorbed at the surface of MWCNTs to form MWCNTs-DBSA filler and then combined with PMMA for developing DBSA-MWCNTs/PMMA. In the fourth case, polyaniline (PANI), a conducting polymer, was grown at the surface of MWCNTs to have PANI-MWCNTs and then introduced in PMMA to prepare PANI-MWCNTs/PMMA. These composites were characterized by UV-Vis and Fourier transform infrared spectrophotometers, x-ray diffraction and scanning electron microscopy for structural and morphological studies. Electrical conductivity and dielectric constant were measured by inductance, capacitance and resistance meter whereas thermal stability was obtained by thermal gravimetric analysis. In case of pristine or unmodified MWCNTs, the MWCNTs/PMMA composite showed band gap energy of 3.7 eV which is lower than pristine PMMA i.e., 4.31 eV. Electrical conductivity observed for pristine PMMA was 8.3 x 10-9 S/cm which was increased to 1.18 S/cm upon addition of 3.57 wt. % of MWCNTs and became constant after 10 wt. % of MWCNTs with 18 S/cm. Percolation threshold obtained for MWCNTs/PMMA was 0.5 wt. % with dielectric constant of 23 and char yield of 2.67 % at 590 oC. Whereas, the value of dielectric constant for pristine PMMA was 2.4 with char yield of 0.3 % at 590oC. In first case of modified MWCNTs, the ZIS-MWCNTs/PMMA composites showed the band gap energy of 3.08 eV with percolation threshold of 0.005 wt. % of MWCNTs. An increase in conductivity of PMMA from 10-9 S/cm to 10-1 S/cm was observed on addition of less than 1 wt. % of MWCNTs and reached to 25 S/cm at 9 wt. % of filler. Maximum dielectric constant for ZIS-MWCNTs/PMMA was 12 with high thermal stability i.e., 7 % char yield at 590 oC. In second case of APTES-MWCNTs/PMMA composites, the value of band gap energy was 4.22 eV. Low percolation threshold i.e., 0.05 wt. % with 0.03 S/cm electrical conductivity at 2 wt. % of MWCNTs were observed for APTES-MWCNTs/PMMA. On comparison with pristine PMMA and MWCNTs/PMMA composites, APTESMWCNTs/PMMA demonstrated significant improvement in the dielectric constant i.e., 40 at 1.6 wt. % of MWCNTs and high thermal stability of 6.7 % char yield at 590 oC. In third case of DBSA-MWCNTs/PMMA composites, the band gap energy was 3.42 eV with 0.8 wt. % percolation threshold. Sharp transition from non-conducting to conducting behavior was obtained in DBSA-MWCNTs/PMMA composites with the maximum conductivity of 2 S/cm at 3 wt. % of MWCNTs. In case of thermal stability, DBSAMWCNTs/PMMA kept its stability with 1.6 % char yield at 590 oC. In fourth case, PANI-MWCNTs/PMMA composite showed band gap energy of 3.27 eV with conductivity of 5.6 S/cm at 2 wt. % of MWCNTs. Percolation threshold for PANIMWCNTs/PMMA was 1.3 wt. % of MWCNTs with significantly high dielectric constant of 45.6 at 2 wt. %. The char yield observed for these composites was 1.27 % at 590oC. The overall comparison of all these five types of composites provides an overview for the selection of suitable filler material for developing polymer composites of enhanced electrical features. This is indeed beneficial in developing modern microelectronic devices with improved performance and stabilityen_US
dc.description.sponsorshipHigher Education Commission Pakistanen_US
dc.publisherUniversity of the Punjab , Lahoreen_US
dc.subjectPhysical Sciencesen_US
dc.titleSynthesis of CNT-polymer composites and their electrical properties.en_US
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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