SYNTHESIS AND CHARACTERIZATION OF ALUMINA-DOPED LOW DENSITY POLYETHYLENE (LDPE/ALUMINA) NANOCOMPOSITES
SYNTHESIS AND CHARACTERIZATION OF ALUMINA-DOPED LOW DENSITY POLYETHYLENE (LDPE/ALUMINA) NANOCOMPOSITES
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Date
2016-09
Authors
ABDULRAHEEM, Aliyu
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Abstract
Nano-sized kaolin also known as alumina was synthesised by acid leaching and subsequently suspended in low density polyethylene (LDPE) to produce nano-polymer for application in electrical insulation. The alumina was prepared by acid leaching via digestion, precipitation, peptization and drying. This was subsequently used to dope the LDPE at varying compositions.
The structural properties of LDPE/Ξ³-alumina with LDPE as a host matrix were investigated by X-ray diffraction, Scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy. Intermediate LDPE/Ξ³-alumina nanocomposites were confirmed by XRD. The Sherrer equation revealed a nano crystalline size of 24.91ππ for the Ξ³-alumina at 400Β°C. SEM images also revealed a heterogeneous dispersion of nano particle layers in the LDPE matrix. Uneven dispersion of nano particles was evident due to agglomeration of alumina. The mechanical properties results which were investigated by Nanoindentation showed that the presence of alumina in the LDPE improved the Youngβs modulus and hardness of the samples. The dielectric permittivity, ππ conductivity, relaxation and electrical modulus of the composites were studied in the frequency range of 20 ππ»π§ to 180 ππ»π§, at room temperature. Addition of alumina up to about 2.5wt% resulted in an increase permittivity.
Doping of LDPE with alumina produced intermediate nanocomposites which possess excellent dielectric properties. The permittivity of LDPE has been measured to be (2.25 - 2.35) at 1 MHz and after doping in this work it was gotten as (2.85-3.47) at 100 kHz. The mechanical behaviour is practically enhanced by an increase in its hardness from 13.5 πππ to a range of (14β34 πππ) in this work while the elastic modulus is within (0.74β1.44 πΊππ).
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The prepared samples have an average dissipation factor of 0.006228 at 20 kHz. The increase in dielectric permittivity of the samples and relatively low and stable tan delta value is an indication of low loss which makes the material an efficient insulator. The pattern of variation of conductivity of LDPE/alumina with frequency is linear increment and is indicative of the semicrystalline structure of the host matrix. The relaxation behaviour showed the same pattern and have their slopes falling between β0.3593 to β0.5223. This may likely be an indication of low stress and brittle failure which is usually initiated at surface or bulk inhomogeneities that act as stress concentrator and of course which the samples (LDPE/alumina) possess. Samples doped at 2.5, 3.0 and 3.5 wt% appeared to have most optimum behaviour in that they have the lowest dielectric loss out of all the samples produced. The samples prepared within the stated ranges also have good stability with respect to elastic modulus and hardness and may therefore be considered as a good alternative electronic substrate for polymeric applications compared to others fabricated at different percentage weights
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A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DEGREE OF DOCTOR OF PHILOSOPHY (PhD PHYSICS) DEPARTMENT OF PHYSICS, FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
Keywords
SYNTHESIS,, CHARACTERIZATION,, ALUMINA-DOPED LOW DENSITY POLYETHYLENE,, (LDPE/ALUMINA),, NANOCOMPOSITES,