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Investigation of Thermal Properties of Radiation Grafted Polystyrene / Polytetrafluoroethylene (PTFE) Copolymer Films

Rais, Md Aidi (2002) Investigation of Thermal Properties of Radiation Grafted Polystyrene / Polytetrafluoroethylene (PTFE) Copolymer Films. Universiti Teknologi Petronas. (Unpublished)

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Abstract

Grafting was carried out using 7-radiation from a 60Co source at dose rates of 1.32- 15.0 kGyh"! at room temperature. The chemical structure and the crystallinity ofthe grafted PTFE films were studied by means of Fourier transform infrared (FTIR). Structural investigation of polystyrene grafted polytetrafluoroethylene) (PTFE) membranes prepared by radiation-induced grafting of styrene onto commercial PTFE films carried out by Fourier transform infrared spectrometer (FTIR) and the thermal stability of thermal gravimetric analyzer (TGA). The effect of the structural changes taking place in the film by grafting and the variation of the degree of grafting on melting temperature (Tm), glass transition temperature (Tg), heat of melting (AHm), anddegree of crystallinity was studied by using differential scanning calorimetry (DSC). Polystyrene grafted films prepared by radiation-induced grafting of styrene onto PTFE films were found to undergo considerable structural changes. The degree of crystallinity decreased upon grafted as well as deviation of the degree of grafting. The changes in melting temperature (Tm) was found to be insignificant regardless of the degree of grafting unlike glass transition temperature (Tg). The decrease in crystallinity was suggested mainly due to the effect of dilution on the original crystalline structure by incorporation of the amorphous polystyrene grafts. Furthermore based on the results and discussion and those on the original and grafted films is that the PTFE film surface undergoes structural changes in terms of chemical composition as a result of styrene grafting. The effect of grafting of polystyrene onto PTFE membrane on the thermal stability of the PTFE matrix is studied. It is found that the fluorinated-structure of the PTFE matrix has a thermal stabilityup to ~550°C followed by one-step degradation. Grafting of styrene, which led to the formation of polystyrene grafts in PTFE matrix introduces a two-step degradation pattern. The polystyrene grafts start to degrade at ~400°C and continue until ~480°C. This is followed by the degradation ofPTFE backbone, which starts at ~550°C and continues to ~680°C. Styrene, which radiochemically grafted onto PTFE films leading to the formation of polystyrene grafted PTFEfilms. The grafted films were found to be very stiff compared to the original PTFE fimi.From DSC thermograms, the high value of Tg compared to that reported in literature (>20°C) [10,11], thus indicates that commercial PTFE film contains certain additive (filler such as glass fibres) that decreases the polymer chain mobility and gives rise to Tg. The incorporation of polystyrene side chain grafts into PTFE film caused a shift in the Tg of the grafted film to higher temperature while significant changes took place in Tm. Grafting of styrene were found to reduce the heat of melting and the degree of crystallinity of PTFE films. In addition, the degree of crystallinity decreased in the original PTFE film to the grafted films. IV

Item Type: Final Year Project
Academic Subject : Academic Department - Mechanical Engineering - Materials - Engineering materials - Polymers - Polymerisation
Subject: T Technology > TJ Mechanical engineering and machinery
Divisions: Engineering > Mechanical
Depositing User: Users 2053 not found.
Date Deposited: 26 Sep 2013 12:47
Last Modified: 25 Jan 2017 09:47
URI: http://utpedia.utp.edu.my/id/eprint/6747

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