Date of Award

2005

Document Type

Thesis

Degree Name

Master of Science in Material Science Engineering (MSMatSE)

Department

Materials Science

First Advisor

Dr. Abdel-Hamid I. Mourad

Second Advisor

Dr. Tarek M. Madkour

Third Advisor

Dr. Ahmed A. Soliman

Abstract

The thermal and mechanical characteristics of thermally treated and untreated pure polyethylene (PE), pure polypropylene (PP) and their blends were investigated. Injection-moulded samples containing 100:00,75:25,50:50,25:75 and 00:100 weight percentage of PE:PP, were prepared and thermally treated at 100°C for 0, 2, 4, 7, 14 days. The treated samples were subjected to differential scanning calorimetry (DSC), thermogravimetry (TG & DTG), infrared spectral analysis (IR) and tensile tests in order to study the effect of thermal treatment and blending ratios on their thermal and mechanical properties. The results indicate that addition of PE causes the melting temperature (Tm) of PP (115 °C) to decrease in both untreated and thermally treated blends by 3.8 °C and 3.0-4.8 °C, respectively. The results indicate also that at least 2 days of thermal aging treatment for pure PE and PP samples has caused the polymer to exhibit a new melting transition at 101°C and 103 °C, respectively, which persists throughout the aging treatment up to 14 days. Their blends show intermediate values. This newly observed melting transition is possibly caused by the reorganization and realignment of polymeric segments causing them to crystallize and melt upon heating. It is also observed that addition of PE to PP decreases the heat of fusion and percentage crystallinity of the later. The heat of fusion has been found to decrease by 15.67 J/g for the untreated blend and by, as much as, 18.71 J/g for treated blends. Moreover, the degree of crystallinity has reduced by 69.8 % for the untreated blend and by about 75.7 % for the treated blends. The IR spectra of all blends at different aging times do not show any degradation products which indicates a chemical stability of these blends over the range of the oven treatment conditions. The initial decomposition temperature (Td(1%)), final decomposition temperature (Td(99%)), maximum decomposition rate temperature (Tmax), activation energy (kJmol-1) activation enthalpy (kJmol-1) and the order of the decomposition reaction (n) were calculated from the TG plots and discussed in terms of blending ratios and aging times. In nitrogen atmosphere, all blends start to decompose at no less that 380 °C, where as in air this was found to be 280 °C. This reflects the thermal stability of the various blends in the operating temperature range of most industrial applications.

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