Abstract
M.Sc. (Chemistry)
This study evaluates the use of low density polyethylene (LDPE)/ethylene vinyl alcohol (EVOH) blend as a tie-layer in multi-layer film construction for packaging application. Compositions of LDPE and EVOH blends were varied from 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80 and 10/90 in order to identify a suitable blend to be used as a tie-layer. These blend ratios were melt-compounded by a co-rotating twin screw extruder. Characterization techniques such as scanning electron microscopy (SEM), Instron tensile tester, Charpy impact tester, rheometer, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), heat deflection temperature (HDT) and melt flow index (MFI) were used to identify blends with desirable properties. SEM morphologies showed that LDPE and EVOH formed phase separated structures which indicated that the blends are immiscible. In 90/10 and 80/20 LPDE/EVOH blends, EVOH formed droplets within the LDPE matrix. Co-continuous morphologies were seen on 70/30, 60/40 and 50/50 LDPE/EVOH blends while LDPE formed mixture of droplets and rod-like structures in blend ratios containing high contents of EVOH. Tensile measurement showed that modulus of the blends increased with increasing EVOH content. The moduli were designated as region I, II and III and were related to the dispersion of the phases in the blends. Blend of 90/10 LDPE/EVOH had a slight improvement in modulus when compared to neat LDPE. Furthermore, the elongation at break and impact resistance of this blend were higher than those of other blend ratios. Rheological studies were conducted to study the viscosity as a function of shear rate and confirmed that neat LDPE present higher viscosity than neat EVOH. Interestingly, 80/20 LDPE/EVOH blend showed higher viscosity than neat LDPE and...