Optimising surface interactions with poly(ethylene) blends through the use of functional additives

Abstract The aim of the present study was to enhance the surface hydrophilicity, measured in terms of apparent surface free energy values, of low-density poly (ethylene) (LDPE) and poly (ethylene-block-methylacrylate) (PE-b-PMA) copolymer blends. In order to achieve this, compounds of these polymers were produced by various methods, namely: twin screw and blown film extrusion processes; injection moulding, and; compression moulding. Bulk and surface properties were characterised by: X-ray photoelectron spectroscopy (XPS); capillary rheology, and; surface free energy measurements. An increase in measured surface free energy, and therefore interactions, was successfully achieved by engineering high concentrations of the dispersed PE-b-PMA phase under conditions where the phase continuity and shear rates led to the diffusion of the block copolymer towards the LDPE surface. The PMA mole fraction at the surface and its properties were found to be critically dependent on a number of factors, including: the additive concentration; the shear rate, and; the cooling rate applied during processing stages. Specifically, the hydrophilicity and hence the reactivity, of the polymer blends incorporating 30 wt% of PE-b-PMA, processed by compression moulding, matched the data obtained for the pure copolymer.