Poly(ethylene-graft-ethylene oxide) Preparation and Properties in Polymer Blends

Sammanfattning: This thesis describes the preparation, characterisation and properties of poly(ethylene-graft-ethylene oxide) (PE-PEO). The grafting reaction was carried out with the grafting onto method using the carboxylic acid groups of poly(ethylene-co-acrylic acid) (PEAA) as reactive sites in an esterification reaction with poly(ethylene oxide) mono-methyl ethers (MPEO) of varying molecular weights: 750, 2000 and 5000. The copolymers were characterised by FTIR and NMR. The crystalline properties was analysed using DSC and X-ray diffraction The large difference in polarity between PE and MPEO result in strongly amphiphilic and surface active copolymers. The copolymers exhibited a micro-phase-separated morphology with two crystalline phases. The surface activity of the PE-PEO graft copolymers was utilised for surface modification of PE. Films of PE and PE-PEO blends, prepared by solvent casting and by compression moulding of melt-mixed blends, had high accumulation of copolymers in the surface region. The surfaces were characterised by water contact angles and X-ray photoelectron spectroscopy (XPS). The compatibilizing effect of PE-PEO graft copolymers in blends of PE and PA-6 was investigated. The copolymers are useful as compatibilizers, in this system, due to the partial miscibility of PEO in PA-6. Blends were prepared by extrusion in a co-rotating twin-screw extruder and by melt mixing in a Brabender Plastograph. The morphology of the blends was investigated using scanning electron microscopy (SEM). The addition of the graft copolymer PE-PEO2000 to the blends reduced the size and narrowed the size distribution of the dispersed phase. The adhesion between the phases was also significantly improved. Furthermore, the mechanical properties of the PE/PA blends increased upon the addition of copolymers. In contrast, the copolymer PE-PEO750, with shorter MPEO grafts and higher grafting density, had no effect of the blend morphology.