Thami Chihani

Surface modification of ethylene copolymers molded against different mold surfaces. Part 2. Changes at the outermost surface

The influence of the mold surface on the surface composition of thermoplastics has been investigated. Two different random copolymers, poly(ethylene-co-acrylic acid) (EAA) and poly(ethylene-co-vinyl acetate) (EVA), with varying comonomer contents were used. Specimens were prepared in molds coated with films of perfluorinated ethylene-propylene copolymer (FEP) and of poly(ethylene terephthalate) (PET). Samples were also molded against air and vacuum. Changes in the concentration and arrangement of the functional groups at the outermost surface were studied using X-ray photoelectron spectroscopy (XPS or ESCA), Fourier transform infra-red techniques (FTIR), and contact angle measurements. The concentration of functional groups at the outermost copolymer surface depended on the nature of the surface against which the random copolymers were molded. Results are interpreted in terms of differences in surface energy between the mold surface and the copolymer. The polar acrylic acid groups in EAA increased when mo...

Surface modification of ethylene copolymers moulded against different mould surfaces-1. Surface enrichment by functional groups

A polymer surface chemical composition can be changed by the influence of different environments. Results presented from this study show that the surface of the mould influences the outermost polymer surface by enriching it with specific functional groups. This was done by moulding random copolymers against polymer films with low and high surface energies. The values presented are interpreted in terms of differences in surface energy between the mould surface and the copolymer. The random copolymers used were poly(ethylene-co-vinylacetate) (EVA) and poly(ethylene-co-acrylic acid) (EAA), both with a different comonomer content. The copolymers were moulded in contact with mould surfaces made of polymer films which were perfluorinated ethylene propylene copolymer (FEP), poly(tetrafluoroethylene) (PTFE), and poly(ethylene terephthalate) (PET). The resultant surfaces were characterized by X-ray photoelectron spectroscopy (XPS or ESCA) and contact angle measurements The surface content of acrylic acid functiona...

Surface modification of epoxy polymer with different perfluoroacids

Perfluorobutyric acid (PBA) and perfluorooctanoic acid (POA) were added to an anhydride epoxy resin in order to modify the epoxy polymer surface to achieve a higher content of specific functional groups and to improve the release properties. The resulting surfaces were analysed with X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements. If the curing of the epoxy was done against a non-polar surface (FEP and air) the perfluoroacids were concentrated at the epoxy surface. At addition levels of 1 wt % of fluorine, the concentration factor was up about 20 times at the outermost epoxy surface. FTIR analysis showed that the acid groups had reacted with the epoxy resin, thus locking the additive in the top layer. Washing with heptane and water leads to corresponding changes in surface polarity due to rearrangement in the outermost layers. Adhesive bonding with a polyurethane adhesive showed that the low molecular weight additive did not decrease the adhesive strength between the adhesive and the...

Surface properties of an anhydride-epoxy resin cured against different mould surfaces

An epoxy resin consisting of diglycidylether of bisphenol A (DGEBA) and methyltetrahydrophthalic anhydride (MTHPA) was cured against moulds with different surface characteristics: poly(ethylene terephthalate) (PET), perfluorinated ethylene propylene copolymer (FEP), and air. The epoxy surfaces were analysed using contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results presented are interpreted in terms of differences in surface energy between the surface of the mould and the epoxy resin. With PET as the mould surface, the surface content of ester groups resulting from the anhydride increased as compared to the average bulk content. With the non-polar FEP mould, the amount of ester groups decreased instead. Shear tests on overlap joints obtained by adhesive bonding with polyurethane and epoxy adhesives showed, however, a high adhesive joint strength, both for epoxy surfaces obtained with FEP as mould, and for ground surfaces with a bulk composition. The surfaces generated in PET ...