Improved adhesion for thermoplastic polymers using oxyfluorination
Industrial applications of thermoplastic polymers are often limited by their poor adhesion properties. In this work the effect of surface oxyfluorination on the adhesion properties was investigated for polyethylene (PE), polyoxymethylene (POM), polybutylene terephthalate (PBT) and polyamide 6 (PA6). The adhesive joint strength was quantified using lap-shear tests. These results were correlated with the changes in the chemical composition of the surface, determined by X-ray photoelectron spectroscopy (XPS), in the surface free energy, measured by the contact angle method, and in the topography, using white-light confocal microscopy. The adhesive strength is strongly improved for all four polymers, but the degree of this increase depends on the polymer type. The surface free energy shows a similar trend for all four polymers. A high surface free energy exceeding 50 mN/m was observed after oxy-fluorination, whereby the polar component was strongly predominant. Surface topography measurements show no significant increase of the surface roughness. So the effect of oxyfluorination results primarily in increased wettability and polarity, due to changes of the chemical composition of the surface. XPS measurements confirm the integration of fluorine and oxygen groups in the polymer chain, which correlates with the increased polarity.
The effect of fluorination on adhesion to polyethylene
Abstract Low density and high density polyethylenes have been treated with fluorine/nitrogen or fluorine/oxygen/nitrogen mixtures at atmospheric pressure. Changes in adhesion caused by the pretreatments have been determined using a composite butt test. Changes in chemistry have been examined using X-ray photoelectron spectroscopy, Fourier transform infra-red analysis and surface free energy measurements.
Gas transport properties of surface fluorinated poly (vinyltrimethylsilane) films and composite membranes
Abstract The surface fluorination of both thick isotropic films and composite membranes formed from poly (vinyltrimethylsilane) (PVTMS) is described. For films ranging in thickness from 23 to 220 μm, fluorination treatment reduced the permeability coefficients for the gases N 2 , O 2 , CH 4 , Kr and Xe while the permeability of He was not affected. The ideal selectivities for He, CO 2 , Kr and Xe relative to N 2 or CH 4 were increased, but the ratio for the O 2 /N 2 pair remained unchanged. Repeated fluorination at increasingly harsh fluorination conditions progressively lowered the permeability and increased the selectivities still further. Effective diffusivity coefficients for the entire treated film were found to be more responsive to fluorination than the solubility coefficients. For composite membranes, comprising a thin (∼ 0.5 μm) selective layer of PVTMS, two sets of fluorination conditions were considered: varible treatment time at a constant fluorine feed concentrations of 0.02% and different feed concentrations at a constant treatment time of 2 min. In the absence of fluorination damage, the selectivity generally increased as a function of treatment time while the permeance ( P / l ) was reduced. Fluorination damage to some membranes caused a decrease in both selectivity and permeance, but these defects could be caulked by applying a surface layer of poly (dimethylsiloxane).