Adhesion promotion of poly(phenylene sulfide) to aluminum treated with silane coupling agents.

This work seeks a suitable silane coupling agent for the bonding of poly(phenylene sulfide) (PPS) to aluminum surfaces. Candidate silanes are selected on the basis of the thermodynamic compatibility of the organofunctional group of the silane with the polymer, as expressed by the (negative) Gibbs free energy of mixing for equimolar pseudo-solutions of the organofunctional group of the silane and the repeat units of the polymer, (-ΔGm0.5). The latter is calculated using the group contribution modified UNIFAC (Dortmund) method. Samples prepared with polymer bonded to silane-modified aluminum surfaces are investigated using a 90-degree peel test. An aromatic sulfide silane is predicted both to yield optimum compatibility with the polymer and is found to produce a 12-fold enhancement of adhesion (the maximum among the systems tested) over the case in which the aluminum substrate was untreated. The extent of the correlation between the compatibility parameter and the measured practical adhesion, however, is limited by several factors, including the unavailability of a wide range of candidate silanes and the incompleteness of the current UNIFAC parameter database. [ABSTRACT FROM AUTHOR]