O. Heuschling et al., ADHESION PROPERTIES OF POLYPROPYLENE TO ALUMINUM - INFLUENCE OF POLYMER GRAFTING AND THERMAL HISTORY, Journal of adhesion science and technology, 8(1), 1994, pp. 53-65
Polypropylene (PP) powder was hot-pressed between aluminium foils and
the adhesion was examined by a peel test. A measurable adhesion was ob
served with the grafted polymer. By grafting 3-azido-sulphonyl benzoic
acid onto PP, the chemical composition of the adhesion failure zones
was monitored by X-ray photoelectron spectroscopy, using N and S as ma
rkers. Adhesion was improved by purifying the grafted polymer before p
ressing against aluminium. Purification eliminates ungrafted polar mol
ecules which form a weak boundary layer at the interface with the Al a
dherend. Adhesion was also very much dependent on the thermal history
of the hot-pressed aluminium/polypropylene/aluminium laminates. Quench
ing increased the peel strength dramatically, whereas annealing after
quenching decreased it. This is interpreted in terms of the structure
and ductility of the polymer. The adhesion of PP to aluminium thus dep
ends on the interplay between the affinity of grafted macromolecules w
ith the adherend, the formation of a weak boundary layer, and the bulk
properties of the polymer.