Лако-красочные материалы — производство

Adhesive bonds with polymer materials generally achieve a good durability, provided that the adherent material contains polar groups or (as in the case of nonpolar polyethylene, polypropylene or similar polymers) polar groups have been generated by oxidation via chemical or physical surface preparation (see Section 6.2) that also improves the wettability. Media that diffuse into the bond may impair the strength. Based on common tables of resistance, the correct selection of the media to which the bonded joints are exposed prevents the media from irreversibly damaging the adherents and the adhesive. The changes in strength remain calculable because they can be determined in advance based on material characteristics. The adhesion zone, which can be critical in the case of inorganic materials (see above), is rather noncritical at long-term loading in the case ofbonded plastic material; this is because, besides physical and chemical interactions, molecular diffusion between the adhe­sive and adherent apparently provides for a durable adhesion (see Chapter 3). However, this does not mean that all plastics can be bonded with all adhesives in the same way. Selection tests (strength tests without aging influence) make it possible to determine whether a plastic material can be bonded, or not. When the results are satisfactory, the durability can then generally be assumed also to be satisfactory, at least as far as modern industrial adhesives are concerned [24].

7.8