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Adhesion is a surface phenomenon. A surface's texture, porosity, and flexibility affect the adhesive strength of a plastic joint. Ditto for any contaminants such as mold release agents, plasticizers, or other resin formulations that migrate to the surface.
Surface energy also influences adhesion. It defines the ability of adhesives and pressure-sensitive adhesive (PSA) tapes to "wet out" plastic surfaces to allow adhesion. Surface wet out refers to how well a liquid or viscoelastic solid flows and intimately covers a surface. Maximum adhesion develops when the adhesive or viscoelastic PSA tans thoroughly wets out the surface to be bonded. The greater the wet out, the better the surface coverage and the greater the attractive forces between adhesives and plastic surfaces. Surfaces with high surface energy bond more readily because they are easier to wet with conventional adhesives and tapes than are lowenergy surfaces.
Surface energy is a relative phenomenon. To gauge the effects of surface energy on adhesion, one must compare the surface energy of a liquid or viscoelastic solid to that of a solid surface. A liquid or viscoelastic solid possessing a...