Contact deformation behavior polymers

Viscoelastic polymers essentially dominate the multi-billion dollar adhesives market, therefore an understanding of their adhesion behavior is very important. Adhesion of these materials involves quite a few chemical and physical phenomena. As with elastic materials, the chemical interactions and affinities in the interface provide the fundamental link for transmission of stress between the contacting bodies. This intrinsic resistance to detachment is usually augmented several folds by dissipation processes available to the viscoelastic media. The dissipation processes can have either a thermodynamic origin such as recoiling of the stretched polymeric chains upon detachment, or a dynamic and rate-sensitive nature as in chain pull-out, chain disentanglement and deformation-related rheological losses in the bulk of materials and in the vicinity of interface. 

Such information offers an opportunity to study details of the fibrillation mechanism. The fibers formed by stretching the spherulitic polymer representing nothing other than ribbon formations plastically deformed and oriented towards the mechanical stress that is released by comparatively weak mutual interconditions existing in an earlier formation (Figure 3). This behavior points to the existence of some weak surfaces in the crystalline polymers. Elements of the super-molecular structure detached by action of the external mechanical forces can slide on the weak surfaces. Evidence for the strain-destruction relationship must come from studies of the modification of the contact surfaces of two neighboring spherulites under mechanical stress. 

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