TABLE OF CONTENTS Polymer interfaces are ubiquitous. They play a critical role in determining the properties, reliability, and function of a broad range of materials. For example, polymer melt processing via injection molding (for plastic auto parts) and extrusion (for plastic pipe) creates many interfaces in the form of internal weld lines where the fluid fronts coalesce and weld. Compression molding and sintering (of artificial hip joints) require the coalescence of pellets or powder when their surfaces contact in the mold. Drying of latex paints and coatings (Chapter 8) entails a very large number of interfaces per unit volume, because the relatively tiny (~1000- ) latex particles interdiffuse to form a continuous film. Construction of composites with thermoplastic matrices (aircraft bodies) requires the fiber-filled laminates to weld by an interdiffusion process at the interface. Welding of two pieces of polymer by thermal or solvent bonding is a commonly encountered example of strength development at a polymer polymer interface; tack between uncured rubber sheets during auto tire manufacture is an important example of this kind of welding.
Numerous examples of symmetric interfaces exist where the same polymer occurs on both sides of the interface. In contrast, rubber toughening of glassy polymers (bulletproof glass) requires that the interface formed by the rubber particle with the glass (Plexiglas ) matrix be sufficiently strong to promote stable energy dissipation. The rubber/Plexiglas is an example of an asymmet ric interface where two different polymers are joined. Asymmetric or dissimilar interfaces come about when polymers...
