Fracture Energetics and Surface Energetics of Polymer Wear

Polymer wear can take place in various modes, e.g., adhesive, abrasive, transfer, fatigue, and tribo-chemical. In reality, several mechanisms can also operate simultaneously. If impaction is involved, an impact wear can be the chief mechanism. The predominance of any one type of wear can be influenced by the form of polymers, e.g., thermoplastics, elastomers or composites. This paper is to discuss polymer wear on the basis of energetics. For adhesive wear, surface energetics are the dominant factor. For example, the work of adhesion of the two counterfaces has been correlated with wear rate. For abrasive wear, fracture energetics can dictate the crack formation and the intensity of wear. Depending on the ductility of polymers, fracture energy Gc or Jc of the material can directly affect the wear. A severe tribo-chemical wear could involve the generation of energetic particles, e.g., free radicals, electrons, positive ions, etc. For polymer transfer, surface polarity has been shown to determine the direction of transfer. Fatigue wear under a cyclic load can involve fracture energy of the material. We found that for fatigue resistance, fracture energy is the most important property. Moreover, most wear mechanisms eventually lead to fatigue wear of polymers.