Louis H. Sharpe

The Interphase in Adhesion

Abstract The role of weak boundary layers (WBL) in determining the breaking stress of adhesive joints has been proposed to be that of a discrete surface layer of material with strength properties inferior to the bulk material from which it originated. The breaking strength behavior of various polyethylene-epoxy adhesive lap joints has been used as prima facie evidence for the presence or absence of WBL. So-called WBL in PE appear not to be removable by extraction, by abrasion or by fractionation but they seem to disappear when one uses PE as a hot-metal adhesive. We shall attempt to place the WBL matter in better perspective by discussing boundary layers in a general way; that is, evidence for their existence, what they might be where we can isolate and identify them, how they develop and how we can control their properties and, finally, how they influence joint behavior. We conclude that the WBL postulated to explain the behavior of unmodified PE is probably a fiction and that the mechanics of the compos...

Some Fundamental Issues in Adhesion: A Conceptual View

Abstract The role of interfacial interactions in determining the global response of joint systems is discussed in relation to the question of true interfacial failure and the ubiquitous occurrence of interphases. The discussion is from the point of view of systems involving adhesives, coatings and composites rather than, e.g., particle-particle or particlesubstrate systems and is strictly conceptual in nature. It is proposed that interfacial interactions, rather than directly exerting an effect on the global response of joint systems, are instead the driving force for the many and varied processes that create interphases. It is such interphases, or transition zones between phases, which affect the global mechanical response of joint systems.

Some Thoughts About the Mechanical Response of Composites

Abstract Some criticism is directed at current approaches to composite response which do not include a mechanical model of the region in the vicinity of the interface. An interphase model based on interface roughness is suggested.

The Mechanical Properties of Rubber Particles in Rubber-Reinforced Glassy Polymers

Abstract The effect of thermal stresses on mechanical properties of the rubber particle in rubber-reinforced glassy polymers is studied. It is found that the rubber particle in the glassy polymer tends to be softer than the one in its stress-free state because of thermally induced hydrostatic tension which lowers the glass temperature of the rubber particle. The analysis is applied to the case of ABS, and the results show that the shift of glass temperature is significant near the Tg of the rubber particle in its free state. The change in the mechanical properties of the rubber particle in ABS due to the shift is also analyzed.

Dr. James A. Koutsky 1940-1994

Abstract James A. Koutsky, Professor in the Chemical Engineering Department at the Univer- sity of Wisconsin, died on November 25,1994. He was born on December 1,1940, in Parma, Ohio, the son of Joseph and Marion Koutsky. Dr. Koutsky received B. S., M. S. degrees (both in Chemical Engineering) and a Ph.D. in Polymer Science, all from Case Western Reserve University.