Molecular Adhesion And Its Applications

Molecular Adhesion and Its Applications

This book sets out to describe the importance of adhesion in our Universe. Although we believe that the universe is expanding and flying apart, we can also see that the Earth and its parts are sticking together with great tenacity. Gravitation explains part of this attraction on earth, but is insufficient to explain why adhesives stick jumbo jets together or why our bodies do not fall apart. To understand the strong attractions between earthly matter we must introduce the idea of molecular adhesion; the fact that all molecules attract each other with a considerable force. This idea at first seems paradoxical because we can identify situations where adhesion is very strong, for example when paint sticks to a surface, but we can also see cases where adhesion is very weak, when sand flows through an hour glass. The objective of the book is to provide explanations for these apparently perverse effects.

Molecular Adhesion and Its Applications

At the beginning of the twentieth century, engineers and technologists would have recognized the importance of adhesion in two main aspects: First, in the display of friction between surfaces — at the time a topic of growing importance to engineers; the second in crafts requiring the joining of materials — principally wood—to form engineering structures. While physical scientists would have admitted the adhesive properties of glues, gels, and certain pastes, they regarded them as materials of uncertain formulation, too impure to be amenable to precise experiment. Biological scientists were aware also of adhesive phenomena, but the science was supported by documentation rather than understanding. By the end of the century, adhesion and adhesives were playing a crucial and deliberate role in the formulation of materials, in the design and manufacture of engineering structures without weakening rivets or pins, and in the use of thin sections and intricate shapes. Miniaturization down to the micro- and now to the nano-level of mechanical, electrical, electronic, and optical devices relied heavily on the understanding and the technology of adhesion. For most of the century, physical scientists were aware that the states of matter, whether gas, liquid, or solid, were determined by the competition between thermal energy and int- molecular binding forces. Then the solid state had to be differentiated into crystals, amorphous glasses, metals, etc. , so the importance of the molecular attractions in determining stiffness and strength became clearer.

Molecular Adhesion and Its Applications