Definition and Classification of Adhesives
Definition
Adhesives are substances that can firmly bond two materials together through surface wetting, molecular diffusion, or chemical reactions.
Historical Background
The history of adhesives dates back 5,000 years to ancient Egypt, where animal glue was used in pyramid construction. The modern adhesive industry began in the 1930s with synthetic resins.
Example
Double-sided tape mounts a picture frame: peel release paper, press to wall, molecules interlock forming mechanical lock. Van der Waals forces achieve chemical adsorption.
Formula
Adhesion Strength = f(Surface Energy, Contact Area, Degree of Curing)
Core Concepts
Interface engineering: bonding through interfacial forces without changing the substrate. Must balance initial tack, holding power, and peel strength.
Extended Applications
Electronics: UV-curing for chip encapsulation (260C); medicine: biocompatible for wound closure; construction: structural for curtain walls; automotive: structural replaces welding.