Concept:Adhesive joint performance relies on two distinct force systems: adhesion (interfacial forces between unlike molecules) and cohesion (internal forces between like molecules).
Formula / Reaction:$$\text{Joint Failure Modes: } \text{Adhesive (Interfacial)} \text{ vs. } \text{Cohesive (Internal)}$$
Solution:- Adhesion: The attractive forces (chemical bonds, van der Waals, mechanical interlocking) holding the adhesive to the adherend surface.
- Cohesion: The internal intermolecular forces holding the bulk adhesive polymer matrix together.
Why other options are incorrect:- Option A: Inverts the definitions of the two phenomena.
- Option B: Both adhesion and cohesion operate in permanent and semi-permanent joints.
- Option D: Adhesion often involves secondary van der Waals forces and hydrogen bonding, not solely covalent bonding.
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