Questions and Answers
What is wettability?
Measure of the affinity of a liquid for a solid as indicated by spreading a drop.
Complete wetting occurs at a contact angle of 180 degrees.
False
What promotes adhesion between two surfaces?
Interfacial force of attraction between molecules or atoms.
An adherend is a material substrate bonded to another material by means of an _________.
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Which of the following defines surface tension?
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What is viscosity?
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What type of stress develops within a material when an external force is applied?
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Plastic materials behave like rigid materials until a certain amount of strain is applied.
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Study Notes
Wettability and Surface Properties
- Wettability indicates a liquid's affinity for a solid, measured through the contact angle of a liquid drop.
- Contact angle of 180° signifies no wetting, while 0° indicates complete wetting.
- Surface energy is the excess energy at a material's surface compared to its bulk, influenced by attraction forces among surface molecules.
Adhesion and Bonding
- Adhesion describes the attraction between two contacting surfaces, crucial for material bonding.
- Micromechanical bonding relies on interfacial forces, enhanced when an adhesive penetrates a rough surface.
- Bonding can occur via chemical forces, mechanical interlocking, or a combination of both.
Surface Tension and Cohesion
- Surface tension is the tendency of fluid surfaces to minimize area, resulting from molecular attraction imbalances at the surface.
- Cohesion refers to the attraction between molecules of the same species, influencing liquid properties.
Terminology in Materials Science
- Stress is defined as force per unit area within a material under external load.
- Strain quantifies deformation as the change in length divided by the original length.
- Shear stress measures time-dependent plastic strain in a solid under consistent load.
Viscosity and Flow Behavior
- Viscosity is the measurement of a fluid's resistance to flow; it describes how substances deform and flow.
- Rheology studies the flow characteristics indicating how materials behave under various forces.
- Newtonian fluids have a consistent viscosity, while non-Newtonian fluids exhibit varied flow properties:
- Dilatant: Flow decreases with increased strain until reaching a constant.
- Pseudoplastic: Flow increases with increased strain.
- Plastic: Resembles rigid material until a minimum strain is applied.
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Description
Explore the key properties of dental materials in this quiz based on Lecture 2. Topics include wettability, solid surfaces, and liquid interactions. Test your understanding of how these principles affect dental practice and material selection.
