MOD 03 - Physical Property

Property

Characteristics of substance that is observed during reaction

Why do we need to know the properties

We will be able to select the appropriate material used in specific cases

Dimensional Change

Shrinkage or expansion of a material

Thermal Dimensional Change

Change of material in its dimensions

Linear Coefficient Thermal Expansion

Expansion of material

Percolation

Penetration or forcing out of fluids

Thermal conductivity

How well heat is being transferred through material

Conductor

High thermal conductivity and electrical conductivity

Semi-Conductor

Allows some electricity or heat to pass through

Insulator

Low thermal and electrical conductivity

Solubility

Capable of being dissolved

Sorption

Take up of liquid inside its structure

What are the two types of sorption?

1. Absorption

2. Adsorption

Absorption

Uptake of liquid by bulk of solid, cannot be reversed

Adsorption

Concentration of molecules @ the surface of liquid, can be reversed

Two types of bonding materials

1. Cohesion

2. Adhesion

Cohesion

Attract the same kind of molecules

Adhesion

Attracts unlike kind of molecule

Two types of adhesion

1. Adherend

2. Adhesive

Adherend

Where adhesive is being applied

Adhesive

Produces adhesion

Principles of adhesion

1. Wettability

2. Surface tension

3. Surface energy

4. Contact angle

Wettability

Measures affinity of liquid for solid by spreading a drop

Two types of wettability

1. Hydrophobic

2. Hydrophilic

Surface tension

Molecular attraction of molecules at the surface of liquid

Surface energy

Degree of molecules on surface attracts other molecules

Acid etching technique

increases surface energy

Contact angle

Angle formed by adhesive with adherend

Zero degree

Good contact ange

Rheology

Flow or deformation of a material

Two types of rheology

1. Consistency

2. Viscosity

Consistency

Thickness or thinness of a material

Viscosity

Flow or motion

Types of viscosity

1. Pseudoplastic

2. Dilatant

3. Plastic

4. Newtonian

Pseudoplastic

Decreases with increasing shear stress until reaches constant value

Dilatant

Increasing with increasing shear stress until becomes rigid

Plastic

Behaves like rigid body until shear stress is reached

Newtonian

Directly proportional to shear strain

Newtonian fluid

Constant viscosity exhibit at constant stage

Thixotropic Material

Liquid that becomes less viscious and more fluid under pressure

Creep

Deformaton or flow produced in completely set solid material

3 types of color

1. Hue

2. Value

3. Chroma

Hue

Dominant color

Value

Lightness and Darkness

Chroma

Saturation of a color

Fluorescence

Energy that tooth absorbs is converted into light with longer wavelength becomes source of light

Metamerism

Shade of resto in one light

Shade guide

Instrument used in color matching