Materials Property Glossary

Chemical Properties

Atomic Volume (average)

The atomic (or molecular) volume (VM) is the average volume per 103*NO of atoms in the structure, where ‘NO is Avogadro's number (6.022 x 1023/mol). For a pure element, it is represented by:

VM = A / ρ

where, ‘A’ is the atomic weight in (kg/kmol) and ‘ρ’ (rho) is the density in (kg/m3).

For compounds the average atomic volume represented by:

VM = M / nρ

where, ‘M’ is the molecular weight and ‘n’ is the number of atoms in the molecule. Thus for a compound with the formula (AxBy) it is represented by:

VM = (XAA + YAB) / (x + y)ρ

where, ‘AA is the atomic weight of element ‘A’, and ‘AB is the atomic weight of element ‘B’. For a polymer (CxHyOz)n it is therefore represented by:

VM = XAC – YAH + ZAO / (x + y + z)ρ

where, ‘AC is the atomic weight of carbon, ‘AH’ is the atomic weight of hydrogen and so forth. The atomic volume is involved in many property correlations together with the density it gives the atomic weight.

Density

The density of a material is defined as its mass (m) per unit volume (V). It is represented in the following equation where ‘ρ’ (rho) represents density;

ρ = m / V

Energy Content

The energy content of a material is an approximate estimate of the energy used to make it from its naturally occurring ores, feed stocks or sources, plus the energy content of the source material itself.

Mechanical Properties

Bulk Modulus

When Hooke’s law is obeyed, the volume strain is proportional to the volume stress. The corresponding elastic modulus (ratio of stress to strain) is termed the bulk modulus. It can be represented in the following equation where ‘B’ represents Bulk modulus, ‘Δp’ represents the change in pressure and ‘V’ represents volume, where ‘ΔV’ is the change in volume and ‘VO’ is the original volume:

B = [ - Δp / (ΔV / VO) ]

Compressive Strength

Compressive Strength is the maximum compressive stress a material can withstand before failure.

Ductility

Ductility is the ability of a material to absorb energy by being drawn out or hammered thin without rupturing, and that can undergo large plastic deformation without fracture or failure. It can also be expressed as the percent fraction of the original gauge length.

Elastic Limit

The elastic limit is the stress beyond which there is permanent deformation. Below the elastic limit all the deformation is recovered when the load is removed.

Endurance Limit

Endurance limit (or sometimes referred to as the fatigue limit) is the maximum stress amplitude in fatigue below which a material can endure an essentially infinite number of stress cycles and not endure failure.

Fracture Toughness

Fracture Toughness is the measure of resistant a material has to the propagation of a crack, denoted KC.

Hardness

Hardness is the resistance a materials surface offers to abrasion, scratching and indentation (local plastic deformation). It is often measured by pressing a pointed diamond or hardened steel ball into the surface of the material. The hardness is defined as the indentor force divided by the projected area of the indent.

Loss Coefficient

The Loss Coefficient is the measure of a materials ability to dissipate vibrational energy. It can be expressed in the following equation where ‘η’ represents Loss Coefficient and ‘ΔU’ represents the change in stored elastic energy.

                            η = ΔU / 2πU

Modulus of Rupture

Modulus of Rupture (MOR) is the maximum surface stress in a bent beam at the instant of failure.

Poisson’s Ratio

Poisson’s Ratio is the negative ratio of the thickness decrease divided by the length increase as a result of a tensile stress applied to a material.

Shear Modulus

Shear modulus is the ratio of shear stress divided by the shear strain in the elastic region. It can also be referred to as modulus of rigidity or torsion modulus.

Tensile Strength

Tensile Strength is the maximum tensile stress a material can withstand before failure.

Young's Modulus

Young’s Modulus (or Elastic Modulus) is the proportionality constant of solids between elastic stress and elastic strain and describes the inherent stiffness of a material. It can be expressed in the following equation where, E is Young’s Modulus;

                            E = Elastic Stress / Elastic Strain

Thermal Properties

Glass Temperature

The Glass Transition Temperature relates to those materials that are non-crystalline solids and is defined by the transition from a true solid to very viscous liquid.

Latent Heat of Fusion

Latent Heat of Fusion is the heat required per unit mass to change a materials state to another state i.e. from a solid to liquid or from a liquid to gas, this process is a reversible, therefore includes a gas to liquid or from a liquid to solid.

Maximum Service Temperature

Maximum Service Temperature is the temperature at which a material can reasonably be used without the effects of oxidation, chemical change or excessive creep.

Melting Point

The Melting Point is the temperature at which a material turns suddenly from solid to liquid.

Minimum Service Temperature

Minimum Service Temperature is the temperature at which a material can reasonably be used without the loss of its original serviceable properties.

Specific Heat

Specific Heat is the quantity of joules needed to raise one unit mass (one Gram mole) of a substance one Kelvin at constant pressure.

Thermal Conductivity

Thermal Conductivity is a measure of heat flow through a material. Where by it relates heat flow (the flow of heat energy per unit area per unit time) too the temperature gradient (which describes a temperature difference per unit distance), causing the heat flow.

Thermal Expansion

Thermal Expansion is the term used to describe the change in dimensions that occurs with most materials as the temperature is increased or decreased.

Electrical Properties

Breakdown Potential

Breakdown Potential is the potential required to apply to a material that is normally an insulator, that allows conduction (or partial ionisation) through the material.

Dielectric Constant

Dielectric Constant is the degree of polarisation or charge storage capability of a material when subjected to an electric field.

Resistivity

Resistivity is the intrinsic materials property that describes the ability of a material to resist, or oppose, the transport of electrical charge in response to an external electric field.

Environmental Properties

Flammability

Flammability is a materials ability to suppress combustion. Where the number given corresponds to a relative rating system.

Fresh Water

Is the materials ability to resist attack from Fresh Water. Where the number given corresponds to a relative rating system.

Organic Solvents

Is the materials ability to resist attack from an Organic Solvent environment. Where the number given corresponds to a relative rating system.

Oxidation at 500°C

Is the materials ability to resist attack via Oxidation at 500°C. Where the number given corresponds to a relative rating system.

Sea Water

Is the materials ability to resist attack from a Sea Water environment. Where the number given corresponds to a relative rating system.

Strong Acid

Is the materials ability to resist attack from Strong Acid. Where the number given corresponds to a relative rating system.

Strong Alkalis

Is the materials ability to resist attack from Weak Alkalis. Where the number given corresponds to a relative rating system.

UV

Is the materials ability to resist attack against UV ( ultra violet light ). Where the number given corresponds to a relative rating system.

Wear

Is the materials ability to resist Wear. Where the number given corresponds to a relative rating system.

Weak Acid

Is the materials ability to resist attack from Weak Acid. Where the number given corresponds to a relative rating system.

Weak Alkalis

Is the materials ability to resist attack from Weak Alkalis. Where the number given corresponds to a relative rating system.

Relative Rating System

The numeral given corresponds to these ratings: 1 = very poor, 2 = poor, 3 = average, 4 = good and 5 = very good.

Primary author: AzoM.com

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