Summary of Performance Testing Methods for Non-metallic Materials

Figure 1: Non-metallic Materials

1. Density and Relative Density

Density refers to the mass contained within a unit volume of a substance, with units of megagram per cubic meter (Mg/m³), kilogram per cubic meter (kg/m³), or gram per cubic centimeter (g/cm³).

Relative density is the ratio of the density of a substance to the density of a reference substance under their respective specified conditions. The symbol is "d", a dimensionless quantity. Common reference substances are air or water: for air, the density of dry air at standard conditions (0°C and 101.325 kPa) is 1.293 kg/m³ (or 1.293 g/L).

Testing methods: Buoyancy method, water displacement method, pycnometer method, gamma ball immersion method, saturated water method, surface coating method, etc.

2. Freezing Point

The freezing point is the temperature at which a crystalline substance solidifies. It is the temperature at which the vapor pressure of a liquid equals the vapor pressure of its solid. Different crystals have different freezing points. Under certain pressures, the freezing point of any crystal equals its melting point. Amorphous substances do not have a freezing point.

3. Melting Point and Melting Range

The melting point is the temperature at which the solid and liquid phases of a pure substance are in equilibrium under a given pressure. The melting range is the temperature range from the start of melting to complete melting, as measured by the capillary method.

Testing methods: Capillary method, supercooling method.

4. Refractive Index

The refractive index is a physical quantity representing the ratio of the speed of light in two different (isotropic) media. When light passes from one transparent medium into another with different density, its speed changes, causing a change in direction (refraction). The ratio of the sine of the angle of incidence to the sine of the angle of refraction, or the speed ratio of light in a vacuum to that in the medium, is the refractive index.

Testing methods: Solid - goniometer method; Liquid - critical angle method; Gas - interference method.

5. Flash Point and Ignition Point

The flash point, also known as the fire flash point, is an indicator of the flammability of a liquid. It is the lowest temperature at which the vapor of a flammable liquid ignites momentarily when exposed to a flame. Flash combustion usually produces a faint blue spark and does not sustain burning. The flash point can be measured using open cup and closed cup methods: the former is typically used for high flash point liquids and the latter for low flash point liquids.

The ignition point is the lowest temperature at which the vapor of a flammable liquid ignites and sustains combustion upon contact with a flame.

Testing methods: Open flash point, closed flash point.

6. Viscosity

Viscosity refers to the internal friction resistance generated during the flow of a fluid (liquid or gas), which is determined by the type of substance, temperature, and concentration. It is usually referred to as dynamic viscosity, with units of pascal-second (Pa·s) or millipascal-second (mPa·s). Viscosity can be classified into dynamic viscosity, kinematic viscosity, and relative viscosity, which should not be confused.

Testing methods: Capillary method, falling ball method, rotational method, vibrational method.

7. Specific Heat Capacity

The amount of heat required to raise the temperature of 1 kilogram of a substance by 1K is called specific heat capacity, with units of kJ/(kg·K). Under constant pressure, the heat absorbed when the temperature rises by 1K is called constant-pressure specific heat capacity.

Testing methods: Mixing method (for solids), electrical heating method (for liquids), cooling method, comparison method.

8. Water Content

The amount of water contained in a substance, excluding crystalline water and associated water. It is usually expressed as the percentage of the original mass of the sample to the mass of the sample after dehydration.

Testing methods: Physical methods - gravimetric method, distillation layering method, gas chromatography; Chemical methods - Karl Fischer method, toluene method.

9. Ash

Ash, also known as ignition residue, refers to the residue of oxides and salts formed from the mineral components after evaporation and ignition, expressed as a percentage.

10. Hardness

Hardness is the ability of a material to resist external forces such as indentation or scratching. Depending on the testing method, there are Shore hardness, Brinell hardness, Rockwell hardness, Mohs hardness, Barcol hardness, and Vickers hardness. The value of hardness depends on the type of hardness tester used, with the Shore hardness tester being simple in structure and suitable for production testing.

Testing methods: Common methods include Shore hardness, ball indentation hardness, Rockwell hardness, etc.

11. Molecular Weight Distribution

Due to the size variability in polymers, molecular weight has statistical characteristics and polydispersity, i.e., molecular weight distribution. The same average molecular weight can have different molecular weight distributions, resulting in different properties.

Testing methods: Precipitation fractionation method, ultracentrifugal sedimentation method, gel permeation chromatography.

12. Glass Transition Temperature

The approximate midpoint of the narrow temperature range in which amorphous or semi-crystalline polymers transition from a viscous flow state or high elastic state to a glassy state (or vice versa) is called the glass transition temperature, usually denoted by Tg, and is an indicator of heat resistance.

Testing methods: Thermomechanical analysis (TMA), differential thermal analysis (DTA), differential scanning calorimetry (DSC).

13. Heat Deflection Temperature under Load

Heat deflection temperature (HDT) is a measure of the heat resistance of polymers. It is determined by placing a polymer sample in a suitable heat transfer medium with a constant heating rate and measuring the temperature at which the sample reaches a specified deflection under a bending load.

Testing methods: Heat deflection temperature test under load.

14. Minimum Film Formation Temperature

The minimum temperature at which a continuous film forms in a synthetic emulsion system is called the minimum film formation temperature (MFT).

15. Softening Point

The softening point is the temperature at which a polymer sample deforms to a specified extent under a certain load and at a prescribed heating rate.

Testing methods: Ring and ball method, fiber-drawing method (for glass), etc.

16. Vicat Softening Point Test

The Vicat softening point test evaluates the tendency of thermoplastics to deform at high temperatures. A flat-topped needle with a specified load and a cross-sectional area of 1 mm² is applied to the sample under constant heating. The temperature at which the needle penetrates 1 mm into the sample is the Vicat softening temperature.

17. Creep

Creep refers to the phenomenon in which deformation changes over time when stress remains constant.

18. Tensile Strength

Tensile strength is the maximum tensile stress that a sample can withstand before breaking. This term was previously used inconsistently, with terms like breaking force, breaking strength, tensile force, tensile strength, and strength being used. According to GB 6039-85, it is uniformly called tensile strength, with units of MPa.

19. Peel Strength

Also known as anti-peel strength, it refers to the maximum breaking load per unit width, measured in kN/m, used to assess the force-bearing capacity of lines.

20. Elongation

The increase in length of a sample under tensile force, expressed as a percentage of the original length.

21. Flame Resistance

Flame resistance is the material's ability to resist combustion when exposed to flames or to prevent continuous combustion after removal from the flame.

Testing method: UL94 flammability test.

22. Weatherability

Weatherability refers to the material's ability to withstand exposure to sunlight, heat, cold, wind, and rain.

Testing methods: Natural climate exposure, outdoor accelerated testing, laboratory simulation.

23. Aging

Aging refers to the series of physical or chemical changes that occur in polymers during processing, storage, and use due to external factors such as heat, light, oxygen, water, radiation, mechanical stress, and chemicals. These changes result in embrittlement, cracking, stickiness, discoloration, roughening, blistering, surface chalking, delamination, and gradual deterioration of properties, ultimately rendering the material unusable.

Testing methods: Artificial accelerated aging test, natural aging test, outdoor natural accelerated exposure test.