What Is Density?
Density determination is the measurement in which the ratio of the mass of the sample to its volume is determined by immersion (Archimedes), pycnometer or flotation (gradient tube) methods.
Purpose of Density
The purpose is to perform identity verification, fill rate control and porosity assessment by determining the density of the material.
Which Products Is Density Applied To?
- Plastic and rubber parts
- Composites with filler additives
- Coating and painting (ISO 2811)
- Metal and ceramic samples
In Which Sectors Is Density Used?
Standards Related to Density
- ISO 1183-1
- ISO 1183-2
- ASTM D792
- ISO 2811-1
Density Conditions
- Method
- Immersion (A), pycnometer (B), or density gradient tube
- Temperature
- Defined in the standard; usually 23 °C ± 2 °C
- immersion liquid
- Distilled water or liquid that does not interact with the sample
- Number of specimens
- Defined in the standard; The mean and distribution are given
Equipment for Density
- Analytical balance and immersion plate
- Pycnometer set
- density gradient tube
- Temperature-controlled bath
Sample Requirements for Density
- There should be no air bubbles on the sample surface.
- If the sample is porous, the method should be chosen accordingly
- Sample temperature must be stabilized
- The sample must not swell in the immersion liquid
Duration of Density
Typically 1 day.
Density Procedure
- 1The sample is conditioned and weighed in air.
- 2It is weighed (or measured with a pycnometer) in the immersion liquid.
- 3Liquid temperature and density are recorded.
- 4Density is calculated.
- 5Iterated and averaged for a defined number of samples.
Density Acceptance Criteria
The acceptance criterion is the density range given in the material standard.
Evaluation of Results
The immersion method gives incorrect results in open-pore samples; If porosity is present, method selection and sample coating requirement should be evaluated against the standard.
Density Report
- Standard and method applied
- Temperature and immersion liquid
- Weighing values
- Calculated density and distribution
- Assessment against the material standard
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Material product standards
Rubber Testing — What Does This Testing Field Cover?
The section below describes the field that the Density test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Rubber testing determines the mechanical behaviour of an elastomer and its resistance to environmental effects. Elastomers are assessed with a different logic from metals and plastics: the real question is not strength but ELASTIC RECOVERY and ageing behaviour.
The function of an elastomer is usually to deform and return: a gasket is compressed and provides a seal, a mount absorbs vibration, a hose expands under pressure. What is measured in the field is therefore not "how many newtons does it withstand" but "how far does it recover after deformation, and how long does it keep doing so".
COMPRESSION SET is therefore the most decisive measurement in the field. If a gasket cannot recover after being held compressed for a long period, it has lost its sealing function even though it has not torn at all. This measurement is made together with temperature, because permanent set increases rapidly with temperature.
Hardness is the most common measurement in the field, using the Shore A and IRHD scales. It is fast and practical but does not define the material on its own: two different compounds of the same hardness can show completely different ageing and fluid resistance. Hardness is valuable in monitoring compound consistency.
On the environmental resistance side, hot air ageing, swelling in fluids, ozone cracking and low temperature behaviour are examined. FLUID RESISTANCE is particularly critical: the same elastomer behaves differently in fuel, oil, coolant and brake fluid — swelling in one, shrinking in another, hardening in a third. The material is therefore tested with the actual fluid it will contact and at the actual temperature.
Ozone cracking is a silent cause of failure in parts used outdoors. Low concentrations of ozone in the atmosphere create surface cracks in unsaturated elastomers under strain; the part cracks while appearing to carry no load at all. An ozone chamber accelerates and reveals this behaviour.
Low temperature behaviour is the second silent risk. As an elastomer approaches its glass transition temperature it loses elasticity and behaves like a rigid plastic; a gasket starts to leak in the cold. Low temperature recovery and brittleness tests establish this limit.
A change of compound is not a silent change in this family. When filler content, plasticiser or the vulcanisation system changes, mechanical properties and fluid resistance shift together; verification is repeated.
Method groups in this field
Mechanical
Tensile stress-strain properties, tear strength, abrasion (rotating drum and Pico), fatigue and tear propagation.
Hardness
Shore A and IRHD indentation hardness; a rapid indicator of compound consistency.
Permanent deformation
Compression set and stress relaxation; decisive for sealing components.
Fluid resistance
Swelling in fuel, oil, coolant and chemicals, change in mass and volume, loss of hardness and strength.
Ageing
Hot air ageing, ozone cracking, the effects of UV and humidity.
Low temperature
Low temperature recovery, brittleness temperature and flexibility measurements.
Commonly confused in this field
- Hardness does not define the material; two compounds of the same hardness can show different ageing and fluid resistance.
- Fluid resistance must be tested with the actual fluid and the actual temperature; a general claim of oil resistance is insufficient.
- Without measuring compression set, no decision can be made about sealing life.
- Ozone cracking occurs under strain; a test with an unstrained specimen does not show the real risk.
- A change of compound requires verification to be repeated; a supplier may change its compound silently.
- A gasket whose low temperature behaviour is not stated produces unexpected leaks in cold climates.
Which decisions these results support
- Material selection for gaskets and sealing components
- Automotive and industrial component approval
- Verification of a compound change
- Root cause analysis of field leaks and cracking
- Declaration of the operating temperature range and fluid compatibility
Related Tests
Frequently Asked Questions About Density
According to which standard is Density made?
Density is executed in scope ISO 1183-1, ISO 1183-2, ASTM D792 and ISO 2811-1. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Density apply to?
Mainly applied to Plastic and rubber parts, Composites with filler additives, Coating and painting (ISO 2811) and Metal and ceramic samples. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Density done?
The determining parameters are: Method — Immersion (A), pycnometer (B), or density gradient tube, Temperature — Defined in the standard; usually 23 °C ± 2 °C and immersion liquid — Distilled water or liquid that does not interact with the sample. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Density?
There should be no air bubbles on the sample surface., If the sample is porous, the method should be chosen accordingly and Sample temperature must be stabilized. The number of samples is determined according to the product standard and the scope to be reported.
How long does Density take?
Typically 1 day. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Density result called "appropriate"?
The acceptance criterion is the density range given in the material standard.