Polymers, composites, ceramics and others (-100 °C to 250 °C)

This guarded heat flow meter is a commercial apparatus for thermal conductivity (or thermal resistance) of medium thermal conductivity materials such as plastics, ceramics and composites.

Specification

• Thermal resistance range: 0.001 m²·K/W to 0.03 m²·K/W
• Mean specimen temperature range (configuration A): 10 °C to 250 °C
• Mean specimen temperature range (configuration B): -100 °C to 20 °C
• Conforms to ASTM E1530-06

Accreditation

• UKAS accredited test service (UKAS 0002)

Specimen dimensions

A single specimen is required.

• Thickness: 1 mm to 20 mm
  (The optimum thickness is dependent on thermal conductivity and the specimen must be within the specified thermal resistance range)
• Diameter: 50.8 mm
  (Within the range 50.6 mm to 51.0 mm)
• Parallelism: Variation in thickness should be less than 0.025 mm
• Flatness: Both round faces must be flat to better than 0.025 mm

Thin Sheets

This apparatus also has a special mode of operation for measuring thin sheets: A layer of the sample material would be placed between two discs of reference material to create a suitable test specimen. The increase in thermal resistance would then be measured as additional layers of the sample material are added to the specimen in successive tests. This allows the effect of thermal contact resistance between the layers to be excluded from the calculated value for thermal resistance of a single layer. We require enough material to cut up to ten 50.8 mm diameter disks.

Note 1

Maximum mean specimen temperature to be at least 20 °C below the softening point of the test specimen.

Note 2

Although 'thermal conductivity'is a property of a homogeneous material, it is generally accepted that the term can still be used for insulation/construction products that contain a continuous mixture of two or more materials (e.g. air and glass fibre or air and concrete) providing the size of any particles is less than a tenth of the specimen thickness. However, if your samples have either discrete layers or large particles, then 'thermal resistance' would be quoted on the Test Report, rather than 'thermal conductivity'. However, the thickness of the product during the test would be quoted in the Test Report, allowing an 'effective' thermal conductivity to be calculated by dividing the thickness (in metres) by the thermal resistance.

Note 3

Consideration should be given to whether or not the specimen is likely to undergo changes in its material properties at the highest temperature at which it is to be measured. If this is the case, then it may be appropriate to either pre-conditioning the specimen at the highest temperature or to request measurements at different temperature points be carried out in a specific order or repeated.

Contact

Customer Services tel: +44 20 8943 6245
E-mail: thermal_enquiries@npl.co.uk