SIST EN ISO 845:2009

SIST EN ISO 845:2009 is the Slovenian adoption of EN ISO 845:2009, based on ISO 845:2006 from CEN and ISO. It specifies a test method for determining the apparent overall density and apparent core density of cellular plastics and rubbers. Engineers, laboratories, quality teams and buyers use it when they need a common density result for moulded or extruded cellular materials.

What does SIST EN ISO 845:2009 specify?

SIST EN ISO 845:2009 specifies how to determine apparent overall density and apparent core density for cellular plastics and rubbers. The method applies to materials with skins formed during moulding or extrusion, and the scope notes that a different method such as buoyancy may be used for shaped materials.

The document is organized into clauses on scope, normative references, terms and definitions, apparatus, test specimens, procedure, expression of results, accuracy and test report. In practice, that means it gives the full path from specimen preparation to the final report.

What are the key requirements of SIST EN ISO 845:2009?

Specimens and conditioning

Clause 5 requires specimens that can be measured easily and cut without deforming the cell structure. It also requires at least five specimens and a minimum specimen volume, so the result is based on more than one piece and is less sensitive to local variation.

Clause 5 also sets conditioning expectations after manufacture and before testing. For the user, this matters because moisture and ageing can change density, so the timing and atmosphere before test must be controlled and reported.

Measuring and weighing

Clause 6 requires dimensional measurements in accordance with ISO 1923, with multiple measurements for each dimension. For rigid board form, the standard asks for more measurements in the central area, which helps avoid edge effects.

Clause 6 also requires mass to be measured with stated accuracy. In practice, the test is only as reliable as the volume and mass data used to calculate density.

Calculating the result

Clause 7.1 gives the calculation for apparent density from mass and volume, and it allows a buoyancy correction when low-density closed-cell materials are affected by displaced air. This matters for very light materials, where air displacement can shift the reported density enough to affect acceptance decisions.

Clause 7.2 requires the estimated standard deviation from the set of specimen results. That gives the user a simple measure of spread, which is useful when comparing batches or checking process consistency.

Accuracy and reporting

Clause 8 states that the published accuracy information was developed from rigid materials conditioned for 72 h. The practical point is that users should be cautious when comparing those figures with softer materials or different conditioning times.

Clause 9 requires the test report to identify the material, conditioning conditions, skin status, specimen defects, individual results, mean density, standard deviation, any buoyancy allowance, and any deviation from the method. This makes the result traceable and easier to compare between laboratories.

What terms does SIST EN ISO 845:2009 define?

• Apparent overall density - the mass per unit volume of a cellular sample, including all skins formed during moulding.
• Apparent core density - the mass per unit volume after the skins formed during moulding have been removed.
• Density, ρ - the symbol used in the standard for the calculated apparent density result.
• Standard deviation, s - the calculated spread of the specimen results around the mean.
• Buoyancy - the air-displacement effect that can bias results for very low-density materials.
• Standard atmospheres - the conditioning environments defined through ISO 291 and used before testing.

Who uses SIST EN ISO 845:2009?

SIST EN ISO 845:2009 is used by manufacturers, test laboratories, and quality control teams working with cellular plastics and rubbers. It is especially useful for moulded or extruded products where skin, core structure, and density uniformity can affect product acceptance.

Buyers and technical specifiers also use it when they need a clear density value in a purchase specification or inspection plan. That helps them compare supplier data using the same measurement approach.

What changed in SIST EN ISO 845:2009 from the previous edition?

SIST EN ISO 845:2009 supersedes EN ISO 845:1995. The underlying ISO text is ISO 845:2006, identified as the third edition, and the foreword states that it cancels and replaces ISO 845:1988 after technical revision.

Which standards are used with SIST EN ISO 845:2009?

ISO 291 provides the standard atmospheres used for conditioning and testing. ISO 1923 provides the method for measuring linear dimensions, which is needed to calculate specimen volume before density is determined.

What does the SIST EN ISO 845:2009 document contain?

The document contains a compact laboratory test method rather than a product specification. Clause 4 sets out the balance and measuring instruments, Clause 5 covers specimen shape, size, number and conditioning, and Clause 6 describes how to measure dimensions and mass.

Clause 7 provides the density calculation, the optional buoyancy allowance, and the standard deviation calculation. Clause 8 gives accuracy information, and Clause 9 gives the reporting checklist for testing, audits, and technical documentation.