BS EN ISO 8067:2018 pdf download – Flexible cellular polymeric materials – Determination of tear strength
This document specifies two methods for the determination of the tear strength of flexible cellular polymeric materials:
— method A, using a trouser test piece;
— method B, using an angle test piece without a nick.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content onstitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1923, Cellular plastics and rubbers — Determination of linear dimensions
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
maximum force per unit thickness observed when stretching a test piece to rupture
The tear strength shall be measured on a tensile-testing machine which will indicate the force at which rupture of the test piece takes place. An automatic machine should preferably be used which draws the actual curve, or a stylus or scale should be used having an indicator that remains at the point of maximum force after rupture of the test piece.
The accuracy of the test machine shall be class 2 or better as defined in ISO 7500-1.
5 Test pieces
The test pieces shall be free of voids and flow lines. Test pieces can be selected either with or without skin.
6 Number of test pieces
Three test pieces shall be tested.
Additional test pieces may be required if the spread of results is too great (see Clause 9) or to compensate for deviation in the progress of the tear (see 8.2).
7 Conditioning Materials shall not be tested less than 72 h after manufacture, unless it can be demonstrated that the mean results obtained at either 16 h or 48 h after manufacture do not differ by more than ±10 % from those obtained after 72 h, in which case testing is permitted at either 16 h or 48 h, respectively.
Prior to the test, the test pieces or the material from which the test pieces are to be cut shall be conditioned for at least 16 h in one of the following atmospheres, unless otherwise specified: — (23 ± 2) °C, (50 ± 5) % relative humidity; — (27 ± 2) °C, (65 ± 5) % relative humidity.
This conditioning period may form the final part of, or in the case of testing 16 h after manufacture, the whole of the period following manufacture. In the case of quality-control tests, test pieces may be taken a shorter time (down to a minimum of 12 h) after manufacture and testing carried out after conditioning for a shorter period (down to a minimum of 6 h) in one of the atmospheres specified above. It is recommended that, for referee purposes, the test is performed 7 days or more after the cellular material has been manufactured. 8 Procedure
8.1 General After conditioning as specified in Clause 7, measure, in accordance with ISO 1923, the thickness of the test piece at the location shown in Figure 1 or Figure 2.
8.2 Method A
8.2.1 Clamp the test piece in the jaws of the test machine, taking care that the jaws grip the test piece properly. Spread the ends of the test piece so that the force is applied in the direction shown in Figure 4. Start the test machine with a jaw speed of 50 mm/min to 500 mm/min.
8.2.2 Where necessary in order to keep the cut in the centre of the test piece while tearing, aid it with light application of a sharp blade, for example a single-edged razor blade.
Cutting should be the exception and should be avoided because it could influence the result.
Care should be taken when using blades.