BS ISO 4647:2021 pdf download – Rubber, vulcanized — Determination of static adhesion to textile cord — H-pull test
This document specifies a method for the determination of the static adhesion of textile cord to vulcanized rubber using the H-pull test. It is applicable to cords made from natural or man-made fibres. The property levels obtained with this method are affected considerably by the history of the cord and the rubber compound. The method yields data, however, on which a judgement as to the service quality of the material can be based. The method is primarily intended for use with tyre cord. However, it can be applied, if desired, to similar cords for use in other rubber products, but it is limited to cords of linear density not exceeding 800 mg/m (tex).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes 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 5893, Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate of traverse) — Specification ISO 18899:2013, Rubber — Guide to the calibration of test equipment ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods
3 Terms and definitions
No terms and definitions are listed in this document. ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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4 Principle
The adhesion between a rubber and textile cord is assessed by measuring the force required to pull a single cord from a block of vulcanized rubber, the force being applied along the longitudinal axis of the cord and the length of cord embedded in the rubber being fixed (see Figure 1).
Cords are stretched over and perpendicular to the rubber strips, with a distance L between each cord. Two further strips of rubber are applied above the cord, the mould closed and put into a press, and the test pieces vulcanized.
It is common practice to use moulds which allow many identical test pieces to be produced simultaneously as a test pad.
One example of a suitable mould is shown in Figure 2. It is recommended that the width of the cord groove be 0,8 mm for cords of linear density 560 mg/m (tex) or less, and 1,2 mm for cords of linear density more than 560 mg/m (tex) and up to 800 mg/m (tex). Although this form of mould is simple to use, the moulding pressure tends to force excess rubber down the cord groove between the rubber strips, particularly when the cord is much narrower than the groove. This “flash” shall be removed from the cord by careful cutting before the test to improve the reproducibility of the results. The formation of this rubber flash can be almost completely eliminated by using a mould of the form shown in Figure 3, which shows two methods for preparing test pieces. The technique requires the cord length between the rubber strips to be held in position during vulcanization by a deformable surface, rather than a groove, so that there are no voids into which excess rubber can flow.
In method A, the cord between the rubber strips R 1 and R 2 , and between R 3 and R 4 , is held between specially prepared silicone-rubber-faced bars. A suitable method for the preparation of such bars is described in Annex A. In method B, the upper strip of rubber is made sufficiently wide to cover the whole distance R 5 to R 6 (and R 7 to R 8 ), with the addition of a thin cellophane or polyester strip applied to the central portion of the rubber, which contacts the cords, to prevent the adherence of rubber to the cord in this region.
6.2 Tensioning device, capable of providing a tensioning force of 0,49 N ± 0,1 N. This can be achieved, for example, by suspending a mass of 50 g ± 1 g on one end of each cord during assembly of the test piece and removing it prior to placing the mould in the vulcanizing press. The masses can be of the hook type or designed in such a manner that they can be clamped to the cord. In any event, the total mass shall be 50 g ± 1 g.BS ISO 4647 pdf download.