Leather — Physical and mechanical tests — Determination of flex resistance: Vamp flex method
1 Scope
This standard specifies a method for determining the wet or dry flex resistance of leathers and finishes applied to leather.
This standard is applicable to the determination of flex resistance of all types of leather below 3.0 mm in thickness.
2 Normative references
The following referenced documents are indispensable for the application 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.
GB/T 6682 Water for analytical laboratory use - Specification and test methods (GB/T 6682-2008, ISO 3696:1987, MOD)
GB/T 39364 Leather - Chemical, physical, mechanical and fastness tests - Sampling location (GB/T 39364-2020, ISO 2418:2017, MOD)
QB/T 2707 Leather - Physical and mechanical tests - Sample preparation and conditioning (QB/T 2707-2018, ISO 2419:2012, MOD)
3 Principles
A test piece is folded with the surface to be tested outwards over two inverted “V” shaped clamps. Relative movement of the clamps flexes the sample producing one downward crease surrounded by four upward creases. The test piece is examined periodically for damage.
4 Apparatus
4.1 Flex resistance test machine, incorporating the following:
4.1.1 Two inverted “V” shaped clamps (Figures 1 and 2), aligned parallel to one another, centred on the same axis and with a minimum separation between the clamps of (9.5 ± 1.0) mm. Each clamp shall have two parts.
4.1.1.1 An outer part comprising a “V” form with an internal angle of (40 ± 1)° and a truncated tip radius of (6,4 ± 0.5) mm.
4.1.1.2 An inner part having the shape and size that shall complement the outer part.
4.1.2 A means of applying a simple harmonic reciprocating motion between the two clamps, to move them apart by (19.0 ± 1.5) mm and return them to the minimum separation (4.1.1) at a rate of oscillation of (300 ± 30) cycles/min.
4.1.3 Counter, to indicate the number of complete cycles.
Press knife: meeting the requirements of QB/T 2707; its inner wall is a rectangle (40±2)mm × (64±1)mm.
4.3 Optical magnifier, with a magnification of approximately four to six times.
Foreword II
1 Scope
2 Normative references
3 Principles
4 Apparatus
5 Sampling and sample preparation
6 Procedure
7 Test report
