Poor adhesion of the finish of an upper material can give rise to flaking or peeling in the shoe factory or in wear. Measurement of the actual strength of the adhesion is therefore important and the SATRA adhesion of finish tester enables this to be done reliably and simply. It has been adopted by the Society of Leather Technologists and Chemists (Method SLF 11) and the method has been recommended by the British Standards Institution as suitable for footwear materials in the introduction to BS 5131. It is also a test requirement for garment leathers in BS 6453: 1984.
The finish side of a strip of upper material is first stuck to a test strip (which can be of metal or PVC depending upon the adhesive used) using an adhesive which does not affect the bond of the finish to the upper material. Increasing static loads are applied to the upper material until it peels away, leaving the finish on the test strip. In some cases the top coat of the finish may be peeled from the base coat. The test is, therefore, very useful in the shoe factory for measuring the compatibility of shoe room dressings and of leather finishes.
Two methods of preparing the test assemblies are available and the actual composition of the apparatus depends on which adhesive is used.
The machine is supplied as standard set up to carry out the polyurethane adhesive test. If the epoxy resin adhesive test is required then the extra parts need to be ordered, Ref. STD 112A, together with resin and hardener, Ref. STD 112R and STD 112H.
A similar test is available utilising a tensile testing machine.