The surface op the final leather products is subject to the most different kinds of stress in everyday use in order to determine optimum properties of the finish coats with regard to their fastness to erasing abrasion reference tests are performed with standardized rubber test specimens. The degree of damage of the wet and dry leather and the change of colour of the finish are assessed. This is an additional test of the fastness to dry and wet rubbing besides the fastness test with felt pads.
Resistance to detergents, cleaning agents and shoe polishes
in shoe fabrication the leathers are particularly soiled through mechanical processingor by contact with dust oil perspiration or fatty substances therefore they have to be cleaned or wiped with a variety of agents as they have received different types of finishes it is necessary to determine by means of preliminary testing with test solutions which product is suitable to prevent defects or
changes of colour the test solutions are neutral cleaning agents weak alkali solutions or benzene the suitable shoe polish is determined by three basic types of product products based on oil emulsions and aqueous products.
Resistance to amines (DABCO)
The finish of furniture leathers upholstered with polyurethane foam but also of shoe upper leathers manufactured with mould on polyurethane foam, but also of shoe upper leathers manufactured with mould-on polyurethane soles, can be damaged by the escape of gaseous
1,4-diazabicyclo (2,2,2) octane= triethylene diamines (abbreviated as DABCO). This causes cracking of the film, especially with nitrocellulose finishes, and results in yellowing of white and pale leathers. Polyurethane finishes or films of cellulose aceto butyrate and albumin binders are stable to DABCO vapors.
A change of the finish due to ageing is mainly indicated by embrittlement of the film this is most
Ly caused by migration of plasticizers from the pigment coat into the interior of the leathers in a quick reference test the leather is stored in the drying oven for several days at different temperatures 50 and 80 c after conditioning the leather samples are assessed as regards embrittlement yellowing elasticity and flexing endurance of the finish films
To process finished leather it is important to know which maximum temperature is admissible for subsequent ironing or lasting without causing damage to the finish the test is performed by means of a hot iron or ironing machine and with temperatures increasing in increments of 20 25 c in order to assess smearing damaging or change of shade of the finish films.
The resistance of the top coat to hot air is tested by means of a hot air current. The initial temperature is 210 ⁰ C. If changes occur, further tests are performed with temperature reduced in increment of 20 ⁰ C.
Resistance to ageing
Ly caused by migration of plasticizers from the pigment coat into the interior of the leathers in a quick reference test the leather is stored in the drying oven for several days at different temperatures 50 and 80 c after conditioning the leather samples are assessed as regards embrittlement yellowing elasticity and flexing endurance of the finish films
To process finished leather it is important to know which maximum temperature is admissible for subsequent ironing or lasting without causing damage to the finish the test is performed by means of a hot iron or ironing machine and with temperatures increasing in increments of 20 25 c in order to assess smearing damaging or change of shade of the finish films.
Fastness to hot ironing, resistance to hot air
To process finished leather it is important to know which maximum temperature is admissible for subsequent ironing or lasting without causing damage to the finish. The test is performed by means of a hot iron or ironing machine and with temperature increasing in increments of 20 to 25 % in order to asses smearing damaging or change of shade of the finish.The resistance of the top coat to hot air is tested by means of a hot air current. The initial temperature is 210 ⁰ C. If changes occur, further tests are performed with temperature reduced in increment of 20 ⁰ C.
Fastness to hot steaming
This test serves t determine the fastness of the top coats to hot steam, to which the leather in shoe production is exposed before lasting. The leather sample is laid into a test chamber saturated with steam for 5 minutes at 65 degree temperature. Swelling of the finish coat or migration of dye is assessed.
Elasticity endurance
If leather is stretched, extended or deformed by bulging the finish should be so elastic that it does not tear or crack off.
A quick reference test is performed by means of a key or mandrel these are drawn with pressure along the unfinished side of the leather the lastometer test a sharp mandrel is pressed upwards to determine the bulging height in the tensometer test a larger section of leather is stretched over a diaphragm to form a spherical cap this also serves to test whether the finish flakes or cracks off.
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