Performance tests leather

Leather is a natural product and is subject to extensive variability. The physical and chemical properties vary considerably depending on the location from which the leather test sample is taken. The standard test method from the American Society for Testing and Materials (ASTM D2813, 1997) ensures random sampling of finished leather and fabricated leather items for physical and chemical tests. Test specimens should be cut from only one side of the backbone with their long dimension perpendicular to the backbone line. Test specimens should be taken from different parts of the shoulder, belly and tail of the leather. The number of specimens taken depends on the reliability of the test results, the deviation and the error of the testing procedures and should be recorded on the test report. Physical tests of leather and leather products, unless otherwise specified, should be performed under the standard atmospheric conditions of 50 4% relative humidity at 23 1 °C. 

Chromium analysis can be performed on the ash sample from leather or can be perfonned on the leather directly. ASTM D2807 is a method for testing chromium by leather digestion (ASTM D 2807-1998). In this method, weigh 1 g of leather to the nearest 0.0001 g and cut it into small pieces 0.5 cm in diameter. Transfer the specimen to a 250 ml flask and add sequentially 20 ml of concentrated nitric acid (HNOj), 15 ml of perchloric acid (HCIO ) and 10 ml of sulphuric acid (H. SOj. 

The article tells of a test performed by toxicologists who may have known poisons, but knew nothing of polyphosphate and gelatin chemistry. It has been known for many years that polyphosphates and gelatin form coascervates. Leather is tanned by treating the gelatin in hides with polyphosphates, to form coascervates that are more resistant than the leather itself. 

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