Hydrolysis Testing Methods

With the popularity of polyurethane (PU) growing in the upholstery marketplace, end users are discovering that not all PUs are created equal. In high traffic seating areas, and under hot and humid weather conditions, PUs that are formulated with inexpensive resin systems will prematurely break down. The breakdown is a delaminating of the PU film layer from the backing substrate in the form of cracking and peeling.

Currently, two tests are considered acceptable to determine the hydrolytic stability of a polyurethane (PU) upholstery product - an ISO test and an ASTM test. The Association of Contract Textiles (ACT) uses the ISO test for its performance guidelines, while the Chemical Fabrics and Film Association (CFFA) endorses the ASTM test. Both tests are conducted by placing the polyurethane material in a heat and humidity chamber at 158 degrees Fahrenheit and 95% relative humidity for a period of time. A brief description of each test is as follows:

ISO 1419: 1995(E) Method C “Tropical Test”
This is the most well-known test in the upholstery marketplace and while its actual name is the “Tropical Test” it is often referred to as the "Jungle Test." In this test, the PU material is put into the test chamber and visually examined against a control sample at the end of each one-week period for a pre-determined number of weeks, or until the product breaks down and fails. Failure against the control sample would be in the form of surface cracking, delaminating of the PU film layer from the backing substrate, or extreme changes in color and gloss level. The test proclaims no minimum specification for failure, but it is generally accepted in the marketplace that a product designed for residential upholstery should withstand at least 3 weeks in the test chamber, and that a product designed for commercial upholstery applications should withstand 5 weeks.

ASTM D 3690 - 02
This test incorporates physical testing after a set period of 15 days in the test chamber. Before the material is put into the test chamber it is tested for adhesion in both the warp and fill directions, and the results are documented. After 15 days the material is removed from the test chamber and allowed to recondition at a controlled room temperature for 24 hours, then tested for adhesion, abrasion, and flex resistance. Adhesion results must maintain at least 75% of the documented values of the material before it was put into the test chamber. It must show no signs of cracking or delaminating after 25,000 Wyzenbeek cycles, with 4 pounds of tension and 3 pounds of compression, using a 100% cotton sateen fabric as the abradent. For flex resistance the ASTM D 2097 Newark Flex test is performed on the material; after 15,000 cycles, there can be no breaks in the PU coating. The criteria of all three of these tests must be met for the PU material to get a passing grade.

It is important to understand the differences in the two tests. The ISO test is the more widely known test. It is a passive test. That is, the sample material is kept in the chamber for a set number of weeks and then given a visual examination. This is the test that people erroneously subscribe the number of weeks in the chamber with an equivalency of years in the field. No such equivalency exists. 

The ASTM is an active test in which the sample material undergoes stringent testing after being in the chamber for 15 days. The result of this test is pass / fail. There is no associated equivalency with years in the field.

The Mitchell Group uses the ASTM to test the hydrolytic stability of its Sta-Kleen products. Moreover, it has run this test for 35 days (5 weeks) not the standard 15 days. This is the value represented on the product specification sheet. Sta-Kleen products that have been tested using ASTM D 3690-02 may have superior hydrolytic stability—far better than a product that passed a 5 week or 7 week ISO test. We utilize the ASTM test at 35 days because we want to ensure our products are able to meet the most rigorous testing standards.