Degradation Pathway
Moisture-driven chain scission occurs in the flexible parts of polyurethane molecules when they are exposed to wet environments for long periods. Inside coated textiles, soft segment hydrolysis turns the resilient waterproof layer into a soft, gooey substance that eventually loses its bond to the fabric. This breakdown is particularly common in older polyester-based synthetic leathers found in humid storage conditions.
Environmental Impact
Heat accelerates the rate of this chemical reaction, causing coatings to fail much faster in tropical climates. When soft segment hydrolysis reaches an advanced state, the coating develops a characteristic sour odor and begins to stick to itself or adjacent items. Verification is done through a simple rub test where the coating will easily slide off the base cloth if it has decayed.
Mill Prevention
Finishers avoid these problems by incorporating additives like carbodiimides that act as moisture scavengers within the resin. Selecting ether-based materials instead of esters also reduces the risk of soft segment hydrolysis during the long-term use of the product. Many high-end brands now specify polyether polyurethane to eliminate the possibility of items failing on retail shelves.
Boundary Condition
Factors stop being relevant once the item moves to a dry environment where chemical breakdown essentially pauses. Recovering functionality after soft segment hydrolysis has occurred is impossible because the polymer network is permanently destroyed.
