Polymer Cleavage
A chemical degradation process breaks the covalent bonds in polymer chains through reaction with water, leading to a loss of tensile strength. In the textile industry, hydrolytic chain scission occurs in synthetic fibers like polyester, nylon, and polyurethane when they are exposed to moisture at elevated temperatures. This reaction converts long-chain molecules into shorter fragments, reducing the structural integrity of the fiber.
Degradation Mechanism
Accelerated breakdown occurs in acidic or alkaline environments which act as catalysts for the reaction. During hydrolytic chain scission, the ester or amide linkages in the polymer are cleaved, leaving carboxylic acid and hydroxyl or amine end groups. This increase in the concentration of end groups can be quantified through chemical titration to measure the extent of the degradation.
As the average molecular weight of the polymer drops, the textile loses its mechanical flexibility and becomes prone to premature failure.
Chemical Resistance
High-temperature dyeing and finishing processes must be carefully monitored to prevent this damage. For example, nylon and polyester yarn must be thoroughly dried before extrusion or melt-spinning to avoid rapid hydrolysis in the molten state.
Preventative Action
Incorporating hydrophobic additives or utilizing polymers with a higher degree of crystallinity improves resistance to moisture-induced degradation. These modified fibers are essential for outdoor fabrics and industrial applications where prolonged exposure to humidity is expected.
