Hydrolysis

Definition and Overview

Hydrolysis is a deterioration phenomenon in which moisture acts on the chemical bonds in a material, changing and breaking molecular links and reducing performance. It tends to occur in hot, humid environments and can also happen during storage even when the item is not in use.

In apparel materials, it is a concern with synthetic leather using polyurethane, coatings, laminates, adhesives, and rubber-based materials. It may appear as stickiness on the surface, hardening, powdering, cracking, or peeling between layers.

Target Materials and Structure

The susceptibility to hydrolysis varies depending on the type of material, formulation, resin design, surface treatment, and usage environment. For materials containing polyurethane, it is important in practice to check hydrolysis resistance as a performance item.

The manufacturing method itself, such as woven elastic, knitted elastic, or braided elastic, does not determine whether hydrolysis occurs. Check the constituent materials, such as elastic yarn, covered yarn, and adhesive layers, together with the intended use and exposure to sweat, washing, and moisture.

• Woven elastic: a flat elastic in which elastic yarn is fixed by a woven structure.
• Knitted elastic: an elastic with a relatively soft texture made by a knitted structure.
• Braided elastic: an elastic made with a braided structure, in round or flat form.

Points to Check for Stretch and Applications

For elastic materials, check not only the width but also elongation rate, elongation stress, and elongation recovery rate. Elongation rate indicates how far it can stretch, elongation stress is the force required to stretch it by a certain amount, and elongation recovery rate is an index showing how well it returns after stretching.

As hydrolysis and other time-related deterioration progress, the material may lose its ability to recover, become hard, or break more easily. Evaluation is especially necessary in areas such as waistbands, cuffs, innerwear, and sports applications, where repeated stretching and exposure to sweat and humidity occur.

Selection and Handling Precautions

When selecting materials, check the test conditions and evaluation standards for hydrolysis resistance, and conduct prototype evaluations under temperature and humidity, washing, sweat, and stretch conditions close to the actual application. Even if a product is labeled as hydrolysis-resistant, that does not mean it will not deteriorate in every environment.

For storage, avoid high temperatures, high humidity, and sealed conditions, and do not leave items wet for long periods. Follow the product's washing and drying instructions, and check the effects of heat, detergents, and bleach for each material. Because elasticity and surface condition are difficult to restore after deterioration, preventive management is important.

Differences from Similar Terms

Hydrolysis is a chemical deterioration involving moisture. It has a different cause from the phenomenon where repeated stretching alone prevents recovery, but both reduce the elastic recovery of rubber, so they should be distinguished and the cause confirmed during use.

Hydrolysis resistance indicates durability against hydrolysis. On the other hand, wash durability is the ability to maintain function and appearance after repeated washing, and it includes not only hydrolysis but also the effects of friction, heat, detergents, and mechanical force.

Frequently Asked Questions