What is alkali hydrolysis?

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Created on Monday, 03 July 2000 01:42

Written by Rich Fitzmorris

Question: What is alkali hydrolysis? How can I test for it? Identify it? Prevent it? Resolve it? I know that washload titrations can identify alkali hydro. However, if our titration levels are normal. Can alkali hydrolysis still be affecting our merchandise? Our white tablecloths have become tender at the corners breaking apart (in one direction) and the breakdown of fibers is visible.
- Brian, GM of O.K. Towel and Uniform Supply, Elizabeth, NJ

Answer: The process of fibers breaking down in fabrics generally describes alkali hydrolysis. Excessively high pH levels, along with high temperatures, causes the damage. The fibers are pitted and noticeably weak, commonly referred to as tensile strength loss. Cotton is generally resistant to high levels of alkali, but polyester blends can be easily damaged from the combination of high temperatures and pH levels in excess of 11.5. Quats, commonly used in chemical fabric softeners, will greatly increase alkali hydrolysis when processing polyester material. Most manufacturers recommend not using Quats on polyester fabrics.
Choosing the proper alkali levels for the fabric type is important. It is also necessary to monitor the pH in the wash bath, maintain temperatures to 160 degrees or less, and not overload the wash wheel. The proper number of rinses and correct stepping down of temperature in each bath is important, and there should be less than 50 PPM of alkalinity in the last rinse. The final step where sour is used to remove residual alkalinity should be adequate in time or step to adjust the desired pH evenly across the material.

Since the fabric content isn’t identified, but was mentioned to be white linen, it should not be overlooked that bleaching can cause damage. Proper methods of bleaching and rinsing, and the use of an anti-chlor can be important to linen life.

Rich Fitzmorris, Vice President, Laundry Division, Sunburst Chemicals.