A permanent press is a characteristic of fabric that has been chemically processed to resist wrinkles and hold its shape. Alternative terms include wrinkle resistant, wash and wear, no-iron, durable press, and easy care. This treatment has a lasting effect on the fabric.
Cotton’s penchant for wrinkling is inscribed in its DNA. Cotton is a cellulose fiber, and cellulose is a polymer. Like all polymers, cellulose has a chainlike structure, comprising long strands of glucose molecules. Hydrogen bonds tie the glucose together.
These hydrogen bonds are weak and easily broken. (Washing breaks them handily.) When the bonds break, the structure of the chains is no longer secure, causing the molecules within them to shift and the fabric to wrinkle.
True permanent press — the term properly describes cloth that is a blend of cotton and synthetic fibers — was invented in the mid-20th century, but for textile makers, a no-iron, 100-percent cotton fabric was a long-sought grail. A few such fabrics had been developed, but they still needed touch-ups with an iron on emerging from the dryer.
Dr. Benerito refined these earlier fabrics by attacking cotton’s weakest link. With her colleagues, she developed a process called cross-linking, which replaced the ineffectual hydrogen bonds with stronger ones. The new chemical bonds act like the sturdy rungs of a ladder, snapping the polymer chains back to crisp, unwrinkled attention.
Treated this way, the resulting fabric (also known by names like durable press and wash-and-wear) needed little or no ironing. Cross-linking, which lets a range of chemicals be affixed to polymer chains, also made possible later developments including stain-resistant and flame-retardant cotton.