Номер B, страница 54 - гдз по английскому языку 11 класс учебник Комарова, Ларионова

Learn about chemistry. Units 3 and 4 - номер B, страница 54.

Условие.

B Now read about different fabrics. How could no-iron, no-stain, no-clean clothes help the environment?

No-wrinkle clothes

Cotton is a cellulose-based substance. It comes from plants. In cotton, the cellulose is cross-linked with hydrogen bonds which hold the fabric flat. When it gets wet or sweaty, however, the hydrogen bonds break and it starts to wrinkle. That's why cotton clothes get wrinkled in the washing machine.

Ruth Rogan Benerito discovered that adding a chemical like formaldehyde would stop cotton wrinkling because it stopped the cotton getting really wet. Formaldehyde isn't a very nice chemical. It's toxic, yellow and stinks. The clothes didn't last long and they weren't very healthy to wear.

A lot of research followed, and by 1992 (not that long ago) dimethylol dihydroxy ethylene urea (DMDHEU) entered the scene. It was not expensive, it didn't turn yellow and it wasn't toxic. If your clothes are wrinkle-free they probably contain this chemical.

Stain-free clothes

A stain resisting substance was first discovered by Patsy Sherman in the 1950s. While Patsy was working on a latex rubber compound for tubes, she spilt a little of the substance on her canvas shoes. After some time she noticed that where the latex compound had dropped on her shoe, the shoe stayed clean. Oil and water and the stains they carried, just rolled off.

This is how Scotchgard was invented. It is the most well-known way to keep clothes stain-free. Now it's used on furniture because it doesn't feel very nice, but Nano-Tex has created fibres that still feel soft and natural, but which are strong and wearing, don't crease and stains just fall off them.

First, fabric is soaked in a solution which contains billions of tiny particles. The fabric is then heated, and these tiny particles bond or stick to the fibre. The particles actually wrap themselves around the fibre with microscopic whiskers sticking out. The whiskers trap air and are like an invisible protection on the fibre so that stains don't get in. This has been used very successfully on clothes like silk ties.

Waterproofing

Researchers at the University of Zurich are working on a fabric made of polyester coated in silicon nanofilaments. This could be the most waterproof clothing ever – clothes that literally never get wet. The silicon is sprayed over the material like a gas. You can't see or feel the silicon, but it's there and it makes the fabric hydrophobic, and the droplets of water just balance on top, but never soak into the material.

This could be a revolutionary new material for swimming costumes. It is possible that this is also the first step towards self-cleaning clothes, or clothes that control smell. It's probably extremely expensive so people won't stop using waterproof clothing, such as Gore-Tex, yet.

Решение.