Designer polymers

What are designer fibres? Designer fibres are found in the fabrics of the clothing we wear to stay comfortable outdoors or when playing sports. Lightweight waterproof clothing used to be made from nylon and PVC but sweat often condensed inside the materials making them cold, wet and uncomfortable. Today, special polymers are woven into fabrics to make them breathable, elastic or insulating. The properties of many of these designer fibres were discovered by accident.

What are insulating fibres? Insulating fabrics help to keep the body and extremities warm during cold weather. Thinsulate™ is a synthetic insulating fabric made from thick polyester ‘staple’ fibres and very thin polypropylene fibres. The lightweight polypropylene fibres in Thinsulate™ are about 10 times thinner than those in other fabrics. This means that more air can be trapped in the fabric, preventing the body's heat from escaping.

How do insulating fabrics work?

What are elastic fibres? The first elastic fibres known as elastane or ‘spandex’, were created from polyurethane in the 1940s by DuPont, and later became known as Lycra®. When mixed with traditional or man-made fibres, elastic fibres allow clothes to stretch and recover their shape. Unlike traditional rubber thread, Lycra® fibres are lightweight and resistant to damage from sunlight, sweat and detergents.

What is Lycra ® made from? Lycra® fibres are made up of two distinct segments: A soft segment made from polyester. When Lycra® is stretched, the polyester segments expand up to six times their original length without being damaged. When released, the polyester segments contract, twisting and looping around themselves. A hard segment made from urethane. Urethane stretches very little but is rigid and gives Lycra® a high tensile strength (resistance to tearing).

How do elastic fibres work?

What are breathable fabrics? Breathable fabrics are designed to keep the wearer warm and dry in extreme weather but still allow sweat to escape. GORE-TEX® is a breathable fabric made from a microporous membrane made from expanded polytetrafluoroethene (ePTFE). The ePTFE is very fragile so it is laminated between layers of nylon or polyester for added strength. It is coated with a special covering to protect against oils, cosmetics and other substances that could cause damage.

How does Gore-Tex ® work?

Bullet proof vests Bullet-proof vests (or soft body armour) are made from tightly woven fibres and are much more flexible and comfortable than hard body armour. Many bullet-proof vests are made from Kevlar® – a synthetic fibre called poly-paraphenylene terephthalamide. Kevlar® is used as a protective material because it is: flexible and lightweight heat resistant five times stronger than steel (mass-for-mass)

Discovering Kevlar®

Kevlar® fibres and bullet proof vests In bullet-proof vest, several layers of Kevlar® fibres are tightly interlaced with each other and sandwiched between layers of plastic film. These layers are then woven to an outer layer of normal ‘carrier’ fabric. When a bullet or other object strikes the vest, it pushes back on the Kevlar® fibres at the point of impact. As this happens, each fibre extends horizontally and vertically, distributing the impact over the whole fibre network.

How do bullet proof vests work?

What is polymorph? Polymorph is a biodegradable polymer that becomes soft and mouldable when heated to about 60 °C, for example with hot water or a hair dryer. The polymorph can then be moulded into any shape required. As it cools, it sets hard and can be drilled, sawn and filed. If the polymorph is heated again it will become semi-liquid and can be fully reshaped. Where might polymorph be useful?

How does Teflon® work? Teflon® was created by accident in 1938 when scientists at DuPont experimented with refrigeration gases. The scientists produced a waxy resin – polytetrafluoroethene (PTFE) – that was inert to almost every chemical and stable over a wide temperature range. PTFE is a chain of carbon atoms surrounded by fluorine atoms. The bonds between carbon and fluorine are very strong, and the fluorine ‘protects’ the carbon chain. C F Teflon® is the slipperiest material in the world. In which products do you think it would be useful?

What are hydrogels? Hydrogels are a network of superabsorbent water-soluble polymers that can be natural (e.g. made by seaweed) or synthetic. They are found in many products such as: nappies and sanitary towels contact lenses water-release granules for plants Hydrogels can be made into thin films which make ideal wound dressings. They absorb liquid from the wound and swell producing a soft, non-stick cushioning gel. Antiseptics can be added that are released directly into the wound.