Higher Chemistry Unit 2(e) Recent polymer developments

After today’s lesson you should be able to: state which type of polymer Kevlar is. explain why Kevlar is strong and give some of its uses. state the property of poly(ethenol) and explain how this property can be altered. explain how poly(ethenol) is made. state the property of the polymer made from poly(ethyne) and how this property occurs. state the property of poly(vinylcarbazole) and its use. state the property of biopol. state the property of the polymer made from low density polythene.

Kevlar Kevlar is an aromatic polyamide. It is extremely strong due to the way in which the rigid, linear molecules can pack together.

Properties and Uses of Kevlar It is heat and fire resistant so is used in the clothing worn by firefighters. It is extremely strong so is used in body armour which offers protection against handgun fire and knife slashes. It has a high resistance to abrasion so is used in brake pads, clutch linings and the protective suits of motorcyclists. It is lightweight so is used as reinforcements in car tyres and to make ropes and cables.

Poly(ethenol) It would be assumed that poly(ethenol) would be made from the monomer ethenol but this does not exist. Poly(ethenol) is made from the polymer poly(ethenyl ethanoate) by a process known as ester exchange.

Properties of Poly(ethenol) Poly(ethenol) is soluble in water. It’s solubility depends on the percentage of hydroxyl groups present or the percentage of acid groups which have been removed. The more hydroxyl groups present or the less acid groups present the LESS soluble the polymer. This is due to the hydrogen bonds forming between the poly(ethenol) chains rather than between the poly(ethenol) chains and the water molecules.

Uses of poly(ethenol) Used to make hospital laundry bags. When any infected laundry is placed in a washing machine the bag dissolves releasing the laundry. Poly(ethenol) is only soluble in hot water so that damp laundry will not dissolve the bag. Used to make soluble stitches for surgery. Takes away the need to have stitches removed after the wound has healed.

Poly(ethyne) Poly(ethyne) is made form the monomer ethyne. It contains alternating single and double carbon to carbon bonds.

Properties and uses of poly(ethyne) Poly(ethyne) has delocalised electrons like benzene. Because of these free moving electrons poly(ethyne) can conduct electricty. If poly(ethyne) is ‘doped’ with iodine it conducts 100,000,000 times better. It is used as an ‘antistatic’ material in high performance loud speakers.

Poly(vinylcarbazole) Poly(vinylcarbazole) is made from the monomer vinylcarbazole. It exhibits photoconductivity i.e. it conducts electricity when light is shone on it. It is used in photocopiers.

Biopol Biopol is a natural polyester. It is a biodegradable polymer. It was launched in 1990 but production was ceased in 1999 due to its high production costs and a shift towards recyclable polymers.

Photodegradable plastics The structure of low density polythene can be modified to produce a photodegradable plastic. The photodegradable plastic either has bonds in its structure that can be weakened and broken by sunlight, or it contains a chemical additive which absorbs light and then attacks the polymer and breaks some of the bonds. Once a photodegradable plastic is exposed to light it begins to break down.

Photodegradable plastics tend to break down into small particles of plastic rather than decomposing completely. The idea is that these small pieces will then biodegrade. Unfortunately, they are often not biodegradable and so remain in the environment. At present, most plastic waste ends up in a landfill site where it is buried in a dark hole in the ground. Under these conditions, photodegradation cannot take place.