Chemistry 1E

Chemistry 1E

1. Goretex

   • Goretex is a waterproof but breathable fabric
   • Goretex is a laminate of nylon and PTFE layers

2. Polymer

   • Carbon atoms in polymer chains are linked by strong covalent bonds
   • Polymer chains are either linked together by weak intermolecular bonds or strong covalent bonds

3. Key Processes

   • Disposal of Polymers
     • Landfill. Waste polymers are disposed of in landfill sites. This uses up valuable land, and suitable sites often fill up quickly
     • Incineration. Polymers release a lot of heat energy when they burn. This energy can be used to heat homes or generate electricity. But there are problems with incineration. Carbon dioxide is produced, which adds to global warming. Toxic gases are also produced, unless the polymers are incinerated at high temperatures
     • Recycling. Many polymers can be recycled. This reduces disposal problems and the amount of crude oil used. But first the different polymers must be separated from each other. This can be difficult and expensive
   • Gore-Tex has the desirable properties of nylon, but is also 'breathable'. It lets water vapour from sweat pass to the outside, but it stops rain drops from passing to the inside. Clothing made of Gore-Tex is very useful to hikers and other people who work or play outside
     • The PTFE contains a lot of tiny holes called pores - there are around 14 million per square millimetre. Each one is too small for water droplets to pass through, but big enough to let water molecules from sweat out
   • Strong covalent bonds
     • Cross-linking is where the polymer chains are chemically joined together in places, by covalent bonds. The polymer molecules cannot slide over each other so easily. This makes materials tougher and less flexible, and they cannot be easily stretched. Cross-linking also gives materials high melting points
   • Weak intermolecular bonds
     • Many polymers, such as polyethene, contain long molecules that lie side by side. These can uncoil and slide past each other, making the material flexible
   • Some polymers are water-soluble, which means they dissolve in water. These polymers are often used to wrap products such as dishwasher tablets and pouches containing detergent for washing machines
   • Chemists are developing new types of polymers. Most polymers, including polyethene and polypropene, are not biodegradable. This means microorganisms cannot break them down, so they may last for many years in rubbish dumps. However, it is possible to include chemicals that cause the polymer to break down more quickly. Carrier bags and refuse bags made from degradable polymers are already available