Polymers have a low density, they can be used in electrical insulation and they have low thermal conductivity, but they also swell with water, require low temperature and have a sensitivity to UV light. Polymers are easy to produce and cost effective, but many are flammable and have a certain toxicity.
Polymers are classified into one of three categories. Thermoplastics flow when heated and solidify when cooled. Thermosets decompose when heated and often decompose due to the cross links between long chains, making them unstable. Elastomers are rubbery at room temperature and must be heated to a high temperature to react.
Polymers are used in a number of different industries. Synthetic polymers are most often used in the production of plastics. These include things like polyethylene and polycarbonate. Natural polymers are breathable, renewable resources that are used in a variety of different items like clothing, compost bags and carrying bags.
Unlike metals and ceramics, polymers don't require finishing to look good and last for a long time. Polymers such as plastic can be easily formed to make almost any imaginable shape and they are normally durable. However, many polymers cannot take exposure to extreme temperatures and don't always hold their shape in water.