This article gives a brief overview of how the chemistry behind plastics helps give them environmentally-beneficial properties. It has been written to support the chat with Anton de Vries on 27 November 2008.
When it comes to protecting the climate, choice of materials is crucial. To give an example, the materials used to construct a car will determine how heavy it is. The heavier it is, the more fuel it will burn, and the more carbon dioxide it will produce. Using materials that reduce a car’s weight will therefore help protect the climate.
Materials have different properties that make them suited to different applications. Understanding the chemistry behind different materials therefore allows us to understand how they can protect the climate.
One important consideration with materials is how much fossil fuel they save during their use phase compared to the fuel needed for their production. From this perspective plastics are an eco-efficient material, as they enable efficient energy use during their use phase.
Plastics are made by linking together organic molecules. The quantity and the structure of theses molecules (also called monomers) determine the property of the plastic material. That gives plastics a “chameleon” characteristic and makes them adaptable to a wide range of applications.
In order to further customise plastics for an application and a manufacturing process additives are needed, e.g. glass fibres, minerals, pigments and other chemicals. There are many different options for combining plastics with other materials. This versatility has many advantages, since plastics can be customised to fit the needs of a particular application. Plastics can be transparent, some are extremely tough, some are flame retardant, some are compatible with body fluids etc. Other materials have a limited variability and are often heavier.
An important achievement for plastics is that they are possible to reproduce in consistent shapes and properties several million times, something that nature cannot do.
Something that also matters for all people around the world is climate change. By producing more renewable energy, we create fewer greenhouse gas emissions. This is a sector where plastics are indispensable. Many technical components needed for the energy producing devices are only possible due to plastics. For example, wind turbines (technology that converts the kinetic energy of wind into mechanical energy) are making use of increasingly sophisticated engineering techniques made possible by plastics to increase the possibilities of wind energy. The blades of many modern wind turbines are made from fibre-reinforced plastics. Such composites result in blades that are rigid, highly durable and lightweight. Their characteristics – high strength, low weight – make plastics an ideal material for wind generators, enabling easier installation, improved durability and reduced maintenance.
The versatility of the material also contribute significantly to increase energy efficiency: savings can be achieved by using plastics insulation materials in buildings, by using light weight plastics in transportation, and by using plastics packaging to reduce spoilage of food. In case plastics would not exist, then the total mass of the used materials would increase by a factor 3.9, the energy consumption by 26% and the CO2emissions by 56% (GUA, 2004).
Another field worth mentioning is consumer electronics, where the miniaturisation of electronic equipment would not be possible without plastics. The computers in the early 1970s required a complete room, while today – thanks to plastics – a small laptop can do even more.
Recycling certain types of plastics also contributes to protecting the climate. Recycling is all about chemistry. Most of the plastics that are in use are thermoplastics. After they have been collected and sorted, they can be melted again and reshaped into other articles. This enables plastics to be used in a number of different formats throughout their life cycle. One good example are the front screens of mobiles: the different colours front plates are made from recycled polystyrene earlier used as disposable coffee cups. This is not possible with thermoset plastics, which have a molecular structure that makes the material decompose if heated to very high temperatures.
Understanding the properties of the materials that we rely on in our daily lives has allowed many technological advances that reduce consumption of energy and natural resources. Firstly by saving weight. Secondly by improving the combustion performance of car engines either directly (e.g. surface quality of air inlet manifolds) or indirectly by enabling to place energy saving electronic parts near the engine block. Plastics also allow easier shaping which helps to lower the air friction or to increase the aerodynamics.