Acrylic is an extremely versatile material which is used in a wide range of environments. Acrylic sheeting is available in a huge range of variations, including; clear, coloured, mirrored, frosted and even with a brushed aluminium effect.
Extruded acrylic and cast acrylic are the two main types of sheet acrylic you will come across. Although they may initially look similar, the two have quite different properties and one is also much more expensive than the other.
It is important to be aware of the differences between the two so you can pick the type most suitable for your needs.
Extruded and cast acrylic sheets differ mainly in their thermal and chemical properties which are caused by the manufacturing process. There are also several other differences as outlined below which you may wish to consider when choosing acrylic sheet for your home DIY project.
Key differences you should be aware of when working with acrylic sheets:
Due to the way the sheets are made cast acrylic tend to have slight variations in the thickness of the sheet whereas extruded sheets are much more uniform, with next to no variation. This makes extruded acrylic ideal for vacuum forming or situations where more detailed precise shapes are needed.
Cast acrylic has an isotropic response to temperature meaning there is a maximum shrinkage of 2% in all directions. It may be important to note that acrylic expands and contracts at a much greater rate than glass. Extruded acrylic, on the other hand, shows differences in shrinkage depending on the thickness and direction of extrusion.
Benefits of Extruded sheets
- Reduced mechanical properties mean process advantages over cast acrylic when bending, heating and vacuum forming
- Better thickness tolerances
- Lower viscosity when hot means it is more ductile than cast acrylic
Benefits of Cast acrylic sheets
- Better thermal stability
- Higher resistance to crazing (when a network of very small cracks form) when exposed to solvents
- Wider thermoforming range than extruded acrylic
- Better ability to be reworked hot
- Superior surface finish and optical properties
Both types of acrylic benefit from being durable and long lasting, showing excellent resistance to natural aging. Most manufactures will guarantee against noticeable yellowing for approximately 10 years.
Often it may not be made obvious which type of acrylic you are buying, especially online. Cast acrylic can be as much as double the price of extruded acrylic so if nothing is mentioned and it seems cheap, the chances are it is extruded acrylic.