There are few differences between the physical properties of Cast Perspex Acrylic and Extruded Perspex Acrylic sheets. Both show excellent resistance to natural ageing. The main differences lie in their thermal and chemical properties and the way they are processed and used. The two materials are different in nature and respond differently to certain processes.
The Cast manufacturing process leads to slight variations in the thickness of sheets whereas the thickness of Extruded sheet varies very little, if at all. Cast has an isotropic response to temperature with a maximum shrinkage of 2% in all directions. However, the extrusion process applied to Extruded sheet leads to differences in shrinkage depending on the thickness and direction of extrusion.
Extruded acrylic sheet has reduced mechanical properties, however it does give process advantages when heating, bending and vacuum forming, and has a better thickness tolerance than cast acrylic sheet. Extruded sheets are ideal for general glazing applications and the much lower viscosity when hot, makes it more ductile than Cast Acrylic.
Cast Acrylic sheets offer greater thermal stability and better resistance to crazing when exposed to solvents. The thermoforming range for cast sheets is wider. They can be reworked hot, which is not always possible with extruded sheets. The surface finish, flatness and optical properties of Cast Acrylic are all superior to those of Extruded Acrylic sheets.
