Acrylic is produced in two basic versions, cast and extruded. Cast acrylic is produced by mixing the acrylic liquid ingredients in molds, whereas extruded acrylic is produced by continuously pushing acrylic mass through a form, while the chemical process takes place. Cast acrylic is homogeneous and extruded acrylic is heterogeneous. Cast acrylic is usually regarded as better quality than extruded acrylic, although extruded acrylic is less costly.
When acrylic is made by "casting" it will always have less built-in stress – meaning, the molecular weight will be higher and it will machine better, handle pressure/vacuum better, and will be more resistant to heat and certain chemicals. If you are planning on doing any drilling/tapping or machining you will find that the cast tubing product excels. Otherwise, the extruded acrylic tubing is fine and typically less costly.
ADVANTAGES OF CAST ACRYLIC RODS:
Superior chemical resistance - cast acrylic is more resistant to solvents
Machining - on cast acrylic there are almost no burrs
Greater range of thickness up to 4" including those produced as bullet-resistant
Low water absorption, excellent optical properties, good electrical and UV resistivity
Outstanding resistance to long-term exposure to sunlight and weathering
ADVANTAGES OF EXTRUDED ACRYLIC RODS:
Less expensive than glass or cast acrylic
More impact resistant than glass
Good electrical and UV resistivity
Extruded rods have a better tolerance on thickness, typically + or – 10%