Difference Between Cast and Extruded Acrylic

Main Difference – Cast vs Extruded Acrylic

According to their physical properties, polymers are divided into three groups as thermosets, thermoplastics, and elastomers. Acrylic is a transparent thermoplastic material. The term acrylic is used to name acrylic polymer compounds: polyacrylates such as polymethyl methacrylate. These polymers are generally referred to as plastics. There are two types of acrylic materials based on the production process. They are cast acrylic and extruded acrylic. The main difference between cast and extruded acrylic is that cast acrylic is produced by mixing the acrylic liquid ingredients in molds whereas extruded acrylic is produced by an extrusion method.

Key Areas Covered

1. What is Cast Acrylic
     – Definition, Chemical Properties
2. What is Extruded Acrylic
     – Definition, Chemical Properties
3. Difference Between Cast and Extruded Acrylic
     – Comparison of Key Differences

Key Terms: Acrylic, Cast Acrylic, Extruded Acrylic, Polymer, Thermoplastic

What is Cast Acrylic

Cast acrylic is a form of acrylic material that is produced by mixing the acrylic liquid ingredients in molds. Cast acrylic is a homogenous material that has equivalent properties in all directions. In the production process, the liquid ingredients are pumped into a mold made from glass plates. Then the mold is submerged in warm water. Here the polymerization process takes place.

Cast acrylic is more chemical resistant when compared to extruded acrylic materials. When laser cutting is done, there are no burrs in edges of the cast acrylic sheet. This means it gives polished edges. Cast acrylic is available in a wide variety of colors (colored using master batch pigments).

Figure 1: Cast Acrylic Materials are Available in Different Colors

When thermoforming cast acrylic, the color of the material can change (thermoforming is a process in which a plastic sheet is heated to a suitable temperature and shaped in a mold, and trimmed to the desired size). For example, matt colored surfaces may become more clear or clear surfaces may become matt colored. Cast acrylic sheets are hard to bend and shape. Cast acrylic materials are more resistant to scratches. Cast acrylic is hard to flame polish. The commercial name of cast acrylic is Perspex. Cast acrylic can be formed in various thicknesses.

What is Extruded Acrylic

Extruded acrylic is a form of acrylic polymer materials produced by an extrusion method. These materials are heterogeneous due to the production process. Extruded acrylic is formed by pushing acrylic mass through a form. Therefore, extruded acrylic has varying properties depending on the direction.

Chemical resistant of extruded acrylic material is low when compared to cast acrylic. When laser cutting extruded acrylic sheets, the edges remain with burrs. This means it does not give fine edges. But these edges can be polished. Extruded acrylic materials behave differently during thermoforming since they have varying properties in different directions.

Extruded acrylic is not available in different colors as cast acrylic. Therefore, there is no considerable color change when thermoforming extruded acrylic. However, it is easy to bend and thermoform. Extruded acrylic has a better tolerance for thickness.

Difference Between Cast and Extruded Acrylic

Definition

Cast Acrylic: Cast acrylic is a form of acrylic material that is produced by mixing the acrylic liquid ingredients in molds.

Extruded Acrylic: Extruded acrylic is a form of acrylic polymer materials produced by an extrusion method.

Color

Cast Acrylic: Cast acrylic materials are available in a wide variety of colors.

Extruded Acrylic: Extruded acrylic is limited in colors.

Chemical Resistance

Cast Acrylic: Cast acrylic is more resistant to chemicals.

Extruded Acrylic: Extruded acrylic is less resistant to chemicals.

Scratch Resistance

Cast Acrylic: Cast acrylic is more scratch resistant.

Extruded Acrylic: Extruded acrylic is less scratch resistant.

Laser Cutting

Cast Acrylic: Cast acrylic has fine edges after laser cutting.

Extruded Acrylic: Extruded acrylic has burr edges after laser cutting.

Flame Polishing

Cast Acrylic: Cast acrylic is hard to flame polish.

Extruded Acrylic: Extruded acrylic is easy to flame polish.

Thermoforming

Cast Acrylic: Thermoforming of cast acrylic can change the color.

Extruded Acrylic: Thermoforming of extruded acrylic has no considerable color change.

Heat Bending

Cast Acrylic: Heat bending of cast acrylic is hard.

Extruded Acrylic: Extruded acrylic is easy to heat bend.

Conclusion

Acrylic is a thermoplastic polymer material. It is available in two different types based on the production process. They are cast acrylic and extruded acrylic. The main difference between cast acrylic and extruded acrylic is that cast acrylic is produced by mixing the acrylic liquid ingredients in molds whereas extruded acrylic is produced by an extrusion method.

Reference:

1. “Cast acrylic versus extruded acrylic”, pmma.dk, Available here.
2. “Cast acrylic.” Wikipedia, Wikimedia Foundation, 25 Dec. 2017, Available here.
3. “Difference between CAST Acrylic & EXTRUDED Acrylic sheets?” Access Plastics, Available here.

Image Courtesy:

1. “Coloured cast acrylic by Midton Acrylics” By Craig Cameron – Own work (CC BY-SA 3.0) via Commons Wikimedia