Acrylic, polycarbonate and PETG (Polyester Terephthalate Glycol Modified) are all materials available in sheet, rod and tube. They are commonly used for machine guards, covers, displays, and any application that needs to be transparent, since they are colorless. Each of these materials are comparatively priced but each has specific advantages and disadvantages that need to be considered when designing for an application.
Acrylic is available as extruded or cast. Extruded material is the most common and cost effective. Cast sheet, rod and tube is generally considerably more expensive because of the manufacturing process. However, cast material has better optical qualities making is suitable for higher end parts such as medical or food processing. Anything over ½ thick is generally cast.
Extruded acrylic is clear, however the surface can have visible extrusion lines and is not as smooth as cast. Extruded acrylic is used for most applications such as displays, fabricated boxes and signage where you need clear material at a competitive price point. Acrylic can be easily fabricated, cemented, and formed using heat and can also be printed on.
Polycarbonate is available as extruded sheet, rod and tube. It is a very versatile material that is a good choice for machine guarding due to its impressive impact strength. It can be used for many applications where strength and clarity are required. There are a multitude of different grades of polycarbonate such as: general purpose, FDA grade, machine grade, mar-resistant, and more. It should be noted that the standard grade of polycarbonate is not food grade. If a part needs to be certified for food contact, this needs to be determined and specified at the beginning of a project. Polycarbonate can be affected by certain chemicals such as aromatic solvents, esters, and ketones that can attack the material and cause severe deterioration, crazing and cracking.
PETG is a great choice for machine guarding. It is much stronger than acrylic but does not have the impact strength of polycarbonate. The cost is usually somewhere between acrylic and polycarbonate. PETG provides excellent toughness, gloss and chemical resistance. It is easier to fabricate than polycarbonate and the standard grade is made from FDA approved resin. The major problem with PETG that needs to be considered is that it is not resistant to ultra violet (UV) rays. This makes it unsuitable for use in outdoor applications.
Impact Strength Izod
ASTM D-256 ft-lb/in of notch
Acrylic is a great all-purpose material. Extruded is very cost effective. It can be easily fabricated and machined, however it does not have the impact strength of either PETG or polycarbonate. PETG is food grade, has good impact strength but cannot be used if exposed to UV rays. Polycarbonate is the most impact resistant of the three materials discussed here, but can be negatively affected if exposed to certain oils and chemicals.
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