Proper procedures & equipment for cementing ACRYLITE® Resist sheet

Cementing
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Proper procedures & equipment for cementing ACRYLITE® Resist sheet

ACRYLITE® Resist™ 65 acrylic sheet (formerly known as ACRYLITE PLUS® acrylic sheet) can be fabricated using the same machinery that is used on ACRYLITE® extruded (FF) acrylic sheet. Fabrication techniques are nearly the same. Minor modifications may be necessary due to the sheet's unique properties. Its greater impact resistance and special formulation require special care in certain machining operations. In general, equipment should be stable, vibration free and show a minimal amount of tool wobble (run-out). For best results, follow the recommendations below and refer to the information prepared for ACRYLITE® extruded (FF) sheet for additional information.

Cementing

Methylene chloride-based solvent cements, typically used for acrylic sheet fabrication, work well with ACRYLITE® Resist™ 65 sheet. These cements produce strong joints that will meet the needs of most display applications. Where additional strength is required, "wickable" cyanoacrylate based cements will produce even stronger cement joints.

ACRYLITE® Resist™ 65 sheet will easily bond to standard acrylic sheet because both materials are attacked by the same cements, permitting the use of acrylic, including acrylic profiles in conjunction with ACRYLITE® Resist™ 65 sheet.

ACRYLITE® Resist™ 65 sheet's excellent craze resistance allows it to be used in many situations where normal cementing would result in crazing. This provides significant benefits in applications where line bends or cold bends are adjacent to a cemented edge. Typical acrylic fabrication techniques for edge preparation can be used with success with ACRYLITE® Resist™ 65 sheet. Edge finished, jointed, or clean saw cut edges are all suitable for cementing. In some instances, saw cut edges may work better because the edge roughness allows more space for the cement to flow into the joint. To achieve the best results when capillary cementing with typical methylene chloride-based solvent cements or cyanoacrylate based cements, the following recommendations should be followed:

  • Ensure a smooth, clean, low stress edge.
  • Apply cement along the entire length of the cement joint. Unlike with standard acrylic sheet, the cement will not flow to the ends of the cement joint if the application of cement is started or finished more than 1/4-1/2" from the ends. Failure to fill the entire length of the cement joint greatly reduces strength.
  • Apply a generous amount of solvent cement to the surfaces being joined by tipping the vertical piece slightly so that its edge can accept more cement, by using a larger diameter applicator tip for increased cement flow, or by providing space at the joint by shimming the edge (0.002"-0.004").

Joint set-up time will vary depending on the exact formulation of the cement and the temperature and humidity of the cementing environment. Cement joints made with ACRYLITE® Resist™ 65 sheet will obtain initial soft strength approximately 30 minutes after application of the cement. They will begin to harden about 3 hours after cement application, but will not approach full strength for 24-48 hours. As a general rule, set up time will be slightly longer than is normally required with unmodified acrylic sheet.

With cyanoacrylate-based cements, the chemical reaction that hardens the cement joint is triggered by moisture in the acrylic sheet and the atmosphere. Therefore, the rate of the curing process is dependant on the rate at which moisture in the air and in the sheet can diffuse to the cement joint. Usually, 48 hours is required for the cement joint to reach full strength, which will be as strong as the material itself. Extra care should be taken when handling parts to avoid cement smudges. The resulting of white marks can usually be removed by wiping with kerosene followed by rinsing with mild soap and water.

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