Continuously cast acrylic is produced from monomer. This type of acrylic is polymerized between two stainless steel belts. The belts are typically 108 to 110 inches wide. Each belt has a seam or weld line at 54 or 55 inches. The 108-inch wide belt is actually made up of two belts which are welded together. The seam in the belt causes a slight distortion in the sheets when viewed at acute angles. Continuous cast acrylic sheet sizes are limited in width by the width of the belts that are used to polymerize the sheets. Continuous cast acrylic is produced in thickness ranging from .100/2.5 mm through .471/12 mm thick. Continuous cast acrylic generally has a higher molecular weight than continuously processed or extruded acrylic sheet. It forms well, it has good thickness tolerances and it can be produced on reels. Continuous cast acrylic is generally considered inferior to cell cast acrylic for optical applications.

Continuously processed acrylic sheet is extruded from polymer. Acrylic polymer or acrylic pellets are melted in a hopper and forced through an extrusion die. As the sheet comes out of the die, it passes through a stack of highly polished drums called a roll stack. The roll stack is used to polish the sheet and control the thickness. Some customers prefer a specific manufacturer of continuously processed acrylic sheet. The sheets differ primarily due to the optical brighteners that the manufacturer uses to control edge color, the quality of the extruder that is used to manufacture the sheet and the downsteam equipment that is used in the final stages of polymerization. Most manufacturers have begun to produce continuously processed acrylic sheet with a higher molecular weight. The molecular weight of this material is similar to continuous cast acrylic sheet.

Continuously processed acrylic sheet is the most commonly sold acrylic sheet in the U.S. market. It has excellent thickness tolerances, shorter cycle times for solvent cementing, bending and forming when compared to cell cast acrylic sheet. The width of the sheet is limited by the width of the extruder, but any length can be achieved. The optical quality of continuously processed acrylic sheet is generally considered to be inferior to cell cast acrylic sheet, but is considered acceptable for most applications, including the framing lens for fine arts. It is also used as the main substrate for the production of acrylic mirror. The production minimums for colors are generally higher than batch minimums for cell cast acrylic.

For more information, contact Mike at Ultra Acrylics, Inc.