PMMA acrylic
Selecting acrylic by grade, casting or extrusion route, optical requirements and fabrication history.
Tags: materials, polymers, acrylic
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Identity and specification
The ACRYLITE GP cast sheet table gives 99°C HDT at 264 psi under ASTM D648 and separately lists 82°C maximum recommended continuous service temperature, subject to the application. Evaluate load, support and heat exposure for the installed sheet. ACRYLITE GP physical properties
PMMA is poly(methyl methacrylate), a thermoplastic commonly called acrylic glass. PLEXIGLAS identifies PMMA products supplied as sheet, tube, rod and film, with clear, translucent, opaque and colored variants. The family name does not identify a particular optical, impact-modified or surface-treated grade. Specify the manufacturer, full grade, color, supplied form, thickness and required surface quality. PLEXIGLAS: GS/XT product overview
Cell cast and extruded sheet
ACRYLITE describes its cell-cast sheet as polymerized in individual cells between glass plates. Its continuously manufactured extruded sheet uses lower-molecular-weight polymer than its cell-cast product. The manufacturer lists tighter thickness tolerance and faster cementing and thermoforming among the extruded sheet's advantages; cast sheet offers less tendency to melt or chip during machining, slightly better chemical resistance and a wider available thickness range. These are comparisons within the supplier's products, not a universal ranking of all acrylic grades. ACRYLITE: cast versus extruded sheet
Choose the route around the requirement. A dimensionally constrained assembly may prioritize thickness tolerance, while a machined optical component may prioritize distortion and edge finish. Ask for actual thickness tolerances and inspection criteria for the ordered size; do not infer them from the production-route label alone.
A bounded property example
ACRYLITE cell-cast sheet (GP) technical information 1235G, 09/24 lists typical properties for 6 mm thickness unless otherwise noted. It explicitly says these values should not be used for specification purposes. ACRYLITE: GP physical properties
| Property | Typical value and stated method |
|---|---|
| Tensile strength | 69 MPa, ASTM D638 |
| Tensile modulus | 2,800 MPa, ASTM D638 |
| Total light transmission, clear material | 92%, ASTM D1003 |
| Heat-deflection temperature | 99 °C at 264 psi, ASTM D648 |
| Maximum recommended continuous service temperature | 82 °C, subject to application |
Source: ACRYLITE GP, 1235G, 09/24.
The heat-deflection result is a test under a stated load, not an operating-temperature guarantee. The sheet also warns about deformation under continuous loads and insufficient support. Panel span, support, temperature and load duration therefore belong in the component assessment. A tensile coupon value does not establish pressure-vessel, machine-guard or safety-glazing suitability.
Optical and weathering boundaries
UV resistance and UV transmission describe different things. PLEXIGLAS technical information 211-1 distinguishes UV-absorbing grades from UV-transmitting special grades, including products intended for tanning applications. A weather-resistant clear sheet need not transmit the wavelengths required by a sensor, curing source or optical experiment. Request the spectral curve for the exact grade, color and thickness. PLEXIGLAS: GS/XT technical information
Likewise, a yellowing warranty is a product-specific commercial commitment. ACRYLITE Premium FF links separate warranty documents for clear and white products; its general product claims do not supply a lifetime guarantee for every acrylic, coating or installation. Check the applicable document and exclusions when outdoor appearance is contractual. ACRYLITE: Premium FF documentation
Expansion and mounting
ACRYLITE's glazing guidance lists a linear expansion coefficient of 0.000040 in/in/°F for its cast and Premium FF sheets, with different values for some sign and impact-modified products. It calculates movement as length × temperature difference × coefficient. Use the coefficient for the actual grade and preserve the temperature units. ACRYLITE: expansion and contraction
Illustrative calculation: a free 48-inch length undergoing a uniform 50 °F rise gives 48 × 50 × 0.000040 = 0.096 inch, approximately 2.44 mm, of expansion. This is total free movement under the stated assumptions, not a prescribed hole clearance. Actual mounting must account for restraint, temperature gradients, fastener arrangement and support engagement. Verify the installation design rather than clamping the sheet tightly and assuming its nominal size remains fixed.
Machining, forming and stress
ACRYLITE machining brief 1319-11G, 10/24 warns that poor tools or equipment can produce notches and overheating. It emphasizes chip clearance, stable machinery and cooling, and requires compatibility testing for cutting emulsions because unsuitable fluids can cause crazing. It also cautions against sharp-edged threads because of acrylic's notch sensitivity. Qualify tools and fixtures on the actual grade and thickness; a polished edge alone does not demonstrate a low-stress part. ACRYLITE: machining brief
Thermoforming needs control of the sheet's core temperature, not just heater settings or a surface reading. The supplier's forming guidance explains that thick sheet can overheat at the surface before its core is ready, and that manufacturing orientation influences shrinkage. It recommends trials to separate manufacturing-related dimensional change from forming shrinkage. Verify wall thinning, optical distortion and final dimensions on the formed part. ACRYLITE: thermoforming guidance
ACRYLITE extruded-sheet annealing brief 1319-12E, 10/24 describes stress relief after operations including machining, bending, cementing and flame polishing. It calls for controlled, uniform heating, appropriate support and slow cooling. Follow the grade-specific procedure, including the required interval after cementing, rather than applying a universal acrylic oven cycle. Annealing reduces stress-related failure risk; it does not make an incompatible cleaner or adhesive acceptable. ACRYLITE: annealing brief
Cleaning and acceptance
ACRYLITE recommends gentle cleaning with a soft damp cloth or mild soap and lukewarm water, and warns against dry abrasive wiping, window-cleaning sprays and solvents such as acetone. Incompatible materials can scratch or induce fine cracking called crazing. Confirm the complete cleaner formulation and concentration for the particular sheet and fabricated condition; compatibility cannot be inferred from an ingredient name alone. ACRYLITE: cleaning and maintenance
For purchasing and qualification, retain:
- Exact grade, color, surface treatment, production route and thickness tolerance.
- Property-source revision, test method and specimen thickness.
- Optical requirements and inspection lighting or measurement method.
- Machining, forming, bonding and stress-relief history.
- Supports, fasteners, loads, temperature range and cleaning sequence.
- Finished-part tests and any required application-specific approvals.
The dated PDFs above establish the cited editions; undated web guidance is identified by its page rather than an inferred revision date. Keep supplier typical values, contractual acceptance limits and measured part performance separate.