[!abstract] Contents

• Terminology
• History and demand
  • Discovery and early use
  • Use in construction
• Composition and production
  • Manufacturing process
  • Product forms
• Grades and types
• Properties
  • Physical
  • Thermal and moisture
  • Fire behavior
  • Durability
• Standards
  • Test methods
• Uses in buildings
  • Building elements
  • Pros and cons
• Design considerations
  • Movement
• Sustainability
  • Recycled content and end of life
• Manufacturing and cost
  • Main manufacturers and suppliers
• Sources

Terminology

• PMMA: poly(methyl methacrylate)
• Plexiglas / Perspex / Lucite: trade names for acrylic sheet (Röhm & Haas, ICI, DuPont)
• Cell cast: sheet cast between glass plates; highest-quality acrylic sheet
• Extruded: continuous sheet; lower cost, less thermally stable than cast
• Tg: glass transition temperature, where forming begins

History and demand

Discovery and early use

• 1843: acrylic acid first made; 1865: methacrylic acid
• 1928: PMMA developed in several laboratories; 1933: Röhm & Haas AG first marketed it as Plexiglas
• 1936: ICI began the first commercially viable acrylic safety glass; used in WWII for periscopes, aircraft windscreens, and canopies

Use in construction

• Civilian uses followed WWII; building examples include the 1972 Munich Olympic Park roofing and the Houston Astrodome ceiling (Lucite)

Composition and production

Manufacturing process

• Emulsion, solution, or bulk polymerization, usually by radical initiation
• Cell casting gives the highest-quality sheet; extrusion and injection molding are also used

Product forms

• Cast and extruded sheet, molded sanitary ware, and laser-cut or prism-based daylighting panels

Grades and types

• Cast acrylic: better thermal stability, solvent-crazing resistance, and surface finish than extruded
• Extruded acrylic: continuous sheet production

Properties

Physical

• Density: 1.17 to 1.20 g/cm³ (about 74 lb/ft³), roughly half that of glass
• Light transmission: up to 92 percent of visible light at 3 mm; about 4 percent reflection per surface

Thermal and moisture

• Glass transition: 105°C (221°F) for atactic PMMA; commercial grades 85 to 165°C (185 to 329°F)
• Coefficient of thermal expansion: (5 to 10) × 10⁻⁵ per °C, about 2.8 to 5.6 × 10⁻⁵ in./in./°F, described as relatively high
• Water absorption: tensile strength decreases as water absorption increases

Fire behavior

• Ignition temperature: 460°C (860°F); combustion produces carbon dioxide, water, carbon monoxide, and low-molecular-weight compounds including formaldehyde

Durability

• UV: filters UV below about 300 nm like window glass; coatings or additives absorb 300 to 400 nm; environmental stability superior to polystyrene and polyethylene

Standards

Test methods

• ASTM D635: burning rate and extent of plastics (CC1, CC2 classification)
• ASTM D1929: self-ignition temperature
• ASTM D2843: smoke density

Uses in buildings

Building elements

• Showers and Tubs: acrylic tub and shower receptors
• Skylights and Roof Windows: dome and pyramid plastic glazing
• Wall Sconces: shades and diffusers

Pros and cons

Pros

• Light transmission up to 92 percent
• About half the density of glass
• Better outdoor stability than polystyrene or polyethylene

Cons

• High thermal expansion
• Combustible, igniting at 460°C
• Strength falls as water absorption rises

Design considerations

Movement

• Expansion about 0.3 to 0.7 in. per 10 ft for a 100°F swing (calculated from 2.8 to 5.6 × 10⁻⁵ in./in./°F)

Sustainability

Recycled content and end of life

• Pyrolysis at 400°C or higher recovers monomer; a chlorinated-solvent UV method reports 94 to 98 percent yields

Manufacturing and cost

Main manufacturers and suppliers

• Trinseo
• Mitsubishi Chemical Group
• Arkema
• Evonik

Trade association: American Chemistry Council.

Sources

• Wikipedia: Poly(methyl methacrylate), https://en.wikipedia.org/wiki/Poly(methyl_methacrylate)
• UpCodes: 2024 IBC Chapter 26 plastic, https://up.codes/viewer/department-of-defense/ibc-2024/chapter/26/plastic