PMMA-HI FR (Flame-retardant impact grade)
Flame-retardant grade
ASTM D788 · JIS K6717 · GB GB/T 7134 Type 2 · ISO 8257-2 PMMA-HI
For electrical enclosures, luminaire diffusers and rail/transport parts needing a flammability rating.
Values for the FR condition
Other PMMA-HI grades and fills
PMMA-HI is listed in 4 conditions; see the grade overview at PMMA-HI.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
FRThis page Flame-retardant impact grade | For electrical enclosures, luminaire diffusers and rail/transport parts needing a flammability rating. | 43 | 45 | 15 | 86 Shore D |
High-flow impact grade | Choose for thin-wall light guides and long flow paths where fill pressure matters more than maximum toughness. | 45 | 47 | 22 | 85 Shore D |
Pigmented / opaque impact grade | Coloured or white-opaque compounds for cosmetic housings, sanitary and appliance parts where gloss and scratch resistance beat ABS. | 46 | 48 | 26 | 86 Shore D |
Heat-resistant impact grade | Use where parts see 90–110 °C service (headlamp inner lenses, near-LED optics) and standard HI would distort. | 51 | 53 | 22 | 88 Shore D |
What is PMMA-HI FR?
PMMA-HI FR is PMMA-HI in the FR grade — for electrical enclosures, luminaire diffusers and rail/transport parts needing a flammability rating. PMMA-HI FR has a yield strength of 43 MPa (6.24 ksi) and a tensile strength of 45 MPa (6.53 ksi) — weaker than 61% of polymer grades. Elongation at break is 15% and the elastic modulus is 2.3 GPa (0.334 Msi). PMMA-HI FR has a density of 1.21 g/cm³ (0.0437 lb/in³), heavier than 60% of polymer grades. Its glass-transition temperature is 102°C (216 °F).
Advantages
- Polishes to a fine finish — 85/100, better than 92% of polymer grades
- Good UV / weathering resistance — 82/100, better than 87% of polymer grades
- Low, predictable mold shrinkage — 0.45%, better than 77% of polymer grades
Limitations
- Needs corrosion protection — 68/100, worse than 85% of polymer grades
- Limited service temperature — 66°C (151 °F), worse than 80% of polymer grades
- Difficult to weld — 18/100, worse than 76% of polymer grades
PMMA-HI FR properties
Typical room-temperature values for PMMA-HI FR; 29 are specific to this condition. Other listed values are PMMA-HI reference data and may not represent this condition. Bars are the position among polymer grades.
Physical6
PMMA-HI FR has a density of 1.21 g/cm³ (0.0437 lb/in³), heavier than 60% of polymer grades. Its glass-transition temperature is 102°C (216 °F).
Mechanical17
PMMA-HI FR has a yield strength of 43 MPa (6.24 ksi) and a tensile strength of 45 MPa (6.53 ksi) — weaker than 61% of polymer grades. Elongation at break is 15% and the elastic modulus is 2.3 GPa (0.334 Msi).
Thermal11
PMMA-HI FR is rated for continuous service to 66°C (151 °F). It conducts heat at 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 56% of polymer grades. Thermal expansion is 75 µm/m·K (41.7 µin/in·°F).
Electrical7
PMMA-HI FR is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 5×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is good (68/100), worse than 85% of polymer grades. UV resistance is very good.
Sustainability4
Producing a kilogram of PMMA-HI FR takes about 103 MJ of energy and emits 5.6 kg of CO₂ — less than 54% of polymer grades. Typical recycled content is 2%.
Manufacturability8
PMMA-HI FR's machinability is good (60/100, better than 51% of polymer grades); weldability poor (18/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PMMA-HI FR
Is PMMA-HI easy to machine?
Machines cleanly with sharp positive-rake carbide, high speed and low feed; less crazing/chipping than GP acrylic but still use coolant/air blast and avoid dwelling to prevent local softening.
Can PMMA-HI be welded?
No true fusion welding in practice — join by solvent cement (MMA/dichloromethane blends), acrylic structural adhesive, ultrasonic or hot-plate welding; anneal before solvent bonding to avoid stress crazing.
Can PMMA-HI be formed, bent or molded?
Dry 4 h at 80–90 °C before moulding; melt 210–260 °C, mould 50–90 °C, moderate injection speed and generous gates; thermoform sheet at 150–175 °C with shrinkage allowance ~0.4–0.7 %.
What surface finishes work on PMMA-HI?
Flame or diamond polishing restores gloss (haze slightly higher than GP PMMA); can be hard-coated for abrasion/UV, vacuum metallised or pad/screen printed with acrylic-compatible inks; anneal 80 °C to relieve stress before coating.
PMMA-HI chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| methyl methacrylate (MMA) unitsPMMA matrix | 70 – 92 | 82 |
| acrylate comonomer (methyl/ethyl acrylatthermal stability / flow modifier | 1 – 6 | 3 |
| core-shell acrylic elastomer (butyl acryimpact modifier; MBS/butadiene types used in some non-weatherable grades | 8 – 25 | 15 |
| UV absorber / stabiliser / lubricant add | 0.1 – 1.5 | 0.5 |
PMMA-HI FR — frequently asked
What is PMMA-HI FR used for?
PMMA-HI FR is typically used for skylights, aircraft canopies, machine guards and impact-resistant glazing. In short: highest-impact acrylic grade; about 30 % elongation; less crazing when machined.
What is the yield strength of PMMA-HI FR?
PMMA-HI FR has a typical yield strength of 43 MPa (6.24 ksi) and a tensile strength of 45 MPa (6.53 ksi) — weaker than 61% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is PMMA-HI FR easy to machine?
Reasonably — machinability is rated good (60/100, better than 51% of polymer grades). Machines cleanly with sharp positive-rake carbide, high speed and low feed; less crazing/chipping than GP acrylic but still use coolant/air blast and avoid dwelling to prevent local softening.
Can PMMA-HI FR be welded?
Not readily — weldability is rated poor (18/100). No true fusion welding in practice — join by solvent cement (MMA/dichloromethane blends), acrylic structural adhesive, ultrasonic or hot-plate welding; anneal before solvent bonding to avoid stress crazing.
What surface finishes work on PMMA-HI FR?
Flame or diamond polishing restores gloss (haze slightly higher than GP PMMA); can be hard-coated for abrasion/UV, vacuum metallised or pad/screen printed with acrylic-compatible inks; anneal 80 °C to relieve stress before coating.
Can PMMA-HI FR be formed, bent or molded?
Dry 4 h at 80–90 °C before moulding; melt 210–260 °C, mould 50–90 °C, moderate injection speed and generous gates; thermoform sheet at 150–175 °C with shrinkage allowance ~0.4–0.7 %.
What is the maximum service temperature of PMMA-HI FR?
PMMA-HI FR is rated for continuous use to about 66°C (151 °F), and briefly to 90°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ISO 8257-2 Plastics — PMMA moulding and extrusion materials — Preparation of test specimens and determination of properties — ISO (2021)
- ASTM D788 Standard Classification System for Poly(Methyl Methacrylate) Molding and Extrusion Compounds — ASTM (2018)
- Impact-modified acrylic moulding compound datasheets (Plexiglas zk / Altuglas HFI / Sumipex HT / Acrypet IR series) — Röhm, Trinseo/Altuglas, Sumitomo, Mitsubishi Chemical (2023)
- CAMPUS plastics database — PMMA impact-modified grade property sets (ISO 10350-1) — CWFG/CAMPUS (2024)
- ASM Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.