SMA UF (Unfilled / Natural)
Grade · default condition
Default choice for rigid, heat-resistant, dimensionally stable molded parts where impact loads are low.
Values for the UF condition
Other SMA grades and fills
SMA is listed in 10 conditions; see the grade overview at SMA.
Compare all 10 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Impact-modified | Choose for automotive instrument-panel substrates and housings needing ABS-like toughness with higher heat resistance. | 36 | 36 | 25 | 105 HRR |
High-MA compatibilizer / coupling resin | Additive grade (flake/pellet/powder) used at 1–10% to compatibilize ABS/PC, PA blends and to couple glass or mineral fillers — not for standalone molding. | 42 | 42 | 1 | 87 Shore D |
Mineral / talc filled SMA | Low-warpage, low-cost stiffening for large flat panels where isotropic shrinkage beats fiber strength. | 45 | 45 | 1.5 | 87 Shore D |
Flame-retardant compound | Use where UL 94 V-0 at 1.5–3 mm is required in heat-exposed electrical housings; slight loss of impact and flow. | 45 | 45 | 2 | 85 Shore D |
Low-MA transparent grade | Pick when optical clarity and easy flow matter more than maximum heat resistance. | 48 | 48 | 3 | 84 Shore D |
UFDefaultThis page Unfilled / Natural | Default choice for rigid, heat-resistant, dimensionally stable molded parts where impact loads are low. | 50 | 50 | 2.5 | 85 Shore D |
Heat-stabilized / high-heat molding grade | Select when HDT above ~130 °C is needed from an unreinforced styrenic, e.g. lighting bezels near lamps. | 52 | 52 | 2 | 86 Shore D |
20% glass-fiber reinforced SMA | Mid-level stiffness/heat upgrade for structural brackets and IP carriers with moderate warpage. | — | 90 | 1.8 | — |
30% glass-fiber reinforced SMA | The workhorse reinforced grade — highest stiffness/HDT combination for load-bearing heat-exposed parts. | — | 110 | 1.5 | — |
40% glass-fiber reinforced SMA | Maximum stiffness / lowest CTE version for rigid metal-replacement structures; very brittle and abrasive to tooling. | — | 125 | 1.3 | — |
What is SMA UF?
SMA UF is SMA in the UF grade — default choice for rigid, heat-resistant, dimensionally stable molded parts where impact loads are low. SMA UF has a yield strength of 50 MPa (7.25 ksi) and a tensile strength of 50 MPa (7.25 ksi) — stronger than 52% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 3.3 GPa (0.479 Msi). SMA UF has a density of 1.08 g/cm³ (0.039 lb/in³), lighter than 67% of polymer grades. Its glass-transition temperature is 140°C (284 °F).
Advantages
- Stiff — 3.3 GPa (0.479 Msi), better than 80% of polymer grades
Limitations
- Limited ductility — 2.5%, worse than 89% of polymer grades
- Needs corrosion protection — 60/100, worse than 89% of polymer grades
- Degrades in UV without stabilisers — 25/100, worse than 76% of polymer grades
- Poor heat conductor — 0.17 W/m·K (0.0982 BTU/hr·ft·°F), worse than 75% of polymer grades
SMA UF properties
Typical room-temperature values for SMA UF; 28 are specific to this condition. Other listed values are SMA reference data and may not represent this condition. Bars are the position among polymer grades.
Physical6
SMA UF has a density of 1.08 g/cm³ (0.039 lb/in³), lighter than 67% of polymer grades. Its glass-transition temperature is 140°C (284 °F).
Mechanical17
SMA UF has a yield strength of 50 MPa (7.25 ksi) and a tensile strength of 50 MPa (7.25 ksi) — stronger than 52% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 3.3 GPa (0.479 Msi).
Thermal11
SMA UF is rated for continuous service to 100°C (212 °F). It conducts heat at 0.17 W/m·K (0.0982 BTU/hr·ft·°F), worse than 75% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical7
SMA UF is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 89% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of SMA UF takes about 95 MJ of energy and emits 3.6 kg of CO₂ — less than 70% of polymer grades. Typical recycled content is 0%.
Manufacturability8
SMA UF's machinability is good (55/100, worse than 64% of polymer grades); weldability good (55/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SMA UF
Is SMA easy to machine?
Machines like SAN/PS — sharp carbide tools, high speed, light feed, air cooling; brittle so avoid sharp internal corners and pre-drill before tapping.
Can SMA be welded?
Ultrasonic, vibration and hot-plate welding work well; solvent bonding with MEK/methylene chloride blends; adhesives should be epoxy or cyanoacrylate, avoid amine-cured systems that react with anhydride.
Can SMA be formed, bent or molded?
Dry 2–4 h at 80–90 °C, mold at 230–270 °C melt / 55–90 °C tool with generous gates; keep residence time short as anhydride can hydrolyse and outgas, causing splay.
What surface finishes work on SMA?
Takes paint and hot stamping readily; can be vacuum metallized after base coat; polishes to a glossy surface but stress-cracks in aggressive solvent-based primers.
SMA 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 |
|---|---|---|
| styrenemonomer, backbone | 68 – 92 | 85 |
| maleic anhydrideMA content sets Tg/HDT and reactivity | 8 – 32 | 15 |
| butadiene/acrylic rubberonly in impact-modified terpolymer grades | 0 – 20 | 0 |
| glass fiberreinforced grades only | 0 – 40 | 0 |
SMA UF — frequently asked
What is SMA UF used for?
SMA UF is typically used for automotive interior trim, appliance housings needing higher HDT, PC/ABS compatibilizer and instrument panel components. In short: highest-HDT styrenic copolymer; PC/ABS compatibilizer resin; glass-reinforced to 40 %.
What is the yield strength of SMA UF?
SMA UF has a typical yield strength of 50 MPa (7.25 ksi) and a tensile strength of 50 MPa (7.25 ksi) — stronger than 52% of polymer grades. Strength varies by condition: see the 10 listed tempers.
Is SMA UF easy to machine?
Reasonably — machinability is rated good (55/100, worse than 64% of polymer grades). Machines like SAN/PS — sharp carbide tools, high speed, light feed, air cooling; brittle so avoid sharp internal corners and pre-drill before tapping.
Can SMA UF be welded?
Yes — weldability is rated good (55/100). Ultrasonic, vibration and hot-plate welding work well; solvent bonding with MEK/methylene chloride blends; adhesives should be epoxy or cyanoacrylate, avoid amine-cured systems that react with anhydride.
What surface finishes work on SMA UF?
Takes paint and hot stamping readily; can be vacuum metallized after base coat; polishes to a glossy surface but stress-cracks in aggressive solvent-based primers.
Can SMA UF be formed, bent or molded?
Dry 2–4 h at 80–90 °C, mold at 230–270 °C melt / 55–90 °C tool with generous gates; keep residence time short as anhydride can hydrolyse and outgas, causing splay.
What is the maximum service temperature of SMA UF?
SMA UF is rated for continuous use to about 100°C (212 °F), and briefly to 130°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SMA UF and SMA IM?
UF is the default condition — default choice for rigid, heat-resistant, dimensionally stable molded parts where impact loads are low. IM: choose for automotive instrument-panel substrates and housings needing ABS-like toughness with higher heat resistance. Yield strength is 50 MPa in UF versus 36 MPa in IM.
Sources
- XIRAN SMA copolymer and compound datasheets — Polyscope Polymers (2023)
- Dylark SMA resin technical data — NOVA Chemicals (2005)
- CAMPUS / UL Prospector styrenic copolymer datasets — CAMPUS Plastics (2024)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
- ISO 527 / ISO 178 / ISO 75 / ISO 306 test methods — ISO (2019)
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.