SMC LP-A
Grade
GB GB/T 25054
LP-A = low-profile Class A surface SMC
Choose when the molded part must be primed and painted to a Class A automotive finish with near-zero shrinkage.
Values for the LP-A condition
Other SMC grades and fills
SMC is listed in 6 conditions; see the grade overview at SMC.
Compare all 6 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Low-density SMC with hollow glass microspheres | Use where mass reduction of 25–35 % versus standard SMC matters more than peak stiffness (vehicle closures, truck panels). | — | 55 | 1.3 | 87 Shore D |
LP-AThis page Low-profile Class A surface SMC | Choose when the molded part must be primed and painted to a Class A automotive finish with near-zero shrinkage. | — | 65 | 1.2 | 90 Shore D |
Flame-retardant / electrical grade SMC | Pick for switchgear, busbar supports, meter boxes and insulating parts needing V-0, high CTI and glow-wire performance. | — | 65 | 1.2 | 90 Shore D |
Vinyl-ester matrix SMC | Choose for chemical plant covers, flue components and hot-water contact where standard polyester SMC hydrolyzes. | — | 85 | 1.7 | 90 Shore D |
HS/HMC | Select for load-bearing brackets, bumper beams and structural reinforcements where SMC must approach laminate stiffness. | — | 180 | 1.8 | 92 Shore D |
CF-SMC | Use where the highest specific stiffness in a compression-moldable thermoset is required (motorsport, aerospace brackets). | — | 250 | 1 | 92 Shore D |
What is SMC LP-A?
SMC LP-A is SMC in the LP-A grade — choose when the molded part must be primed and painted to a Class A automotive finish with near-zero shrinkage. SMC LP-A has a tensile strength of 65 MPa (9.43 ksi), stronger than 73% of polymer grades. Elongation at break is 1.2% and the elastic modulus is 11.5 GPa (1.67 Msi). SMC LP-A has a density of 1.9 g/cm³ (0.0686 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is 115°C (239 °F).
Advantages
- Low, predictable mold shrinkage — 0.02%, better than 100% of polymer grades
- Stiff — 11.5 GPa (1.67 Msi), better than 98% of polymer grades
- Low embodied carbon — 3.2 kg CO₂/kg, better than 81% of polymer grades
- Conducts heat well — 0.28 W/m·K (0.162 BTU/hr·ft·°F), better than 79% of polymer grades
- Good UV / weathering resistance — 55/100, better than 77% of polymer grades
Limitations
- Limited ductility — 1.2%, worse than 98% of polymer grades
- Heavy — 1.9 g/cm³ (0.0686 lb/in³), worse than 97% of polymer grades
- Limited formability — 5/100, worse than 95% of polymer grades
- Difficult to weld — 5/100, worse than 89% of polymer grades
- Difficult to machine — 30/100, worse than 87% of polymer grades
SMC LP-A properties
Typical room-temperature values for SMC LP-A; 25 are specific to this condition. Other listed values are SMC reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
SMC LP-A has a density of 1.9 g/cm³ (0.0686 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is 115°C (239 °F).
Mechanical12
SMC LP-A has a tensile strength of 65 MPa (9.43 ksi), stronger than 73% of polymer grades. Elongation at break is 1.2% and the elastic modulus is 11.5 GPa (1.67 Msi).
Thermal10
SMC LP-A is rated for continuous service to 130°C (266 °F). It conducts heat at 0.28 W/m·K (0.162 BTU/hr·ft·°F), better than 79% of polymer grades. Thermal expansion is 22 µm/m·K (12.2 µin/in·°F).
Electrical7
SMC LP-A is an electrical insulator with a dielectric strength of 15 kV/mm (381 V/mil) and a resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is good.
Sustainability4
Producing a kilogram of SMC LP-A takes about 60 MJ of energy and emits 3.2 kg of CO₂ — less than 96% of polymer grades. Typical recycled content is 0%.
Manufacturability6
SMC LP-A's machinability is poor (30/100, worse than 87% of polymer grades); weldability not recommended (5/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SMC LP-A
Is SMC easy to machine?
Highly abrasive — drill and trim with PCD or diamond-coated tooling at high speed/low feed, back the part to avoid edge chipping, and extract glass dust.
Can SMC be welded?
Thermoset — cannot be welded; join by structural adhesive (urethane/epoxy), molded-in inserts, bolts or rivets.
Can SMC be formed, bent or molded?
Compression mold matched-metal at 140–160 °C, 5–15 MPa, ~30–45 s/mm wall; charge 40–70 % of cavity area and keep flow paths short to control fiber orientation and knit lines.
What surface finishes work on SMC?
In-mold coating or primer-surfacer plus 2K polyurethane paint for Class A; deflash edges, degrease and lightly abrade before bonding or painting; no plating without special conductive pretreatment.
SMC 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 |
|---|---|---|
| unsaturated polyester resin (styrene-croorthophthalic/isophthalic UP; vinyl ester in VE grade | 20 – 32 | 26 |
| glass fiber (chopped, 12–50 mm)45–65 % in HS/HMC grades | 20 – 35 | 28 |
| low-profile additive (thermoplastic, PS/controls cure shrinkage / Class A surface | 2 – 6 | 4 |
| zinc stearate / internal mold release | 2 – 5 | 3.5 |
| MgO or Mg(OH)2 thickenerB-stage maturation | 0.5 – 1.5 | 1 |
| peroxide initiator (TBPB/TBPO) | 0.5 – 1.5 | 1 |
| pigment / additives | 0.5 – 3 | 1.5 |
| calcium carbonate fillerreplaced wholly/partly by ATH in FR grades | ≥ 30 (balance) | — |
SMC LP-A — frequently asked
What is SMC LP-A used for?
SMC LP-A is typically used for electrical switchgear housings, automotive body panels, bathroom fixtures and junction boxes. In short: low-cost structural thermoset; good high-voltage insulation; not weldable or recyclable.
What is the tensile strength of SMC LP-A?
SMC LP-A has a typical tensile strength of 65 MPa (9.43 ksi) — stronger than 73% of polymer grades. Strength varies by condition: see the 6 listed tempers.
Is SMC LP-A easy to machine?
Not especially — machinability is rated poor (30/100, worse than 87% of polymer grades). Highly abrasive — drill and trim with PCD or diamond-coated tooling at high speed/low feed, back the part to avoid edge chipping, and extract glass dust.
Can SMC LP-A be welded?
Not readily — weldability is rated not recommended (5/100). Thermoset — cannot be welded; join by structural adhesive (urethane/epoxy), molded-in inserts, bolts or rivets.
What surface finishes work on SMC LP-A?
In-mold coating or primer-surfacer plus 2K polyurethane paint for Class A; deflash edges, degrease and lightly abrade before bonding or painting; no plating without special conductive pretreatment.
Can SMC LP-A be formed, bent or molded?
Compression mold matched-metal at 140–160 °C, 5–15 MPa, ~30–45 s/mm wall; charge 40–70 % of cavity area and keep flow paths short to control fiber orientation and knit lines.
What is the maximum service temperature of SMC LP-A?
SMC LP-A is rated for continuous use to about 130°C (266 °F), and briefly to 180°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- GB/T 15568 (SMC) — SAC (2008)
- ISO 527-4 / ISO 14125 — tensile and flexural properties of fiber-reinforced plastic composites — ISO (1998)
- Engineered Materials Handbook Vol. 2: Composites — ASM International (1987)
- SMC compound technical datasheets (Menzolit, Polynt Composites, IDI Composites, Continental Structural Plastics) — various (2023)
- UL Yellow Card / IEC 60112 CTI and UL 94 listings for polyester molding compounds — UL Solutions (2023)
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.