Syntactic Foam Core
Syntactic Foam Core is a thermoset resin matrix filled with hollow glass or ceramic microspheres, supplied in density grades SF-32 to SF-70 plus macrosphere, high-temperature, structural-core and tooling-block variants.
Reference datasheet — Syntactic Foam Core is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SF-45 condition
Syntactic Foam Core grades and fills
Syntactic Foam Core is supplied in 9 conditions, soft to hard. SF-45 is the default FabDigit quotes; the values on this page are for it.
Compare all 9 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
0.32 g/cm³ shallow-water buoyancy grade | Maximum buoyancy per volume for shallow ROV/riser modules and floats to ~1500 m. | 9 | |||
0.38 g/cm³ mid-water grade | Balanced buoyancy/strength for work-class ROV and mooring floats to ~2500 m. | 12 | |||
SF-45Default 0.45 g/cm³ deep-water buoyancy / general core grade | Default all-round grade: good buoyancy with 3000–4000 m crush rating, also used as machinable sandwich core. | 15 | |||
0.56 g/cm³ full-ocean-depth class | Thick-wall microsphere grade for 6000 m AUV/HOV and subsea equipment buoyancy. | 20 | |||
0.70 g/cm³ hadal / 11 000 m grade | Highest-strength buoyancy grade (often ceramic/thick-wall spheres) for hadal landers and full-ocean-depth submersibles. | 26 | |||
Structural sandwich core / edge close-out & insert potting syntactic | Higher-density paste or sheet syntactic used as honeycomb edge close-out, insert potting and high-bearing core in composite panels. | 28 | |||
Macrosphere/composite buoyancy block | Lowest density and lowest cost per litre of buoyancy for large shallow/mid-water modules where crush rating is moderate. | ||||
High-temperature matrix grade | Choose for downhole tools, subsea insulation and hot-wet service where the standard epoxy grade would soften. | ||||
Syntactic tooling / modelling board grade | Dimensionally stable, low-CTE machinable board for composite layup tools, master models and check fixtures. |
What is Syntactic Foam Core?
Syntactic Foam Core is a thermoset resin matrix filled with hollow glass or ceramic microspheres, supplied in density grades SF-32 to SF-70 plus macrosphere, high-temperature, structural-core and tooling-block variants. The default grade has 0.45 g/cm³ density, 15 MPa tensile strength, 2.4 GPa modulus, 0.12 W/m·K conductivity and 80 °C maximum service temperature; it is chosen for very low water absorption and high hydrostatic compressive strength in deep-sea buoyancy and sandwich cores. The microspheres are abrasive (machinability 55), so tool wear and dust control are constraints; PVC or PMI foam is cheaper where hydrostatic pressure is low. Syntactic Foam Core has a density of 0.45 g/cm³ (0.0163 lb/in³), lighter than 83% of composite grades. Its glass-transition temperature is 100°C (212 °F). Syntactic Foam Core has a tensile strength of 15 MPa (2.18 ksi), weaker than 83% of composite grades. Elongation at break is 1% and the elastic modulus is 2.4 GPa (0.348 Msi).
What is Syntactic Foam Core used for?
- subsea buoyancy modules
- ROV/AUV structural cores
- deep-sea sandwich panels
Advantages
- Low moisture uptake — 0.1%, better than 85% of composite grades
- Lightweight — 0.45 g/cm³ (0.0163 lb/in³), better than 83% of composite grades
- Low, predictable mold shrinkage — 0.3%, better than 75% of composite grades
Limitations
- Low fracture toughness — 0.6 MPa·√m (0.546 ksi·√in), worse than 98% of composite grades
- Limited service temperature — 80°C (176 °F), worse than 94% of composite grades
- Low stiffness — 2.4 GPa (0.348 Msi), worse than 83% of composite grades
- Poor heat conductor — 0.12 W/m·K (0.0693 BTU/hr·ft·°F), worse than 81% of composite grades
- Limited ductility — 1%, worse than 80% of composite grades
Syntactic Foam Core properties
Typical room-temperature values for Syntactic Foam Core-SF-45; bars are the position among composite grades.
Physical4
Syntactic Foam Core has a density of 0.45 g/cm³ (0.0163 lb/in³), lighter than 83% of composite grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical14
Syntactic Foam Core has a tensile strength of 15 MPa (2.18 ksi), weaker than 83% of composite grades. Elongation at break is 1% and the elastic modulus is 2.4 GPa (0.348 Msi).
Thermal10
Syntactic Foam Core is rated for continuous service to 80°C (176 °F). It conducts heat at 0.12 W/m·K (0.0693 BTU/hr·ft·°F), worse than 81% of composite grades. Thermal expansion is 40 µm/m·K (22.2 µin/in·°F).
Electrical5
Syntactic Foam Core is an electrical insulator with a dielectric strength of 12 kV/mm (304.8 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 77% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of Syntactic Foam Core takes about 95 MJ of energy and emits 5.5 kg of CO₂ — less than 72% of composite grades. Typical recycled content is 0%.
Manufacturability4
Syntactic Foam Core's machinability is good (55/100, better than 71% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the composite family
Yield strength against density for every composite grade FabDigit runs. Syntactic Foam Core is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Syntactic Foam Core
Is Syntactic Foam Core easy to machine?
Machines like a soft plastic but the glass spheres are highly abrasive — use sharp carbide or PCD tools, high speed/low feed, no coolant (avoid water pickup) and full dust extraction; seal machined faces with epoxy or gelcoat.
Can Syntactic Foam Core be welded?
Not weldable; join by epoxy bonding, bolting through potted inserts or overmolding with a polyurethane/GRP skin.
Can Syntactic Foam Core be formed, bent or molded?
Produced by casting/compression-moulding a microsphere–resin slurry into blocks or near-net moulds and oven post-curing; vacuum de-airing and controlled exotherm are essential to avoid voids and sphere crushing.
Syntactic Foam Core 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 |
|---|---|---|
| hollow glass microspheres (soda-lime bor50–65 vol %; wall thickness/crush rating sets the density grade | 35 – 55 | 45 |
| hollow ceramic or thick-wall glass microused in 6000–11000 m grades | 0 – 20 | 0 |
| hollow macrospheres (GRP/epoxy shells)composite/macrosphere buoyancy variants only | 0 – 40 | 0 |
| additives (toughener, pigment, FR, silan | 0 – 5 | 2 |
| epoxy resin (DGEBA) + amine/anhydride hamatrix; phenolic, BMI or polyester used in special grades | ≥ 40 (balance) |
What surface finishes work on Syntactic Foam Core?
Typically coated with polyurethane elastomer, GRP skin or marine epoxy paint for impact, abrasion and UV protection; machined surfaces should always be sealed before immersion.
Equivalent designations
Standards and trade names that resolve to Syntactic Foam Core in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- Syntactic Foam
How much does Syntactic Foam Core cost?
Syntactic Foam Core is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Syntactic Foam Core — frequently asked
What is Syntactic Foam Core used for?
Syntactic Foam Core is typically used for subsea buoyancy modules, ROV/AUV structural cores and deep-sea sandwich panels. In short: highest hydrostatic-pressure core; near-zero water absorption; abrasive to cutting tools.
What is the tensile strength of Syntactic Foam Core?
Syntactic Foam Core has a typical tensile strength of 15 MPa (2.18 ksi) — weaker than 83% of composite grades. Strength varies by condition: see the 9 listed tempers.
Is Syntactic Foam Core easy to machine?
Reasonably — machinability is rated good (55/100, better than 71% of composite grades). Machines like a soft plastic but the glass spheres are highly abrasive — use sharp carbide or PCD tools, high speed/low feed, no coolant (avoid water pickup) and full dust extraction; seal machined faces with epoxy or gelcoat.
Can Syntactic Foam Core be welded?
Not weldable; join by epoxy bonding, bolting through potted inserts or overmolding with a polyurethane/GRP skin.
What surface finishes work on Syntactic Foam Core?
Typically coated with polyurethane elastomer, GRP skin or marine epoxy paint for impact, abrasion and UV protection; machined surfaces should always be sealed before immersion.
Can Syntactic Foam Core be formed, bent or molded?
Produced by casting/compression-moulding a microsphere–resin slurry into blocks or near-net moulds and oven post-curing; vacuum de-airing and controlled exotherm are essential to avoid voids and sphere crushing.
What is the maximum service temperature of Syntactic Foam Core?
Syntactic Foam Core is rated for continuous use to about 80°C (176 °F), and briefly to 110°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Syntactic Foam Core cost?
Syntactic Foam Core is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- Deep-sea buoyancy syntactic foam grade datasheets (density vs depth rating) — Trelleborg Offshore / Engineered Syntactic Systems / Cuming (2023)
- ASM Handbook Vol. 21 — Composites (syntactic foams) — ASM International (2001)
- ASTM D1622 / D695 / D790 / D2842 — density, compressive, flexural and water absorption of cellular plastics — ASTM (2020)
- Syntactic foam mechanical property reviews (microballoon volume fraction vs modulus/strength) — peer-reviewed composites literature (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.