Syntactic Foam Core HT
Heat-treated state
HT = high-temperature matrix grade
Choose for downhole tools, subsea insulation and hot-wet service where the standard epoxy grade would soften.
Values for the HT condition
Other Syntactic Foam Core grades and fills
Syntactic Foam Core is listed in 9 conditions; see the grade overview at Syntactic Foam Core.
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. | — | — | — | — |
HTThis page 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 HT?
Syntactic Foam Core HT is Syntactic Foam Core heat treated to HT — choose for downhole tools, subsea insulation and hot-wet service where the standard epoxy grade would soften. Syntactic Foam Core HT 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 3 GPa (0.435 Msi). Syntactic Foam Core HT has a density of 0.55 g/cm³ (0.0199 lb/in³), lighter than 82% of composite grades. Its glass-transition temperature is 220°C (428 °F). SF-45 is the default condition FabDigit quotes; HT is available on request or by drawing note.
Advantages
- Low moisture uptake — 0.1%, better than 85% of composite grades
- Lightweight — 0.55 g/cm³ (0.0199 lb/in³), better than 82% 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
- Low stiffness — 3 GPa (0.435 Msi), worse than 81% of composite grades
- Limited ductility — 1%, worse than 80% of composite grades
- Poor heat conductor — 0.15 W/m·K (0.0867 BTU/hr·ft·°F), worse than 79% of composite grades
- Hard to polish — 25/100, worse than 76% of composite grades
Syntactic Foam Core HT properties
Typical room-temperature values for Syntactic Foam Core HT; 13 are specific to this condition. Other listed values are Syntactic Foam Core reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
Syntactic Foam Core HT has a density of 0.55 g/cm³ (0.0199 lb/in³), lighter than 82% of composite grades. Its glass-transition temperature is 220°C (428 °F).
Mechanical14
Syntactic Foam Core HT 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 3 GPa (0.435 Msi).
Thermal10
Syntactic Foam Core HT is rated for continuous service to 200°C (392 °F). It conducts heat at 0.15 W/m·K (0.0867 BTU/hr·ft·°F), worse than 79% of composite grades. Thermal expansion is 40 µm/m·K (22.2 µin/in·°F).
Electrical5
Syntactic Foam Core HT 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 HT 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 HT's machinability is fair (45/100, better than 63% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Syntactic Foam Core HT
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.
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.
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) | — |
Syntactic Foam Core HT — frequently asked
What is Syntactic Foam Core HT used for?
Syntactic Foam Core HT 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 HT?
Syntactic Foam Core HT 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 HT easy to machine?
Reasonably — machinability is rated fair (45/100, better than 63% 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 HT 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 HT?
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 HT 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 HT?
Syntactic Foam Core HT is rated for continuous use to about 200°C (392 °F), and briefly to 260°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.