DAIP MDI
Reinforced grade
ASTM D5948 Type SDI, D5948 Type GDI-30 · also MIL-M-14 Type GDI
MDI = mineral/silica filled DAIP compound
Choose the mineral/silica-filled compound for low-cost encapsulation and switch insulation needing low CTE and arc resistance; impact strength is the lowest of the family.
Values for the MDI condition
Other DAIP grades and fills
DAIP is listed in 5 conditions; see the grade overview at DAIP.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Short synthetic-fiber / low-filler DAIP, fine-detail molding | Select the low-filler, short synthetic-fiber grade for thin-wall fine-detail insulators and multi-cavity precision transfer molding, where flow matters more than the 38 MPa strength. | — | 38 | 1.4 | 100 HRM |
MDIThis page Mineral/silica filled DAIP compound | Choose the mineral/silica-filled compound for low-cost encapsulation and switch insulation needing low CTE and arc resistance; impact strength is the lowest of the family. | — | 38 | 0.4 | 112 HRM |
Synthetic (acrylic/polyester) fiber filled DAIP | Use the synthetic-fiber filled grade for thin-wall insulators and high-frequency or high-voltage tracking duty: 1.58 g/cm³ density, low dielectric loss and good precision machining at 42 MPa. | — | 42 | 0.9 | — |
Flame-retardant 30% glass-filled DAIP | Choose the flame-retardant 30% glass-filled version when thin-wall V-0, low smoke or strict fire certification governs; strength drops to 50 MPa and service temperature to 200 °C. | — | 50 | 0.5 | 105 HRM |
GDI-30Default 30% glass-fiber reinforced DAIP molding compound | Pick the 30% glass-fiber molding compound for military and aerospace connector insulators: highest stiffness, heat-deflection and 205 °C service for pin-loaded structures, at the cost of machinability. | — | 55 | 0.6 | — |
What is DAIP MDI?
DAIP MDI is DAIP in the MDI grade — choose the mineral/silica-filled compound for low-cost encapsulation and switch insulation needing low CTE and arc resistance; impact strength is the lowest of the family. DAIP MDI has a tensile strength of 38 MPa (5.51 ksi), weaker than 56% of polymer grades. Elongation at break is 0.4% and the elastic modulus is 10 GPa (1.45 Msi). DAIP MDI has a density of 1.92 g/cm³ (0.0694 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is 190°C (374 °F). GDI-30 is the default condition FabDigit quotes; MDI is available on request or by drawing note.
Advantages
- Conducts heat well — 0.55 W/m·K (0.318 BTU/hr·ft·°F), better than 99% of polymer grades
- Stiff — 10 GPa (1.45 Msi), better than 95% of polymer grades
- Low, predictable mold shrinkage — 0.3%, better than 90% of polymer grades
- High service temperature — 200°C (392 °F), better than 87% of polymer grades
- Good UV / weathering resistance — 70/100, better than 83% of polymer grades
Limitations
- Limited ductility — 0.4%, worse than 100% of polymer grades
- Limited formability — 2/100, worse than 99% of polymer grades
- Heavy — 1.92 g/cm³ (0.0694 lb/in³), worse than 97% of polymer grades
- Difficult to weld — 3/100, worse than 95% of polymer grades
- Difficult to machine — 30/100, worse than 87% of polymer grades
DAIP MDI properties
Typical room-temperature values for DAIP MDI; 23 are specific to this condition. Other listed values are DAIP reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
DAIP MDI has a density of 1.92 g/cm³ (0.0694 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is 190°C (374 °F).
Mechanical9
DAIP MDI has a tensile strength of 38 MPa (5.51 ksi), weaker than 56% of polymer grades. Elongation at break is 0.4% and the elastic modulus is 10 GPa (1.45 Msi).
Thermal10
DAIP MDI is rated for continuous service to 200°C (392 °F). It conducts heat at 0.55 W/m·K (0.318 BTU/hr·ft·°F), better than 99% of polymer grades. Thermal expansion is 22 µm/m·K (12.2 µin/in·°F).
Electrical7
DAIP MDI is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of polymer grades. UV resistance is very good.
Sustainability4
Producing a kilogram of DAIP MDI takes about 105 MJ of energy and emits 5.5 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 0%.
Manufacturability7
DAIP MDI's machinability is poor (30/100, worse than 87% of polymer grades); weldability not recommended (3/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with DAIP MDI
Is DAIP easy to machine?
Cured parts can be turned, milled and drilled, but they are brittle and abrasive: use diamond or carbide tooling at high speed and low feed, and place a backing plate on the exit side to prevent chipping. Extract glass dust at source.
Can DAIP be welded?
Thermoset — no melt welding is possible. Use epoxy or cyanoacrylate bonding, or mechanical fastening.
Can DAIP be formed, bent or molded?
Mainly compression and transfer moulding, with thermoset screw injection also possible: material temperature 85–120 °C, mould temperature 150–180 °C, cure 45–180 s. Thick-walled parts need tool venting and a post-cure at 150–200 °C for several hours to stabilise dimensions and electrical properties.
What surface finishes work on DAIP?
Deflash with cryogenic dry ice or media blasting. The surface can be painted or selectively metallised; plasma or chemical roughening is required before plating deep holes. Mirror polishing is neither needed nor practical.
DAIP 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 |
|---|---|---|
| diallyl isophthalate prepolymer + monomediallyl isophthalate prepolymer/monomer matrix | 25 – 45 | 35 |
| glass fiberchopped glass fiber (GDI-30) | 25 – 35 | 30 |
| organic peroxide initiator (e.g. dicumylcure initiator | 0.3 – 2 | 1 |
| mold release / lubricant (metal stearate | 0.3 – 1.5 | 0.8 |
| pigment / colorantblue/black identification colors common in military parts | 0 – 2 | 1 |
| mineral filler (silica / clay / CaCO3)balance of filler; sets CTE and electrical properties | ≥ 20 (balance) | — |
DAIP MDI — frequently asked
What is DAIP MDI used for?
DAIP MDI is typically used for mil-spec connectors, high-reliability electrical housings and aerospace terminal blocks. In short: 205 °C allyl thermoset; mil-spec connector material; higher-temperature DAP alternative.
What is the tensile strength of DAIP MDI?
DAIP MDI has a typical tensile strength of 38 MPa (5.51 ksi) — weaker than 56% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is DAIP MDI easy to machine?
Not especially — machinability is rated poor (30/100, worse than 87% of polymer grades). Cured parts can be turned, milled and drilled, but they are brittle and abrasive: use diamond or carbide tooling at high speed and low feed, and place a backing plate on the exit side to prevent chipping. Extract glass dust at source.
Can DAIP MDI be welded?
Not readily — weldability is rated not recommended (3/100). Thermoset — no melt welding is possible. Use epoxy or cyanoacrylate bonding, or mechanical fastening.
What surface finishes work on DAIP MDI?
Deflash with cryogenic dry ice or media blasting. The surface can be painted or selectively metallised; plasma or chemical roughening is required before plating deep holes. Mirror polishing is neither needed nor practical.
Can DAIP MDI be formed, bent or molded?
Mainly compression and transfer moulding, with thermoset screw injection also possible: material temperature 85–120 °C, mould temperature 150–180 °C, cure 45–180 s. Thick-walled parts need tool venting and a post-cure at 150–200 °C for several hours to stabilise dimensions and electrical properties.
What is the maximum service temperature of DAIP MDI?
DAIP MDI 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
- ASTM D5948 — Standard Specification for Molding Compounds, Thermosetting — ASTM International (2019)
- MIL-M-14H — Molding Plastics and Molded Plastic Parts, Thermosetting — US DoD (1989)
- ASTM D638 / D790 / D256 / D648 / D150 / D257 / D570 test methods — ASTM International (2022)
- Engineered Materials Handbook Vol.2 — Engineering Plastics (allyl resins) — ASM International (1988)
- DAISO ISODAP / DAP resin technical data — Osaka Soda (2022)
- Diallyl phthalate & diallyl isophthalate molding compound datasheets — Cosmic Plastics / Glenro / DAP (2023)
- DAP/DAIP (2025)
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.