General Purpose · grade
General Purpose-D75
Properties of the D75 condition, compared with the other General Purpose grades.
Rigid unfilled PU for machinable tooling blocks, jigs, fixtures and cast prototype parts.
What is General Purpose-D75?
General Purpose-D75 is General Purpose in the D75 grade — rigid unfilled PU for machinable tooling blocks, jigs, fixtures and cast prototype parts. General Purpose-D75 has a tensile strength of 55 MPa (7.98 ksi), stronger than 63% of polyurethane grades. Elongation at break is 30% and the elastic modulus is 1.7 GPa (0.247 Msi). General Purpose-D75 has a density of 1.2 g/cm³ (0.0434 lb/in³), heavier than 87% of polyurethane grades. Its glass-transition temperature is -35°C (-31 °F). GP-A80 is the default condition FabDigit quotes; D75 is available on request or by drawing note.
Advantages
- Good UV / weathering resistance — 35/100, better than 85% of polyurethane grades
- High service temperature — 90°C (194 °F), better than 83% of polyurethane grades
- Easy to machine — 75/100, better than 80% of polyurethane grades
Limitations
- High mold shrinkage — 1.2%, worse than 98% of polyurethane grades
- Hard to polish — 30/100, worse than 83% of polyurethane grades
General Purpose-D75 properties
Typical room-temperature values for General Purpose-D75 — 16 properties are specific to this condition; the rest are grade-level values shared by every General Purpose grade. Each bar shows where the value sits among the polyurethane grades in FabDigit's library — further right is higher.
Physical4
General Purpose-D75 has a density of 1.2 g/cm³ (0.0434 lb/in³), heavier than 87% of polyurethane grades. Its glass-transition temperature is -35°C (-31 °F).
Mechanical9
General Purpose-D75 has a tensile strength of 55 MPa (7.98 ksi), stronger than 63% of polyurethane grades. Elongation at break is 30% and the elastic modulus is 1.7 GPa (0.247 Msi).
Thermal8
General Purpose-D75 is rated for continuous service to 90°C (194 °F). It conducts heat at 0.22 W/m·K (0.127 BTU/hr·ft·°F), better than 85% of polyurethane grades. Thermal expansion is 90 µm/m·K (50 µin/in·°F).
Electrical7
General Purpose-D75 is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹⁰ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 83% of polyurethane grades. UV resistance is fair.
Sustainability4
Producing a kilogram of General Purpose-D75 takes about 105 MJ of energy and emits 5 kg of CO₂ — more than 63% of polyurethane grades. Typical recycled content is 3%.
Manufacturability4
General Purpose-D75's machinability is very good (75/100, better than 80% of polyurethane grades).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other General Purpose grades and fills
General Purpose is also supplied in 16 other conditions. The full side-by-side table is on the General Purpose overview.
- GP-A80DefaultDefault all-round grade for rollers, pads, bushings and seals needing high abrasion and tear resistance with useful flexibility.40 MPa tensile
- GF30Structural RIM/cast grade for stiff, dimensionally stable housings and panels replacing sheet metal.80 MPa tensile
- D75Rigid unfilled PU for machinable tooling blocks, jigs, fixtures and cast prototype parts.55 MPa tensile
- A90Pick for heavy-load wheels, mill liners, cyclone parts and stripper plates where abrasion and load dominate over flexibility.48 MPa tensile
- TPU-ESMelt-processable grade for injection-moulded and extruded parts (hose, cable jacket, wheels) needing top abrasion and oil resistance.45 MPa tensile
- TPU-ETUse where parts see hot water, humidity or microbial attack, or must stay flexible below −40 °C.38 MPa tensile
- A70Standard hardness for drive rollers, scrapers and low-noise wheels.35 MPa tensile
- A60Good compromise of cushioning and load capacity for rolls, wipers and shock pads.30 MPa tensile
- A40Choose for soft printing/conveying rolls, vibration pads and gaskets needing high conformability.18 MPa tensile
- FLEX-FOAMFor cushioning, seating, packaging and acoustic absorption where load-bearing is minimal.0.15 MPa tensile
- RIGID-FOAMBest-in-class insulation core for panels, cold-chain and spray-applied insulation; not a load-bearing structural material.8 properties
Working with General Purpose-D75
Is General Purpose easy to machine?
Machines like a tough rubber: use very sharp positive-rake carbide or single-flute tools, high surface speed with low feed pressure, air or water-mist cooling, and support thin walls to avoid deflection and tearing; hard D-scale grades cut almost like a rigid plastic.
Can General Purpose be welded?
Cast (thermoset) PU cannot be welded — join by adhesive bonding with polyurethane/epoxy or cyanoacrylate after abrasion and primer; TPU grades weld well by hot-plate, HF/ultrasonic and hot-air methods.
Can General Purpose be formed, bent or molded?
Open-cast, centrifugal or RIM processing of prepolymer at 70–110 °C mould temperature with post-cure 8–16 h at 100 °C; TPU is injection-moulded or extruded at 185–225 °C melt and must be dried 2–3 h at 80–100 °C to avoid hydrolysis and bubbles.
What surface finishes work on General Purpose?
Not platable or anodizable; parts are usually used as-cast or ground/lathe-finished, and can be painted with 2K polyurethane paints after solvent wipe and light abrasion — adhesion to metal cores requires blasting plus a PU bonding primer.
General Purpose 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 |
|---|---|---|
| MDI (4,4'-diphenylmethane diisocyanate)TDI or aliphatic HDI/H12MDI used in some grades | 20 – 40 | 30 |
| chain extender (1,4-butanediol / MOCA / sets hard-segment content and hardness | 3 – 10 | 6 |
| catalyst, antioxidant, hydrolysis stabil | 0.2 – 2 | 1 |
| glass fiber0–30% in reinforced RIM/rigid variants | ≈ 0 | 0 |
| polyester or polyether polyoladipate polyester, PTMEG or PPG; determines hydrolysis and low-temperature behaviour | ≥ 50 (balance) | — |
General Purpose-D75 — frequently asked
What is General Purpose-D75 used for?
General Purpose-D75 is typically used for housings, enclosures and fixtures. In short: everyday rigid cast PU; ABS-like feel.
What is the tensile strength of General Purpose-D75?
General Purpose-D75 has a typical tensile strength of 55 MPa (7.98 ksi) — stronger than 63% of polyurethane grades. Strength varies by condition: see the 17 listed tempers.
Is General Purpose-D75 easy to machine?
Yes — machinability is rated very good (75/100, better than 80% of polyurethane grades). Machines like a tough rubber: use very sharp positive-rake carbide or single-flute tools, high surface speed with low feed pressure, air or water-mist cooling, and support thin walls to avoid deflection and tearing; hard D-scale grades cut almost like a rigid plastic.
Can General Purpose-D75 be welded?
Cast (thermoset) PU cannot be welded — join by adhesive bonding with polyurethane/epoxy or cyanoacrylate after abrasion and primer; TPU grades weld well by hot-plate, HF/ultrasonic and hot-air methods.
What surface finishes work on General Purpose-D75?
Not platable or anodizable; parts are usually used as-cast or ground/lathe-finished, and can be painted with 2K polyurethane paints after solvent wipe and light abrasion — adhesion to metal cores requires blasting plus a PU bonding primer.
Can General Purpose-D75 be formed, bent or molded?
Open-cast, centrifugal or RIM processing of prepolymer at 70–110 °C mould temperature with post-cure 8–16 h at 100 °C; TPU is injection-moulded or extruded at 185–225 °C melt and must be dried 2–3 h at 80–100 °C to avoid hydrolysis and bubbles.
What is the maximum service temperature of General Purpose-D75?
General Purpose-D75 is rated for continuous use to about 90°C (194 °F), and briefly to 120°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in General Purpose-D75?
Yes — General Purpose-D75 is available for urethane casting with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASM Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
- Polyurethane Handbook (Oertel) — Hanser (1994)
- Desmopan / Texin TPU product datasheets — Covestro (2023)
- Adiprene / Vibrathane cast prepolymer selector guides — LANXESS (Chemtura) (2022)
- Elastollan TPU material properties brochure — BASF (2023)
- CAMPUS plastics database — TPU records — CWFG (2024)
- ASTM D412 / D624 / D395 / D2240 rubber test methods — ASTM (2022)
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.