Cast polyurethane elastomer (PU) parts in mid-2026 typically land between US$10/kg for commodity rollers and US$80–250/kg for custom-moulded engineering grades, with the 80A–95A Shore A hardness band covering roughly 70% of industrial orders placed through Guangdong and Henan custom shops [S1][S3].
Three levers dominate every quote: the polyol–isocyanate system (MDI, TDI, HDI, IPDI), the isocyanate index (R value, 0.95–1.05 in production practice), and the part geometry that drives mould cost and demould time [S6]. For reference, polyurethane elastomer fundamentals cover the prepolymer method that most Chinese custom moulders still use.
Raw-Material Cost Stack: Polyol, Isocyanate and Chain Extender
Polycarbonate diol (PCDL) systems trade 25–35% higher polyol cost for better hydrolysis and UV resistance, which is why outdoor mining and offshore orders tend to be quoted on PCDL rather than PTMEG or polyester systems [S6].
Hardness, Modulus and Density: The 80A–95A Sweet Spot
Most stock and custom PU parts ship in 80A–95A Shore A, with 85A as the default when the buyer leaves hardness unspecified — a recipe for rework because a 5-point Shore change typically forces a reformulation and a new mould trial [S1][S3].</h2> <p>Tensile strength on properly cured polyester-TDI systems sits in the 30–50 MPa band, with elongation at break between 400% and 650%; polycarbonate-MDI grades push tensile to 45–60 MPa and improve hot-oil ageing, which is why mine-hoist sheave pads and crossed roller guide buffers often specify them [S4][S6]. Density for unfilled PU runs 1.10–1.25 g/cm³, so a 5 kg roller is roughly 4–4.5 L of cast material — useful for cross-checking weight-driven freight quotes on export shipments [S3].
Processing Cost: Mould, Demould Time and Batch Size
Open-cast PU moulding on aluminium tools at small shops in Dongguan and Luoyang runs 30–60 minutes demould time at 80–110 °C, with mould amortisation alone adding US$0.30–1.20 per part on lots under 500 pieces [S3][S4].
Compression moulding of prepolymer drops cycle time to 8–20 minutes but adds US$8,000–25,000 of steel-tool cost — pay-back typically needs 2,000–5,000 pieces for a 200×200 mm part [S3]. For prototype runs below 200 pieces, 3D-printed sand moulds and silicone tooling are common at a 15–30% unit-cost premium, which is a useful floor when negotiating with smaller Chinese custom shops [S1].
Form, MOQ and Freight: What Changes the Landed Cost
Stock rollers, seals and sheets carry MOQs of 100–500 pieces and ship in carton or plywood-crate packaging, with annual production capacities in the 50,000-piece range typical for mid-tier Chinese manufacturers [S3][S4].
Custom formulations, by contrast, usually carry a 300–1,000 kg MOQ, a US$200–500 small-batch surcharge, and a 25–35 day lead time that can stretch to 50 days during the Q3 shipping peak [S1][S3]. Payment terms in B2B PU export remain anchored on T/T and L/C, with 30% deposit standard and the balance against a copy of the B/L — useful to know when comparing quotes from a manual pallet jack or power trowel supplier that also pushes PU wheels and buffers.
Ageing, Media Compatibility and Service-Life Cost
Polyester-PU loses 15–25% of tensile strength after 100 days in 70 °C water, while polyether-PU in the same test stays within 5–10% — the headline reason hydrolysing environments (food, pharma, mining water) pay the polyether premium [S2].
Glass-transition temperature (Tg) measured by DSC on a typical polyester-TDI elastomer sits between −40 °C and −55 °C, with the soft-segment Tg clearly visible in the heating curve from −100 °C to +80 °C at 2 K/min under nitrogen [S8].
Spec Cut: Polyester vs Polyether vs Polycarbonate PU
Polyester-PU is the cheapest at US$10–25/kg for stock parts, with best mechanical strength and best oil resistance, but worst hydrolysis resistance — pick it for indoor dry service [S1][S2]. Polyether-PU sits at US$15–35/kg and is the workhorse for water-exposed service like pumps, hoses and screen panels [S2]. Polycarbonate-PU at US$30–80/kg delivers the best combination of hydrolysis, UV and dynamic load life, and is the default for mining sheaves, offshore seals and high-cycle crossed roller guide buffers [S3][S6].
For rubber-and-elastomer buyers comparing elastomer families, the NBR vs Silicone spec cut and the EPDM selection guide cover the same decision logic on the rubber side of the aisle; the rule of thumb is PU when abrasion and load-bearing dominate, and rubber when compression set and broad chemical resistance dominate.
Limits, Failure Modes and What to Put on the PO
Three failure modes drive 80% of PU warranty claims: hydrolysis in polyester systems (visible as surface tack and tear-drop cracks within 6–18 months), dynamic heat build-up in thick sections above 95A Shore A, and moulded-in stress from R-value drift above 1.05 that cracks within weeks of demould [S2][S6].
The next signal worth watching is the Q3 2026 MDI/TDI contract round out of Wanhua and Covestro, which historically resets 60–70% of Chinese PU-elastomer raw-material pricing and will pull 2027 stock-part quotes by 3–8%.