Unsaturated polyester resins: Overview
From quartz worktops to boats, tanks and pipes
What this tab covers What the chemical is, how big its market is, what it is used for (with shares, volumes, why it wins and what could replace it), and its chain from raw material to end user. Ends with three things to remember.Unsaturated polyester resins (UPR) are made by reacting glycols with maleic and phthalic anhydrides and dissolving the polyester in styrene. A peroxide catalyst then crosslinks the styrene and polyester into a hard solid, usually reinforced with glass fibre. UPR is the cheapest composite resin, used in pipes and tanks, building panels, boats, car parts, wind blade components and quartz stone. China made about 3.45 Mt in 2024 (Chyxx), roughly half the world total of about 6.5-7 Mt (indicative). For India it matters as a building and water-infrastructure material made from mostly imported styrene and glycols.
Volume about 6.5-7 Mt a year (2024-2025, indicative, basis: China demand of 3.31 Mt in 2024 at roughly half of world volume); China output 3.45 Mt (2024e) Market value $14.6 billion (2025, IMARC); $11.95 billion (2026, Mordor Intelligence) Growth 4.4-4.7% a year (IMARC to 2034; Mordor to 2031); China output up 7.27% in 2023 IMARC Group 2025; Mordor Intelligence via GII 2026; Chyxx (China output and demand, 2025); world volume indicativeKey uses
| Use | Share | Annual volume | Why this commodity | Alternatives |
|---|---|---|---|---|
| Pipes, tanks and FRP grating (water, sewage, chemicals) | 20% | about 1.4 Mtbasis | Glass-reinforced UPR pipes and tanks do not corrode, are light to install and cost less than stainless steel or lined steel. Isophthalic and vinyl ester grades are used for corrosive service. indicative share | HDPE and PVC pipe ductile iron and concrete vinyl ester and epoxy composites |
| Artificial and engineered stone (quartz surfaces, cultured marble) | 20% | about 1.4 Mtbasis | UPR binds about 90% quartz or marble filler into slabs for kitchen tops and sanitaryware. In China this is a key outlet, and US tariffs on quartz stone in 2018-2019 cut Chinese UPR output (Chyxx). indicative share; Chyxx 2025 | natural stone acrylic solid surface ceramics |
| Construction panels, roofing sheets, sanitaryware and doors | 18% | about 1.2 Mtbasis | Translucent roofing, cladding, cooling towers, bathtubs and doors use UPR for low cost and easy moulding. indicative share | PVC and polycarbonate sheet steel acrylic |
| Transport (SMC and BMC car and truck parts, rail interiors) | 12% | about 0.8 Mtbasis | Sheet and bulk moulding compounds make light, paintable body panels and battery covers. Carmakers processed about 1.8 Mt of composite resins in 2025, about 40% as SMC (Mordor). indicative share; Mordor via GII 2026 | steel and aluminium thermoplastic composites polypropylene compounds |
| Electrical (SMC/BMC enclosures, meter boxes, insulators) | 8% | about 0.5 Mtbasis | Mineral-filled UPR compounds are flame-retardant, insulating and dimensionally stable. indicative share | phenolics thermoplastics (PC, PBT) epoxy |
| Marine (boat hulls and decks) | 8% | about 0.5 Mtbasis | Hand lay-up and infusion of UPR and gelcoats is the standard way to build small boats. indicative share | aluminium vinyl ester and epoxy (performance boats) |
| Wind blade parts, gelcoats, putties, coatings and other | 14% | about 1.0 Mtbasis | UPR is one of three main blade resins with epoxy and vinyl ester (Chyxx), used mainly in nacelle covers and some blades; car-body putties and gelcoats are steady outlets. Wind blade composite demand rose 22% in 2025 (Mordor). indicative share; Chyxx 2025; Mordor via GII | epoxy vinyl ester polyurethane |
From raw material to user
- Feedstocks Phthalic anhydride from o-xylene, maleic anhydride from n-butane or benzene, propylene glycol from PO, diethylene glycol from MEG units, styrene from benzene and ethylene.
- Polyesterification Glycols and anhydrides are heated to about 190-210 C in batch reactors for 10-20 hours, removing about 0.06-0.07 t water per t resin (indicative).
- Thinning in styrene The polyester is dissolved in about 30-40% styrene with inhibitors; this is the saleable resin.
- Compounding Resin is mixed with glass fibre, fillers (calcium carbonate, quartz) and additives as SMC, BMC or for spray-up and infusion.
- Curing Peroxide (often MEKP) and a cobalt accelerator start styrene crosslinking at room or elevated temperature.
Made from (commodity table)
Oil Crude oilThree things to know
- China produced 3.23 Mt of UPR in 2023 and about 3.45 Mt in 2024, against demand of about 3.31 Mt (Chyxx).
- Orthophthalic resins were 53% of 2025 market revenue and maleic anhydride 51% of raw-material spend (Mordor via GII).
- UPR is about one-third styrene, so styrene prices (Asia $1,030/t on 2 March 2026, styrene tile) drive resin cost.