1. Epoxy vs vinyl ester: which resin wins for which job
Both resins start from bisphenol-A epoxy, which is why they are often confused. Vinyl ester is made by reacting an epoxy resin with methacrylic or acrylic acid and dissolving the product in 35 to 45% styrene, so it cures through the same peroxide-initiated free-radical reaction as polyester [media] [S34]. Epoxy stays an epoxy: it is cured by a hardener mixed at a fixed ratio, with no styrene at all. ALTA, the current producer of Derakane, describes epoxy vinyl esters as combining the toughness of epoxy with the easier processing and lower-temperature cure of polyester, and positions them for corrosion-resistant tanks, pipes and pultruded profiles [company] [S4].
In practice the split is clean. Choose vinyl ester when the laminate is wetted by acids, bleach, caustic or hot water, when it is built by hand lay-up, spray-up or filament winding in a fabricator's shop without ovens, and when styrene handling is already under control. Choose epoxy when the part is fatigue-loaded, bonded, carbon-reinforced or vacuum-infused into a large structure, and when you can control mix ratio and cure temperature. Isophthalic polyester remains the cheaper baseline for mild exposure, but on the same pultruded profile Strongwell rates its isophthalic grade not resistant to 0–37% hydrochloric acid and 5% caustic, where its vinyl ester grade is resistant up to 160 °F and 150 °F [company] [S8].
Table 1 compares named grades rather than resin families. The numbers are typical datasheet values for neat castings, not design allowables, and they come from different test laboratories. Read them as an order of magnitude: vinyl ester sits between polyester and epoxy on elongation, and the epoxy row varies more with the hardener than any polyester-to-vinyl-ester difference.
| Property | Isophthalic polyester (Interplastic COR75-AQ-470) | Bisphenol-A vinyl ester (Derakane Signia 411) | Epoxy (Westlake EPON 828 and EPIKOTE RIMR 135/RIMH 137) |
|---|---|---|---|
| Liquid viscosity at 25 °C | 375–475 cP | 370 mPa·s | EPON 828 neat resin 110–150 P (11,000–15,000 mPa·s); RIMR 135 resin 700–1,100 mPa·s, hardener 10–50 mPa·s |
| Styrene content | 45% maximum | 44% | none; infusion system has no unreactive components |
| Tensile strength | 60 MPa (ASTM D638) | 86 MPa (ISO 527) | 60–75 MPa (RIMR 135/137); above 69 MPa for unfilled EPON 828 systems |
| Tensile modulus | 3,655 MPa | 3,100 MPa | 2.7–3.2 GPa (RIMR 135/137); above 2,750 MPa (EPON 828) |
| Elongation at break | 1.9% | 5–6% | 8–16% (RIMR 135/137) |
| Heat deflection temperature | 117 °C (ASTM D648) | 105 °C (ISO 75, 1.8 MPa) | 31–180 °C for EPON 828 depending on hardener; RIMR 135 rated to 80 °C service after heat treatment |
| Volume shrinkage | not stated | 8% | described as low; no figure published |
| Cure system | MEKP, cobalt | MEKP-925H 1.0–2.0 phr plus cobalt 0.10–0.40 phr; or BPO plus DEA | hardener at 100:30 ± 2 by weight (RIMR 135/137); off-ratio cannot be corrected |
| Typical post-cure | per fabricator | laminate data after post-cure; casting data after 24 h RT + 2 h at 120 °C (Momentum 411-350) | 24 h at 23 °C + 15 h at 60–80 °C (RIMR 135/137) |
Source: Interplastic TDS rev. 3/20 [S5]; ALTA Derakane Signia 411 TDS, May 2025 [S1]; Ashland Derakane Momentum 411-350 TDS [S2]; Westlake EPON 828 TDS rev. 2021 [S6]; Hexion RIMR 135 TDS rev. 2015 [S7]. Typical values, not specifications.
2. Why vinyl ester resists hydrolysis better than polyester
Water, acids and caustic attack composites mainly by hydrolyzing ester links in the matrix. An unsaturated polyester chain is built by esterifying acids with glycols, so every repeat unit carries ester links and its reactive double bonds sit in the middle of the chain. A vinyl ester molecule has an epoxy backbone of aromatic rings, ether links and hydroxyl groups, with a methacrylate group at each end; the diester product is then crosslinked through those end groups only [media] [S34]. The result is far fewer hydrolyzable sites per unit of network, and the ones that exist sit at the crosslinks.
The moisture data follow the chemistry. In Sandia and Montana State University tests of resin-transfer-molded neat resins in 50 °C distilled water, the vinyl esters and the isophthalic polyester absorbed much less moisture than the orthophthalic polyester and the unmodified epoxy, and the laminates ranked in the same order [statistic] [S9]. The same program found the baseline orthophthalic polyester had inadequate resistance to hot, wet conditions for blade use [statistic] [S9]. Epoxy's weakness is not hydrolysis: an amine-cured epoxy has no ester links, but it absorbs several percent water, which softens the network and lowers its glass transition temperature [statistic] [S9].
Two consequences matter for buyers. First, the backbone sets the ceiling: the guide describes novolac-based Derakane 470 resins as offering high resistance to solvents, acids and oxidizers such as chlorine and high strength retention at temperature, which makes them the resins of choice for flue gas [company] [S3]. Second, hardener choice changes an epoxy's chemistry: anhydride-cured epoxies form ester links during cure, so an 'epoxy' quotation without the hardener named tells you little about chemical service.
↔ Scroll horizontally to see the full diagram.
3. Strength, elongation and heat resistance: what the datasheets say
Tensile strength does not separate the families; elongation does. A Derakane Signia 411 casting reaches 86 MPa with 5–6% elongation, against 60 MPa and 1.9% for a corrosion-grade isophthalic polyester and 60–75 MPa with 8–16% for the EPIKOTE RIMR 135/RIMH 137 infusion epoxy [company] [S1] [S5] [S7]. Elongation is what lets the matrix follow the fibers under cyclic strain, thermal cycling and impact without microcracking, which is why vinyl ester replaced polyester in corrosion equipment that sees pressure and temperature swings, and why epoxy dominates fatigue-loaded structures.
Heat resistance is the opposite story. Signia 411 has a heat deflection temperature of 105 °C at 1.8 MPa; Ashland lists the Momentum 411-350 casting at 105 °C and a Tg of 120 °C after a 2-hour post-cure at 120 °C [company] [S1] [S2]. An epoxy can be far below or far above that. Westlake's EPON 828 table lists deflection temperatures from 31 °C with a polyetheramine to 120 °C with DETA or TETA at room temperature, 150 °C with metaphenylenediamine and 180 °C with nadic methyl anhydride after a 260 °C cure [company] [S6]. The RIMR 135 infusion system is rated for service up to 50 °C without heat treatment and 80 °C after it [company] [S7].
Independent data show how much processing moves these values. In Sandia's resin study, all resins were molded into dog-bone specimens by resin transfer molding, and the measured heat deflection temperatures were 55 °C for orthophthalic polyester, 69 °C for isophthalic, 78 °C for Derakane 411C-50, 75 °C for Derakane 8084, 56 °C for an unmodified epoxy and 83 to 95 °C for two modified epoxies [statistic] [S9]. Those are far below datasheet figures because cure schedules differ. Ask for heat resistance measured on the supplier's actual cure cycle, not the resin maker's post-cured casting.
↔ Scroll horizontally to see the full chart and data table.
Source: Interplastic [S5]; ALTA [S1]; Hexion [S7]. * Bars marked estimate are midpoints of published ranges. Elongation, not strength, is the property that separates the three families.
View the chart data and evidence
| Series | Category | Value | Unit | Evidence / value basis | Reported range | Point note |
|---|---|---|---|---|---|---|
| — | Iso polyester, COR75-AQ-470 | 1.9 | % | Company data | — | — |
| — | Vinyl ester, Signia 411 | 5.5 | % | GetFRP estimate | — | midpoint of 5–6% |
| — | Epoxy, RIMR 135/RIMH 137 | 12 | % | GetFRP estimate | — | midpoint of 8–16% |
↔ Scroll horizontally to see the full chart and data table.
Source: Westlake EPON Resin 828 technical data sheet, Table 1 [S6]. Cure schedules: D-400 30 min at 115 °C; EPIKURE 3370, 3125 and DETA 7 days at 25 °C; MTHPA 2 h at 120 °C + 2 h at 150 °C; MPDA 2 h at 80 °C + 2 h at 150 °C; NMA 1 h at 120 °C + 2–24 h at 260 °C. Same base resin, different hardener. For comparison, the bisphenol-A vinyl ester Derakane Signia 411 casting is 105 °C [S1].
View the chart data and evidence
| Series | Category | Value | Unit | Evidence / value basis | Reported range | Point note |
|---|---|---|---|---|---|---|
| — | D-400 polyetheramine | 31 | °C | Company data | — | — |
| — | EPIKURE 3370 cycloaliphatic | 56 | °C | Company data | — | — |
| — | EPIKURE 3125 polyamide | 90 | °C | Company data | — | — |
| — | DETA aliphatic amine | 120 | °C | Company data | — | — |
| — | MTHPA anhydride | 130 | °C | Company data | — | — |
| — | MPDA aromatic amine | 150 | °C | Company data | — | — |
| — | NMA anhydride | 180 | °C | Company data | — | — |
| Resin | Type | Tensile strength, MPa | Modulus, GPa | Failure strain, % | Heat deflection, °C |
|---|---|---|---|---|---|
| Ortho-polyester 63-AX-051 | orthophthalic | 54.1 | 3.18 | 2.0 | 55 |
| Iso-polyester 75-AQ-010 | isophthalic | 34.6 | 3.32 | 1.2 | 69 |
| Derakane 411C-50 | bisphenol-A vinyl ester | 57.7 | 3.21 | 2.1 | 78 |
| Derakane 8084 | rubber-toughened vinyl ester | 72.6 | 3.25 | 3.0 | 75 |
| System 41 | unmodified epoxy | 52.6 | 3.56 | 1.6 | 56 |
| SC-14 | acrylate-modified epoxy | 68.3 | 2.80 | 3.3 | 83 |
Source: Mandell, Samborsky and Cairns, SAND2002-0771, Table 2 [S9]. One laboratory and one molding method, so the ranking is more comparable than datasheet values; absolute values are lower than post-cured castings.
4. Chemical resistance by named chemical and temperature
The Derakane guide is the most widely used public dataset for corrosion-resistant FRP, and it shows that 'vinyl ester' is not one rating. It lists the highest temperature at which equipment has given good service or passed ASTM C581 testing, for a corrosion barrier 2.5 to 6.3 mm thick whose first 0.3 to 0.8 mm is 95% resin with surfacing veil, backed by 75% resin chopped-strand mat [company] [S3]. Under those conditions, Derakane 411 is rated to 100 °C in 0.5–25% sulfuric acid but only 40 °C in 71–75%, and not recommended above 80%; novolac Derakane 470 holds 105 °C and 80 °C in the same ranges [company] [S3].
The novolac grade is not better everywhere. In 5% sodium hydroxide Derakane 411 is rated to 80 °C and Derakane 470 to only 40 °C, and the guide gives no 470 rating for 10–50% caustic, where 411 is rated to 65–80 °C [company] [S3]. Solvents reverse the picture again: 100% toluene is 25 °C for 411 and 50 °C for 470, 40–100% methanol is not recommended for 411 but 40 °C for 470, and 100% acetone is not recommended for any grade [company] [S3]. Bleach, chlorine dioxide and hydrofluoric acid carry footnotes on veil type and barrier construction; read them with the chemical row.
Public epoxy data are thinner. Westlake states that cured EPON 828 resists a broad range of chemicals including caustic, acids, fuels and solvents, but publishes no temperature table [company] [S6]. That is why corrosion standards and owners specify vinyl ester and polyester grades with chemical guides behind them, and why an epoxy offered for a chemical tank should come with immersion test data for the actual hardener and cure.
↔ Scroll horizontally to see the full chart and data table.
Source: Ashland, Derakane resin selection guide for corrosion resistance (COM19-002, 2018) [S3]. Ratings assume a properly built corrosion barrier and continuous immersion. They are the manufacturer's service experience and ASTM C581 results, not design temperatures for another resin brand.
View the chart data and evidence
| Series | Category | Value | Unit | Evidence / value basis | Reported range | Point note |
|---|---|---|---|---|---|---|
| Derakane 411 (bisphenol-A) | Sulfuric 0.5–25% | 100 | °C | Company data | — | — |
| Derakane 411 (bisphenol-A) | Sulfuric 71–75% | 40 | °C | Company data | — | — |
| Derakane 411 (bisphenol-A) | Hydrochloric 1–15% | 80 | °C | Company data | — | — |
| Derakane 411 (bisphenol-A) | Nitric 11–20% | 50 | °C | Company data | — | — |
| Derakane 411 (bisphenol-A) | Sodium hydroxide 5% | 80 | °C | Company data | — | — |
| Derakane 411 (bisphenol-A) | Toluene 100% | 25 | °C | Company data | — | — |
| Derakane 411 (bisphenol-A) | Deionized water | 80 | °C | Company data | — | — |
| Derakane 470 (novolac) | Sulfuric 0.5–25% | 105 | °C | Company data | — | — |
| Derakane 470 (novolac) | Sulfuric 71–75% | 80 | °C | Company data | — | — |
| Derakane 470 (novolac) | Hydrochloric 1–15% | 110 | °C | Company data | — | — |
| Derakane 470 (novolac) | Nitric 11–20% | 65 | °C | Company data | — | — |
| Derakane 470 (novolac) | Sodium hydroxide 5% | 40 | °C | Company data | — | — |
| Derakane 470 (novolac) | Toluene 100% | 50 | °C | Company data | — | — |
| Derakane 470 (novolac) | Deionized water | 80 | °C | Company data | — | — |
| Exposure | Derakane 411 (bisphenol-A vinyl ester) | Derakane 470 (novolac vinyl ester) | Strongwell pultruded profiles: vinyl ester vs isophthalic polyester |
|---|---|---|---|
| Sulfuric acid | 0.5–25%: 100 °C; 51–70%: 80 °C; 71–75%: 40 °C; above 80%: not recommended | 0.5–25%: 105 °C; 71–75%: 80 °C; above 80%: limited service | 0–30%: both resistant at room temperature; 30–50%: vinyl ester resistant to 160 °F, polyester not resistant |
| Hydrochloric acid | 1–15%: 80 °C; 37%: 40 °C | 1–15%: 110 °C | 0–37%: vinyl ester resistant to 160 °F; polyester not resistant |
| Sodium hydroxide | 5%: 80 °C; 10–25%: 65 °C; 50%: 80 °C | 5%: 40 °C; higher concentrations not rated | 0–5%: vinyl ester resistant to 150 °F; polyester not resistant |
| Methanol 40–100% | not recommended | 40 °C | 100%: neither resistant |
| Acetone 100% | not recommended | limited service only | neither resistant |
| Deionized water | 80 °C | 80 °C | not listed |
Source: Derakane guide [S3]; Strongwell Corrosion Resistance Guide [S8], which covers only Strongwell products and states temperatures are evaluation limits, not necessarily maximum service temperatures.
5. Fatigue, interlaminar shear and toughness: where epoxy earns its premium
The best public fatigue comparison comes from the SNL/MSU/DOE database, which held more than 12,000 test results on over 250 wind-blade material systems by 2012 [statistic] [S10]. For infused laminates with stitched glass fabrics, the epoxy resin significantly out-performed the vinyl ester and polyester in tensile fatigue, and vinyl ester results sat between epoxy and polyester [statistic] [S10]. The mechanism was specific: polyester and vinyl ester laminates cracked along the transverse backing strands of the fabric, and those cracks then failed the 0° fibers; the epoxy laminates showed little sensitivity to fabric weight, construction or sizing [statistic] [S10].
The gap closes with better reinforcement. With aligned strands instead of stitched fabric, the vinyl ester performed similarly to the epoxy, and fatigue stresses at the same life more than doubled for the polyester and vinyl ester laminates [statistic] [S10]. Earlier work on lower fiber contents typical of hand lay-up showed very little effect of resin type on fatigue [statistic] [S10]. For a filament-wound tank at 40% glass, resin choice is a corrosion decision; for an infused blade laminate at 54–58% fiber volume, it is a fatigue decision.
Delamination tells a similar story. The same program measured very low mode I toughness for the baseline orthophthalic polyester, while the toughened vinyl ester Derakane 8084 and a modified epoxy had the highest mode II toughness dry at room temperature; the epoxy lost mode II toughness when hot and wet, and the two vinyl esters stayed good under all conditions [statistic] [S9]. Datasheet interlaminar shear strength for the RIMR 135/137 system is 42–46 MPa with glass fabric and 47–55 MPa with carbon at 43% fiber volume [company] [S7]. Ask for short-beam shear (ASTM D2344 or ISO 14130) on your laminate, conditioned wet if the part sees water.
Rule of thumb from the fatigue data
At hand lay-up fiber contents, resin type barely changes tensile fatigue life. At infusion fiber contents with stitched fabrics, epoxy out-performs vinyl ester, which out-performs polyester. If you must use vinyl ester in a fatigue part, specify aligned reinforcement or a toughened grade and test the actual fabric.
6. Cure, shrinkage, styrene emissions and post-cure
The two resins cure by different chemistry, and that difference drives the shop. A vinyl ester is catalyzed in the field: ALTA's table for Signia 411 reaches a 30-minute gel at 22 °C with 1.5 phr MEKP-925H and 0.30 phr cobalt, and warns that less than 0.05 phr cobalt can under-cure the laminate [company] [S1]. An epoxy has no such dial. Hexion's infusion system must be mixed at 100:30 ± 2 by weight, and the datasheet states that more or less hardener does not speed or slow the reaction but leaves an incomplete cure that cannot be corrected [company] [S7]. Its pot life halves for every 10 °C rise, and a large mixed mass can exceed 200 °C [company] [S7].
Shrinkage follows the cure. A cured Signia 411 casting shrinks 8% by volume and Momentum 411-350 7.8% [company] [S1] [S2]; Westlake attributes epoxy's strong adhesion partly to low shrinkage during cure but does not publish a number [company] [S6]. Shrinkage shows up as print-through on cosmetic surfaces, residual stress at bonded inserts and sink in thick sections, which is one reason epoxy is preferred for tooling and precision bonded assemblies.
Styrene is the regulatory difference. Signia 411 contains 44% styrene and uses a suppression additive with a vapor suppression effectiveness factor of 0.55 under 40 CFR 63 Subpart WWWW, which ALTA equates to the emissions of a 37.0% styrene resin in manual lay-up [company] [S1]. The US OSHA limit remains 100 ppm as an 8-hour average with a 200 ppm ceiling [official] [S11]; Germany applies 20 ppm and Australia moves from 50 ppm to 20 ppm on 1 December 2026 [official] [S12]. A Chinese fabricator quoting vinyl ester work for an EU or Australian site should show local exhaust and personal monitoring, not just a resin brand.
Post-cure is part of the specification for both. Ashland's laminate data for Momentum 411-350 follow 24 hours at room temperature plus 6 hours at 80 °C, and its casting data 2 hours at 120 °C [company] [S2]. Hexion's neat-resin data use 24 hours at 23 °C plus 15 hours at 60 °C [company] [S7]. The Derakane guide recommends post-curing linings and coatings whenever possible because thin layers develop little exotherm [company] [S3].
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| Jurisdiction | 8-hour limit | Short-term limit | Status |
|---|---|---|---|
| United States, OSHA Table Z-2 | 100 ppm | 200 ppm ceiling; 600 ppm peak for 5 min in any 3 h | in force |
| Germany | 20 ppm | 40 ppm | in force (as tabulated by Composites Australia) |
| Australia, Safe Work Australia | 20 ppm (from 50 ppm) | 40 ppm (from 100 ppm) | from 1 December 2026 |
| European Union | no EU-wide value | — | set nationally |
Source: OSHA 29 CFR 1910.1000 Table Z-2 [S11]; Composites Australia, May 2026 [S12].
7. Secondary bonding, repair and multi-stage laminates
Thick vinyl ester equipment is built in stages, so the bond between a cured laminate and the next layer is a design issue. ALTA states that properly made Signia 411 laminates built up in multiple steps have shown good interlaminar adhesion, that minimal or no resin excess is needed between layers, and that fabricators should confirm their own practice gives similar results [company] [S1]. The product is formulated to reduce or eliminate surface preparation between layers during initial production [company] [S1]. That claim covers same-resin staging during fabrication, not repairs to a laminate that has been in service.
Epoxy is the stronger adhesive. Westlake cites shear strengths up to 6,000 psi (41 MPa) for EPON 828 systems and good adhesion to a broad range of substrates [company] [S6]. Its weakness is the surface it leaves: WEST System describes amine blush as a wax-like, water-soluble by-product of cure, more common in cool, moist conditions, removed by washing with water and an abrasive pad and then sanding glossy areas with 80-grit paper [company] [S33]. Peel ply removes most of that work.
Mixed systems need their own qualification. Neither datasheet covers bonding one family to the other, so treat any assembly that combines them as a separate process: write the bonding direction (which resin goes over which), surface preparation and test (lap shear or flatwise tension, with failure mode recorded) into the purchase order, and run it on coupons cut from production laminate.
8. Which resin for tanks, pipes, rebar, blades and grating
Most specification decisions are set by the governing standard and the owner's practice. ASME RTP-1-2023 covers stationary reinforced thermoset vessels for corrosive service at pressures up to 15 psig internal or external above hydrostatic head [official] [S13]; in Europe, EN 13121 does the same for above-ground GRP tanks. Both are built around the corrosion-barrier construction that the Derakane guide assumes, and both expect the fabricator to name the resin and show chemical data for it.
For concrete reinforcement, ACI CODE-440.11-22 covers only GFRP bars conforming to ASTM D7957-22 [official] [S14], and Strongwell's guide advises vinyl ester rather than polyester where pultruded FRP must keep long-term structural integrity in concrete [company] [S8]. For wind blades, epoxy is the standard matrix: China revised its national standard for vacuum-infusion epoxy for wind blades as GB/T 31293-2025, in force since 1 January 2026 [official] [S27], and Swancor reports that its blade epoxy volumes rose 17.62% in 2024 [company] [S23].
| Service | Usual resin | Why | Evidence to request |
|---|---|---|---|
| Chemical tanks, scrubbers and ducts | Bisphenol-A vinyl ester; novolac vinyl ester for hot acids, solvents and flue gas | Hydrolysis and caustic resistance; room-temperature cure for large shop-built parts | Resin maker's written recommendation for each chemical, concentration and upset temperature; ASME RTP-1 or EN 13121 design basis |
| Process and sewer pipe | Vinyl ester liner with polyester or vinyl ester structural wall; epoxy for some oil and gas pipe | Liner carries the chemistry, structure carries the pressure | Liner resin and thickness, hydrostatic design basis, ASTM C581 data |
| Pultruded grating and profiles in corrosive plants | Vinyl ester; isophthalic polyester for mild exposure | Strongwell rates isophthalic polyester not resistant to 0–37% hydrochloric acid and 5% caustic | Resin grade on the mill certificate; fire rating for the actual resin |
| GFRP rebar | Vinyl ester | Alkaline concrete pore solution; ACI 440.11 scope tied to ASTM D7957 bars | ASTM D7957 qualification and lot tests |
| Wind blades and spar caps | Epoxy (infusion and pultrusion) | Fatigue at high fiber volume; adhesion to carbon | GB/T 31293-2025 or DNV-type material qualification, Tg after the actual cure |
| Marine hulls and decks | Vinyl ester skin coat or laminate over polyester; epoxy for high-performance builds | Blister resistance; secondary bonding | Water-uptake and laminate test data |
| Carbon fiber structures | Epoxy | Polyesters bond poorly to carbon fiber; epoxy is the usual resin, with some vinyl ester use | Interlaminar shear on the actual fiber and sizing |
Source: ASME RTP-1 [S13]; ACI CODE-440.11-22 [S14]; Strongwell [S8]; GB/T 31293-2025 [S27]; SAND2002-0771 on carbon fiber bonding [S9]; GetFRP selection practice.
9. China supply: producers, capacity and 2026 resin prices
China is long on epoxy. SunSirs counted more than 4 million tonnes of national epoxy capacity in 2025 with an operating rate of 51.44%, 720,000 t/yr of new capacity added in the year and an expected top-five concentration of 58% [media] [S19]. Hongchang Electronic Materials, a listed producer, made 152,121 t of epoxy in 2025 at an average ex-VAT price of RMB 13,208/t, essentially flat on 2024, while its bisphenol-A input fell 14.6% and epichlorohydrin rose 32.8% [company] [S21]. Its Zhuhai site has 295,000 t/yr of design capacity running at 65.39%, with 80,000 t/yr more under construction [company] [S22]. The same annual report notes that some wind-blade makers produce their own epoxy, which makes blade-resin sales more competitive [company] [S22].
Prices swing more than buyers expect. East China liquid epoxy hit a four-year low of RMB 12,800–13,200/t in June 2023 [statistic] [S20], traded at RMB 13,600–14,000/t in April 2025 [statistic] [S36], spiked to RMB 19,000–19,500/t in March 2026 [statistic] [S18], then fell: the market average dropped from RMB 17,467 to 15,300/t in May and to 13,750/t by the end of June [statistic] [S15]. E-51 recovered to RMB 14,500–14,700/t in late July and the market rose a further 9% in September [statistic] [S16] [S17]. Lock price formulas to a published index for long contracts.
Vinyl ester is a smaller, more concentrated business. Swancor Advanced Materials, which describes itself as the domestic leader in vinyl ester by output and sales, sold 42,483 t of corrosion-resistant materials and 30,985 t of wind-blade resin materials in 2024 from five plants with 313,205 t of combined design capacity [company] [S23]. Its revenue rose 20.29% to RMB 1.797 billion in 2025 [company] [S24]. Dividing 2024 segment revenue by volume gives about RMB 16,300/t for the corrosion-resistant line and about RMB 19,300/t for blade materials, ex-VAT and including export sales [estimate: RMB 691.1 m ÷ 42,483 t; RMB 598.6 m ÷ 30,985 t] [S23]. Polyester is the cheap baseline: FRP-grade polyester at Yongyue Technology averaged RMB 6,819/t ex-VAT in January to September 2025, down 10.0%, with styrene bought at RMB 6,912/t [company] [S25].
What that means per part: the vinyl ester premium over polyester, about RMB 9,450/t of resin on these figures, adds roughly RMB 3.3 per kilogram to a laminate at 35% resin, but about RMB 7.1 per kilogram to a corrosion-barrier layer at 75% resin [estimate: (16,267 − 6,819) × 0.35 and × 0.75 ÷ 1,000]. That is why many Chinese tank and pipe shops quote a vinyl ester liner on a polyester structural wall; ask which layers carry which resin.
↔ Scroll horizontally to see the full chart and data table.
Source: SunSirs epoxy market reports [S20] [S36] [S18] [S15] [S16]. * Midpoints of published ranges [estimate]. Observations mix East China liquid epoxy quotes and the SunSirs market average and are unevenly spaced. September 2026 added a further 9% [S17].
View the chart data and evidence
| Series | Category | Value | Unit | Evidence / value basis | Reported range | Point note |
|---|---|---|---|---|---|---|
| — | Jun 2023 | 13000 | RMB/t | GetFRP estimate | — | midpoint of 12,800–13,200, East China |
| — | Apr 2025 | 13800 | RMB/t | GetFRP estimate | — | midpoint of 13,600–14,000, East China ex-works |
| — | Mar 2026 | 19250 | RMB/t | GetFRP estimate | — | midpoint of 19,000–19,500, East China |
| — | Early May 2026 | 17467 | RMB/t | Statistic | — | market average |
| — | End May 2026 | 15300 | RMB/t | Statistic | — | market average |
| — | End Jun 2026 | 13750 | RMB/t | Statistic | — | market average |
| — | End Jul 2026 | 14400 | RMB/t | GetFRP estimate | — | midpoint of E-51 14,200–14,600 |
↔ Scroll horizontally to see the full chart and data table.
Source: Yongyue Technology [S25]; Hongchang Electronic Materials [S21]; Swancor 2024 annual report [S23]. * Swancor values are segment revenue divided by sales volume [estimate]. Company averages, not spot quotes; different years. Use as relative positions, not prices to quote.
View the chart data and evidence
| Series | Category | Value | Unit | Evidence / value basis | Reported range | Point note |
|---|---|---|---|---|---|---|
| — | Polyester, Yongyue 2025 | 6819 | RMB/t | Company data | — | — |
| — | Liquid epoxy, Hongchang 2025 | 13208 | RMB/t | Company data | — | — |
| — | Vinyl ester line, Swancor 2024 | 16267 | RMB/t | GetFRP estimate | — | — |
| — | Blade epoxy, Swancor 2024 | 19319 | RMB/t | GetFRP estimate | — | — |
| Company | Resins | Scale indicator | GetFRP profile |
|---|---|---|---|
| Swancor Advanced Materials (Shanghai, SSE 688585) | Vinyl ester, wind-blade epoxy, recyclable resins | 42,483 t corrosion materials and 30,985 t blade materials sold in 2024; 313,205 t design capacity | — |
| Hongchang Electronic Materials (SSE 603002) | Liquid and specialty epoxy | 152,121 t produced in 2025; Zhuhai 295,000 t/yr design capacity | — |
| ALTA Performance Materials | Derakane and Derakane Signia vinyl esters, polyester, gelcoat | Global producer of the Derakane line referenced in this report | View profile |
| AOC | Polyester, vinyl ester, SMC/BMC resins | Global corrosion and molding resin producer | View profile |
| Changzhou Rixin Group | Polyester, vinyl ester, gelcoat, SMC/BMC | China Composites Expo exhibitor | View profile |
| Techstorm Advanced Material | Epoxy for filament winding, pultrusion, infusion and prepreg | Cable-core rod and spar-cap pultrusion systems | View profile |
| Wells Advanced Materials (Shanghai) | Wind, infusion, pultrusion and RTM epoxy systems | Blade and structural adhesive epoxies | View profile |
| Dalian Liansheng New Materials | Epoxy resins and hardeners | Specialty epoxy and curing agents | View profile |
| Zhejiang Tianhe Resin | Unsaturated polyester | Polyester and adhesive producer | View profile |
Source: Company filings [S21] [S22] [S23] and GetFRP profiles. Listing is by product scope, not a ranking. Confirm the producing plant and resin grade on every certificate.
10. Chinese and international standards, HS codes and duties
China's national standards cover polyester and epoxy, not vinyl ester. GB/T 8237-2025, the product standard for liquid unsaturated polyester resin for fiber-reinforced plastics, replaced the 2005 edition on 1 January 2026 [official] [S26]; GB/T 13657-2011 covers bisphenol-A epoxy resin [official] [S28]; GB/T 31293-2025 covers vacuum-infusion epoxy for wind blades [official] [S27]. A search of the national registry for vinyl ester resin returned no national standard, so Chinese vinyl ester is sold against the maker's own specification and tested with polyester and casting methods such as GB/T 2567-2021 [official] [S29] [S30]. Name the resin maker and grade in the order, not 'vinyl ester to GB'.
On trade, epoxide resins enter the United States under HTS 3907.30.00 at 6.1% MFN [official] [S31]. The line is on Section 301 List 2 (heading 9903.88.02, 25%), and Chinese goods also carry the 12.5% country tariff of heading 9903.05.31, a 43.6% stack in total [official; estimate for the sum] [S32]. The US International Trade Commission made a negative final injury determination on epoxy resin from China in April 2025, so no anti-dumping order followed [media] [S19]. Saudi Arabia opened an anti-dumping investigation on Chinese epoxy in February 2026, and ECHA's addition of BPAF to the SVHC list raises compliance work for some specialty epoxies sold into the EU [media] [S35].
| Standard | Scope | Use in an RFQ |
|---|---|---|
| GB/T 8237-2025 | Liquid unsaturated polyester resin for FRP (in force 1 Jan 2026) | Polyester and baseline test methods |
| GB/T 13657-2011 | Bisphenol-A epoxy resin | Epoxy equivalent and viscosity grades (E-51, E-44 class) |
| GB/T 31293-2025 | Vacuum-infusion epoxy for wind turbine blades (in force 1 Jan 2026) | Blade and infusion epoxy acceptance |
| GB/T 2567-2021 | Test methods for resin casting properties | Neat-resin tensile, flexural and HDT on Chinese test reports |
| GB/T 24148.9-2014; GB/T 14520-2025 | Total volume shrinkage of UP resin; residual styrene in UP-based plastics | Shrinkage and residual styrene checks |
| ASTM C581; ASTM C582 | Chemical resistance testing of thermoset laminates; contact-molded laminates for corrosion service | Chemical qualification and laminate construction |
| ASME RTP-1-2023; EN 13121 | Corrosion-resistant thermoset vessels; above-ground GRP tanks | Design basis for tanks and vessels |
| ASTM D648 / ISO 75; ASTM D638 / ISO 527 | Heat deflection; tensile properties | Datasheet comparability |
| ASTM D2344 / ISO 14130 | Short-beam (interlaminar) shear | Laminate acceptance |
Source: SAMR national standards registry [S26] [S27] [S28] [S29] [S30]; ASME [S13]; Derakane guide for ASTM C581 [S3].
11. RFQ and acceptance checklist for vinyl ester and epoxy laminates
Most disputes with resin and laminate suppliers come from an RFQ that names a family instead of a system. The checklist below turns the evidence above into requirements with values to request. Ask each bidder to answer every line; a missing answer is information.
- 1. Resin identity: maker, grade and plant (for example Derakane Signia 411, or EPIKOTE RIMR 135 with RIMH 137), with the current technical data sheet and safety data sheet.
- 2. Cure package: peroxide type and phr, cobalt and accelerator phr, inhibitor, target gel time at shop temperature; for epoxy, hardener grade and mix ratio with tolerance (for example 100:30 ± 2).
- 3. Post-cure: time and temperature actually used, and Tg by DSC or DMA on a witness coupon from the same cure cycle.
- 4. Chemical service: the resin maker's written recommendation for each chemical, concentration range, normal and upset temperature; Derakane-type ratings apply only with the stated corrosion barrier.
- 5. Corrosion barrier: veil type (C-glass or synthetic), resin-rich layer 0.3–0.8 mm at about 95% resin, total barrier 2.5–6.3 mm at about 75% resin, and which layers use which resin.
- 6. Laminate data on the actual construction: glass content by burn-off (ASTM D2584 or ISO 1172), tensile and flexural results, Barcol hardness, and short-beam shear wet and dry where relevant.
- 7. Styrene control for vinyl ester and polyester: local exhaust, personal monitoring results against the destination limit (20 ppm where applicable), and residual styrene by GB/T 14520-2025 for food or potable contact.
- 8. Secondary bonding: surface preparation, peel ply, maximum open time between stages, and a bond test with failure mode recorded.
- 9. Batch traceability: resin lot numbers on the laminate record, storage below 25 °C, shelf life (12 months from manufacture for Derakane, 24 months for the RIMR system).
- 10. Commercial: price formula tied to a published epoxy or styrene index for contracts over three months, HS code and duty basis, and written notice before any resin or plant change.
Shortcut for corrosion equipment
If the supplier cannot name the resin grade, the corrosion-barrier build and the chemical recommendation, do not compare its price with a bid that can. The resin premium is a few renminbi per kilogram; a failed liner costs the vessel.
Frequently asked questions
Is vinyl ester better than epoxy?
For chemical service, usually yes: a bisphenol-A vinyl ester such as Derakane 411 is rated to 100 °C in 0.5–25% sulfuric acid and 80 °C in 5% caustic, with public ratings for hundreds of chemicals. For fatigue, bonding and carbon fiber, epoxy is better: infusion epoxies reach 8–16% neat-resin elongation against 5–6% for vinyl ester, and epoxy laminates out-performed vinyl ester in tensile fatigue with stitched fabrics.
Is vinyl ester stronger than polyester?
Yes, mainly in toughness. A Derakane Signia 411 casting reaches 86 MPa tensile strength with 5–6% elongation, against 60 MPa and 1.9% for a corrosion-grade isophthalic polyester. On pultruded profiles, Strongwell rates its vinyl ester grade resistant to 0–37% hydrochloric acid and 5% caustic where its isophthalic polyester grade is not resistant.
Can you put epoxy over vinyl ester, or vinyl ester over epoxy?
Neither resin maker's datasheet covers cross-family bonding, so qualify it as a separate process. ALTA's Signia 411 data cover vinyl ester built up over vinyl ester in stages with minimal surface preparation. On cured epoxy, any amine blush must be washed off with water and the gloss sanded with 80-grit paper before the next layer; test lap shear or flatwise tension on production coupons and record the failure mode.
How much does vinyl ester cost compared with epoxy in China?
In 2026, East China liquid epoxy ranged from about RMB 13,750 to 19,500 per tonne. Swancor's corrosion-resistant (vinyl ester) materials averaged about RMB 16,300 per tonne in 2024 and FRP-grade polyester about RMB 6,800 per tonne in 2025, ex-VAT. The vinyl ester premium over polyester adds roughly RMB 3 per kilogram to a laminate at 35% resin.
What temperature can vinyl ester resin withstand?
A bisphenol-A vinyl ester casting has a heat deflection temperature of about 105 °C and a Tg of about 120 °C after post-cure. In service the limit depends on the chemical: Derakane 411 is rated to 80 °C in deionized water and 100 °C in dilute sulfuric acid, while novolac grades such as Derakane 470 reach 105–110 °C in some acids.
Why is epoxy used for wind turbine blades instead of vinyl ester?
Fatigue at high fiber volume. In the Sandia and Montana State database, infused epoxy laminates with stitched glass fabrics significantly out-performed vinyl ester and polyester in tensile fatigue, because the latter cracked along transverse backing strands. China's vacuum-infusion blade epoxy standard was revised as GB/T 31293-2025, in force from 1 January 2026.
Does vinyl ester contain styrene?
Yes. Vinyl esters are diluted to roughly 35–45% styrene; Derakane Signia 411 contains 44%. The US OSHA limit is 100 ppm over 8 hours, while Germany applies 20 ppm and Australia moves to 20 ppm on 1 December 2026. Epoxy laminating systems contain no styrene.
Which resin should GFRP rebar use?
Specify vinyl ester. ACI CODE-440.11-22 covers concrete reinforced with GFRP bars that conform to ASTM D7957-22, and Strongwell's corrosion guide advises vinyl ester rather than polyester wherever pultruded FRP must keep long-term structural integrity in concrete, whose pore solution is alkaline. Ask for ASTM D7957 qualification and lot test reports with the resin named.
Sources and scope
Figures were cross-checked against primary documents where available; secondary citations are marked in each scope note. Company figures are reported as disclosed by the companies themselves. This note is an independent market assessment and not investment advice.
- [S1]ALTA Performance Materials, Derakane Signia 411 epoxy vinyl ester resin technical datasheet (May 2025, distributor-hosted PDF)
Viscosity 370 mPa·s, 44% styrene, gel-time tables, VSE 0.55 and emission equivalents, casting properties (86 MPa, 3,100 MPa, 5–6%, 105 °C, 8% shrinkage), post-cured laminate at 38.6% glass, secondary bonding statements. Manufacturer document on a distributor host.
- [S2]Ashland, Derakane Momentum 411-350 epoxy vinyl ester technical datasheet (document 1701, approved 2015, issued 2018)
Casting Tg 120 °C, HDT 105 °C, 7.8% shrinkage, cure schedules (24 h RT + 2 h 120 °C casting; 24 h RT + 6 h 80 °C laminate), 12-month shelf life, storage below 25 °C. Older legacy grade; distributor host.
- [S3]Ashland, Derakane epoxy vinyl ester resins: resin selection guide for corrosion resistance (COM19-002, 2018)
Maximum service temperatures by chemical and concentration for Derakane 411, 441, 451, 455, 470, 510, 515 and 8084; corrosion-barrier construction assumed; ASTM C581 basis; product descriptions. Manufacturer data, not a rating for other brands.
- [S4]ALTA Performance Materials, epoxy vinyl ester resins product page
Positioning of epoxy vinyl esters for corrosion-resistant tanks, pipes and pultruded profiles; toughness of epoxy with polyester-like processing and lower-temperature cure.
- [S5]Interplastic Corporation, CoREZYN COR75-AQ-470 isophthalic corrosion-resistant polyester technical datasheet (rev. 3/20)
Viscosity 375–475 cP, 45% maximum styrene, casting tensile 60 MPa, modulus 3,655 MPa, elongation 1.9%, HDT 117 °C. Distributor-hosted manufacturer sheet.
- [S6]Westlake Epoxy, EPON Resin 828 technical data sheet (revision June 2021)
Viscosity 110–150 P, WPE 185–192, Table 1 of curing agents with cure schedules and deflection temperatures (31–180 °C), tensile above 69 MPa, adhesive shear up to 41 MPa, chemical resistance statement. Distributor-hosted manufacturer sheet.
- [S7]Hexion, EPIKOTE Resin MGS RIMR 135 and EPIKURE Curing Agent MGS RIMH 134–137 technical data sheet (rev. 2015)
Germanischer Lloyd approval, mix ratio 100:30 ± 2, pot life halves per 10 °C, neat resin 60–75 MPa and 8–16% elongation, laminate ILSS 42–46 MPa glass and 47–55 MPa carbon at 43% fiber volume, service temperature limits.
- [S8]Strongwell, Corrosion Resistance Guide for industrial products
Vinyl ester vs isophthalic polyester ratings for pultruded profiles and grating; advice to use vinyl ester for long-term structural integrity in concrete. Strongwell products only; temperatures are evaluation limits.
- [S9]Mandell, Samborsky and Cairns, Fatigue of composite materials and substructures for wind turbine blades, Sandia contractor report SAND2002-0771
Neat-resin properties of ortho and iso polyester, vinyl esters and epoxies in one laboratory; moisture absorption ranking; mode I and II toughness; polyester bonding to carbon fiber.
- [S10]Samborsky, Mandell and Miller, The SNL/MSU/DOE fatigue of composite materials database: recent trends (AIAA, 2012)
Database of over 12,000 results; epoxy out-performs vinyl ester and polyester in tensile fatigue with stitched fabrics; vinyl ester similar to epoxy with aligned strands; little resin effect at hand lay-up fiber contents.
- [S11]OSHA, 29 CFR 1910.1000 Table Z-2
Styrene: 100 ppm 8-hour TWA, 200 ppm ceiling, 600 ppm peak for 5 minutes in any 3 hours.
- [S12]Composites Australia, Styrene exposure limits in Australia: regulatory context and industry implications (19 May 2026)
Australian styrene limit revised to 20 ppm TWA and 40 ppm STEL from 1 December 2026, replacing 50 and 100 ppm; comparison table listing Germany at 20 and 40 ppm. Industry association summary.
- [S13]ASME RTP-1-2023, Reinforced thermoset plastic corrosion-resistant equipment (standards listing)
Edition RTP-1-2023 issued February 2024; scope limited to vessels at pressures not exceeding 15 psig internal or external above hydrostatic head.
- [S14]American Concrete Institute, ACI CODE-440.11-22 preview (preface and chapter 1)
Code applies to concrete reinforced with GFRP bars conforming to ASTM D7957-22; effective 2 September 2022. The resin requirement is not stated in the preview pages.
- [S15]SunSirs, The domestic epoxy resin market saw a significant decline in June (2 July 2026)
Market average price fell from RMB 15,300 to 13,750/t in June 2026; causes. Price agency report.
- [S16]SunSirs, The domestic epoxy resin market remained stable with a slight increase in July (5 August 2026)
Liquid E-51 high of RMB 14,500–14,700/t on 21 July 2026; end-month RMB 14,200–14,600/t; solid E-12 RMB 13,400–13,800/t.
- [S17]SunSirs, The epoxy resin market saw significant gains in September (10 October 2026)
September 2026 monthly increase of 9% for liquid and solid epoxy; drivers and outlook. No absolute price stated.
- [S18]SunSirs, The East China epoxy resin market was weakening on March 18 (19 March 2026)
East China liquid epoxy RMB 19,000–19,500/t net, ex-works, 18 March 2026.
- [S19]SunSirs, 2025 year-end review of the epoxy resin industry (7 January 2026)
China capacity above 4 Mt, operating rate 51.44%, 720 kt new capacity, CR5 58% expected; US ITC negative final determination (30 April 2025); Hongchang phase II start-up. Price agency commentary, tagged media.
- [S20]SunSirs, Domestic epoxy resin dropped to a four-year low (7 June 2023)
East China liquid epoxy RMB 12,800–13,200/t on 6 June 2023; bisphenol-A and epichlorohydrin prices.
- [S21]Hongchang Electronic Materials (SSE 603002), 2025 epoxy resin business operating data announcement (April 2026)
2025 epoxy output 152,120.86 t, sales 151,073.01 t, revenue RMB 1.995 billion; average ex-VAT price RMB 13,208/t vs 13,200/t; raw material price changes. Unaudited company data.
- [S22]Hongchang Electronic Materials (SSE 603002), 2025 annual report
Zhuhai design capacity 295,000 t/yr at 65.39% utilization, 80,000 t/yr under construction; statement that some wind-blade makers produce their own epoxy.
- [S23]Swancor Advanced Materials (SSE 688585), 2024 annual report
Leadership claims in vinyl ester and blade epoxy; 2024 sales of 42,483 t corrosion-resistant and 30,985 t blade materials; segment revenue; five plants with design capacities and utilization.
- [S24]Swancor Advanced Materials (SSE 688585), 2025 annual report summary (30 March 2026)
2025 revenue RMB 1,796.8 million, up 20.29%; market position statements.
- [S25]Yongyue Technology (SSE 603879), 2025 third-quarter operating data announcement
FRP and other polyester resin average ex-VAT price RMB 6,818.95/t in Jan–Sep 2025 (−9.99%); styrene purchase price RMB 6,911.95/t. Unaudited.
- [S26]SAMR national standards registry, GB/T 8237-2025 Liquid unsaturated polyester resin for fiber-reinforced plastics
Issued 30 June 2025, in force 1 January 2026; replaces GB/T 8237-2005.
- [S27]SAMR national standards registry, GB/T 31293-2025 Vacuum infusion epoxy resin for wind turbine blades
Issued 30 June 2025, in force 1 January 2026; replaces the 2014 edition.
- [S28]SAMR national standards registry, GB/T 13657-2011 Bisphenol-A epoxy resin
Issued 30 December 2011, in force 1 June 2012.
- [S29]SAMR national standards registry, search results for unsaturated polyester resin standards
GB/T 14520-2025 residual styrene, GB/T 24148.9-2014 total volume shrinkage and other UP-R standards; a parallel search for vinyl ester resin returned no national standard on 3 November 2026.
- [S30]SAMR national standards registry, search results for resin casting and epoxy test standards
GB/T 2567-2021 test methods for resin casting properties (replacing 2008); related epoxy test standards such as GB/T 1630.2-2023.
- [S31]USITC Harmonized Tariff Schedule, subheading 3907.30.00 epoxide resins
General (MFN) rate 6.1% for epoxide resins; polyester lines 3907.91.40 at 5.8% and 3907.91.50 at 6.5%.
- [S32]USITC Harmonized Tariff Schedule, chapter 99 (2026 revision 22)
3907.30.00 and 3907.91 lines listed in U.S. note 20(d) for heading 9903.88.02 (25%); heading 9903.05.31 adds 12.5% on products of China under U.S. note 52. Check exclusions before quoting landed cost.
- [S33]WEST SYSTEM, Surface preparation
Amine blush as a water-soluble cure by-product; removal with water and abrasive pad; sanding glossy areas with 80-grit paper.
- [S34]Wikipedia, Vinyl ester resin (citing Ullmann's Encyclopedia of Industrial Chemistry)
Vinyl ester as the esterification product of an epoxy with acrylic or methacrylic acid, dissolved in about 35–45% styrene and cured by free radicals. Secondary reference used only for basic chemistry; tagged media.
- [S35]SunSirs, Key events in the epoxy resin industry in February 2026 (6 March 2026)
Saudi Arabia anti-dumping investigation into epoxy resins from China and others (9 February 2026); ECHA adds BPAF to the SVHC list; capacity projects.
- [S36]SunSirs, Market situation of liquid epoxy resin in some regions of China on April 17th (18 April 2025)
East China liquid epoxy RMB 13,600–14,000/t ex-factory on 17 April 2025; wind-power orders noted.
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