Epoxidized Soybean Oil ESO

Why Do Flexible PVC Compounders Replace a Fraction of Primary Plasticizer with ESO?

In flexible PVC dry blends for calendered film, extruded profiles, and wire jacketing, ESO is introduced at 3–10 phr as a secondary plasticizer and acid-scavenging co-stabilizer. Typical primary plasticizer systems contain DINP or DOTP at 50–70 phr, and ESO displaces 5–15 % of that primary mass rather than functioning as a complete substitute. The oxirane oxygen content of 6.3–7.0 %, determined by ASTM D1652, supplies a theoretical HCl capture capacity of approximately 148 mg HCl/g ESO because each oxirane oxygen can ring-open with one equivalent of HCl to form a chlorohydrin. The compound is dry-blended in a high-intensity mixer operating at 25–40 m/s tip speed. Liquid plasticizers and ESO are injected after resin temperature reaches 80 °C, and the blend is held to 110 °C before transfer to a cooling mixer at 45 °C. On a single-screw extruder with L/D 24:1–30:1 and compression ratio of 2.5:1–3.5:1, barrel zones are maintained between 150 °C and 175 °C, with die head pressure in the range 150–350 bar. ESO lowers plateau torque on the extruder drive because its viscosity of 350–450 mPa·s at 25 °C measured by ASTM D445 improves flow in the metering section. Migration resistance is evaluated by compression for 24 h at 50 °C under 0.5 kg/cm² using ASTM D3291-11; formulations exceeding 15 phr ESO begin to show visible exudation on calendered sheet when final nip roll temperature exceeds 175 °C.

Calendered film lines running ESO-containing compounds require polished or chrome-plated rolls because ESO is slightly more hydrophilic than phthalate plasticizers and can build up on matte steel surfaces over extended runs. Gauge dispersion is checked by contact thickness scanning, while tensile properties are measured by ASTM D638-14 on Type IV die-cut specimens and low-temperature torsional stiffness by ASTM D1043-16. Primary plasticizer reduction at equal Shore A hardness can increase volumetric resistivity of cable jackets when measured by ASTM D257-14. Flame performance of plenum-grade compounds may shift with ester content; oxygen index is evaluated by ISO 4589-2:2017. Because ESO behaviour in calendered films is influenced by stabilizer type, filler loading, and roll shear history, production mill trials are used to define the maximum acceptable replacement ratio for each specific film gauge.

Rigid PVC dry blends for pressure pipes, window profiles, and cellular foam board are compounded with ESO at 2–7 phr inside calcium/zinc stabilizer packages. The epoxy group does not simply scavenge free HCl; it also functions as a Lewis base that interrupts zinc-catalysed polyene propagation when zinc stearate and calcium stearate are combined in ratios from 1:2 to 1:4. Fusion behaviour is followed in a torque rheometer with roller rotors at 30 rpm and 180 °C; gelation time typically moves 5–15 s later when ESO replaces an equal mass of paraffin wax, although the actual shift is stabilizer-package-dependent and must be measured on the target dry blend. A counter-rotating twin-screw extruder with L/D 20:1–36:1 processes the compound at barrel temperatures from 170 °C to 195 °C and die temperature 190–210 °C; screw oil temperature is held below 150 °C to prevent pre-gelation in the feed zone. Early colour drift in white profiles is measured in a ventilated oven at 180 °C per ISO 182-2; production trials show that compounds without ESO exhibit yellowing 10–20 min earlier at the same stabilizer loading.

The operational boundary in rigid PVC appears when ESO exceeds 7 phr: Vicat softening temperature measured according to ISO 306:2022 drops by 2–4 °C compared with a non-ESO reference, which may compromise pressure pipe classified under ISO 1452-2:2009. Notched Charpy impact strength measured by ISO 179-1:2023 on 4 mm specimens can shift from ductile to brittle at 0 °C when filler level is above 8 phr. Because ESO has an iodine value below 2.0 g I₂/100 g, it contributes negligible oxidative crosslinking, but it does not behave as a primary heat stabilizer and must not replace organotin or Ca/Zn components below their minimum dosage. In foam extrusion on a conical twin-screw foaming line with L/D 24:1, die swell is controlled by reducing ESO to 2–3 phr when azodicarbonamide is used at 0.2–0.8 phr.

Plastisol Rheology, Gelation Profiles, and Migration Boundaries in Dip-Formed Parts

Dip-coated tool handles and rotationally cast parts are produced from PVC plastisol formulated with dispersion resin having K-value 62–70, primary plasticizer at 60–90 phr, and ESO at 5–10 phr. Brookfield RVT viscosity measured with spindle 4 at 20 rpm after 24 h maturation is typically 1500–3500 mPa·s; ESO depresses initial viscosity by 10–20 % relative to a straight DINP plastisol because its density of 0.990–0.998 g/cm³ increases solvency without lowering gelation temperature as sharply as butyl benzyl phthalate. Shelf life is assessed by viscosity rise at 35 °C over 28 days; a rise greater than 25 % indicates poor dispersion or moisture uptake, with pre-drying of fillers required when ambient relative humidity exceeds 60 %. Gelation temperature is recorded on a Haake viscometer as the crossover of storage and loss modulus during temperature sweep from 25 °C to 180 °C at 3 °C/min; typical gelation onset shifts from 82 °C to 86 °C when 10 phr ESO is introduced.

Fused parts are cured in an air oven at 190–200 °C for 5–12 min depending on wall thickness; under-fusion is detected by solvent swell ratio in methyl ethyl ketone using ASTM D471-16. Exudation is evaluated by compression at 70 °C for 48 h under polypropylene foam per ASTM D3291-11; at 12 phr ESO, glossy coatings on steel plate occasionally develop an oily film if gelation temperature is below 185 °C. Hardness of aged specimens is tested by ASTM D2240-15e1 on Shore A and Shore D; ESO at 10 phr typically reduces Shore A by 2–4 points after 168 h at 70 °C. These plastisols are used for sleeves and grips where phthalate restrictions are managed through EU Substance of Very High Concern screening and Toy Safety Directive 2009/48/EC compliance protocols.

When Epoxidized Soybean Oil Is Ring-Opened to a Polyol for Cast Polyurethane

ESO is converted to a polyester polyol by acid-catalysed ring opening with methanol, butanol, or fatty acids at 120–150 °C under nitrogen. The oxirane oxygen value measured by ASTM D1652 falls to 0.5 % or below, while hydroxyl number measured by ASTM D4274-21 rises to 90–130 mg KOH/g. Acid value after neutralization is controlled below 1.0 mg KOH/g per ASTM D974 to prevent premature reaction with isocyanate. The polyol has a viscosity of 1500–4000 mPa·s at 25 °C measured by ASTM D445, which imposes preheating to 50–60 °C before metering into a low-pressure polyurethane dispensing machine. Casting trials in open molds use a prepolymer with NCO content 18–22 % and a stoichiometric index of 95–105; gel time measured by ASTM D2471-20 extends by 30–90 s relative to petroleum polyols when ESO-derived polyol comprises 20 wt% of the polyol blend.

Hardness of cured cast elastomer specimens is tested with ISO 868:2003, tensile strength by ISO 37:2017, and tear strength by ISO 34-1:2022. Because the ESO backbone contains secondary hydroxyl groups from epoxy ring opening, cure advancement can be slower than for primary-hydroxyl polyols, and demold time is extended by 2–6 h at 60 °C. Formulators avoid amine-based catalysts in ESO-derived polyol systems when residual acid value exceeds 0.5 mg KOH/g because salt formation increases phase separation. In water-blown rigid foam at 2–3 parts water per 100 parts polyol, silicone surfactant adjustment is required, and spray foam trials are needed because cell structure is surfactant-dominated.

In nitrile rubber and PVC/NBR blends intended for oil-resistant hoses and gaskets, ESO is added at 5–15 phr as a bio-based plasticizer that softens the compound without reducing acrylonitrile content. Mooney viscosity ML(1+4) at 100 °C measured by ASTM D1646-19 drops from 65–70 MU to 45–55 MU when 10 phr ESO replaces an equal mass of dioctyl adipate, but grade-specific data must be generated on the target NBR polymer. Vulcanization curves are recorded on a moving die rheometer at 170 °C for 20 min per ISO 6502:2023; scorch time t_s2 shifts 0.5–1.5 min longer with ESO, and maximum torque decreases by 5–10 % due to reduced compound viscosity. Compression set compounds for oilfield packers are cured with sulfur donors and tested after 70 h at 100 °C per ASTM D395-18 Method B; ESO does not migrate to the surface as readily as phthalate plasticizers under 25 % compression.

Low-temperature flexibility is measured by Gehman stiffness per ASTM D1053-16; the T₁₀ value is 2–4 °C lower in ESO-containing compounds compared with phthalate references at equal Shore A hardness. Hot air ageing at 100 °C for 168 h according to ISO 188:2023 shows tensile retention above 80 % when antioxidant systems include 1–2 phr of hindered phenolic and 0.5 phr of phosphite. ESO is not a reactive vulcanizing plasticizer because the iodine value below 2.0 g I₂/100 g provides negligible sulfur-reactive unsaturation, so it does not substitute for vulcanized vegetable oil in sulfur donor recipes. In polar elastomers, ESO addition above 20 phr can reduce adhesion to metal inserts in bonded gaskets; pull-out adhesion is evaluated according to ASTM D429-14 Method B.

The Four-Ball Wear Scar Limit Appears at 10 wt% ESO in Non-Ionic Microemulsions

Within metalworking fluid concentrates based on vegetable oil methyl esters and non-ionic surfactants, ESO is incorporated at 5–10 wt% to adjust lubricity. Four-ball wear preventive characteristics are measured by ASTM D4172-20 at 40 kg load, 1200 rpm, 75 °C, and 60 min; formulations above 10 wt% ESO occasionally show increased wear scar diameter due to higher acid value generation during the test. Extreme pressure behaviour is screened by ASTM D2783-19 load-wear index; ESO alone does not provide sulfur or phosphorus active antiwear layers, so it is combined with 0.5–2 wt% zinc dialkyldithiophosphate or sulfurized fat. Oxidative stability of the concentrate is measured by ISO 3924:2019 rotating pressure vessel oxidation test; ESO batches with acid value above 0.5 mg KOH/g are excluded because metal carboxylate precipitation can clog 10 µm filters in central lubrication systems.

In lithium complex grease, ESO at 2–5 wt% of the base oil reduces thickener content when penetration is controlled to NLGI 2 under ASTM D217-21. Dropping point measured by ASTM D2265-20 is maintained above 260 °C, but continued use in open bearings at 150 °C may increase viscosity due to oxidative polymerization of the residual unsaturation present at iodine value ≤2.0 g I₂/100 g. Because ESO is not classified as a lubricating oil base stock under ISO 6743-4:2015, its use is limited to additive or co-base fluid status, and published performance data for these specific configurations is limited.