Dioctyl Phthalate DOP / DEHP

PVC Cable Sheathing Outside RoHS-Compliant Boundaries

Compounding of flexible PVC insulation for non-EU cable constructions begins with a suspension resin of K-value 67–70, DEHP at 40–60 phr, a calcium-zinc or barium-zinc stabiliser at 3–7 phr, calcined clay filler at 10–25 phr, and a lubricant system adjusted for wire-line screw slip. The dry blend is mixed in a high-speed turbo mixer to a drop temperature of 105–115°C, then pelletised on a counter-rotating twin-screw extruder with L/D 28:1 and barrel zones from 145°C to 180°C. A single-screw wire coating unit with a crosshead die and pressure tooling applies the insulation at melt temperature 170–185°C. At 50 phr DEHP, volume resistivity measured by ASTM D257-14 remains above 1×10¹⁴ Ω·cm after conditioning for 24 h at 23°C and 50% RH. Tensile properties conforming to IEC 60811-501:2012 typically show a tensile strength of 16–20 MPa and elongation at break of 300–380% for unfilled insulation; the addition of calcined clay reduces elongation to 180–250% while improving cut-through resistance. The upper continuous conductor temperature is usually limited to 75°C because DEHP volatility and exudation accelerate above this threshold; 90°C-rated constructions require trimellitate or polymeric plasticiser.

Regulatory compliance is the decisive boundary. Under EU RoHS 2011/65/EU Annex II entry 7, DEHP is restricted to 0.1 wt% in homogeneous material for electrical and electronic equipment placed on the EU market. This restriction excludes DOP-based cable from most RoHS-scope products after the 22 July 2019 application date. Production of DEHP-containing cable in the EU also requires authorisation under REACH Annex XIV, so current use is concentrated in non-EU jurisdictions or products outside the RoHS scope where national migration limits are less stringent.

Representative formulation response envelope for suspension PVC K-value 67 with Ca-Zn stabiliser; production values vary with resin particle size distribution, filler type, and extrusion history. No product specification should be derived from this table without full qualification testing.

Calendered vinyl flooring compounds built around suspension PVC K-value 66–68 are plasticised with DEHP at 50–80 phr in the foamable core and 40–55 phr in the transparent wear layer. A Farrel continuous mixer discharges at 165°C, after which the melt passes to a two-roll mill and then an inverted-L four-roll calender with roll temperatures 170–195°C. The foamable core contains azodicarbonamide at 1.5–3.0 phr; decomposition in a hot-air fusion oven at 185–205°C produces a closed-cell structure with density 0.60–0.80 g/cm³. The wear layer is applied at 170–185°C and embossed on the last calender roll. Hardness of the fused wear layer is 70–80 Shore A per ISO 868; tensile strength per ISO 527-2 is 14–18 MPa for a 0.35 mm sheet. Residual indentation after 150 min at 23°C is typically below 0.10 mm for the compact layer when measured by EN 433:1994. DEHP-containing flooring sold in the EU as an article triggers REACH Article 33 SVHC notification at 0.1 wt%; EU manufacture itself requires authorisation under REACH Annex XIV, so production lines for this formulation are located outside the EU or use non-phthalate plasticisers.

On full-scale calender lines, the principal failure mode is plasticizer exudation at the wear-layer interface when DEHP exceeds 55 phr and roll take-off speed exceeds 25 m/min. Exuded DEHP causes detachment of polyurethane top coats and increases the coefficient of friction on the sheet surface. The compounder must therefore control plasticizer absorption by raising dry-blend temperature to 110°C before Banbury mixing and limiting storage of compounded sheet to 48 h at 30°C.

What Is the Realistic Fusion Window for DEHP Plastisols?

Knife-over-roll coating of PVC paste resin for synthetic leather, footwear uppers, and tarpaulin covers is governed by the gelation and fusion profile of the plastisol. Dispersion-grade paste resin of K-value 72–80 is mixed under high shear in a planetary mixer; DEHP is added at 50–75 phr to give a Brookfield RVT viscosity of 2,000–6,000 mPa·s at 20 rpm and 25°C. At this loading the plastisol remains pseudoplastic, allowing coating at line speeds of 15–35 m/min. The coated web enters a forced-air fusion tunnel with zone set points from 160°C to 200°C; complete fusion requires a substrate surface temperature of 180–195°C for 60–120 s, depending on coat weight and air velocity. At 170°C the plastisol remains incompletely fused, producing haze, low peel strength, and surface defects; above 205°C, DEHP volatilisation increases and fabric scorch risk becomes measurable. The practical throughput ceiling is therefore set by a narrow dwell-temperature plateau of ±5°C for thin skins, a primary process conflict in high-speed coating.

Peel adhesion to polyester and cotton fabrics is product-specific, but DEHP migration to the bond line weakens wet adhesion after hydrolysis ageing. Automotive interior applications generally reject DEHP-containing skins because DIN 75201:2011 fogging tests show condensate mass above OEM limits when DEHP exceeds 5 wt% of the plastisol formulation. For articles exported to the EU, REACH Article 33 notification applies at 0.1 wt% DEHP in the coated fabric. The formulation is therefore retained for industrial tarpaulins, bookbinding covers, and non-automotive upholstery outside EU RoHS or REACH authorisation requirements.

Extrusion-cast PVC film using DEHP at 30–45 phr is compounded for industrial stationery, book covering, non-food adhesive tape backings, and self-adhesive decorative sheet. In a 65 mm single-screw extruder with L/D 30:1 and barrier screw, barrel temperatures from 160°C to 190°C are maintained; the melt is polished through a three-roll stack at 60–90°C before embossing. Hardness is 75–85 Shore A per ISO 868; tensile strength measured by ISO 527-3 is 15–20 MPa for film at 0.20 mm thickness. DEHP surface migration over time lowers print adhesion on uncoated film; corona treatment above 42 mN/m is required before solvent-based ink application. The film is not suitable for food contact under Regulation (EU) No 10/2011 because DEHP is not listed as an authorised additive for food-contact plastics.

If Low-Temperature Flexibility Outweighs Migration Losses in Industrial Hose

Soft PVC profiles, appliance gaskets, suction hose, and pneumatic tubing are produced by single-screw extrusion of dry blends containing 50–75 phr DEHP, suspension PVC K-value 64–70, and 10–30 phr coated calcium carbonate. The dry blend is prepared in a turbo mixer to 105°C and cooled; the extruder screw has a compression ratio of 2.5:1 and barrel temperatures from 150°C to 180°C, giving a melt pressure of 12–18 MPa at the die. Hardness after cooling is 55–70 Shore A per ISO 868; low-temperature brittleness is -25°C to -30°C per ASTM D746-20 for unfilled compounds. The primary limitation is extraction in paraffinic and aromatic oils: immersion in ASTM Oil No. 3 at 70°C for 72 h can produce mass loss of 5–12% because DEHP is soluble in the oil phase. This extraction shrinks gaskets and increases hardness by 8–15 Shore A, creating seal leakage; nitrile rubber vinyl blends or polymeric plasticiser are required for oil-contact service.

Modifying Nitrocellulose Coatings with a High-Molecular-Weight Phthalate

Nitrocellulose lacquers for wood finishing, gravure ink opacifiers, and screen-printing clear coats are plasticised with DEHP at 3–8 wt% of total non-volatile solids to reduce film cracking and improve cold flex. The plasticizer is pre-dispersed in a ketone-ester solvent blend before high-speed dispersion; final viscosity at 25°C is 30–60 s through a Ford #4 cup per ASTM D1200-10. Free-film elongation improves from brittle failure below 2% to 8–15% when tested by ISO 527-3. Compatibility is not unlimited: DEHP loading above 10 wt% of non-volatile solids tends to produce surface exudation and blocking under stacking pressure during warehouse storage. DEHP remains extractable by ethanol and sebum simulants, so these formulations are not suitable for toy coatings under REACH Annex XVII entry 51, which caps DEHP at 0.1 wt% of plasticised material in toys and childcare articles.

Where solvent-cement open time must be extended without altering PVC solubility, DEHP is occasionally added as a secondary plasticiser at 3–10 phr in white or grey PVC pipe cements based on 10–18 wt% PVC resin dissolved in cyclohexanone-THF. The mixed adhesive is applied by brush or trowel at 5–25°C; solvent cement joints are tested according to ASTM D2564-20 requirements for PVC pipe and fittings. DEHP addition improves the flexibility of the dried bond line but lowers resistance to aromatic hydrocarbon service and increases long-term extractables in industrial pressure systems. For EU industrial supply, the formulation must be reviewed against REACH Article 33 notification and Annex XIV authorisation duties because DEHP remains present at 0.1 wt% or more in many finished adhesives.