Dioctyl Phthalate (DOP) 99.5%: General Purpose PVC Plasticizer Bulk Export is traded as bis(2-ethylhexyl) phthalate, CAS 117-81-7, EINECS 204-211-0. The bulk-export grade is supplied at 99.5% minimum ester content and is produced by the controlled esterification of phthalic anhydride with 2-ethylhexanol, followed by neutralisation, water washing, steam stripping under reduced pressure, and filtration. The resulting oily ester is compatible with suspension, emulsion, and mass-polymerised PVC across a broad addition range. Export certificates of analysis normally report free acidity, moisture, and colour because these parameters directly control PVC compound heat stability, clarity, and storage behaviour. Typical physical data include density 0.984–0.988 g/cm³ at 20 °C, refractive index 1.485–1.487 at 25 °C, dynamic viscosity 72–85 mPa·s at 20 °C, and APHA colour 20–30. Sampling and testing follow ASTM D1045-19 for plasticizers used in poly(vinyl chloride), with ester content commonly determined by gas chromatography with flame ionisation detection under an ISO/IEC 17025-accredited supplier method.

Typical bulk-export specification for DOP 99.5%

Parameter	Specification	Reference method
Ester content	99.5% minimum	GC-FID, supplier-accredited method
Acid value	0.07 mg KOH/g maximum	ASTM D1045-19
Water content	0.10% maximum	ASTM E203-16
Colour	20–30 APHA maximum	ASTM D1209-05(2019)
Density at 20 °C	0.984–0.988 g/cm³	ASTM D4052-22
Refractive index at 25 °C	1.485–1.487	ASTM D1218-21
Dynamic viscosity at 20 °C	72–85 mPa·s	ASTM D445-23
Flash point, open cup	not less than 200 °C	ASTM D92-18

What Distinguishes DOP from Fast-Fusing Speciality Plasticizers in PVC?

Addition of 50 phr DOP to a K-value 69–71 suspension PVC resin yields flexible compounds with Shore A hardness 78–85 measured by ISO 7619-1:2010, tensile strength 16–22 MPa, and elongation at break 300–400% under ISO 527-2:2012. Reducing the concentration to 40 phr raises hardness by approximately 5–7 Shore A units and lowers elongation, while increasing the plasticizer level to 70 phr typically brings Shore A hardness to 65–70 and reduces tensile strength. These ranges are observed on production-scale twin-roll mills and in twin-screw compounding; they are not universal because resin K-value, stabiliser type, filler loading, and process residence time each modify the final mechanical envelope. DOP is a moderately solvating plasticizer rather than a fast-fusing plasticizer. Dry blends begin to develop gel strength at approximately 120–130 °C, and acceptable fusion for opaque sheet requires stock temperatures above 160 °C. Below this threshold, residual PVC grain boundaries lower tensile strength and surface gloss under ISO 2813:2014 measurement.

Low-temperature flexibility follows a concentration-dependent threshold. A 50 phr DOP compound commonly shows a Clash-Berg stiffness below −20 °C, but the exact value is influenced by test speed, stabiliser package, and specimen conditioning. Electrical behaviour also shifts with plasticizer level. Volume resistivity of a 50 phr DOP formulation conditioned at 23 °C and 50% relative humidity is typically reported in the range 10¹²–10¹⁴ Ω·cm under ASTM D257-14, which places DOP-containing flexible PVC in the insulating class for non-critical low-voltage sheathing where the end-use does not fall under regulated electrical and electronic equipment restrictions. DOP is not selected where extraction resistance against n-alkanes, edible oils, or polar solvents is required because its low molecular weight and moderate vapour pressure permit progressive migration from the PVC matrix.

In plastisol compounding, Brookfield RVT viscosity data are obtained on a paste-resin formulation with 60 phr DOP and a K-value 67 emulsion PVC. Using spindle No. 6 at 20 rpm and 25 °C, following ISO 2555:2018, the initial viscosity is commonly 2500–7000 mPa·s. Viscosity may fall during the first 24–48 h of storage as the plasticizer solvates the paste resin, then stabilise if moisture uptake is kept below 0.10%. Gelation initiates near 120 °C; full fusion in a Mathis oven at 120 s residence time is reached between 160 °C and 180 °C. Below 150 °C, the plastisol retains granular structure that lowers fused tensile strength. Above 185 °C, dehydrochlorination can accelerate if the heat stabiliser dose is marginal, producing yellowing and release of hydrogen chloride. These boundaries define the processing window for thick films and rotationally cast hollow articles.

When Volatility and Die Pressure Control the Calendering and Extrusion Window

Flexible PVC production with DOP is constrained by volatility and fusion limits, particularly on continuous lines. In a corotating twin-screw extruder with L/D 30:1, a barrel temperature profile of 150/160/170/175 °C, and die pressure below 180 bar, DOP at 40–60 phr lowers melt viscosity and drive torque while allowing stable strand pelletising. At barrel temperatures above 185 °C, plasticizer volatility increases. Gravimetric loss from a small DOP sample held at 125 °C for 3 h is normally 0.2% maximum, but at die and calender roll temperatures approaching 195–200 °C visible condensate and roll plate-out become more likely, especially when external lubricant dosage is below 0.2 phr. For calendered film and sheet, the stock temperature at the nip is maintained at 160–175 °C. Below 155 °C, incomplete fusion produces a matte surface and lower tensile strength; above 180 °C, fuming and colour formation may appear at the bank mark. The acceptable nip window is therefore narrow and dependent on residual stabiliser and lubricant balance.

Transfer from ISO tank containers and lined bulk vessels imposes additional boundary conditions. The material is loaded under a nitrogen pad of 0.2–0.5 bar gauge, and moisture exclusion is critical because water above 0.10% can reduce clarity and contribute to hydrolysis during high-temperature compounding. Carbon steel tanks with epoxy phenolic linings or stainless steel are used for extended storage. At 20 °C the viscosity is 72–85 mPa·s, but at lower ambient temperatures the viscosity climb can slow transfer. Warm-water or low-pressure steam coils set at 30–50 °C reduce viscosity to approximately 35–50 mPa·s for pumping; heating above 60 °C is avoided because prolonged exposure may promote slight colour reversion. Centrifugal pumps with mechanical seals and PTFE-compatible gaskets are specified for bulk handling. Sampling is performed from top, middle, and bottom connections to detect stratification or free water prior to discharge into shore tanks.

Surface Migration, Extraction, and Restricted Electrical-Enclosure Use

Migration of DOP from plasticised PVC into adjacent styrenic or acrylic surfaces is a documented failure mode in laminated profiles and co-extruded edge bands. A 50 phr compound aged at 60 °C in contact with impact-modified polystyrene for 14 days can transfer sufficient plasticizer to create haze and reduce the tensile strength of the styrenic substrate; published data for this specific multi-layer configuration are limited. DOP is not considered a permanent plasticizer in high-migration applications such as pressure-sensitive graphic films or solvent-sensitive laminates because its low molecular weight enables diffusion along a concentration gradient. Solvent extraction resistance is lower than that of polyester or trimellitate plasticizers, and DOP-containing flexible PVC is therefore not selected for oil-resistant hose covers unless a barrier layer or crosslinking strategy is included.

Regulatory status imposes operational boundaries that must be verified at the order level. Bis(2-ethylhexyl) phthalate is listed as a substance of very high concern under REACH Article 57(c) for reproductive toxicity. Articles supplied to the European Economic Area that contain DEHP above 0.1% by mass must trigger communication duties under REACH Article 33. Under REACH Annex XVII entry 51, DEHP is restricted in toys and childcare articles at concentrations greater than 0.1% by mass of the plasticised material. In electrical and electronic equipment placed on the EU market, Directive 2011/65/EU Annex II limits DEHP to 0.1% by weight in homogeneous materials. These restrictions do not eliminate bulk supply for industrial flexible PVC in non-regulated regions; they define the end-use segments where DOP cannot be specified without regulatory clearance.

Compliance matrix for bulk-export DOP under typical regulatory frameworks

Framework	Threshold	Operational consequence
EU REACH Annex XVII entry 51	0.1% by mass of plasticised material	Not permitted in toys or childcare articles above threshold
EU REACH Article 33	0.1% w/w in article	Supplier communication required for SVHC presence
EU RoHS Directive 2011/65/EU Annex II	0.1% by weight in homogeneous material	Not permitted in covered electrical and electronic equipment above threshold
US California Proposition 65	No numerical safe harbour in bulk form	Warning required for consumer product exposures above the listed phthalate trigger

For general-purpose flexible profiles, hoses, floorings, and calendered sheet produced outside regulated electrical or toy segments, the 99.5% DOP grade is combined with 3–5 phr epoxidised soybean oil and 2–4 phr of a calcium-zinc or barium-zinc stabiliser to maintain thermal stability during twin-screw compounding. Formulations above 80 phr DOP can show plasticizer exudation at high humidity, and direct contact with polycarbonate or impact-modified polystyrene glazing should be avoided unless migration-resistant barrier layers are specified. The material remains a low-cost primary plasticizer where regulatory exposure limits are not exceeded.