DIDP (Diisodecyl Phthalate): Properties, Uses in Plastics and Regulatory Status

DIDP (diisodecyl phthalate, CAS 68515-49-1) is a high-molecular-weight ortho-phthalate used as a primary plasticizer for flexible PVC, chosen where permanence and low volatility matter more than plasticizing efficiency, above all in wire and cable insulation and automotive interiors. Because DIDP carries a C10 alcohol chain rather than the C9 chain of DINP or the C8 chain of DEHP, it sits at a different point on the efficiency-versus-permanence trade-off, which is where most selection decisions start.

DIDP is registered under REACH, is not a Substance of Very High Concern, is restricted only in mouthable toys and childcare articles under REACH Annex XVII entry 52, carries a group migration limit of 1.8 mg/kg together with DINP in EU food-contact plastics, remains authorised by the US FDA for three food-contact uses, and has been on the California Proposition 65 list for developmental toxicity since 20 April 2007. DIDP is one of 56 plasticizer pages in our directory of plastic additives, each carrying the same identity, dosage and regulatory fields.

This page holds the data-sheet view and the compliance view together: identity and the two CAS numbers, physical constants, dosage evidence, 4 application areas, efficiency and volatility against DINP and DEHP, the dated regulatory matrix for the EU, the United States, Canada and Japan, the comparison with DINP, DPHP, DEHP, DOTP and TOTM, and the trade names a buyer can source.

Table T1. DIDP identity card.

Footnote: identity and physical data from PubChem CID 33599; food-contact status from the consolidated text of Regulation (EU) No 10/2011 of 14 July 2026; Proposition 65 status from the OEHHA chemical list. Status as of 23 September 2026.

What Is DIDP (Diisodecyl Phthalate)?#

DIDP is the diester of phthalic acid (benzene-1,2-dicarboxylic acid) with branched C10 alcohols, a primary plasticizer that softens PVC on its own without a second plasticizer. The two carboxyl groups sit next to each other on the benzene ring, in the ortho position, which is what separates an ortho-phthalate such as DIDP from a terephthalate such as DOTP. Each carboxyl is esterified with isodecyl alcohol, and the product carries the formula C28H46O4, a molecular weight of 446.7 g/mol and the systematic name bis(8-methylnonyl) benzene-1,2-dicarboxylate. Which substances, then, does the name DIDP actually cover?

A primary plasticizer is defined by behaviour in the resin rather than by chemistry. ASTM D883 defines a plasticizer as a substance incorporated into a plastic or elastomer to increase its flexibility, workability or distensibility, and a primary plasticizer is compatible enough with PVC to do that as the sole softener, as ortho-phthalates, terephthalates and trimellitates all are. Plasticizers are the heaviest additive family in polymers by weight, and the hub on plasticizers for plastics compares every class, from ortho-phthalates and terephthalates to adipates, citrates and epoxidised esters.

What does DIDP stand for?#

DIDP stands for diisodecyl phthalate, where "isodecyl" means a branched ten-carbon alcohol chain, not a straight n-decyl chain. The same name appears on supplier paperwork as di-isodecyl phthalate and, in registration documents, as phthalic acid, diesters with primary saturated C9-C11 alcohols with more than 90 % C10.

Why does DIDP have two CAS numbers?#

DIDP carries two CAS numbers, 68515-49-1 and 26761-40-0, because both identify the same commercial product: a mixture of phthalate diesters made from primary saturated C9-C11 alcohols with more than 90 % C10. Annex I of Regulation (EU) No 10/2011 lists both numbers under the single FCM substance number 729, so a compliance check that finds only one of the two is still a match.

The PubChem record CID 33599 resolves through the name diisodecyl phthalate rather than through 68515-49-1, so a data sheet that quotes PubChem is quoting the 26761-40-0 route into the same record. Name the number a source uses whenever the two are compared.

Is DIDP one substance or a mixture?#

DIDP is a mixture, not a single molecule: it is a UVCB substance (of unknown or variable composition), so the molecular weight of 446.7 g/mol and the formula C28H46O4 describe the dominant C10 diester rather than every molecule in the drum. The alcohol feed runs from C9 to C11 with more than 90 % C10, and each alcohol isomer produces its own diester. A specification therefore controls the C10 content and the physical constants, not a single structure.

Is DIDP a high-molecular-weight phthalate?#

Yes: DIDP is a high-molecular-weight phthalate, the group European Plasticisers defines as ortho-phthalates with 7 to 13 carbon atoms in the alcohol-chain backbone, namely DINP, DIDP, DPHP, DIUP and DTDP. The low-molecular-weight group, which holds DEHP, DBP, BBP and DIBP, carries harmonised reproductive-toxicity classifications and falls under REACH Annex XVII entry 51; the high-molecular-weight group carries neither. The split between low and high molecular weight decides which restrictions apply, and phthalate plasticizers sets out both groups with their entries and dates.

The 5 members of the high-molecular-weight ortho-phthalate group are listed below.

• DINP (diisononyl phthalate): C9 alcohol chain, molecular weight 418.6 g/mol, the highest-volume member.
• DIDP (diisodecyl phthalate): C10 branched alcohol chain, molecular weight 446.7 g/mol.
• DPHP (dipropylheptyl phthalate): C10 chain from 2-propylheptanol, molecular weight 446.7 g/mol.
• DIUP (diundecyl phthalate): C11 alcohol chain.
• DTDP (ditridecyl phthalate): C13 alcohol chain, the longest of the group.

DEHP sits in the low-molecular-weight group despite its eight-carbon alcohol, because its alcohol backbone counts only six carbons.

How Does DIDP Plasticize PVC?#

DIDP plasticizes PVC by placing its ester molecules between the polymer chains, weakening the dipole and van der Waals forces between them and lowering the glass transition temperature. The ester carbonyls solvate PVC at its polar carbon-chlorine bonds, while the branched C10 tails hold neighbouring chains apart and create free volume. Compatibility limits that process: the workable difference in solubility parameter between polymer and plasticizer is within ±1.5 (cal/cm3)^0.5.

What does the longer C10 chain change? A longer, heavier chain lowers vapour pressure and slows diffusion out of the article, which formulators call permanence, but each molecule delivers less softening per unit of weight, so the compound needs more of it. The four theories behind the softening itself are explained with solubility parameters on how plasticizers work.

The 4 classic plasticization theories are listed below.

• Lubricity theory: the plasticizer lubricates the polymer chains, letting them slide past one another.
• Gel theory: the plasticizer breaks the polymer-polymer attachments that form a three-dimensional gel.
• Free-volume theory: the plasticizer raises the free volume and so lowers the glass transition temperature.
• Mechanistic theory: plasticization is a dynamic solvation and desolvation equilibrium at the polar sites.

A floor applies to the dose. Below about 15 phr, antiplasticization raises stiffness instead of lowering it, so DIDP is used well clear of that threshold in every flexible application.

What Are the Physical and Chemical Properties of DIDP?#

DIDP is a colourless liquid with a melting point of -50 °C (-58 °F), a boiling point of 253 °C at 4 mmHg (482 to 495 °F at the same reduced pressure) and a density of 0.966 g/cm3 at 20 °C. The density places it below water, so spilled material floats (USCG, 1999), and the melting and boiling points come from the NTP record of 1992.

Table T2. Physical and chemical properties of DIDP.

Footnote: the flash-point row stays open because the source record holds two values that differ by more than 40 °C; this page prints neither until the primary record is re-checked.

Two caveats travel with this table. Lab-supplier listings that print "boiling point above 250 °C" without a pressure are quoting the reduced-pressure figure, so data sheets are comparable only when both give the pressure, and no atmospheric boiling point for DIDP appears in the primary records used here. The molecular weight of 446.7 g/mol is a nominal value for the dominant C10 diester, because DIDP is a UVCB mixture rather than a single compound.

Which Polymers Use DIDP, and at What Dosage?#

DIDP is used almost entirely in flexible PVC, where total plasticizer content ranges from 5 to 65 wt% depending on the target hardness of about Shore A 50 to 90, and as an ester softener in nitrile rubber. That 5 to 65 wt% span is the class range for flexible PVC as a whole, not a DIDP dosage: no DIDP-specific phr or wt% range appears in the primary records, so the evidence below is given as published formulations rather than as a recommended level.

How does a phr figure convert to weight percent? Compound recipes give DIDP in PHR (parts per hundred resin), which converts with the formula wt% = phr of the ingredient divided by the total phr of the formulation, multiplied by 100. The worked conversion for the published cable recipe below turns 55 phr of DIDP into 20.9 wt% of the finished compound, and the same arithmetic works for every other ingredient in that recipe.

Table T3. DIDP level by polymer and application, with the evidence behind each figure.

DIDP in flexible PVC compounds#

A flexible PVC compound needs more DIDP than DEHP for the same hardness: the typical substitution factor of DIDP is 1.11 against DEHP's reference value of 1.00, so about 11 % more plasticizer by weight is required. That penalty buys permanence, because the longer C10 chain lowers vapour pressure and slows migration out of the finished article. Hardness targets, stabilizer choice and filler loading for flexible PVC formulations set the plasticizer level before the substitution factor is applied, so the factor adjusts a level rather than defining one.

The substitution factor of 1.11 is a typical figure from a single secondary source, not supplier data, and it is identical to the figure recorded for TOTM.

DIDP in a sourced PVC cable formulation#

One published PVC cable formulation uses DIDP at 55 phr: PVC K-70 at 100 phr, DIDP at 55 phr, lead-free stabilizer at 2.7 phr, aluminium trihydroxide at 100 phr and zinc borate at 5 phr, a recipe that reaches a limiting oxygen index of 26 to 27 vol % O2 and UL 94 V-0 at 3 mm. The formulation is published by Huber Advanced Materials in its cable brochure, which gives three variants using its Martinal OL-104 LEO grade of aluminium trihydroxide at 100, 50 and 45 phr, the lower loadings balanced with 10 phr of chalk (calcium carbonate).

The base variant totals 262.7 phr, so the DIDP share converts as 55 divided by 262.7, multiplied by 100, which is 20.9 wt% of the compound. Its five ingredients are listed below.

• PVC K-70: 100 phr, the resin and the reference for every other figure.
• DIDP: 55 phr, the sole plasticizer, 20.9 wt% of the compound.
• Lead-free stabilizer: 2.7 phr, the heat-stabilizer package.
• Aluminium trihydroxide (Martinal OL-104 LEO): 100 phr, the flame retardant and smoke suppressant.
• Zinc borate: 5 phr, the flame-retardant synergist.

Cable insulation is where that oxygen index matters: PVC cable insulation targets at least 26 vol % O2, and the three published variants reach 26 to 27 vol % O2 measured by the limiting oxygen index (LOI) method.

DIDP in rubber compounds (NBR)#

DIDP also serves as an ester softener in nitrile rubber, where a Hallstar comparison of NBR with 34 % acrylonitrile and 20 pphr plasticizer recorded a weight loss of 3.8 % after 70 hours at 125 °C (257 °F), against 9.2 % for DOP. Rubber compounding falls outside this directory except where the same ester serves both plastics and elastomers, as DIDP does.

What Is DIDP Used For? 4 Applications in Plastics#

DIDP is used in 4 main plastics applications: wire and cable insulation, automotive interiors and undercoating, calendered film, and coated fabrics. The US EPA records the same picture in its conditions-of-use listing, where DIDP is a plasticizer for flexible PVC in building and construction materials and automotive articles.

• Wire and cable insulation and sheathing: the largest application, in the 70 to 90 °C temperature classes.
• Automotive interiors and undercoating: interior trim and underbody coatings, where low volatility governs the choice.
• Calendered film: tarpaulins, wallcovering and similar flexible sheet.
• Coated fabrics: upholstery and technical textiles with a PVC coating.

Wire and cable insulation#

DIDP is a standard plasticizer for PVC cable insulation and sheathing in the 70 to 90 °C temperature classes, the range it shares with DINP. Above that range the compound moves to a trimellitate, because TOTM meets the 105 °C classes of UL 62 and UL 1581 on its very low volatility, and below it DOTP now replaces both DINP and DIDP in many cable compounds for regulatory rather than technical reasons. The full insulation package, from heat stabilizer to flame retardant and filler, is on additives for wire and cable compounds.

Insulation compounds ask two things of a plasticizer at once: permanence through the cable's service life, and no interference with the flame-retardant package. The Huber formulation shows both conditions met, with DIDP at 55 phr alongside 100 phr of aluminium trihydroxide and 5 phr of zinc borate reaching an oxygen index of 26 to 27 vol % O2. Which ester covers which temperature class is tabulated on plasticizers for wire and cable.

Automotive interiors and undercoating#

DIDP goes into automotive interior trim and underbody coatings because its C10 chain lowers volatility, which is what keeps plasticizer out of the windscreen condensate that fogging tests measure. Interior trim, instrument-panel skins and door-panel laminates all sit in a cabin that reaches high temperatures in sunlight, so a plasticizer that evaporates leaves a stiffened part and a filmed windscreen. The rest of the interior package, from UV stabilizers to scratch-resistance additives, is on additives for automotive plastics.

Carmakers verify plasticizer volatility with fogging and VOC testing for automotive interiors, the methods being DIN 75201 for fogging and VDA 278 for thermal desorption. No DIN 75201 or VDA 278 value for DIDP appears in the primary records used here, so this page names the methods and prints no fogging number. The EPA conditions-of-use listing records automotive articles among DIDP's uses, which confirms the application without quantifying it.

Calendered film and coated fabrics#

Calendered PVC film and coated fabrics use DIDP where the finished article has to keep its hand and flexibility for years, for example in tarpaulins, wallcovering and upholstery fabric. The HSDB use record lists calendered film, coated fabrics and building wire jackets among DIDP's PVC end uses, all of them thin sections with a high surface-to-volume ratio where plasticizer loss shows up as embrittlement first. No dosage, line-speed or fusion data for DIDP in calendering appears in the primary records, so these applications are described here rather than quantified.

How Does DIDP Perform in PVC?#

DIDP trades efficiency for permanence: it needs about 11 % more weight than DEHP for the same hardness, at a typical substitution factor of 1.11 against 1.00, and it loses about 60 % less weight than DOP in the Hallstar heat-aging comparison. The two measured indicators behind that sentence are the substitution factor and the volatility weight loss, and both carry conditions that the table below states in full.

Table T4. DIDP performance indicators, references and test methods.

Footnote: substitution factors are typical figures from one secondary source (Kanademy), not supplier data. The volatility figures are measured in NBR, not in PVC.

How efficient is DIDP compared with DEHP and DINP?#

DIDP is the least efficient of the three common general-purpose plasticizers: its typical substitution factor is 1.11, against 1.04 for DINP and 1.00 for DEHP, so a compound switching from DEHP to DIDP needs roughly 11 % more plasticizer by weight for the same hardness. Efficiency falls as the alcohol chain lengthens, which is the same structural fact that raises permanence, and the ranking therefore runs DEHP, DOTP at 1.03, DINP at 1.04, then DIDP and TOTM at 1.11.

Every one of those figures is a typical value drawn from a single secondary compilation rather than from a supplier specification, and a formulation change is validated on hardness and tensile data, not on a factor. Substitution factors for 15 plasticizers are listed on plasticizer efficiency and substitution factors, where the same caveat applies to each.

How volatile is DIDP?#

DIDP is among the least volatile general-purpose plasticizers: in a Hallstar comparison run on NBR with 34 % acrylonitrile at 20 pphr, DIDP lost 3.8 % of its weight after 70 hours at 125 °C (257 °F), against 4.2 % for DINP and 9.2 % for DOP. The polymer in that test is nitrile rubber, not PVC, so the percentage documents the relative ranking of the esters rather than a PVC compound's loss rate, and no PVC-measured volatility value for DIDP appears in the primary records used here. Two polymeric esters bracket the result: 610P at 3.3 % and 711P at 4.4 %.

The mechanism behind the ranking is molecular weight and vapour pressure. At 446.7 g/mol DIDP outweighs both DEHP (390.6 g/mol) and DINP (418.6 g/mol), and vapour pressure falls as molecular weight rises across an ester series. ASTM D1203 Methods A and B, ISO 176 and ISO 177 are the standards that quantify this in plastics, and they are explained on plasticizer migration, extraction and volatility.

Evaporation is one of three physical loss routes, beside extraction by a contacting liquid and migration into an adjacent material. The same mechanism drives additive volatility for antioxidants and slip agents.

How Does DIDP Interact with Other Plasticizers and Additives?#

DIDP is usually blended rather than used alone: formulators pair it with a fast-fusing ester when gelation speed matters, with ESBO as a co-stabilizer, and with flame-retardant fillers such as aluminium trihydroxide and zinc borate in cable compounds. The three interaction routes that decide a DIDP formulation are listed below.

• Fast fusers: DBP, DIBP, BBP, DIHP and DPGDB raise gelation speed where a high-molecular-weight phthalate on its own fuses slowly, which matters most in plastisol and coating processes.
• Epoxidised co-stabilizers: ESBO (epoxidized soybean oil) acts as a co-stabilizer at 1 to 2 wt% and as a main plasticizer at 25 to 45 wt%, a split measured by Czogała, Pankalla and Turczyn in Materials 14:844 (2021).
• Flame-retardant fillers: aluminium trihydroxide at 45 to 100 phr and zinc borate at 5 phr sit alongside DIDP at 55 phr in the published Huber cable recipe, together with a lead-free stabilizer at 2.7 phr.

Compatibility governs every one of those pairings: a second plasticizer stays in the compound only if its solubility parameter lies within ±1.5 (cal/cm3)^0.5 of the resin's. No DIDP-specific fusion temperature or plastisol viscosity value appears in the primary records used here, so blend ratios for gelation speed are set by trial rather than quoted from this page.

What Is the Regulatory Status of DIDP?#

DIDP is registered under REACH, is not a Substance of Very High Concern, is restricted only in mouthable toys and childcare articles under Annex XVII entry 52, carries a group migration limit of 1.8 mg/kg with DINP in EU food-contact plastics, remains one of the 8 ortho-phthalates the FDA still authorises, and has been on the California Proposition 65 list for developmental toxicity since 20 April 2007 (status 23 September 2026). Two of those instruments point in opposite directions, and the matrix below holds both without aggregating them.

Table T5. DIDP regulatory matrix, status 23 September 2026.

Two entries of Annex XVII carry the EU phthalate restrictions, and DIDP appears in only one of them. Entry 52 and the neighbouring entry 51 are explained on REACH Annex XVII restrictions.

Is DIDP REACH registered, and is it an SVHC?#

Yes, DIDP is registered under REACH (Regulation (EC) No 1907/2006), and no, it is not a Substance of Very High Concern: neither of its two CAS numbers appears on the Candidate List as of 23 September 2026. DIDP is also absent from Annex XIV, so no authorisation is needed for any use in the EU. The registered tonnage band is not stated on this page until the registration dossier is re-checked.

The contrast with the low-molecular-weight group is sharp and dated. DEHP, DBP and BBP have been on the SVHC Candidate List since 28 October 2008 and DIBP since 13 January 2010; DIDP has never been added to it.

Is DIDP allowed in food-contact plastics?#

Yes, with limits: DIDP is listed in Annex I of Regulation (EU) No 10/2011 as FCM substance 729 with no individual migration limit but a group restriction 26 that caps DINP plus DIDP at a total of 1.8 mg/kg, a value lowered from 9 mg/kg by Regulation (EU) 2023/1442. The same entry carries group restriction 32 at an SML(T) of 60 mg/kg and limits the permitted function to three cases: plasticiser in repeated-use articles, plasticiser in single-use articles contacting non-fatty foods other than infant formula, follow-on formula and baby food, and technical support agent at or below 0.1 %, never combined with FCM 157, 159, 283 or 1085. Group restrictions 26 and 32 and the overall migration limit are explained on EU 10/2011.

The 1.8 mg/kg figure traces to a toxicological reassessment. In its opinion of 18 September 2019, EFSA set a group tolerable daily intake of 50 µg/kg body weight per day for DBP, BBP, DEHP and DINP expressed as DEHP equivalents, and an individual tolerable daily intake of 150 µg/kg body weight per day for DIDP, which sits outside that group. The complete SML table for plasticizers in food contact materials compares all 22 listed plasticizer FCM substances.

In the United States, DIDP is one of the 8 ortho-phthalates whose food-contact authorisations survived the FDA final rule of 20 May 2022 (87 FR 31080), and it is authorised under 21 CFR 175.105 for adhesives, 21 CFR 177.2600 for rubber articles intended for repeated use and 21 CFR 178.3910 for surface lubricants. The FDA post-market review announced on 27 May 2026 under docket FDA-2026-N-5776 proposes grouping DEHP, DCHP, DIOP and DINP for cumulative risk assessment; that action is a proposal rather than a restriction, and DIDP is not in the proposed group.

Is DIDP restricted in toys and childcare articles, and how is it tested?#

DIDP is restricted in mouthable toys and childcare articles in the EU, Canada and Japan, but not in the United States: REACH Annex XVII entry 52 caps DINP, DIDP and DNOP at 0.1 % by weight of the plasticised material in toys and childcare articles that children can put in the mouth, while 16 CFR 1307.3 does not list DIDP at all. The US rule permanently restricts DEHP, DBP and BBP and has restricted DINP, DIBP, DPENP, DHEXP and DCHP since 25 April 2018, and DIDP is absent from that closed list of 8.

Table T5b. DIDP in toys and childcare articles, by jurisdiction.

Entry 52 has survived one review: ECHA examined it in 2013 and reported no reason to lift it, a statement recorded in a European Commission dossier rather than in a published review decision. Which plasticizers each jurisdiction allows is tabulated on plasticizers for toys, including the divergence between the EU and US lists that entry 52 creates.

Compliance is demonstrated by phthalate testing in plastics on the plasticised component, not on the whole article, because each limit is written against the plasticised material. Three methods carry that work: CPSC-CH-C1001-09.4 for the US rule, EN 14372 for childcare articles in the EU, and IEC 62321-8 for phthalate determination in electrotechnical products.

Is DIDP on the California Proposition 65 list?#

Yes: DIDP has been on the California Proposition 65 list for developmental toxicity since 20 April 2007, which makes it the one high-molecular-weight phthalate on this page with a reproductive-toxicity listing rather than a cancer listing. DINP, by contrast, was listed on 20 December 2013 for cancer, with a No Significant Risk Level of 146 µg/day, and DEHP carries both types: cancer since 1 January 1988 and developmental and male reproductive toxicity since 24 October 2003.

No safe-harbour level, that is no Maximum Allowable Dose Level, for DIDP appears in the primary records used here, so this page states the listing and its date without stating any exposure threshold. Listing dates for all plasticizers are on California Proposition 65.

What did the EPA conclude in the TSCA risk evaluation of DIDP?#

The US EPA's final TSCA risk evaluation for DIDP, announced in the Federal Register on 6 January 2025 (90 FR 638), found unreasonable risk to female workers of reproductive age from 6 of 49 conditions of use, all of them spray applications, and no unreasonable risk to consumers, the general population or the environment. The evaluation was manufacturer-requested in December 2019, developmental toxicity is the key endpoint, and the 6 conditions of use are spray-applied adhesives, sealants, paints, coatings, lacquers and penetrants.

The 3 findings of the evaluation are listed below.

• Unreasonable risk to female workers of reproductive age in 6 of 49 conditions of use, all spray applications.
• No unreasonable risk to consumers or the general population from any evaluated condition of use.
• No unreasonable risk to the environment from any evaluated condition of use.

Risk-management rulemaking under TSCA section 6(a) follows a finding of unreasonable risk, which makes a future rule on those 6 spray applications the next procedural step rather than an announced measure. That sequence, and how it has run for other additives, is set out on TSCA and plastic additives.

Is DIDP Safe? Health, Safety and Environmental Profile#

DIDP has no harmonised hazard classification under the EU CLP Regulation, but its profile is not empty: companies notifying it to ECHA report aquatic hazards, California lists it for developmental toxicity, and the US EPA identified developmental toxicity as the key endpoint in its 2025 risk evaluation. Those three records come from three instruments with three different tests, and they are stated separately below rather than merged into a verdict.

• Classification: no harmonised classification under Regulation (EC) No 1272/2008, so DIDP carries no mandatory CLP hazard class for human health.
• Aquatic hazard: ECHA C&L inventory notifications for DIDP include H400 (very toxic to aquatic life), H410 (very toxic to aquatic life with long lasting effects) and H411 (toxic to aquatic life with long lasting effects). The share of notifiers reporting each code is not recorded in the primary records used here.
• Assessments: California listed DIDP for developmental toxicity on 20 April 2007, and the EPA's final risk evaluation of 6 January 2025 identified developmental toxicity as the key endpoint while finding unreasonable risk only for female workers of reproductive age in 6 spray-application conditions of use.

Exposure follows production volume, and the high-molecular-weight phthalates carry about 85 % of Western European ortho-phthalate production against under 11 % for the low-molecular-weight group. The exposure and epidemiology picture for the ortho-phthalate group as a whole is summarised on phthalates: health effects.

The EPA finding of no unreasonable risk to consumers is a conclusion about the evaluated conditions of use under one statute, not a general safety statement, and the Proposition 65 listing is a hazard identification, not an exposure estimate. Table T5 holds both, dated, so a reader sees the contradiction rather than a resolution of it.

What Are the Alternatives to DIDP?#

The 4 main alternatives to DIDP in flexible PVC are DINP, DPHP, DOTP and TOTM, while DEHP (DOP) is the low-molecular-weight ortho-phthalate that DIDP and its group replaced. Each differs from DIDP on a different axis: DINP on efficiency and cost, DPHP on isomer chemistry and food-contact status, DOTP on acid class, TOTM on heat class, and DEHP on regulatory obligation.

Table T6. DIDP compared with 5 alternative plasticizers.

Footnote: substitution factors are typical figures from one secondary source (Kanademy), not supplier data. Regulatory status as of 23 September 2026.

Full property data for the same esters, including the non-phthalate options a specification may name instead, sit on the plasticizer comparison page.

DINP vs DIDP: what is the difference?#

DIDP is the choice where permanence decides and DINP where efficiency and cost decide: one extra carbon in the alcohol chain gives DIDP a molecular weight of 446.7 g/mol against 418.6 g/mol for DINP, lower volatility at 3.8 % against 4.2 % weight loss in the Hallstar NBR test, and a higher typical substitution factor of 1.11 against 1.04. The C9 against C10 difference is the whole technical argument, and it moves both properties in the same direction: heavier molecule, lower vapour pressure, less softening per unit weight.

The regulatory positions overlap in Europe and diverge in the United States. Both substances share EU group restriction 26 with a combined SML(T) of 1.8 mg/kg, both fall under REACH Annex XVII entry 52 at 0.1 % in mouthable toys and childcare articles, and neither is a Substance of Very High Concern. In the United States the two separate: DINP has been restricted in children's toys and child care articles under 16 CFR 1307.3(b) since 25 April 2018 and is listed under Proposition 65 for cancer since 20 December 2013, while DIDP is unrestricted in US children's products and is listed under Proposition 65 for developmental toxicity. Their TSCA evaluations ran in parallel: the DINP notice of 15 January 2025 (90 FR 3828) found unreasonable risk to workers from 4 conditions of use against DIDP's 6.

Food contact separates them once more. DINP (diisononyl phthalate) is authorised by the FDA under 21 CFR 178.3740 at or below 43 wt% in vinyl chloride polymers, a quantified ceiling that DIDP's three authorisations do not carry.

DIDP vs DPHP#

DPHP is the isomer of DIDP: both have the formula C28H46O4 and a molecular weight of 446.7 g/mol, but DPHP is built from 2-propylheptanol while DIDP is built from branched isodecyl alcohols. Both are therefore C10 phthalates and both sit in the high-molecular-weight group, which makes their softening behaviour close and their regulatory positions far apart.

DPHP is absent from REACH Annex XVII entries 51 and 52, so it is unrestricted even in mouthable toys, and it is absent from Annex I of Regulation (EU) No 10/2011 in the consolidated text of 14 July 2026, so it cannot be used in EU food-contact plastics at all. That is the mirror image of DIDP's position, which is restricted in mouthable articles but listed for food contact under FCM 729. DPHP (dipropylheptyl phthalate) is also not authorised by the FDA for food contact, and ECHA's use mapping records it at 10 to 35 wt% in plastic materials, with cables, roofing membranes and automotive articles as its main applications, the same three markets DIDP serves.

DIDP vs DEHP (DOP)#

DIDP replaced DEHP in most European cable and automotive compounds for a regulatory reason rather than a technical one: DEHP carries a harmonised Repr. 1B classification (H360FD), has sat on the REACH Candidate List since 28 October 2008 and needs an authorisation after the Annex XIV sunset date of 21 February 2015, while DIDP carries none of those obligations. REACH Annex XVII entry 51 adds a 0.1 % limit on DEHP in all articles since 7 July 2020, against entry 52's limit on DIDP in mouthable toys only, and EU food-contact law gives DEHP an individual SML of 0.6 mg/kg as FCM 283 against DIDP's shared 1.8 mg/kg group limit.

DIDP pays for that freedom in efficiency and is repaid in permanence. The typical substitution factor of 1.11 against DEHP's 1.00 means about 11 % more plasticizer by weight for the same hardness, while the Hallstar heat-aging test on NBR recorded 3.8 % weight loss for DIDP against 9.2 % for DOP after 70 hours at 125 °C (257 °F). DEHP (DOP, dioctyl phthalate) also retained its FDA food-contact authorisations after the final rule of 20 May 2022, so the US and EU positions on the two substances are not parallel.

DIDP vs DOTP: phthalate versus non-phthalate#

DOTP is the non-phthalate route out of DIDP: as a terephthalate it falls outside every ortho-phthalate restriction, it carries an individual food-contact migration limit of 60 mg/kg instead of a 1.8 mg/kg group limit, and its typical substitution factor of 1.03 makes it more efficient than DIDP's 1.11. The structural difference is the position of the second carboxyl group, which sits at position 4 of the benzene ring in a terephthalate and at position 2 in an ortho-phthalate, and that single change puts DOTP outside Annex XVII entries 51 and 52, outside the Proposition 65 list and outside group restriction 26. DOTP / DEHT (dioctyl terephthalate) is the terephthalate that replaces DINP and DIDP in many cable compounds.

The advantage is regulatory and efficiency-based rather than a clean technical win. No volatility value for DOTP appears in the primary records used here, so this page makes no claim that DOTP matches DIDP on permanence, and at 390.6 g/mol DOTP is 56.1 g/mol lighter than DIDP, which argues the other way. Buyers asking for non-phthalate plasticizers are asking for the group that sits outside every ortho-phthalate restriction, and a terephthalate is precisely a non-ortho-phthalate.

DIDP vs TOTM#

TOTM is the step above DIDP in heat class: its three ester arms and molecular weight of 546.8 g/mol give the very low volatility that the 105 °C insulation classes of UL 62 and UL 1581 require, whereas DIDP and DINP serve the 70 to 90 °C classes. The extra ester arm costs the same efficiency that the extra carbon costs DIDP, and both esters carry a typical substitution factor of 1.11 against DEHP's 1.00.

Their regulatory positions differ in kind rather than in degree. TOTM (trioctyl trimellitate) is a trimellitate, not a phthalate, so no ortho-phthalate restriction names it, and it is absent from Annex I of Regulation (EU) No 10/2011, which keeps it out of EU food-contact plastics where DIDP is listed as FCM 729. This page assigns DIDP to a temperature class range, not to a UL file or a yellow-card rating, because a UL rating belongs to a compound rather than to a plasticizer.

Who Manufactures DIDP? Grades and Suppliers#

DIDP is made by the large global plasticizer producers, including ExxonMobil, which sells it as Jayflex DIDP, and BASF, which sells it as Palatinol Z. Two further trade names appear in the market, Vestinol DZ and Plasthall DIDP, and the table below states what is verified about each. Global plasticizer consumption runs at 8.4 Mt per year according to European Plasticisers, and DIDP is one of the general-purpose esters inside that volume.

Table T7. DIDP producers and trade names.

Price follows the C10 alcohol feedstock and the DINP contract, because the two esters compete for the same applications and buyers. No DIDP price figure appears in the primary records used here, so this page quotes none; price drivers for the high-molecular-weight phthalates are tracked on plasticizer prices, and more producers with their locations are in the directory of plasticizer manufacturers.

Buyers should request the supplier's technical data sheet and safety data sheet, the CAS number printed on the certificate of analysis, and a statement of the C10 content, because the UVCB definition means the C9 to C11 distribution varies between producers while the trade name does not change.

Where Does DIDP Sit in the High-Molecular-Weight Phthalate Family?#

DIDP sits in the middle of the high-molecular-weight phthalate class, one carbon above DINP and one to three below DIUP and DTDP, in the group that makes up about 85 % of Western European ortho-phthalate production. The class runs from 7 to 13 carbon atoms in the alcohol-chain backbone, and every step up that scale repeats the same trade: more permanence, less efficiency, higher heat class. The class page for high molecular weight ortho-phthalates lists all 5 members with their chain lengths, against global plasticizer consumption of 8.4 Mt per year.

Longer-chain phthalates: DUP/DIUP and DTDP#

Above DIDP the chain keeps growing: diundecyl phthalate (DUP/DIUP) and ditridecyl phthalate (DTDP) extend the same trade-off, with DTDP used mainly in automotive wire and cable. DUP/DIUP (diundecyl phthalate) adds one carbon to the DIDP chain and DTDP (ditridecyl phthalate) adds three, which places DTDP at the top of the class for permanence. No CAS number, molecular weight or regulatory detail for either substance appears in the primary records used here beyond their membership of the high-molecular-weight group, so neither is given an identity card on this page.

What are the three types of plasticizers?#

Plasticizer suppliers such as Hallstar group specialty plasticizers into 3 types, low-temperature, high-temperature and permanent (polymeric), with the general-purpose commodity esters such as DIDP, DINP and DOTP forming a fourth group beside them. The 3 specialty types are listed below.

• Low-temperature plasticizers: aliphatic diesters, glycol esters and oleates, chosen for flexibility below freezing.
• High-temperature plasticizers: trimellitates such as TOTM and pentaerythritol esters, chosen for heat aging.
• Permanent plasticizers: polymerics, chosen where extraction and migration resistance decide.

A second split cuts across that field: primary plasticizers such as DIDP soften PVC on their own, while secondary plasticizers extend a primary one. All classes are compared on the hub for types of plasticizers.

DIDP in recycled PVC#

DIDP turns up in recycled PVC: in 151 new PVC floorings tested on the Swiss market by Helene Wiesinger and colleagues at ETH Zürich (Environmental Science & Technology, 2024), 29 % contained other ortho-phthalates including DINP and DIDP above 0.1 wt%, alongside 16 % that contained regulated chemicals such as lead and DEHP above 0.1 wt%, both findings linked to recycled PVC feedstock. DINP or DIDP above 0.1 wt% in flooring breaks no rule, because Annex XVII entry 52 covers mouthable toys and childcare articles only.

Legacy plasticizer carry-over is one of the reasons how additives affect plastic recyclability decides whether a recyclate can re-enter a regulated application, since a bale of post-consumer PVC carries no additive history.

Is DIDP banned?#

No: DIDP is not banned anywhere covered on this page; it is restricted to 0.1 % in mouthable toys and childcare articles in the EU and Japan, to 1,000 mg/kg in the vinyl of mouthable parts in Canada, and it is unrestricted in US children's products (status 23 September 2026). Country rules are compared on phthalate restrictions worldwide.

Is DIDP the same as DIDA?#

No: DIDP is diisodecyl phthalate, an aromatic ortho-phthalate, while DIDA is diisodecyl adipate, an aliphatic diester used as a low-temperature plasticizer; the two share the isodecyl alcohol but not the acid. DIDA (diisodecyl adipate) belongs with DOA, DINA, DOS and DOZ in the low-temperature aliphatic diester group.

Does DIDP need an SDS?#

Yes: suppliers provide a safety data sheet for DIDP as for any traded chemical, and the aquatic-hazard notifications (H400, H410 and H411) in the ECHA C&L inventory make section 12 of that sheet worth reading before disposal decisions. DIDP has no harmonised CLP classification, so the hazard statements on a given sheet reflect the supplier notification rather than a mandatory EU label.