Industrial Grade 98% Diethyl phthalate CAS 84-66-2

What is Diethyl Phthalate? How does it work?

Diethyl phthalate (also known as diethyl phthalate, phthalic acid diethyl ester, DEP, ethyl phthalate, phthalic acid diethyl ester, diethyl benzene-1,2-dicarboxylate), with the chemical formula C12H14O4, a molecular weight of 222.24, CAS number 84-66-2, EINECS 201-550-6, UNII UF064M00AF, and InChIKey FLKPEMZONWLCSK-UHFFFAOYSA-N, is a phthalic anhydride-ethanol esterified product consisting of two ethyl esters. It is one of the shortest molecular members in the phthalates plasticizer family. It is a typical industrial oily ester: at room temperature, it is a clear, colorless, oily liquid, almost odorless, heavier than water, insoluble in water, and completely miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons. It has a high boiling point, low vapor pressure, and stable chemical properties. Due to its plasticizing, strong solvent, and low volatility, industrial-grade DEP is widely used in plastics processing, textile printing and dyeing, fragrances and flavors, paints and inks, alcohol denaturation, hygiene and insecticides, and adhesives. It is a classic plasticizer for cellulose acetate and other cellulose ester plastics (eyeglass frames, toothbrush handles, tool handles), a dyeing agent and dispersion medium for polyester carriers, a fragrance fixative solvent, an ethanol denaturant, and a traditional mosquito repellent ingredient.

Basic information : Chemical formula C12H14O4 (structural formula C6H4(COOC2H5)2, ortho-diethyl ester); molecular weight 222.24; CAS number 84-66-2; EINECS 201-550-6; aliases: diethyl phthalate, diethyl phthalate, diethyl phthalate, DEP, Ethyl phthalate, phthalic acid diethyl ester, 1,2-benzenedicarboxylic acid diethyl ester; trade names: Palatinol A, Kodaflex DEP, Placidol E, Unimoll DA, Anozol, Phthalol, Solvanol, etc.

Structurally , the DEP molecule consists of a central benzene ring and two ethyl ester groups (-COOC2H5): the benzene ring provides a rigid framework and aromaticity, while the two ethyl ester groups provide polarity and flexibility. The molecule is short and has no long-chain side groups. The process is mature, and it is one of the oldest phthalate family products in the world.

Physically , DEP is a clear, colorless, oily liquid, almost odorless (almost odorless): boiling point approximately 298℃ (760 mmHg); melting point approximately -40℃ (still liquid at low temperatures); flash point approximately 161℃ (closed cup); density approximately 1.12 g/cm³ (heavier than water at 25℃, in the range of 1.118-1.232); extremely low vapor pressure (almost non-volatile at room temperature); vapor density 7.7 (air=1); refractive index approximately 1.500-1.505; extremely low solubility in water (almost insoluble at 25℃), completely miscible with most organic solvents such as ethanol, ketones, esters, and aromatic hydrocarbons, and partially miscible with aliphatic hydrocarbons; moderate viscosity, neutral, and non-corrosive.

Chemically , DEP is an aromatic dicarboxylic acid ester: the ester bond (-COO-) can be hydrolyzed and saponified into phthalic acid and ethanol under acid or base catalysis, and is chemically inert under neutral conditions; the benzene ring is stable, has good heat resistance, and is not easily oxidized and discolored; the two ethyl ester groups give it excellent solvent ability and compatibility, and it can dissolve or plasticize polymers such as cellulose esters (cellulose acetate, etc.), polystyrene, and polyvinyl chloride, as well as disperse dyes, fragrances, resins, and waxes; its high boiling point and low vapor pressure result in low volatilization loss during processing and use, and it has both fragrance fixing and long-lasting plasticizing effects; its small molecular weight and relatively high migration make it easier for DEP to be released from products.

Why does DEP play these roles in industry? Its mechanism of action mainly includes the following:

Plasticizing mechanism : Short, flexible diester molecules insert into the polymer molecular chains, increasing the interchain spacing, weakening the interchain forces, and lowering the glass transition temperature, making rigid plastics more flexible; for cellulose esters containing hydroxyl groups, such as cellulose acetate, the ester groups can also form hydrogen bonds with the polymer, exhibiting excellent compatibility, which is the basis for its use as a plasticizer for cellulose esters and general-purpose plastics.

Strong solvent and compatibility mechanism : The two ethyl ester groups make it completely miscible with alcohols, ketones, esters, aromatic hydrocarbons, and a variety of resins, dyes, fragrances, and waxes. It can be used as a solvent and diluent for fragrances/dyes/resins, and it can also be well-complied with polymers to ensure uniform and stable formulations. This is the basis for its use as a fragrance solvent, paint and ink solvent, and industrial carrier.

Fiber swelling and carrier dyeing mechanism : DEP small molecules can penetrate into the amorphous region of hydrophobic synthetic fibers such as polyester, making the fibers swell and loose, reducing the temperature required for disperse dyeing and promoting the entry of dye molecules into the fiber interior, thus achieving normal pressure or low temperature carrier dyeing. This is the core function of polyester carrier dyeing agent and dispersion medium.

Low volatility fixative mechanism : Its high boiling point (about 298°C) and extremely low vapor pressure make it almost non-volatile in fragrance systems. It can delay the loss of volatile components in fragrances, prolong the fragrance time and round the aroma. At the same time, it is used as a high boiling point solvent and diluent, which is the basis for its use as a fragrance fixative and solvent.

Repellency and Mechanism of Action : DEP has a repellent and antifeedant effect on piercing-sucking insects such as mosquitoes. It can be used as a repellent active ingredient or carrier component to play a role in preventing bites. At the same time, its oil solubility makes it easy to be combined with carrier oils, alcohols, etc. to form formulations, which is the basis for its use as an insect repellent and insecticidal adjuvant.

 All Uses of Industrial Grade Diethyl Phthalate

1. Cellulose ester plasticizers (plastics industry)

Corresponding products: cellulose acetate eyeglass frames, toothbrush handles, combs, tool handles, pen barrels, buttons, films, sheets, automotive steering wheel trims, and household appliance housings, etc.

Why it works for this purpose: DEP is a classic plasticizer for cellulose ester plastics (especially cellulose acetate). Its ester groups form hydrogen bonds with the hydroxyl groups of cellulose esters, resulting in excellent compatibility. It can significantly reduce processing temperature and product brittleness, and give frames and handles a flexible and impact-resistant feel. At the same time, it has good transparency and is not easy to precipitate, making it a classic plasticizer for cellulose ester plastics.

2. General-purpose plasticizers (plastics industry)

Corresponding products: polystyrene products, PVC auxiliary plasticizing, toys, auto parts, daily necessities, food packaging films, flexible plastic parts, plastisol, etc.

Why it can be used for this purpose: DEP makes plastics more flexible and easier to process, and products include toothbrushes, automotive parts, tools, toys and food packaging (common products); as an auxiliary plasticizer, it can be used with other primary plasticizers to adjust hardness and processability. Its short-chain structure has high migration, making it suitable for daily necessities and industrial products where the requirements for exudation are not strict.

3. Polyester carrier dyeing agents and dispersion media (textile printing and dyeing industry)

Corresponding products: polyester fiber carrier dyeing agent, polyester/blended fabric dyeing, disperse dye carrier, printing paste auxiliary agent, dye bath swelling agent, yarn dyeing auxiliary agent, etc.

Why it can be used for this purpose: DEP small molecules penetrate into the amorphous region of polyester fiber, making it swollen and loose, reducing the dyeing temperature of disperse dyes, promoting dye penetration and fixation, and enabling carrier dyeing of polyester at normal pressure or low temperature. At the same time, it acts as a dispersion medium to help the dye disperse evenly, which is the core application of dispersion medium and dye carrier.

4. Fragrance fixatives and solvents in the fragrance and flavor industry

Corresponding products: perfumes, concentrated fragrance solutions, daily chemical fragrances, food fragrance solvents, fixatives, fragrance diluents, air freshener fragrances, soap fragrances, candle fragrances, etc.

Why it can be used in this way: DEP has a high boiling point and low volatility. As a fragrance fixative, it can delay the loss of volatile fragrance raw materials, prolong the fragrance and round the aroma. As a high boiling point solvent, it can dissolve difficult-to-dissolve fragrance raw materials and dilute concentrated fragrances. It is a fragrance component listed by IFRA and a commonly used solvent in the fragrance industry.

5. Coating and Ink Solvents (Coating/Ink Industry)

Corresponding products: nitrocellulose lacquer, alkyd lacquer, baking varnish, clear varnish, printing ink, screen printing ink, gravure ink, spray paint thinner, ink additives, paint plasticizers, etc.

Why it can be used for this purpose: DEP is used as a high-boiling-point solvent and plasticizer in coatings and inks. It dissolves resins, improves leveling and adhesion, and enhances the flexibility and gloss of the paint film. At the same time, it delays whitening and poor leveling caused by excessively rapid solvent evaporation. It is a commonly used additive in paint and ink formulations that combines dissolution and plasticization.

6. Ethanol denaturant (daily chemical/chemical industry)

Corresponding products: denatured alcohol, denatured ethanol for disinfection, cosmetic alcohol, industrial ethanol, cleaning alcohol, solvent-based cleaners, aerosol alcohol, etc.

Why it works for this purpose: DEP is a commonly used ethanol denaturant. When added to ethanol, it imparts a bitter taste and a distinctive odor, making it unsuitable for drinking, thus meeting the regulatory requirements for duty-free industrial alcohol. At the same time, it does not affect the solvent properties of ethanol, making it a classic application of ethanol denaturation.

7. Insect repellents and mosquito repellents

Corresponding products: mosquito repellent liquid, mosquito repellent spray, mosquito repellent lotion, insect repellent agent, sanitary insecticide adjuvant, insect repellent oil, outdoor insect repellent products, livestock insect repellent, etc.

Why it works for this purpose: DEP has a repellent effect on piercing-sucking insects such as mosquitoes. It is added to mosquito repellent preparations as a repellent active ingredient or adjuvant. Its oil solubility makes it easy to mix with carrier oils and alcohol. It is a common component of traditional mosquito repellents.

8. Adhesives and adhesion promoters (adhesive industry)

Corresponding products: solvent-based adhesives, pressure-sensitive adhesives, hot melt adhesive additives, sealants, label adhesives, shoe adhesives, wood adhesives, plastic adhesives, adhesion promoters, etc.

Why it can be used in this application: DEP acts as a solvent, plasticizer and adhesion promoter in adhesive systems, dissolves resins, adjusts viscosity and open time, improves film flexibility and adhesion, and improves wetting and adhesion to the surface of the bonded plastic. It is an important application of adhesives and adhesion/cohesion promoters.

9. Industrial solvents and oil-based carriers (fine chemicals)

Corresponding products: wax solvents, pigment carriers, resin diluents, oil-based formulation additives, cleaning agent components, polishing agent carriers, pesticide solvents, coating carriers, printing additives, etc.

Why it can be used in this application: DEP is miscible with most organic solvents and oily components, and can be used as a high-boiling-point solvent and diluent in industrial formulations to dissolve and disperse waxes, pigments, resins and oily raw materials, adjust viscosity and flowability, and its low volatility and heat resistance ensure the stability of the formulation during storage and processing.

Summarize

Industrial-grade diethyl phthalate (DEP, CAS 84-66-2) is a short-chain phthalate ester formed by the esterification of phthalic anhydride and ethanol. With its core strengths—a rigid benzene ring backbone and the strong solvent, plasticizer, and low volatility of diethyl esters—it serves industries such as plastics, textile printing and dyeing, fragrances and flavors, paints and inks, alcohol denaturation, insecticides, and adhesives. It is a classic plasticizer for cellulose acetate and general-purpose plastics, as well as a dyeing agent and dispersion medium for polyester carriers, a fragrance fixative solvent, an ethanol denaturant, and a traditional mosquito repellent. Understanding its molecular structure of "one benzene ring + two short ethyl esters" explains why it can simultaneously plasticize, dissolve, fix fragrance, and repel—this is precisely why it spans multiple industrial applications and is a versatile industrial oily ester.