Industrial grade 99% Triphenyl Phosphate CAS 115-86-6 TPP

What is triphenyl phosphate? How does it work? What are its industrial applications?

1. What is Triphenyl phosphate?

Triphenyl phosphate, also known as triphenyl phosphate (TPP, TPhP, or Triphenyl ester of phosphoric acid), is an aryl phosphate ester formed by the esterification of phenol and phosphoric acid. It is one of the most widely used halogen-free, environmentally friendly organophosphorus flame retardants and plasticizers. Its chemical formula is usually written as:

C18H15O4P (OP(OC6H5)3, CAS No.: 115-86-6, EINECS No.: 204-112-2, molecular weight approx. 326.29)

It is a white, odorless crystalline powder (needle-shaped crystals) at room temperature, slightly hygroscopic, with a melting point of about 48-50℃ and a boiling point of about 370℃ (decomposes). It is insoluble in water but soluble in organic solvents such as ether, benzene, chloroform, and acetone. Industrially, it is prepared by esterification of phosphorus oxychloride (or phosphorus trichloride) with phenol.

Structurally, the TPP molecule consists of a central phosphate group connected to three benzene rings. The phosphate group is the core of its flame-retardant function (it decomposes upon heating to produce phosphorus-containing active species), and the three benzene rings give it rigidity and excellent compatibility, making it both a flame retardant and a plasticizer. It is a bifunctional phosphate ester that combines flame retardancy and plasticization.

Chemically, TPP is stable, resistant to hydrolysis, and has good compatibility with most polymer materials; it is low in toxicity, but has been confirmed to have endocrine-disrupting properties . It should be stored in a sealed, moisture-proof, and light-proof container.

Industrial-grade TPP refers to products designed for industrial applications such as PVC, engineering plastics, polyurethane foam, coatings, and hydraulic fluids, typically with a content of 99% or higher. Industrial-grade products place greater emphasis on the following indicators:

1. acid value

Acid value reflects the content of free acid, which affects product stability and the quality of downstream products, and must be controlled within a reasonable range.

2. Moisture

Moisture content affects product storage stability and processing performance, and must be strictly controlled.

3. Color (APHA)

Color affects the transparency and appearance of downstream products; the product must maintain a white crystalline appearance.

4. Ash and chlorine content

Ash content reflects the total amount of inorganic impurities, while chlorine content is a key indicator for halogen-free flame retardants and must be controlled within an extremely low range.

5. Volatile matter

Volatile matter reflects low-boiling-point impurities, which affect processing stability and product performance, and must be controlled within a reasonable range.

What are the uses of industrial-grade triphenyl phosphate?

Industrial-grade TPP, with its unique properties of "phosphorus-based flame retardancy + plasticization + lubrication," is used across plastics, rubber, coatings, cables, hydraulics, and chemicals industries.

1. PVC flame retardant plasticizer (core application in the plastics industry)

TPP is the most important flame-retardant plasticizer for PVC (polyvinyl chloride), possessing both flame-retardant and plasticizing functions. It is used in PVC sheets, films, wire and cable materials, artificial leather, and roofing materials, helping products meet flame-retardant requirements while maintaining flexibility.

Why it works for this purpose: A single TPP molecule simultaneously provides phosphorus-based flame retardancy (gas-phase free radical quenching + solid-phase charring) and phosphate ester plasticization (intercalation between chains to lower Tg). It achieves both flame retardancy and flexibility without the need for additional plasticizers. Its benzene ring structure provides good compatibility, making it economical and efficient.

2. Flame retardants for engineering plastics (core application in the field of engineering plastics)

TPP is used as a flame retardant plasticizer for engineering plastics such as PC/ABS, ABS, PC, PPO, HIPS, PP, and epoxy resin (EP), helping to improve the flame retardancy rating and processing flowability of engineering plastics. It is also used as a plasticizer and flame retardant for phenolic resin laminates, and is widely used in electronic and electrical housings and automotive parts.

Why it works for this purpose: TPP has a moderate melting point, good compatibility with engineering plastics, and can be uniformly dispersed at processing temperatures; its phosphorus-based halogen-free flame retardancy aligns with environmental trends, and its plasticizing effect can also reduce melt viscosity and improve the mold filling flowability of thin-walled electronic and electrical components.

3. Flame retardants for polyurethane foam (furniture and home furnishings industry)

TPP is used as a flame retardant in both flexible and rigid polyurethane foams, helping to reduce the flammability of sofas, mattresses, chairs, and insulation foams. It is widely used in furniture upholstery, children's products, and building insulation materials.

Why it works for this purpose:: Polyurethane flexible foam is porous, has a large specific surface area, and is highly flammable. TPP's gas-phase free radical quenching mechanism can interrupt the chain reaction in the early stages of combustion. It requires low dosage, produces low smoke and low toxicity, and does not affect the foam's resilience or feel.

4. Cellulose resin plasticizers (plastic coatings industry)

TPP is used as a plasticizer in cellulose acetate, nitrocellulose, and varnishes. It is also a non-flammable substitute for camphor in celluloid, helping to improve the flexibility and flame retardancy of cellulose. It is widely used in plastic products, varnishes, and coatings.

Why it works for this purpose: Celluloid and other nitrocellulose products are highly flammable. TPP can replace camphor to provide plasticizing effects and also provide phosphorus-based flame retardancy, achieving two benefits at once. Its benzene ring structure has good polar compatibility with cellulose, allowing it to be uniformly dispersed without precipitation.

5. Synthetic rubber softeners (rubber industry)

TPP is used as a softener and flame retardant for both natural and synthetic rubber, helping to improve rubber processing properties and the flame retardancy of finished products, serving the rubber products industry.

Why it works for this purpose: The polar phosphate groups of TPP weaken the intermolecular forces in rubber, improving flexibility and processability, while also providing phosphorus-based flame retardancy, making it suitable for rubber products requiring flame retardancy (such as flame-retardant sheets and cable rubber sheaths).

6. Flame-retardant wires and cables (cable industry)

TPP is used as a flame-retardant plasticizer in flame-retardant PVC wire and cable materials and cable sheaths, helping cables meet flame-retardant rating requirements. It is widely used in building wiring and electronic cables.

Why it works for this purpose: Wires and cables require both flame retardancy and flexibility, and TPP's dual-functional properties perfectly match this requirement. Its hydrolysis resistance and non-migration properties ensure stable flame-retardant performance of cables during long-term use and in high-temperature environments.

7. Flame-retardant hydraulic fluid (hydraulic field)

TPP is used as a component in flame-retardant hydraulic fluids to help prevent combustion under high temperature and pressure, and is widely used in hydraulic systems in mining, aviation, and industry.

Why it works for this purpose:Hydraulic fluids pose a risk of combustion and explosion under high temperature and pressure conditions. TPP's phosphorus-based flame retardancy improves the flash point and flame-retardant safety of the hydraulic fluid; simultaneously, its polar molecules can form adsorption films and tribochemical reaction films on metal surfaces, reducing wear and friction and protecting hydraulic components.

8. Flame retardant and plasticizing coatings (coatings industry)

TPP is used as a flame-retardant plasticizer in paints, coatings, and paint layers to help improve the flexibility and flame retardancy of coating films, serving the architectural and industrial coatings industries.

Why it works for this purpose:Coatings are prone to cracking and flammability after film formation. TPP intercalates between resin chains to improve film flexibility, reduce the tendency for internal stress cracking, and simultaneously provide phosphorus-based flame retardancy to improve the fire resistance rating of coatings. It also has good compatibility and does not affect gloss.

9. Adhesives and sealants (adhesive field)

TPP is used as a flame-retardant plasticizer in adhesives and sealants, helping to improve the flexibility and flame retardancy of adhesives, serving the construction, packaging, and electronics adhesive industries.

Why it works for this purpose:After curing, the adhesive layer tends to be hard and brittle. TPP lowers the glass transition temperature of the adhesive, improves flexibility and low-temperature performance, while providing flame retardancy, meeting the flame-retardant requirements of electronic adhesives and building sealants.

10. Fine chemical intermediates (chemical industry)

TPP is used as an intermediate in fine chemicals for the manufacture of trimethyl phosphate and other organophosphate esters, serving the phosphorus-based fine chemicals industry.

Why it works for this purpose: TPP can be exchanged with other alcohols through transesterification to produce various organophosphate esters. Its reactivity is moderate, and the byproduct (phenol) is easily separated and recovered, making it an ideal raw material for the preparation of phosphorus-based fine chemicals.

Summarize

Triphenyl phosphate (TPP, C18H15O4P, CAS No. 115-86-6, EINECS No. 204-112-2) is a white, odorless crystalline powder that is insoluble in water. It has become one of the most widely used halogen-free organophosphorus flame retardants and plasticizers due to its dual mechanisms of phosphorus-based flame retardancy (gas-phase free radical quenching + solid-phase char formation) and phosphate ester plasticization (interchain insertion to reduce Tg). In daily life, we encounter it through wires and cables, electronic devices, sofa foam, automotive interiors, flooring and roofing, and hydraulic equipment. In industry, TPP is widely used as a flame retardant plasticizer for PVC, a flame retardant for engineering plastics, a flame retardant for polyurethane foam, a plasticizer for cellulose resin, a softener for synthetic rubber, a flame retardant for wires and cables, a flame retardant hydraulic fluid, a flame retardant plasticizer for coatings, an adhesive sealant, and a fine chemical intermediate. It is a versatile flame retardant plasticizer that connects "phosphorus-based flame retardant chemistry" with "plastics, rubber, coatings, cables, hydraulics, and chemicals." At the same time, its endocrine-disrupting properties require attention to environmental compliance and green alternatives.