PHTHALIC ANHYDRIDE- ▸ Plasticizers: Feedstock for phthalate ester plasticizers.
- ▸ Polyester resins: Building block for unsaturated polyester resins.
- ▸ Alkyd resins: Used in alkyd resin manufacture for coatings.
- ▸ Epoxy curing: Anhydride curing agent for epoxy resins.
- ▸ Dyes and pigments: Intermediate for dyes and pigments.
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
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Transport classification per the UN Model Regulations / 49 CFR 172.101 Hazardous Materials Table. Confirm against the grade-specific SDS (Section 14) before shipping.
Phthalic anhydride (PA) is a large-volume anhydride used as a heat-cure epoxy hardener and, in much larger volume, as the intermediate for plasticizers (phthalates), alkyd and unsaturated-polyester resins. Identity: CAS 85-44-9.
What it is
Phthalic anhydride (CAS 85-44-9) is a white flake/molten aromatic anhydride. It is a major chemical intermediate and also serves as an epoxy curing agent.
How it works
As an epoxy hardener its anhydride reacts with epoxy (catalyzed, on heating) to a high-temperature, electrically insulating, low-shrinkage network used in castings and electrical parts. Its dominant uses are as a feedstock for phthalate plasticizers, alkyd resins and unsaturated polyesters.
Applications
PA is used as a heat-cure epoxy/anhydride hardener (electrical castings) and as an intermediate for plasticizers, alkyd and unsaturated-polyester resins, and dyes. See the epoxy curing agents guide.
Forms, grades and handling
PA is supplied as flakes or molten in bags, drums and bulk. Properties are typical reference values; the Certificate of Analysis (CoA) for the lot you buy governs. Isocyanates are moisture-sensitive and require respiratory/skin precautions; handle per the current Safety Data Sheet (SDS). Each lot ships with CoA, TDS and SDS.
Bulk supply and RFQ
RawSource sources Phthalic Anhydride direct from producers in bulk, with CoA, TDS and SDS per lot. Tell us your binder system, cure schedule and the performance you need, and we will quote the right grade. See the epoxy curing agents guide.
Typical Properties
Typical reference values, not a specification; the Certificate of Analysis (CoA) for the lot governs.
| Property | Typical Value |
|---|---|
| Chemical / class | Anhydride epoxy hardener / intermediate |
| Function | Heat-cure epoxy hardener; plasticizer intermediate |
| CAS Number | 85-44-9 |
| Molecular Formula | C8H4O3 |
| Molecular Weight | 148.11 g/mol |
| Handling | Refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 201-607-5
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Frequently Asked Questions
What is phthalic anhydride (PA) used for?
Phthalic anhydride (PA, CAS 85-44-9) is mainly an intermediate for phthalate plasticizers, alkyd and unsaturated-polyester resins, and is also used as a heat-cure anhydride epoxy hardener for electrical castings.
How is bulk phthalic anhydride supplied and quoted?
RawSource supplies phthalic anhydride in bulk with CoA, TDS and SDS per lot. Pricing is quote-based on grade and volume; submit an RFQ with your binder system and cure schedule.
What is the REACH and TSCA regulatory status of Phthalic Anhydride (PA)?
Phthalic Anhydride (PA) (CAS 85-44-9) is subject to U.S. TSCA Inventory requirements; supplying it into the EU requires valid REACH registration ((EC) No 1907/2006). RawSource cannot verify a third-party supplier's registrations — buyers should require documented TSCA and REACH compliance for their jurisdiction and volume (EC 201-607-5).