Isophthalic acid
CAS 121-91-5
EC 204-506-4
Formula C8H6O4
MW 166.13 g/mol
Organic Acids Plastics & PolymersCoatings, Adhesives, Sealants & ElastomersPrinting & PackagingTextile, Leather & PaperPersonal Care & Cosmetics Polymerization InitiationPreservation & BiocidepH Regulation & BufferingCatalysis
Description
Isophthalic acid (CAS 121-91-5, EC 204-506-4) is a benzene dicarboxylic acid also referenced as m-phthalic acid, 1,3-phthalic acid, and NSC 15310. It carries no assigned E-code and is classified under HS code 29173980 within the organic acids category.
In unsaturated polyester and alkyd resin production, isophthalic acid replaces orthophthalic acid to improve hydrolytic resistance and mechanical strength through its symmetrical meta-carboxyl geometry. It also functions as a pH buffer and catalyst in textile dyeing baths, where controlled acidity governs dye uptake rates and fiber penetration.
Isophthalic acid is supplied as a crystalline powder in technical and polymer grades, compliant with REACH registration requirements applicable to EU importers and downstream users. Standard packaging includes 25 kg bags and bulk quantities. Buyers should confirm grade specification against intended resin or coating formulation requirements prior to ordering.
In unsaturated polyester and alkyd resin production, isophthalic acid replaces orthophthalic acid to improve hydrolytic resistance and mechanical strength through its symmetrical meta-carboxyl geometry. It also functions as a pH buffer and catalyst in textile dyeing baths, where controlled acidity governs dye uptake rates and fiber penetration.
Isophthalic acid is supplied as a crystalline powder in technical and polymer grades, compliant with REACH registration requirements applicable to EU importers and downstream users. Standard packaging includes 25 kg bags and bulk quantities. Buyers should confirm grade specification against intended resin or coating formulation requirements prior to ordering.
Physical Properties
| Melting Point | 347 °C |
| Boiling Point | 100 °C |
| Density | 1.507 g/cm³ @ Temp: 20 °C |
| Appearance | whitetolightyellowcrytalpowe |
| Color | White to off-white |
| Form | Crystalline Powder |
| Water Solubility | 0.01 g/100 mL (25 ºC) |
| Vapor Pressure | 0Pa at 25℃ |
| Refractive Index | 1.5100 (estimate) |
| pH | 3.33(1 mM solution);2.76(10 mM solution);2.24(100 mM solution) |
| Log P | 1.66 at 25℃ |
Trade & Regulatory
| HS Code | 29173980 |
| Storage Class | 13 - Non Combustible Solids |
| WGK (Germany) | 2 |
Other Names
benzene-1,3-dicarboxylic acidIPAm-benzenedicarboxylic acidmeta-benzenedicarboxylic acidm-Phthalic acid
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Derivatives
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