Isophthalic acid
CAS Number
121-91-5
EC Number
204-506-4
Abbreviation
IPA
What is Isophthalic acid?
Isophthalic acid (CAS 121-91-5), commonly abbreviated as IPA in the polymer and coatings industry, is an aromatic dicarboxylic acid used as a monomer and polymer modifier.
Where is Isophthalic acid used?
- Unsaturated polyester resins: superior corrosion resistance
- Fiberglass-reinforced tanks, pipes and marine composites
- Alkyd and polyester resins: adhesion, gloss retention and durability
- PET modification: partial substitution of terephthalic acid reduces crystallization rate
- Adhesives and powder coatings: crosslinking co-monomer that controls cure behaviour
- It introduces flexibility and improved chemical resistance.
Good to know: Compared to its terephthalic acid counterpart, it reduces crystallinity in polyester and resin systems.
Commercial specifications
- Purity typically 99% or higher
- Packaging: 25 kg bags to bulk containers, fiber drums common for industrial quantities
Other Names (Synonyms)
meta-benzenedicarboxylic acid|m-benzenedicarboxylic acid|IPA|Benzene-1,3-dicarboxylic acid|1,3-Benzenedicarboxylic acid|m-Phthalic acid|Acide isophtalique|Kyselina isoftalova
What are the physical properties of Isophthalic acid?
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℃
Which trade and regulatory codes apply to Isophthalic acid?
HS Code 29173980
Storage Class 13 - Non Combustible Solids
WGK (Germany) 2