HomeSolutionsNMP-free PAI

An excellent heat-resistant binder resin that conforms to REACH regulations and does not include restricted substances

Applicable business fields

Automotive parts manufacturers

Expected applications

Binders for sliding part paint

Key Benefits

• NMP-free
• High heat resistance
• Excellent durability

Polyamide-imide (PAI) resins are used in paint binders for sliding parts such as automotive compressors or engine pistons that require heat resistance. A movement of restriction under the EU REACH regulations on the use of N-Methyl-2-pyrrolidone (NMP), which is generally used as a solvent for this PAI resin, is underway. So far, as a material most suitable for automotive parts, we have aimed at the development of PAI in which the environment and safety are taken into account.

Showa Denko Materials’s Solution

No REACH restricted substances, reduction in countermeasure cost

For NMP, which is generally used as a solvent for PAI, there is a concern about reproductive toxicity, and NMP is handled as a restricted substance under the REACH regulations. When it is used, various restrictions (requirements), such as the obligation of controlling the amount of worker exposure to NMP, and investment in exhaust/collection equipment for reducing the amount of exposure, must be followed. Related materials such as DMAC* *and NMP, which are restricted by the REACH regulations, are not used for the new PAI resin we have developed or in any process including the production process. Therefore, various countermeasures for compliance with regulations are unnecessary. Furthermore, as the high heat resistance and mechanical properties, which are the characteristics of PAI resins, are the same as those of conventional materials, high-performance binder films applicable to high-temperature environments can be formed. (* Regulations as of April 2019)

REACH regulations


New PAI resin
New PAI resin(NMP not used)

Conventional PAI resin
(NMP used)

(Candidate list of substances for authorization)



(Candidate list of substances for restriction)




Strong and hard-to-peel coating is formed

Compared to epoxy, acryl, and urethane resins, which are widely used as binders for sliding part paint, PAI resin has high heat resistance (Tg ≧ 270℃) and mechanical property (elastic modulus ≧ 2.5 GPa), as well as excellent durability. Furthermore, thanks to the low linear expansion coefficient, delamination due to temperature changes is reduced.

Typical property comparison between PAI resin and resins used in binders for sliding part paint

Water-soluble (water-dilutable) type is available

Water-soluble type PAI resins that can be diluted with water or water-based materials are available. They are produced by controlling solubility in solutions, and can reduce the amount of volatilized solvent during heat curing. Furthermore, as paint and coating films absorb moisture and are resistant to whitening and solidification, it is easy to control the humidity in the painting environment.


Solvent included in the product

Solvent that can be added

Organic solvent type

Organic solvent

Organic solvent

Water-soluble type

Organic solvent + water

Organic solvent or water