Polyamide imide

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Amide group
Imide group

Polyamide- imides, also known as PAI for short , are polymers that contain both amide and imide groups.

application

After the pure polyimides, polyamide-imides with aromatic components in the polymer chain are the most thermally stable carbon-based polymers. In addition, it has a high level of chemical resistance and abrasion resistance. Polyamide-imides are used as heat-resistant electrical insulating varnishes and foils, coatings ( English overcoats ) of wire varnishes and generally as heat-resistant coatings. The permanent temperature resistance is over 220 ° C.

An important application is the polyamide- imide fiber Kermel, which was introduced on the market by Rhône-Poulenc in 1972 and is now produced by Kermel SA . This fiber belongs to the group of infusible, high-temperature or flame-resistant fibers with moderate mechanical-technical properties. The dry tear strength is 42 ± 4 cN / tex, the dry elongation at break 19 ± 2% and the modulus of elasticity between 240 and 440 cN / tex. A LOI of 30–32% indicates the high heat and flame resistance (heat-resistant up to 240 ° C). The decomposition temperature is higher than 380 ° C. The density is 1.34 g / cm³. At 3.4%, the moisture absorption is within the range of most synthetic fibers. The kerm fiber is spun-dyed and thus achieves a high degree of color fastness . There are 18 standard colors. Since the fiber only shrinks slightly in boiling water or hot air, items of clothing made from this fiber can be washed industrially without any problems. Kermel fiber is resistant to common solvents and acids. Due to its properties, it is suitable for protective clothing in various applications. The problem-free miscibility with other fibers is also important, especially with flame-retardant viscose fibers for textiles that come into contact with the skin.

Manufacturing

There is extensive patent literature on production, but in most cases heat-resistant polyamide-imides based on trimellitic acid derivatives , preferably trimellitic anhydride (TMA) and aromatic diamines and isocyanates, are described.

General structure of polymers with diphenylene methane as a chain extension

There are two manufacturing routes. Trimellitic anhydride is dissolved in the solvents mentioned below and reacted with 4,4'-diaminodiphenylmethane (MDA) in the presence of dehydrating agents or it is reacted with 4,4'-diphenylmethane diisocyanate (MDI), the isocyanate groups being split off with carbon dioxide form the amide or imide group. Usually, polyamide- imide is marketed as a solution in N- methylpyrrolidone (NMP), dimethylformamide (DMF) or dimethylacetamide (DMAc). Well-known manufacturers are Solvay and BASF .

Individual evidence

  1. ↑ Thomas Meyer to Capellen: Lexicon of tissues. 5th, fundamental revised and expanded edition. Deutscher Fachverlag, Frankfurt am Main 2015, ISBN 978-3-86641-258-3 , p. 229.
  2. ↑ Hans-J. Koslowski: Chemical fiber - Lexicon. 12th, expanded edition. Deutscher Fachverlag, Frankfurt am Main 2009, ISBN 978-3-87150-876-9 , p. 116.
  3. ↑ Walter Loy: Chemical fibers for technical textile products. 2nd, fundamental revised and expanded edition. Deutscher Fachverlag, Frankfurt am Main 2008, ISBN 978-3-86641-197-5 , p. 110.
  4. ↑ Brochure Kermel Solutions for Industry - Protection against heat, flame and electric arc. Website www.kermel.com. Retrieved on March 11, 2020 at: www.kermel.com/wp-content/uploads/2019/02/KermelBrochIndustry17_GB.pdf.
  5. ↑ Walter Loy: Chemical fibers for technical textile products. 2nd, fundamental revised and expanded edition. Deutscher Fachverlag, Frankfurt am Main 2008, ISBN 978-3-86641-197-5 , p. 280f.
  6. ↑ Walter Loy: The chemical fibers - their performance profile in clothing and home textiles. Fachverlag Schiele & Schön, Berlin 1997, ISBN 3-7949-0618-7 , p. 143.
  7. ↑ Patent DE10303635A1
  8. ↑ Patent DE4440409C2