Polymethacrylmethylimide

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Structural formula
PMMI structural element
General
Surname Polymethacrylmethylimide
CAS number 1883603-77-7
Monomers / partial structures Methacrylmethylimide
Type of polymer

Thermoplastic

properties
Physical state

firmly

density

unreinforced 1.21 g / cm 3

Thermal expansion coefficient

4.5 to 5.3 10 −5 K −1

safety instructions
GHS labeling of hazardous substances
no classification available
H and P phrases H: see above
P: see above
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Polymethacrylmethylimide ( abbreviation PMMI ) is a thermoplastic material . These are partially imidated methacrylic polymers such as. B. PMMA . The general empirical formula is [(C 9 H 13 NO 2 ) n (C 5 H 8 O 2 ) m ]. The imidation increases the modulus of elasticity, the viscosity, the refractive index and the water absorption. Was put on the market PMMI early 1990s by the company Rohm & Haas in the US under the name Kamax ® and Europe from Rohm under the name Pleximid ® .

history

As early as 1959, Röhm received a patent for the incorporation of nitrogen into the PMMA molecule, which led to the development of polymethacrylimide (trade name Rohacell ® ). Due to the higher water absorption compared to PMMA, however, the importance remained minor. However, since the higher glass temperature compensates for the interplay of stresses in the absorption and release of water, this interplay does not lead to premature component failure.

At the beginning of the 1990s, Pleximid was brought onto the market in Europe and given it a good chance of becoming a more important product, especially in the automotive and lighting industries.

Manufacturing

PMMI is obtained by reacting PMMA with methylamine in dispersion or the melt in a reactor, with methanol being produced as a by-product. In the process, imide ring structures form on the “side arms” of the PMMA macromolecule, which stiffen the macromolecule. The degree of conversion can be set in a targeted manner, so that molding compositions tailored to the particular application are obtained.

properties

Infrared spectrum from PMMI

PMMI is an amorphous, crystal-clear plastic. The light transmission at 3 mm thickness is approx. 90%. The refractive index increases linearly with the imide content, as does the modulus of elasticity. The heat resistance and water absorption also increase with the imide content. The toughness and weather resistance are comparable to conventional PMMA, the stress cracking resistance to aromatics and gasoline is better than that of PMMA, short-chain aliphatic hydrocarbons are critical.

processing

The processing takes place in the injection molding process , mass and mold temperature have to be selected approx. 40 ° C higher than with PMMA processing, since the more bulky PMMI molecule increases the melt viscosity .

use

PMMI is of particular interest for applications where transparency and heat resistance are important, e.g. B. Luminaire covers and light guides. It can be alloyed with other plastics such as PC , PVC , PA , SAN and thermoplastic polyesters and reinforced with glass or carbon fibers.

Trade names

Individual evidence

  1. ↑ a b Highly heat-resistant molding compound PLEXIMID, preliminary product information from Röhm 7/96.
  2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  3. ↑ Manfred Buck “Polymethacrylate” in Kunststoffe 80 (1990) 10, p. 1134.
  4. ↑ Homogeneous polymer compositions of polymethacryl-imide-polymers .
  5. ↑ Heinz Vetter " ® PLEXIMID - the magic formula for thermoplastic methacrylates with high heat resistance", brochure from Röhm.

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