Polyvinyl acetals

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Polyvinyl acetal (R = H, alkyl) with a degree of acetalization of 75%.

Polyvinyl acetals form a group of plastics, the most important representatives of which are polyvinyl formal (PVFO), polyvinyl acetaldehyde and polyvinyl butyral (PVB). They are thermoplastics .

Manufacturing

Polyvinyl acetals are produced from polyvinyl alcohol by acetalization with an aldehyde with elimination of water , it being possible for the degree of acetalization to vary. In the polymer excerpt shown below, the degree of acetalization is 75% (75% of the hydroxyl groups in polyvinyl alcohol are converted into acetal groups, 25% are left over):

Production scheme for polyvinyl acetals with a degree of acetalization of 75%.

The tensile strength (N · mm −2 ) increases as the degree of acetalization increases. To a small extent, acetal formation can also take place between two polyvinyl alcohol chains, so that crosslinking occurs.

use

PVFO is used for wire insulation and lacquer for petrol cans. Among other things, PVB is used as an intermediate layer between the glass panes of windshields , as it is characterized by a splinter-binding effect and high tear resistance. PVB resins are also used as components of metal foil paints and stoving paints.

Individual evidence

  1. ^ Brockhaus ABC chemistry . VEB FA Brockhaus Verlag, Leipzig 1965, p. 1123.
  2. ^ A b Karlheinz Biederbick: Plastics . 4th edition, Vogel-Verlag, 1977, ISBN 3-8023-0010-6 , pp. 110-111.
  3. ↑ Sebastian Kotzenburg, Michael Maskus, Oskar Nuyken: Polymers - Synthesis, Properties and Applications . Springer Spectrum, 2014, ISBN 978-3-642-34772-6 , pp. 430-431.