Polyaddition
Polyaddition (also known as addition polymerization) is a polyreaction that forms polymers ( plastics ) via individual, independent addition reactions . Polyaddition takes place as a step growth reaction via molecules with low degrees of polymerization , i.e. dimers , trimers and oligomers , which form new adducts with one another . Only when the conversion is almost complete does the polymer form, as in polycondensation and in contrast to chain polymerization . A polyaddition can only take place if theMonomers carry two or more functional groups . The products of the polyaddition are called polyadducts.
Polyaddition is not synonymous with the English term “addition polymerization”.
Example polyurethane (PUR)
A technically important polyaddition reaction is the production of polyurethanes (PUR). The starting products for the synthesis of polyurethanes are polyhydric isocyanates and polyhydric alcohols . Usually diisocyanates and diols are used as starting materials, e.g. B. 1,6-hexane diisocyanate (dihydric isocyanate) and 1,4-butanediol (dihydric alcohol):
- (n ≈ 40)
The curing of epoxy resins also takes place through polyaddition.
Web links
- Manufacture of plastics: polyaddition. Institute for Chemistry and Biochemistry Berlin-Dahlem
Individual evidence
- ↑ a b Entry on polyaddition . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.P04720 Version: 2.3.2.
- ↑ a b Entry on polyadditions. In: Römpp Online . Georg Thieme Verlag, accessed on June 21, 2014.
- ^ Wolfgang Kaiser : Synthetic chemistry for engineers. 4th edition. Carl Hanser, Munich 2016, p. 62.
- ↑ Erna Padelt: The basic knowledge of the engineer. 7th edition. Fachbuchverlag VEB, Leipzig 1968, p. 847.
- ^ MD Lechner, K. Gehrke and EH Nordmeier: Makromolekulare Chemie. 4th edition. Birkhäuser, Basel / Boston / Berlin 2010, ISBN 978-3-7643-8890-4 , pp. 138-139.