Characterization of Crosslinked Polyurethanes and Relations of Structural Features to Some Applications

Karel Dusek

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic

Heyrovskeho nam. 2, CZ-162 06 Prague 6, Czechia

Tel: +420 296 809 297   Fax: +420 296 809 410
Email: dusek@imc.cas.cz

Biography 
 

Education and Training: Institute of Chemical Technology, Prague, 1949-1953, macromolecular chemistry/physical chemistry.

Ph.D. studies at Research Institute for Synthetic Resins, Pardubice, 1953-1957, Ph.D. degree obtained from Institute of Physical Chemistry, Czechoslovak Academy of Sciences

Career: 1957-1965, Research Institute for Synthetic Resins and Lacquers, Pardubice

1965-till now, Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences (CSAS),  (later Academy of Sciences of the Czech Republic (ASCR), Prague (1976-1990 head, Department of Polymer Physics,

1972—92, head, Laboratory/Department of Polymer Networks and Mechanical Properties), current principal Scientist and Project Coordinator

Abstract

Methods for characterization of build-up of linear and crosslinked polyurethane structures will be reviewed. Based on probabilistic or kinetic theories, the structure build-up can be described in terms of degree-of-polymerization or molecular-weight distribution and verified experimentally by SEC and MS. The evolution of molecular-weight distribution determines the viscosity increase.

For crosslinking systems, the gel point conversion or time are very important. Beyond the gel point, the sol fraction decrease and the gel fraction increase as the reaction proceeds. The postgel reactions are associated with decrease of molecular weight of the sol and increase in the concentration of elastically active network chains (effective crosslink density) in the gel.

These structural changes determine swelling and  equilibrium and viscoelastic mechanical properties of the network and also their application potential.

Very importance for properties is the possible presence of diluents during network formation. Their presence can cause reaction-induced phase separation and formation of inhomogeneous or porous structures.