Entanglement

A looping ( English entanglement ) is a physical networking of two or more polymer chains that arises by cross. Ver smart levies hold a plurality of movable polymer chains, ie amorphous chains above the glass transition together physically. Therefore entanglements are much weaker than chemical crosslinks and can both mikrobrownsche motion ( reptation , contour lengths fluctuation (engl. Contour length fluctuation can be also achieved as by external force)). One speaks of loosening .

However, since the microbrown movements also re-form entanglements, there is a dynamic equilibrium . This is described by the statistical mean in the molar mass between two entanglements, the entanglement molar mass : ${\displaystyle M_{e}}$

${\displaystyle M_{e}=\rho \cdot R\cdot T/G_{n}^{0}}$

in which

• ${\displaystyle \rho }$- density
• R - gas constant
• T - absolute temperature
• ${\displaystyle G_{n}^{0}}$- Plateau module of the stiffness of the material in the rubber-elastic plateau for unfilled thermoplastics .

The entanglement molar mass is a material constant which, to a good approximation, is independent of the branching structure , molar mass and molar mass distribution , but is increased by large numbers of branching points.

literature

• James E. Mark: Physical Properties of Polymers. Handbook . 2nd edition Springer, New York 2007, ISBN 978-0-387-31235-4 .