The influence of molecular structure on physical aging kinetics

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Physical aging is a slow and gradual approach from a thermodynamic non-equilibrium to a thermodynamic equilibrium and this process affects material properties. Macroscopically, a gradual increase of the yield stress is observed which causes embrittlement of the material and leads ultimately to undesirable brittle failure.  Many studies have been conducted on the macroscopic connection between physical aging and yield kinetics, however the knowledge of the microscopic origins these processes is still lacking.  Knowledge of physical aging is very important for many applications, for example polymers used in any load bearing construction should not show any undesirable embrittlement.

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Flash-Differential Scanning Calorimetry (FDSC) is used to study the aging kinetics of polystyrene with different tacticties and polycarbonate  with introduction of various bulky groups. The benefit of using  FDSC is that it is possible to conduct experiments with very high heating and cooling rates which ensures an amorphous sample without the need to take crystallization into account and those rates are similar to real processing conditions of polymers (up to 1000 K/s).

Type of research: Experimental