Crystallization of isotactic polypropylene during step shear rate experiments is carried out in a plate-plate geometry by means of a Linkam shearing cell. The evolution of crystalline structures is observed during the tests at a fixed radial position. The samples are then analyzed by optical microscopy and the radial position at which a transition between the spherulitic and fibrillar morphology took place is measured. The analysis of the samples allows detecting the critical shear rate at which, after a given shearing time, the fibrillar morphology overcomes the spherulitic structure. With the aim of giving a quantitative description of the conditions for the formation of a fibrillar structure, two different models are applied: one based on molecular stretch, the other one relying on specific work.
FIBRILLAR MORPHOLOGY IN SHEAR-INDUCED CRYSTALLIZATION OF POLYPROPYLENE
PANTANI, Roberto;NAPPO , VALENTINA;DE SANTIS, FELICE;TITOMANLIO, Giuseppe
2014
Abstract
Crystallization of isotactic polypropylene during step shear rate experiments is carried out in a plate-plate geometry by means of a Linkam shearing cell. The evolution of crystalline structures is observed during the tests at a fixed radial position. The samples are then analyzed by optical microscopy and the radial position at which a transition between the spherulitic and fibrillar morphology took place is measured. The analysis of the samples allows detecting the critical shear rate at which, after a given shearing time, the fibrillar morphology overcomes the spherulitic structure. With the aim of giving a quantitative description of the conditions for the formation of a fibrillar structure, two different models are applied: one based on molecular stretch, the other one relying on specific work.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
