M. Mierzwa et G. Floudas, Real-time crystallization and melting of poly(n-octadecyl methacrylate) induced by temperature and pressure - A dielectric spectroscopy investigation, IEEE DIELEC, 8(3), 2001, pp. 359-364
Citations number
25
Categorie Soggetti
Eletrical & Eletronics Engineeing
Journal title
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
We have studied the crystallization and melting of poly(n-octadecyl methacr
ylate) (PNODMA) by performing temperature and pressure jump experiments fro
m the melt to the final semicrystalline state. The evolution of the crystal
lization process is studied in real time by recording the changes in the di
electric spectrum. The single cu process in the melt upon crystallization l
ooses intensity and a new slower alpha ' process appears, reflecting the dy
namics of the restricted amorphous phase. The effect of pressure on increas
ing the crystallization temperature is stronger than the increase of the me
lt glass transition temperature, i.e. dT(c)/dP approximate to 2.3dT(g)(m)/d
P. The isothermal/isobaric crystallization experiments induced by T and P j
umps give rise, respectively, to stretched exponential and to typical nucle
ation and growth kinetics of the Avrami type. The different crystallization
kinetics induced by T and P reflect the 'paradoxical' situation of increas
ing mobility with increasing pressure. From the equivalence of the dynamics
we concluded that undercooling of 1K corresponds to an overpressure of 20
MPa, ie. deltaT/deltaP approximate to 50 K/GPa.