Analysis of the pressure effect on the crystallization kinetics of polypropylene: Dilatometric measurements and thermal gradient modeling

International audienc

Analysis of the pressure effect on the crystallization kinetics of polypropylene: Dilatometric measurements and thermal gradient modeling

International audienceDilatometric measurements in isobaric cooling mode were performed to study the pressure effects on the crystallization kinetics of polypropylene (PP) up to 100 MPa. The experimental specific volume curves were analyzed by taking into account the thermal gradient that appears in the sample even for relatively low cooling rates. The Tait equation was used to describe the specific volume of the purely amorphous phase, and linear variations of the purely crystalline phase specific volume are considered. The relative crystal linity was modeled using the Nakamura equation, which is relevant for non-constant cooling rates. Considering an Avrami exponent of 3, the Nakamura rate constant was obtained first at atmospheric pressure and then generalized for higher pressures considering the equilibrium melting temperature variation. The obtained intrinsic specific volume was validated by computing the thermal gradient in the sample and comparing the calculated average specific volume to the experimental one

Study and modeling of heat transfer during the solidification of semi-crystalline polymers

International audienc

Performance of the Barrel Ring Imaging Cherenkov Counter of DELPHI

The Barrel Ring Imaging Cherenkov detector of the DELPHI experiment at LEP provides particle identification by the detection of the radiation emitted in UV transparent perfluorocarbons. We will present the principles of the operation of the detector together with a discussion of the automatized control of all the relevant physical parameters. The observed performances of the detector are very close to their design values. © 1994 IEE