V. Brucato

An experimental methodology to study polymer crystallization under processing conditions. The influence of high cooling rates

Abstract A new experimental route for investigating polymer crystallization under very high cooling rates (up to 2000°C/s) is described. A complete and exhaustive description of the apparatus employed for preparing thin quenched samples (100– 200 μm thick) is reported, the cooling mechanism and the temperature distribution across sample thickness is also analysed, showing that the final structure is determined only by the thermal history imposed by the fast quench apparatus. Details concerning the characterization techniques used to probe the final structure are reported, including density measurements and wide angle X-ray diffraction patterns. Experimental results concerning isotactic polypropylene, polyethylenetherephthalate and polyamide 6 are reported, showing the reliability of this experimental route to assess not only a quantitative information but also a qualitative description of the crystallization behaviour of different classes of semi-crystalline polymers.

Measurement and modelling of the film casting process 1. Width distribution along draw direction

In the cast

Measurement and modelling of the film casting process: 2. Temperature distribution along draw direction

lm process a polymer melt is extruded through a slit die, stretched in air and cooled on a chill roll. During the path in air, while the melt cools, a reduction of both thickness and width takes place; obviously, thickness and width reductions are functions of draw ratio and stretching distance. Width distribution along the draw direction was measured on a iPP resin supplied by Montell as function of both 8ow rate and take up velocity. Final

Role of thermal history on quiescent cold crystallization of PET

lm width was found to decrease as take up velocity increase and, surprisingly, as extrusion 8ow rate increases. Thus draw ratio increase, attained by either lowering extrusion 8ow rate or by rising take up velocity, can lead to either enlargement or reduction of

Injection Molding of iPP

nal

Crystallization during fast cooling experiments, a novel apparatus for real time monitoring

lm width. The process of stretching in air was modelled with coupled one-dimensional equations of continuity and motion based on work of Barq, Haudin, Agassant, and Bourgin (Int. Poly. Process. 9 (1994) 350) the crystallinity generation term, according to the Nakamura non-isothermal model, was included in the equation of energy lumped along the thickness direction. The polymer was considered as a viscous 8uid (non-Newtonian), the apparent viscosity being function of temperature and strain rate. Furthermore, the e?ect of crystallinity on viscosity was somehow accounted for. The model equations were solved numerically. A modi

Polymer Solidification under Pressure and High Cooling Rates

ed expression of heat transfer coe@cient with respect to the model of Barq et al. (1994) was applied leading to a better agreement between model predictions and data with reference to width distribution along the draw direction and

Influence of “controlled processing conditions” on the solidification of iPP, PET and PA6

nal

Porous poly (L-lactic acid) scaffolds are optimal substrates for internal colonization by A6 mesoangioblasts and immunocytochemical analyses.

lm thickness. ? 2001 Elsevier Science Ltd. All rights reserved.

Polymeric scaffolds prepared via Thermally Induced Phase Separation (TIPS): tuning of structure and morphology

Abstract In the case film process a polymer melt is extruded through a slit die, stretched in air and cooled on a chill roll. During the path in air the melt cools and a reduction of both thickness and width takes place; obviously, temperature distribution, thickness and width reductions are function of draw ratio and stretching distance. Temperature distribution along the draw direction was measured as function of flow rate during film casting experiments performed with an iPP resin. A non-contacting method of measurement, based on a narrow-band IR pyrometer, was adopted. A good qualitative agreement is shown between experimental temperature data and predictions of a model accounting of radiation emissivity dependence upon film thickness. Differences are consistent with discrepancies of film thickness evolution along draw direction, indeed the model slightly over predicts both film thickness reduction and, parallel, temperature decrease along the draw direction.