A Novel Dilatometer for PVT Measurements of Polymers at High Cooling – and Shear Rates

Abstract

A novel dilatometer to investigate the specific volume of polymers as a function of the combined effect of pressure (100 MPa), temperature (300°C), cooling rate (100°C/s) and shear rate (200 l/s) was developed. The dilatometer consists of a pressure cell, which in design is a combination of a traditional “piston-die type” dilatometer and a Couette rheometer, embedded in a custom made frame, which allowed for scaling down to a “table-sized” machine that requires only standard laboratory supplies, like pressurized air and tap water, for operation and cooling. We implemented software for fully automated control of procedures to operate non-isothermal experiments with shear steps applied at predefined temperatures. The sample rings (m ≈ 65 mg) used in the dilatometer are made with a micro injection moulding machine. Experiments with two commercial isotactic Polypropylene (iPP) grades at low cooling rates, performed by two independent groups, were compared with measurements from a commercial confined fluids dilatometer showing small relative differences in the range of 0.03 to 0.3%. As an example, additional results of an isotactic polypropylene were chosen to show the profound influence of cooling rate and melt shearing on the evolution of specific volume.

The effect of pressure pulses on isotactic polypropylene crystallization

“…A unique dilatometer (IME Technologies) was used; detailed information on this apparatus, that was originally developed in our group, have already been described elsewhere [23,25,41,42]. The actual imposed cooling conditions are expressed in terms of the average cooling rate experienced by the samples in the temperature range in which the polymer solidifies, i.e., between 195 and 130°C.…”

Fast cooling of (non)-nucleated virgin and recycled poly(propylenes): Effect of processing conditions on structural and mechanical properties

“…A Pirouette pressurevolume-temperature (PVT) apparatus from IME Technologies was used in this study [44][45][46][47] can be achieved, respectively. The cooling profile in the 0.5 mm thick ring-shaped samples is independent of the distance of the location of interest to the cooling surface.…”

Using rheometry to determine nucleation density in a colored system containing a nucleating agent

“…A new type of dilatometer, the Pirouette (http://www.imetechnologies.nl), developed in our group (Forstner et al 2009;Van der Beek et al 2006), does allow for applying shear to the sample and thus for using the measured timedependent specific volume for our purpose: determining the nucleation density. However, in this paper, we will use a rheometer that first serves as flow device (with the possibility to vary the shear rate and the shear time) and, subsequently, as a mechanical spectrometer that measures the changing complex modulus due to the progressing crystallization process.…”