On the effect of pressure on the shear and elongational viscosities of polymer melts

Abstract

The effect of pressure and temperature on the shear and elongational deformation rateϪdependent viscosities has been experimentally investigated for several polymers (HDPE, LDPE, LLDPE, PP, PC, PMMA, and PS) on a capillary rheometer with a backpressure device. Pressure, ␤, and temperature, ␣, coefficients have been determined through simultaneous fitting of the shear and extensional viscosity data by the modified White-Metzner model. The dependence of ␤ and ␣ on temperature and pressure, respectively, was investigated and it has been found that simple relationships exist between pressure and temperature sensitivity coefficients for individual polymers.

Rheology of Polymers with Nanofillers

“…Evidently, the different sources of the rheological and PVT data could have introduced extra errors. Fortunately, Sedlacek et al [2004Sedlacek et al [ , 2005 reported η and PVT data for eight commercial polymers measured within the same range of T and P. The authors observed that Eq. (16.36) was not followed: At high P the viscosity data were below the master curve defined by low-pressure data.…”

The effect of powder characteristics on pressure sensitivity of powder injection moulding compounds

“…As introduced by Sedlacek et al [23], and described in detail in our previous paper [22], the rheometer was modified with an additional device generating backpressure, which causes increase of pressure actuating on the tested materials, Fig. 3.…”

On Pressure Affected Shear Viscosity of Poly(Lactic) Acid

“…The pressure dependent rheological behavior of PLA at temperature of 190qC was studied using a capillary rheometer, Göttfert Rheograph 2001, Germany equipped with back-pressure device. Back-pressure device designed at Polymer Centre of Tomas Bata University in Zlin, Czech Republic, and described in more details in the paper of Sedlacek et al [10] (its schematic diagram is shown in Figure 2) was used for modification of standard rheometer in order to generate pressure increase in tested polymer melts. Pressure level in polymer melt is controlled by the mean of an adjustable needle valve restricting outflow channel which is horizontally altered in a range of micro meter.…”

“…Furthermore an investigation of pressure affected viscosity employing modified rheometers and followed by evaluation of flow behavior by the help of pressure coefficient using some mathematical models could be employed. The pressure coefficient was incorporated into several nonlinear models such as Barus-Arrhenius combination [8][9], White-Metzner [10], Cross-Vogel [11], modified power law [12], WLF equation [13] and Carreau-Yasuda [1,14]. The accuracy and reliability of different techniques available for determination of pressure influence has been reported by Goubert et al [15] and H. E. Park et.…”

“…For this purpose, the standard capillary rheometer with back pressure device as present in Sedlacek at el. [10] was used for determination of pressure affected viscosity of PLA melt, while obtained flow curves were evaluated by means of the Carreau-Yasuda model.…”