Continuous Two-Domain Equations of State for the Description of the Pressure-Specific Volume-Temperature Behavior of Polymers.

Jian Wang,Cemi Kahve,Jonathan Alms,Malte Röbig,Christian Hopmann,Tobias Hohlweck

doi:10.3390/polym12020409

Abstract

The two-domain Schmidt equation of state (EoS), which describes the pressure-specific volume–temperature (pvT) behavior of polymers in both the equilibrium molten/liquid state and non-equilibrium solid/glassy state, is often used in the simulation of polymer processing. However, this empirical model has a discontinuity problem and low fitting accuracy. This work derived a continuous two-domain pvT model with higher fitting accuracy compared with the Schmidt model. The cooling rate as an obvious influencing factor on the pvT behavior of polymers was also considered in the model. The interaction parameters of the equations were fitted with the experimental pvT data of an amorphous polymer, acrylonitrile-butadiene-styrene (ABS), and a semi-crystalline polymer, polypropylene (PP). The fitted results by the continuous two-domain EoS were in good agreement with the experimental data. The average absolute percentage deviations were 0.1% and 0.16% for the amorphous and semi-crystalline polymers, respectively. As a result, the present work provided a simple and useful model for the prediction of the specific volume of polymers as a function of temperature, pressure, and cooling rate.

Highlights

The prediction of the pressure-specific volume-temperature behavior of polymers is an important task, considering that it offers many highly promising applications in polymer physics and processing
In order the discontinuity of improve the traditional two-domain in the description of to thedeal pvTwith behavior of polymers problems and further the accuracy of the equation of state (EoS)
Behavior of polymers and further improve the accuracy of the models, continuous two-domain pressure-specific volume–temperature (pvT) model was derived in this work

Summary

Introduction

The prediction of the pressure-specific volume-temperature (pvT) behavior of polymers is an important task, considering that it offers many highly promising applications in polymer physics and processing. In injection molding, the predictions of shrinkage and warpage of the injection-molded parts are all based on pvT models [1,2,3,4]. The pvT model can be used to map process variables to quality variables so that the course of cavity pressure can be adjusted to the actual path of melt temperature [6,7,8,11]. Polymers in molten/liquid state can be considered as equilibrium, the pvT behavior of the polymers in molten/liquid state can be represented accurately by the equation of state (EoS). Various theories have been developed to describe the pvT properties of polymer solutions, including the cell model [12,13,14], the hole model [15], the lattice-fluid model [16], and the statistical–mechanical

Methods

Results

Conclusion