Effects of pressure on the compressibility and crystallization of fiber‐forming polymers

Abstract

The effects of pressure on the compressibility and crystallization of three fiber‐forming polymers, poly(tetramethylene terephthalate), nylon 66, and Qiana® nylon, have been studied. The Instron capillary rheometer was adapted as a high‐pressure dilatometer for all the high‐pressure experiments. The compressibility results reaffirmed that polymers are highly compressible, and their compressibilities are nonlinear at temperatures above the glass transition temperatures. Polymer melts show higher compressibility than do polymers in the solid state. The kinetics of crystallization of these polymer melts under high pressures were studied. Analysis of the data revealed low Avrami exponents at high pressures. It seems that the kinetics of crystallization of these polymers from the melt under high pressure are different from those at normal pressure. Crystallization temperatures of these polymers were also measured. The crystallization temperatures are considerably higher at higher pressures.

Equations of state for polyamide‐6 and its nanocomposites. 1. Fundamentals and the matrix

“…During the PVT tests, as T and P increase, the polymer anneals toward equilibrium. The maximum crystallization rate is expected at: T max % (T g þ T m )/2, with all three temperatures increasing with P. 53 The effect of pressure on X cryst is related to the crystal growth rate [54][55][56][57] :…”

Compression creep of molten poly (butylene terephthalate)

“…As may be observed, the volume deformation k is larger the higher the pressure and the lower the temperature. There are two plateau regions [5] (see also figures 4 and 5) in which the behavior seems to be viscoelastic (one at high temperature and low pressure corresponding to pure melt behavior, and another at low temperatures, high pressures, and long times, corresponding to pseudoequilibrium crystalline solid state) separated by a change of slope zone in which the isothermal rise of the pressure of the melt has as direct effect a rise in the melting temperature of th'e polymer T m to a new value T" such as the Tex v < T,~ and, therefore, crystallization from the melt begins [5,8].…”

“…The experimental procedure was tested with poly(ethylene terephthalate) data published elsewhere [5,8]. Results are shown in figure 1 at 541 K and 69.16 MPa.…”

“…The purpose of this paper is to describe the poly (butylene terephtalate) (PBT) melt compression creep behavior, since there are no published data about it to-date, though some information about the PBT melt compressibility (mainly oriented toward the elucidation of its crystallization kinetics) have been published [5].…”

Crystallization from the melt at high supercooling in finely dispersed polymer blends: DSC and rheological analysis

“…It should be pointed out that our experimental data are in good agreement with the literature. 12,13 From these experiments, it was possible to evaluate the effect of the temperature on the specific volume of the molten PBT (V mPBT ), the solidified PBT (V sPBT ) and the molten PE (V mPE ). The molten part of the specific volume can be generally fitted with an exponential, a polynomial or a linear expression.…”