BS ISO 17744:2025

Plastics. Determination of specific volume as a function of temperature and pressure, pvT diagram. Piston apparatus method. | Status: Current

1 Scope This document describes procedures for determining the specific volume of plastics as a function of temperature and pressure in both the molten and solid states. This document specifies the use of a piston-equipped apparatus in which the test sample, held in a measurement cell, is pressurized by means of the piston. Measurements under conditions of constant pressure or constant temperature can be made.

NOTE For the acquisition of data needed for processing design, the isobaric cooling method is found to be more useful, see ISO 17282. The result of this measurement cannot be used directly for injection-moulding simulation.

This document is used to obtain:

1. — pvT diagrams that represent the relationship which exists between pressure, specific volume and temperature for a given material;
2. — volumetric compressibility and volumetric thermal-expansion coefficients;
3. — information on first-order and glass transitions as a function of temperature and pressure.