ISO/TC 61/SC 5/WG 9 - Rheology

This document specifies a procedure for the determination of an elasticity index based on measurements of the shear storage modulus using oscillatory rheometers, establishes general principles, and gives guidelines for performance of measurements. The elasticity index is applicable to all thermoplastics and viscoelastic materials for which the elastic behaviour is a crucial application property.

This document specifies the general principles of a method for determining the transient extensional viscosity of polymer melts. The procedure details the measurement of polymer melt specimens stretched uniaxially under conditions of constant strain rate and constant temperature. The method is capable of measuring the transient extensional viscosity of polymer melts at Hencky strain rates typically in the range 0,01 s–1 to 1 s–1, at Hencky strains up to approximately 4 and at temperatures up to approximately 250 °C (see NOTEs 1 and 2). It is suitable for measuring transient extensional viscosity values typically in the range from approximately 104 Pa⋅s to 107 Pa⋅s (see NOTE 3). NOTE 1  Hencky strains and strain rates are used (see Clause 3). NOTE 2  Values of strain, strain rate and temperature outside these limiting values can be attained. NOTE 3  The operating limit of an instrument, in terms of the lowest transient extensional viscosity values that can be measured, is due to a combination of factors, including the ability of the specimen to maintain its shape during testing and the resolution of the instrument.

This document specifies methods for determining the fluidity of plastics melts subjected to shear stresses at rates and temperatures approximating to those arising in plastics processing. Testing plastics melts in accordance with these methods is of great importance since the fluidity of plastics melts is generally not dependent solely on temperature, but also on other parameters; in particular shear rate and shear stress. The methods described in this document are useful for determining melt viscosities from 10 Pa∙s to 107 Pa∙s, depending on the measurement range of the pressure and/or force transducer and the mechanical and physical characteristics of the rheometer. The shear rates occurring in extrusion rheometers range from 1 s−1 to 106 s−1. Elongational effects at the die entrance cause extrudate swelling at the die exit. Methods for assessing extrudate swelling have also been included. The rheological techniques described are not limited to the characterization of wall-adhering thermoplastics melts only; for example, thermoplastics exhibiting "slip" effects[1][2] and thermosetting plastics can be included. However, the methods used for determining the shear rate and shear viscosity are invalid for materials which are not wall-adhering. Nevertheless, this document can be used to characterize the rheological behaviour of such fluids for a given geometry.

This document specifies a method for determining the drawing and break characteristics of molten plastics. The method involves the measurement of the force generated in deforming a molten filament under defined extrusion temperature and drawing conditions. Data is generated under non-isothermal and non-homogeneous deformation conditions. However, it is useful for the interpretation of polymer behaviour in extensional flow. The method is suitable for thermoplastics moulding and extrusion materials that can be extruded using a capillary extrusion rheometer, or an extruder with capillary rod die or other extrusion devices and have sufficient melt strength to be handled without difficulty. The method is applicable to chemically stable materials that produce a uniform extrudate free from heterogeneities, bubbles, unmelted impurities, etc. This method can provide information on — processability for all extrusion techniques, — the effect of mechanical and thermal history, and — the effect of chemical structure, such as branching, entanglements and molecular mass. This technique is one of a number of techniques that can be used to measure the extensional flow behaviour of a material. This method of measurement does not necessarily reproduce the drawing conditions to which thermoplastics are subjected to during their processing.

ISO 11443:2014 specifies methods for determining the fluidity of plastics melts subjected to shear stresses at rates and temperatures approximating to those arising in plastics processing. Testing plastics melts in accordance with these methods is necessary since the fluidity of plastics melts is generally not dependent solely on temperature, but also on other parameters, in particular shear rate and shear stress. The methods described in ISO 11443:2014 are useful for determining melt viscosities from 10 Pa∙s to 107 Pa∙s, depending on the measurement range of the pressure and/or force transducer and the mechanical and physical characteristics of the rheometer. The shear rates occurring in extrusion rheometers range from 1 s-1 to 106 s-1. Elongational effects at the die entrance cause extrudate swelling at the die exit. Methods for assessing extrudate swelling have also been included. The rheological techniques described are not limited to the characterization of wall-adhering thermoplastics melts only; for example, thermoplastics exhibiting "slip" effects and thermosetting plastics can be included. However, the methods used for determining the shear rate and shear viscosity are invalid for materials which are not wall-adhering. Nevertheless, ISO 11443:2014 can be used to characterize the rheological behaviour of such fluids for a given geometry.

ISO 1133-2:2011 specifies a procedure for the determination of the melt volume-flow rate (MVR) and melt mass-flow rate (MFR) of thermoplastic materials that exhibit a high rheological sensitivity to the time-temperature history experienced by the sample during the test and/or to moisture. It is possible that this method will not be appropriate for materials whose rheological behaviour is extremely affected during testing. MFR values can be determined by calculation from MVR measurements provided the melt density at the test temperature and pressure is known, or by measurement using a cutting device provided that the accuracy of the measurement is at least the same as that of the MVR measurement. The primary difference between ISO 1133-2:2011 and ISO 1133-1 is that ISO 1133-2:2011 specifies tighter tolerances on the temperature in the cylinder and on the time duration over which the material is subjected to that temperature. Thus the time-temperature history of the material is more tightly controlled and consequently, for materials that are likely to be affected by exposure to elevated temperatures, the variability of test results is reduced compared with whether the specifications of ISO 1133-1 were used. ISO 1133-2:2011 also provides information for preparation and handling of moisture sensitive materials that again are critical to obtaining repeatable, reproducible and accurate data. The test conditions for measurement of the MVR and MFR are often specified in the material standard. However, for those materials where there are no test conditions specified in the material standard, it is necessary for the test conditions to be agreed between the interested parties

ISO 20965:2005 specifies the general principles of a method for determining the transient extensional viscosity of polymer melts. The procedure details the measurement of polymer melt specimens stretched uniaxially under conditions of constant strain rate and constant temperature. The method is capable of measuring the transient extensional viscosity of polymer melts at Hencky strain rates typically in the range 0,01 s-1 to 1 s-1, at Hencky strains up to approximately 4 and at temperatures up to approximately 250 °C. It is suitable for measuring transient extensional viscosity values typically in the range from approximately 104 Pa.s to 107 Pa.s.

ISO 17744:2004 describes procedures for determining the specific volume of plastics as a function of temperature and pressure in both the molten and solid states. The standard 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. In the constant-pressure mode, the maximum heating and cooling rates permissible are restricted to 5 °C/min. By using these procedures, it is possible to obtain: pvT diagrams that represent the relationship which exists between pressure, specific volume and temperature for a given material; compressibility and volumetric thermal-expansion coefficients; information on first-order and glass transitions as a function of temperature and pressure.

ISO 16790:2005 specifies a method for determining the drawing and break characteristics of molten plastics. The method involves the measurement of the force generated in deforming a molten filament under defined extrusion temperature and drawing conditions. Data is generated under non-isothermal and non-homogeneous deformation conditions. However, it is useful for the interpretation of polymer behaviour in extensional flow. The method is suitable for thermoplastics moulding and extrusion materials that can be extruded using a capillary extrusion rheometer, or an extruder with capillary rod die or other extrusion devices, and have sufficient melt strength to be handled without difficulty. Such materials should be chemically stable and produce a uniform extrudate free from heterogeneities, bubbles, unmelted impurities, etc. This method may provide information on: processability for all extrusion techniques; the effect of mechanical and thermal history; the effect of chemical structure, such as branching, entanglements and molecular mass.

ISO 1133:2005 specifies two procedures for the determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastic materials under specified conditions of temperature and load. One is a mass-measurement method. The other is a displacement-measurement method. Normally, the test conditions for measurement of melt flow rate are specified in the material standard with a reference to ISO 1133. The test conditions normally used for thermoplastics are listed in annexes. These methods are in principle also applicable to thermoplastics for which the rheological behaviour is affected during the measurement by phenomena such as hydrolysis, condensation or crosslinking, but only if the effect is limited in extent and only if the repeatability and reproducibility are within an acceptable range. For materials which show significantly affected rheological behaviour during testing, these methods are not appropriate. In such cases, the use of the viscosity number in dilute solution, determined in accordance with the relevant part of ISO 1628, is recommended for characterization purposes.

ISO 11443:2005 specifies methods for determining the fluidity of plastics melts subjected to shear stresses at rates and temperatures approximating to those arising in plastics processing. Testing plastics melts in accordance with these methods is necessary since the fluidity of plastics melts is generally not dependent solely on temperature, but also on other parameters, in particular shear rate and shear stress. The methods described in this International Standard are useful for determining melt viscosities from 10 Pa·s to 107 Pa·s, depending on the measurement range of the pressure and/or force transducer and the mechanical and physical characteristics of the rheometer. The shear rates occurring in extrusion rheometers range from 1 s-1 to 106 s-1. Elongational effects at the die entrance cause extrudate swelling at the die exit. Methods for assessing extrudate swelling have also been included. The rheological techniques described are not limited to the characterization of wall-adhering thermoplastics melts only: for example, thermoplastics exhibiting 'slip' effects and thermosetting plastics can be included. However, the methods used for determining the shear rate and shear viscosity are invalid for materials which are not wall-adhering. Nevertheless, the standard can be used to characterize the rheological behaviour of such fluids for a given geometry.

Describes a method for the determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MFR) of thermoplastics under specified conditions of temperature and load. Does not apply to thermoplastics for which the rheological behaviour is affected by hydrolysis, condensation or crosslinking. Replaces the second edition.

Specifies methods for testing plastic melts subjected to shear stresses at rates and temperatures approximately to those arising in plastic processing. Testing plastic melts in accordance with these methods is necessary since their fluidity is generally not dependent solely on temperature, but also on other parameters, e.g. shear rate and shear stress. Methods for assessing extrudate swelling have also been included. The rheological techniques described are not limited to wall-adhering thermoplastic melts, the methods used for determining the shear rate and shear viscosity, however, are invalid for not wall-adhering materials.