ASTM D4440-08

This test method provides a simple means of characterizing the important rheological properties and viscosity of thermoplastic polymers using very small amounts of material (approximately 25 to 50 mm in diameter by 1 to 3 mm in thickness ... approximately 3 to 5 g). Data may be used for quality control, research and development, and establishment of optimum processing conditions.

Dynamic mechanical testing provides a sensitive method for determining molten polymer properties by measuring the elastic and loss moduli as a function of frequency, strain, temperature, or time. Plots of viscosity, storage, and loss moduli, and tan delta as a function of the aforementioned process parameters provide graphical representation indicative of molecular weight, molecular weight distribution, effects of chain branching, and melt-processability for specified conditions.

Values obtained in this test method can be used to assess the following:

Complex viscosity of the polymer melt as a function of dynamic oscillation,

Processing viscosity, minimum as well as changes in viscosity as a function of experimental parameters,

Effects of processing treatment,

Relative polymer behavioral properties, including viscosity and damping, and

Effects of formulation additives that might affect processability or performance.

Before proceeding with this test method, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM materials specification shall take precedence over those mentioned in the test method. If there are no relevant ASTM material specifications, then the default conditions apply.

1.1 This test method outlines the use of dynamic mechanical instrumentation in determining and reporting the rheological properties of thermoplastic resins and other types of molten polymers. It may be used as a method for determining the complex viscosity and other significant viscoelastic characteristics of such materials as a function of frequency, strain amplitude, temperature, and time. Such properties may be influenced by fillers and other additives.

1.2 It incorporates a laboratory test method for determining the relevant rheological properties of a polymer melt subjected to various oscillatory deformations on an instrument of the type commonly referred to as a mechanical or dynamic spectrometer.

1.3 This test method is intended to provide a means of determining the rheological properties of molten polymers, such as thermoplastics and thermoplastic elastomers over a range of temperatures by nonresonant, forced-vibration techniques. Plots of modulus, viscosity, and tan delta as a function of dynamic oscillation (frequency), strain amplitude, temperature, and time are indicative of the viscoelastic properties of a molten polymer.

1.4 This test method is valid for a wide range of frequencies, typically from 0.01 to 100 Hz.

1.5 This test method is intended for homogenous and heterogeneous molten polymeric systems and composite formulations containing chemical additives, including fillers, reinforcements, stabilizers, plasticizers, flame retardants, impact modifiers, processing aids, and other important chemical additives often incorporated into a polymeric system for specific functional properties, and which could affect the processability and functional performance. These polymeric material systems have molten viscosities typically less than 10⁶ Pa·s (10⁷ poise).

1.6 Apparent discrepancies may arise in results obtained under differing experimental conditions. Without changing the observed data, reporting in full (as described in this test method) the conditions under which the data was obtained may enable apparent differences observed in another study to be reconciled.

1.7 Test data obtained by this test method are relevant and appropriate for use in engineering design.

1.8 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Note 1—This test method is equivalent to ISO 6721, Part 10.