Significance and Use
This test method provides a simple means of characterizing the cure behavior of thermosetting resins using very small amounts of material (fewer than 3 to 5 g). The data obtained may be used for quality control, research and development, and establishment of optimum processing conditions.
Dynamic mechanical testing provides a sensitive method for determining cure characteristics by measuring the elastic and loss moduli as a function of temperature or time, or both. Plots of cure behavior and tan delta of a material versus time provide graphical representation indicative of cure behavior under a specified time-temperature profile.
This test method can be used to assess the following:
5.3.1 Cure behavior, including rate of cure, gel, and cure time.
5.3.2 Processing behavior, as well as changes as a function of time/temperature.
Note 3—The presence of the substrate prevents an absolute measure, but allows relative measures of flow behavior during cure.
5.3.3 The effects of processing treatment.
5.3.4 Relative resin behavioral properties, including cure behavior and damping.
5.3.5 The effects of substrate types on cure.
Note 4—Due to the rigidity of a supporting braid, the gel time obtained from dynamic mechanical traces will be longer than actual gel time of the unsupported resin measured at the same frequency. This difference will be greater for composites having greater support-to-polymer rigidity ratios.3
5.3.6 Effects of formulation additives that might affect processability or performance.
For many materials, there may be a specification that requires the use of this test method, but with some procedural modifications that take precedence when adhering to the specification. Therefore, it is advisable to refer to that material specification before using this test method. Table 1 of Classification System D 4000 lists the ASTM materials standards that currently exist.
1.1 This test method covers the use of dynamic-mechanical-oscillation instrumentation for gathering and reporting the thermal advancement of cure behavior of thermosetting resin. It may be used for determining the cure properties of unsupported resins and resins supported on substrates and subjected to various oscillatory deformations. These deformations may be in shear or the dynamic compression of supported resins using a dynamic mechanical instrument.
1.2 This test method is intended to provide means for determining the cure behavior of supported and unsupported thermosetting resins over a range of temperatures by free vibration and resonant and nonresonant forced-vibration techniques, in accordance with Practice D 4065. Plots of modulus, cure behavior, tan delta, and damping index as a function of time/temperature are indicative of the thermal advancement or cure characteristics of a resin.
1.3 This test method is valid for a wide range of frequencies, typically from 0.01 to 100 Hz. However, it is strongly recommended that low-frequency test conditions, generally below 1.5 Hz, will generate more definitive cure-behavior information.
1.4 This test method is intended for resin/substrate composites that have an uncured effective elastic modulus in shear greater than 0.5 MPa.
1.5 Apparent discrepancies may arise in results obtained under differing experimental conditions. These apparent differences from results observed in another study can usually be reconciled, without changing the observed data, by reporting in full (as described in this test method) the conditions under which the data were obtained.
1.6 Due to possible instrumentation compliance, especially in the compressive mode, the data generated may indicate relative and not necessarily absolute property values.
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.
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. Specific precautionary statements are given in Note 5.
Note 2—There is no similar or equivalent ISO standard.