GB/T 33061.1-2025Plastics - Determination of dynamic mechanical properties - Part 1: General principles (English PDF)

5.1 Types

See the relevant parts of GB/T 33061 and Chapter 4.

5.2 Mechanical, electronic and recording system

See the relevant parts of GB/T 33061.

5.3 Temperature control chamber

The test specimen, fixtures and supports shall be enclosed in a temperature-controlled test chamber capable of providing the required test environment, including air or a suitable inert gas.

The temperature control chamber shall provide a sufficient temperature range for testing the material under test conditions (e.g. -100 °C ~ 300 °C). The chamber should be equipped with a programmable temperature control device.

The temperature inside the chamber shall be uniform and controlled within ±1 K along the length of the test specimen, and shall be measured at a position close to the specimen.

When a constant temperature program is used (see 9.5), the temperature during the test shall be maintained within ±1 K. When a constant heating (or cooling) rate is applied (see 9.4), the heating (or cooling) rate shall not exceed 120 K/h.

5.4 Gas

The purge gas shall be air or a suitable inert gas.

5.5 Temperature measuring device

A device for measuring the air temperature around the specimen, with an accuracy of at least ±0.5 °C. A temperature measuring device equipped with a low-inertia sensor should be used.

5.6 Specimen dimension measuring device

In the various parts of GB/T 33061, specimen dimensions used for modulus calculations shall be measured at room temperature. When determining the temperature dependence of the modulus, the effect of thermal expansion is not taken into account.

The measuring device used to determine specimen length, width and thickness (in accordance with GB/T 6672) shall have an accuracy of at least ±0.5% or ±0.05 mm (whichever is more accurate).

6.1 General requirements

The test results obtained by the test methods in this document are affected by both the dimensions of the test specimen and the uniformity of its physical state (such as crystallinity, orientation or internal stress). For test specimens of special materials, these factors should be considered when selecting dimensions and tolerances, specimen preparation methods and conditioning procedures.

Within the temperature range of measurement, the test specimen (homogeneous specimen, laminated strip or rod) shall have negligible shrinkage or distortion.

6.2 Dimensions

See the relevant parts of GB/T 33061.

6.3 Preparation

Test specimens, whether prepared from raw materials or finished products, shall be prepared in accordance with the relevant standards. They may be machined from compression-molded sheets [see GB/T 5471, GB/T 9352 and GB/T 27797 (all parts)] or from finished products (see GB/T 39812), or may be directly injection molded [see

GB/T 17037 (all parts)].

9.1 Test environment

The test temperature (or the variation of temperature with time), the gas (air or an inert gas) and the relative humidity shall be selected according to the type and purpose of the test.

9.2 Measurement of specimen cross-section

Before testing, the thickness and width of each test specimen shall be measured to an accuracy of ±0.5 % or ±0.05 mm (whichever is more accurate). Measurements shall be made at five points along the length of the specimen.

Specimens exhibiting obvious defects, such as sink marks or variations in thickness and/or width exceeding 3 % of the average value, shall be discarded. For specimens with non-uniform thickness, such as finished products, only the loss factor can be measured.

The procedure for measuring the dimensions of specimens of other shapes shall be agreed upon by the interested parties.

9.3 Specimen mounting

See the relevant parts of GB/T 33061.

9.4 Temperature-variation test

When determining the viscoelastic properties of a material, if temperature is the independent variable, the temperature of the test specimen shall be varied from the lowest temperature to the highest temperature. The frequency may be kept constant (Vibration Mode I), decreased freely with increasing temperature (Vibration Modes II and IV), or scanned (Vibration Mode III) (see Table 3).

The temperature of the test specimen shall be increased from the lowest temperature to the highest temperature either in constant temperature increments or at a sufficiently slow heating rate to ensure that the entire specimen reaches thermal equilibrium. The time required to reach equilibrium depends on the mass of the specimen and the apparatus used. A continuous heating rate of 1 °C/min ~ 2 °C/min or stepwise heating in increments of 2 °C ~ 5 °C (with a holding time of 3 min ~ 5 min at each step) should be selected. For Vibration Mode III, an interval of 10 min between successive steps is recommended.

The dynamic modulus of polymers is generally affected by the physical aging state of the specimen during testing. The aging state depends on the thermal history of the specimen and its time-dependent changes at temperatures below thetaalpha. The temperature thetaalpha is the temperature corresponding to the midpoint of the alpha-relaxation region. The alpha- relaxation is the highest-temperature mechanical relaxation and, for amorphous polymers, corresponds to the transition from the glassy state to the rubbery state.

Changes in the physical aging state affect molecular motion and consequently the response of the polymer to time-dependent loading or strain.

During measurements carried out while heating, the physical aging state of the specimen begins to change within the time scale of the test when the temperature approaches thetaalpha. This cooling produces a different physical aging state. Further measurements of the dynamic properties will therefore no longer reproduce the original measured values. Therefore, for high-precision measurements, the thermal history of the specimen and the heating rate used in the temperature-rise test shall be recorded.

9.5 Frequency-variation test

If vibration frequency is the independent variable, the test temperature shall be maintained at the required value. When measuring the viscoelastic properties, the vibration frequency of the test specimen shall be varied.

9.6 Dynamic strain-amplitude sweep test

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