BS ISO 6721-11:2019 download free.Plastics-Determination of dynamic mechanical properties.
Introduction
BS ISO 6721-11 covers the use of dynamic mechanical analysis (DMA) procedures, in the temperature scanning mode, to determine a value for the glass transition temperature of plastics. It provides an alternative procedure to the use of differential scanning calorimetry (DSC) (see ISO 11357-2)[1] for this measurement.
DMA is used to determine the variation of the storage modulus, loss modulus and loss factor as a function of temperature and frequency. From these data, a value for the glass transition temperature is determined. Many types of commercial equipment are available that use this technique, and, in principle, it applies to all the loading modes described in ISO 6721-1.
The procedures minimize errors due to thermal lag of the specimen, which varies with the heating rate used, through assuming the specimen temperature is given by the measured oven temperature[21. This eliminates the need for the temperature of the specimen to be measured directly by, for example, a thermocouple embedded in the specimen.
I Scope
BS ISO 6721-11 specifies methods for determining a value of the glass transition temperature (Ti) from the dynamic mechanical properties measured during a linear temperature scan under heating conditions. The glass transition temperature is an indicator of the transition from a hard and relatively brittle glassy state to a rubbery or viscous liquid state in an amorphous polymer or in amorphous regions of a partially crystalline polymer.
lisuaily referred to as dynamic mechanical analysis (DMA). the methods and their associated procedures can be applied to unreinlorced and filled polymers, barns, rubbers, adhesives and 1ibre reinforced plastics/composites. The methods are limited to materials that are Inherently stable above T1, I.e. amorphous materials that transform into a rubbery state or partially crystalline materials that keep their shape due to crystallinity.
Different modes (e.g. flexure, torsion, shear, compression, tension) of dynamic mechanical analysis can be applied, as appropriate, to the form of the source material.
Measured T5 values using instrumentation can vary as a result of material characteristics and/or the test set-up. The temperature sensor in a DMA instrument Is not in contact with the test specimen and therefore measures temperature of the environment surrounding tile specimen under test. The resulting data can vary with the heating rate applied. A procedure Is Included to take Into account the thermal Lag influencing the measured data.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (Including any amendments) applies.
15(1472. Plastics — Vocabulary
ISO 6fl1L Plastics — Determination of dynamic mechanical properties — I’lirt 1: General principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472. ISO 6721-1 and the following apply.
ISO and IEC maintain terminologicai databases for use in standardization at the following addresses:
— temperature of the Inflection point of the curve of storage modulus vs. temperature (see 12);
— temperature of the peak In the curve of loss (actor (tan delta) vs. temperature (see 13).
The test procedure described minimizes errors of the specimen temperature through due to the thermal lag. which varies with the heating rate used, assuming that the specimen temperature Is given by the measured oven temperature.
NOTE I The temperature o(the peak in the loss moduIu curve correlates quite well with the mIdpoint 01 the storage modulus curve drawn in linear scale. For many thermoplastic materials, this temperature measured at a frequency of I liz correlates well with the glass transition temperature determined as midpoint of step change-s obtained in DSC curves measured at 20 K/minlah.
NOTE 2 The temperature of the lnflecton point in the storage modulus curve depends on the numeric representation of the storage modulus. Using a linear scale results in inflection points that are similar to glass transition temperatures obtained by DS€ while plotting the storage modulus in loganthmic scale Yields signiiicantiy higher values.
NOTE 3 The temperature ol the peak In the curve of loss factor (tan delta) is Influenced by the decrease of the storage modulus and thus usually higher than that o[thc peak in the loss modulus curvc(,tl.
NOTE 4 In addition to the three methods above, the onset temperatures as defined by the Intercept of the tangents below Ta and the slopes in the curves of loss modulus or loss factor (tan delta) or the decrease in the storage modulus, respectively, arc also usedl4l.
5 Apparatus
5.1 Test equipment
The test equipment shall be capable of heating at rates from 1 K/mm to 10 K/mm over the required temperature range and mechanically oscillating the specimen at the reference frequency of 1 Hz or 10 Hz, respectively, The heating rate accuracy shall be ±5 % or better.
The instrument shall continuously monitor and record the sinusoidal load applied to the specimen, the corresponding sinusoidal displacement, and the phase angle as a (unction of the measured temperature, in order to determine the storage modulus, loss modulus and loss factor. The load and displacement capabilities of the equipment shall be sufficient for the specimens tested.
The temperature sensor should he positioned in the instrument as closely as possible to the sample under test, but ensuring it is not touching it.
The equipment shall be calibrated regularly, or when the testing mode or atmosphere Is changed or when the temperature sensor Is moved or changed.
5.2 Devices for measuring test specimen dimensions These shall be in accordance with ISO 6721-L
6 Test specimen
6.1 General
The test specimen shall be in accordance with ISO 6721.L
6.2 Shape and dimensions
The dimensions of the specimen shall be as required by the equipment for the selected test mode.
9.2.3 Method B — Raterndependent results
Undertake the procedure specified in method A but using a single temperature rate selected within the range specified (see 92.1). Plot the storage modulus, loss modulus and loss factor vs. temperature curve from the recorded data and determine T5 using one of the methods given in CLause4.
10 Expression of results
Report the values of Tj1. Tj, 7’5 or A determined according to 92.1. 922, or 92.3. as appropriate.
If required, report curves of storage and loss modulus and loss factor as well.
11 Precision
At the time of publication of this document, there are no precision data available.
12 Test report
The test report shall Include the Information required in IS672IL plus the following:
a) the method used (method A. offset method, or method B);
b) the test Irequency used;
c) a plot of the storage modulus, loss modulus and loss factor against temperature, with the analysis points Indicated;
d) all individual values of Tg1, T1or A as appropriate. together with, ii required, curves of storage and loss modulus and loss factor.