BS ISO 6721-9:2019 pdf free download – Plastics一Determination of dynamic mechanical properties.
5.4 Pulse arrival time measuring equipment
This instrument shall be capable of measuring the time interval between two pulses, one from transducer drive unit and the other from receiving transducer to an accuracy of ± 0,5 Is.
NOTE The time interval will depend upon the distance between the transmitting and receiving transducers and the sonic wave velocity in the material.
5.5 Temperature measurement and control equipment
According to ISO 6721-1.
6 Test specimens
6.1 General
The test specimens shall be in accordance with Iso 6721-1.
6.2 Shape and dimensions
Test specimens in the form of a thin film or fibre are suitable. The dimensions are not critical, however, specimens 200 mm to 500 mm in length, 1 mm to 10 mm in width, and 0,1 mm to 1 mm in thickness or diameter are suitable.
6.3 Preparation
According to ISO 672 1-1.
7 Number of specimens
According to ISO 672 1-1.
8 Conditioning
According to ISO 672 1-1.
9 Procedure
9.1 Test atmosphere
According to ISO 672 1-1.
9.2 Mounting the specimen
Place a test specimen in the apparatus so that the received pulse has a suitable amplitude to determine its arrival time. Poor contact between the test specimen and the transducers makes the pulse energy inadequate for determining the sonic pulse propagation time.
For not rigid specimens, apply a small tension to the specimen to make it tight, but not stretched.
9.3 Performing the test
9.3.1 Position the transducers so that the longitudinal sonic pulse will be transmitted through the test specimen. The separation distance between them is determined so that the sonic pulse arrival time shall be at least 100 μs for good accuracy (See Note). Measure the separation distance of the transducers, L (m) to an accuracy of+ 0,5 %.
A.1 For the reasons outlined in Clause 11, the precision of this method is not known. However, Table A.1 gives repeatability data based on testing performed on identical test pieces in the same laboratory under the same conditions by the same operator using the same equipment within short intervals of time.
The densities of specimens were measured by use of a density gradient column in accordance with ISO 1183-2. The vL and E’ values reported are average values obtained from 10 measurements. It can be seen that a coefficient of variation of up to about 3 % can be expected within a particular laboratory.
A.2 When this method is used with certain materials, consideration should be given to various factors that can lead to a decrease in the repeatability of the measured values. Such factors include the following:
a) poor contact between the specimen and the transducers, which may give rise to a low amplitude of the sonic pulse and associated errors in determining the pulse propagation time;
b) anisotropy in the properties of the material, caused by molecular orientation, which will give rise to a dependence of the pulse propagation time on direction in the specimen;
c) the presence of filler or reinforcement in the material such that the distribution or orientation of the filler or reinforcement affects the pulse propagation time.
Since the properties of thermoplastics are time-dependent[l], the pulse propagation time and hence the dynamic modulus depend closely on the frequency of the sonic pulse used[Z]. It is therefore not possible to make accurate comparisons of results obtained using different frequencies.