ISO 248-2:2019 pdf free.Rubber, raw – Determination of volatil e-matter content -Thermogravimetric methods using an automatic analyser with an infrared drying unit.
8 Procedure
8.1 General
Either method A (which uses a pre-defined drying time) or method B (in which drying ends when the mass loss rate has decreased to a pre-defined level) can be chosen, provided the automatic analyser used offers the choice. The endpoint (the pre-defined drying time for method A or the pre-defined mass loss rate for method B) shall be determined for each of the two methods for each type or grade of rubber to be analysed.
Examples of test conditions are given in Annex A.
8.2 Determination of endpoints for method A and method B
8.2.1 First take a typical sample of the type or grade of rubber being analysed and determine its volatile-matter content in accordance with one of the methods described in ISO 248-1.
8.2.2 Then, for method A, take a test portion of between 2 g and 15 g and weigh it to the nearest
1 rng. Operating the automatic analyser in accordance with the manufacturer’s instructions, set a drying temperature (preferably between 100 °C and 120°C) and obtain a drying profile (X-axis: time in mm, Y-axis:
volatile matter lost, in %). From the drying profile (see Figure 1), determine the time at which the volatile- matter content determined by the automatic analyser is equal to that determined in 8.2.1. Take this drying time as the pre-defined drying time to be used in method A for this particular type or grade of rubber.
8.2.3 For method B, take a test portion of between 2 g and 15 g and weigh it to the nearest I rng. Operating the automatic analyser in accordance with the manufacturer’s instructions, set a drying temperature (preferably between 100 °C and 120 °C) and obtain a drying profile (X-axis: time, Y-axis:
mass). From the drying profile (see Figure 2), determine the mass loss rate at the point on the profile where the volatile-matter content corresponds to that determined in 8.2.1. Take this value of the mass loss rate as the endpoint for use in method B for this particular type or grade of rubber.
NOTE The automatic analyser can be programmed to calculate this value automatically.
8.2.4 8.2.1 and either 8.2.2 or 8.2.3 shall be performed individually for each type or grade of raw rubber to be analysed.
8.3.3 Position an empty sample tray in the designated place and set the balance to zero.
8.3.4 Take a test portion of about the same mass (within ±10 %) as was taken to determine the drying profile in 8.2.2. spread it on the sample tray as uniformly and quickly as possible and press the start button. The initial mass (mA) of the test portion before drying starts is measured and recorded automatically. Drying starts immediately.
8.3.5 When the drying time reaches the pre-defined value, drying stops automatically.
8.3.6 The final mass (mR) of the test portion after drying is measured and recorded automatically.
8.3.7 The volatile-matter content is calculated automatically in accordance with &S.
8.4 Method B (in which drying ends when the mass loss rate has decreased to a predefined level)
8.4.1 Operate the apparatus in accordance with the manufacturer’s instructions. A general procedure is described in 8,42 to 8.4,8.
8.4.2 Input the drying temperature and the pre-defined mass loss rate determined in 8.2.3 into the microprocessor of the apparatus.
8.4.3 Position an empty sample tray in the designated place and set the balance to zero.ISO 248-2 pdf download.