ISO 248-2:2012 pdf download – Rubber, raw – Determination of volatile- matter content”
6 Sampling and preparation of test portion
Take a laboratory sample in accordance with the method specifed in ISO 1795, and then prepare a test portion of between 2 g and 15 g from the laboratory sample. The actual mass of the test portion will depend on the type of analyser, the expected volatile-matter content, and the form of the sample. For raw rubbers in bale form, the test portion shall be cut into small pieces of volume less than about 350 mm 3 (in the ideal case of a cubic piece, the length of a side should be about 7 mm). This operation shall be carried out as quickly as possible so as not to lose volatile matter. The test result is taken to be the value from a single determination of the volatile-matter content.
7.1 General
Either method A (which uses a pre-defned drying time) or method B (in which drying ends when the mass loss rate has decreased to a pre-defned level) can be chosen, provided the automatic analyser used offers the choice. The end point (the pre-defned drying time for method A or the pre-defned 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.
7.2.1 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 .
7.2.2 Then, for method A, take a test portion of between 2 g and 15 g and weigh it to the nearest 1 mg. 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 profle (X-axis: time in min, Y-axis: volatile matter lost, in %). From the drying profle (see Figure 1), determine the time at which the volatile-matter content determined by the automatic analyser is equal to that determined in 7.2.1. Take this drying time as the pre- defned drying time to be used in method A for this particular type or grade of rubber.
7.2.3 For method B, take a test portion of between 2 g and 15 g and weigh it to the nearest 1 mg. 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 profle (X-axis: time, Y-axis: mass). From the drying profle (see Figure 2), determine the mass loss rate at the point on the profle where the volatile-matter content corresponds to that determined in 7.2.1. Take this value of the mass loss rate as the end point 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.