ISO 248-2:2019 download free.Rubber, raw — Determination of volatile-matter content — Part 2: Thermogravimetric methods using an automatic analyser with an infrared drying unit.
1 Scope
1.1 ISO 248-2 specifies two thermogravimetric methods for the determination of moisture and other volatile-matter content in raw rubbers by using an automatic analyser with an infrared drying unit.
1.2 These methods are applicable to the determination of volatile-matter content in synthetic rubbers (58k. NBR, BR, 1k. CR, Ilk. halogenated hR and EPDM) listed in Iso 1629 and to various forms of raw rubber, such as bale, block, chip, pellet, crumb, powder and sheet These methods might also be applicable to other raw rubbers only when the change In mass is proven to be due solely to loss of original volatile matter and not to rubber degradation.
1.3 The methods are not applicable to raw rubbers which need homogenizing as specified in ISO 1795.
1.4 The hot-mill method and the oven method specified In ISO 248-1 and the methods specified In this document might not give identical results. In cases of dispute, therefore, the oven method, procedure A, specified In ISO 248-1:2011, Is the referee method.
NOTE These methods can be useful for routine determinations, e.g. quality control, when the measurement conditions for the automatic analyser are fixed for a particular raw rubber or grade of raw rubbei
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.
ISO 248.1. Rubber, row — Determination of volatiIe-mauer content — Part 1: Hot-mIll method and oven method
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 Terms and definitions
No terms and definitions are listed in ISO 248-2.
The test result is taken to be the value from a single determination of the volatile-matter content.
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 predcflned 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-delined mass loss rate for method H) 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 Annix 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 IS g and weigh it to the nearest
1 mg. Operating the automatic analyser in accordance with the manufacturer’s instructions, set a drying temperature (prelrably between 100 ℃ and 120 ℃) and obtain a drying profile (X-axis: time in mm, V-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.ZJ.. 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 mg. Operating the automatic analyser In accordance with the manufacturer’s instructions, set a drying temperature (preferably between 100 ℃ and 120 ℃ ) and obtain a drying profile (X-axis: time, V-axis:
mass), From the drying profile (see FiguteZ), determine the mass loss rate at the point on the profile where the volatile-matter content corresponds to that determined in 82.1. 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 calcuiate this value automatically.
8.2.4 8.2.1 and either 82.2 or 8.23 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 diying 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.
8.33 When the drying time reaches the pre-delined value, drying stops automatically
8.3.6 The final mass (mit) of the test portion after drying Is measured and recorded automatically.
8.3.7 The volatile-matter content is calculated automatically in accordance with 8,5,
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 manufacturers Instructions. A general procedure is described in 8,4,2 to 8,4,8.
8.4.2 Input the drying temperature and the pre-deflned 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.
8.4.4 Take a test portion of about the same mass (within ±10 %) as was taken to determine the drying profile in 82.3 spread it on the sample tray as uniformly and quickly as possible and press the start button, The initial mass (m,J of the test portion before drying starts is measured and recorded automatically. Drying starts Immediately.
8.4.5 The mass of the test portion is continuously measured and recorded during drying, and the mass loss rate continuously calculated.
8.4.6 When the mass loss rate reaches the pre-deflnrd value, drying stops automatically.
8.4.7 The final mass (mit) of the test portion after drying is measured and recorded automatically.
8.4.8 The volatile-matter content is calculated automatically in accordance with U5.
8.5 Calculation of volatile-matter content
The volatile-matter content is calculated according to Formula (2):
9 Precision See Annex B.
10 Test report
The test report shall include the following information:
a) a reference to this document, i.e. ISO 248-2:2O9:
b) all details necessary for the identification of the sample of raw rubber tested; c) the method used (method A or method B);
d) full details ot the apparatus and measurement conditions;
e) the method, and associated procedure, in ISO 2481 used In determining the pre-detined drying time (method A) or pre-defined mass loss rate (method B);
f) details of any operation not specified in ISO 248-2 and of any optional operation;
g) any unusual features noted during the determination;
h) the test result;
i) the date of the test.