BS ISO 22768:2017 pdf download – Rubber, raw — Determination of the glass transition temperature by differential scanning calorimetry (DSC)
1 Scope
This document specifies a method using a differential scanning calorimeter to determine the glass transition temperature of raw rubber.
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 1407, Rubber — Determination of solvent extract
ISO 11357-1:2016, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles
ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11357-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
glass transition
reversible change in an amorphous polymer, or in amorphous regions of a partially crystalline polymer,from (or to) a rubbery or viscous condition to (or from) a glassy or hard condition
glass transition temperature
T g
approximate midpoint of the temperature range over which the glass transition (3.1) takes place Note 1 to entry: For the purposes of this document, the glass transition temperature is defined as the point of
inflection of the DSC curve which has been obtained at a heating rate of 20 °C/min (see A.3).
4 Principle
The change in specific heat capacity of the rubber as a function of temperature under a specified inert atmosphere is measured using a differential scanning calorimeter (DSC). The glass transition temperature is determined from the curve thus produced.
5 Apparatus and materials
5.1 Differential scanning calorimeter, in accordance with ISO 11357-1:2016, 5.1.
The calorimeter should be operated in a room held at standard laboratory temperature. It should be protected from draughts, direct sunlight and sudden temperature changes.
5.2 Specimen pans (crucibles), in accordance with ISO 11357-1:2016, 5.2.
5.3 Gas supply, analytical grade, usually nitrogen or helium.
5.4 Balance, capable of measuring the specimen mass to an accuracy of ±0,000 1 g.
6 Test specimen
The test specimen shall be as representative as possible of the sample being examined and shall have a mass between 0,01 g and 0,02 g.
To determine T g of polymers, extract raw rubber in accordance with ISO 1407.
7 Conditioning
Condition the sample to be examined and the test specimen in accordance with ISO 23529.
8 Calibration
Calibrate the calorimeter according to the manufacturer’s instructions.
The use of suitable analytical grade substances is recommended to check the accuracy of the temperature scale. Ideally, substances whose melting points bracket the temperature range of interest should be chosen. n-Octane, n-heptane and cyclohexane have been found to be useful. Indium should be used if a higher temperature calibrant is required.
9 Procedure
9.1? Gas? flow? rate
The same inert gas flow rate with a tolerance of ±10 %, shall be used throughout the procedure. Flow rates between 10 ml/min and 100 ml/min have been found to be suitable.
9.2 Loading the test specimen
Determine the mass of the test specimen to an accuracy of ±0,001 g. The same nominal mass shall be used for all determinations. If possible, the specimen shall have a flat surface so as to give good thermal contact with the bottom of the pan.
NOTE 1 Intimate thermal contact between the test specimen and the bottom of the pan is essential for good repeatability.
Place the specimen in the pan, using tweezers and seal with a lid. Place the sealed pan in the calorimeter using tweezers.
Do not handle the test specimen or the pan with bare hands.
NOTE 2 Placing an empty pan with a lid as a reference helps to obtain stable DSC thermograms.BS ISO 22768 pdf download.