BS ISO 11344:2016 pdf download

BS ISO 11344:2016 pdf download,Rubber, raw synthetic — Determination of the molecular- mass distribution of solution polymers by gel permeation chromatography
1 Scope
This International Standard describes a method for the determination of the molecular mass, expressed as polystyrene, and the molecular-mass distribution of polymers produced in solution which are completely soluble in tetrahydrofuran (THF) and which have a molecular-mass range from 5 × 10 3 to 1 × 10 6 . It is not the purpose of this International Standard to explain the theory of gel permeation chromatography.
2 Principle
The molecular components of a polymer are separated on the basis of macromolecule size on a gel permeation column. A known quantity of a dilute solution of the polymer is injected into a stream of solvent, which carries it through the column at a constant rate. The concentration of the separated molecular components in the solvent stream is measured by a suitable detector. Through the use of a calibration curve, both the number-average molecular mass (M n ) and mass-average molecular mass (M w ) of the material analysed can be determined from the retention time and the corresponding concentration.
3 General
3.1 Gel permeation chromatography (GPC), which is also known as size exclusion chromatography (SEC), is a particular type of liquid chromatography which allows the separation of the various components of a polymer based on molecular size. 3.2 The molecules of a polymer do not all have the same mass, but comprise a range of different masses. For this reason, the usual concept of molecular mass is not applicable to polymeric materials. Instead, different average molecular masses are determined as shown in Table 1.
4 Reagents and materials
4.1 Tetrahydrofuran (THF), with or without 2,6-di-tert-butyl-4-methylphenol (BHT), solvent for the mobile phase, analytical grade.
4.2 THF containing 2,6-di-tert-butyl-4-methylphenol, solvent for sample dissolution, analytical grade (THF containing BHT solution). The solution of 2,6-di-tert-butyl-4-methylphenol (also known as BHT, butylated hydroxytoluene) in THF is commercially available. For the purpose of this International Standard, the solution is called THF containing BHT. When it is difficult to find this solution in the market, the alternative can be obtained by adding 100 mg to 500 mg of BHT to 1 l of THF. Preparation of this solution is also effective when a noticeable peak is not obtained for BHT.
4.3 Set of certified polystyrene reference standards (minimum 10), with molecular masses in the range 5 × 10 2 to 1 × 10 7 (depending on the sample molecular-mass range) and a very narrow molecular- mass distribution (D < 1,10) (see Table 2 for an example of such a set, available from various chemical suppliers).