GB/T 7139-2023 Plastics - Vinyl chloride homopolymers and copolymers - Determination of chlorine content
WARNING — Persons using this document shall be familiar with normal laboratory practice. This document does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
1 Scope
This document specifies the methods for the determination of the chlorine content of homopolymers and copolymers of vinyl chloride.
This document is applicable to the determination of the chlorine content of homopolymers and copolymers of vinyl chloride, free from plasticizers or additives. It can also be used as a reference for the determination of chlorine content in other chlorine-containing polymers without plasticizers and additives.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 601 Chemical reagent - Preparations of reference titration solutions
GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test methods
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 9725-2007 Chemical reagent - General rule for potentiometric titration
3 Terms and definitions
No terms and definitions are listed in this document.
4 Method A - Combustion bomb
4.1 Principle
A test portion is oxidized with sodium peroxide followed by potentiometric titration of the resulting chlorides.
4.2 Reagents or materials
Unless otherwise specified, analytical reagents and Grade III water specified in GB/T 6682, or water of equivalent purity, shall be used for the analysis. Standard volumetric solutions, reagents, and products shall be prepared in accordance with the requirements of GB/T 601 and GB/T 603.
4.2.1 Sodium peroxide, granulated or powdered.
4.2.2 Nitric acid, concentrated.
4.2.3 Nitric acid solution: 125 g/L. Take 135 mL of nitric acid and dilute it to 1,000 mL.
4.2.4 Silver nitrate, standard volumetric solution, c(AgNO3)=0.1 mol/L.
4.2.5 Starch, sucrose or ethylene glycol, as combustion aids.
4.3 Apparatus
4.3.1 Drying oven, capable of being maintained at (50±2)°C or (75±2)°C.
4.3.2 Balance, to weigh to an accuracy of 0.1 mg.
4.3.3 Potentiometric titrator, with an accuracy of 2 mV; equipped with a type 216 silver indicator electrode and a type 217 double-salt bridge saturated calomel reference electrode.
4.3.4 Combustion bomb, gas or electrically fired. An example of a suitable gas-fired bomb is shown in Figure 1.
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Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Method A - Combustion bomb
5 Method B - Combustion flask method
6 Test report
Annex A (Informative) Comparison of structural changes between this document and ISO 1158: 1998 in clause/subclause number
Annex B (Informative) Technical differences between this document and ISO 1158: 1998 and their justifications
Annex C (Informative) Methods for placing sodium peroxide, starch or sucrose, and test portion
