GB/T 13021-2023 Polyolefin pipes and fittings - Determination of carbon black content - Test method of alcination and pyrolysis
1 Scope
This document specifies test methods for the determination of the carbon black content of polyolefin compositions used in particular for the manufacture of pipes and fittings, and provides a basic specification for polyethylene pipes and fittings.
This document applies equally to the material for manufacture and to any material taken from a pipe or fitting.
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 11358-1, Plastics - Thermogravimetry (TG) of polymers - Part 1: General principles
3 Terms and definitions
There are no terms and definitions to be defined in this document.
4 Principle
It is possible to determine the carbon black content of polyolefin compositions by one of the following three methods:
——Method A: Pyrolysis of the sample at (550 ± 50) °C in a stream of nitrogen for 45 min followed by calcination at (900 ± 25) °C, by using an electrical tube furnace.
——Method B: Pyrolysis of the sample in a quartz crystal crucible with lid, by using a muffle furnace. According to the type of muffle furnace used there are two different procedures:
●Conventional muffle furnace (Method B1): pyrolysis from (325 ± 25) °C to (550 ± 25) °C at 15 °C/min and at (550 ± 25) °C for (10 ± 0.5) min followed by calcination at (900 ± 25) °C.
●Microwave muffle furnace (Method B2): pyrolysis at (520 ± 25) °C for (10 ± 0,5) min followed by calcination at (900 ± 25) °C.
——Method C: Pyrolysis of the sample at a constant rate in a thermogravimetric analyzer (TGA) under inert atmosphere at 800 °C followed by calcination under oxidizing atmosphere at 900 °C.
Note 1: Carbon black is decomposed from 500 °C in air or oxygen. Therefore, the loss observed between 500 °C and 700 °C in air or oxygen corresponds to the overall decomposition of the carbon black.
Note 2: If the composition contains, in addition to the carbon black, additives likely to decompose at 900 °C, for example ingredients such as calcium carbonate, the calculation can lead to an over-estimation of the carbon black content. If the ash yield is more than 1 %, further investigation can be required.
Calculate the carbon black content from the difference in mass before and after calcination and pyrolysis.
