Overview
ISO 6964:2019 specifies standardized test methods for determining carbon black content in polyolefin compositions used for pipes and fittings, and provides a basic specification framework for polyethylene pipes and fittings. The standard applies both to raw material intended for manufacture and to samples taken from finished pipes or fittings. Carbon black content is measured by a combination of pyrolysis and calcination and reported as a percentage by mass.
Key topics and technical requirements
- Test principles: Carbon black content is calculated from the difference in mass before and after pyrolysis (inert atmosphere) and calcination (oxidizing atmosphere).
- Three validated methods:
- Method A - Electrical tube furnace: Pyrolysis at (550 ± 50) °C in nitrogen for 45 min followed by calcination at (900 ± 25) °C.
- Method B - Muffle furnace:
- B1 (conventional): Pyrolysis ramp from (325 ± 25) °C to (550 ± 25) °C at 15 °C/min, hold at 550 °C for (10 ± 0,5) min, then calcination at 900 °C.
- B2 (microwave): Pyrolysis at (520 ± 25) °C for (10 ± 0,5) min, then calcination at 900 °C.
- Method C - Thermogravimetric analyzer (TGA): Controlled-rate pyrolysis under inert gas up to 800 °C followed by oxidation at 900 °C.
- Sampling and repeatability: Three test portions are taken, and the arithmetic mean is reported rounded to two significant figures.
- Important notes:
- Carbon black decomposes in air/oxygen from about 500 °C - loss between 500 °C and 700 °C corresponds to carbon black decomposition.
- Presence of inorganic additives (e.g., calcium carbonate) can increase ash and lead to overestimation of carbon black; ash yields >1% may require further investigation.
- Reference standard: ISO 11358-1 (Thermogravimetry of polymers) is cited for TGA principles.
Applications
- Quality control and incoming material inspection for polyolefin and polyethylene pipe manufacturers.
- Product specification and certification to demonstrate compliance with material composition requirements.
- Failure analysis and forensic testing where carbon black content affects UV protection, thermal properties, or mechanical performance.
- R&D and formulation control for compounding and additive optimization in pipe grades.
Who uses this standard
- Pipe and fitting manufacturers, compounders, and converters
- Accredited testing laboratories and QA/QC personnel
- Materials engineers and polymer technologists
- Regulatory and standards bodies involved in plastic pipe safety and performance
Related standards
- ISO 11358-1 - Plastics - Thermogravimetry (TG) of polymers - Part 1: General principles
Keywords: ISO 6964:2019, carbon black content, polyolefin pipes, polyethylene pipes, calcination, pyrolysis, TGA, test method, pipe fittings, quality control.
