A Complete Guide to ISO 6964 Tiêu chuẩn: Core Criteria for Determining Carbon Black Content in Polyolefin Pipes and Fittings

In the polyolefin pipe and fitting industry, the addition amount of carbon black directly determines the aging resistance, service life and safety stability of products. As the core international standard for determining carbon black content in this field, ISO 6964 provides a unified and scientific technical basis for the quality control of relevant products worldwide. This article will comprehensively dissect the ISO 6964 standard from aspects such as standard overview, core technical content, revision history and changes, application scenarios and practical significance, helping industry practitioners, inspectors and relevant learners quickly grasp its core points.

TÔI. Overview of ISO 6964 Tiêu chuẩn: Positioning and Core Objectives

ISO 6964, fully named “Polyolefin pipes and fittings — Determination of carbon black content by calcination and pyrolysis — Test methods”, is a special determination standard formulated by the International Organization for Standardization (ISO) for carbon black content in polyolefin pipes, fittings and their raw materials. The current valid version is ISO 6964:2019. The core positioning of this standard is to “unify test methods, ensure data comparability and support quality control”, and its formulation and revision have always been in line with the needs of industry technological development and product quality.
As a key anti-aging additive in polyolefin products, carbon black can effectively absorb ultraviolet rays and delay material degradation. Especially for polyolefin pipes used in municipal water supply and drainage, gas transmission, agricultural irrigation and other outdoor or long-term service scenarios, whether the carbon black content meets the standard is directly related to the durability and safety of products — too low content will lead to easy aging and brittleness of pipes, while too high content may affect the mechanical properties and processing performance of pipes. Through clear and scientific test methods, ISO 6964 standardizes the determination process of carbon black content, ensures the consistency and credibility of test results among different laboratories and enterprises, and provides a unified benchmark for product quality inspection, raw material inspection and industry supervision.
It is worth noting that China has equivalently adopted this standard and converted it into the national standard GB/T 13021-2023 “Polyolefin pipes and fittings — Determination of carbon black content — Calcination and pyrolysis method”. This means that the testing requirements for relevant domestic products are fully in line with international standards, which not only facilitates Chinese polyolefin pipe enterprises to participate in international competition, but also better ensures the quality and safety of domestic market products.

II. Core Content of ISO 6964:2019: Detailed Explanation of Test Principles and Methods

The core content of ISO 6964:2019 is to specify three test methods for carbon black content, all based on the core principle of “calcination + pyrolysis” — that is, decomposing and volatilizing the polyolefin matrix through high-temperature treatment, retaining the carbon black component, then oxidizing and eliminating the carbon black through high-temperature calcination, and calculating the carbon black content according to the mass difference before and after treatment. The three methods are applicable to different scenarios and can be flexibly selected according to laboratory equipment conditions and sample characteristics. The specific details are as follows:
(TÔI) Core Test Principle
The core logic of all test methods is consistent: first, the polyolefin sample is pyrolyzed under the protection of inert gas (such as nitrogen), so that the polyolefin matrix (such as polyethylene and polypropylene) is decomposed into volatile substances and discharged, leaving only non-volatile carbon black and a small amount of ash; then switch to oxidizing atmosphere (or directly in air), completely oxidize and decompose the carbon black through high-temperature calcination, and finally calculate the accurate carbon black content in the sample according to the difference between “the mass of residue after pyrolysis” Và “the mass of remaining ash after calcination”.
Key Notes: Carbon black will gradually oxidize and decompose in an oxidizing atmosphere above 500℃, while the pyrolysis temperature of polyolefin matrix under the protection of inert gas can be controlled at about 500-600℃ to avoid premature oxidation of carbon black; if the sample contains additives such as calcium carbonate that do not decompose at 900℃, it will lead to high ash content. If the ash content exceeds 1%, further verification is required to ensure the accuracy of test results.
(II) Specific Requirements for the Three Test Methods
Phương pháp A: Tube Furnace Method (Basic Method)
This method is the basic method specified in the standard, applicable to various polyolefin pipes, fittings and raw materials, with relatively conventional operation. The core requirements are as follows:
•Reagents and Instruments: Dry nitrogen (oxygen content less than 20mg/kg, purified if necessary), quartz sample boat (length 50-60mm), tube furnace (length of heating section not less than 3 times the length of sample boat, length of combustion tube not less than 7 times the length of sample boat), balance with accuracy not less than 0.1mg, timer with accuracy not less than 1s, desiccator, vân vân. are required.
•Test Steps: Đầu tiên, calcine the quartz sample boat at 900℃±25℃ to constant weight (the difference between two weighings does not exceed 0.5mg); weigh a certain amount of sample (granular or chopped pipe sample) and place it in the sample boat, and condition it at 23℃±2℃ for not less than 24h; put the sample boat into the tube furnace, pass nitrogen flow for protection, and pyrolyze at 550℃±50℃ for 45min; then heat up to 900℃±25℃ for calcination until the carbon black is completely oxidized; weigh after cooling, and calculate the carbon black content through mass difference.
Method B: Muffle Furnace Method (Divided into B1 and B2)
This method is a new test method added in ISO 6964:2019, applicable to scenarios where the laboratory has a muffle furnace but no tube furnace, with simpler operation, divided into two subtypes:
•Method B1: Box-type Resistance Furnace (Traditional Muffle Furnace) Method: Put the sample into a covered quartz crucible, heat it from 325℃±25℃ to 550℃±25℃ at a certain heating rate, and keep it at this temperature for 10min±0.5min for pyrolysis; after pyrolysis, heat up to 900℃±25℃ for calcination until the carbon black is completely oxidized, and calculate the content through mass difference.
•Method B2: Microwave Muffle Furnace Method: Compared with the traditional muffle furnace, it has higher efficiency. Put the sample into a quartz crucible, pyrolyze at 520℃±25℃ for 10min±0.5min, then heat up to 900℃±25℃ for calcination, and the rest steps are the same as B1.
Method C: Thermogravimetric Analyzer Method (TGA Method)
This method is also a new method added in ISO 6964:2019, applicable to scenarios where the laboratory has a thermogravimetric analyzer, with high automation, small sample dosage and high test efficiency. The core requirements are as follows:
Put the sample into the thermogravimetric analyzer, pass inert gas (such as nitrogen), heat it to 800℃ at a specified rate to pyrolyze and volatilize the polyolefin matrix; then switch the inert gas to oxygen, heat up to 900℃ for calcination to completely oxidize the carbon black; the instrument records the mass change of the sample in real time, and directly calculates the carbon black content through the mass loss curve, without manually weighing the cooled residue, with smaller error and more convenient operation.
(III) Requirements for Test Reports
ISO 6964:2019 clearly stipulates that the test report shall include the following core information: sample information (tên, đặc điểm kỹ thuật, nguồn), test method (A/B1/B2/C), instrument model and parameters, test environment (nhiệt độ, humidity), sample conditioning status, weighing data, calculation process, carbon black content results (retaining appropriate significant figures), and necessary notes (such as abnormal ash content, special circumstances during the test, vân vân.) to ensure the traceability and completeness of the report.

III. Revision History of ISO 6964 Tiêu chuẩn: Upgrading from 1986 ĐẾN 2019

Since its release, the ISO 6964 standard has undergone several revisions. The core revision direction is to “meet the needs of industry technological development, improve test methods, and enhance test accuracy and applicability”. Its main revision history and key changes are as follows:
•1986 Version: The ISO 6964 standard was released for the first time, only specifying the tube furnace method (later Method A), mainly used for the determination of carbon black content in polyethylene pipes and fittings. The test method was relatively single, and the instrument requirements were relatively simple. At that time, China equivalently adopted this version and formulated the national standard GB/T 13021-1991 “Determination of carbon black content in polyethylene pipes and fittings (Phương pháp nhiệt kế)”, which was used for nearly 30 years without revision and gradually failed to meet the needs of industry development.
•2019 Version (Current Version): Aiming at the limitations of the 1986 version, combined with the progress of industry technology (such as the wide application of microwave muffle furnaces and thermogravimetric analyzers) and the increase of product types, a comprehensive revision was carried out. The core changes include: adding Method B (muffle furnace method, including traditional and microwave types) and Method C (thermogravimetric analyzer method) to enrich test options; refining instrument requirements, such as increasing the length requirements of tube furnace and quartz tube, and improving the accuracy requirements of balance and timer; improving the test process and adding sample conditioning steps; adjusting the calcination temperature of the tube furnace method (from 900℃±50℃ to 900℃±25℃) to improve test accuracy; clarifying the treatment method for abnormal ash content to reduce test errors; expanding the scope of application from only polyethylene pipes to all polyolefin pipes, fittings and their raw materials.
China has kept pace with the international revision, and released GB/T 13021-2023 TRONG 2023, which equivalently adopts ISO 6964:2019 and replaces GB/T 13021-1991 which has been used for nearly 30 years. In addition to minimal editorial changes (such as modifying the standard name), it fully retains the technical content of ISO 6964:2019, and adds a chapter on “Terms and Definitions” to better meet the usage habits of the domestic industry, realizing the full integration of domestic standards with international standards.

IV. Comparison between ISO 6964 and Other Relevant Standards

Hiện tại, there are many standards for carbon black content determination at home and abroad. With the advantages of “comprehensive methods and wide applicability”, ISO 6964:2019 has become the core standard in the polyolefin pipe industry. The key comparisons between it and other relevant standards at home and abroad are as follows:
•Comparison with Domestic Standards: GB/T 13021-2023 (equivalently adopting ISO 6964:2019) is a special method standard in the field of polyolefin pipes; GB/T 2951.41-2008 is mainly applicable to the determination of carbon black content in cable and optical cable insulation and sheath materials, including direct combustion method, thermogravimetric analyzer method, vân vân., which has different application scenarios from ISO 6964 and is used complementarily.
•Comparison with International Standards: ASTM D 1603-20 (American Standard) only specifies the tube furnace method, applicable to olefin plastics, with a single method; ASTM D 4218-20 (American Standard) only specifies the traditional muffle furnace method, applicable only to polyethylene polymers; while ISO 6964:2019 includes tube furnace method, muffle furnace method (two subtypes) and thermogravimetric analyzer method, applicable to all polyolefin pipes, fittings and their raw materials, with more comprehensive methods and wider applicability, and is currently the most recognized international standard for carbon black content determination in polyolefins.

V.. Application Scenarios and Practical Significance of ISO 6964

(TÔI) Core Application Scenarios
The application of ISO 6964 runs through the entire industrial chain of the polyolefin pipe industry, and the core scenarios include:
1.Raw Material Inspection: Polyolefin pipe manufacturers test the carbon black content of purchased polyethylene and polypropylene raw materials to ensure that the raw material quality meets the production requirements and control product quality from the source.
2.Production Process Control: During the production process, sample testing is carried out on semi-finished and finished pipes and fittings to monitor whether the carbon black addition amount is uniform and meets the product design standards, and adjust the production process in a timely manner.
3.Product Quality Acceptance: Factory inspection by enterprises, incoming inspection by dealers, and random inspection by third-party testing institutions all take ISO 6964 (or GB/T 13021-2023) as the basis to determine whether the carbon black content of products meets the standard, which is one of the core indicators for product qualification.
4.Industry Supervision and Arbitration: When market supervision departments conduct quality inspections on the polyolefin pipe market and quality disputes occur between enterprises, the methods specified in this standard are used as the basis for testing and arbitration to ensure the fairness and scientificity of supervision and arbitration.
5.Product R&D: When scientific research institutions and enterprise R&D departments develop new types of polyolefin pipes (such as anti-aging and high-strength pipes), they test the correlation between carbon black content and product performance through ISO 6964 to optimize formula design.
(II) Practical Significance
1.Standardizing Industry Order: The unified test method avoids result deviations caused by differences in test processes among different enterprises and laboratories, eliminates the possibility of “false testing” Và “data fraud”, and promotes the high-quality development of the industry.
2.Ensuring Product Safety: By strictly controlling the carbon black content, it ensures that polyolefin pipes have sufficient aging resistance, avoids safety accidents such as water leakage and gas leakage caused by pipe aging and brittleness, and guarantees the safety and stability of municipal construction and people’s livelihood projects.
3.Facilitating International Integration: China’s equivalent adoption of ISO 6964:2019 aligns the product testing standards of domestic enterprises with international standards, reduces the technical barriers for Chinese polyolefin pipe exports, and improves the international competitiveness of products.
4.Promoting Technological Progress: The newly added thermogravimetric analyzer method and microwave muffle furnace method in the standard guide enterprises and laboratories to upgrade testing equipment, improve testing efficiency and accuracy, and at the same time promote the optimization and upgrading of carbon black addition technology and polyolefin formulas in the industry.

VI. Notes on the Implementation of ISO 6964

To ensure the effective implementation of ISO 6964:2019 and improve the accuracy and reliability of test results, the following points should be noted in actual operation:
•Instrument Calibration: The instruments used for testing, such as balances, tube furnaces, muffle furnaces and thermogravimetric analyzers, should be calibrated regularly to ensure that the temperature accuracy and weighing accuracy meet the standard requirements, and avoid instrument errors affecting the test results.
•Sample Preparation: Samples should be taken uniformly; if they are pipes or fittings, they should be cut into small pieces (to avoid insufficient pyrolysis of large samples); sample conditioning should be carried out strictly in accordance with the requirements of 23℃±2℃ for not less than 24h to ensure that the samples are in a stable state.
•Gas Purity: The nitrogen used in Methods A and C should ensure purity, and the oxygen content should not exceed the standard requirements. Purification treatment is necessary if required to avoid premature oxidation of carbon black caused by oxygen, resulting in low test results.
•Ash Verification: If the ash content of the sample is found to exceed 1% after testing, further verification is required to check whether the sample contains non-decomposable additives such as calcium carbonate, so as to avoid ash interfering with the calculation of carbon black content.
•Personnel Training: Testers should be familiar with the standard requirements, master the operation procedures and precautions of the three test methods, and avoid test result deviations caused by operational errors (such as improper control of heating rate and insufficient calcination time).
•Environmental Control: The test environment should be kept clean and dry, with stable temperature and humidity, to avoid dust, water vapor and other factors affecting the sample quality and instrument operation.

VII. Phần kết luận

As the core international standard for determining carbon black content in polyolefin pipes and fittings, ISO 6964:2019 provides a unified benchmark for industry quality control through clear and scientific test principles, comprehensive test methods and strict operation requirements. Its revision and upgrading are in line with the needs of industry technological development, and the newly added test methods improve the testing efficiency and applicability. China’s equivalent adoption of this standard realizes the integration of domestic testing with international standards, which not only ensures the quality and safety of domestic products, but also helps Chinese polyolefin pipe enterprises participate in international competition.
For industry practitioners, proficiently mastering the core content and implementation points of ISO 6964:2019 and carrying out testing work in strict accordance with the standard requirements are the key to ensuring product quality and improving enterprise competitiveness; for scientific research institutions and industry supervision departments, this standard is also an important support for promoting technological progress and standardizing industry order. In the future, with the continuous development of polyolefin material technology, the ISO 6964 standard will continue to be optimized to further adapt to new industry needs and provide guarantee for the high-quality development of the global polyolefin pipe industry.

Our Product GA-1030 Carbon Black Content Tester meets this standard.

Máy kiểm tra hàm lượng than đen GA-1030

Tiêu chuẩn:
ISO 6964, GB/T13021, IEC 60811-4-1, GB/T 2951.41, JTG E50 T1165, ASTM D1603-94, GB/T13021-1991, vân vân.
Phương pháp thử nghiệm chung đối với vật liệu cách điện và vỏ bọc cho cáp và cáp quang
“Determination of Rubber Carbon Content — Pyrolysis Method”
Dụng cụ đo hàm lượng muội than của ống và phụ kiện Polyethylene (Phương pháp đo nhiệt lượng)
“Test Methods for Copper-Core Polyolefin Insulated Comprehensive Aluminum-Plastic Sheathed Municipal Communication Cables – Part 3: Test Methods for Mechanical and physical properties”
Polyetylen (Thể dục) piping systems for water supply – Part 2: Ống

Instrument Features
• Instrument appearance structure is beautiful, hoạt động rất đơn giản;
• The furnace door structure is open type, thuận tiện cho việc đặt mẫu và xác định vị trí tốt nhất của mẫu.
• 7 “LCD touch screen display, bầu không khí cao cấp
• High degree of automation, chỉ cần cài đặt nhiệt độ và thời gian làm nóng, thiết bị tự động làm nóng đến giá trị cài đặt;Hiển thị thời gian thực các đường cong nhiệt độ trên màn hình.
• High temperature control precision, phạm vi nhiệt độ lớn, độ đồng đều nhiệt độ lò cao;
• Excellent constant temperature function, và có thể thiết lập thời gian nhiệt độ không đổi, độ chính xác nhiệt độ không đổi cao;
• The instrument can set 30 nhóm thời gian gia nhiệt khác nhau, với nhiệt độ gia nhiệt khác nhau, tốc độ gia nhiệt và thời gian nhiệt độ không đổi.
• The parameter display is comprehensive, hiển thị số đã đặt, nhiệt độ lý thuyết, nhiệt độ thực tế, thời gian sưởi ấm (hoặc thời gian nhiệt độ không đổi);
• During the operation of the instrument, có thể kiểm tra các thông số đã thiết lập và thời gian gia nhiệt hoặc nhiệt độ không đổi.

Ứng dụng:
Thích hợp để xác định hàm lượng cacbon đen trong polyetylen, nhựa polypropylen và polybutene. Phép đo muội than thu được bằng phân tích trọng lượng của các mẫu bị phân hủy ở nhiệt độ cao dưới sự bảo vệ của nitơ. Dụng cụ này có ưu điểm là sử dụng thuận tiện, Hoạt động đơn giản, phương pháp đo lường chính xác, độ chính xác cao và mức độ tự động hóa cao.

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