GB/T 3780.7-2025Carbon black — Part 7: Determination of pH value (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents" Drafting.

This document is Part 7 of GB/T 3780 "Carbon Black". GB/T 3780 "Carbon Black" has been published in the following parts.

— Part 1: Test method for iodine adsorption value;

— Part 2: Determination of oil absorption;

— Part 4: Determination of oil absorption value of compression specimen;

— Part 5: Determination of specific surface area - CTAB method;

— Part 6: Determination of tinting strength;

— Part 7: Determination of pH value;

— Part 8: Determination of loss on heating;

— Part 10.Determination of ash content;

— Part 12.Inspection of impurities;

— Part 14.Determination of sulfur content;

— Part 15.Determination of light transmittance of toluene extract;

— Part 17.Indirect determination of particle size - reflectivity method;

— Part 18.Identification methods in natural rubber (NR);

— Part 21.Determination of sieve residue - Water rinse method;

— Part 22.Calculation of process capability index using process control data;

— Part 23.Sampling and identification of carbon black or other ambient particles;

— Part 24.Determination of void volume;

— Part 25.Determination of carbon content;

— Part 26.Determination of carbon content in carbon black feed oil;

— Part 27.Determination of aggregate size distribution by disc centrifugal optical sedimentation measurement;

— Part 28.Determination of polycyclic aromatic hydrocarbons content;

— Part 29.Determination of solvent extractables;

— Part 30.Determination of high temperature volatiles by thermogravimetric method;

— Part 31.Determination of total hydrogen content.

This document replaces GB/T 3780.7-2016 "Carbon black - Part 7: Determination of pH value" and is consistent with GB/T 3780.7-2016.

In addition to structural adjustments and editorial changes, the main technical changes are as follows.

— Changed "Scope" (see Chapter 1, Chapter 1 of the 2016 edition);

— Deleted "Standard buffer solutions that meet the requirements of this part can be purchased commercially, or prepared according to GB/T 9724 or Appendix A" "Should comply with the provisions of GB/T 9724" was added (see 5.1, 3.1 of the 2016 edition);

— Added "calibration with a standard buffer solution of known pH value at the test temperature" (see 6.3);

— Added magnetic stirrer and magnetic stirring bar (see 6.11, 6.12);

— Added "When adding ethanol or acetone, the volume of water should be reduced to ensure the ratio of carbon black to water shown in Table 1".

The sample weight is specified (see 8.1.1, 7.1 of the 2016 edition);

— Changed the step of “calibrating the instrument with standard buffer solution” (see 8.1.6, 7.6 of the 2016 edition);

— Changed the method for testing pH value by boiling mud method (Method A) (see 8.1.7, 7.7 of the 2016 edition);

— Added the test steps and precision requirements of the ultrasonic slurry method (Method B) (see 8.2, 10.2);

— Deleted “standard buffer solution” (see Appendix A of the 2016 edition).

Please note that some of the contents of this document may involve patents. The issuing organization of this document does not assume the responsibility for identifying patents.

This document was proposed by the China Petroleum and Chemical Industry Federation.

This document is under the jurisdiction of the National Technical Committee on Rubber and Rubber Products of Standardization (SAC/TC35).

This document was drafted by: Longxing Chemical Co., Ltd., Zhonghao Heiyuan Chemical Research and Design Institute Co., Ltd., Iksda (Qingdao) Control Co., Ltd., Wuxi Shuangcheng Carbon Black Technology Co., Ltd., Qujing Zhongyi Fine Chemical Co., Ltd., Shanxi Anlun Chemical Co., Ltd. company.

The main drafters of this document are: Hou Hegang, Liu Jian, Chen Xiaoyan, Tang Guojun, Hu Xiaoli, Xue Yalei, Xiong Jinli, and Nie Suqing.

The previous versions of this document and the documents it replaces are as follows.

— First published as GB/T 3780.7-1983 in 1983, first revised in 1996;

— In the second revision in 2006, the content of GB/T 3781.4-1993 "Determination of pH value of acetylene black" was incorporated (The previous versions of GB/T 3781.4-1993 are: GB/T 3781.4-1983) and GB/T 7045-2003 "Color Determination of pH value of carbon black" (the previous versions of GB/T 7045-2003 are: GB/T 7045- 1986, GB/T 7045-1993); revised for the third time in 2016;

— This is the fourth revision.

Introduction

Carbon black is a type of carbon element that exists in the form of nano-sized particles and amorphous carbon. It is formed by organic matter (natural gas, heavy oil, fuel oil, etc.) in the air.

Carbon black is a product obtained by incomplete combustion or thermal decomposition under conditions of insufficient gas.

Rice material, is listed as one of the 25 basic chemical products and fine chemical products in the international chemical industry. Carbon black is an indispensable It uses a small amount of reinforcing raw materials and can give rubber products a series of excellent properties.

In the carbon black standardization system, the three major characteristic indicators of carbon black, namely, specific surface area, structure and surface activity, are the main indicators for determining the reinforcing capacity of carbon black.

Indicators, focusing on the performance of carbon black, GB/T 3780 "Carbon Black" is intended to be divided into the following parts.

— Part 1: Test method for iodine absorption value. Applicable to test the surface area of carbon black. The surface area of carbon black will affect the absorption of carbon black in rubber.

dispersion, especially related to tire wear resistance.

— Part 2: Determination of oil absorption value. Applicable to test the structure of carbon black. The structure is a unique property of carbon black. Carbon black with high structure can To provide better reinforcement for tires, the structures tested in this section are the primary and secondary structures of carbon black.

It is the structure formed by the agglomeration of the smallest unit aggregates of carbon black.

— Part 4: Determination of oil absorption value of compression specimen. The oil absorption value of compression specimen of carbon black is used to test the primary structure of carbon black.

The structural parameters of the smallest unit aggregate of carbon black, only the primary structure of carbon black can have a reinforcing effect on the tire.

— Part 5: Determination of specific surface area - CTAB method. Applicable to test the surface area of carbon black, which is the surface area of carbon black and rubber.

The effective area that can produce cross-linking.

— Part 6: Determination of tinting strength. Applicable to testing the particle size distribution of carbon black, which can determine its effect on rubber.

Reinforcement effect. Carbon black with high tinting strength value has a more concentrated particle size distribution, which can greatly improve the reinforcing effect of carbon black.

— Part 7: Determination of pH value. Applicable to testing the pH value of carbon black, which affects the vulcanization speed of rubber products.

degree and vulcanization time.

— Part 8: Determination of heating loss. Applicable to the determination of low temperature volatiles such as moisture in carbon black.

When the temperature is high, the rubber products will produce bubbles due to the vulcanization of low-temperature volatiles such as water at high temperatures, affecting the performance of rubber products such as tires. quality.

— Part 10.Determination of ash content. A high ash content in carbon black will affect the purity of carbon black and reduce the carbon content in carbon black.

— Part 12.Inspection of impurities. Impurities in carbon black are foreign matter introduced during the production process. They are large in size and are present in rubber products.

If it exists, local cracks will easily appear at the location where it exists, which may cause a tire blowout.

— Part 14.Determination of sulfur content. Rubber products need to be vulcanized with sulfur. The high sulfur content of carbon black will affect the sulfur content of rubber products. Speed.

— Part 15.Determination of transmittance of toluene extract. The carbon black toluene extract involved in this part comes from hydrocarbons that are not completely pyrolyzed.

The tar-like substance attached to the surface of carbon black can be extracted by some solvents such as toluene.

Benzene dissolves and extracts low molecular weight volatiles on the surface of carbon black. The lower the transmittance of the toluene solution, the higher the content of low molecular weight volatiles in the carbon black.

High, will affect the surface gloss of rubber products.

— Part 17.Indirect determination of particle size - reflectivity method. This part is an indirect test of the particle size of carbon black, with electron microscopy The carbon black particle size is corresponding to the carbon black particle size tested by the method, which can quickly test the particle size of carbon black and determine its effect on rubber products.

— Part 18.Identification method in natural rubber (NR). Applicable to testing the physical and mechanical properties of carbon black in rubber.

The method is to mix carbon black with rubber, vulcanize it, and then test the physical and mechanical properties of the rubber after carbon black reinforcement according to GB/T 528.

— Part 21.Determination of sieve residue - Water flushing method. The sieve residue in carbon black is generated during the production process and its volume is greater than The substance with a diameter of 45µm is small in size. When it exists in rubber products, it will easily cause local cracks to appear, causing rubber The product breaks prematurely.

— Part 22.Calculation of process capability index using process control data. This part is applicable to the guidance of carbon black production process control.

— Part 23.Sampling and identification of carbon black or other environmental particles. This part specifies the sampling and identification of carbon black in the carbon black production environment.

The sampling and identification of fugitive particles are suitable for testing the pollution of carbon black to the environment.

— Part 24.Determination of void volume. This part is the same as Part 4 and is a method for testing the primary structure of carbon black. This method can Quickly test the structure of carbon black.

— Part 25.Determination of carbon content in carbon black. This part is to place the combustion boat containing the weighed sample in a 1350 ° C tubular The combustion is complete in the furnace, and the carbon is oxidized into carbon dioxide. The carbon dioxide concentration is measured with a carbon analyzer to determine its carbon content.

Together with Part 26, it constitutes the test method for carbon emissions from carbon black production process, which is used to formulate carbon emission control methods for carbon black production process. Prepare standards.

— Part 26.Determination of carbon content in carbon black feedstock oil. This part uses the same method as Part 25 to test carbon black feedstock.

Carbon content in oil, together with Part 25, constitutes the test method for carbon emissions from carbon black production.

Prepare for the implementation of carbon emission control standards.

— Part 27.Determination of aggregate size distribution by disk centrifugal optical sedimentation measurement. This part adopts the physical centrifugal method to measure Test the particle size distribution of carbon black, the same as Part 6, by testing the particle size distribution of carbon black to determine its reinforcing effect on rubber.

— Part 28.Determination of polycyclic aromatic hydrocarbons content. The source of polycyclic aromatic hydrocarbons in carbon black is the same as that in Part 15.

Aromatic hydrocarbons are introduced into the environment as carbon black is used in various rubber and plastic products, especially in paints, inks, toys, etc.

Carbon black with high PAH content can cause harm when it comes into contact with the human body.

— Part 29.Determination of solvent extractables. The source of solvent extractables in carbon black is the same as that in Part 15, toluene or acetone The size of the isosolvable extractable fraction reflects the residual organic polymers that remain on the carbon black surface during carbon black production and are not completely decomposed.

The amount of extractables reflects the completeness of carbon black production conversion. A high content of extractables may contaminate the rubber compound and may cause It can cause pollution and the appearance of the product may also be problematic.

— Part 30.Determination of high temperature volatiles by thermogravimetric method. This part is the quantitative determination of high temperature volatiles of carbon black by thermogravimetric analyzer.

The method of weight loss does not include the heating loss at 125°C specified in GB/T 3780.8.It is suitable for the analysis of carbon black surface functional groups and adsorption Evaluation of the pyrolysis of adsorbents (e.g. hydrocarbons).

— Part 31.Determination of total hydrogen content. This part uses the thermal conductivity detector (TCD) method to determine the total hydrogen content in carbon black.

Content, applicable to carbon black for rubber, related to the reinforcing performance of carbon black.

The release of the above standards can improve the level of carbon black technology in China, promote the improvement of carbon black product quality, and provide reference for the relevant users of carbon black.

At the same time, it can be aligned with international standards, promote the effective use of standard functions, and better promote trade and exchange.

flow and technical cooperation.

Carbon black - Part 7: Determination of pH Warning. Personnel using this document should have practical experience in regular laboratory work. This document does not address all possible safety issues.

The user is responsible for taking appropriate safety and health measures and ensuring that the conditions stipulated by relevant national laws and regulations are met.

1 Scope

This document describes the determination of the pH value of carbon black by the boiling slurry method (Method A) and the ultrasonic slurry method (Method B).

This document is applicable to the determination of carbon black for rubber, acetylene black, pigment black and other carbon blacks.

2 Normative references

GB/T 3778

GB/T 3782

GB/T 6682

GB/T 7044

GB/T 8170

GB/T 9724

GB/T 12804

3 Terms and Definitions

There are no terms or definitions that require definition in this document.

4 Test conditions

Not contaminated by chemical gases such as acid and alkali.

5 Reagents or materials

Unless otherwise specified, only analytical grade reagents were used in the analyses.

5.1 Standard buffer solution shall comply with the requirements of GB/T 9724. 5.2 Anhydrous ethanol. 5.3 Acetone.

5.4 Water. Laboratory water should meet the requirements for Grade 3 water in GB/T 6682.Freshly prepared water is preferred.