GB/T 33317-2025Plastics - Determination of hexamethylenetetramine content in phenolic resins - Kjeldahl method, perchloric acid method and hydrochloric acid method (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document replaces GB/T 33317-2016 "Determination of Hexamethylenetetramine Content in Plastic Phenolic Resins - Kjeldahl Method and High Chlorine Content".

Compared with GB/T 33317-2016, the main technical changes in "Acid Method and Hydrochloric Acid Method" are as follows, except for structural adjustments and editorial modifications.

---A new chapter on "Terms and Definitions" has been added (see Chapter 3);

--- An automatic potentiometric titration method has been added to the perchloric acid method (see 5.5.2).

This document is modified to adopt ISO 8988:2006 "Determination of hexamethylenetetramine content in phenolic resins—Phenolic plastics—Kjeldahl nitrogen determination method, high chlorine content—" Acid method and hydrochloric acid method.

The technical differences between this document and ISO 8988:2006, and the reasons therefor, are as follows.

---The unit for the requirements of mass and analytical balance precision in the standard has been changed to mg (see 4.3.6, 4.4.4, 4.5.1, 5.4.5).

(5.5.1.1, 5.5.1.2, 5.5.2.2, 6.4.3, 6.5.1, 6.5.2) for ease of use;

---ISO 385 (see 4.4.3) has been replaced with the normatively referenced GB/T 12805 to adapt to my country's technical conditions and increase operability.

Actual nature;

---The calculation formula has been changed to use the actual concentration of the solution (see 4.6). The international standard directly uses 0.10 for solution concentration.

Substituting 0.20 into the calculation will result in a deviation when the actual concentration is prepared. Using the actual concentration of the solution can improve the accuracy of the results.

---The reproducibility requirement in 3.7 of ISO 8988:2006 is listed and explained in this standard (see 4.7), because the Kjeldahl method has not yielded [reproducibility details].

Obtain relevant data from inter-laboratory pairs;

---Automatic potentiometric titration has been added to the perchloric acid method (see 5.5.2). With the development of modern analytical techniques, automatic potentiometric titration has become increasingly important.

Its accuracy and automated operation are becoming increasingly widely adopted, therefore this method has been added to this document;

---The normative reference GB/T 601 (see 5.3.4) has been added because the automatic potentiometric titration method has been added to the perchloric acid method in this paper.

The following minimal editorial changes have been made to this document.

---The standard title has been revised to "Determination of Hexamethylenetetramine Content in Phenolic Resins of Plastics. Kjeldahl Method, Perchloric Acid Method, and Hydrochloric Acid Method".

Law".

Please note that some content in this document may involve patents. The issuing organization of this document assumes no 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 Plastics Standardization (SAC/TC15).

1 Scope

This document describes three methods for determining the hexamethylenetetramine content in phenolic resins. These three methods are equivalent.

The Kjeldahl method is not applicable to phenolic resins containing other nitrogen compounds, nor to resins containing additives that can be oxidized by perchloric acid.

The perchloric acid process is not suitable for phenolic resins containing other acidic or alkaline substances, nor for resins containing additives that can be oxidized by perchloric acid.

The hydrochloric acid method is not suitable for phenolic resins containing other acidic or alkaline substances.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 601 Preparation of Standard Titration Solutions for Chemical Reagents GB/T 12805 Burettes for Laboratory Glassware

3 Terms and Definitions

This document does not contain any terms or definitions that need to be defined.

4 Kjeldahl method for nitrogen determination