GB/T 13505-2025High purity insulating wood pulp (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 13505-2007 "High-purity insulating wood pulp". Compared with GB/T 13505-2007, the main differences are in structural adjustments and formatting. Aside from the logical changes, the main technical changes are as follows:

a) The scope has been changed (see Chapter 1, Chapter 1 of the.2007 edition);

b) The classification has been changed (see Chapter 4,

3.1 of the.2007 edition);

c) The requirement for first-class products has been removed, and the requirement for qualified products has been added (see 5.1,

4.1 in the.2007 edition);

d) The tensile index, iron content, pH value of the water extract, conductivity of the water extract, water-soluble chloride content, and crosslinking properties of the superior grade product were modified. Requirements for moisture, dust, and appearance of goods (see 5.1, 5.3, and 5.4;

4.2 in the.2007 edition);

e) Increased requirements for water extract pH, water-soluble sulfate content, acetone-soluble matter, D65 brightness, and fiber bundle properties (see...) 5.1) and test methods (see 6.9, 6.12, 6.13,

f) The requirements for pulp water extract acidity, dichloromethane extract content, and moisture content in sales quality calculations have been removed (see the.2007 edition). 4.1) and test methods (see 5.6,

5.12 in the.2007 edition);

g) An additional test method for appearance has been added (see 6.19);

h) Added dimensional tolerance requirements and test methods for flat slurry plates (see

1 Scope

GB/T 13505-2025 is the Chinese national standard covering the pulp from which transformer and cable insulating paper is made - where the conductivity, the ash and the metal ions matter more than the strength, because they are what will eventually break down under electrical stress in oil. Issued on 2 December 2025, it has been in force since 1 July 2026, replacing GB/T 13505-2007.

This document specifies the requirements, inspection rules, marking, packaging, transportation, and storage of high-purity insulating wood pulp, and describes the corresponding test methods. The law provides information on classification. This document applies to the production, inspection, and sale of high-purity insulating wood pulp.

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 451.1 Determination of dimensions and skewness of paper and paperboard

GB/T 462 Determination of moisture content in analytical samples of paper, paperboard and pulp

GB/T 740 Sampling of Pulp Samples

GB/T 742 Determination of ash content (on-ignition residues) in papermaking raw materials, pulp, paper and paperboard (575°C and 900°C)

GB/T 1545-2008 Determination of acidity or alkalinity of extracts from paper, paperboard and pulp

GB/T 1546 Determination of kappa number in pulp

GB/T 1548 Determination of intrinsic viscosity in copper ethylenediamine (CED) solution for pulp

GB/T 2678.2-2021 Determination of water-soluble chlorides in paper, paperboard and pulp

GB/T 2678.6-2023 Determination of water-soluble sulfates in paper, paperboard and pulp

GB/T 2828.1 Sampling Procedures for Inspection by Attributes - Part

1.Sampling Schemes Retrieved by Acceptable Quality Limit (AQL) for Lot-by-Lot Inspection

GB/T 3332 Determination of pulp freeness (Schober-Regler method)

GB/T 7974 Determination of blue light diffuse reflectance factor D65 luminance of paper, paperboard and pulp (diffuse/vertical method, outdoor daylight conditions)

3 Terms and Definitions

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