GB/T 45128-2025Plastics - Determination of water content (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 modified to adopt ISO 15512:2019 "Determination of water content of plastics".

Compared with ISO 11512:2019, this document has many structural adjustments. The structural number changes between the two documents are shown in the table below.

See Appendix A.

The technical differences between this document and ISO 15512:2019 and their reasons are as follows.

--- Adjust the operation and related explanations of the method in the scope of application of the method in Chapter 1 to the newly added introduction to increase the applicability of the standard.

Readability;

--- Adjust the provisions of the method detection limit in Chapter 1 to the calculation and expression of the results of each method (see 5.5, 6.5, 7.5, 8.5, 9.5 and 10.5.2) to meet the requirements of standard compilation;

--- Use the normative reference GB/T 6283 to replace ISO 760 (see 5.2.2, 5.3.8) to adapt to my country's technical conditions and increase operability Sex;

--- Adjust Note 1 of ISO 15512:2019 "Pressure moisture analyzer" to the main text (see 8.3.1) to comply with the requirements for standard compilation;

--- Unify the unit of water content of nitrogen and unify it to 0.554×10-6 in accordance with the provisions of Appendix A of GB/T 5832.2-2016 (volume fraction) (see 7.2.6, 9.2.3) to increase the consistency between the standard and the Chinese standard;

--- Adjust the informative Appendix B of ISO 15512:2019 to a normative appendix (see Appendix C) to meet the requirements for standard preparation;

--- Adjust the informative Appendix C of ISO 15512:2019 to a normative appendix (see Appendix D) to meet the requirements for standard preparation.

The following editorial changes were made to this document.

--- The informative reference GB/T 1034 replaces ISO 62 (see introduction) to adapt to my country's technical conditions;

--- The informative reference GB/T 1631.1 replaces ISO 1632.1 (see C.2) to adapt to my country's technical conditions;

--- The informative reference GB/T 1631.3 replaces ISO 1632.3 (see C.2) to adapt to my country's technical conditions;

--- The informative reference GB/T 1631.4 replaces ISO 1632.4 (see C.2) to adapt to my country's technical conditions;

--- The informative reference GB/T 1631.5 replaces ISO 1632.5 (see C.2) to adapt to my country's technical conditions;

--- The informative reference GB/T 12006.1 replaces ISO 370 (see C.2) to adapt to my country's technical conditions.

Introduction

Moisture content is an important parameter for processing materials. Too high moisture content will affect the processing performance of the material.

This document describes six moisture content test methods.

---Method A is anhydrous methanol extraction method. Anhydrous methanol is used to extract water from the sample, and then the extract is subjected to Karl Fischer Titration.

---Method B1 is a tube furnace evaporation method. The water contained in the sample is evaporated and transported to the titration cell by dry air or nitrogen, and then the collected water was then coulometrically determined using a Karl Fischer titrator.

---Method B2 is the sample bottle evaporation method. The water contained in the sample is evaporated and transported to the titration cell by dry air or nitrogen, and then the collected water was then subjected to Karl Fischer titration using a Karl Fischer titrator.

---Method C is a pressure measurement method. The evaporation of water in the vacuum system causes an increase in pressure, and the water content of the sample is calculated by the pressure increase.

The evaporation temperature is not specified in this document, and for the pressure method a temperature of.200°C is generally used. However, for some condensation materials this temperature may cause condensation reaction and produce water.

---Method D is to use phosphorus pentoxide (P2O5) coulometric method. The water contained in the sample is evaporated and then transported through dry air or nitrogen.

It is sent to a phosphorus pentoxide electrolytic cell, and then the collected water is subjected to thermocoulometric determination.

---Method E is the calcium hydride test method. The sample is heated under vacuum to evaporate the water in the sample. The evaporated water reacts with calcium hydride Hydrogen (H2) and calcium hydroxide are generated. Hydrogen (H2) increases the pressure of the vacuum system, and the sample content is calculated by the pressure increase value.

The volatile components that do not react with calcium hydride condense into liquid in the cooling trap and do not affect the determination of water content.

The water content of plastics tested by the above method is different from the water absorption of plastics tested by GB/T 1034-2008 (dynamic balance).

Performance parameters, understanding the differences between the two standards is conducive to the implementation of the standards.

The differences in sample packaging, sample handling, equipment and setting parameters will affect the test results of plastic moisture content.

The inter-laboratory comparability of moisture content determination of raw materials is usually poor. Package the samples in dry glass containers or waterproof sealed bags and place them in dry Processing samples in a nitrogen or air environment is conducive to improving the comparability of data between laboratories. In order to improve repeatability and reproducibility, strict Follow the test procedures specified in this document.

The optimum heating temperatures described in this document will vary depending on the material being tested, the equipment used, and actual conditions.

The water in the test material will not evaporate completely, and too high a temperature will cause degradation and condensation reactions, resulting in the generation of water.

A method for optimizing heating temperature was proposed in order to select a suitable temperature for the determination of water content and to improve the comparability among laboratories.

Determination of moisture content in plastics

1 Scope

This document describes six methods for determining the moisture content of plastic powders, granules and products. Method A, Method B, Method C and Method E are suitable for for all types of plastics, method D is suitable for polyamide (PA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), epoxy resin Resins, polyesters, polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polylactic acid (PLA), polyamide diamine (PAI), not suitable for releasable Samples of NH3.

Method A (anhydrous methanol extraction method) is applicable to all samples with a size less than 4mm×4mm×3mm and a water content greater than or equal to 0.1%.

The method is accurate to 0.1%. This method can also be used to determine the powder prepolymer material that is insoluble in methanol.

Method B1 (tube furnace evaporation method) is applicable to all samples with a size less than 4 mm × 4 mm × 3 mm and a water content greater than or equal to 0.01%.

Determination of.

Method B2 (vial evaporation method) is applicable to all samples with a size less than 4 mm × 4 mm × 3 mm and a water content greater than or equal to 0.01%.

Determination of.

Method C (pressure measurement method) is applicable to the determination of water content greater than or equal to 0.01%. This method is not applicable to the determination of water containing volatile compounds.

For plastic samples containing substances (except water), volatile compounds have a significant effect on pressure at room temperature. When using method C, gas chromatography is used Regularly check samples (especially new types or brands) for volatile compounds using methods such as Method D [phosphorus pentoxide (P2O5) coulometric method] is applicable to the determination of water content greater than or equal to 0.01%. This method is not applicable to Plastic samples containing volatile compounds (except water), volatile compounds [especially volatile components that can react with phosphoric acid pentoxide coating] Regularly check samples (especially new types or grades) for volatile chemicals.

Compound.

Method E (calcium hydride test method) is applicable to the determination of water content greater than or equal to 0.001%.

2 Normative references

The contents of the following documents constitute the essential clauses of this document through normative references in this document.

For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to this document.

GB/T 6283 Determination of water content in chemical products Karl Fischer method (general method) [GB/T 6283-2008, ISO 760:1978,NEQ]

3 Terms and definitions

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

4 Sample preparation and storage

The sample can be in any form such as plastic powder, pellets and products.

Quickly cut large-size samples into pieces smaller than 4mm×4mm×3mm. Take a certain amount of representative samples and place them on the Put the solution into a flask or sealed bag that has been dried to constant weight and seal the mouth of the flask immediately.