GB/T 42701-2023Textiles—Identification of naturally colored cottons— Chemical staining method (English PDF)

Foreword

This document was drafted in accordance with the rules given in GB/T 1.1-2020 "Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents".

1 Scope

This document describes a method for the identification of naturally colored cottons (including natural brown cotton and natural green cotton) using the chemical staining method.

This document applies to naturally colored cottons and their pure spinning products, blended or interwoven products of naturally colored cottons and uncolored fibers.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 6682, Water for analytical laboratory use -- Specification and test methods

3 Terms and definitions

This document has no terms and definitions that need to be defined.

4 Principle

Under the specified conditions, drop the color reagent to wet the specimen. The specific polyphenol pigment contained in the naturally colored cotton in the specimen will chemically react with the color reagent and change the color of the specimen. Observe the color change of the specimen to determine whether the specimen contains naturally colored cottons.

5 Reagents and equipment

Unless otherwise specified, all reagents are analytically pure.

5.4 Sodium hydroxide solution: the mass concentration is 10 g/L

5.2 4-(Dimethylamino) cinnamaldehyde: purity is >=95.0%.

5.3 Iodine-potassium iodide reagent: a mixed aqueous solution containing 1.3 g/L iodine and 2.4 g/L potassium iodide.

5.6 Reaction container: a Petri dish with a diameter of 90 mm or a beaker with a capacity of not less than 100 mL.

5.8 Constant temperature water bath: can maintain the temperature at (60±1)°C and (80±1)°C.

5.7 Oven: can keep the temperature at (60±1)°C

5.1 Water: Grade III water in accordance with GB/T 6682

6 Sampling

6.1 Loose fiber: randomly draw about 0.2 g of fiber from at least 3 sites. After merging, arrange them into straight parallel bundles.

6.2 Yarn: randomly cut 20 cm long yarn segments from at least 3 different bobbins, hanks or bobbins, totaling about 0.2 g. Combine them into yarn bundles.

6.3 Fabric: randomly cut a 5cm × 5cm cloth sample at least 5 cm away from the selvage edge for testing. For woven fabric samples, if necessary, the warp and weft yarns can be disassembled and tested separately. Indicate in the test report.

6.4 During the operation of sample preparation, the specimen shall be prevented from being contaminated.

7 Specimen pretreatment

7.1 If the specimen contains starchy size, the size shall be reduced first. See Annex A […]