GB/T 39026-2020Test method for the identification of recycled polyethylene terephthalate (PET) fiber (English PDF)

5.1 Instruments and Equipment

5.1.1 High performance liquid chromatograph, equipped with diode array detector (DAD) and column temperature control device.

5.1.2 Analytical balance. with an accuracy of 0.1 mg.

5.1.5 Bench vice or other fixing device.

5.1.6 Automatic pipetting device or pipette. 1 mL, 20 mL and 25 mL.

5.1.7 Measuring cylinder. 50 mL and 200 mL.

5.1.8 Volumetric flask. 2 L.

5.1.10 Syringe-driven filter, filter membrane 0.45 µm; made of PTFE.

5.1.11 Reagent reservoir, with a stopper; made of glass.

5.1.92 mL threaded sample bottle that can be used for automatic sample injection of the high performance liquid chromatograph, with PTFE liner.

5.2 Reagents and Materials

5.2.1 Methanol, analytically pure.

5.2.2 Methanol, chromatographically pure.

5.2.3 Catalyst. zinc acetate, analytically pure.

5.2.4 Transesterification solution. weigh-take 60 mg of zinc acetate; use methanol to dissolve it and dilute to 2 L.

6.1 Methanolysis

6.1.1 Weigh-take 0.8 g (accurate to 0.1 mg) of the specimen to be tested.

6.1.2 Place the specimen into the reaction tube; accurately add 25 mL of the transesterification solution. Use the bench vice to tighten the cap of the reaction tube (to ensure air tightness); vertically put it into the heating device.

6.2 Swelling-extraction

6.2.1 Weigh-take about 5 g of the same specimen to be tested; place it in a drying oven that is previously heated to 105 °C to dry for 30 min. Then, take it out and put it in a desiccator to cool it down; reserve it for later use.

6.2.2 Use a measuring cylinder to respectively weigh-take 160 mL of sulfolane and 40 mL of acetonitrile. Put them into the reagent reservoir, put on the cap; shake it well and reserve it for later use.

6.2.4 Pour the sample into a centrifuge tube, then, at a centrifugal speed of 4,000 r/min, centrifuge for 8 min. Take the supernatant; filter it through the syringe-driven filter to a […]

6.3 High Performance Liquid Chromatography Detection

Respectively conduct high performance liquid chromatography detection on the treatment liquids treated in accordance with 6.1 and 6.2. After the chromatographic detection is completed, derive the original signal data of high performance liquid chromatography.

6.4 Data Processing and Identification

6.4.1 In terms of the signal obtained after the alcoholysis treatment through the high performance liquid chromatography detection, respectively define the two strong peaks with retention time 12.11 min ~ 12.55 min and 15.50 min ~ 16.10 min as positioning peak "peak1" and positioning peak "peak2", as it is shown in Figure 2;

6.4.3 The detailed information of the positioning peak and the characteristic peak is shown in Table 2.

6.4.4 Establish a discriminant function Wi for the relative content of fingerprint peaks "peak3", "peak4", "peak6" and "peak7". The discriminant function is related to the dispersion of the data and is the quadratic function of Xi, as it is shown in Formula (5).