GB/T 14190-2017Test methods for fibre grade polyester (PET) chip (English PDF)

5.1.1 Method A (capillary viscometer method)

5.1.1.1 Method summary DETERMINE the elution time of the solvent at 25 °C and the PET solution at a concentration of

0.005 g/mL, and CALCULATE the intrinsic viscosity according to the determined elution time and the solution concentration of the sample. The capillary viscometer uses 1B to meet the requirements that the kinetic energy correction term of the viscometer is not considered.

5.1.1.2 Instruments and equipment 5.1.1.2.1 Constant temperature bath. temperature control (25.00 ± 0.05) °C.

5.1.1.3 Solvents 5.1.1.3.4 Selection of solvents The calculation method for the intrinsic viscosity of PET chips is related to the solvent used. Two different solvents are available. 5.1.1.3.1, 5.1.1.3.2. 5.1.1.3.5 Solvent stability test The elution time of the solvent used is measured periodically. If the elution time of the solvent exceeds 1 % of the initial value (the initial value is the solvent elution time measured after solvent preparation), the solvent shall be discarded, and a new solvent shall be prepared.

5.1.1.4 Sample 5.1.1.4.1 WEIGH (0.125 ± 0.005) g of sample to the nearest

0.1 mg, and PLACE it in an Erlenmeyer flask with stopper. If the water content of the sample is more than 0.5 %, the sample shall be placed in a vacuum drying oven at a

5.1.1.6 Test procedure 5.1.1.6.1 FILTER the solution through a filter and ADD it to the Ubbelohde viscometer so that the liquid level is between the liquid filling lines.

5.1.1.7 Calculation of results 5.1.1.7.1 For tests using phenol/1,1,2,2-tetrachloroethane (mass ratio 50.50) as solvent, calculate the relative viscosity (etar), the specific viscosity (etasp) and the intrinsic viscosity ([eta]) according to formula (3) ~ formula (5).

5.1.1.8 Expression of results The calculation result of the intrinsic viscosity is expressed as the average value of the test values of the two parallel samples, and rounded off to the third decimal place according to GB/T 8170.

5.1.1.9 Precision 5.1.1.9.1 Repeatability For the determined values of two independent test results obtained under repeatability conditions, when the intrinsic viscosity is

0.630 dL/g ~

0.720 dL/g, the absolute difference between the two tests does not exceed the repeatability limit (

0.006 dL/g), and the case where it exceeds the repeatability limit (

0.006 dL/g) does not exceed 5 %. 5.1.1.9.2 Reproducibility The absolute difference between the two independent test results obtained under reproducibility conditions, when the intrinsic viscosity is

0.630 dL/g ~

0.720 dL/g, is not greater than the reproducibility limit (

0.010 dL/g), and the case where it exceeds the reproducibility limit (

0.010 dL/g) does not exceed 5 %.

5.1.2 Method B (relative viscometer method)

5.1.2.1 Method summary The PET sample is dissolved in the mixed solvent of phenol and tetrachloroethane, and then the solution and the blank solvent containing no sample flow in the two capillaries of the viscometer. The viscometer monitors the pressure drop p1 of the first solvent reference capillary and the pressure drop p2 of the second sample capillary. The relative viscosity is obtained from the ratio of p2 and p1, and the intrinsic viscosity of the sample is obtained by a mathematical model. The schematic diagram is shown in Figure 2.

5.1.2.2 Solvents Same as 5.1.1.3.

5.2.1 Method A (methanol transesterification method)

5.2.1.1 Method summary The sample is subjected to a transesterification reaction at high temperature and in the presence of methanol, diethylene glycol is released, and then the diethylene glycol content in the filtrate is measured by gas chromatography.

5.2.1.2 Instruments and equipment

5.4.2.7 Expression of results The calculation result is expressed as the average value of the two test-values, and is rounded off to one decimal place according to GB/T 8170.

5.4.2.8 Precision 5.4.2.8.1 Repeatability For the determined values of the two independent test results obtained under repeatability conditions, when the terminal carboxyl group is

35.0 mol/t, the absolute difference between the two tests does not exceed the repeatability limit (

2.0 mol/t), and the case where it exceeds the repeatability limit (

2.0 mol/t) does not exceed 5 %.

5.5.1 Method A (dry pulverization method)

5.5.1.1 Method summary After the sample is dried and pulverized, the chromaticity of the sample is tested with an automatic color difference meter, and the results are expressed in HunterLab color systems L, a, and b. NOTE. The color value test can only be compared if the materials are the same, the chip dicing, size and appearance are basically the same, the instrument geometry is the same and the viewing hole surface is close.

5.5.1.2 Instruments and equipment 5.5.1.2.1 Color difference meter. D65 light source, 10° angle of view, 0°/45° or 45°/0° light path geometry, HunterLab color system, it is recommended to use 45 mm ~ 52 mm viewing hole surface. 5.5.1.2.2 Sample cup. quartz glass. 5.5.1.2.3 Air drying oven. 5.5.1.2.4 Sample sieve. 833 µm and 350 µm.

5.5.1.3 Test procedure 5.5.1.3.1 PLACE the sample in the air dying oven, HEAT the bright PET chip at (140 ± 5) °C for 60 min; HEAT the semi-dull PET chip and full dull PET chip at (135 ± 5) °C for 30 min. After taking out the cooling, it was pulverized and sieved to obtain particles of 350 µm to 833 µm. NOTE. Chips that are not crystallized or have a very slow rate of crystallization can also be measured directly. 5.5.1.3.2 PLACE the sieved sample particles in the sample cup, make the sample tightly packed; PLACE it on the measuring hole, determine the chromaticity (L value, a value and b value) of the sample. The measurement is carried out every about 120° of rotation, and a total of three points are measured.

5.6 Test method for aggregated particles

5.6.1 Method summary The aggregated particles in the sample are observed under a microscope, the size is measured, and the number is counted.

5.6.2 Instruments and equipment

5.6.2.1 Microscope (magnification 200 times to 400 times) and microscope illumination.

5.6.2.2 Slicer. the division value is 1 µm.

5.6.2.3 Balance. the minimum division value is

0.1 mg.

5.6.2.4 Cover slip. the thickness is

0.17 mm.

5.6.2.5 Medical tweezer and scissor.

5.6.2.6 Micrometer. the division value is

0.01 mm.

5.6.2.7 Slide. the thickness is 1 mm.

5.6.3 Reagents Oil or wetting agent of which the refractive index is close to nD20 = 1.51.

5.6.4 Test procedure

5.6.4.1 Randomly TAKE five PET chips from the sample, and CUT each chip into 5 to 8 pieces of slices with a thickness of 20 µm with the slicer, so that the total mass of the sliced slices reaches 3 mg ~ 5 mg, to the nearest

0.1 mg. PLACE the slices on a clean glass slide, WET them well with reagents (or other physical means), PRESS the cover slip tightly against the sample to form a flat surface.

5.6.4.2 PLACE the slide containing the slices on the microscope stage, ADJUST the focal length of the microscope, and OBSERVE the aggregated particles larger than or equal to 10 µm (or the required size) with transmitted light. Round particles are measured and counted by their diameter, and particles of other shapes are measured and counted by the longest part.

5.6.5 Calculation of results The aggregated particle is calculated according to formula (10).

5.11 Test method for iron content...

5.11.5 Test procedure

5.11.5.1 ADD 5 mL of hydrochloric acid solution to the residue after ashing, HEAT to dissolve, COOL and FILTER into a 100 mL beaker with filter paper, and WASH the filter paper with approximately 40 mL of distilled water to the beaker.

5.11.5.2 MEASURE the absorbance of the sample solution according to the procedure of 5.11.1.2, 5.11.4.3.

5.11.6 Calculation of results The iron content is calculated according to formula (18).

5.11.7 Expression of results The calculation result is expressed as the average value of the test values of the two parallel samples, and is rounded off to one decimal place according to GB/T 8170.

5.11.8 Precision

5.11.8.1 Repeatability For the determined values of the two independent test results obtained under repeatability conditions, when the iron content is

0.5 mg/kg ~

4.0 mg/kg, the absolute difference between the two tests does not exceed the repeatability limit (

0.5 mg/kg), and the case where it exceeds the repeatability limit (

00.5 mg/kg) does not exceed 5 %.

5.11.8.2 Reproducibility The absolute difference between the two independent test results obtained under reproducibility conditions, when the iron content is

0.5 mg/kg ~

4.0 mg/kg, is not greater than the reproducibility limit (

1.0 mg/kg), and the case where it exceeds the reproducibility limit (

1.0 mg/kg) does not exceed 5 %.