1 Scope
This standard applies to the determination of the intrinsic viscosity of prepolymers, polyester chips and melts. The measurement range is: 0.020-1.500dL/g
2 Method Overview
The sample was dissolved in a mixture of phenol and 1,2-dichlorobenzene. The flow time t was measured by an Ubbelohde viscometer. The flow time of the mixture of phenol and 1,2-dichlorobenzene was measured by an Ubbelohde viscometer. , to determine the relative viscosity of the sample η relative = t / t0. The relationship between relative viscosity and intrinsic viscosity can be expressed by the Billmeyer equation:
η characteristic=1/4×(ηrelative-1)/C+3/4×(lnηrelative)/C
Where: C-sample solution concentration, g/100mL;
η characteristics - sample intrinsic viscosity, dL/g;
η-relative-sample relative viscosity.
3 Instruments
3.1 Viscometer: The temperature can be controlled to 25.00 ± 0.05 °C.
3.2 Ubbelohde viscometer, plus a viscometer frame that matches it.
3.3 Thermometer: 0-50°C, 0.1 degree.
3.4 Magnetic heating stirrer.
3.5 Pipette: 25 mL.
3.6 metal filter: 200 mesh.
3.7 stoppered flask: 50 mL.
3.8 Teflon stirrer.
3.9 Glass funnel: 5 cm in diameter.
3.10 Beaker: 5000 mL.
4 Reagents and materials
4.1 Water: Meets the requirements for tertiary water specified in GB 6682-92.
4.2 Phenol.
4.3 1,2-Dichlorobenzene.
4.4 Ethanol.
4.5 Hydrochloric acid solution: (1+1).
4.6 Acetone.
5 test steps
5.1 Preparation of phenol-1,2-dichlorobenzene solution
5.1.1 mixed phenol / 1,2-dichlorobenzene: 510mL 1,2-dichlorobenzene was added to a bottle containing 1kg of phenol (3:2 by weight mixing), the density of the solution was 1.151 ±0.001g/cm3 (25 °C).
5.1.2 Heat the mixture in an oven. The oven temperature is 60°C. During the heating process, it should be shaken continuously until it is evenly mixed.
5.1.3 Pour the solution through the filter into the brown reservoir bottle.
5.2 Determination of blank
5.2.1 set the viscosity bath water temperature 25.00 ± 0.05 °C.
5.2.2 Add approximately 17 mL of phenol/1,2-dichlorobenzene solution (5.1) to the viscometer between the two marked lines.
5.2.3 Put the viscometer in the water bath of the viscometer and keep it at a constant temperature for 15-20 minutes. Determine the flow time of phenol/1,2-dichlorobenzene. Measure five times. The deviation should not exceed 0.1 second.
5.2.4 Take the average of five tests as the flow time of each freshly prepared phenol/1,2-dichlorobenzene solution. The flow time of the to measure should be between 80-120 seconds. Too high and too low are not allowed.
5.3 Preparation of Samples
5.3.1 The moisture content of the polyester should be less than 0.5%. Wet slices should be cleaned with acetone and the residual acetone should be sliced and dried in an oven at 80 °C for 15-20 minutes. The residual moisture is so small that it does not have a significant effect on the relative viscosity value.
5.3.2 If the polyester has a high degree of crystallinity, its crystal structure must be destroyed. The method is to load the slices into a suitable grinder to crush the slices (pressure is about 150 bar).
5.4 Test
5.4.1 Finely weighed 125-145mg sample to a value of 0.0001g and put it into a 50-mL Erlenmeyer flask. Add 25 mL (weight 28.75--28.80 g) of phenol/1,2-dichlorobenzene solution (5.1.1 ), put a magnetic stir bar, and cap it.
5.4.2 Place the flask on a magnetic stirrer and heat, stir and dissolve the sample at 90-100°C.
5.4.3 After the sample is dissolved, cool the sample.
5.4.4 The sample solution is filtered through a 200 mesh metal filter and added to the viscometer.
5.4.5 The viscometer shall be immersed in a water bath of the viscometer for a period of 20 minutes. Through three measurements, the flow time of the sample solution shall be determined. The difference shall not exceed 0.2 second.
5.4.6 Calculate the average t of the three measurements.
5.5 Calculation
5.5.1 Determination of Relative Viscosity
η relative = t (average flow time of sample solution, second) / t0 (average flow time of phenol/1,2-dichlorobenzene solution, second)
5.5.2 Correlation Factor F
The relevant factor F read out from the attached table.
5.5.3 Calculation of Intrinsic Viscosity
With the relevant factor F, divided by the weight of the sample, the value is the intrinsic viscosity.
η characteristic = F/W
Among them: η characteristics - sample intrinsic viscosity, dL/g;
F-related factor, mg·dL/g;
W-sample weight, mg.
5.5.4 The difference between two parallel determinations of the same sample is not greater than 0.008 dL/g, and the arithmetic average is taken as the measurement result. The result is rounded off to the third decimal place.
5.6 Viscometer Cleaning
5.6.1 After the operation is complete, pour the solution from the viscometer into the waste bottle.
5.6.2 Place the viscometer to be cleaned in a beaker.
5.6.3 Add an appropriate amount of ethanol to the viscometer and wash it several times with a suction earball. Thoroughly pour off the residue.
5.6.4 soak in hydrochloric acid solution for one day.
5.6.5 Clean the viscometer with water, rinse with ethanol, and dry it upside down on the shelf.
5.6.6 The viscometer is cleaned with chromic acid lotion when it is used for the first time or when there are many impurities.
Description
When the normal polyester chips are melted or no oil, the heating temperature cannot be too high and cannot exceed 100°C. This step takes about 15 minutes.
When the dry section before spinning is dissolved, the heating temperature can be increased to 130-140°C.
7 Precautions
Phenol, 1,2-dichlorobenzene and acetone are toxic. Avoid inhalation and contact with the skin. Wear rubber gloves and goggles when preparing and using these chemicals. All operations including waste treatment should be completed in a fume hood. . The waste liquid is poured into the waste barrel and processed regularly.
