Original standard number GB 8326-87 HG/T 2758-1996 Determination of viscosity number and viscosity ratio of cellulose acetate dilute solution HG/T2758-1996 Standard download decompression password: www.bzxz.net

HG/T2758—1996
This standard is equivalent to the international standard ISO1157:1990 "Plastics—Determination of viscosity number and viscosity ratio of cellulose acetate dilute solutions", and is consistent with it in terms of technical content and writing format. This standard is based on GB/T1.1~-1993, and the previous version of the standard GB832687 is revised into an industry standard. The difference from the previous version is the addition of a preface, an ISO preface, and a chapter on precision. The text is also revised accordingly in accordance with ISO1157:1990. From the date of entry into force of this standard, GB8326-87 will be invalidated at the same time. This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China, and this standard is under the jurisdiction of the Plastic Resin Products Branch (SC4) of the National Plastic Standardization Technical Committee. The drafting unit of this standard: China Institute of Metrology. The main drafters of this standard: Zhang Hongan, Ping Lei, ISo Foreword
The International Organization for Standardization is a worldwide federation of national standards associations (ISO member groups). The work of developing international standards is carried out by ISO technical committees. Any member group interested in a project determined by a technical committee has the right to send representatives to participate in the technical committee. Governmental or non-governmental international organizations may also participate in this work by contacting ISO. ISO and the International Electrotechnical Commission (IEC) work closely on all subjects of electrotechnical standardization. Draft international standards adopted by the technical committee are circulated to members for voting. At least 75% of the member groups' votes are required to publish them as international standards. International Standard ISO 1157 was prepared by ISO/TC 61 Plastics Technical Committee. This second edition replaces and cancels the first edition (ISO 1157: 1975), and the first edition is slightly revised. Chemical Industry Standard of the People's Republic of China Determination of viscosity number and viscosity ratio of dilute solutions of cellulose acetate HG/T 2758 -1996
idtISo1157:1990
Warning: The use of this standard may involve hazardous materials, operations and equipment. This standard does not address all safety issues related to its use. Users of this standard are responsible for establishing appropriate safety measures and determining the applicability of the regulatory system before use. 1 Scope
This standard specifies the method for determining the dilute solution viscosity number and viscosity ratio of cellulose acetate in a mixed solvent of dichloromethane and methanol. It is applicable to cellulose acetate with an acetic acid value of not less than 50%. 2 Cited standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1632-1993 Determination of viscosity and intrinsic viscosity of dilute polymer solutions (eq VISO1628/1:1984) 3 Definition
For the definition of viscosity and other terms, definitions and formulas, see GB1632-19934 Principle
The outflow time of solvent and cellulose acetate solution with a concentration of 5mM/mL is determined by conventional methods at 25°C. The viscosity number and viscosity ratio are calculated from these measured values ​​and the known solvent concentration. In this method, the corrections for density differences and kinetic energy are very small and are not considered. s Solvents
All solvents used in the determination are of recognized analytical grade. 5.1 Dichloromethane: Relative density (20/20℃) is 1.321~1.331. The volume of stuffing steamed at 39~40.5℃ under pressure of 101.325kP (760mmHg) is not less than 95%. Safety precautions: Inhalation of difluoromethane is harmful to the human body, avoid contact with the skin. 5.2 Methanol: Relative density (20/20℃) is 0.792~0.795, and the distillation temperature range is 64.5~65.5℃ under pressure of 101.325kPa (760mmHg). Safety precautions: Methanol is a flammable and toxic substance, and inhalation is harmful to the human body. The container must be sealed and away from fire, do not smoke, and avoid contact with the skin. 6 Instruments 6.1 Volumetric flask: 100mL, with ground glass stopper & 2 Constant temperature water bath: can be maintained at 25±0.05℃. Approved by the Ministry of Chemical Industry of the People's Republic of China on April 15, 1996, and implemented on January 1, 1997
HC/T 2758 1996
63 Viscometer: Air-bearing column Ubbelohde viscometer, main dimensions see Figure 1, or other viscometers that can produce the same results. N
Volume between scale lines
1.8mL to 2.2mL
Capillary 0o.35~0.40mm
Filling line
Figure 1 Island viscometer
6.4 Dryer: Equipped with desiccant (such as anhydrous calcium chloride) 65 Analytical balance: Sensitivity 0.1 convex.
6.6 Stopwatch: graduation value 0.1s
7 Operating steps
HG/T 2758—1996
7.1 Before use and when inconsistent readings occur, as well as after a period of normal use, the viscometer should be cleaned with a mixture of equal volumes of concentrated sulfuric acid and saturated aqueous potassium dichromate, followed by water rinse: then washed with two acetones and dried with a dust-free air stream: between two consecutive satisfactory measurements, it is sufficient to wash with acetone and dry as above. 7.2 Dry a sufficient amount of cellulose acetate sample in an oven at 105±2℃ for 3h, then cool it in a desiccator (6.4) for 1h before use.
7.3 Mixed solvent and preparation: Mix 90 parts (volume) of dichloromethane (5.1) and 10 parts (volume) of medium alcohol (5.2) at 25±0.05℃.
7.4 Weigh 0.5±0.5 mg of dry cellulose acetate (accurate to 0.1 mg), transfer quantitatively to a volumetric flask (6.1), add about 60 mL of mixed solvent, pay attention to avoid lumps, and plug the flask. Gently stir the mixture for 5 minutes, and then place it in a constant temperature bath (6.2) at 25±0.05℃ for 55 minutes. Repeat this operation until the cellulose acetate is completely dissolved. Keep the solution at 25±0.05, then add solvent at the same temperature until the volume of the solution reaches 100 mL, cover the flask tightly, shake it upside down several times, and let it stand for 2 hours.| |tt||7.5 Use a viscometer to measure the flow time of solutions and mixed solvents. 7.5.1 When using an Ubbelohde viscometer, the operation is as follows: pre-immerse the viscometer in a constant temperature water bath (6.2) to a depth of about 20 mm above the upper scale line. Fix the viscometer and make it vertical.
Use a pipette to transfer the solution prepared in (7.3) from the container (6.1) into the tube L of the viscometer (see Figure 1). The volume of the solution should be such that the liquid level is between the two filling lines. After at least 10 minutes, use dust-free air pressure or suction to raise the solution in the viscometer to a position close to the center of the upper ball. Close tube N so that the solution does not flow out from the lower end of the capillary, then open tube N and measure the time it takes for the meniscus of the solution to flow between the two scale lines. Press or suction the fluid to the upper ball and then measure the flow time. 7.5.2 If the viscometer is not an Ubbelohde type, the above steps should be appropriately changed. 7.5.3 The flow time of the solution should be the average of two measurements. The difference between the two measurements should not be greater than 0.4% of the smaller value. The average flow time of the solvent should be measured in the same way. If two values ​​that meet the above conditions and the difference between the two measurements is less than 0.4% of the smaller value cannot be obtained in no more than four measurements, the viscometer should be cleaned and the test should be repeated with new solution. If it is necessary to relate the viscosity number and viscosity ratio to the length of the molecular chain, samples with the same acetic acid value should be comparable. If the sample contains plasticizers, additives, fillers and other substances that affect the viscosity, they must be separated by a method agreed upon by both parties. 8.1 It is best to express the results in terms of viscosity number, expressed in mL/g, and calculated using formula (1): Viscosity number
Where: 1—solvent flow time, s;
fa——solvent flow time, si
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Concentration of cellulose acetate solution, g/m³. 8.2 Viscosity ratio is calculated using formula (2):
Viscosity ratio
The symbols in the formula have the same meaning as those in formula (1). (1)
Precision
HG/ T 2758 —1996
Because inter-laboratory data have not yet been obtained, the precision of this test method is still unknown. Before these data are obtained, this method is not applicable in specifications or in controversial situations. Test report
The test report should include the following items:
Indicate that it is in accordance with this industry standard:
A comprehensive description of the product being tested, including the product name, model, factory batch number, source, etc.: Sample treatment before the test:
Viscosity number (reported to the nearest 0.1mL/g) and (or) viscosity ratio: Test temperature,
all test conditions that may affect the results other than those specified in this standard.
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