BS 2880-1991 Methods of testing cellulose acetate flake《醋酸纤维素片的试验方法》.pdf

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1、BRITISH STANDARD BS 2880:1991 Methods of testing cellulose acetate flake Incorporating corrigendum February 2010 ICS 83.080.10National foreword This British Standard is a revision of BS 2880:1957 and BS 2880: Addendum No.1:1959 which are withdrawn. The UK participation in its preparation was entrust

2、ed to Technical Committee PRI/82, Thermoplastic materials. A list of organizations represented on this committee can be obtained on request to its secretary. In this revision the test methods have been aligned with the latest versions of the relevant International Standards. In some case the precise

3、 ISO procedure has been invoked. In these cases it is intended that the ISO methods of test will be published as BS 2782 methods identical with the corresponding ISO standards. However, at the present time, although method numbers have already been allocated, some BS 2782 methods have not yet been p

4、ublished and, until they have, the corresponding ISO standards should be used. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations.

5、 BS 2880:1991 This British Standard, having been prepared under the direction of the Plastics and Rubber Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 30 August 1991 BSI 2010 First published July 1957Amendments/corrigenda issued since p

6、ublication Date Comments 28 February 2010 Supersession text amended ISBN 978 0 580 69807 1BS 2880:1991 1 1 Scope This standard describes methods of test for the following cellulose acetate flake properties: a) moisture content; b) ash content; c) acetic acid yield; d) bulk density; e) particle size

7、distribution; f) free acidity; g) viscosity ratio of a 5 g/L solution at 25 C; h) viscosity at a concentration of 60 g/L; i) viscosity at 25 % concentration at 25 C; j) insoluble particles; k) original light absorption and change of light absorption after heating of plasticized cellulose acetate; l)

8、 the reduction in viscosity ratio on moulding. NOTE The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definition For the purposes of this British Standard the following definition applies. cellulose acetate flake non-plasticized acetic acid esters of

9、cellulose (excluding mixed acid esters) in flake form 3 Method 1. Determination of moisture content 3.1 Principle A specified mass of material is heated at 105 C for 3 h and the percentage loss of mass is used to determine the moisture content. 3.2 Sampling Select a representative sample following t

10、he principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 3.3 Procedure Determine the moisture content of the sample selected in accordance with 3.2 by the met

11、hod described in BS 2782-4:Method 431C. NOTE BS 2782-4:Method 431C is identical with ISO 585. 4 Method 2. Determination of ash content 4.1 Principle A given mass of material is heated at 575 C to constant mass and the residual mass is taken as the ash content. 4.2 Sampling Select a representative sa

12、mple following the principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 4.3 Procedure Determine the ash content of the sample selected in accordance with 4.2

13、 by the method described in BS 2782-4:Method 470C except that the temperature used shall be 575 C. NOTE BS 2782-4:Method 470C is identical with ISO 3451-3. 5 Method 3. Determination of acetic acid yield 5.1 Principle Finely divided cellulose acetate stands in contact with a mixture of acetone and aq

14、ueous sodium hydroxide. The amount of alkali consumed in hydrolysing the cellulose acetate is then measured by titration. NOTE The method described for the estimation of acetic acid yield has been found to be suitable for cellulose acetates of acetic acid yields ranging from about 40 % to a nominal

15、62.5 %. The term “acetic acid yield” is preferred for describing what has previously been known as “acetyl value”. 5.2 Reagents 5.2.1 Sodium hydroxide solution, carbonate free, analytical reagent grade, nominal c(NaOH) = 1 mol/L. 5.2.2 Dilute sodium hydroxide solution, carbonate free, analytical rea

16、gent grade, nominal c(NaOH) = 0.5 mol/L. 5.2.3 Sulphuric acid, analytical reagent grade, nominal c(H 2 SO 4 ) = 0.5 mol/L. NOTE In order to ensure that there will be a positive back titration value in the blank the strength of the sulphuric acid (5.2.3) should be greater than that of the sodium hydr

17、oxide (5.2.1). 5.2.4 Acetone, complying with BS 509-1. 5.2.5 Phenolphthalein, a solution comprising 5 g of phenolphthalein dissolved in a litre of ethanol. BSI 2010BS 2880:1991 2 5.3 Sampling Select a representative sample following the principles embodied in BS 5309 and BS 6001. Pack the sample in

18、a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 5.4 Procedure Grind at least 2 g of the sample selected in accordance with 5.3 so that all of it will pass through a sieve with a nominal aperture size of 212 m comply

19、ing with BS 410. NOTE A beater-cross mill has been found suitable for grinding the material. Place a test portion of the ground material equivalent to about 1.5 g of oven-dry material in a w e i g h i n g b o t t l e , d r y f o r 3 h a t a t e m p e r a t u r e of 110 2 C and cool in a desiccator.

20、Stopper the bottle and weigh. Transfer the contents of the bottle to a 300 mL stoppered borosilicate glass conical flask. Reweigh the stoppered bottle and determine the mass taken by difference. Shake the test portion evenly over the base of the flask and, without lifting the flask from the bench, c

21、arefully run in 15 mL of water around the sides of the flask to ensure even distribution over the base; then add 65 mL of acetone (5.2.4). In order to prevent the formation of lumps, add the first 10 mL very slowly by pouring carefully around the sides of the flask while the flask is turned gently w

22、ithout its base leaving the bench. Allow the flask and contents to stand for 30 min and then shake for 3 h or allow to stand for between 16 h and 24 h. Add 25 mL of sodium hydroxide solution (5.2.1) slowly with continual swirling. Shake for 3 h. Wash down the stopper with water, adding approximately

23、 50 mL of water to the contents of the flask. Add 25 mL of sulphuric acid (5.2.3) and about 0.5 mL of the phenolphthalein solution (5.2.5). Allow to stand, shaking if necessary, until any signs of pink coloration have disappeared from the insoluble matter. Titrate with dilute sodium hydroxide soluti

24、on (5.2.2). Carry out a blank determination on the reagents used. 5.5 Calculation of result Calculate the acetic acid yield (in %) using the following equation: where 6 Method 4. Determination of bulk density 6.1 Principle The material is allowed to flow under fixed conditions from a prescribed funn

25、el into a measuring cylinder of predetermined mass. The density is then determined from the mass of material and its measured bulk volume. 6.2 Sampling Select a representative sample following the principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good qu

26、ality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 6.3 Procedure Carry out the determination of bulk density on the sample selected in accordance with 6.2 by the method described in BS 2782-6:Method 621A. 7 Method 5. Determination of the particle size distri

27、bution 7.1 Principle A known amount of material is separated into differing amounts of material of specified minimum particle size by progressive sieving. W is the weight of the oven-dry test portion (in g); A is the volume of sodium hydroxide solution (5.2.2) required for the test portion (in mL);

28、B is the volume of sodium hydroxide solution (5.2.2) required for the blank (in mL). BSI 2010BS 2880:1991 3 7.2 Sampling Select a representative sample following the principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tin

29、s have been used satisfactorily as moisture-proof containers. 7.3 Procedure Carry out the particle size distribution analysis on portions of the sample selected in accordance with 7.2 by the dry sieving method described in BS 1796-1 using test sieves with the following nominal aperture sizes and com

30、plying with BS 410: 850, 710, 500, 425, 355, 250, 212 and 150m. 8 Method 6. Determination of free acidity 8.1 Principle Treatment of the cellulose acetate with water and subsequent titration with sodium hydroxide solution is used to calculate the free acidity as the percentage by mass of the free ac

31、etic acid. 8.2 Sampling Select a representative sample following the principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 8.3 Procedure Carry out the determi

32、nation of free acidity using the sample selected in accordance with 8.2 by the method described in BS 2782-4:Method 459A. NOTE It is intended to dual-number ISO 1061 as BS 2782-4:Method 459A. However, at present, although this number has been allocated, the BS method has not been published and until

33、 it has, the corresponding ISO standard should be used. 9 Method 7. Determination of viscosity ratio of a 5 g/L solution at 25 C 9.1 Principle The viscosity ratio is determined as the ratio of the efflux times of the specified solution of the acetate and the pure solvent determined by a U-tube visco

34、meter. 9.2 Sampling Select a representative sample following the principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 9.3 Procedure Determine the viscosity r

35、atio using the sample selected in accordance with 9.2 by Method 733C of Part 7 of BS 2782 except that the viscometer used shall be model OC as specified in Table 1 of BS 2782-7:Method 732A. NOTE It is intended to dual-number ISO 1157 as BS 2782-7:Method 733C. However, at present, although this numbe

36、r has been allocated, the BS method has not been published and until it has the corresponding ISO standard should be used. BS 2782-7:Method 732A is identical with ISO 1628-1. 10 Method 8. Determination of viscosity at a concentration of 60 g/L 10.1 Introduction This method is widely used for viscosi

37、ty control in the manufacture of cellulose acetate and also forms the basis of most commercial cellulose acetate viscosity specifications. 10.2 Principle The viscosity of a specified solution of the acetate is determined using a U-tube viscometer. 10.3 Apparatus and materials 10.3.1 Viscometer, U-tu

38、be direct flow type (BS/U), as described in Appendix A of BS 188:1977. 10.3.2 Water bath, maintained at a temperature of 25 0.01 C. 10.3.3 Timing device, accurate to 0.1 s. 10.3.4 Solvent, a mixture of 95 mL of acetone (5.2.4) and 5 mL of distilled water. 10.4 Sampling Select a representative sample

39、 following the principles embodied in BS 5309 and BS 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 10.5 Procedure Dry a suitable quantity of cellulose acetate from the material selected in

40、 accordance with 10.4 to constant mass and dissolve 6.0 g of it by mechanical shaking in 100 mL of solvent (10.3.4). Transfer the solution to the viscometer (10.3.1). Allow the viscometer to stand in a water bath (10.3.2) maintained at 25 0.01 C for a minimum of 20 min. Determine the viscosity in ac

41、cordance with BS 188:1977 and calculate the dynamic viscosity, as described in 10.6. NOTE Infra-red weighing balances are now common in industrial laboratories and allow drying of cellulose acetate to constant mass in less than 3 min. Using this drying method the total viscosity determination takes

42、less than 2 h. BSI 2010BS 2880:1991 4 10.6 Calculation Calculate the dynamic viscosity (in mPas) using the following equation: = Ctp where 11 Method 9. Determination of viscosity at 25 % concentration at 25 C 11.1 Principle A solution is prepared from 25 parts of cellulose acetate and 75 parts (by m

43、ass) of solvent. The time for a steel ball to fall over a specified distance is measured. NOTE This test is primarily intended for cellulose acetate for use in spinning solutions. It is suitable for testing cellulose acetate which is completely soluble in the solvent (11.2.8) and which gives solutio

44、ns with falling ball times, over a specified distance, of more than 15 s when tested by the procedure given in 11.4. 11.2 Apparatus and materials 11.2.1 Glass jar, screw-capped, approximately 150 mm tall and 65 mm in diameter. 11.2.2 Water bath, thermostatically maintained at a temperature of 25 0.1

45、 C. 11.2.3 Small brass rod of known mass. 11.2.4 Thin glass plate 11.2.5 Small stainless steel container with close-fitting stainless steel lid. 11.2.6 Sighting box, about 200 mm 75 mm 75 mm, provided with vertical slits at back and front: each slit is fitted with a pair of thin horizontal wires 50.

46、0 0.4 mm apart for sighting. 11.2.7 Steel ball, 5.56 0.0025 mm in diameter, clean and free from grease. 11.2.8 Solvent, a mixture of 950 mL of acetone complying with BS 509-1 and 50 mL of distilled water. 11.3 Sampling Select a representative sample following the principles embodied in BS 5309 and B

47、S 6001. Pack the sample in a moisture-proof container. NOTE Good quality, clean, dry lever-top tins have been used satisfactorily as moisture-proof containers. 11.4 Procedure Spread thinly a test portion of the sample, ground to pass through an 850 m nominal aperture sieve complying with BS 410 and

48、equivalent to at least 200 g of oven-dry material, on paper or thin flexible aluminium sheet and dry for 3 h at a temperature of 110 2 C. Transfer to a beaker or other suitable container and allow to cool in a desiccator. Dissolve 200 g of the dried test portion in 600 mL of the solvent (11.2.8). NO

49、TE Suitable methods of dissolving test portions in the solvent are as follows. a) Mix for 4 h in a sealed contra-rotating sigma-blade mixer of approximate capacity 2 kg. b) Place approximately 300 mL of the solvent in a wide-mouth glass-stoppered bottle of approximate capacity 2 L. Add the test portion and allow to stand for a few hours. Add the remainder of the solvent and rotate the bottle at a speed of approximately 2 r/min to 6 r/min until complete solution is achieved (this should generally take not more than 24 h). Transfer part