1、BRITISH STANDARD BS5270-1: 1989 Bonding agents for use with gypsum plasters and cement Part1: Specification for polyvinyl acetate (PVAC) emulsion bonding agents for indoor use with gypsum building plasters UDC691.178:665.939.57:678.744.422:691.55:666.91:620.1BS5270-1:1989 This British Standard, havi
2、ng been prepared under the direction of the Adhesives Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 31 October 1989 BSI 03-1999 First published January 1976 The following BSI references relate to the work on this standard: Committee refere
3、nceADC/10 Draft for comment87/51811DC ISBN 0 580 17078 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Adhesives Standards Policy Committee (ADC/-) to Technical CommitteeADC/10, upon which the following bodies were represented: British
4、 Adhesives and Sealants Association British Ceramic Research Ltd. British Ceramic Tile Council British Floor Covering Manufacturers Association British Plastics Federation British Railways Board British Resin Manufacturers Association Cement Admixtures Association Contract Flooring Association Cork
5、Industry Federation Department of the Environment (Building Research Establishment) FeRFA Gypsum Products Development Association Mastic Asphalt Council and Employers Federation National Federation of Plastering Contractors Plastics and Rubber Institute Amendments issued since publication Amd. No. D
6、ate of issue CommentsBS5270-1:1989 BSI 03-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Composition 1 3 Solids content 1 4 Saponification value 1 5 Acid value 1 6 Ash residue 1 7 Low-temperature film formation capability 1 8 Bond strength 1 9 Marking 1 Append
7、ix A Determination of solids content 2 Appendix B Determination of saponification value 2 Appendix C Determination of acid value 3 Appendix D Determination of ash residue 4 Appendix E Low-temperature film formation test 5 Appendix F Determination of bond strength 5 Publications referred to Inside ba
8、ck coverBS5270-1:1989 ii BSI 03-1999 Foreword This revision of this Part of BS5270 has been prepared under the direction of the Adhesives Standards Policy Committee. BS5270 was first published in1976 and was based on established characteristics of PVAC homopolymers of known composition. This present
9、 edition of BS5270 is to be published in two Parts. Part1 supersedes BS5270:1976 which is withdrawn. The subject matter is the same as in the previous edition but there is greater emphasis on performance requirements. A requirement for low-temperature film formation capability, and a corresponding m
10、ethod of test, replace those for film flexibility given in the earlier edition. Coverage rates for different types of surface are now specified, and the procedures used in the method of test have been made clearer and more precise. The proposed Part2 is expected to cover bonding agents for cement re
11、ndering and screeding for both dry and intermittently wet service conditions. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself con
12、fer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated
13、in the amendment table on the inside front cover.BS5270-1:1989 BSI 03-1999 1 1 Scope This Part of BS5270 specifies composition and performance requirements for vinyl acetate homopolymer emulsion bonding agents, substantially unfilled, for indoor use with gypsum building plasters. Bonding agents spec
14、ified are intended for use with plasters complying with ClassB, types b.1 and b.2 of BS1191-1 and typea.3of BS1191-2. NOTE 1The bonding agents may also be used with other plasters that are recommended by the manufacturer for use on backgrounds treated with bonding agents. NOTE 2The titles of the pub
15、lications referred to in this standard are listed on the inside back cover. 2 Composition The bonding agent shall consist primarily of an emulsion of vinyl acetate homopolymer. NOTEThe bonding agent may contain such additives as are necessary to meet the performance requirements of this standard. 3
16、Solids content The solids content of the bonding agent before it is diluted for use shall be not lower than the minimum value stated by the manufacturer, when tested in accordance with Appendix A. The solids content of the bonding agent when diluted for use shall be such that, when applied to the su
17、rfaces shown, the corresponding minimum dry coating masses obtained per unit area are as follows: 4 Saponification value The saponification value of the non-volatile component of the bonding agent shall be between575mg and652mg of potassium hydroxide per gram of film, when determined in accordance w
18、ith Appendix B. 5 Acid value The acid value of the non-volatile component of the bonding agent shall not exceed10mg of potassium hydroxide, when determined in accordance with Appendix C. 6 Ash residue The ash residue of the bonding agent shall not exceed2% by mass, when determined in accordance with
19、 Appendix D. 7 Low-temperature film formation capability The bonding agent shall produce a continuous film, when tested in accordance with Appendix E. 8 Bond strength The adhesive bond shall be stronger than the cohesive strength of the plaster. When tested in accordance with Appendix F, at least se
20、ven out of nine test areas shall break within the plaster (seeF.3.3) and no test area shall break at a stress of lower than230kN/m 2 . 9 Marking Each container shall be clearly marked with the following information: a) the words “(Name of product) complying with BS5270-1:1989 1) ”; b) the name or tr
21、ade mark of the manufacturer: c) the number of the manufacturers batch or other identification unit of production; d) the minimum solids content, expressed as a percentage by mass; e) instructions for storage, including temperature limits; f) instructions for use, including coverage recommendations,
22、 in square metres per litre, that give the minimum dry coating masses per unit area on low-, moderate- and high-suction surfaces (seeclause3); g) the date by which the contents shall be used. 60g/m 2 bonding coat on a low-suction surface 40g/m 2 bonding coat on a moderate suction surface 15g/m 2 sea
23、ling coat, followed by 40g/m 2 bonding coat on a high-suction surface NOTEExamples of surfaces having different degrees of suction are given in BS5492. 1) Marking BS5270-1:1989 on or in relation to a product represents a manufacturers declaration of conformity, i.e.a claim by or on behalf of the man
24、ufacturer that the product meets the requirements of the standard. The accuracy of the claim is therefore solely the responsibility of the person making the claim. Such a declaration is not to be confused with third party certification of conformity, which may also be desirable.BS5270-1:1989 2 BSI 0
25、3-1999 Appendix A Determination of solids content A.1 Principle A known mass of the bonding agent is weighed into an aluminium dish and heated in an oven at110C for1h. It is then cooled and reweighed to determine the mass of solid remaining. NOTEFor some materials it may not be possible to dry to co
26、nstant mass under these conditions. A.2 Apparatus A.2.1 A laboratory balance, capable of weighing to the nearest0.1mg. A.2.2 Aluminium dishes, of50mm diameter, mass approximately1g, with aluminium covers. A.2.3 A thermostatically controlled oven, complying with BS2648, capable of being controlled at
27、110 2 C. A.2.4 A glass desiccator, with silica gel desiccant. A.2.5 A glass rod. A.3 Procedure Place a clean, dry, marked aluminium dish(A.2.2) and its cover in the oven(A.2.3) set at110 2 C for15 min. Allow to cool in the desiccator(A.2.4), then weigh the dish and its cover to the nearest0.1mg. Sti
28、r the sample of bonding agent in its container with a clean glass rod (A.2.5) to ensure that it is homogeneous. Then, using the rod to assist pouring, pour1.5g to2.0g of the bonding agent into the dish. Cover the dish immediately and weigh the dish and its contents to the nearest0.1mg. NOTEThe dish
29、should be weighed as speedily as possible to avoid errors due to evaporation of water or solvents. Remove the cover, tilt the dish to distribute the contents over the whole area of the base of the dish and transfer the dish and contents to the oven. Heat for1h at110 2 C. Remove the dish from the ove
30、n, cover and allow to cool in the desiccator. Weigh the dish and contents to the nearest0.1mg. Duplicate this procedure using a fresh portion of the sample. If the results of the two determinations do not agree to within1% of the mass before drying, repeat the determinations with a fresh sample. A.4
31、 Expression of results The solids content (D), expressed as a percentage by mass of the sample, is given by the following equation: where Take as the final result the mean of duplicate determinations that differ by not more than1% of the mass before drying. Appendix B Determination of saponification
32、 value B.1 Principle The bonding agent in the form of a dry, thin film is refluxed for a period in an alkaline solution. The residual mixture is then titrated with hydrochloric acid solution. B.2 Reagents B.2.1 General. The reagents used shall be of recognized analytical grade. Water complying with
33、grade3 of BS3978 shall be used throughout. B.2.2 Alcoholic potassium hydroxide solution, c (KOH)=approximately1.0mol/L. B.2.3 Hydrochloric acid, standard volumetric solution, c(HCl)=approximately1.0mol/L. B.2.4 Phenolphthalein, 10g/L solution in ethanol95% (V/V). B.3 Apparatus B.3.1 A conical flask,
34、 capacity250mL. B.3.2 A burette, capacity50mL, complying with BS846. B.3.3 A glass condenser, complying with BS5922. B.3.4 An electric hot plate. B.3.5 A pipette, capacity25mL, complying with BS1583. B.3.6 A flat, glass plate, of approximate size350mm 350mm. m 0 is the mass of the dish and cover (in
35、g); m 1 is the mass of the dish, cover and test sample before drying (ing); m 2 is the mass of the dish, cover and test sample after drying (ing). D m 2 m 0 m 1 m 0 - 100 =BS5270-1:1989 BSI 03-1999 3 B.3.7 A laboratory balance, capable of weighing to the nearest0.1mg. B.3.8 A constant temperature an
36、d humidity cabinet, capable of being controlled at23 2 C and505%r.h. NOTEConstant temperature and humidity cabinets complying with either BS3718 or BS3898 are suitable. B.4 Preparation of film sample Spread the bonding agent onto a flat, glass plate(B.3.6) over an area of about1 000cm 2 . The amount
37、 of bonding agent needs to be sufficient to give approximately5g of film when dried. Allow the plate to dry in a horizontal position in the constant temperature and humidity cabinet(B.3.8) for at least18h at23 2 C and505%r.h. Then scrape off sufficient film to provide the dried film. NOTEIf the bond
38、ing agent has a solids content lower than about35% or if it has a low viscosity, it may be necessary to increase the area over which the film is spread. B.5 Procedure Follow the procedure in duplicate and perform a duplicate blank test at the same time. Weigh to the nearest1.0mg approximately0.7g of
39、 the dried film obtained as described inB.4 into the previously tared250mL conical flask(B.3.1). Pipette(B.3.5)20mL of the alcoholic potassium hydroxide solution(B.2.2) into the flask and fit the flask for reflux. Reflux the mixture for4h to5h, then cool and wash down the condenser(B.3.3) with water
40、. Remove each flask and titrate the contents with the hydrochloric acid solution(B.2.3) using the phenolphthalein(B.2.4) as indicator. Average the results of the duplicate sample determinations if they differ by not more than12mg of potassium hydroxide per gram of film. If the difference is greater
41、than this, repeat the determinations until results differing by not more than12mg of potassium hydroxide per gram of film are obtained. Average the results of the duplicate blank determinations if they differ by not more than0.2mL of hydrochloric acid solution. If the difference is greater than this
42、, repeat the determinations until determinations differing by not more than0.2mL of hydrochloric acid solution are obtained. NOTEIf the concentrations of both the potassium hydroxide solution and of the hydrochloric acid solution are1.0mol/L, a difference of0.1mL in the volume of hydrochloric acid s
43、olution used in the titration will be equivalent to5.61mg of potassium hydroxide. B.6 Expression of results The saponification value (S), expressed as the number of milligrams of potassium hydroxide required to saponify1g of the film, is given by the equation: where Calculate the mean of the results
44、 of the duplicate determinations that differ by not more than12mg of potassium hydroxide per gram of film. Appendix C Determination of acid value C.1 Principle The bonding agent, in the form of a dry, thin film, is dissolved in ethanol and the resulting solution is then titrated with sodium hydroxid
45、e solution. C.2 Reagents C.2.1 General. The reagents used shall be of recognized analytical grade. Water complying with grade3 of BS3978 shall be used throughout. C.2.2 Sodium hydroxide solution, c (NaOH)=approximately0.01mol/L. C.2.3 Ethanol 95% (V/V), complying with BS507 and made neutral to pheno
46、lphthalein indicator. NOTEDepending on the nature of the PVAC in the bonding agent, it may be necessary to dilute the ethanol with up to35% (V/V) of water in order to effect solution. C.2.4 Phenolphthalein, 10g/L, solution in ethanol95% (V/V). C.3 Apparatus C.3.1 A stoppered conical flask, capacity2
47、50mL. C.3.2 A burette, capacity10mL, complying with BS846. C.3.3 A measuring cylinder, capacity100mL, complying with BS604. C.3.4 A laboratory balance, capable of weighing to the nearest0.1mg. V 0 is the average volume of the hydrochloric acid solution used for the blanks (inmL); V 1 is the average
48、volume of hydrochloric acid used in the determinations (inmL); T is the exact concentration (in mol/L) of HCl in the hydrochloric acid solution(B.2.3); m is the mass of the dried film (ing). S 56.1 V 0 V 1 ()T m - =BS5270-1:1989 4 BSI 03-1999 C.4 Preparation of film sample Prepare a film as describe
49、d inB.4. C.5 Procedure Weigh to the nearest0.1mg about1g of dried film into the previously tared conical flask(C.3.1). Add70mL of the ethanol(C.2.3) from the measuring cylinder(C.3.3) and, if necessary, warm gently to obtain a clear solution. Titrate with the sodium hydroxide solution(C.2.2) using the phenolphthalein solution as indicator(C.2.4). Perform a duplicate determination. If the results of the duplicate determinations do not agree to within0.12mg of potassium h
