1、BRITISH STANDARD BS7344:1990 Specification for Reeled low density polyethylene film for general purpose applicationBS7344:1990 This British Standard, having been prepared under the directionof the Plastics StandardsPolicyCommittee, waspublished under the authorityof the Board of BSI andcomes into ef
2、fect on 31 August1990 BSI07-1999 The following BSI references relate to the work on this standard: Committee referencePLM/40 Draft for comment89/39138DC ISBN 0 580 18752 7 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics Standard
3、s Policy Committee (PLM/-) to Technical Committee PLM/40, upon which the following bodies were represented: British Plastics Federation Engineering Equipment and Materials Users Association Furniture Industry Research Association Her Majestys Stationery Office Institute of Trading Standards Administ
4、ration Ministry of Defence PIRA Packaging and Industrial Films Association Amendments issued since publication Amd. No. Date CommentsBS7344:1990 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Composition 1 4 Appearance and finish 1 5 Con
5、ditioning of test specimens 1 6 Dimensional tolerances 1 7 Classification 2 8 Marking 3 Appendix A Additional properties to be agreed between purchaser and manufacturer 4 Appendix B Specimen orientation for the determination of gloss 4 Appendix C Method to determine resistance to opening of blocked
6、polyethylenelayflat tubular film 4 Appendix D Common trade abbreviations 4 Figure 1 General arrangement for determination of resistance toopeningofblocked layflat tubular film 5 Figure 2 Common trade abbreviations 5 Table 1 Spot thickness and average thickness tolerances 2 Table 2 Yield tolerance fo
7、r a consignment of reels 2 Table 3 Classifying properties 3 Table 4 Additional properties 4 Publications referred to Inside back coverBS7344:1990 ii BSI 07-1999 Foreword This British Standard has been prepared under the direction of the Plastics Standards Policy Committee. It is based on Defence Sta
8、ndards93-13/Issue1 and93-20/Issue1 and the Packaging and Industrial Films Association Voluntary Standard4/80. The most important optical properties of polyethylene film, with respect to clarity and appearance, are haze and gloss which have therefore been classified, together with other basic physica
9、l characteristics. With this type of classification it may be possible to assemble on paper a combination of properties that is impossible to obtain with the present state of technology. A purchaser wishing to use this specification for the first time will probably find it necessary to contact mater
10、ial suppliers to learn what materials are commercially available. After establishing which material meets his requirements the purchaser may subsequently specify the material by the appropriate designation. It is important that there are discussions between the manufacturer and the purchaser concern
11、ing other properties of the film. A list of additional properties which may be agreed between the purchaser and the manufacturer, together with their methods of test, is given in Appendix A. Useful common trade abbreviations are given in Appendix D for information. A British Standard does not purpor
12、t 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 confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cov
13、er, pagesi andii, pages1 to6, 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 in the amendment table on the inside front cover.BS7344:1990 BSI 07-1999 1 1 Scope This British Standard specifies
14、 unprinted low density (k 927kg/m 3 ) polyethylene film in the form of sheet or layflat tubing, excluding coextrusions, in the thickness range25m to300m, available in widths up to2m (i.e.up to4m centre folded). It includes tolerances on the length, width, weight and thickness of the film, and a clas
15、sification system covering certain basic physical characteristics. This standard excludes special films. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the following definitions apply. 2.1 y
16、ield area of film per unit mass NOTEAverage thickness is inversely proportional to yield. 2.2 haze percentage of transmitted light which, in passing through the specimen, deviates from the incident beam by forward scattering. For the purposes of this standard, only light flux deviating by more than2
17、.5 is considered to be haze 2.3 gloss ten times the percentage of an incident light beam collected at135 to the plane of the film, when the incident beam strikes the film at an angle of45 . The gloss value is expressed in“gloss units” 2.4 clarity a function of gloss and haze properties NOTESee Table
18、 3. 2.5 opacity a function of light transmission; the lower the opacity, the higher the light transmission NOTESee Table 4. 3 Composition The polyethylene film shall be manufactured from a base material consisting of polyethylene, or a copolymer in which ethylene is the major constituent. Polyethyle
19、ne film intended for the exclusion of light and for maximum resistance to weathering shall be manufactured from a base material containing sufficient finely dispersed carbon black to give the film a light transmittance of less than1% (seeAppendix A). When determined by BS2782:Method823A the numerica
20、l rating of the carbon black dispersion shall be5 or less. NOTEThe material may contain stabilizers, pigments or other additives. For compositions and raw material requirements seeBS3412. 4 Appearance and finish The film shall be in the form of sheet or layflat tubing. NOTE 1The film may be supplied
21、 folded in any form if agreed between the purchaser and the supplier. NOTE 2The film should have an appearance conforming with that produced by good commercial practice. It should be as free from gels, streaks, pinholes, foreign matter or undispersed raw material as is commercially possible. There s
22、hould be no visible defects such as holes, tears and blisters. NOTE 3The film may be treated to promote adhesion if required by the purchaser, e.g.corona surface treatment. 5 Conditioning of test specimens All samples shall be conditioned at23 2 C for not less than1h before testing or the measuremen
23、t of dimensions, and all testing and measurement shall be carried out at23 2 C. Polyethylene films are insensitive to changes in the relative humidity of the atmosphere and there is no necessity for the preconditioning of samples to a standard relative humidity. 6 Dimensional tolerances 6.1 Length T
24、he length of film on a reel shall be at least the stated length. NOTE 1Where a number of short length reels are supplied the number in any consignment should be subject to agreement between supplier and customer. In cases of dispute the length shall be determined in accordance with BS2782:Method632A
25、. NOTE 2For routine testing any method shown to give accurate results may be used to determine the length. Reels shall contain no more than one break or join per1000m of film. Any such breaks or joins shall be identified by suitable marks on tags visible on the outside of the reel.BS7344:1990 2 BSI
26、07-1999 6.2 Width The average width of the film shall be within the following deviations from the stated width. Tubular film and edge-slit film: In cases of dispute the width shall be determined in accordance with BS2782:Method632A. NOTEFor routine testing any method shown to give equivalent results
27、 may be used. 6.3 Thickness 6.3.1 Spot thickness When tested in accordance with BS2782:Method630A, individual spot thickness measurements shall comply with the spot thickness tolerances given in Table 1. Sufficient test strips shall be taken from a reel to allow a minimum of20 measurements to be mad
28、e and at least two test strips shall be tested. 6.3.2 Average thickness When tested in accordance with section 1 of BS2782:Method631A:1982, the average thickness measurements on specimens from a reel shall comply with the average thickness tolerances given in Table 1. In cases of dispute and for pig
29、mented material the density shall be determined in accordance with BS2782:Method620D. NOTEFor routine testing of unpigmented film the density may be taken as920kg/m 3 . Table 1 Spot thickness and average thickness tolerances 6.4 Weight The net weight of film on a reel shall be at least the stated we
30、ight. 6.5 Yield of a consignment of reels When tested in accordance with section 2 of BS2782:Method631A:1982, the yield of reels in a consignment shall comply with the relevant yield given in Table 2. In cases of dispute and for pigmented film, the density shall be determined in accordance with BS27
31、82:Method620D. NOTE 1For routine testing of unpigmented film the value for density used in the calculation may be taken as920kg/m 3 . Table 2 Yield tolerance for a consignmentofreels NOTE 2In the plastics film industry the term yield (in m 2 /kg) is commonly used. It may be calculated as shown in se
32、ction 2 of BS2782:Method631A:1982, or from the following equation: Yield 7 Classification 7.1 The classification system given in7.2, in which the polyethylene film is classified according to its form, its density and various attributes, shall be used. 7.2 The classification system shall consist of t
33、he following elements given in the order presented, with each element separated by a comma: a) the number and date of this British Standard; b) the form and description of the material; c) classifying properties as coded in Table 3. 7.3 An example of a complete classification is as follows. Layflat
34、tubing (T), not coloured (N) surface treated for special properties (P) with an unspecified impact strength (O), a coefficient of kinetic friction of0.35(2) and high clarity(3) would have the following classification: BS7344:1990, TNP, 023. up to and including250mm width 5mm above250mm width 2% Trim
35、med film: up to and including350mm width 5mm above350mm width 1.5%. Range in which nominal thickness falls Spot thickness tolerance on specimens Average thickness tolerance on specimens m 25 to100 101 to200 201 to300 % 20 15 10 % 10 7.5 5 Range in which nominal thickness falls Tolerance for the yiel
36、d of reels in consignmentscontaining 1 reel 2 to25 reels 26 to50 reels 51 and above m % % % % 25 to100 101 to200 201 to300 10 7.5 5 7.5 5 3 5 3 2 3 2 2 where t is the average thickness (in m); p is the density (in g/cm 3 ). S Sheet T Tubing N Natural/not coloured C Coloured (including white and blac
37、k not intended for classification B below) B Black for exclusion of light and maximum resistance to weathering P P Surface treated for special properties; Yield 1000 tp - =BS7344:1990 BSI 07-1999 3 8 Marking Each reel or pallet shall be marked with the following information: a) the name and/or trade
38、 mark of the manufacturer; b) the full classification of the material 1)as described in clause7; c) the nominal thickness; d) the width, length and net weight of the film; e) the batch number and/or order number, or other suitable means of identification. Table 3 Classifying properties 1) Marking BS
39、7344:1990 on or in relation to a product represents a manufacturers declaration of conformity, i.e.a claim by or on behalf of the manufacturer 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. Suc
40、h a declaration is not to be confused with third party certification of conformity, which may also be desirable. Property Code Test method Minimum impact strength a(in g/m) Unspecified 3.5 0 1 2 3 BS2782:Method352D Coefficient of kinetic friction Unspecified 0.50 (low slip) 0 1 2 3 BS2782:Method824A
41、 b Clarity Unspecified, or coloured film 0 Method515A of BS2782:1970 for haze c Clarity Haze Gloss Low Medium High % 15 8 to15 65 1 2 3 Method515B of BS2782:1970 for gloss d a Impact strength can vary depending upon whether it is measured at the fold, or within the body of, the film. b The coefficie
42、nt of kinetic friction should be measured after a suitable conditioning period, normally a period of more than24h after manufacture. c The haze value is the mean of the readings taken on four specimens of film. d See Appendix B for specimen orientation. BS7344:1990 4 BSI 07-1999 Appendix A Additiona
43、l properties to be agreed between purchaser and manufacturer Table 4 lists a selection of properties which the purchaser may wish to specify. Relevant test methods are included in Table 4. Table 4 Additional properties Appendix BSpecimen orientation for the determination of gloss The gloss value of
44、a specimen is the mean of the four readings obtained with the sample perpendicular to the plane of the incident and reflected beams and with the following orientations: a) the front surface of the film towards the incident beam and the machine direction of the film parallel to the plane of the incid
45、ent and reflected beams; b) the front surface of the film towards the incident beam and the transverse direction of the film parallel to the plane of the incident and reflected beams; c) the back surface of the film towards the incident beam and the machine direction of the film parallel to the plan
46、e of the incident and reflected beams; d) the back surface of the film towards the incident beam and the transverse direction of the film parallel to the plane of the incident and reflected beams. Appendix CMethod to determine resistance to opening of blocked polyethylene layflat tubular film C.1 Te
47、st specimen Cut three test specimens from the film under test with the assistance of a template120 5mm long and50 1mm wide. NOTEThe width of the template is the same as that of the platens described inC.2. C.2 Procedure Carry out the test at a temperature of20 5 C. Place the test specimen symmetrica
48、lly between two flat platens50 1mm square and12.5 2.5mm thick, which may be made of any rigid material that will not warp, e.g.polymethylmethacrylate or aluminimum. Take care to prevent premature separation of the components of the specimen. Separate the layers of film outside the area of the platen
49、s and secure the four lengths of film thus obtained by means of spring clamps or pressure sensitive adhesive tape to the platens, as indicated in Figure 1 so that there is no slack length of film. Place the assembly of platens and test specimen on a flat surface and place a load on the assembly such that the total force on the test specimen is9.8 0.5N. Connect the upper platen to a sensitive load measuring device (see note) and the lower platen to a dri
