SIST EN 16240:2014
(Main)Light transmitting flat solid polycarbonate (PC) sheets for internal and external roofs, walls and ceilings - Requirements and test methods
Light transmitting flat solid polycarbonate (PC) sheets for internal and external roofs, walls and ceilings - Requirements and test methods
EN 16240 specifies the requirements for light transmitting flat solid polycarbonate (PC) sheets for internal and external use in walls, roofs and ceilings. This European Standard applies to light transmitting flat extruded solid PC sheets of minimum thickness 2 mm, without or with uniform functional layers (e.g. coating, co-extruded layer) made from PC-based or other materials. It also specifies the test methods needed for the evaluation of conformity and marking of the sheets.
Lichtdurchlässige, flache, massive Platten aus Polycarbonat (PC) für Innen- und Außenanwendungen an Dächern, Wänden und Decken - Anforderungen und Prüfverfahren
Diese vorliegende Europäische Norm legt die Anforderungen an lichtdurchlässige, flache, massive Platten aus Polycarbonat (PC) für Innen- und Außenanwendungen an Wänden, Dächern und Decken fest.
Diese Europäische Norm gilt für lichtdurchlässige, flache, extrudierte massive Platten aus PC mit einer Mindestdicke von 2 mm, mit oder ohne gleichmäßige Funktionsschichten (z. B. Beschichtung, koextrudierte Schicht) aus PC basierten oder sonstigen Kunststoffmaterialien.
Außerdem legt sie die für die Konformitätsbewertung und die Kennzeichnung der Platten erforderlichen Prüf-verfahren fest.
Plaques d'éclairement pleines planes en polycarbonate (PC) pour toitures, bardages et plafonds intérieurs et extérieurs - Exigences et méthodes d'essai
La présente Norme européenne spécifie les exigences relatives aux plaques d'éclairement pleines planes en polycarbonate (PC) pour usage intérieur ou extérieur dans les toitures, bardages et plafonds.
La présente Norme européenne s'applique aux plaques d'éclairement pleines planes extrudées en PC d'une épaisseur minimale de 2 mm, avec ou sans couches fonctionnelles uniformes (par exemple, revêtement, couche co-extrudée) en matériaux à base de PC ou autres matières plastiques.
Elle spécifie également les méthodes d'essai nécessaires pour l'évaluation de la conformité ainsi que le marquage des plaques.
Prosojne, ploščate, masivne polikarbonatne (PC) plošče za notranje in zunanje strehe, stene in strope - Zahteve in preskusne metode
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Lichtdurchlässige, flache, massive Platten aus Polycarbonat (PC) für Innen- und Außenanwendungen an Dächern, Wänden und Decken - Anforderungen und PrüfverfahrenPlaques d'éclairement pleines planes en polycarbonate (PC) pour toitures, bardages et plafonds intérieurs et extérieurs - Exigences et méthodes d'essaiLight transmitting flat solid polycarbonate (PC) sheets for internal and external roofs, walls and ceilings - Requirements and test methods91.060.20StreheRoofs91.060.10Stene. Predelne stene. FasadeWalls. Partitions. Facades83.140.10Filmi in folijeFilms and sheetsICS:Ta slovenski standard je istoveten z:EN 16240:2013SIST EN 16240:2014en,de01-februar-2014SIST EN 16240:2014SLOVENSKI
STANDARD
SIST EN 16240:2014
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 16240
December 2013 ICS 83.140.10; 91.060.10 English Version
Light transmitting flat solid polycarbonate (PC) sheets for internal and external use in roofs, walls and ceilings - Requirements and test methods
Plaques d'éclairement pleines planes en polycarbonate (PC) pour usage intérieur ou extérieur dans les toitures, bardages et plafonds - Exigences et méthodes d'essai
Lichtdurchlässige, flache Massivplatten aus Polycarbonat (PC) für Innen- und Außenanwendungen an Dächern, Wänden und Decken - Anforderungen und Prüfverfahren This European Standard was approved by CEN on 5 October 2013.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 16240:2013 ESIST EN 16240:2014
EN 16240:2013 (E) 2 Contents Page
Foreword .4 Introduction .5 1 Scope .6 2 Normative references .6 3 Terms, definitions and symbols .7 3.1 Terms and definitions .7 3.2 Symbols .8 4 Requirements .9 4.1 Visual appearance .9 4.2 Dimensions and mass per unit area and their tolerances .9 4.3 Spectral characteristics . 10 4.4 Total solar energy transmittance . 10 4.5 Impact resistance. 11 4.6 Durability . 12 4.7 Deformation behaviour . 14 4.8 Airborne sound insulation . 14 4.9 Thermal transmittance . 14 4.10 Water vapour permeability . 16 4.11 Water/air tightness. 16 4.12 Linear thermal expansion . 16 4.13 Reaction to fire . 16 4.14 External fire performance . 16 4.15 Resistance to fire . 16 4.16 Net heat of combustion . 17 4.17 Presence of functional layers . 17 4.18 Release of dangerous substances . 17 4.19 Resistance to fixings . 17 4.20 Temporary protective coverings . 17 5 Test and calculation methods . 17 5.1 Dimensional tolerances and mass per unit area . 17 5.2 Artificial ageing . 20 5.3 Yellowness index . 21 5.4 Small hard body impact resistance . 21 5.5 Deformation behaviour . 22 5.6 Airborne sound insulation . 23 5.7 Reaction to fire . 23 6 Assessment and verification of constancy of performance – AVCP . 27 6.1 General . 27 6.2 Product type determination . 27 6.3 Factory production control (FPC) . 28 6.4 Initial inspection of factory and of FPC . 30 6.5 Continuous surveillance of FPC . 31 7 Marking and labelling . 31 Annex ZA (informative)
Clauses of this European Standard addressing the provisions of the EU Construction Products Regulation . 33 SIST EN 16240:2014
EN 16240:2013 (E) 3 ZA.1 Scope and relevant characteristics . 33 ZA.2 Procedure for AVCP of light transmitting flat solid polycarbonate sheets . 36 ZA.2.1 Systems of AVCP . 36 ZA.2.2 Declaration of performance (DoP) . 38 ZA.3 CE marking and labelling. 42 Bibliography . 45
SIST EN 16240:2014
EN 16240:2013 (E) 4 Foreword This document (EN 16240:2013) has been prepared by Technical Committee CEN/TC 128 “Roof covering products for discontinuous laying and products for wall cladding”, the secretariat of which is held by NBN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2014, and conflicting national standards shall be withdrawn at the latest by June 2014. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 16240:2014
EN 16240:2013 (E) 5 Introduction This document describes the requirements for light transmitting flat solid PC sheets for internal and external use in walls, roofs and ceilings. It is applicable to the sheets for the delivery only. Reference should be made to national regulations and manufacturer literature for requirements concerning the design, storage and fundamental guidance for installation of sheets, including all safety aspects. The standards and guideline addressing light transmitting flat solid PC sheets for building applications are the following: — EN 1873, Prefabricated accessories for roofing — Individual roof lights of plastics — Product specification and test methods (harmonized standard) — EN 14963, Roof coverings — Continuous rooflights of plastics with or without upstands — Classification, requirements and test methods (harmonized standard) — EOTA ETA-Guideline 010, Self supporting translucent roof kits The flat solid PC sheets that satisfy the requirements of this document are suitable for use as components in accordance with EN 1873, EN 14963 or ETAG 010. SIST EN 16240:2014
EN 16240:2013 (E) 6 1 Scope This European Standard specifies the requirements for light transmitting flat solid polycarbonate (PC) sheets for internal and external use in walls, roofs and ceilings. This European Standard applies to light transmitting flat extruded solid PC sheets of minimum thickness 2 mm, without or with uniform functional layers (e.g. coating, co-extruded layer) made from PC-based or other materials. It also specifies the test methods needed for the evaluation of conformity and marking of the sheets. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1990:2002, Eurocode - Basis of structural design EN 1873:2005, Prefabricated accessories for roofing - Individual roof lights of plastics - Product specification and test methods EN 13501-1, Fire classification of construction products and building elements - Part 1: Classification using test data from reaction to fire tests EN 13501-2, Fire classification of construction products and building elements - Part 2: Classification using data from fire resistance tests, excluding ventilation services EN 13501-5, Fire classification of construction products and building elements - Part 5: Classification using data from external fire exposure to roofs tests EN 13823, Reaction to fire tests for building products - Building products excluding floorings exposed to the thermal attack by a single burning item EN 14500:2008, Blinds and shutters - Thermal and visual comfort - Test and calculation methods EN 14963:2006, Roof coverings - Continuous rooflights of plastics with or without upstands - Classification, requirements and test methods EN ISO 178:2010, Plastics - Determination of flexural properties (ISO 178:2010) EN ISO 472:2013, Plastics - Vocabulary (ISO 472:2013) EN ISO 527-1:2012, Plastics - Determination of tensile properties - Part 1: General principles (ISO 527-1:2012) EN ISO 527-2, Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics (ISO 527-2) EN ISO 717-1, Acoustics - Rating of sound insulation in buildings and of building elements - Part 1: Airborne sound insulation (ISO 717-1) EN ISO 1043-1:2011, Plastics - Symbols and abbreviated terms - Part 1: Basic polymers and their special characteristics (ISO 1043-1:2011) SIST EN 16240:2014
EN 16240:2013 (E) 7 EN ISO 1716, Reaction to fire tests for products - Determination of the gross heat of combustion (calorific value) (ISO 1716) EN ISO 4892-2:2013, Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc lamps (ISO 4892-2:2013) EN ISO 6603-1, Plastics - Determination of puncture impact behaviour of rigid plastics - Part 1: Non-instrumented impact testing (ISO 6603-1) EN ISO 6946, Building components and building elements - Thermal resistance and thermal transmittance - Calculation method (ISO 6946) EN ISO 10140-1:2010, Acoustics - Laboratory measurement of sound insulation of building elements - Part 1: Application rules for specific products (ISO 10140-1:2010) EN ISO 10140-2, Acoustics - Laboratory measurement of sound insulation of building elements - Part 2: Measurement of airborne sound insulation (ISO 10140-2) EN ISO 10140-4, Acoustics - Laboratory measurement of sound insulation of building elements - Part 4: Measurement procedures and requirements (ISO 10140) EN ISO 10140-5, Acoustics - Laboratory measurement of sound insulation of building elements - Part 5: Requirements for test facilities and equipment (ISO 10140-5) EN ISO 11664-1, Colorimetry - Part 1: CIE standard colorimetric observers (ISO 11664-1) EN ISO 11664-2, Colorimetry - Part 2: CIE standard illuminants (ISO 11664-2) EN ISO 11925-2, Reaction to fire tests - Ignitability of products subjected to direct impingement of flame - Part 2: Single-flame source test (ISO 11925-2) EN ISO 12572, Hygrothermal performance of building materials and products - Determination of water vapour transmission properties (ISO 12572) ISO 11359-2, Plastics - Thermomechanical analysis (TMA) - Part 2: Determination of coefficient of linear thermal expansion and glass transition temperature ETAG 010, Self supporting translucent roof kits 3 Terms, definitions and symbols 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in EN ISO 472:2013, EN ISO 1043-1:2011 and the following apply. 3.1.1 PC sheet flat extruded sheet substantially made of polycarbonate polymer to which are added those additives to facilitate the manufacture of sheet conforming to the requirements of this standard and customer requirements Note 1 to entry: Additives can be e.g. lubricants, processing aids, UV absorbers, colorants, functional layers and/or flame retardants. Note 2 to entry: There is a distinction between a coloured sheet containing colorants and an uncoloured sheet having a coloured functional layer or paint on the external surfaces. SIST EN 16240:2014
EN 16240:2013 (E) 8 3.1.2 indirect test IT test performed by the manufacturer, different from that specified for that particular characteristic, having verified its correlation with the specified test 3.1.3 sheet length dimension of a sheet in the extrusion direction Note 1 to entry: It is expressed in millimetres. 3.1.4 sheet width dimension of a sheet perpendicular to the extrusion direction Note 1 to entry: It is expressed in millimetres. 3.2 Symbols For the purposes of this document, the symbols and the relevant subclauses are given in Table 1. Table 1 — Symbols Symbols Term/definition Relevant subclause d1 Flatness across the sheet width 5.1.8 d2 Flatness across the sheet width 5.1.8 Ef Flexural modulus 4.7 and 5.5.2 g Total solar energy transmittance 4.4 h Overall sheet thickness 4.9 and 5.5.3
he External heat transfer coefficient 4.4 and 4.9 hi Internal heat transfer coefficient 4.4 and 4.9 Lsp Length of a test specimen 5.1 m Mass of a test specimen 5.1.5; 5.1.6 qi Secondary internal heat transfer factor 4.4 Rse External surface resistance 4.9 Rsi Internal surface resistance 4.9 RT Total thermal resistance
4.9 Rw (C;Ctr) Sound reduction index 4.8; 5.6 U Thermal transmittance 4.9 Ws Sheet width 5.1 YI Yellowness index 4.6.1.2 and 5.3 . Linear thermal expansion 4.12 .e Solar direct absorbance 4.4 / Water vapour permeability 4.10 ûY Variation of yellowness index 4.6.1.2 and 5.3
Design thermal conductivity 4.9
Poisson's ratio 4.7 SIST EN 16240:2014
EN 16240:2013 (E) 9 a Mass per unit area
5.1.5 e Solar direct reflectance 4.4 1M Tensile stress at yield 4.7 and 5.5.3 2e Solar direct transmittance 4.4 2e,n-h Normal-hemispherical solar transmittance (see 4.3, NOTE 1). 4.3 2v Light transmittance 4.3 2v,n-h Normal-hemispherical light transmittance (see 4.3, NOTES 1 and 2).
4.3 4 Requirements 4.1 Visual appearance The sheets shall have regular, smooth or patterned surfaces. There shall be no scratches, marks or other defects larger than 4 mm2 each anywhere on the sheet surface. There shall be no obvious bubbles, inclusions, cracks, depressions or other defects anywhere in the sheets that could adversely affect the performance of the sheets in its intended application. The edges of the sheet shall be straight and cut cleanly. The colour distribution shall be visually uniform, unless otherwise specified. For specific uses, further requirements concerning the visual aspects of the sheets might be considered. 4.2 Dimensions and mass per unit area and their tolerances The dimensional tolerances and mass per unit area shall be assessed when subject to regulatory requirement. When tested in accordance with the test methods specified in 5.1.1 to 5.1.8, the dimensional tolerances and mass per unit area of the sheets shall conform to the requirements given in Table 2. The test methods given in Table 2 are used for initial type testing, and are the reference test methods. Table 2 — Requirements for dimensions and mass per unit area and their tolerances Characteristic Test method Requirement Sheet thickness 5.1.4 The nominal sheet thickness of the sheet shall be declared in millimetres. The sheet thickness at any point shall not vary by more than: – ± 5 % of the declared nominal sheet thickness for nominal sheet thickness greater or equal to 2 mm and up or equal to 5 mm. – ± 10 % of the declared nominal sheet thickness for nominal sheet thickness greater than 5 mm. For sheets with patterned surfaces, the sheet thickness is the overall thickness of the sheet. Mass per unit area 5.1.5 The nominal mass per unit area of the sheet shall be declared in grams per square metre. The mass per unit area of a sheet shall be not less than 95 % of the declared nominal mass per unit area. SIST EN 16240:2014
EN 16240:2013 (E) 10 Sheet length and width 5.1.6 The sheet length/width shall be within the interval from 0 % to +0,30 % of the declared sheet length/width. Deviation from rectangular shape (only for rectangular sheets) 5.1.7 The difference between the lengths of the two diagonals of the sheet shall be less than 0,35 % of the width of the sheet or 2 mm, whichever is the higher. Sheet flatness
5.1.8 The deviation from flat across the width of the sheet shall be ≤ 3 mm per metre of width. The deviation from flat along the length of the sheet shall be ≤ 3 mm per metre of length. 4.3 Spectral characteristics The spectral characteristics of solid PC sheets shall be assessed when subject to regulatory requirement. The spectral characteristics of a solid PC sheet include the luminous and solar characteristics, and the reflection and transmission characteristics. The solid PC sheets are defined by their thickness, colour, texture and functional layer(s). A change of one of these characteristics affects the spectral characteristics of a solid PC sheet. The spectral characteristics shall be measured according to EN 14500 considering the samples cut from solid PC sheets as thick translucent samples (for the definition of thick translucent samples, see EN 14500:2008, 6.3.2). For accurate measurements, the sphere diameter should be much larger than the diameter of the light entrance port. The sphere diameter should be greater or equal to 1 000 mm and the entrance diameter equal to 100 mm. NOTE 1 The normal-hemispherical light transmittance, 2v,n-h, and the normal-hemispherical solar transmittance, 2e,n-h, as designated in EN 14500 are corresponding respectively to the light transmittance, 2v, and the solar direct transmittance, 2e, as designated in EN 410. NOTE 2 The normal-hemispherical light transmittance, 2v,n-h, is corresponding to the total luminous transmittance, 2D65, as stated in EN 1873:2005 and ETA-Guideline 010. The normal-normal light transmittance, 2v,n-n, should be determined according to EN 14500, where relevant. Test samples shall be clean and dry, unless otherwise specified. The storage and the cleaning procedures stated by the manufacturer shall be followed. The spectral characteristics, i.e. the light transmittance, 2v, and the solar direct transmittance, 2e, shall be declared and subsequent measurements shall be within ± 3 absolute value (or units) of the declared values. EXAMPLE For a declared value of the light transmittance equal to 40 %, the actual light transmittance of a sheet may be included between 37 % and 43 %. 4.4 Total solar energy transmittance The total solar energy transmittance of solid PC sheets shall be assessed when subject to regulatory requirement. The total solar energy transmittance of flat solid PC sheets shall be measured when subject to outdoor uses. The total solar energy transmittance, g, is given by Formula (1): ieqg+=τ (1) SIST EN 16240:2014
EN 16240:2013 (E) 11 where 2e is the solar direct transmittance; qi is the secondary internal heat transfer factor. NOTE 1 Formula (1) comes from EN 410:2011, 5.4.1. The optical factors, i.e. the solar direct transmittance, 2e, and the solar direct reflectance, e, are measured physical characteristics (see 4.3). In the case of a flat solid PC sheet having an emissivity greater than 0,8, the secondary internal heat transfer factor, qi, is given by the Formula (2): iieeihqhhα=+ (2) where .e is the solar direct absorbance; he is the external heat transfer coefficient, in watts per square metre Kelvin; hi is the internal heat transfer coefficient, in watts per square metre Kelvin. For solid PC sheets, the standard values for he and hi are 25 W/(m2„K) and 7,7 W/(m2„K), respectively. The relation between the optical factors is given by Formula (3); 1eeeτρα++= (3) where .e
is the solar direct absorbance; 2e
is the solar direct transmittance; e
is the solar direct reflectance. NOTE 2 The value of heat transfer coefficient towards the outside corresponds to summer conditions. NOTE 3 Formula (2) comes from EN 410:2011, 5.4.6.2 and Formula (3) comes from EN 410:2011, 5.4.2. 4.5 Impact resistance 4.5.1 Small hard body impact resistance The small hard body impact resistance shall be assessed when subject to regulatory requirement. The small hard body impact resistance shall be evaluated by determining the impact behaviour according to 5.4. Failure occurs when a crack or a break appears on the test specimen. White discolorations are not considered as cracks. SIST EN 16240:2014
EN 16240:2013 (E) 12 When ten test specimens taken from three sheets are submitted to the test, no failure shall occur. 4.5.2 Large soft body impact resistance The resistance to large soft body impact depends very heavily on the method of installation and the roof system into which the light transmitting sheet is incorporated, rather than a property of the sheet itself. The large soft body impact resistance of the same product is likely to be different when the same product is used in different roofing systems and/or installed with different methods of installation, and therefore cannot be declared for a particular product. In the absence of an appropriate European test method for sheets, the manufacturer may declare the method of installation for each application, which shall consider the large soft body impact resistance. The manufacturer shall assess the large soft body impact resistance separately in accordance with ETAG 010, EN 1873, EN 14963 or individual national safety requirements for each such application. The test report shall record the test method and the manufacturer's instructions for the installation. NOTE At the date of publication of this document, the following national safety requirements have been identified: DS 1133:1987 [1] and ACR[M]001:2005 [2]. The user should not assume that the large soft body impact resistance for any one application shall apply to any other application or method of installation. 4.6 Durability 4.6.1 Solid PC sheets for external use 4.6.1.1 General The durability shall be assessed when subject to regulatory requirement. The durability of the solid PC sheets shall be demonstrated by testing after artificial ageing the variation of the yellowness index and the light transmittance with the same level of radiant exposure in the total daylight and declaring the results according to 4.6.1.2. 4.6.1.2 Classification according to the radiant exposure The exposure to artificial ageing shall be carried out in accordance with 5.2 using one of the classes given in Table 3. SIST EN 16240:2014
EN 16240:2013 (E) 13 Table 3 — Artificial ageing classification Class Radiant exposure in the total daylight range (300 nm to 2 500 nm) GJ/m2 Uncoloured sheets Coloured sheets Variation of yellowness index Variation of light transmittance Variation of yellowness index Variation of light transmittance ûYI absolute value (or unit) û 2v % ûYI absolute value (or unit) û 2v % ûA ûD ûE ûF 18 18 10 10 ≤ 10 Not applicable ≤ 10 Not applicable ≤ 5 Not applicable ≤ 10 Not applicable ≤ 10 ≤ 20 a ≤ 10 ≤ 20 b ≤ 5 ≤ 10 a ≤ 10 ≤ 10 b a A coloured sheet made from the same mC resin as an uncoloured sheet classified ûA and having the same UV protection shall be classified ûD without further testing. b A coloured sheet made from the same mC resin as an uncoloured sheet classified ûb and having the same rs protection shall be classified ûF without further testing. In the case of an exposure to a radiant exposure greater than 18 GJ/m2, the actual value may be declared by the manufacturer to allow the customer to determine the suitability of the sheets to exposure in areas where the conditions are particularly severe. EXAMPLE An uncoloured sheet, with the following characteristics: — YI = 2 before ageing and YI ≤ 12 after ageing: ûYI ≤ 10 — 2v = 80 % before ageing and 2v ≥ 75 % after ageing: û2v ≤ 5 % is classified ûA. 4.6.1.3 Variations of yellowness index and light trans
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