1、BRITISH STANDARDBS EN ISO 291:2008Plastics Standard atmospheres for conditioning and testingICS 83.080.01g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g
2、36g58BS EN ISO 291:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2008 BSI 2008ISBN 978 0 580 62283 0National forewordThis British Standard is the UK implementation of EN ISO 291:2008. It supersedes BS EN ISO 291:2005 which is wi
3、thdrawn.The UK participation in its preparation was entrusted to Technical Committee PRI/21, Testing of plastics.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract.
4、Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 291May 2008ICS 83.080.01 Supersedes EN ISO 291:2005 Engl
5、ish VersionPlastics - Standard atmospheres for conditioning and testing(ISO 291:2008)Plastiques - Atmosphres normales de conditionnement etdessai (ISO 291:2008)Kunststoffe - Normalklimate fr Konditionierung undPrfung (ISO 291:2008)This European Standard was approved by CEN on 21 April 2008.CEN membe
6、rs are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application
7、to the CEN 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the sa
8、me status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Roma
9、nia, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedwor
10、ldwide for CEN national Members.Ref. No. EN ISO 291:2008: EForeword This document (EN ISO 291:2008) has been prepared by Technical Committee ISO/TC 61 “Plastics“ in collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by NBN. This European Standard shall be g
11、iven the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2008, and conflicting national standards shall be withdrawn at the latest by November 2008. Attention is drawn to the possibility that some of the elements of this document
12、 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 supersedes EN ISO 291:2005. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound
13、 to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Swi
14、tzerland and the United Kingdom. Endorsement notice The text of ISO 291:2008 has been approved by CEN as a EN ISO 291:2008 without any modification. BS EN ISO 291:2008iiiContents Page 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle. 2 5 Standard atmosphere. 2 6 Classes
15、of standard atmosphere 2 7 Standard and ambient temperatures 3 8 Procedure 3 Annex A (normative) Attainment of moisture equilibrium by plastics in a conditioning atmosphere 4 Annex B (informative) Background Information . 6 Bibliography . 8 BS EN ISO 291:2008blank1Plastics Standard atmospheres for c
16、onditioning and testing 1 Scope This International Standard sets out specifications relating to the conditioning and testing of all plastics and all types of test specimen at constant atmospheric conditions. Special atmospheres applicable to a particular test or material or simulating a particular c
17、limatic environment are not included in this International Standard. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced do
18、cument (including any amendments) applies. ISO 62, Plastics Determination of water absorption 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 standard atmosphere preferred constant atmosphere for which specific air temperature and humidity va
19、lues, as well as limit ranges for atmospheric pressure and air-circulation velocity, are specified, the air not having any significant additional constituents and the atmosphere not being subject to any significant additional radiation influences NOTE 1 Standard atmospheres permit a defined state to
20、 be attained and maintained for samples or specimens. NOTE 2 Standard atmospheres correspond to the average atmospheric conditions in laboratories and can be established in conditioning (controlled atmosphere) cabinets, chambers or rooms. 3.2 conditioning atmosphere constant atmosphere in which a sa
21、mple or test specimen is kept before being subjected to a test 3.3 test atmosphere constant atmosphere to which a sample or test specimen is exposed throughout a test 3.4 conditioning one or more operations intended to bring a sample or test specimen into a state of equilibrium with regard to temper
22、ature and humidity 3.5 conditioning procedure combination of the conditioning atmosphere and the period of conditioning BS EN ISO 291:20082 3.6 ambient temperature environmental conditions corresponding to the usual atmospheric conditions in laboratories with uncontrolled temperature and humidity NO
23、TE The phrase “at ambient temperature” refers to an environment the air temperature of which lies within a specified range, no consideration being given to relative humidity, atmospheric pressure or air-circulation velocity. In general, the air-temperature range extends from 18 C to 28 C and is stat
24、ed as “at an ambient temperature of 18 C to 28 C”. 4 Principle If a test specimen is exposed to a specific conditioning atmosphere or temperature, then a reproducible state of temperature and/or of moisture equilibrium is reached between the test specimen and the conditioning atmosphere or temperatu
25、re. It is not the intent of this International Standard to define procedures specifying how to determine sensitivity to moisture. Some materials may have special conditioning requirements. Follow the relevant International Standards. 5 Standard atmosphere Unless otherwise specified, use one of the s
26、ets of conditions given in Table 1 as the standard atmosphere. Table 1 Standard atmospheres Air temperature Relative humidity (RH) Symbol for standard atmosphere C % Remarks 23/50 23 50 Shall be used unless otherwise specified 27/65 27 65 May be used for tropical countries if agreed on by all partie
27、s NOTE The values in Table 1 apply to normal altitudes with an atmospheric pressure between 86 kPa and 106 kPa and an air-circulation velocity u 1 m/s. 6 Classes of standard atmosphere Table 2 gives the different classes of standard atmosphere corresponding to different tolerance levels for the temp
28、erature and relative humidity. The tolerances given in Table 2 apply to the specimen-storage space in a test enclosure or conditioning enclosure. Class 1 cabinets will require more frequent calibration. Follow the manufacturers recommendations for calibration. Cabinets shall be calibrated at least o
29、nce per year. BS EN ISO 291:20083Table 2 Standard atmosphere classes corresponding to different permitted deviations Permitted deviations in relative humidity (RH) % Class Permitted deviations in temperature C 23/50 27/65 1 1 5 5 2 2 10 10 NOTE Usually, the tolerances are coupled in pairs, i.e. clas
30、s 1 tolerance for both temperature and relative humidity or class 2 tolerance for both. 7 Standard and ambient temperatures If humidity has no influence or only a negligible influence on the properties being examined, the relative humidity does not have to be controlled. The corresponding environmen
31、ts are designated “temperature 23” and “temperature 27”, respectively. Similarly, if neither temperature nor humidity has any noticeable influence on the properties being examined, neither the temperature nor the relative humidity has to be controlled. In this case, the atmospheric condition is term
32、ed the “ambient temperature”. 8 Procedure 8.1 Conditioning The period of conditioning shall be as stated in the relevant specifications for the material. When the conditioning periods are not stated in the applicable standard, the following shall be adopted: a) unless otherwise specified, a minimum
33、of 88 h for atmospheres 23/50 and 27/65; b) unless otherwise specified, a minimum of 4 h for temperatures of 18 C to 28 C. NOTE 1 The length of time necessary for a plastics material to come to humidity equilibrium is in general much longer than the length of time necessary for it to come to tempera
34、ture equilibrium. NOTE 2 Samples conditioned in accordance with a) may not reach humidity equilibrium. A sufficient equilibrium is reached after conditioning longer than the time t70as defined in ISO 62. t70depends on the square of the thickness. More information about the time needed to reach equil
35、ibrium can be found in Annex A. NOTE 3 For particular tests and for plastics or test specimens that are known to reach temperature and humidity equilibrium either very rapidly or very slowly, a shorter or longer time may be specified for the conditioning period in the appropriate International Stand
36、ard (see Annex A). 8.2 Testing Unless otherwise specified, specimens shall be tested in the same atmosphere or at the same temperature in which they have been conditioned. In all cases, the test shall be carried out immediately after the removal of the specimens from the conditioning enclosure. BS E
37、N ISO 291:20084 Annex A (normative) Attainment of moisture equilibrium by plastics in a conditioning atmosphere The amount of moisture absorbed by a test specimen conditioned in an atmosphere and the rate of moisture absorption or desorption vary significantly depending on the nature and the shape o
38、f the material of which the specimen is made. The conditioning times given in 8.1 may not be satisfactory, especially in the following cases: specimen materials and specimen thicknesses that are known to reach equilibrium with their conditioning atmosphere only after a long period of time (for examp
39、le, certain polyamides and thicknesses over 2 mm, see ISO 62); unfamiliar materials, for which neither the capacity for absorbing moisture nor the time required to reach equilibrium can be estimated beforehand. In these cases, use one of the following procedures: a) Dry the material at an elevated t
40、emperature that will not significantly or permanently change the material (for many materials, a temperature of 50 C 2 C is acceptable). Allow the specimens at least 2 h to cool to the test temperature in a desiccator. State in the test report that the conditioning did not conform to ISO 291 but was
41、 a recommended alternative for special cases. b) Condition the specimens in atmosphere 23/50 until equilibrium has, to all intents and purposes, been reached. A sufficient time is the time t70at which 70 % of the water content at saturation is reached, as defined in ISO 62. If the time t70as defined
42、 in ISO 62 corresponds to a specimen of thickness d0, calculate the conditioning time t70necessary for specimens of other thicknesses using Equation (A.1): 270 7020dt td= (A.1) where t70is the conditioning time necessary; t70is the time taken for moisture equilibrium to be reached, determined in acc
43、ordance with ISO 62, with specimens of thickness d0; d is the thickness of the specimens to be conditioned in accordance with this International Standard. Mention this in the test report. c) Keep the specimens in a circulating-air oven or conditioning enclosure at a prescribed elevated temperature a
44、nd defined humidity (preferred are 50 % RH or 65 % RH) until moisture equilibrium has, to all intents and purposes, been reached (the temperature and relative humidity used shall be agreed upon by all interested parties and shall be included in the test report). Procedure a) has the disadvantage tha
45、t the values of certain properties, in particular mechanical properties, are different in the dry state from those obtained after conditioning in atmosphere 23/50. It is for this reason that this conditioning procedure does not conform to ISO 291 but is a recommended alternative. BS EN ISO 291:20085
46、In the case of procedure b), the following rule of thumb may be useful: equilibrium can be assumed to have been reached if two weighings made at an interval of d 2weeks differ by only 0,1 % (d being the thickness, in millimetres, of the specimen). Procedure c) is used when the moisture diffusion cha
47、racteristics of the polymer are known and can be used to determine appropriate exposure periods and conditions. The specimens shall be kept in the oven or conditioning enclosure until they are, to all intents and purposes, in a state of moisture equilibrium. This may be assumed to be the case when t
48、he average moisture content of the material changes by less than 0,01 % during a conditioning period of at least 1 day, determined by loss in mass as specified in ISO 62. If the moisture diffusion coefficient D is known, the time necessary for moisture equilibrium to effectively be reached is determ
49、ined using Equation (A.2) or taken as 1 day, whichever is the longer. 2702dtD=(A.2) where t70is the time taken for moisture equilibrium to effectively be reached (see ISO 62); d is the specimen thickness, in millimetres (mm); D is the moisture diffusion coefficient, in mm2/s. BS EN ISO 291:20086 Annex B (informative) Background Information B.1 General A previous edition of this International Standard ISO 291:1977, was based on ISO 554:1976, Standard atmospheres for conditioning and/or testing Specifications, prepared by ISO/TC 12
