ISO 291:2008 download.Plastics – Standard atmospheres for conditioning and testing.
I Scope
ISO 291 sets out specifications relating to the conditioning and testing of al plastics and al types of test specimen at constant atmospheric conditions.
Special atmospheres applicable to a particular test or material or snLdating a particidar climatic environment are not included in ISO 291.
2 Normathve references
The following referenced documents are Indispensable for the application of ISO 291. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (Including any amendments) applies.
ISO 62. Pta stlcs — Oeterr,Wnat.’on of water absorption
3 Terms and definlUons
For the purposes of ISO 291, the following terms and definitions apply
3.1
standard atmosphere
preferred constant atmosphere for which specific air temperature and humidity values, as well as lEnll ranges for atmospheric pressure and air-circulation velocity, are specified, the air not having any significant additional constituents and the atmosphere not being subed to any significant additional radiation influences
NOTE I Standard atmospheres permit a defined stale to be attained and maintained Sor samples or specaTnens. NOTE 2 Standard atmospheres correspond to the average atmoephenc conditIons In laboratories and can be estatiuialed In condiboiwig (controlled atmosphere) cabinets, chanibers or rooms.
3.2
conditioning atmosphere
constant atmosphere in which a sample or test specimen Is kept before being subjected to a test
3.3
test atmosph.r.
constant atmosphere to which a sample or lest specimen is exposed llwouout a test
3.4
conditioning
one or more operations Intended to bring a sample or test specimen Into a state of equlibrium with regard to temperature and humidity
3.5
conditioning procedure
combination of the conditioning atmosphere and the penod of conditioning
3.6
ambient t.mp.rature
envwonmentai conditions corresponding to the usual abncsphenc conditions in Ial,cralories tf’ uncontrolled temperature and hum4dity
NOTE The phrase .t ambient temperata’e refers to an environment t11 air temperaltie of whict, lies withm a specitied range, no oonstdemtlon being ven to relative tsaivdIty, almoaphenc pressure or aW.cculatlon velodty. In general. the aW4ensralure range eictends from 18 t 1o28 C and is stated es at an ambent temperature of 18 C to
28 C
4 PrincIple
If a test specimen is exposed to a specific conditioning atmosphere or temporature, then a reproduddle state of temperature andior of moisture eqaIibflum is reached between the test specimen and the conditioning atmosphere or temperature
It Is not the intent of this Intemaltonal Standard to define procedures specifying how to determine sensilMty to moisture.
Some materials may have special conditioning requirements. Follow the relevant International Standards.
5 Standard atmosphere
Unless otherwise specified, use one of the sets of conditions given in Table I as the standard atmosphere.
6 Classes of standard atmosphere
Tabôe 2 gives the different classes c( standard atmosphere corresponding to different tolerance levels for the temperature and relative humidity. The tolerances given in Table 2 apply to the specimen-storage space ii a lest enclosure or condeUoning enclosure, Class 1 cabInets MI require more frequent c&abration Follow the manufacturers recommendations for calibration. Cabinets shall be calibrated at least once per yew.
7 Standard and ambient temperatures
If humidity has no Influence or only a negllgtle Influence on the properties being examined, the relative hemidity does not have to be controlled. The corresponding enwonments are designated “temperature 23” end temperature 27”, respedlvely.
Simdariy, 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 atmosphenc condition is termed the ambient temperature”
8 Procedure
8.1 CondItioning
The period of condilioring shall be as stated in the relevant specifications for the material. When the conditioning penods are not stated In the applicable standard, the following shall be adopted:
a) unless otherwise specified, a minimum of 88 h for atmospheres 23150 and 27?65:
b) unless otherwise specified, a minimum a(4 h for temperatures of 18 “C to 28 “C.
NOTE I The length of tine neceewy for a plastics material to ooine to nidey squdibrium is th gerer much longer than the length of Wne necessary for it to come to temperature eqiilrien.
NOTE 2 Samples conditioned In accordance ntth a) may not reach ISanidity equilibrium. A sufficient equllibmmi reached alter condeloning longer than the tine as defined in ISO 62. r depends on the square 01 the Iflicknass More Information about the tine needed to reach equIlibrium can be found m Annex A.
NOTE 3 For particular tests and for plastics or test specimens that are Iciown to reach temperature end hwnidity equilibrium either very rapidly or very slowly, a shorter ci longer tine may be specified Ioi the Conditioning period In the appropriate Intemationst Standard (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 inmedeately after the removal of the specimens from the conditioning enclosure.