BS ISO 11561-1999 Ageing of thermal insulation materials - Determination of the long-term change in thermal resistance of closed-cell plastics (accelerated laboratory test methods).pdf

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1、BRITISH STANDARD BS ISO 11561:1999 Ageing of thermal insulation materials Determination of the long-term change in thermal resistance of closed-cell plastics (accelerated laboratory test methods) ICS 91.100.60BSISO11561:1999 This British Standard, having been prepared under the directionof the Secto

2、r Committeefor Materials and Chemicals, waspublished underthe authorityof the Standards Committee and comesinto effect on 15 October 1999 BSI 04-2000 ISBN 0 580 35325 7 National foreword This British Standard reproduces verbatim ISO 11561:1999 and implements it as the UK national standard. The UK pa

3、rticipation in its preparation was entrusted to Technical Committee PRI/24, Testing of rigid and flexible cellular materials, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or pro

4、posals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement inte

5、rnational or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to inc

6、lude 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 cover, page

7、s i and ii, theISO title page, pages ii to iv, pages 1 to 14 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. Amendments issued since publication Amd. No. Date Comm

8、entsBSISO11561:1999 BSI 04-2000 i Contents Page National foreword Inside front cover Foreword iii Text of ISO 11561 1ii blankBSISO11561:1999 ii BSI 04-2000 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Normative references 1 3 Definitions 2 4 Test methods General 3 5 Method A Test to determi

9、ne time-dependent change in thermal properties of core materials 4 6 Method B Simplified test to determine a design life-time thermal resistance of an unfaced product 5 7 Precision 6 8 Test report 6 Annex A (informative) Analytical model 7 Annex B (informative) Example of the determination of long-t

10、erm thermal resistance of faced products 12 Bibliography 14 Figure A.1 Relative thermal resistance of three thicknesses ofacellularplasticfoam after application of a scaling factor 9 Figure A.2 Normalized thermal resistance of two thicknesses of a rigid closed-cell plastic foam as a function of real

11、 time 10 Figure A.3 Normalized thermal resistance of two thicknesses of a rigid closed-cell plastic foam after application of the scaling factor 10 Table 1 Symbols 3BSISO11561:1999 BSI 04-2000 iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national

12、 standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. Internationa

13、l organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules

14、given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 11561 was

15、 prepared by Technical Committee ISO/TC 163, Thermal insulation, Subcommittee SC 1, Test and measurement methods. Annex A and Annex B of this International Standard are for information only.iv blankBSISO 11561:1999 BSI 04-2000 1 Introduction The purpose of this International Standard is to determine

16、 the ageing (long-term decrease in thermal resistance) of closed-cell cellular plastic materials and products which have properties that, due to diffusion of contained gases, change with time. The thermal resistance and its rate of change will vary with product variability, temperature and thickness

17、, and also within the thickness due to cross-sectional variability and the effects of natural or applied surface skins or protective facings. The long-term thermal resistance is one property required for establishing design thermal performance under service conditions and for determining life-time e

18、nergy requirements. This International Standard contains two procedures based on the conditioning of thin slices at room temperature, since conditioning at elevated temperatures can induce changes in a material other than those due to diffusion processes. The first, method A, relates to the core mat

19、erial only. An alternative, method B, is a simplified test to determine a conservative value of a design life-time thermal performance of a product. Two informative annexes provide essential background information on the ageing process and on the factors to be considered when measurements are requir

20、ed on faced products. The phenomenon and mechanisms of ageing have been known and understood for many years. The use of a blowing agent produces a relatively uniform cell size and initial high thermal resistivity. However, during the subsequent life of the foam, the principle component gases in the

21、air diffuse into the cells and this increases the cell gas pressure, effectively increasing the thermal conductivity of the gas mixtures. In addition, some of the blowing agent is absorbed by or dissolved into the polymer matrix, saturating it, while the remainder diffuses out. This inward diffusion

22、 is influenced by appropriate diffusion coefficients. These in turn are influenced by the temperature, effective cell diameter in the direction of movement of air components, and the nature of the polymer matrix. Since the diffusion of nitrogen and oxygen molecules into the cells is very much faster

23、 than the outward diffusion of the generally used larger molecule (the blowing agent), the whole ageing process is a combination of two stages: a) a primary stage (thermal drift) due to the significant rate of change of cell gas composition (usually complete within 5 years); b) a secondary stage whe

24、re air diffusion is complete but there is still very slow outward diffusion of the blowing agent (a period much greater than 10 years and estimated in some cases to be over 100 years). 1 Scope This International Standard specifies two laboratory test methods, based on slicing and scaling techniques,

25、 to determine the long-term changes in the thermal resistance of closed-cell (normally 90 %) cellular plastic materials that contain gases which, through diffusion processes, affect the properties of a foam with time. Using standard methods for the measurement of thermal resistance, method A consist

26、s of periodic measurements performed over a short time interval on thin specimens conditioned in a controlled ambient temperature environment. The results of relative change with time are used in conjunction with a mathematical technique to derive the thermal resistance of greater thicknesses of the

27、 material as a function of time. Method B describes a simple test to determine a conservative design life-time value (25 years and longer) for an unfaced, closed-cell, cellular plastic product. This method is limited currently to unfaced homogeneous materials. For this method, multiple specimens of

28、the core and surfaces of materials with variations in the slope of the primary stage thermal resistivity and a time relationship of less than 10 % within a sample are considered to be homogeneous. Generally, products with natural skins or with density deviations normally found with such products may

29、 be considered acceptable for test by this technique. 2 Normative references The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these

30、 publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred t

31、o applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 7345, Thermal insulation Physical quantities and definitions. ISO 8301, Thermal insulation Determination of steady-state specific thermal resistance and related properties Heat flow meter apparatus.

32、BSISO11561:1999 2 BSI 04-2000 ISO 8302, Thermal insulation Determination of steady-state thermal resistance and related properties Guarded hot plate apparatus. ISO 9346, Thermal insulation Mass transfer Physical quantities and definitions. 3 Terms and definitions For the purposes of this Internation

33、al Standard, the terms and definitions given in ISO 7345 and ISO9346, and the following apply. NOTEA list of symbols is given in Table 1. 3.1 ageing process by which the physical, mechanical and thermal properties of a material, product, or system change with time NOTE 1Accelerated tests can introdu

34、ce effects that will not occur during natural ageing. Care should be taken when developing such test methods and methods of evaluation of test results. NOTE 2Examples of ageing processes are the settling of some low-density fibrous materials and gas diffusion in cellular plastics. NOTE 3Whatever the

35、 process, ageing is always strongly related to the environmental or service conditions to which the material, product or system is exposed and to its shape, size and finish. Accurate prediction of ageing effects should always consider these items. 3.2 aged value value of a property of a material, pr

36、oduct or system after exposure to known environmental conditions for a specified time 3.3 accelerated aged value aged value obtained through laboratory test or through reproducible prediction models for a specified time interval and specified environmental conditions aimed at reproducing frequently

37、encountered service conditions NOTEThe actual size, working environment and expected life-time should be compared carefully with those implied in the definition of an aged value. 3.4 design life-time time interval during which an installed material, product or system should maintain its design perfo

38、rmance NOTELife-time depends upon the serviceability of the installation, for example, the design life-time for a thermal insulation material, product or system used in a building might be at least 25 years. 3.5 effective diffusion coefficient material property which relates the rate of gas transpor

39、t to the gas pressure difference across the material having a specific thickness at a specific temperature 3.6 primary stage portion of the ageing process where changes in thermal properties are influenced primarily by diffusion of gaseous components such as nitrogen and oxygen into or out of the cl

40、osed-cell material 3.7 scaling factor ratio of the squares of the product and test specimen thicknesses NOTEThis ratio represents the acceleration rate being applied to the ageing process of a cellular plastic due to thickness differences. 3.8 secondary stage portion of the ageing process where chan

41、ges in thermal properties are influenced primarily by the diffusion of blowing agents usually high molecular weight gases out of the closed-cell material 3.9 thickness of damaged surface layer (TDSL) average thickness of surface cells, on one surface, which are ruptured or otherwise damaged during p

42、reparation of the test specimen 3.10 transition point estimated age of a closed-cell cellular plastic when the ageing process changes from the primary to secondary stage NOTEThis is also called the transfer point.BSISO 11561:1999 BSI 04-2000 3 Table 1 Symbols 4 Test methods General 4.1 Conditions A

43、summary of the analytical model that serves as the basis for the slicing and scaling method is given in Annex A. The experimental procedure is based on the assumption that the material characteristics of thin specimens are equivalent to those of the material being investigated, i.e. specimens of red

44、uced thickness have the same effective diffusion coefficient and initial cell gas content as those of the full-thickness material and that one-dimensional diffusion is the dominating factor. Conditioning of full-thickness samples to obtain a service life 25 years or longer value requires too long a

45、period of testing. 4.2 Effects of influencing parameters Annex A also contains brief details of other important factors which affect the ageing process: errors due to small thickness used; thickness of damaged surface layers; ageing prior to preparation of specimen; inhomogeneities in the material;

46、high and/or inconsistent open-cell content. Symbol Quantity Unit a thermal diffusivity (thermal diffusion coefficient) m 2 /s thermal conductivity W/(mK) density kg/m 3 c p specific heat capacity at constant pressure J/(kgK) D effective gas diffusion coefficient m 2 /s D 0 effective gas diffusion co

47、efficient of a reference slab m 2 /s d thickness of specimen (slices) m d 0 thickness of a reference slab m F numerical coefficient F 0 Fourier number i day i of ageing period day n ageing period days r thermal resistivity mK/W r 0 initial thermal resistivity mK/W r t thermal resistivity of a test s

48、pecimen after time t mK/W R thermal resistance m 2 K/W R av average thermal resistance during ageing period m 2 K/W R 0 initial thermal resistance m 2 K/W R t thermal resistance of a test specimen after time t m 2 K/W R n thermal resistance on last day of ageing period m 2 K/W S scaling factor t tim

49、e day t 0 initial time day T temperature K T 1 , T 2 uniform surface temperatures of a heated or cooled slab K T m mean slab temperature K TDSL thickness of damaged surface layer mBSISO11561:1999 4 BSI 04-2000 5 Method A Test to determine time-dependent change in thermal properties of core materials 5.1 Principle Method A is a general procedure for determining change in thermal resistance at any time due to reduced conditioning time. Random samples of a cellular plastic product having a thickness greater than 25