Recommendations for the use of the cone calorimeter is published as a draft for development DD 246:1999
This guidance document is being issued in the Draft for Development series of publications as it is of a provisional nature because techniques, applications and software for the use of the cone calorimeter are still being developed. However the topics discussed are of considerable importance and help to users. It covers a wide range of important practical details and suggestions for using the cone. It is essential reading for anyone using or contemplating using the cone for whatever reason. This draft was prepared by FSH 21 of the BSI.
The first part of DD 246 covers the following topics: capability and limitations of the cone, recommended calibration procedures, test specimen preparation and presentation along with the selection of the heat flux and ignition protocols.
The second area of guidance in DD 246 is the testing of non-standard products, for example non-planar products, thermally mobile specimens including those that intumesce and those which retreat from the heat source, non-homogeneous products and finally specimens with a short test duration. It also explains how to test liquids both with and without the radiant heater.
The next section of DD 246 discusses the theory of oxygen consumption calorimetry. This discussion deals with issues such as the effect of incomplete combustion on the calculations. It also calculates, for a typical polysiloxane, the deviation from the 02 "rule". Similar changes to the calculation are to be expected when silicone oils and rubbers are burnt in the cone. Finally, there is an important section devoted to the presentation of data. After outlining the requirements set out in the current standards (e.g. ISO 5660, BS 476 Part 15 etc.) and pointing out some of the consequences of these measurements, in that full use is not made of all the data collected, the section includes a sub-section on additional useful data that can be obtained. This is followed by some detailed recommendations on what provisions there should be in the software used to process data to enable the user to maximise his understanding.
The draft concludes with two annexes. The first deals with radiation transfer considerations and is illustrated graphically. The second is also an important annex and is devoted to the effect of additives and fillers - which is sometimes misunderstood. Concern has been shown where fillers and additives are present that the oxygen depletion work gives erroneous heat release measurements. Calculations are given for three different plastics based on PMMA, firstly, with an added inert filler, secondly PMMA with a filler, which undergoes an endothermic phase change with no mass loss, and lastly PMMA with a filler undergoing an endothermic reaction with the loss of water. In each case the results are given in tabular form for the data presented in three mass related ways to give an understanding of the effect of additives.
Thus DD 246 is a very timely publication in a field which is still changing.
The draft can be purchased from Customer Services, BSI Tel: 44(0) 20 8996 9001 or by Fax: 44(0) 8996 7001.