BS 4745:1990 pdf free.Method for Determination ofthermal resistance oftextiles.
BS 4745 Cut circular test specimens of diameter 330 mm,avoidingcreases and folds. Precondition them by laying them flat in thestandard atmosphere for testing textiles (see clause 7) for 24 h.where possible,test three specimens of each sample.
Procedure Two methods are specified below.The first of these, the two-plate method,is normally used for materials which,when inuse, are shielded from the ambient air,e.g. a blanket whencovered by a bedspread. The second , the singleplate method,is normally used for materials which,when in use, have theirouter faces exposed to the ambient air (e.g. bedspreads andouter-wear garments).The two-plate method is the preferredone on accuracy and reproducibility grounds, however , and it isrecommended that this method be used for all materials.
Lay the conditioned test specimen on the hot plate of the ap-paratus and place the cold plate gently on top of it, taking carenot to compress the surface of the test specimen. Shield theedges from the air-flow,e.g. by wrapping a strip of wovenblanket or masking tape round the apparatus. Switch on the electric heaters and adjust the temperature con-troller so that T2 registers a temperature within the range 304 Kto 308 K. Maintain a steady state of temperature at each of thethermocouple sites T, Tand T3 for a period of not less than30 min before considering a test to be completed, and ensurethat the fluctuations in the various temperature levels do notexceed 0,1 K throughout this period.
As in the method described in 9.1，lay the conditioned testspecimen on the hot plate (with the edges shielded) but leaveits outer face uncovered and place the cold plate underneaththe apparatus. Support the cold plate, e.g. by three corks,toallow air circulation and cover with a circular piece of hardboard or metal sheet to the upper face of which a sheet of aluminium foil has been stuck in order to shield the cold platefrom the radiant heat emitted by the apparatus.T is now usedto measure the air temperature.BS 4745 pdf download.