Heat resistance test parameters

In an ideal situation the parameters used to define furniture should be ignition resistance and the rate of generation of heat, smoke and toxic gases. Tests to do this with actual or mock-up full sized furniture are not yet available as final specifications but the Nordtest (28) and NBS furniture calorimeters (29) represent scientific methods while room/ corridor rigs, typically UK DOE PSA FR5 and 6 of 1976 (5) (6) were originally used but are less satisfactory from a scientific point of view. The Californian (30) and Boston tests (31) for public area furniture are essentially simple room tests and are similar in principle to DOE, PSA, FR5 and 6 although the latter do not have pass/fail criteria. Bench scale rate of heat release tests include the NBS cone (29) which, with a code of practice represent a possible alternative but the rate of burning of... 

The inner dimensions of the test furnace are 1.0 m (W) X 2.7 m (L) X 2.3(H) and the radiant tube is equipped horizontally. The W-type radiant tube has a total length of 8055 mm and a diameter of 7 inches (outer diameter is 194 mm and inner diameter is 177 mm). The material of the radiant tube is heat resistant cast steel (SCH24). The thermocouple positions is welded on the outside surface of the tube along the length and the tube circumference. The operation parameters in the tests are each 500- 900°C for furnace temperature, 20-100% firing rate and 1.15 to 1.50 for excess air ratio. 

It is obvious that the scaling resistance of the heat-resisting steels will be detrimentally influenced by any other corrosion mechanism which may be destroying the oxide layer, e.g., by chemical reactions with other metal oxides, chlorine, or chlorides. Thus in general, the heat resistance cannot be characterized by a single test method or measuring parameter but will depend on the speciflc environmental conditions. 

The free carrier optical reflection of test modules before and after damp heat indicates that the effective carrier density is not much affected [58]. Hence, the degradation of the ZnO sheet resistance is probably more of a carrier transport problem. It is, at present, unclear where electron barriers are located. They may be present at the grain boundaries in general [59]. In this case, the disturbances of the ZnO microstructure (induced by the substrate but also depending on preparation parameters) are only harmful because they allow a faster penetration of the humidity into the film. On the other hand, the disturbed regions may themselves be highly resistive after damp heat exposure, which forces the current to percolate around these... 

In general, heat sealable packs are not resealable once opened, hence they are inherently tamper-evident and tamper-resistant. Certain cold seal materials may be resealable, hence they do not comply with this parameter. Child-resistance properties are less easy to confirm, as the standard varies between countries. In the USA materials have to meet the test created via the PPA (Poisons Prevention Act 1970), in Germany DIN 55559, and the UK BSI7236 1989. 

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