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September, 1952
61
A TEST TO MEASURE THE FLAMMABILITY OF KINEMATO GRAPH SAFETY FILM
R. W. Pickard, B.Sc. * and D. Hird, B.Sc. *
TI
'HE work described in this note was carried out at the request of British Standards Institution Technical Committee CME/6. Its purpose was to investigate the relative fire hazard of various types of safety film marketed to-day with other comparable cellulosic materials in common use.
Development of Apparatus
Some preliminary work was carried out to compare the fire hazard of safety film
GRADUATED SCALE.
In the light of these results it was considered that if a specimen of safety film were mounted in a semicircular form, and ignited at one end, it would continue to burn to a point which would be characteristic of the particular type of film. This may be explained by considering the heat transfer between the flame and the film. The flame front continues to advance provided the film directly in front of the flame is heated to its ignition temperature. Initially, when the flaming is takift*
~^-4
Fig. 1.
Apparatus for tests
on 35 mm. film.
with the known hazard of nitrate film. To do this, a length of 35 mm. safety film was mounted vertically and its lower end ignited. It was found that the flame spread upwards over most types of safety film. However, if the upper end of the specimen were ignited, in no experiment did the flame spread downwards. Nitrate film subjected to the same test permitted the spread of flame in either direction.
Manuscript received July 23, 1952.
place on the section of film which is vertical or nearly vertical, the film directly in front of the flame is heated by convection and radiation from the flame. As the flame front advances towards the horizontal section of the film the contribution of heat from the flame decreases since the angle between the plane of the flame and the film increases. A point may therefore be reached at which the heating received by the film from the flame is insufficient for burning to continue.
* Department of Scientific & Industrial Research and Fire Offices' Committee Joint Fire Research
Organization.