Polymer films, flammability testing

A third test often cited, Oxygen Index (O.I.) is an ASTM test which measures the flammability of the base polymers. The flammability of the polymer film may alone differ significantly from the flammability of the same polymer on a nonwoven substrate. Theoretically, the higher O.I. for a sample film, the higher its nonflammability. 

Preparation of Samples for Flammability Testing. Samples of the phosphorus containing terepolymers and of the polymer blends were converted to film by compression molding on a Carver Laboratory Press with electrically heated platens. The films were prepared at 250°C and 20,000 lb. pressure, using a 10 mil thick frame mold. Samples (2" x 1/4") were cut from this film for flammability testing. 

Ester interchange between the additive and polymer would be expected if the mixture were held for an excessive time in the melt. In order to avoid the potential for interchange, the blendings were conducted in solution and heated only for a time necessary to melt press films for flammability testing. An alternative method of film preparation by solvent casting of films was discarded due to difficulties in preparing uniform, sufficiently thick, solvent free films for evaluation. 

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