Development of a pendant experiment using melt indexer for correlation with the large-size dripping in the UL-94 test

The dripping phenomena affect fire hazards significantly. In the UL-94 test, the dripping has been classified into the small-size dripping due to surface melting and the large-size dripping originating from bulk softening. Both types of dripping result from the gravity resisted by the forces including the viscous force. Based on the mechanical mechanism, a pendant experiment to reflect the ability of polymer melt to resist the gravity and a simple model equation were developed. The pendant experimental data of 7 polymers verified the model equation, and the regressed model parameter values of activation energy were close to reported data to some extent for most polymers. Correlations between the predicted pendant mass and the dripping behavior featured by the maximum drop mass showed that the pendant mass predicted at the glass transition temperature was proportional to the maximum drop mass. For polymers of large-size dripping, the pendant mass predicted at typical decomposition temperatures such as the onset decomposition temperature was generally proportional to the maximum drop mass. Moreover, the model equation indicated that for the large-size dripping the product of drop mass and first dripping time should be proportional to the specimen thickness, which was verified by reported dripping data.