A Model for the Oxygen Index of Plasticized Poly(Vinyl Chloride

Experimental Oxygen Index data taken on plasticized poly(vinyl chloride) systems which consisted of just poly(vinyl chloride) resin, PVC, and plasticizer are shown to obey a simple two-parameter equation for plasticizer loadings above 15 weight percent. The empirical equation is further tested using data for similar plasticized PVC compounds based on large number of commercial plasticizers and plasticizer blends. One parameter used in the equation is the Oxygen Index of the pure plasticizer determined using a simple modification of the standard Oxygen Index test procedure. The other parameter is shown to have essentially the same value for all the plasticizers tested. A detailed deriva tion of the empirical model is provided using published flame spread models adapted for the Oxygen Index test. Predictions of the Oxygen Index for the two-component (ideal) plasticized PVC compounds are within 2-3% of the ex perimentally measured values.