THE OXIDATIVE STABILIZATION AND CARBONIZATION OF A SYNTHETIC MESOPHASE PITCH .1. THE OXIDATIVE STABILIZATION PROCESS

The transformation of mesophase pitch to an ordered carbon by high-tem perature heat treatment in an inert atmosphere must be preceded by a s uitable period of thermosetting or oxidative stabilization. The chemic al process of oxidative stabilization is not well characterized, altho ugh research has clearly indicated that the oxidation history of the m esophase has a profound impact on the mechanical qualities of the resu ltant carbon product. In this study, we oxidized samples of a commerci ally available, synthetic mesophase pitch to determine the effect of d ifferent time/temperature profiles of oxidation on the quantity and ty pe of introduced functionality. Fourier transform infrared spectroscop y (FT-IR) was used to characterize and quantify oxygen functionality p resent in this oxidized pitch. The oxidation process was characterized by periods of weight gain and weight loss. It was concluded that weig ht gain during oxidation involves the loss of aliphatic content in the pitch, with a concurrent increase in oxygen content as predominately ester and anhydride functionality. Weight loss is characterized by a l oss of aromatic carbon content from the pitch and a further increase i n the relative oxygen content in the pitch. It was discovered that cha nging the time/temperature profile of oxidation affects the pitch prim arily via the degree of weight gain and weight loss experienced, rathe r than through the introduction of specific functionality-with weight gain dominating at lower oxidation temperatures and shorter time perio ds, and weight loss dominating at higher temperatures and longer perio ds of oxidation. We conclude by suggesting mechanisms of derivatizatio n to explain the oxidative stabilization of this synthetic, naphthalen e-derived mesophase pitch in an oxygen-rich atmosphere.