Some interesting polyacetylenes present unstable behaviour because of their reactivity with oxygen, among them, poly(2-hexyne). This paper is a continuation of a previous work, where models for oxidation and chain scission processes of this polymer were proposed. Here, the model of oxidation has been applied to a sample of poly(2-hexyne) with different molecular weight, to examine its effect on the parameters of the model, including the activation energy of oxidation and volatilization processes. The effect of a radical scavenger (N-phenyl-alpha-naphtylamine) on poly(2-hexyne) stabilization has also been examined. A modified model of oxidation including this effect and an equation to predict the lifetime of poly(2-hexyne) films with antioxidant have been proposed.