Tetra‐Phase Compatibilization of Epoxy/Carbon Black Nanocomposites Using Hydroxyl‐Terminated Polybutadiene and Anhydride Hardeners

ABSTRACT In this study, a tetra‐phase compatibilization strategy was developed for epoxy/carbon black (CB) nanocomposites using hydroxyl‐terminated polybutadiene (HTPB) and various hardeners. Direct addition of CB caused severe aggregation and poor interfacial compatibility, resulting in degraded properties. In contrast, HTPB acted as a reactive compatibilizer when combined with anhydride hardeners, especially maleic anhydride (MAn) and phthalic anhydride (PAn). FTIR‐ATR analysis more directly supported esterification between HTPB hydroxyl groups and anhydrides, followed by epoxy–carboxylic reactions. Possible oxa‐Diels–Alder‐type interactions between HTPB vinyl groups and conjugated carbonyl‐containing functionalities on the CB surface are considered a possible secondary interfacial pathway because the relevant CC‐related absorptions could not be clearly distinguished. The thermal, mechanical, and morphological responses were strongly dependent on hardener chemistry, with the anhydride systems showing the most consistent improvement upon HTPB addition.