Processing/property/structure interactions in a calcium aluminate-phenol resin composite

Abstract

Relationships among mixing conditions, extensional viscosities of the formed paste, and the morphology and flexural strength of hardened composites have been studied for a calcium aluminate cement-phenol resin composite. Mixing torque was monitored as a function of temperature and resin pH. The behavior of the torque time curves as well as ¹³C nuclear magnetic resonance and differential scanning calorimetry measurements suggest that paste formation is characterized by an induction period of flat torque, corresponding to dissolution of cement ions followed by a styffening period of rapid torque rise, corresponding to an ionic interaction between the resin and cement particles. The viscoelastic nature of the paste was studied using a biaxial squeeze flow device. The steady biaxial extensional viscosity trends with extension rate are consistent with the formation of an increasingly cross-linked bulk organic phase in the paste. Flexural strengths of hardened material processed under varying degrees of resin pH suggest that an optimal structure forms when the resin is allowed to simultaneously polymerize and ionically interact with cement particles. This conclusion is supported by evidence of scanning electron microscopy, which shows structure formation for a given cut of missing conditions.