Microstructural development of a vitrified hindered phenol compound during thermal annealing

Structural changes in vitrified 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) during the annealing process were studied by DSC, WAXD and FT-IR. The initial AO-80 is highly crystalline, whereas AO-80 obtained by cooling from its melting state is an amorphous material. Annealing treatments below the melting point of AO-80 resulted in structural development. In addition, the modification of the crystal formed by annealing treatment depended on the annealing conditions. The IR spectra of various crystal modifications were different. Analysis of the microstructures of the crystals that formed indicated that the crystal formed by annealing at 100 °C is a smectic crystal, whereas the crystal formed by annealing at 80 °C is a nematic crystal. The AO-80 crystal formed within the chlorinated polyethylene (CPE) matrix during annealing at 100 °C is also a nematic crystal. Though the CPE matrix decreased regularity of AO-80 crystals, it raised the growth rate of AO-80 crystals.