Abstract

Mixtures of polyethylene oxide (PEO) and sodium thiocyanate (NaSCN) were isothermally crystallized at temperatures between 7 and 37° C, below the eutectic temperature Te=63° C. The stable phases are semicrystalline polyethylene oxide, SPEO, and a crystalline complex, CC, with the formula PEO3 NaSCN; these two solids grow by different mechanisms. Salt mole fraction was varied between 0.067⩽X⩽0.143 for studies by optical microscopy and differential scanning calorimetry. Solidification was observed to proceed by primary growth followed by coupled growth at a nonequilibrium composition X′e much greater than the equilibrium eutectic composition Xe=0.026. The boundaries of this skewed coupled zone could not be determined because of a dependence of X′e on the nature of the primary phase.

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