Properties of oligomers present in poly(ethylene terephthalate)

Abstract

Heat treatment of polyester yarns induces the selective crystallization of the cyclic trimer [(GT)3] in the form of polygonal solids on the fiber surfaces. At the temperature studied, namely, 200°C, the diffusion rate of (GT)3 appears to be very rapid. Small quantities of the cyclic tetramer were also found. The total extractable oligomer content of the samples is reduced considerably after annealing at 200°C, mainly due to solid phase polymerization. Exposure to methylene chloride vapor also causes cyclic oligomers to diffuse to the fiber surface. The migration of (GT)3 is again very rapid. Larger cyclics also diffuse to the surface in appreciable quantities. Solvent exposed samples, unlike annealed ones, exhibit irregular crystal shapes and sizes on their surfaces. The moisture regain of the extracted oligomers is less than that of the polyester. It is suggested that this is due to the oligomers being in a crystalline form.