Investigation of Thermal Aging of Polyamide 4,6 by¹H Solid‐State NMR

Abstract

Abstract The thermal aging of polyamide 4,6 was investigated by DSC, SEM, WAXS, and 1 H solid‐state NMR. Phase composition, chain mobility, morphology, and domain sizes were determined as a function of aging time. Proton transverse magnetization relaxation was measured at low resonance frequency, 1 H wide‐line NMR spectra and 1 H spin‐diffusion experiments were made at high resonance frequency. The NMR investigation shows that the aging process affects the rigid (crystalline), semi‐rigid (crystalline/amorphous interface), and the mobile (amorphous) fraction of polyamide 4,6. The amount of rigid (crystalline) fraction increases by about 10% upon aging at 200 °C for 1 000 h at the expense of the interfacial fraction. Chain mobility in crystalline phase is reduced upon aging suggesting perfections of the crystalline order. magnified image