Effect of annealing on thermal properties and crystalline structure of polyamides. Nylon 12 (polylaurolactam)

Summary Thermal and crystalline behaviour of nylon 12 annealed at low supercooling for 10–2500 hours were studied by DSC, SAXS, WAXS and electron microscopy. The melting temperature and the heat of melting increased on annealing time and temperature from 174 °C and 10 cal/g to 187 °C and 23 cal/g, and at the same time the long period was enhanced from 80 to 160 Å. Long time annealing caused a partial transformation of the-crystal structure to the-crystalline modification.Annealed nylon 12 consisted typical folded chain spherulites of increased latteral dimensions.The extrapolated heat of meltingH _m ^* of the crystalline phase of nylon 12 in the-form is 50 cal/g.With 9 figures