NEW ROUTES TO POLYETHYLENE TEREPHTHALATE WITH IMPROVED MECHANICAL-PROPERTIES

Two-stage cold drawing with each stage followed by high temperature annealing was used to prepare high performance polyethylene terephthalate (PET). By this means a very high draw ratio (λ = 20) is achieved at room temperature. The different supermolecular structures in the materials with λ = 5 and λ = 20 are measured by means of SAXS and WAXS. Mechanical and thermal treatments give rise to an alternating structure in PET with λ = 5 and to an almost parallel extension of the macrochains in the absence of alternation in PET with λ = 20. This difference in the supermolecular structure affects the mechanical behaviour of the two materials: the samples with λ = 20 have double the tensile strength (0.60 against 0.26 GPa) and elasticity modulus (18.6 against 11.5 GPa) of those with λ = 5. © 1990.