Binary (1:1 by weight) and ternary (1:1:1 by weight) blends of polyethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and Nylon 6 (PA 6) as well as the homopolymers are extruded as strips and ultraquenched from the melt. After zone drawing and additional annealing at Ta = 220 or 240 °C for 5 or 25 h with fixed ends in vacuum, the samples are studied by DSC, WAXS, solubility, and mechanical testing. It is found that all components in the blends are oriented and perfection of the structure is observed at T, = 220 °C. At T, = 240 °C isotropization of PBT and PA 6 takes place in their blends with PET, the orientation of the latter being preserved; i.e., microfibrillar reinforced composites are obtained. Their mechanical properties are comparable to those of glass fiber reinforced PBT and PA 6. During prolonged thermal treatment, in addition to isotropization, chemical interactions (additional condensation and exchange reactions) take place at the interfaces, resulting in the formation of copolycondensates playing the role of compatibilizers. The initially multiblock copolymers randomize with the progress of annealing, losing their crystallization ability, as proved by DSC, WAXS, and solubility measurements. Finally, the entire amounts of PBT and PA 6 become involved in the copolymers, converting in this way the starting homopolymer matrix of the microfibrillar reinforced composite into a copolymer one. This change in the chemical composition affects the overall behavior of the composites.

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Cold drawn poly(ethy1ene terephthalate) (PETP) fibres are subjected to zone annealing or isothermal annealing with fixed ends. The morphological changes taking place during both types of thermal treatment are followed by means of SAXS, WAXS, birefringence and density measurements, DSC, and mechanical tests. Differences in the supermolecular structure ofthe samples subjected to zone annealing and those annealed with fixed ends are established. Zone annealing results in better definition of the basic structural elements, higher orientation and larger number oftaut tie molecules which in turn predetermine the higher performance of the zone annealed material. Polv(etli~~letiterepphthalat)-Fasern tnir verbesserten tnechanischen EigenschaftenKalt gereckte Poly(ethylenterephtha1at)-Fasern wurden einer Zonentemperung beziehungsweise einer isothermen Temperung mit fixierten Enden unterworfen. Die bei beiden Arten der thermischen Behandlung auftretenden morphologischen Anderungen wurden durch Rontgenkleinwinkel-und Rontgenweitwinkelstreuung, Doppelbrechungs-und Dichtemessungen, Differential-Scanning-Calorimetrie sowie mechanische Priifungen untersucht. Es wurden Unterschiede in der ubermolekularen Struktur der unterschiedlich getemperten Proben gefunden. Die Zonentemperung ftihrt zu einer besseren Herausbildung der Basisstrukturelemente, hoherer Orientierung und grol3erer Zahl von gespannten Verbindungsmolekulen, was bessere mechanische Eigenschaften des zonengetemperten Materials mit sich bringt.

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