Abstract
The development of crystal phase and properties of uniaxially drawn poly(butylene terephthalate) films depended on the processing conditions. PBT films of 11% crystallinity were drawn at 50, 80, 100, 120 and 15$0^{\circ}C$ and the films drawn at 5$0^{\circ}C$ were heat-set at 120, 150, 180, and 20$0^{\circ}C$. The resulting samples were studied by WAXD results suggested that only $\beta$-form crystla, $\alpha$/$\beta$-form crystals, and $\alpha$-form crystal was formed at drawing temperatures of 50/8$0^{\circ}C$, 100/12$0^{\circ}C$, and 15$0^{\circ}C$, respectively. Therefore, an increase in heat setting temperature caused an increase in the $\alpha$-form crystal content. Dynamic viscoelastic analysis showed that the tan $\delta$$_{max}$ corresponding to the glass transition of the PBT films decreased with the drawing temperature. But, the tan $\delta$$_{max}$ did not change significantly with the heat setting temperature. The initial modulus of the films increased when the $\beta$-crystal content was increased, but the tensile strength depended more on the $\alpha$phase content, i. e., the total crystallinity.ity.