Structural Development of PEN/PET Blend Film during Drawing at High Temperature
Syozo MURAKAMI, Elinor L. BEDIA and Shinzo KOHJIYA@
Abstract:Structural, thermal and mechanical properties of the blend of poly(ethylene naphtalate) [PEN] and poly(ethylene terephtalate) [PET] were investigated using 1H nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and tensile testing machine. The PEN/PET blends were obtained by melt blending (mixing for 2 min at 310Ž and quenching with ice water). Structural formation in unoriented amorphous (50/50) PEN/PET blend films during drawing at 85Ž, 100Ž and 130Ž was studied by In Situ X-ray measurements, and the results were discussed by comparing with those of PEN and PET themselves. PEN in blend films was partially miscible with PET partly due to the formation of copolymers by transesterification during blending. This miscibility is estimated from the findings, that is, the blend film exhibited a single glass transition temperature (Tg) and the Tg increased linearly with increasing PEN content. The heat of crystallization by cold-crystallization and the heat of fusion by melting were the lowest value in (50/50) PEN/PET blend film among the blends. The (50/50) blend showed the highest degree of transesterification ( ca. 6 %). The tensile stress at the yield point and the tensile modulus of PEN/PET blend films increased with increasing PEN content. Though PET film could not be drawn above 100Ž at a lower drawing rate, PEN/PET blend films was drawable. In (50/50) PEN/PET blend film crystallization proceeded gradually with the drawing at 100Ž which was under Tg (117Ž) of PEN. The crystallization was evidenced by the ƒ¿-form crystalline reflection of PEN which was detected by In Situ X-ray measurements. Key Words:PEN/PET blends, Transesterification, Mechanical properties, Oriented crystallization, In Situ WAXD measurement