Summary: | 博士 === 國立成功大學 === 化學工程學系碩博士班 === 98 === Spherulite morphology of poly(octamethylene terephthalate) (POT) and poly(nonamethylene terephthalate) (PNT) in thin-film or three dimensional forms, were characterized using polarized versus non-polarized optical microscopy, scanning electron microscopy (SEM), wide-angle X-ray (WAXD) analysis, and transmission electron microscopy (TEM). POT can simultaneously display solely one type of spherulite or dual types of spherulites (double-ring-banded and ringless ones), depending on Tc or Tmax imposed. Fractions of these two types depend on Tc when quenched from a fixed Tmax = 160oC. At lower Tc’s, POT exhibits higher crystallization rates leading to higher fractions of ringless spherulites; at higher Tc’s, POT exhibits lower crystallization rates leading to ring-banded spherulites.
Three types of spherulites (labeled: Type-0, 1, and 2) are possible in PNT when crystallized at wide range of crystallization temperature (Tc); however, only two of the three types can coexist in PNT at a given Tc. At lower Tc (lower than 55oC), the spherulites in PNT are either of Type-0 (appearing ringless in POM) or Type-2 (double-band in POM). When crystallized at 55oC or higher, the morphology is featured with Type-1 (single-ring-banded in POM) spherulites as the majority species that co-exist with Type-2 spherulites as imbedded minority. By comparison, the rod-like lamellae in the double-banded spherulites (Type-2) are longer and thicker, and more ordered than those in the single-banded spherulites (Type-1).
Morphology of crystallized spherulites in PNT in bulk forms, instead of thin-film forms, was investigated. Ring textures were found to exist on the fractured surfaces or microtomed films from bulk PNT samples. By further SEM and TEM examinations, the fracture surfaces and microtomed films from the interior of the bulk display similar ring-banded patterns as those in thin films cast on glass slides. Although the cast PNT thin films in two-dimensional growth are known to display both Type-1 ring bands as majority and Type-2 ring bands as minority, this study further shows that the interior of PNT bulk exhibits mainly Type-1 (single rings with narrower spacing than Type-2) ring bands, and Type-2 spherulites exist sporadically in three-dimensional forms. From these analyses on the ring bands in the interiors of bulk-form PNT crystallized at several specific temperatures, it can be proposed that the growth of spherulites in three dimensions is layer-by-layer, packing into a multi-shells structure in three-dimensional ring-banded spheres. The rarely seen Type-2 spherulites are observed to be increased in population when crystallized on KBr substrates. From the relationship of the top or bottom surface and the fractured surface of bulk PNT taken off from KBr substrate it shows that the ring-band patterns exhibited on the top or bottom surface are actually the multi-shell construction with crystalline and non-crystalline layers alternating in spherulite of the bulk.
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