The morphology of cast and annealed films from poly[bis(trifluoroethoxy)phosphazene] (PBFP, +(CF3CH20bP=N+,] has been studied by electron, scanning electron and optical microscopy. Several polymorphic forms and one mesophase (hexatic) have been established. From THF solution, PBFP has a chain folded morphology (a-orthorhombic) which transforms into a chain extended 2D hexagonal mesophase at T(1). It remains in this state until Bnal melting occurs at T, = 245 "C approximately. Upon cooling the melt, it quickly reverts to the hexagonal mesophase again, but then passes into a chain extended (3D) y-orthorhombic modification. This material is much more stable thermodynamically than the a-form, which is friable or brittle. PBFP cannot be quenched to a glassy form from the molten state, but it can be disordered as assessed by its reduced T(1) enthalpy and less well defined morpholqgy assessed by electron microscopy. Another crystal modification (B-monoclinic) has been found in solution cast low molecular weight PBFP films.

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SynopsisMorphology and crystal structure of solution-grown and melt-grown crystals of thermally decomposed polypropylene have been studied by electron microscopy and x-ray diffraction. By crystallization from dilute a-chloronaphthalene or carbitol solutions well-defined lamellar crystals about 100-150 A. in thickness are obtained from fractions (number-average molecular weights 1600-2100) of thermally decomposed crystalline polypropylene. The structure is monoclinic as crystallized from very dilute a-chloronaphthalene or carbitol solutions (0.024.005 wt.-%). However crystals of the triclinic as well as of the monoclinic forms are precipitated from carbitol solutions of higher concentrations (0.05-1 wt.-%). On the other hand, the separated triclinic form has been obtained from the melt,.I n addition, the chain molecules cannot be expected to fold, within the thickness of lamellae in crystals of either modification prepared from the low molecular weight fractions used in this study.Crystals of both modifications have similar morphology.

The ion etching technique has been applied to a morphological study of mechanically blended polypropylene (PP) with high‐density polyethylene (HDPE). Samples blended to PP/HDPE compositions of 65/35 and 85/15 by weight were highly drawn and then heat treated for 30 min at selected temperatures up to 163°C. When these samples are carefully ion‐etched several features are observed in electron micrographs, namely (i) crosshatched, and (ii) twisted or layered textured inclusions of HDPE crystals within arrays of lamellalike PP crystals situated perpendicular to the direction of drawing. X‐ray diffraction measurements of the drawn samples heat treated in the range 145–163°C for 30 min shows that oriented HDPE crystallizes with b‐axis orientation along the drawing direction. Supporting evidence is obtained from electron diffraction measurements. The molecular weight of the HDPE component is a major factor in the b‐axis‐oriented growth of HDPE crystals in PP/HDPE blends.

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