Morphology of drawn syndiotactic polypropylene films

Abstract

Morphological studies were made to investigate the drawablity of melt-quenched (MQ) and slowly cooled (MSC) films of syndiotactic polypropylene (sPP) with a high syndiotactic pentad fraction.Transmission electron microscopy (TEM) using the ruthenium tetraoxide staining and ultrathin sectioning method revealed that amorphous chains as the matrix of MQ film played a role in drawability of the film by their alignment to machine direction MD and partial crystallizations into nanofibrils. On the other hand, the initial strain induced rotations of clusters of long lamellar crystals as the major entity of MSC film, accompanying breaks of long lamellae and formation of crazes and microvoids at the cluster boundary. Compared with a homogeneous thinning of MQ film by drawing, ca. 100 nm-thick layer slips along MD and parallel to the film surface took place in MSC film. This gave rise to formation of V-shaped bent lamellar morphology and their further break into a smaller cluster of stacked lamellae which were aligned oblique by ca. 35 o from MD. With elongation, some nanofibrils formed from chains generated by the partial breaks of lamellae are aligned perpendicular 2 to the remained oblique lamellae and others parallel to MD in region where lamellar morphology almost disappeared. No chain slips in the nanofibrils can be related to a low elongation at break, i. e., a low ductility of sPP films. The lower elongation at break for MSC film than for MQ one can be interpreted by microvoids initially formed in the neck region and later moved to the fully drawn part, the microvoids initiating the break of the drawn film.

Deformation-Induced Morphology Changes and Orientation Behavior in Syndiotactic Polypropylene

“…Simultaneously, many helical chains experience a transformation into a planar conformation. Such a breakup of form I lamellae was seen by Komoto et al in TEM micrographs . The resulting helical chains are too small to form regular crystallites.…”

“…Such a breakup of form I lamellae was seen by Komoto et al in TEM micrographs. 52 The resulting helical chains are too small to form regular crystallites. Horizontal wavenumber shifts in Raman spectra illustrate the helical-to-planar conformation change very well.…”

Deconvolution Analyses of Differential Scanning Calorimetry Profiles of β-Crystallized Polypropylenes with Synchronized X-ray Measurements

“…Such duplicated DSC peaks are often observed for various polymers, − but their resolutions into each endotherm are seldom examined. In the case of ultrahigh molecular weight polyethylene, the fitting function composed by a combination of extreme and Lorenz functions was very effective for estimating the phase amounts of shish kebab morphologies …”

A study of the yield and post-yield behavior of syndiotactic polypropylene

“…Syndiotactic polypropylene (s‐PP) has been widely studied in the last fifty years mainly concerning its crystal polymorphism and morphology (see e.g., refs. 1–3) and the effects of drawing on material structure . When slowly cooled from the melt state or when crystallized from solution, s‐PP shows a crystalline phase consisting of an antichiral packing (right‐handed and left‐handed chains alternating along a and b axis of the unit cell) in which the macromolecular chains show a twofold helical conformation in an orthorhombic crystalline cell.…”