Lamellar branching

Fig. 21 In-situ phase images of a BA-C10 film showing the lamellar branching at different temperatures a and b no branching at 80 °C c and d branching largely at the tips of lamellae when the temperature is quenched to 35 °C [64]. The time interval between a and b was about 106 min...

Lotz, B. and Wittmann, J.C. (1986) The molecular origin of lamellar branching in the a (monoclinic) form of isotactic polypropylene. /. Polymer Sci., Part B, Polymer Phys., 24, 1541-58. 

From a thorough analysis the corresponding distribution of lamellar thicknesses can be directly accessed. In addition, the mechanism of lamellar branching via the action of screw dislocations (166,167), which eventually leads to a spherical envelope of spherulites (see section Multilamellar Crystals, Hedrites, and Spherulites), could be confirmed. 

Scheme 11.2 Lamellar branching and epitaxial relationships in isotactic polypropylene (Reprinted from Auriemma and De Rosa 2006 with permission)...

Padden FJ, Keith HD (1973) Mechanism for lamellar branching in isotactic polypropylene. J Appl Phys 44 1217... 

Isotactic polypropylene displays a highly unusual ability to induce epitaxial crystallization of a number of different polymers with their chain axes tilted at large angles, 40—80°, relative to the helix axis direction of the polypropylene substrate. The same polymer shows an epitaxy, i.e. homoepitaxy, at an angle of 80° (Fig. 7.30). The homoepitaxy is responsible for crosshatching, a structure typical of the monoclinic a structure. This feature causes the lamellar branching and the optical complexity, with both positive and negative spherulites, typical of isotactic polypropylene (section 7.4). 

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