Polymorphism of Isotactic Poly(1-butene) as Revealed by Microindentation Hardness. 1. Kinetics of the Transformation

Abstract

The microindentation hardness technique has been employed to examine the II → I polymorphic transformation of i-PBu1 taking place upon aging at room temperature. The hardness values of form I are shown to be remarkably higher than those of form II due to the denser packing of chains in the hexagonal crystal modification. The kinetics of the II → I transformation has been followed by means of microindentation hardness measurements in real time. The influence of molar mass and crystallization temperature on the kinetics of the polymorphic transformation is examined. Results suggest that the rate of polymorphic transformation is independent of molecular weight. In addition, it is seen that increasing the crystallization temperature (up to 105 °C) notably reduces the time required for a full transformation of form II into form I. The influence of the fraction of amorphous material on the rate of polymorphic transformation is discussed.

Direct melt crystal growth of isotactic polybutene‐1 trigonal phase

“…Isotactic polybutene-1 (it-PB1) is a semicrystalline polyolefin which exhibits outstanding mechanical properties and pronounced polymorphs that depend on its crystallization conditions [1,2]. Three different polymorphs, designated trigonal (forms I and I') and tetragonal (form II) and orthorhombic phases, have been reported in the literature [3][4][5][6][7].…”

Effect of polymorphism of isotactic polybutene‐1 on peel behavior of polyethylene/polybutene‐1 peel systems

“…The form II-form I crystal-crystal transformation of the specific iPB-1 is faster than expected. Former, independent research about the transition kinetics suggests completion of the phase transformation after 100 to 200 h. 3,4,18 The phase transformation of the particular iPB-1 of the present study, obviously, is completed already after about 50 h. The faster Figure 1 TEM images of LDPE/iPB-1 blends with 6 m% iPB-1 (left column, images a6 and b6), and 15 m% iPB-1 (right column, images a15 and b15). The top images (a6 and a15) show the phase structure of the MD-ND cross-section and the bottom images (b6 and b15) show the phase structure of the TD-ND cross-section.…”

“…1,2 The degree of crystallinity is typically about 50-70%. 3,4 iPB-1 is polymorphic, i.e., the crystalline phase can adopt different structures. Crystal polymorphs include forms I, II, and III and forms I 0 and II 0 .…”

“…16 The kinetics of the phase transformation depends on one side on the chemical structure of the macromolecule, i.e., on the molecular weight, tacticity, or presence of comonomers, and on the physical superstructure which is controlled by the condition of processing/primary solidification. 3,4,23 As for the effect of condition of primary crystallization, it was found that the transformation rate is increased with decreasing temperature of primary formation of form II crystals. 24 Since a decrease of the crystallization temperature yields smaller crystals, it can be assumed that the phase-transformation rate increases due to an increase of possible sites of nucleation.…”

Preparation and Properties of PB-1/PP Blends

“…Given its outstanding properties in heat creep and stress cracking resistance, flexibility, superb chemical stability, abrasion resistance and plasticity [1] , it is honored as the ''Golden Plastic'' [2] in the world. As the price of PB-1 is relatively higher, while polypropylene (PP) is a kind of common polymer with a lower cost, and the molecular structures of PB-1 and PP are comparatively similar, so these are reasonable to produce PB-1=PP blends in real produce [3,4] .…”