Kinetics of competitive crystallization of β- and α-modifications in β-nucleated iPP studied by isothermal stepwise crystallization technique

Abstract

Crystallization kinetics of β-nucleated isotactic polypropylene (β-iPP) under isothermal conditions were investigated by differential scanning calorimetry (DSC). iPP was nucleated by a trisamide derivative, namely tris-2,3-dimethyl-hexylamide of trimesic acid (TATA). In the presence of TATA possessing dual nucleating ability, the formation of the α-and β-form occurs simultaneously. An isothermal stepwise crystallization (ISC) method is suggested in this work, which can separate the crystallization process of β-and α-iPP and consequently their crystallization kinetics can be evaluated separately. The results indicated that the mechanism of crystallization changes in temperature especially in the vicinity of the upper critical temperature of the formation of the β-phase. In addition, it was found that the ratio of the growth rates of β-and α-modification determines the characteristics of crystallization and influences the apparent rate constant of crystallization of both polymorphs.

Melting and crystallization behaviors, morphology, and mechanical properties of β‐polypropylene/polypropylene‐graft‐maleic anhydride/calcium sulfate whisker composites

“…The enthalpies of the α form ( ) and β form were obtained by separating the areas of the α and β melting peaks by a “vertical line” method. The crystallinity values of the α ( X α ) and β forms ( X β ) as well as the β crystalline form content ( K DSC ) were calculated as follows: …”

Formation of various crystalline structures in a polypropylene/polycarbonate in situ microfibrillar blend during the melt second flow

“…Therefore, surface-induced polymer crystallization is paid close attention from both practical and scientific points of view. [17][18][19][20][21] b-iPP is hardly achieved under normal processing conditions because its nucleation occurs much more rarely in bulk crystallization than that of a-monoclinic. Having a transcrystalline layer at interfaces is regarded as an effective and economical method to enhance interfacial adhesion, which could greatly promote the mechanical properties of the composites.…”

The influence of glass fibers on the morphology of β-nucleated isotactic polypropylene evaluated by differential scanning calorimetry

“…iPP has been studied extensively for its polymorphic characteristics and crystallization behavior, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] since the formation of specific crystalline forms (α, β and γ, or smectic) can affect the macroscopic behavior quite dramatically. iPP has been studied extensively for its polymorphic characteristics and crystallization behavior, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] since the formation of specific crystalline forms (α, β and γ, or smectic) can affect the macroscopic behavior quite dramatically.…”