Tailoring of Three‐Phase Crystalline Systems in Isotactic Poly(propylene)

Abstract

Summary: A novel method for the tailoring of unique three‐phase crystalline systems in isotactic poly(propylene) has been proven. It is based on a synergistic application of a specific β‐nucleating agent and high pressure during crystallization. The formation of a γ phase was supported by elevated pressure and high temperature during crystallization; under these conditions the growth of both β and α phases was significantly suppressed. Nevertheless, during the course of crystallization at lower pressure and/or lower temperatures, strong β‐nucleation efficiency favored the formation of a β phase. magnified image

The influence of chain defects on the crystallisation behaviour of isotactic polypropylene

“…This conclusion is in disagreement with an earlier published result that the two types of defects (regio/ stereo) have the same influence on the formation of the #-polymorphic form of iPP [32]. Under the crystallization conditions employed, the #-phase percentage increases up to 93±5% [33] for the polymer with the highest fraction of defects. The polymer with the lowest fraction of defects, i.e.…”

“…The polymer with the lowest fraction of defects, i.e. the polymer synthesized by a ZN, contains approximately 7±5% [33] #-phase, which is still considerable. As one can see, Figure 3 shows two approximately linear dependences on the number of regioand stereo-defects, respectively.…”

“…where X = X s + (11.1±3.1)X r (33) A combined defect fraction (X) was introduced and defined as the sum of the number of stereo-defects and the number of regio-defects multiplied by a given regio-error coefficient with a certain value t(11.1±3.1). With the current copolymer crystallization theory an expression for the regio-error coefficient can be found.…”

Crystallization behavior of isotactic polypropylene induced by competition action of β nucleating agent and high pressure

“…However, the crystallization of iPP induced by joint action of high pressure and NA are less reported [38]. During the crystallization process, the presence of NA decreases the nucleation activation energy, which leads to the crystallization of iPP occurring at relatively higher temperature (lower supercooling) on the one hand.…”

Morphology and properties of highly filled iPP/TiO2 nanocomposites

“…Addition of selective b-nucleating agents, which are generally crystallizable organic compounds with low molecular weight (e.g., quinacridone dye, triphenodithiazine, and pimelic acid), is the common method to obtain high b-phase content in iPP [20,22,23,26,27,30].…”