Advanced nucleating agents for polypropylene

Abstract

The present short review aims to summarize advanced nucleating agents for polypropylene (PP). Reviewing the relevant literature, we focused on powerful nucleators that are capable of significantly increasing the crystallization temperature of the polymer at very low working concentrations and also serving as clarifying agents. The nucleation mechanism and efficiency of these compounds are discussed in detail. The nucleating agents were divided into groups according to their tendency to induce monoclinic (α), hexagonal (β), or orthorhombic (γ) PP cell geometries. The major α‐nucleators and clarifiers are sorbitol‐based compounds that speed‐up the polymer crystallization due to gelation phenomena and induction of epitaxial crystallization by the metal salts of substituted aromatic heterocyclic phosphate. Among β‐nucleators, N,N′‐dicyclohexyl‐2,6‐naphthalene dicarboxamide was found to be very efficient and its nucleation ability was highly concentration dependent. In addition, it was shown that nucleation efficiency of a nucleator can be significantly increased by a new dispersion method comprising its solubilization in a microemulsion. Moreover, the nucleator (HPN‐68) increased the γ‐modification present in the polymer. Copyright © 2007 John Wiley & Sons, Ltd.

Synthesis and Structure–Efficiency Relations of 1,3,5‐Benzenetrisamides as Nucleating Agents and Clarifiers for Isotactic Poly(propylene)

“…[6][7][8] The induction of the a-phase in i-PP, as well as reduction of spherulite size improve mechanical properties such as strength and stiffness, [1,9] whereas b-phase nucleated i-PP products feature increased toughness. A general review summarizing the state of the art in the nucleation of i-PP was recently published by Libster et al [10] Most important for the increasing market of poly(propylene) is the introduction of so-called ''clarifying agents,'' addition of which yield highly transparent, semi-crystalline i-PP, which is normally opaque and, hence, excluded from applications such as transparent packaging. These clarifying agents are self-assembling species and mostly based on sorbitol acetal chemistry.…”

Metallocene polypropylene crystallization kinetic during cooling in rotational molding thermal condition

“…Figure 12 presents numerical T-t diagram obtained with three coefficients (20,25, and 30 W m À2 C À1 ) and for a furnace maintained at 300 C. Thanks to experimental results, we note that a value of 25 W m À2 C À1 presents a real sense in our case. Olson et al 48 find a similar result.…”

“…Some thermograms obtained with Rotolog system 57 are presented in Figure 3. The various heating times are indicated on curves (20,25, and 30 min at 300 C). By approximating heating and cooling stages by a straight line, it was possible to determine graphically heating and cooling rates.…”

“…Scanning Electron Microscopy (SEM) As explained in the introduction part, the increasing of crystallization kinetic during cooling stage does not allow any microstructure observation. 20,21 To observe the microstructure of a metallocene PP grade, we have decided to decrease drastically cooling rate. For that, we have used the oven of a DSC 7 from Perkin Elmer.…”

“…[10][11][12][13][14][15][16][17][18][19] But, the increasing of crystallization kinetic during cooling stage does not allow any microstructure observation. 20,21 Metallocene materials were then stimulated great interest. 22 To simulate the crystallization kinetics of metallocene polymers, global kinetics have often been used.…”