Structural characterization of α‐ and β‐nucleated isotactic polypropylene

Abstract

Modification of isotactic polypropylene (iPP) with two nucleation agents, namely 1,3:24‐bis(3,4‐dimethylobenzylideno) sorbitol (DMDBS) (α‐nucleator) and N, N′‐dicyclohexylo‐2,6‐naphthaleno dicarboxy amide (NJ) (β‐nucleator), leads to significant changes of the structure, morphology and properties. Both nucleating agents cause an increase in the crystallization temperature. The efficiency determined in a self‐nucleation test is 73.4 % for DMDBS and 55.9 % for NJ. The modification with NJ induces the creation of the hexagonal β‐form of iPP. The addition of DMDBS lowers the haze of iPP while the presence of NJ increases the haze. Copyright © 2004 Society of Chemical Industry

Advances in Polypropylene Based Materials

“…In most cases, the β-form can only be partially formed in samples mixed with α-form. A high content of the β-form in iPP can be achieved under special conditions such as rapid quenching, zone solidification, crystallization under a temperature gradient [12,15] or in the presence of selective β nucleating agents [21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Conformation of macromolecules in γ-form is analogous to α form, and it can be obtained as a result of crystallization under elevated pressure above 200 MPa and from iPP samples with a low molecular weight.…”

“…Derivatives of sorbitol are the most effective known nucleating agents of iPP, leading exclusively to the creation of the monoclinic α-form [26,38,39]. The best-known β-nucleating agents are the trans-quinacridone [21] and a bicomponent mixture of pimelic acid and calcium stearat [40]. A particularly important structural effect, usually observed if nucleating agents are introduced into semi-crystalline polymers, is an increase of crystallization temperature T c .…”

Crystallization of Polypropylene: Application of Differential Scanning Calorimetry Part Ii. Crystal Forms and Nucleation

“…There is particular interest in adjustment of the optical properties, a so-called clarifying effect achieved by the use of the derivatives of sorbitol [59][60]. One can also affect mechanical properties, namely enhance the impact strength and lower the stiffness for β-nucleated iPP [56].…”

“…The best-known β-nucleating agents are the trans-quinacridone Permanent Red [56] and a bicomponent mixture consisting of equivalent amounts of pimelic acid and calcium stearat [57]. The amount of the β-phase in iPP depends on the concentration of the additives and on the cooling conditions during crystallization from the melt.…”

Controlled Crystallization of Isotactic Polypropylene Based on α/β Compounded Nucleating Agents: From Theory to Practice

“…NA as one of the additives presents a role of increasing the nucleation density of polymer greatly and enhancing the nucleation rate dramatically so as to have a great impact on the mechanical properties of polymer (Kristiansen et al, 2003;Romankiewicz et al, 2004;Tenma & Yamaguchi, 2007). So far, two kinds of NAs, phase and phase NAs discriminated by the form of iPP they induce have been widely put into use in modifying iPP.…”