Crystallization of long-chain branched polypropylene with nucleating agents

Result code in IS VaVaI

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Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Crystallization of long-chain branched polypropylene with nucleating agents

Original language description

Isotactic polypropylene (PP) is a versatile material which can crystallize into several crystal modifications according to molecular structure and crystallization conditions. Common linear polypropylene (L-PP) usually crystallizes into monoclinic α-phase. To increase rate of crystallization, heterogeneous nucleating agents are often added which affect also morphology decreasing size of spherulites. Special α-nucleating agents serve as clarifying agent improving transparency of the material. Specific nucleators can induce crystallization into trigonal β-phase showing significantly higher impact strength. The introduction of long branches onto polypropylene chain significantly changes the crystallization behaviour. As long-chain branched polypropylene (LCB-PP) processes self-seeding effect, the overall crystallization is faster with higher crystallization temperature [1, 2]. In this work, isothermal crystallization of LCB-PP without/with two types of nucleating agents is studied and compared with that of linear PP. Crystallization half-time of linear and branched PP with/without commercial α-nucleating/clarifying agent Millad 3988 (1,3;2,4-bis(3,4-dimethylbenzylidene)sorbitol)) (α-PP and α-LCB-PP) or β-nucleating agent NJ Star NU 100 (N,N´-dicyclohexylnapthalene-2,6-dicarboxamide) (β-PP and β-LCB-PP) crystallized at several temperatures (135, 140, 142, 144, 146, 148 and 150 °C) is shown in Figure 1. While L-PP crystallized in a given time of 180 min only at low temperatures of 130 and 135 °C, branched polypropylene and all nucleated ones could not be evaluated at these temperatures: they crystallized already when cooled to the crystallization temperature and the exotherm was not complete. LCB-PP samples showed the lowest crystallization half-life independent on the presence of nucleating agent. Figure 2 shows melting temperatures of isothermally crystallized samples. Several melting temperatures (peak of melting endotherm) in L-PP indicate the polymorphic composition, especially in the β-nucleated PP. On the other hand, all LCB-PP samples show only one melting temperature corresponding to α-phase.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

10404 - Polymer science

Project

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Continuities

V - Vyzkumna aktivita podporovana z jinych verejnych zdroju

Publication year

2023

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů