Crystalization of β-nucleated iPP in model composites with glass fibres

Janevski, Aco and Bogoeva-Gaceva, Gordana (2013) Crystalization of β-nucleated iPP in model composites with glass fibres. In: 10th Symposium ”Novel technologies and economic development”, 22-23 Oct 2013, Leskovac, Serbia.

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The aim of this work is to analyze the crystallization of β-nucleated iPP and its crystallization in model composites with different content (10-60 %) of glass fibers, known as α-nucleators, in order to predict the behaviour of real glass fiber/iPP composites, since the two polymorphic modifications of iPP are known to have different mechanical properties .
Melting and crystallization behavior of the polymer was analyzed by Perkin-Elmer DSC-7, in dynamical (heating rate 10 K/min, cooling rate 1, 3, 5, 10, 15 and 20 K/min) and isothermal regime (Tc=391-409 K) in a nitrogen atmosphere.
β-nucleator, Ca pimelate was synthesized and mixed (01 %wt.), with iPP in Brabender PL 2000 at 460K.
High content of hexagonal crystal phase of iPP in model composites was determined by the wide-angle X-ray diffraction, PLM and DSC. The kβ values estimated from x-ray diffraction patterns by Turner-Jones method was 0.94.
From isothermal DSC investigations, thermodynamical parameters of crystallization were determined. The equilibrium melting temperature (Tm0) was 446 K, and it rises with content of glass fibers up to 452 K. Crystal fold surface energy (σe) was 85.4x10-3 Jm-2 for a polymer, and 105 x10-3 Jm-2 for the composites. The Avrami plots were linear both for iPP and glass fiber composites, and the determined coefficients suggested that heterogeneous nucleation took place during the crystallization process. This was expected, because Ca-pimelate crystals represent a substrate for hexagonal crystal phase growth.
An attempt was made to evaluate results of nonisothermal crystallization with respect of nucleation activity. We applied the approach of Dobreva et al. for calculation of Θ parameter, which represents the ratio between the work of heterogeneous and homogenous nucleation, during the crystallization in polymer systems with different additives (substrates). For the neat polymer, Θ =0.34 because Ca-pimelate isa very strong nucleator, however for the composites values of 0.43-0.46 were calculated. The content of the αcrystal phase increases, with a content of the glass fibers and the temperature of crystallization for about 7%. It should be noticed that despite the -nucleation activity of glass fibers, our investigation has shown that the -phase is predominant in model composites with glass fibers in which -nucleated iPP is used as a matrix.

Item Type: Conference or Workshop Item (Poster)
Subjects: Engineering and Technology > Chemical engineering
Natural sciences > Chemical sciences
Engineering and Technology > Materials engineering
Engineering and Technology > Other engineering and technologies
Natural sciences > Other natural sciences
Divisions: Faculty of Technology
Depositing User: Aco Janevski
Date Deposited: 20 Nov 2013 14:36
Last Modified: 20 Nov 2013 14:36

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