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Journal ArticleDOI

Polymer Crystallization By Chemical Nucleation

04 Aug 1983-Nature (Nature Publishing Group)-Vol. 304, Iss: 5925, pp 432-434
TL;DR: In this article, the mechanism of action of organic nucleating agents such as sodium benzoate and its derived salts completely differs from the generally accepted model, at least in the case of polyesters.
Abstract: Several attempts1–5 have been made to control the rate of crystallization and the morphology by the addition of very finely-divided substances which promote abundant nucleation. However, these studies have mostly been carried out on an empirical basis and, except in a few cases (self-seeding6, epitaxy2–5), the mechanism of action of these nucleating agents is poorly understood despite several attempts at modelling1,2. This is particularly so in the case of most technical nucleating agents such as mica, talc and organic salts. We report here that the mechanism of action of organic nucleating agents such as sodium benzoate and its derived salts completely differs from the generally accepted model, at least in the case of polyesters. The nucleating agent reacts as a true chemical reagent with the molten macromolecules and produces ionic end groups which constitute the true nucleating species.
Citations
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TL;DR: An overview of the current understanding on the fundamentals of PLA crystallization in quiescent conditions and on the practical means to enhance its rate can be found in this paper, where the most promising efforts in enhancing PLA crystallisation kinetics through plasticization or heterogeneous nucleation are reviewed.

1,144 citations

Journal ArticleDOI
02 Nov 2007-Polymer
TL;DR: In this article, different strategies to promote PLA crystallization were investigated with the objective of increasing the crystalline content under typical polymer processing conditions, and the effect of heterogeneous nucleation was assessed by adding talc, sodium stearate and calcium lactate as potential nucleating agents.

676 citations

Journal ArticleDOI
TL;DR: In this paper, the authors propose an epitaxie polymere-polymere-substrat organique (polymer-polymer) for the preparation of polyethylene substrats.

407 citations

Journal ArticleDOI
TL;DR: It was proposed that the nucleation mechanism of the PLLA/PPZn system is epitaxial nucleation, and PPZn shows excellent nucleating effects on P LLA crystallization.
Abstract: Layered metal phosphonate, zinc phenylphosphonate (PPZn), reinforced poly(l-lactide) (PLLA) composites were fabricated by a melt-mixing technique. The nonisothermal and isothermal crystallization, melting behavior, spherulite morphology, crystalline structure, and static and dynamic mechanical properties of the PLLA/PPZn composites were investigated. PPZn shows excellent nucleating effects on PLLA crystallization. With incorporation of 0.02% PPZn, PLLA can finish crystallization under cooling at 10 °C/min. The crystallization rate of PLLA further increases with increasing PPZn concentration. Upon the addition of 15% PPZn, the crystallization half-times of a PLLA/PPZn composite decrease from 28.0 to 0.33 min at 130 °C, and from 60.2 to 1.4 min at 140 °C, compared to the neat PLLA. With the presence of PPZn, the nuclei number of PLLA increases and the spherulite size reduces significantly. Through analysis of the crystal structures of PLLA and PPZn, it was proposed that the nucleation mechanism of the PLLA/...

184 citations

Journal ArticleDOI
TL;DR: A detailed overview on research in the area of IF-based polymer nanocomposites, with special emphasis on the use of inorganic fullerene-like (IF-WS2) nanoparticles as environmentally friendly reinforcing fillers is presented in this article.

151 citations

References
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Journal ArticleDOI
01 Apr 1969
TL;DR: In this paper, a technique d'autoensemencement for obtenir des preparations homogenes de monocristaux en solution a ete appliquee a la cristallisation des polymeres fondus, stabilises par recuit.
Abstract: La technique d’autoensemencement pour obtenir des preparations homogenes de monocristaux en solution a ete appliquee a la cristallisation des polymeres fondus. On montre, en effet, que la croissance des spherulites peut Etre initiee quasi simultanement par des fragments cristallins submicroscopiques, stabilises par recuit. La concentration et la taille moyenne de ces fragments dependent de l’histoire thermique de l’echantillon, plus particulierement de la temperature maxima T s ou il a ete fondu avant la recristallisation. Toutefois, une partie des germes, lies aux impuretes de l’echantillon, paraIt indestructible, car leur nombre est independent de la temperature T s . Ainsi la concentration de l’ensemble des germes que l’on estime a partir de la cinetique de cristallisation (determinee par dilatometrie) et de la vitesse de croissance radiale des spherulites (mesuree sous microscope), varie d’une maniere discontinue avec T s . La temperature critique Tf * est voisine, mais plus petite, que la temperature de fusion d’equilibre, Tf 0; la difference etant une fonction de la taille des germes produits par l’autoensemencement. Ces divers effects sont analyses et discutes en s’appuyant sur un grand nombre de resultats experimentaux, obtenus avec des echantillons de polybutene-I (isotactique), de polyethylene et de polyoxyethylene, de masses moleculaires elevees. On examine, en outre, quelques effects particuliers provoques par la variation de la concentration des germes sur la cinetique de cristallisation isotherme de ces echantillons. Ces effets ont ete interpretes par la modification de la texture spherulitique.

102 citations