On crystallization phenomena in PEEK☆

Bassett, D. C.; Olley, R. H.; Raheil, I.A.M. Al

doi:10.1016/0032-3861(88)90386-2

Cited by 362 publications

(230 citation statements)

References 18 publications

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“…These results emphasise how complex the thermal behaviour of PEEK is and can also be the reason for the observed correlation between the minimum value of the 1 st derivative and the bed temperature. Fundamental studies carried out on the crystal structure of PEEK showed the possibility of having two populations of lamellar thickness [36][37][38]. Recently, Wang et al [39] identified also two types of nano-sized crystal blocks self-organized into a spherulitic structure in PEEK.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Predicting processing parameters in high temperature laser sintering (HT-LS) from powder properties

2016

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New materials for Laser Sintering (LS) are usually developed using a trial and-error approach that consists of a series of builds within LS systems. This strategy is time consuming, costly and focuses only on the optimisation of the processing parameters, ignoring the powder properties of the materials under examination. Being able to predict processing parameters on the basis of the powder material properties would enable a faster development of new materials and new applications, while acknowledging a more in-depth understanding of the mechanisms involved in LS. This paper provides new results into the prediction of processing conditions from the material properties. It is here shown that high temperature polymers such as Poly Ether Ether Ketone (PEEK) and Poly Aryl Ether Ketone (PEK) can be successfully used in LS despite the lack of a super-cooling window. The evaluation of the stable sintering region of PEEK 450PF and the application the energy melt ratio parameter in relation to the mechanical performance of laser sintered PEEK samples are also provided. Lastly, a new method for estimating the powder bed temperature is proposed.

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Section: Accepted M Manuscriptmentioning

confidence: 99%

Predicting processing parameters in high temperature laser sintering (HT-LS) from powder properties

2016

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“…In order to do so, the nature of the secondary crystallites must first be established. This discussion is based on the two variances 27,31,40,41,[43][44][45]47,48 of the dual-lamellar population model 35,38 and a recent notion on secondary crystallization in polymers proposed by Marand and Alizadeh. 74 It is well established that overall crystallization in semicrystalline polymers can be divided into two main processes: primary crystallization and secondary crystallization.…”

Section: Dependence Of Subsequent Melting Endotherms On Crystallizatimentioning

confidence: 99%

“…The dual-lamellar population model, which was originally suggested by Cebe and Hong 35 and Bassett et al, 38 hypothesizes that a bimodal distribution of lamellae of different thicknesses exists within crystalline aggregates formed at the crystallization conditions studied, and the melting of the thin and the thick lamellae give rise to the appearance of the low-and high-temperature endotherms, respectively. The two extensions of this model 49 are the dual-lamellar stack model 27,31,40,47,48 and the lamellar insertion model.…”

Section: Introductionmentioning

confidence: 96%

“…34 -50 A number of hypotheses were proposed to explain the occurrence of multiple melting endotherms. In the studies of isothermal crystallization under quiescent conditions (i.e., crystallization is only a function of temperature), the multiple melting behavior of these semicrystalline polymers may be designated as being the result of one of the following reasons: the presence of two (or more) crystal modifications, 13,15 the presence of two (or more) crystalline morphologies, 28 the presence of two populations of crystal lamellae of different thicknesses, 35,38,40,[43][44][45] and the simultaneous melting, recrystallization, and remelting of the lamellae initially formed at the crystallization conditions. 22,34,37,39,42,46 Among these models, simultaneous meltingrecrystallization-remelting and the dual-lamellar population models seem to receive much attention in explaining the multiple melting behavior in various semicrystalline polymers that do not exhibit multiple crystal modifications upon crystallizing at the crystallization conditions studied.…”

Section: Introductionmentioning

confidence: 99%

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Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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ABSTRACT:The melting behavior of syndiotactic polypropylene (s-PP) after isothermal crystallization from the melt state was studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques. Three melting endotherms were observed for isothermal crystallization at high degrees of undercooling. The minor endotherm, located closed to the corresponding crystallization temperature, was postulated to be the melting of the secondary crystallites formed at the crystallization temperature. The low-temperature melting peak was found to be the melting of the primary crystallites formed, and the high-temperature melting peak was a result of the melting of the crystallites recrystallized during a heating scan. The triple-melting behavior observed in subsequent melting endotherms of s-PP was therefore described as contributions from melting of the secondary crystallites and their recrystallization, partial melting of the less stable fraction of the primary crystallites and their recrystallization, melting of the primary crystallites, and remelting of the recrystallized crystallites formed during the heating scan. In addition, determination of the equilibrium melting temperature for this s-PP resin according to the linear and nonlinear Hoffman-Weeks extrapolations provided values of 143.1 and 185.6°C, respectively.

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“…and biodegradable polymers (e.g. PHB, PLLA), which have usually been interpreted in terms of a pre-exiting morphology 36,37 and/or reorganization. [38][39][40][41][42][43] Both reasons often compete with one another to make the melting behaviour very complex, and sometimes it is very difficult to differentiate between these two phenomena.…”

Section: Effective Energy Barriermentioning

confidence: 99%

Development of novel melt-processable biopolymer nanocomposites based on poly(l-lactic acid) and WS2 inorganic nanotubes

2014

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The use of tungsten disulphide inorganic nanotubes (INT-WS 2 ) offers the opportunity to produce novel and advanced biopolymer-based nanocomposite materials with excellent nanoparticle dispersion without the need for modifiers or surfactants via conventional melt blending. The study of the non-isothermal melt-crystallization kinetics provides a clear picture of the transformation of poly(L-lactic acid) (PLLA) molecules from the non-ordered to the ordered state. The overall crystallization rate, final crystallinity and subsequent melting behaviour of PLLA were controlled by both the incorporation of INT-WS 2 and the variation of the cooling rate. In particular, it was shown that INT-WS 2 exhibits much more prominent nucleation activity on the crystallization of PLLA than other specific nucleating agents or nano-sized fillers. These features may be advantageous for the enhancement of mechanical properties and processability of PLLA-based materials. PLLA/INT-WS 2 nanocomposites can be employed as low cost biodegradable materials for many eco-friendly and medical applications, and the exceptional crystallization behaviour observed opens new perspectives for scale-up and broader applications.

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On crystallization phenomena in PEEK☆

Cited by 362 publications

References 18 publications

Predicting processing parameters in high temperature laser sintering (HT-LS) from powder properties

Predicting processing parameters in high temperature laser sintering (HT-LS) from powder properties

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Development of novel melt-processable biopolymer nanocomposites based on poly(l-lactic acid) and WS2 inorganic nanotubes

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