Formation and disappearance of the rigid amorphous fraction in semicrystalline polymers revealed from frequency dependent heat capacity

Schick, Christoph; Wurm, Andreas; Mohammed, Alaa

doi:10.1016/s0040-6031(02)00526-9

Cited by 115 publications

(121 citation statements)

References 43 publications

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“…12 Calculating X C as a ratio of enthalpy values extracted from DSC curves is trouble because of the crystalline reorganization occurring at slow heating rates; 40 therefore, the values used for X C were the ones obtained by WAXD after each thermal treatment ( Table 1). The gray dotted lines reported in Figure 5 represent the repartition of crystalline and amorphous fractions expected under the assumptions of a twomodel phase for Melt isoT Cryst (X C WAXD = 66%) and Cold isoT Cryst (X C WAXD = 44%) samples.…”

Section: Articlementioning

confidence: 99%

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

et al. 2016

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In most cases, a three-phase model consisting of crystalline domains surrounded by rigid amorphous areas dispersed in the mobile amorphous phase is required and eventually sufficient to accurately describe the microstructure of semicrystalline polymers. This work shows that the microstructure developed by poly(hydroxybutyrate-co-hydroxyvalerate) by cold crystallization is better described by a complex two-phase model in which the boundaries of the crystalline domains and the surrounding amorphous environment form a “continuum of mobility”. This concept can be extended to a wide range of semicrystalline polymers. When the crystalline and the amorphous phases are strongly coupled, the rigid and mobile amorphous fractions are hardly fractionated, and the whole noncrystalline phase should be rather depicted as continuum with a broad distribution of the relaxation times associated with the glass transition. Such a depiction of the amorphous phase allows taking into account any modification of the mobility landscape with time, which can be evidenced as the progressive spreading of the relaxation functions. From a practical point of view, the rigidification of the “continuum of mobility” upon storage in conditions of cold crystallization could be considered as a cause of the progressive embrittlement sometimes observed in semicrystalline materials during physical aging and would be explained by a redistribution of the relaxation times translated in terms of relaxation temperatures

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Section: Articlementioning

confidence: 99%

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

et al. 2016

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“…About 15 years ago, the third phase, called rigid amorphous phase (RAP), an interphase between crystalline and amorphous layers, has been taken into consideration. The RAP represents a fraction of the sample that does neither contribute to the heat of fusion (crystallinity) nor to the heat capacity change ðDC p Þ or relaxation strength at the glass transition [1].…”

Section: Introductionmentioning

confidence: 99%

“…However, the author gave no information about the rigid amorphous phase in this paper. According to the literature [1,2,5,9,10] the determination of the amount of RAP X ra needs some experimental effort. One possibility is to measure the amount of the mobile amorphous phase X a (e.g.…”

Section: Introductionmentioning

confidence: 99%

Glass transition and the rigid amorphous phase in semicrystalline blends of bacterial polyhydroxybutyrate PHB with low molecular mass atactic R, S-PHB-diol

El-Taweel

Höhne²,

Mansour

et al. 2004

Polymer

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“…RAF and crystalline fraction remain solid-like at the glass transition and does not contribute to the heat capacity step at glass transition. In semi-crystalline PEEK, a rigid fraction of about 0.55 estimated at T g was reported [16], which is almost twice the crystalline fraction. Based on the three phase model assumption, the RAF of the semi-crystalline polymer can be calculated using Equation (1) where W c is the degree of crystallinity of semi-crystalline polymer and W MAF is the fraction of unstrained amorphous phase.…”

Section: Thermal Transition Analysismentioning

confidence: 93%

Self-bonding of PEEK for active medical implants applications

Awaja

Zhang

2015

Journal of Adhesion Science and Technology

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In an effort to select the best possible medical grade of polyether ether ketone (PEEK) for active medical implants application, it was necessary to inspect surface thermodynamic properties of different grades and correlate with self-bonding (autohesion) strength. Autohesion is the process of choice for encapsulating active medical implants made of PEEK. Temperature modulated DSC was used to investigate crystallinity and thermal events of range of medical grade PEEK (semicrystalline, amorphous, semi-crystalline with amorphous surface, minerals and black masterbatch filled). Lab shear test was used to measure autohesive forces between PEEK samples pressed at moderate temperature (200°C) and pressure. Samples with higher mobile amorphous region (MAF) and lower degree of crystallinity (W c ) resulted in higher autohesivce bonding strength. However, semi crystalline PEEK with surfaces that showed high MAF and low W c resulted in higher autohesive bonding strength when compared with crystalline samples. The presence of fillers (minerals and black masterbatch) in the crystalline structure doubled the autohesive bonding strength values of the semi-crystalline sample. The presence of large crystalline region and a larger portion of the rigid amorphous region acted negatively on autohesion strength. Semi-crystalline PEEK with a special manufacturing procedure to produce amorphous surface produced the best choice among the PEEK grades. This grade have the desired thermodynamical properties in the bulk while exhibiting best surface adhesion strength.

show abstract

Formation and disappearance of the rigid amorphous fraction in semicrystalline polymers revealed from frequency dependent heat capacity

Cited by 115 publications

References 43 publications

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

Glass transition and the rigid amorphous phase in semicrystalline blends of bacterial polyhydroxybutyrate PHB with low molecular mass atactic R, S-PHB-diol

Self-bonding of PEEK for active medical implants applications

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