On the interpretation of multiple melting peaks in poly(ether ether ketone)

Blundell, D.J.

doi:10.1016/0032-3861(87)90382-x

Cited by 258 publications

(176 citation statements)

References 7 publications

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“…Complex melting peaks were observed for both materials with the main ones occurring in the range 142-179 °C and 137-176 °C for PHB-1 and PHB-2, respectively. Multiple melting peaks are commonly observed in many semicrystalline polymers, including polyesters such as poly(ethylene terephtalate) (PET) 22 and poly(trimethylene terephalate) (PMT) 23 , polyethers such as poly(ether ether ketone) (PEEK) 24 , and polyolefins such as polypropylene (PP) 25 . Multiple melting peaks may be attributed to the melting of crystals of different sizes and perfection.…”

Section: Differential Scanning Calorimetry (Dsc) Measurementsmentioning

confidence: 99%

Environmental Stress Cracking of Poly(3-hydroxibutyrate) Under Contact with Sodium Hydroxide

et al. 2015

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Environmental stress cracking (ESC) is one of the most important causes of polymer premature failure, occurring when a combination of mechanical load and an aggressive fluid is applied. The phenomenon is well know by polymer producers and product designers but its mechanisms are not very well understood. Although the ESC effects of many commercial polymers are well known, this type of failure in biopolymers were not studied yet. In the current work, the stress cracking behaviour of poly(3-hydroxybutyrate) (PHB) with 4,0 and 6,2% of hydroxyvalerate (HV) was investigated in injection-moulded bars under contact with sodium hydroxide (NaOH) solutions. The experiments were conducted using two different types of stress arrangements: (i) an ordinary tensile testing and (ii) a relaxation experiment. In both situations the injection-moulded bars were exposed to the NaOH solution and some testing conditions where varied, like the cross-head speed of the tensile test and the maximum load of the relaxation arrangement. The results showed that NaOH acted as a strong stress cracking agent for PHB, causing surface cracking and reducing significantly the mechanical properties. Catastrophic failure with an extensive surface damage was also observed by photographed and scanning electron microscopy (SEM) images. The magnitude of the effects increased with decreasing crosshead speed and increasing loading level.

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Section: Differential Scanning Calorimetry (Dsc) Measurementsmentioning

confidence: 99%

Environmental Stress Cracking of Poly(3-hydroxibutyrate) Under Contact with Sodium Hydroxide

et al. 2015

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“…Complex cold crystallization peaks were observed for PET/PS blends with less that 10% PS. According to literature, the shape of crystallization peaks is related to morphology of crystalline phase [23][24][25][26][27][28] . Both peaks, exothermic crystallization peak and endothermic fusion peak, were integrated from starting to end points visually determined, using a straight virtual baseline between them, to obtain the mass fractions crystallized or fused, respectively:…”

Section: Resultsmentioning

confidence: 99%

Effect of polystyrene on poly(ethylene terephthalate) crystallization

Wellen

2014

Mat. Res.

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Blends of poly(ethylene terephthalate) (PET) and polystyrene (PS) with PS content ranging from 0% to 60% by weight, were compounded in a laboratory internal mixer, followed by quenching into iced water, resulting in substantially amorphous compounds. Blend morphology was analyzed by scanning electron microscopy (SEM). Standard differential scanning calorimetry (DSC) was used to study the cold crystallization and melting behavior of PET and PET/PS blends. SEM micrographs show a two-phase structure made up with spherical PS particles dispersed in a PET matrix. DSC scans showed that crystallization of PET is affected by the heating rate and by the addition of even small amounts of PS. In particular, the rate of cold crystallization of PET is significantly reduced by the incorporation of 1% of PS, attributed to the anti-nucleating effect of PS on PET. The amount of PET crystallized and the melting characteristics (temperature, rate) are not significantly affected by either PS content or heating rate.

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“…The multiple melting behavior is usually explained by polydisperse lamellar thickness (dual lamellar thickness) (Cheng et al, 1986;Hsiao et al, 1993a, b), melting-recrystallization-remelting (Blundell & Osborn, 1983;Blundell, 1987) and polymorphic crystals (Sun & Woo, 1999;Ho et al, 2000;Gan et al, 2004;Ghosh et al, 2005). Both the dual lamellar thickness and melting-recrystallization-remelting can easily be confirmed by DSC measurements at different scan rates and different annealing treatments (time and/or temperature).…”

Section: Introductionmentioning

confidence: 98%

Melting behavior of polymorphic crystals of poly(trimethylene 2,6-naphthalate) studied by simultaneous synchrotron X-ray scattering and thermal analysis

et al. 2007

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The polymorphic crystallization and melting behavior of poly(trimethylene 2,6‐naphthalate) (PTN) have been investigated using small‐angle X‐ray scattering and simultaneous wide‐angle X‐ray scattering (WAXS) and differential scanning calorimetry (DSC). The α‐crystal, the β‐crystal and the coexistence of both crystal forms of PTN develop at an isothermal temperature below 393 K, above 453 K and between these two temperatures, respectively. The simultaneous WAXS/DSC measurement provides a good way to identify the origin of multiple melting peaks and to get equilibrium melting temperatures. During the PTN melting process, the thermal evolutions of crystallinities, Bragg diffraction intensities and DSC thermograms reveal that the phase transformation and primary and secondary crystallizations arise to generate the multiple melting peaks. The β‐crystal with high equilibrium melting temperature ( = 510 K) is a structurally stable phase while the α‐crystal with low equilibrium melting temperature ( = 488 K) is a metastable phase. The temperature‐dependent structural parameters such as the long period, lamellar thickness and amorphous thickness were extracted from the interface distribution function. Two‐step changes in the lamellar thickness and the invariant during the subsequent melting of PTN crystallized at 383 K are consistent with the transformation obtained by WAXS/DSC. The transformation, a typical melting–recrystallization, proceeds firstly via surface melting of α‐lamellae, and then the PTN chains near the boundaries of surviving α‐lamellae modify their conformation to form the β‐crystal resulting in thickening lamellae.

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On the interpretation of multiple melting peaks in poly(ether ether ketone)

Cited by 258 publications

References 7 publications

Environmental Stress Cracking of Poly(3-hydroxibutyrate) Under Contact with Sodium Hydroxide

Environmental Stress Cracking of Poly(3-hydroxibutyrate) Under Contact with Sodium Hydroxide

Effect of polystyrene on poly(ethylene terephthalate) crystallization

Melting behavior of polymorphic crystals of poly(trimethylene 2,6-naphthalate) studied by simultaneous synchrotron X-ray scattering and thermal analysis

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