On the multiple melting behavior of bisphenol-A polycarbonate

Sohn, So Young; Alizadeh, Azar; Marand, Herve

doi:10.1016/s0032-3861(00)00110-5

Cited by 92 publications

(104 citation statements)

References 22 publications

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“…In order to overcome these disadvantages, a correction of the effect of thermal lag and a calorimetric study using various heating rates have been carried out, according to the procedure adopted by Sohn and Wu. [19,20] As well known, the increment in the observed peak temperature is proportional to the square root of the heating rate at constant thermal resistance, heat of fusion and sample weight, on the basis of the theory of heatflow calorimetry. [21] The observed melting temperatures have been therefore plotted as a function of the square root of heating rate, r 1/2 , for the different T c s (see some typical curves in Figure 8).…”

Section: Resultsmentioning

confidence: 99%

Multiple Melting Behavior of Poly(thiodiethylene terephthalate): Further Investigations by Means of X‐ray and Thermal Techniques

Fichera

Finelli

Gazzano

et al. 2004

Macro Chemistry & Physics

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Summary: The complex multiple melting behavior of poly(thiodiethylene terephthalate) (PSDET) was investigated by means of differential scanning calorimetry, X‐ray diffraction and hot‐stage optical microscopy. The phenomenon was ascribed to the existence of two different crystal structures (α and β), each of them being able to melt and recrystallize under the experimental conditions adopted. Linear and nonlinear treatments were applied in order to estimate the equilibrium melting temperature for α PSDET, by using the corrected values of Tm. The nonlinear estimation led to a higher value by about 25 °C. Isothermal crystallization kinetics of each crystalline form were analyzed according to Avrami's treatment. In both cases, values of Avrami's exponent, n, close to 3 were obtained, in agreement with a crystallization process originating from predeterminated nuclei and characterized by three dimensional spherulitic growth. The rate of crystallization of each crystalline structure was found to become lower as the crystallization temperature is increased, as usual at low undercooling, where the crystallization process is controlled by nucleation.

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Section: Resultsmentioning

confidence: 99%

Multiple Melting Behavior of Poly(thiodiethylene terephthalate): Further Investigations by Means of X‐ray and Thermal Techniques

Fichera

Finelli

Gazzano

et al. 2004

Macro Chemistry & Physics

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“…The morphology of the semicrystalline polymer is described by the stacking of crystalline polymers with multiply folded chains, localized fully amorphous domains, and intermediate motion-restricted rigid amorphous fractions [51,52]. During subsequent heating, the melting-recrystallization-remelting, the creation of secondary lamella, or the relaxation of rigid amorphous fractions are often considered for the description of the complex melting behavior of the semicrystalline polymers [53][54][55][56][57][58][59][60]. For several polymers such as PET, the issue is not finally resolved yet even though it was already studied since 1970 [61].…”

Section: Scanning Calorimetermentioning

confidence: 99%

Chip calorimetry for fast cooling and thin films: a review

et al. 2009

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Here we review on the thin-film chip calorimeter with controllable cooling as well as heating rates up to 10 6 K$s -1 developed in the last 5 years at the Institute of Physics, Rostock University. The calorimeter has been successfully used for fast thermal processing and simultaneous calorimetric measurements of many polymer samples, the physical properties of which are generally dependent strongly on their thermal history. Besides, owing to the very small addenda heat capacity, the calorimeter is very sensitive to study samples of only several tenths of nanograms. With differential alternating current (AC) design, the sensitivity of the calorimeter increased to a few tenths of pico-Joules per Kelvin. Therefore, it can be used to study glass transition of polymers confined in ultra-thin films down to several nanometers thickness. After the discussion of the strategy to realize fast cooling, we describe the static and dynamic thermal properties of the sensors used for the setup of the calorimeter. Finally, we present examples to show the performance of the calorimeter in different measurement modes.

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“…Estas interpretações, geralmente, são reunidas em grupos e descritas por meio de modelos: (i) da existência de diferentes estruturas cristalinas [12] , (ii) de fusão e recristalização [11,[13][14][15] e (iii) da dupla população de espessuras lamelares [13,16] , além do modelo de envelhecimento físico [14] , de diferentes morfologias [11] e do modelo de relaxação da fase "pseudo cristalina" [17] . Todos estes modelos estão fundamentalmente relacionados ao aparecimento, em muitos polímeros, de dois picos endotérmicos nas curvas de DSC.…”

Section: Estes Monômeros Acrílicos (unclassified

Comportamento do polipropileno em presença de monômeros trifuncionais no estado fundido e sua influência na morfologia

et al. 2004

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IntroduçãoO Polipropileno linear de configuração isotática (iPP) é um dos polímeros que pode ser objeto de cisão de cadeias durante os processos físicos e químicos utilizados na produção e para a aplicação final. A quebra das macromoléculas de um polímero, usualmente conhecido como "visbreaking" [1] resulta em produtos de baixa massa molecular. Há vários processos que promovem este efeito em poliolefinas, grupo este em que se enquadra o iPP. Dentre estes processos pode-se destacar a pirólise térmi-ca [1] , o manuseio de agentes oxidantes durante o processamento [2] , o uso da extrusão reativa [2] , os múltiplos processamentos [3] como, por exemplo, as extrusões sucessivas e a utilização da radiação ionizante [2,[4][5][6][7] , utilizados freqüentemente para modificar estruturalmente polímeros que são essencialmente lineares. O aumento da massa molecular ponderal média pode ocorrer pela reação de recombinação dos radicais ou oligômeros formados durante o processamento. A redução ou ampliação da massa molecular resulta em mudanças nas propriedades físicas e de processamento destes materiais.O iPP, como já comentado, é um polímero essencialmente linear devido ao seu processo de polimerização que pode utilizar catalisadores do tipo Ziegler-Natta e metalocênicos. Estes processos ainda não permitem a produção do iPP ramificado. No momento, a obtenção de iPP ramificado só é possível via modificação radicalar de suas Abstrac: It well known that in essentially linear polymers the properties of the melt polymers change with increasing molecular weights and degrees of branching. This behavior was observed from data analysis of the strength of the melt polymer, drawability and gel content. In this work isotactic polypropylene (iPP) in the presence of multifunctional monomers was irradiated with gamma radiation. The monomers used were Trimethylolpropane triacrylate (TMPTA) and Triallylcyanurate (TAC). iPP with TMPTA showed the highest strength in the melt and gel content, followed by TAC. It was demonstrated that TMPTA is a powerful agent to crosslinking and branching iPP. Both monomers modified the original morphology of the iPP, the melting peak shifts toward lower temperature and crystallization temperature increased during cooling after the first run. Double melting peaks were observed in the DSC thermograms, which were caused by a double lamellar thickness.

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On the multiple melting behavior of bisphenol-A polycarbonate

Cited by 92 publications

References 22 publications

Multiple Melting Behavior of Poly(thiodiethylene terephthalate): Further Investigations by Means of X‐ray and Thermal Techniques

Multiple Melting Behavior of Poly(thiodiethylene terephthalate): Further Investigations by Means of X‐ray and Thermal Techniques

Chip calorimetry for fast cooling and thin films: a review

Comportamento do polipropileno em presença de monômeros trifuncionais no estado fundido e sua influência na morfologia

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