On the crystallization mechanism of poly(ethylene terepthalate) in its blends with poly(vinylidene fluoride)

Rahman, M. Habibur; Nandi, Arun K.

doi:10.1016/s0032-3861(02)00660-2

Cited by 24 publications

(27 citation statements)

References 34 publications

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“…A remarkable feature of the dependence is a break point at ~ 475 K (i.e., ~ 202 °C) that signals a change in the crystallization mechanism. For isothermal PET crystallization, Lu and Hay [110] and Rahman and Nandi [111] have reported a change in the crystallization mechanism revealed as a break point in the Hoffman-Lauritzen plot (Eq. 3.54) at the respective temperatures 217 and 236 °C.…”

Section: E U T T T K R T T T T T T Tmentioning

confidence: 99%

Physical Processes

Vyazovkin

2015

Isoconversional Kinetics of Thermally Stimulated Processes

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Section: E U T T T K R T T T T T T Tmentioning

confidence: 99%

Physical Processes

Vyazovkin

2015

Isoconversional Kinetics of Thermally Stimulated Processes

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“…The nucleation parameter K g is given by Equation (8). (8) where b is the monomolecular layer thickness, taken to be the perpendicular separation of (010) planes, this is 5.53 Å [2]. σ is the side surface free energy of the polymer crystal, σ e is the fold surface free energy, ΔH f is the enthalpy of fusion per unit volume (2.1·10 8 J/m 3 ) [2] and k B is the Boltzmann constant equaling to 1.35·10 -23 J/mol·K.…”

Section: The Fold Surface Free Energy Based On Hoffman-lauritzen Relamentioning

confidence: 99%

“…The side surface free energy σ is often estimated as [25] (9): (9) where α was derived empirically to be 0.11 by analogy with the known behavior of hydrocarbons . The unit cell dimensions, a 0 and b 0 for PET used in the analysis are 4.57 and 5.95 Å, respectively [2]. Combining Equation (8) and Equation (9), we can observe the Equation (10) as follows: (10) σ e of pure PET and PET/nucleating agent blends are determined, and listed in Table 3.Generally speaking, the smaller the fold surface free energy σ e , the faster the crystallization rate of polymer crystal.…”

Section: The Fold Surface Free Energy Based On Hoffman-lauritzen Relamentioning

confidence: 99%

“…However, it has not gained noticeable application in the field of injection molding because of its low crystallization rate. In order to accelerate the crystallization rate of PET and obtain the desired morphology and properties, a great deal of effort has been made into studying the crystallization kinetics corresponding to the change of the performed properties [1][2][3][4][5][6][7][8][9]. It is generally considered that the addition of nucleating agents gives rise to increase the crystallization rate of PET [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Effect of nucleating agents on crystallization kinetics of PET

Jiang¹,

Luo²,

Sun³

et al. 2007

Express Polym. Lett.

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Abstract. Effects of three nucleating agents concluding talc, sodium benzoate (SB) and an ionomer (Ion., Na + ) on crystallization of poly(ethylene terephthalate) (PET) were studied by differential scanning calorimetry (DSC) and polarized optical microscope (POM), the parameters of crystallization kinetics were obtained through Avrami and Ozawa equations. The fold surface free energy σe of pure PET and PET/nucleating agent blends was calculated by Hoffman-Lauritzen theory. The results indicate that the three kinds of nucleating agents increase the crystallization rate constant through promoting their nucleating effect for PET crystallization, among which SB is the best one with the same content. The crystallization mode of PET might shift from three-dimensional growth to two-dimensional growth by the addition of the nucleating agents. The values of σe of PET/nucleating agent blends are much less than that of pure PET, and PET/SB (99:1) blend has the least value of σe (18.2 mJ/m 2 ). The conclusion based on Hoffman theory is similar to the analysis by Avrami and Ozawa equations.

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“…Esse resultado é altamente significativo em termos práticos, uma vez que a adição de apenas 1% de poliestireno, que provoca praticamente os mesmos efeitos da adição de 15% de PS, deve provocar efeitos mínimos nas propriedades mecânicas, propriedades óticas e processabilidade do PET. A diminuição da taxa de cristalização do PET foi previamente observada em diferentes sistemas poliméricos como é o caso das blendas PET/PC [8] , PET/PEI [30] e PET/PVF 2 [31] , como resultado dos processos de segregação de moléculas do segundo componente, de uma limitada solubilidade entre os componentes da blenda, de um aumento da energia de ativação para a cristalização isotérmica e de uma diminuição da cristalizabilidade do PET. Porém, nestas blendas a concentração do segundo componente variou entre 10-50%.…”

Section: Cinética De Cristalização Isotérmica a Friounclassified

Redução da velocidade de cristalização a frio do PET na presença de poliestireno

Wellen¹,

Rabello²

2007

Polímeros

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Resumo: A cristalização a frio do poli(tereftalato de etileno) (PET) e de suas blendas com poliestireno (PS) foi estudada utilizando calorimetria exploratória diferencial (DSC), análise dinâmico-mecânica (DMA), microscopia eletrônica de varredura (MEV) e propriedades mecânicas. As blendas PET/PS formam misturas bifásicas, como confirmado por MEV e por DMA, onde fases distintas e duas T g s foram observadas. Por outro lado, a determinação da temperatura de fusão de equilí-brio (T m o ) do PET por DSC indicou uma diminuição neste parâmetro com a presença do PS, sugerindo que uma solubilidade limitada do PS no PET deve ocorrer. A presença de um componente não cristalizável como o PS, parcialmente solúvel em uma fase cristalizável como PET, reduz a habilidade de cristalização. Isto foi observado nas análises de DSC através do deslocamento dos picos de cristalização a frio do PET para temperaturas maiores e por uma redução na velocidade de cristalização a frio. A abordagem de Avrami foi utilizada para os estudos cinéticos em condições isotérmicas, mostrando que o processo de cristalização ocorre em dois estágios e que a constante de cristalização K diminuiu significativamente com a presença de poliestireno. Nas blendas PET/PS a presença de apenas 1% de PS retardou significantemente a cristalização do PET, em magnitude semelhante ao que ocorreu quando concentrações mais elevadas de PS foram utilizadas. Este comportamento é de grande importância industrial já que em baixa concentração de PS as propriedades mecânicas do PET não são afetadas, como também mostrado neste estudo. Palavras-chave: Cristalização isotérmica a frio, PET, poliestireno, blendas. The Reduction of the Cold Crystallization Rate of PET in the Presence of PolystyreneAbstract: The cold crystallization of PET and its blends with polystyrene (PS) was investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMA), scanning electron microscopy (SEM) and mechanical properties. PET/PS blends form separate phases, as confirmed by SEM and DMA, showing distinct phases and two glass transition temperatures. On the other hand, the determination of the equilibrium melting temperature of PET indicated that this parameter decreased when PS was added, suggesting that a limited solubility should exist. The presence of non crystallizable molecules like polystyrene, partially soluble in the PET crystallizable phase, reduces the driving force for crystallization. In the current study this effect was observed as a shifting of the cold crystallization DSC peaks to higher temperatures and also by the reduction in the rate of cold crystallization. The approach developed by Avrami was applied to study the kinetics of cold crystallization under isothermal conditions. It was shown that the crystallization occurs in two stages and that the rate constant K decreased significantly when PS was present. The blends containing only 1% of PS had the same magnitude of reduction in the rate of crystallization as the blends with higher PS content. This b...

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On the crystallization mechanism of poly(ethylene terepthalate) in its blends with poly(vinylidene fluoride)

Cited by 24 publications

References 34 publications

Physical Processes

Physical Processes

Effect of nucleating agents on crystallization kinetics of PET

Redução da velocidade de cristalização a frio do PET na presença de poliestireno

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