The kinetics of isothermal cold crystallization and tensile properties of poly(ethylene terephthalate)

Wellen, Renate Maria Ramos; Rabello, Marcelo S.

doi:10.1007/s10853-005-3173-3

Cited by 81 publications

(60 citation statements)

References 28 publications

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“…It is very well know that morphology and crystallinity have a great influence on polymer performance 21 . To assess the effect of HV content on crystallinity, thin films were removed from the moulded surfaces and tested by DSC.…”

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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“…The melting point and decomposition temperatures were found to decrease with increased amount of zeolites used, sugesting that the components of the samples decomposed were PP, while the zeolite remained intact. Overall, it can be seen that the melting points of the reinforced samples are higher than that of unreinforced sample, indicating that some of the heat was absorbed by the zeolite [22].…”

Section: Resultsmentioning

confidence: 97%

Mechanical and Thermal Properties of Polypropylene Reinforced by Calcined and Uncalcined Zeolite

Bukit¹

2013

MST

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This study was carried out to compare mechanical and thermal properties of polypropylene (PP) reinforced with uncalcined and calcined zeolites. The PP samples were reinforced with zeolites at various quantities of 2, 4, and 6 (wt %). The comparison of the two types of zeolite was based on mechanical properties, including tensile strength, elongation at break, and Young's modulus, and thermal characteristics analyzed using DSC, and DTA/TGA technique. The results obtained clearly revealed that both zeolites were able to significantly increase tensile strength and Young's modulus of the samples, with calcined zeolite was found to work better. Addition of calcined zeolite was found to result in increased fracture elongation of the samples reinforced with up to 4 wt% zeolite but decreased sharply for the sample reinforced with 6 wt% zeolite, while for the samples reinforced with uncalcined zeolite, no consistent trend was observed. Thermal analyses demonstrated that the samples reinforced with calcined zeolite are more resistant to thermal treatment than those reinforced with uncalcined zeolite, as indicated by their higher decomposition temperature. DSC analysis revealed that there was no significant difference of the melting points of the samples was observed, but the effect of the quantity of zeolite on enthalphy was quite evident, in which the enthalpies of the samples reinforced with calcined zeolites were relatively lower than those of the samples reinforced with uncalcined zeolites. Abstrak Sifat Mekanik dan Termal dari Polipropilena Diperkuat dengan Zeolit Tanpa Kalsinasi dan Zeolit Kalsinasi.Penelitian ini bertujuan untuk membandingkan zeolite tanpa kalsinasi dan yang dikalsinasi sebagai penguat polipropilena (PP). Sampel PP diperkuat dengan zeolite dengan jumlah yang berbeda, yakni 2, 4, dan 6% berat. Sifat mekanik yang diamati adalah kekuatan tarik, perpanjangan putus dan modulus Young. Sifat termal dianalisis dengan menggunakan DSC dan DTA/TGA. Dari hasil penelitian ini diperoleh kekuatan tarik dan modulus Young zeolit kalsinasi meningkat. Perpanjangan putus pada penambahan zeolit sampai 4% mengalami peningkatan namun terjadi penurunan pada penambahan 6%. Zeolit tanpa kalsinasi menunjukan perpanjangan putus lebih rendah dari zeolit kalsinasi. Analisis termal dengan DTA/TGA pada zeolit kalsinasi memiliki daya tahan termal lebih tinggi dibandingkan dengan zeolit tanpa kalsinasi, yang ditandai dengan peningkatan temperatur dekomposisi zeolit kalsinasi. Dari analisis DSC didapatkan bahwa tidak ada perbedaan yang sigifikan antara titik lebur sampel, namun sampel yang diberi zeolite kalsinasi memiliki entalpi yang relatif lebih rendah.

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“…O estudo da cinética de cristalização foi realizado sob condições isotérmicas através de um rápido aquecimento ( 100 °C.min -1 ) da temperatura ambiente até a temperatura alvo de cristalização isotérmica seguindo-se procedimentos anteriores [10] . A exoterma de cristalização foi registrada em função do tempo até que nenhuma variação com respeito à linha base fosse observada.…”

Section: Dsc E Cinética De Cristalizaçãounclassified

“…Para cada temperatura foram realizados 2 ensaios. A partir dos termogramas dados cinéticos como velocidade de cristalização e curva de Avrami foram calculados de acordo com o procedimento descrito anteriormente [10] .…”

Section: Dsc E Cinética De Cristalizaçãounclassified

“…A utilização de grades de alto peso molecular [6,7] como também a adição de diferentes polímeros como o policarbonato [8] e o poli(naftalato de etileno) (PEN) [9] reduziram a velocidade de cristalização do PET. Em trabalho anterior [10] , os presentes autores avaliaram a cinética de cristalização a frio de chapas extrudadas de PET, observando que a velocidade de cristalização é fortemente dependente da temperatura e o comportamento mecânico do material é afetado pela estrutura cristalina obtida.…”

Section: Introductionunclassified

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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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The kinetics of isothermal cold crystallization and tensile properties of poly(ethylene terephthalate)

Cited by 81 publications

References 28 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

Mechanical and Thermal Properties of Polypropylene Reinforced by Calcined and Uncalcined Zeolite

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

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