Evaluation of Philips and Ziegler–Natta high-density polyethylene degradation during processing in an internal mixer using the chain scission and branching distribution function analysis

Pinheiro, Luís Antônio; Chinelatto, Marcelo Aparecido; Canevarolo, Sebastião V.

doi:10.1016/j.polymdegradstab.2006.04.005

Cited by 29 publications

(27 citation statements)

References 25 publications

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“…In a study by Hoàng et al [97] it was shown that polymers with higher levels of chromium catalyst residues were less stable, however, in this case the initial vinyl unsaturation appeared to have a more dramatic influence on the initial rate of oxidation of the chromium-type polymers. According to Pinheiro et al [98] Phillips HDPE mainly shows chain branching, while Z-N HDPE preferentially undergoes chain scission. This difference was attributed to the lower concentration of unsaturations in the Z-N HDPE.…”

Section: -Degradation During Processingmentioning

confidence: 99%

“…Peroxide concentrations as calculated according to the above-mentioned equations (lines) and determined by an iodometric method (points) during a peroxide decomposition experiment at 70 °C with polypropylene pre-oxidized for several times at 70°C [108] Reprinted from Polymer Degradation and Stability, Vol 51, P. Gijsman, J. Hennekens and J. Vincent, The mechanism of the low-temperature oxidation of polypropylene, [95][96][97][98][99][100][101][102][103][104][105]1993, , with permission from Elsevier This decay could not be described with first or second order decomposition kinetics. Assuming that the titrated concentration of peroxides consists of two fractions (both decomposing according to first order kinetics), the calculated data could be fitted with the experimental values (see Fig.…”

Section: Fig 12mentioning

confidence: 99%

“…Also shown are the measured peroxide concentration (∆) and the calculated concentration of rapidly decomposing peroxides (+) after the above mentioned decomposition times. Reprinted from Polymer Degradation and Stability, Vol 51, P. Gijsman, J. Hennekens and J. Vincent, The mechanism of the low-temperature oxidation of polypropylene, [95][96][97][98][99][100][101][102][103][104][105]1993, with permission from Elsevier.…”

Section: Fig 12mentioning

confidence: 99%

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Review on the thermo-oxidative degradation of polymers during processing and in service

Gijsman

2008

E-Polymers

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Section: -Degradation During Processingmentioning

confidence: 99%

Section: Fig 12mentioning

confidence: 99%

Section: Fig 12mentioning

confidence: 99%

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Review on the thermo-oxidative degradation of polymers during processing and in service

Gijsman

2008

E-Polymers

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“…Essa metodologia é chamada de função de distribuição de cisão de cadeia (CSDF) e foi utilizada para acompanhar a degradação termo-mecânica do polipropileno [2][3][4][5] e polietileno de alta densidade [6,7] durante a extrusão.…”

Section: Introductionunclassified

Cisão de cadeia na degradação termo-mecânica do poliestireno sob múltiplas extrusões

Cáceres

Canevarolo

2008

Polímeros

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Resumo: Determinou-se o número de cisões de cadeia gerado pela degradação termo-mecânica do poliestireno quando submetido a múltiplas extrusões. A degradação foi acompanhada pelas mudanças nas curvas de distribuição de massa molar. Seguindo-se o significado físico das massas molares médias de uma curva de MWD mostrou-se que a massa molar numérica media M n é a única que pode ser relacionada diretamente com o número de moléculas do sistema. A partir desta calculou-se o número de cadeias clivadas (ns) como uma relação entre a M n da amostra degradada e a virgem. A função de distribuição de cisão de cadeia (CSDF) mostra que o processo de degradação termo-mecânica do poliestireno submetido a múltiplas extrusões à 240 °C é do tipo aleatório, independente da massa molar inicial. Palavras-chave:Degradação termo-mecânica, extrusão, poliestireno, cisão de cadeia. Chain Scission in the Thermo Mechanical Degradation of Polystyrene under Multiple ExtrusionsAbstract: The number of chain scissions during thermo-degradation of polystyrene under multiple extrusions was calculated. The degradation produces changes in the molecular weight distribution MWD curves. Following the physical meaning of the average molecular weights of a MWD curve it was shown that the number average molecular weight M n is the only average that can be directly related to the number of molecules in the system. From that it was calculated the number of sectioned chains (ns) as a ratio between the number of chains in the degraded and original polymers. The chain scission distribution function (CSDF) shows that the thermo-mechanical degradation process of polystyrene under multiple extrusions at 240 °C is of a random type, independent of the initial molecular weight.Keywords: Thermo-mechanical degradation, extrusion, polystyrene, chain scission. IntroduçãoDurante o processo de propagação da cadeia radical na polimerização em cadeia os centro ativos da frente em crescimento se instabilizam e morrem aleatoriamente, o qual gera cadeias poliméricas com diferentes tamanhos, formando uma distribuição de tamanhos em torno de um valor mé-dio, o que exige uma curva de distribuição de massa molar (MWD) para representá-lo. A partir de 1964 [1] a cromatografia de exclusão por tamanho (SEC) tem sido extensivamente utilizada na caracterização de polímeros, através da obtenção das curvas de distribuição de massa molar (MWD). A análise das curvas de MWD pode ajudar no entendimento das propriedades físico-químicas dos polímeros incluindose a elucidação dos processos de degradação termo-mecâ-nica. Infelizmente a análise destas curvas é ainda difícil e não está completamente equacionada. Assim a maioria das publicações se restringe a analise das mudanças nas massas molares médias, não explorando apropriadamente todas as informações contidas em uma curva de MWD.Para melhor entender os processos de degradação que ocorrem durante o processamento termo-mecânico de um polímero foi proposta uma metodologia de cálculo [2,3] que permite quantificar o deslocamento total da curva de M...

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“…2,3 Today, research in this field has become increasingly important in helping manufacturers to tailor competitive wood products for a wider range of applications. [4][5][6][7][8][9][10][11][12][13][14][15][16] Two aspects must be considered: composite processing, since factors such as degradation and residence time are important parameters that influence properties, [17][18][19][20][21] and compatibility between the materials' phases. 7 Wood plastic composites (WPC) have limited applications due to the intrinsic properties of wood, such as its hydrophilicity and the relatively low dimensional stability of lignocellulosic components.…”

Section: Introductionmentioning

confidence: 99%

Optimization of wood flour acetylation by factorial design and partial least squares regression

Nadal¹,

Cararo²,

Pinheiro³

et al. 2012

Quím. Nova

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Recebido em 5/1/12; aceito em 17/5/12; publicado na web em 24/8/12Acetylation was performed to reduce the polarity of wood and increase its compatibility with polymer matrices for the production of composites. These reactions were performed first as a function of acetic acid and anhydride concentration in a mixture catalyzed by sulfuric acid. A concentration of 50%/50% (v/v) of acetic acid and anhydride was found to produced the highest conversion rate between the functional groups. After these reactions, the kinetics were investigated by varying times and temperatures using a 3 2 factorial design, and showed time was the most relevant parameter in determining the conversion of hydroxyl into carbonyl groups.

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Evaluation of Philips and Ziegler–Natta high-density polyethylene degradation during processing in an internal mixer using the chain scission and branching distribution function analysis

Cited by 29 publications

References 25 publications

Review on the thermo-oxidative degradation of polymers during processing and in service

Review on the thermo-oxidative degradation of polymers during processing and in service

Cisão de cadeia na degradação termo-mecânica do poliestireno sob múltiplas extrusões

Optimization of wood flour acetylation by factorial design and partial least squares regression

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