Linear and branched poly(butyleneterephthalate): Activation energy for melt flow

Munari, Andrea; Pilati, Francesco; Pezzin, G.

doi:10.1007/bf01462502

Cited by 9 publications

(10 citation statements)

References 9 publications

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“…The activation energy E a determined for linear samples ( 1 4 -15 kcal/mol) is a little, but significantly, lower than that of highly branched samples ( 1 8 -2 0 kcal/mol). A larger increase of E a was found for branched PBTP samples [6], containing smaller quantities of the trifunctional co-monomer than in the present case of highly branched PET. The stronger increase in the activation energy in the case of PBTP may be attributed to the longer branches for the same/XS/w.…”

Section: F ) ----contrasting

confidence: 46%

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Rheological characterization of highly branched poly(ethyleneterephthalate)

Munari

Pezzin²,

Pilati

et al. 1989

Rheol Acta

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Linear and highly branched poly(ethyleneterephthalate) samples were synthesized and characterized in terms of intrinsic viscosity, molecular weight and melt viscosity over a wide range of shear rates at several temperatures, in the range from 265 ° to 295 °C. Linear samples exhibited Newtonian behavior over a wide range of shear rates, while the branched ones became shear thinning at relatively low shear rates. Our experimental data, as well as data previously reported, were found to be described by a proposed correlation between the melt viscosity ratio and a branching index. Moreover, the activation energy for melt flow was found for the highly branched samples to be a little higher than that of the linear samples.

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Section: F ) ----contrasting

confidence: 46%

“…This result seems interesting in light of recent discussions [5] concerning the applicability of the reptation theory to the flow of branched polymers. For PBTP, moreover, it was found that the activation energy for melt flow was sensibly larger for branched than for linear samples [6].…”

Section: Introductionmentioning

confidence: 98%

Rheological characterization of highly branched poly(ethyleneterephthalate)

Munari

Pezzin²,

Pilati

et al. 1989

Rheol Acta

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“…In addition, when Newtonian behavior is found below a certain value of shear rate, an Arrhenius-type equation correlates the Newtonian viscosity r/0 with temperature [10,11,13,14]:…”

Section: Resultsmentioning

confidence: 99%

“…As far as the activation energy for melt flow is concerned, it is known from the literature that both for polydisperse randomly branched and monodisperse Y-shaped polymers [ 1 -8] its value appears to be substantially larger than for the corresponding linear samples, whereas for nearly monodisperse starbranched polymers the activation energy is not in all cases enhanced by branching [ 9 -1 2 ] . Recently, the present authors have found that for polydisperse randomly branched poly(butyleneterephthalate) [13] and poly(ethyleneterephthalate) [14] samples, the activation energy was increased by the presence of long branches. It is the purpose of the present paper to report the results of a careful investigation on the influence of branching on the temperature coefficient of melt flow for poly(butyleneisophthalate) (PBIP), whose melt viscosity-branching index relationship has been described recently [15].…”

Section: Introductionmentioning

confidence: 89%

Linear and branched poly(butyleneisophthalate): Activation energy for melt flow

1990

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Several poly(butyleneisophthalate)s of different molecular weight, both linear and randomly branched, were synthetized by bulk polymerization and studied in the molten state with a capillary rheometer in the temperature range 190-220 °C. The viscosity shift factors showed to be well correlated to temperature by an Arrhenius-type equation. The melt-flow activation energy at constant shear stress E~ was found to be 15+1 kcal/mol for both linear and branched samples, whereas for polydisperse poly(butyleneterephthalate) and poly(ethyleneterephthalate) it was found previously that random long-chain branching substantially increases the activation energy.An analysis of our results and of those available in the literature shows that the influence of branches on the temperature coefficient of viscosity of polymers is still a subject open to discussion.

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“…1 Therefore, in previous investigations some of us dealt with the synthesis and molecular and rheological characterization of linear and branched poly(butylene terephtalate) (PBT), [2][3][4][5] poly(ethylene terephthalate) (PET), 6 and poly(butylene isophthalate) (PBI). [7][8][9] Subsequently, given that it is well known that the presence of branches markedly changes the crystallization kinetics and melting behavior of linear polymers, the crystallization behavior of branched PBT was also investigated.…”

Section: Introductionmentioning

confidence: 99%

Influence of branching on the thermal behavior of poly(butylene isophthalate)

Finelli

Lotti

Munari

2002

J of Applied Polymer Sci

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ABSTRACT:The thermal behavior of linear and randomly branched poly(butylene isophthalate) samples was investigated by thermogravimetric analysis and differential scanning calorimetry. As to the thermal stability, it was found to be good and similar for all the samples. The thermal analysis carried out using DSC technique showed that the melting temperature of the polymers decreased with increasing branching unit content, although the glass-transition temperature was practically not affected by ramifications. The multiple endotherms typical of linear PBI were also observed in branched samples and were found to be influenced both by temperature and degree of branching. By applying the Hoffman-Weeks' method, the equilibrium melting temperatures of the polymers were obtained. The presence of a crystal-amorphous interphase was evidenced only for the branched samples and the interphase amount was found to increase as the branching unit content was increased. Isothermal melt crystallization kinetics was analyzed according to Avrami's treatment. The introduction of branching points was found to decrease the overall crystallization rate of poly(butylene isophthalate). Values of Avrami's exponent n close to 3 were obtained for all the samples, in agreement with a crystallization process originating from predetermined nuclei and characterized by three dimensional spherulitic growth.

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Linear and branched poly(butyleneterephthalate): Activation energy for melt flow

Cited by 9 publications

References 9 publications

Rheological characterization of highly branched poly(ethyleneterephthalate)

Rheological characterization of highly branched poly(ethyleneterephthalate)

Linear and branched poly(butyleneisophthalate): Activation energy for melt flow

Influence of branching on the thermal behavior of poly(butylene isophthalate)

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