Melt rheology of aliphatic hyperbranched polyesters

Vuković, Jovana S.; Jovanović, Slobodan; Lechner, M. D.; Vodnik, Vesna

doi:10.1002/app.29836

Cited by 21 publications

(31 citation statements)

References 39 publications

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“…Since linear polymers show constant activation energies regardless of molar mass , the increase indicates an increasing extent of branching . The high values of the activation energies found are comparable to values of 174–215 kJ mol −1 reported for other branched polyesters . The authors explain that interactions of polar groups such as the OH and COOH end groups of the PET grades considered here can cause a more pronounced viscosity decrease at higher temperatures.…”

Section: Resultssupporting

confidence: 83%

Analysis of high melt‐strength poly(ethylene terephthalate) produced by reactive processing by shear and elongational rheology

Kruse

Wang

Shah

et al. 2018

Polymer Engineering & Sci

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Three grades of poly(ethylene terephthalate) (PET) produced by different synthesis routes and with different molar masses were reactively extruded with two tetra‐functional chain extenders, i.e., pyromellitic dianhydride (PMDA) and tetraglycidyl diamino diphenyl methane (TGDDM). The preferred reactivity of the coupling agents led to different long‐chain branched (LCB) structures, which can be related to different hydroxyl and carboxyl end group concentrations of the PET grades investigated. The complex viscosity and the transient elongational viscosity increased by up to two decades. Both the activation energy of flow and the loss angle indicate long‐chain branching. A more quantitative assessment of the extent of strain hardening was achieved by application of the molecular stress function (MSF) model. The two material parameters of the model revealed different behaviors depending on the chain extender used. The initial molar mass of PET and the concentration of end groups, i.e., hydroxyl and carboxyl, determine the structure of the polymer molecules. PMDA proved to be an excellent coupling agent for industrial processing which induces reproducibly either a star‐like, comb‐like, or randomly branched structure depending on the concentration of coupling agent added and the hydroxyl concentration of the PET employed. TGDDM led to a hyperbranched structure. POLYM. ENG. SCI., 59:396–410, 2019. © 2018 Society of Plastics Engineers

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Section: Resultssupporting

confidence: 83%

Analysis of high melt‐strength poly(ethylene terephthalate) produced by reactive processing by shear and elongational rheology

Kruse

Wang

Shah

et al. 2018

Polymer Engineering & Sci

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“…With increasing generation number, the behavior slowly approached a terminal behavior with G ″ ∼ ω 0.9 , i.e., close to the terminal scaling, whereas the scaling exponent for G ′ was around one. These results are in agreement with non‐terminal G ′ and G ″ scaling that was previously reported for dendritic polymers and for HB polyesters . These results indicate that synthesized HB polyesters exhibited slower relaxation modes compared with those for most linear polymers as a consequence of the high branch density and intermolecular interactions.…”

Section: Resultssupporting

confidence: 91%

“…It was observed that the values of the thermal coefficient of expansion, α f , and the fractional free volume, f g , increase with increasing size or pseudo‐generation of the HB polyesters due to the increasing freedom of movement of the existing branches. This trend was identical and the values of α f and f g were similar to those found earlier for other HB polyesters . Such a trend is in accordance with the observed decrease in E a with generation number and suggests that the flexibility is increased because the hydrogen bonding is less pronounced.…”

Section: Resultssupporting

confidence: 91%

Rheological properties of hydroxyl‐terminated and end‐capped aliphatic hyperbranched polyesters

Dunjic

Tasic²,

Bozic

et al. 2014

J of Applied Polymer Sci

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The rheological behavior of two series of aliphatic hyperbranched (HB) polyesters, based on 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and di-trimethylol propane (Di-TMP) as a tetrafunctional core, was studied. The effect of the size (pseudogeneration number, from second to eight) and structure on the melt rheological properties was investigated for a series of hydroxylterminated HB polyesters. In addition, the influence of the nature and degree of modification of the terminal OH groups in a series of fourth-generation polyesters end-capped with short and long alkyl chains and some aryl groups on the rheological properties was analyzed. The time-temperature superposition procedure was applied for the construction of master curves and for the analysis of the rheological properties of HB polyesters. The data obtained from WLF analysis of the HB polyesters showed that the values of the thermal coefficient of expansion of free volume a f and the fractional free volume at the glass transition temperature, f g , increase with increasing size of the HB polyesters. It was shown that the modified HB polyesters exhibited lower T g and T G 0 5G 00 temperatures, above which viscous became dominant over elastic behavior. From an analysis of the master curves of the modified HB polyesters, it was observed that with increasing degree of modification, both storage and loss modules and complex dynamic viscosity and apparent energy for viscoelastic relaxation decrease, because of reduced intermolecular hydrogen interactions. They do not exhibit a plateau of rubbery behavior, which confirms that no entanglements are present and that the molar masses are below the critical molar mass.

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“…The DSC curves of the synthesized PU samples obtained during the first and second heating runs are shown in Fig. 31 The T g values of the PUs synthesized in this work, determined during the second heating run, were in the range from 50 to 58 °C (Table II) content. The broad endothermic peak around 150 °C, observed in the DSC curves during the first heating run, corresponds to H-bond interactions in PU samples.…”

Section: Thermal Properties Of the Synthesized Polyurethane Networkmentioning

confidence: 83%

Poly(urethane-siloxane)s based on hyperbranched polyester as crosslinking agent: Synthesis and characterization

Pergal¹,

Dzunuzovic²,

Ostojić

et al. 2012

JSCS

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A series of novel polyurethane crosslinked structures (PUs) was prepared from α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO), 4,4’-methylenediphenyl diisocyanate and Boltorn® hyperbranched polyester of the third pseudo generation. The hydroxyfunctional hyperbranched aliphatic polyester with 26 end groups was used as crosslinking agent. In order to improve the compatibility of all reactants during the synthesis, PU samples were prepared by a step-growth polymerization in two stages in solution. The soft EO-PDMS-EO segment content was varied in the range from 15 to 40 wt.%. The influence of the EO-PDMS-EO content on the swelling behavior, crosslinking density, hardness, thermal and surface properties of the synthesized PUs was investigated. The structure of the synthesized polyurethanes was confirmed by the presence of specific bands in Fourier transform infrared spectra. Swelling studies were carried out to determine the crosslinking density and polyurethane networks with lower EOPDMS- EO content revealed higher crosslinking density. The glass transition temperature of the synthesized PUs, determined by differential scanning calorimetry, slightly increased from 50 to 58°C by decreasing EO-PDMS-EO content as a consequence of higher crosslinking density of samples. The increase of EO-PDMS-EO content leads to the better thermal stability, as it was confirmed by the value of the starting temperature of thermal degradation. The surface of the polyurethane networks became more hydrophobic with increasing EO-PDMS-EO content. The surface morphology of synthesized polyurethanes was analyzed by scanning electron microscopy

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Melt rheology of aliphatic hyperbranched polyesters

Cited by 21 publications

References 39 publications

Analysis of high melt‐strength poly(ethylene terephthalate) produced by reactive processing by shear and elongational rheology

Analysis of high melt‐strength poly(ethylene terephthalate) produced by reactive processing by shear and elongational rheology

Rheological properties of hydroxyl‐terminated and end‐capped aliphatic hyperbranched polyesters

Poly(urethane-siloxane)s based on hyperbranched polyester as crosslinking agent: Synthesis and characterization

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