Kinetic Model of Polymer Degradation Occurring during Extrusion Process

El'darov, E.G.; Mamedov, F.V.; Gol'dberg, V.M.; Заиков, Г. Е.

doi:10.1080/00914039508009674

Cited by 4 publications

(5 citation statements)

References 2 publications

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“…4(a)]. Comparison of this significant endothermic absorption with those observed in Figure 2(a) and 3(a), where the curves were completely flat and with slight absorption endotherm, respectively, leads us to propose three possible hypotheses: appearance of a new product formed by chemical reaction (polymerization or breakdown) during extrusion, due to high shear and temperature17, 18; appearance of a crystalline structure19; appearance of an organized noncrystalline structure 20 …”

Section: Resultsmentioning

confidence: 70%

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Influence of hot‐melt extrusion and compression molding on polymer structure organization, investigated by differential scanning calorimetry

Sarraf¹,

Tissot²,

Tissot³

et al. 2001

J of Applied Polymer Sci

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A blend of a pullulan polymer and 1,2,6-hexanetriol as a plasticizer were used to study the effect of melt processing techniques on the physical properties of the resulting materials. The main advantage of pullulan is its linear polysaccharide chain model structure. Hot-melt extrusion and compression molding were performed under the same temperature and pressure conditions. The materials obtained were analysed by differential scanning calorimetry. For the first time, the comparative effect of the two processing techniques, i.e., extrusion and compression molding, on the polymer arrangement is reported. Endothermic events resulted from the melt extrusion process were shown to be related to different structures of oriented populations of macromolecules and to microphase separation. Orientation was enhanced by cooling the extrudate at the die exit, with a corresponding increased enthalpy from 34.7 to 51.4 J/g. In contrast, when using compression molding, the endotherm was less marked (11.9 J/g), suggesting less orientation, but the shape of the thermogram was quite similar to that of the extrudate. In both cases, we observed a loss of orientation when the molded materials were milled. A semiquantitative kinetic study of the disorientation process of the extrudate upon isothermic tempering suggests that a disorientation phenomenon occurs at the same time as a swelling process due to the presence of microphase separation. The extrudate was shown to be stable at 25°C.

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Section: Resultsmentioning

confidence: 70%

“…appearance of a new product formed by chemical reaction (polymerization or breakdown) during extrusion, due to high shear and temperature17, 18;…”

Section: Resultsmentioning

confidence: 99%

Influence of hot‐melt extrusion and compression molding on polymer structure organization, investigated by differential scanning calorimetry

Sarraf¹,

Tissot²,

Tissot³

et al. 2001

J of Applied Polymer Sci

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“…According to Equation (1) and Figure 6, a linear model can be written to correlate the MI of the pellet, the MI of the powder and the peroxide concentration, as performed for Extruder B. For Equation (5), the following results are obtained: R 2 ¼ 0.972, b 1 ¼ 0.384 AE 0.037 and b 2 ¼ 1.06 AE Figure 13. Experimental MWD for the PP processed in Extruder A without addition of peroxide and with 0.0325% of HDPE (case 1 of Table 1).…”

Section: Simplified Models For Extruder Bmentioning

confidence: 99%

“…This can be attributed to the interferences caused by polymer melt in the rheometer, for instance the accumulation of material and calibration problems that induce inaccuracy in the measurements. Therefore, it seems reasonable to say that the estimates for the MI values obtained from the model [Equation (5)] are more reliable than the values provided by the rheometer. This also provides a simple, reliable and cheap technique for continuous in-line monitoring of the MI of the polymer pellets.…”

Section: In-line Controlmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10] Usually, the kinetic mechanisms proposed to explain the controlled polymer degradation are complex and include steps such as chain scission (promoted by free radicals, by spontaneous thermal decay or by the action of shear), chain transfer (when radicals transfer activity to other molecules) and chain termination (when radicals lose activity). Although the number of studies on this subject is large, some questions of practical and theoretical relevance regarding the degradation mechanisms remain open for discussion.…”

Section: Introductionmentioning

confidence: 99%

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Controlled Degradation of Poly(propylene) in Industrial Extruders

Oliveira

Biscaia

Fadigas

et al. 2006

Macro Materials & Eng

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Summary: The main objective of this work was to study the controlled degradation of PP in industrial extruders at different operating conditions. Firstly, the investigation of certain key polymer properties, such as the MI and the MWD, revealed that the changes undergone by the polymer resin during the reactive extrusion depend strongly on the operating conditions. In the absence of oxygen, the results indicated that spontaneous thermal and/or mechanical degradation were not very important. Therefore, resin properties were not expected to change during extrusion if no peroxide was fed into the extruder, in the absence of oxygen. On the other hand, in the presence of oxygen, MWD analysis showed that the MWD could be shifted towards higher or lower molecular weights, indicating that both chain growth and chain scission were possible during extrusion. Finally, simple expressions are presented here in order to allow for the monitoring and control of the important final properties of the extruded resin.The molecular weight distribution of polymer powder and polymer pellets during extrusion.imageThe molecular weight distribution of polymer powder and polymer pellets during extrusion.

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