Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 1. Kinetik, Molekulargewichtsabhängigkeit und Frage des Bruchmechanismus

Müller, H. G.; Klein, Joachim

doi:10.1002/macp.1981.021820219

Cited by 14 publications

References 25 publications

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Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln

1981

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Mechanical shear degradation of poly(decyl methacrylate), (viscosity average molecular weight in tetrahydrofuran M,, = 1,3 . 1 06, M,/M, = 5) in the thermodynamically good solventtetrahydrofuran has been studied in turbulent flow through a capillary as a function of polymer concentration in the range from 0,22 to 8,9 g/100 cm3. Due to turbulent flow conditions the shear stress, shear rate and shear energy proved to be the same for all concentrations and remained constant during degradation, giving a general insight into mechanism of degradation. The rate of degradation has been followed using molecular weight distribution curves obtained by gel permeation chromatography. The reaction was found to be of first order. Rate constants determined for molecular weights from 3,2 -9,5 . 106 decreased with increasing concentration following a law of the type ki = (K + b -c ) -' , K and b being constants for each molecular weight. Hydrodynamic volumes of polymer molecules have been calculated according to models of Rudin as function of molecular weight and concentration. It can be shown that rate constants of degradation and calculated hydrodynamic volumes are proportional for the whole range of molecular weight and concentrations up to 3,6 g/100 cm3. There is also a rather good proportionality between these rate constants and the volumes of polymer coils predicted by de Gennes. This result is an additional confirmation of the concept that hydrodynamic volume governs shear degradation of polymer solutions. Additional experiments show that this type of concentration dependence is also to be found for other polymers in other solvents.

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Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln

1981

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Mechanical shear degradation of polymers in solution by turbulent flow, 3. The influence of chemical constitution and thermodynamic quality of the solvent on shear degradation

Müller

Klein

1981

Makromol. Chem.

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Mechanical shear degradation of polyisobutylene, polystyrene, poly(viny1 chloride), poly-(methyl methacrylate), poly(decy1 methacrylate), poly(methy1 acrylate), and 1,4-polybutadiene in dilute solutions of tetrahydrofuran (THF) are studied under turbulent flow conditions through a capillary, in order to study the effect of the chemical constitution on shear degradation. In addition the influence of solvent quality on shear degradation is investigated. The changes of the molecular weight distribution curves were followed by gel permeation chromatography (GPC), in order to determine the degradation constants ki for the corresponding molecular weight distribution fractions Mi. GPC calibration via the concept of universal calibration, Mark-Houwink relations for polyisobutylene, poly(methy1 methacrylate), poly(methy1 acrylate), I ,4-polybutadiene, and poly(dimethylsi1oxane) in T H F as solvent had to be established for this purpose. Substantial differences in the rate constants ki were observed as a function of Mi, whereas a master curve resulted for all polymers except I ,4-polybutadiene when ki was plotted against the number of main chain carbon atoms ii for each molecular weight Mi. From this the shear degradation of C-C single bond polymers can be represented by ki = C . if, C being independent of the chemical nature of the C-C single bond polymer, and a varying from I ,7 to 2,6. This means that in addition to the shape of the deformed macromolecule to be degraded not only its hydrodynamic volume (in rest) but also its chain length plays an important role. As to the influence of solvent quality, the degradation constants were found to increase with decreasing solvating power of the solvent. Mechanical shear degradation of the type discussed here takes place in drag reduction by polymers. a) Teil 2: cf. 2 5 ) . b, Jetzige Adresse: Bayer AG Leverkusen, Abt. FE-DPP-PA, 5090 Leverkusen. 0025-1 I6X/8

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Non‐newtonian flow behaviour of poly(decyl methacrylate) solutions

Herold

Wolf

1983

Makromol. Chem.

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The viscosity of solutions of poly(decy1 methacrylate)s, PDMA, in I-pentanol (thermodynamically poor solvent) and in toluene or isooctane (good solvents) was measured up to shear rates of 3 . 1 @ s-I by means of rotational viscosimeters. The observed pronounced shear thinning is for all solutions well described by the theory of Graessley, with the extension, introduced by Ito. Two parameters, resulting from the evaluation of the flow curves on the basis of the above theory, are discussed: r,, a characteristic relaxation time of the polymer chain, is found to be in the range of ms. qfric, a frictional parameter, independent of shear rate, amounts up to 50% of the zero-shear viscosity for the measured solutions. Both, T,, and qfric, increase with decreasing solvent quality, increasing molecular weight, and increasing concentration, in accord with theory. A comparatively sharp downward bend, separating two power-law regimes, shows up with moderately concentrated solutions, as the shear rate exceeds about Id to 1@ S K I . This transition is tentatively interpreted as an orientation of the long side chains of PDMA.

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Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 1. Kinetik, Molekulargewichtsabhängigkeit und Frage des Bruchmechanismus

Cited by 14 publications

References 25 publications

Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln

Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln

Mechanical shear degradation of polymers in solution by turbulent flow, 3. The influence of chemical constitution and thermodynamic quality of the solvent on shear degradation

Non‐newtonian flow behaviour of poly(decyl methacrylate) solutions

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