Disruptive processes in the shear crystallization of poly(ethylene oxide)

Fritzsche, A. K.; Price, Fraser P.; Ulrich, Robert D.

doi:10.1002/pen.760160311

Cited by 25 publications

(15 citation statements)

References 14 publications

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“…The apparatus used in these experiments has been explained in detail elsewhere [ 12, 13,161. It is, therefore, only necessary here to provide a summary of modifications made to the instrument prior to these experiments and present a brief description of the apparatus.…”

Section: Apparatusmentioning

confidence: 99%

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Effect of shear on the crystallization kinetics of poly(ethylene oxide) and poly(e‐caprolactone) melts

Sherwood

Price

Stein

1978

J. polym. sci., C Polym. symp.

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The effect of shear on polymer crystallization kinetics has been studied for three materials at several shear rates and degrees of supercooling. Two poly(ethylene oxide) samples, with molecular weights of 72, 200 and 12, 600, and a poly(e‐caprolactone) material, with a molecular weight of 9, 400, were investigated. The apparatus used was a concentric cylinder viscometer, which also functions as a dilatometer, capable of detecting very small volume changes on crystallization. The shear‐rate range of the experiments was 0 to 60 sec−1. Avrami kinetics were used to describe the transformation process and the exponent was found to increase from the quiescent value of 3 to a value greater than 5 with increasing shear rate for all materials studied. The acceleration in the transformation process was associated with a reduction in induction time. The value of induction time at high shear rates did not significantly decrease with increasing shear rate, indicating a saturation effect with shear. This was most pronounced in the low molecular weight samples. The value of induction time for the high molecular weight poly(ethylene oxide) sample, under identical experimental conditions, was substantially less than that of the low molecular weight material in all cases. Nuclei formation measurements were made for the crystallizing melt in a separate instrument. Nuclei formation under shear was very different from quiescent behavior and increased substantially with increasing shear rate. These experimental observations lead to the conclusion that accelerated crystallization is due to increased molecular chain extension and orientation under shear. This orientation greatly enhances the nucleation process, which is thought to be the rate controlling step in the crystalline transformation. This enhancement results in shorter induction times and more rapid crystallization.

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Section: Apparatusmentioning

confidence: 99%

“…A second instrument was used in this work to measure nucleation rates in a polymer sample under shear. The apparatus, which is described elsewhere [ 13,211, is a parallel-plate viscometer mounted on the stage of a polarizing microscope. Both plates are made of glass and nuclei are counted directly by a photographic technique.…”

Section: Apparatusmentioning

confidence: 99%

Effect of shear on the crystallization kinetics of poly(ethylene oxide) and poly(e‐caprolactone) melts

Sherwood

Price

Stein

1978

J. polym. sci., C Polym. symp.

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“…[22][23][24][25][26][27][28][29][30][31][32][33][34] The earliest work was reported by Treloar and Gent, who observed a decrease in the onset of crystallization for cross-linked natural rubber with increasing extension ratio. [22,23] Fritzsche et al investigated the crystallization kinetics of poly(ethylene oxide), PEO, under varying condition of shear rate and temperature.…”

Section: Introductionmentioning

confidence: 99%

“…[22,23] Fritzsche et al investigated the crystallization kinetics of poly(ethylene oxide), PEO, under varying condition of shear rate and temperature. [25,26] They found that the kinetics of the crystallization process was altered by shear, as indicated by a decrease in induction time and an elevation of the Avrami exponent. Haas and Maxwell studied the kinetics of crystallization for polyethylene, PE, under stress.…”

Section: Introductionmentioning

confidence: 99%

Shear‐Induced Crystallization and Shear‐Induced Dissolution of Poly(ethylene oxide) in Mixtures with Tetrahydronaphthalene and Oligo(dimethyl siloxane‐b‐ethylene oxide)

Madbouly

Wolf

2003

Macro Chemistry & Physics

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Cloud point temperatures (Tcp) and crystallization temperatures (Tl/s) were measured at different constant shear rates for the ternary system tetrahydronaphthalene/poly(ethylene oxide)/oligo(dimethyl siloxane‐b‐ethylene oxide) using a rheo‐optical device and in the case of Tl/s additionally a viscometer. This system enables for the first time a joint investigation of both transitions with a given mixture. Shear favors the homogeneous liquid state and the formation of crystals. Tcp (liquid/liquid demixing, UCST) shifts to lower and Tl/s (liquid/solid, segregation of PEO) to higher temperatures by several degrees as the shear rate,$\dot \gamma$, is increased up to 500 s−1. The normalized shift in Tcp fits well into previous results for high molecular weight blends, oligomer mixtures, polymer solutions in single solvents and low molecular weight mixtures. A phase separated near critical blend was examined 1 K below its Tcp by means of a shear cell (Linkam) in the quiescent state and under shear with respect to its morphology. Upon an increase in $\dot \gamma$one observes a transition from the co‐continuous structures existing in the quiescent state via deformed and oriented particles to string like morphologies. Finally, at sufficiently high shear rates the mixture becomes homogeneous and structures can no longer be seen under the microscope. The morphologies developing after the secession of shear are pointing to pronounced influences of the flow history of the system on the final structure of two phase blends.

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“…This phenomenon, apparently entailing a heterogeneous nucleation process, may only in extremely few cases be the result of lattice plane epitaxial crystallization due to proper matching of the lattice parameters of the additive with those of the crystallizing phase. It has been well recognized that flow is a significant variable affecting both the crystallization of polymers from their molten state and the resulting morphology [22,23,24,25,26]. It has been well recognized that flow is a significant variable affecting both the crystallization of polymers from their molten state and the resulting morphology [22,23,24,25,26].…”

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confidence: 99%

Polymer-metal halide interactions

Reimschuessel¹

1982

Colloid & Polymer Sci

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Zirconium tatrafluoride forms stable complexes with Nylon 6 and caprotactam entailing the amide moieties. In compositions up to 5% ZiF 4 the crystalline structure of the polyamide appears unaffected by the complexed chain segments formed during melt blending. These segments become upon solidification part of the amorphous regions of the polyamide. This molecular reinforcement results in significant increases in both yield stress and tensile modulus. The polyamide compositions are characterized by increased rates of nucleation and a stable, fine crystalline structure in the solid state.

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Disruptive processes in the shear crystallization of poly(ethylene oxide)

Cited by 25 publications

References 14 publications

Effect of shear on the crystallization kinetics of poly(ethylene oxide) and poly(e‐caprolactone) melts

Effect of shear on the crystallization kinetics of poly(ethylene oxide) and poly(e‐caprolactone) melts

Shear‐Induced Crystallization and Shear‐Induced Dissolution of Poly(ethylene oxide) in Mixtures with Tetrahydronaphthalene and Oligo(dimethyl siloxane‐b‐ethylene oxide)

Polymer-metal halide interactions

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