Feinstrukturuntersuchungen am Schichtaufbau von extrudiertem Polypropylen

Dragaun, H.

doi:10.1007/bfb0117094

Cited by 8 publications

(3 citation statements)

References 5 publications

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“…When passing the water bath, the molten polymer solidifies and the morphology of the pipe wall is formed. As a result of the thermal conditions a gradient of temperature exists after entering the water bath, i.e., quenching occurs at the outer pipe wall where the melt is exposed to water, whereas the inner sections gradually crystallize . The resulting morphology, i.e., the degree of crystallinity, type and quantity of polymorphs and the crystallite size distribution can be controlled by nucleating agents .…”

Section: Introductionmentioning

confidence: 99%

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Spatially resolved monitoring of crystalline suprastructure and molecular orientation in α‐ and β‐nucleated polypropylene pipes using differential scanning calorimetry, infrared microscopy, and polarized light microscopy

Schuster

Rode

Brüll

et al. 2013

J of Applied Polymer Sci

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Differently nucleated polypropylene (PP) pipes were studied by polarized light and infrared (IR) microscopy and differential scanning calorimetry (DSC). Although Fourier transform IR microscopy (mFTIR) excels by high spatial resolution and ease of measurement over the classical approach with manually prepared sections and individual analysis, a disadvantage is that the vibrational bands used to calculate the degree of crystallinity may be influenced by the polymorphism of PP. While this does not play a role for the a-polymorph, in the case of b-nucleated PP the calculated profile of crystallinity derived from the so called crystallinity bands depends on the direction of inspection. We could show that in the case of b-nucleation the results from mFTIR and DSC of cross-sections can be correlated, and thus the crystallinity profile obtained from mFTIR becomes independent from the direction of consideration. Consequently the advantages of mFTIR with regard to spatial resolution and reproducibility can now be exploited for b-nucleated PP as well. Using the differently nucleated specimen we give the first practical validation of a previously on a theoretical basis derived model to determine the molecular orientation in all three dimensions (machine, transverse, and normal). It could be shown that the profiles of molecular orientation are a function of both, the extrusion process with its post extrusion cooling conditions, and the type of nucleating agent.

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Section: Introductionmentioning

confidence: 99%

“…Polarized light microscopy (PLM) is widely used to analyze the morphological structure with regard to type and size of spherulites . Particularly, the “core–shell” structure formed in polymer pipes can be studied …”

Section: Introductionmentioning

confidence: 99%

Spatially resolved monitoring of crystalline suprastructure and molecular orientation in α‐ and β‐nucleated polypropylene pipes using differential scanning calorimetry, infrared microscopy, and polarized light microscopy

Schuster

Rode

Brüll

et al. 2013

J of Applied Polymer Sci

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“…The study on morphology in pipe extrusion was limited to a single set of L and N, specifically to isotactic polypropylene, i-PP. 6 It is the intent of this paper, to relate changes in morphology1' (surface and bulk) of pipe fabricated from extrusion grade high density polyethylenes, (HDPE), I-PP, with N and L where the ratio, N/L, is variable. Correlation of N and L with overall dimensional stability, surface quality, crystallinity, and density are made.…”

Section: Introductionmentioning

confidence: 99%

Extrusion process for polyethylene pipe: Dependence of morphology on the process parameters

et al. 1987

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Shear‐induced β‐form crystallization in isotactic polypropylene

Dragaun¹,

Hubeny²,

Muschik³

1977

J. Polym. Sci. Polym. Phys. Ed.

119

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SynopsisExtruded, injection-molded, unoriented crystallized specimens and capillary rheometer efflux strands of commercially stabilized polypropylene without nucleating agents were examined by optical microscopy and x-ray diffraction to determine the conditions for ,%form crystallization as a function of the distance from the surface and of the shear rate at commercial processing conditions. Results demonstrate that a t all "cooling conditions" AT = T,,, -Tb (defined as the melt temperature T , minus the bath temperature Tb) effects of strain flow initiate nucleation of &form crystals. The shear rate is demonstrated to be important for &form crystallization. A critical average threshold value for the shear rate of approximately 3 X lo2 sec-l has to be exceeded. The 0 modification is mostly connected with type-I11 spherulites and partly to row structures, and it is observed at processing conditions in oriented structures only.

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Feinstrukturuntersuchungen am Schichtaufbau von extrudiertem Polypropylen

Cited by 8 publications

References 5 publications

Spatially resolved monitoring of crystalline suprastructure and molecular orientation in α‐ and β‐nucleated polypropylene pipes using differential scanning calorimetry, infrared microscopy, and polarized light microscopy

Spatially resolved monitoring of crystalline suprastructure and molecular orientation in α‐ and β‐nucleated polypropylene pipes using differential scanning calorimetry, infrared microscopy, and polarized light microscopy

Extrusion process for polyethylene pipe: Dependence of morphology on the process parameters

Shear‐induced β‐form crystallization in isotactic polypropylene

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