Hydrodynamically induced crystallization of polymers from solution

Pennings, A. J.; Mark, J. M. A. A. van der; Booij, H. C.

doi:10.1007/bf02086621

Cited by 214 publications

(75 citation statements)

References 22 publications

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“…Chain extension and alignment have also been achieved in polymer melts and solutions by the action of flow fields (see e.g. [10][11][12][13][14][15][16]). …”

Section: !Ntroduetionmentioning

confidence: 99%

“…The relatively rapid relaxation of macromolecules in the liquid state, however, can be inhibited by fixation of the oriented chains in a crystalline lattice. This was demonstrated in studies on hydrodynamically induced crystallization of polyethylene from supercooled solutions that were 0022-2461/80/020505-10503.00/0 subjected to flow [10][11][12][13][14]. In this process still some relaxation of the polymer molecules might have occurred, which can be judged from the properties of the crystals produced.…”

Section: !Ntroduetionmentioning

confidence: 99%

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Ultra-high-strength polyethylene filaments by solution spinning/drawing

1980

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This paper deals with ultra-high-strength monofilaments of linear polyethylene that are produced by solution spinning and subsequent hot drawing at 120 ~ C. The influence of the draw ratio on the mechanical and thermal properties of the fibres was investigated. Some salient features of a polyethylene filament with a draw ratio of 31.7 are: tensile strength at break = 3.0 GPa, Young's modulus = 90 GPa and DSC-melting point at a scan speed of 10 ~ Cmin -1 = 145.5 ~ C. The modulus was found to depend linearly on the draw ratio. The tensile strength tended, by contrast, to approach an upper limit at high draw ratios. Additional morphological and X-ray studies revealed an extremely good orientation of the macromolecules in the fibre direction of the highly drawn polyethylene monofilaments.

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“…Chain extension and alignment have also been achieved in polymer melts and solutions by the action of flow fields (see e.g. [10][11][12][13][14][15][16]). …”

Section: !Ntroduetionmentioning

confidence: 99%

Section: !Ntroduetionmentioning

confidence: 99%

Ultra-high-strength polyethylene filaments by solution spinning/drawing

1980

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“…In the 1970s, the shish-kebab morphology under elongation flow in polymer solutions and melts was widely investigated. [1][2][3][4] The study of isotactic polypropylene (iPP) under flow has generated particular interest because iPP is an important commodity polymer. Considerable efforts have been devoted to shear-induced crystal structural changes in iPP with wide-angle X-ray diffraction (WAXD).…”

Section: Introductionmentioning

confidence: 99%

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

Yang

Somani

et al. 2001

J Polym Sci B Polym Phys

145

105

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Crystallization studies at quiescent and shear states in isotactic polypropylene (iPP) containing nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules were performed with in situ small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). DSC was used to characterize the quiescent crystallization behavior. It was observed that the addition of POSS molecules increased the crystallization rate of iPP under both isothermal and nonisothermal conditions, which suggests that POSS crystals act as nucleating agents. Furthermore, the crystallization rate was significantly reduced at a POSS concentration of 30 wt %, which suggests a retarded growth mechanism due to the molecular dispersion of POSS in the matrix. In situ SAXS was used to study the behavior of shear-induced crystallization at temperatures of 140, 145, and 150°C in samples with POSS concentrations of 10, 20, and 30 wt %. The SAXS patterns showed scattering maxima along the shear direction, which corresponded to a lamellar structure developed perpendicularly to the flow direction. The crystallization half-time was calculated from the total scattered intensity of the SAXS image. The oriented fraction, defined as the fraction of scattered intensity from the oriented component to the total scattered intensity, was also calculated. The addition of POSS significantly increased the crystallization rate during shear compared with the rate for the neat polymer without POSS. We postulate that although POSS crystals have a limited role in shear-induced crystallization, molecularly dispersed POSS molecules behave as weak crosslinkers in polymer melts and increase the relaxation time of iPP chains after shear. Therefore, the overall orientation of the polymer chains is improved and a faster crystallization rate is obtained with the addition of POSS. Moreover, higher POSS concentrations resulted in faster crystallization rates during shear. The addition of POSS decreased the average long-period value of crystallized iPP after shear, which indicates that iPP nuclei are probably initiated in large numbers near molecularly dispersed POSS molecules.

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“…This appearance of the striations indicates the secondary flow pattern arising in the stirred solution. The striations may be generated by Taylor vortices in the solution as previously reported [8] and the crystals are deposited on the sites on the stirring bar and the vessel wall where the fluid moved from the stirring bar towards the vessel wall. This means that the striations from two Taylor vortices rotating in opposite directions settled at the same place on the stirring bar and the inner vessel wall.…”

Section: Resultsmentioning

confidence: 75%