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Macromolecules
Volumn 32, Issue 22, 1999, Pages 7537-7547
Shear-enhanced crystallization in isotactic polypropylene. 1. Correspondence between in situ rheo-optics and ex situ structure determination
Author keywords

[No Author keywords available]
Indexed keywords

BIREFRINGENCE; CRYSTALLIZATION; GROWTH (MATERIALS); MICROSCOPIC EXAMINATION; MORPHOLOGY; OPTICAL VARIABLES MEASUREMENT; PHASE TRANSITIONS; PLASTIC FLOW; SHEAR STRESS; STRUCTURE (COMPOSITION); TEMPERATURE;
EID: 0033517598     PISSN: 00249297     EISSN: None     Source Type: Journal    
DOI: 10.1021/ma990772j     Document Type: Article
Times cited : (359)
References (58)
  • 34
    • 0343945363 scopus 로고    scopus 로고
    • Shearing the polymer leads to a temperature increase due to viscous dissipation. However, the temperature increase is small since the shear rate is highest near the wall, which is maintained isothermal by the temperature control system and since the shear is imposed only for a brief duration. No variation in temperature during shear is recorded by a thermocouple positioned near the sample
    • Shearing the polymer leads to a temperature increase due to viscous dissipation. However, the temperature increase is small since the shear rate is highest near the wall, which is maintained isothermal by the temperature control system and since the shear is imposed only for a brief duration. No variation in temperature during shear is recorded by a thermocouple positioned near the sample.
  • 35
    • 0343944986 scopus 로고    scopus 로고
    • The temperature chosen, 220 °C, was higher than the Hoffman-Weeks equilibrium melting temperature for PP-300/6, which was determined to be 190 °C. Holding at this temperature for 5 min was deemed to be adequate to erase melt memory effects since higher temperatures (up to 240 °C) or longer holding times did not have any measurable difference on the crystallization kinetics
    • The temperature chosen, 220 °C, was higher than the Hoffman-Weeks equilibrium melting temperature for PP-300/6, which was determined to be 190 °C. Holding at this temperature for 5 min was deemed to be adequate to erase melt memory effects since higher temperatures (up to 240 °C) or longer holding times did not have any measurable difference on the crystallization kinetics.
  • 36
    • 0343944985 scopus 로고    scopus 로고
    • -6 s) for the present experiments
    • -6 s) for the present experiments.
  • 38
    • 0342638972 scopus 로고    scopus 로고
    • Nonlinear viscoelastic data obtained using a capillary rheometer indicate that PP-300/6 is shear thinning. Fitting this data to a power law model yields a value of about 0.38 for the power law exponent
    • Nonlinear viscoelastic data obtained using a capillary rheometer indicate that PP-300/6 is shear thinning. Fitting this data to a power law model yields a value of about 0.38 for the power law exponent.
  • 39
    • 0343944984 scopus 로고    scopus 로고
    • shear = 12 s) show that the spherulitic core has a lower melting temperature than the oriented skin. This suggests that the core might have crystallized at a lower temperature than the skin
    • shear = 12 s) show that the spherulitic core has a lower melting temperature than the oriented skin. This suggests that the core might have crystallized at a lower temperature than the skin.
  • 43
    • 0342638966 scopus 로고    scopus 로고
    • 17 (Figure 5). This is misleading. The steep increase in force and the subsequent decay between 10 and 20 s in Figure 6 of ref 14 is the viscoelastic response of the polymer melt to step strain. Neither the time scale nor the magnitude of the overshoot observed in the rheometer torque in Figure 5 of ref 17 change with the imposed strain rate, suggesting that the overshoot might be an artifact of the experimental setup (repositioning of the polymer, as suggested by the authors). In both these references, the increase in stress at later times results from an increase in modulus of the polymer due to crystallization with no evidence that these are oriented
    • 17 (Figure 5). This is misleading. The steep increase in force and the subsequent decay between 10 and 20 s in Figure 6 of ref 14 is the viscoelastic response of the polymer melt to step strain. Neither the time scale nor the magnitude of the overshoot observed in the rheometer torque in Figure 5 of ref 17 change with the imposed strain rate, suggesting that the overshoot might be an artifact of the experimental setup (repositioning of the polymer, as suggested by the authors). In both these references, the increase in stress at later times results from an increase in modulus of the polymer due to crystallization with no evidence that these are oriented.
  • 44
    • 0343509251 scopus 로고    scopus 로고
    • cryst = 141 °C for ∼6 s of shear are qualitatively similar to that in Figure 1a in the work of Andersen and Carr
    • cryst = 141 °C for ∼6 s of shear are qualitatively similar to that in Figure 1a in the work of Andersen and Carr (Andersen, P. G. and Carr, S.H. J. Mat. Sci. 1975, 10, 870-886.) which was obtained from an iPP fiber with well-developed α-iPP crystal structure having strong uniaxial orientation of parent crystallites (c axis along the fiber), bearing the associated crosshatched "daughter" crystallites.
    • Kumaraswamy, G.1    Verma, R.K.2    Wang, P.3    Kornfield, J.A.4    Yeh, F.5    Hsiao, B.S.6
  • 45
    • 0016510939 scopus 로고
    • which was obtained from an iPP fiber with well-developed α-iPP crystal structure having strong uniaxial orientation of parent crystallites (c axis along the fiber), bearing the associated crosshatched "daughter" crystallites
    • cryst = 141 °C for ∼6 s of shear are qualitatively similar to that in Figure 1a in the work of Andersen and Carr (Andersen, P. G. and Carr, S.H. J. Mat. Sci. 1975, 10, 870-886.) which was obtained from an iPP fiber with well-developed α-iPP crystal structure having strong uniaxial orientation of parent crystallites (c axis along the fiber), bearing the associated crosshatched "daughter" crystallites.
    • (1975) J. Mat. Sci. , vol.10 , pp. 870-886
    • Andersen, P.G.1    Carr, S.H.2
  • 50
    • 0342638963 scopus 로고    scopus 로고
    • Figure 4 in ref 24
    • Figure 4 in ref 24.
  • 54
    • 0343944980 scopus 로고    scopus 로고
    • z = 407 000 g/mol) was sheared at a temperature of 150 °C for shearing times of ∼20 s at wall shear stresses around 0.1 MPa. No upturn was seen in the birefringence observed during shear
    • z = 407 000 g/mol) was sheared at a temperature of 150 °C for shearing times of ∼20 s at wall shear stresses around 0.1 MPa. No upturn was seen in the birefringence observed during shear.
  • 55
    • 0001302524 scopus 로고    scopus 로고
    • Flow induced orientation and structure formation
    • Meijer, H. E. H., Ed.; VCH: NY
    • Keller, A.; Kolnaar, H. W. H. Flow Induced Orientation and Structure Formation. In Processing of Polymers; Meijer, H. E. H., Ed.; VCH: NY, 1997; Vol. 18.
    • (1997) Processing of Polymers , vol.18
    • Keller, A.1    Kolnaar, H.W.H.2

* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.