Abstract
The rheological behavior of two flexible thermoplastics, Nylon-6 (Ny) and bisphenol-A polysulfone (PSu), and two wholly aromatic liquid crystalline polymers, Vectra-A900 (VA) and Vectra-B950 (VB), as well as that of Ny/VB and PSu/VA blends with 10% LCP, has been investigated by the use of capillary viscometers equipped with cylindrical dies having different length-to-diameter ratios. The elongational viscosity of all materials was calculated, from the results of isothermal measurements carried out at 290°C, by means of the Cogswell's analysis, based on the estimation of the pressure drop due to the converging flow at the die inlet. The behavior in elongational flow was compared with the rheological behavior in shear flow conditions. It was found that the elongational viscosities of VA and VB are very large and account for a fairly marked pressure drop at the die entrance, due to the orientation of the LCP domains taking place in the converging flow zone. For these materials, the ratio of the elongational viscosity to the Newtonian shear viscosity is up to two orders of magnitude higher than the value expected on the basis of the Trouton rule. For the flexible resins, the Trouton ratio is 3 and ca. 3–10, are common values for high molar mass linear polymers. The addition of 10% LCP into the flexible resins strongly increases their elongational viscosity and makes the blends resemble neat LCPs in their extensional flow behavior. In shear flow, on the contrary, the addition of LCP was shown to induce a marked reduction of the melt viscosity, even when, as for the Ny/VB blend, the LCP is more viscous than the matrix.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bankar VG, Spruieli JE, White JL (1977) Melt spinning dynamics and theological properties of nylon 6. J Appl Polym Sci 21:2135–2155
Beery B, Konig S, Siegmann A, Narkis M (1992) Shear and elongational viscosities of a thermotropic liquid crystalline polymer and its blend with polycarbonate. Polym Eng Sci 32:14–19
Calundann GW, Jaffe M (1982) Anisotropic polymers, their synthesis and properties. Proc. Robert A. Welch Conference on Chemical Research. XXVI Synthetic Polymers 247–291
Cogswell FN (1972) Converging flow of polymer melts in extrusion dies. Polym Eng Sci 12:64–73
Chung TS (1986) The recent developments of thermotropic liquid crystalline polymers. Polym Eng Sci 26:901–919
Crowson RJ, Folkes MJ, Bright PF (1980) Rheology of short glass fiber-reinforced thermoplastics and its application to injection molding. I Fiber motion and viscosity measurement. Polym Eng Sci 20:925–933
Dutta D, Fruitwala H, Kohli A, Weiss RA (1990) Polymer blends containing liquid crystals: A review. Polym Eng Sci 30:1005–1026, and references therein
Gibson AG, Williamson GA (1985) Shear and extensional flow of reinforced plastics in injection molding. I Effect of die angle and bore diameter on entry pressure with bulk molding compound. Polym Eng Sci 25:980–985
Gotsis AD, Langelaan HC (1994) Origins of nonlinear pressure profiles in the flow of nematic melts in capillaries and slits. J Rheol 38:1369–1383
Izu P, Munoz ME, Pena JJ, Santamaria A (1993) Capillary and slit-die flow of two liquid-crystalline polymers. The effect of pressure on viscosity. J Polym Sci Polym Phys 31:347–356
Izu P, Munoz ME, Pena JJ, Santamaria A (1996) Competition between textural transitions and pressure effects on the viscosity of thermotropic liquid-crystal polymers. Polym Eng Sci 36:721–730
La Mantia FP, Valenza A (1989) Shear and non-isothermal elongational characterization of a liquid crystalline polymer. Polym Eng Sci 29:625–631
La Mantia FP, Valenza A, Paci M, Magagnini PL (1989) Shear viscosity of PBT/LCP blends. Rheol Acta 28:417–422
La Mantia FP, Valenza A, Paci M, Magagnini PL (1990) Rheology-Morphology relationships in Ny6/LCP blends. Polym Eng Sci 30:7–12
La Mantia FP, Valenza A (1992) Shear flow characterization of blends containing liquid crystal polymers. Makromol Chem Makromol Symp 56:151–159
La Mantia FP, Valenza A, Magagnini PL (1992) Liquid crystal polymer based blends: “Universal grade polmyers?”. J Appl Polym Sci 44:1257–1265
La Mantia FP (ed) (1993) Thermotropic liquid crystal polymer blends, Technomic, Lancaster and references therein
La Mantia FP, Valenza A (1993) A phenomenological approach to predict the presence of minima in shear flow curves of blends with liquid crystal polymers. Polym Networks & Blends 3:125–129
La Mantia FP, Valenza A, Scargiali F (1994) Non-isothermal elongational behavior of blends with liquid crystalline polymers. Polym Eng Sci 34:799–803
La Mantia FP, Roggero A, Pedretti U, Magagnini PL (1996) Fibers of blends with liquid crystalline polymers: spinnability and mechanical properties. In: Isayev AI, Kyu T, Cheng SZD (eds) Liquid crystalline polmyer systems technological advances. ACS Symposium Series 632, Washington DC pp 110–117
Laun HM (1979) Das viskoelastische Verbalten von polyamid-6-Schmelzen. Rheol Acta 18:478–491
Laun HM, Schuch H (1989) Transient elongational viscosities and drawability of polymer melts. J Rheol 33:119–175
Lefeuvre P, De'Nève T, Navard P (1994) Bagley plot of Vectra B950 thermotropic polymer. J Rheol 38:169–175
Marrucci G (1993) Rheology of thermotropic liquid crystalline polymer thermotropic. In: La Mantia FP (ed) Liquid crystal polymer blends, Technomic. Lancaster pp 43–58
Valenza A, Spadaro G, La Mantia FP, Acierno D (1986) A comprehensive experimental study of the rheological behaviour of HDPE. III Extensional flow results. Rheol Acta 25:50–54
Valenza A, La Mantia FP, Acierno D (1986) The theological behaviour of HDPE/ LDPE blends. V Isothermal elongational at constant stretching rate. J Rheol 30:1085–1092
Turek DE, Simon GP, Tin C (1992) The effect of the die aspect ratio on the theological properties of a thermotropic copolyester. J Rheol 36:1057–1078
Turek BE, Simon GP, Smejkal F, Grosso M, Incarnato L, Acierno D (1993) Transient isothermal elongational flow of thermotropic liquid crystalline polymers. Polymer 34:204–206
Wissbrun KF (1993) A two-fluid model for inconsistency of observations in capillary rheometry of thermotropic copolyesters. J Rheol 37:777–797
Yongcheng YE, La Mantia FP, Valenza A, Città V, Pedretti U, Roggero A (1991) Characterization of blends of polypropylene with a semirigid liquid-crystal copolyester. Europ Polym J 27:723–727
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
La Mantia, F.P., Paci, M. & Magagnini, P.L. Isothermal elongational behavior of liquid-crystalline polymers and LCPs based blends. Rheola Acta 36, 152–159 (1997). https://doi.org/10.1007/BF00366821
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00366821