Evolution of morphological and rheological properties along the extruder length for blends of a commercial liquid crystalline polymer and polypropylene

Filipe, S.; Cidade, M. T.; Wilhelm, Manfred; Maia, João M.

doi:10.1016/j.polymer.2003.12.080

Cited by 43 publications

(31 citation statements)

References 32 publications

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“…It should be mentioned that the temperature used for the later measurements (170°C) was the highest temperature for which reproducible results were obtained. However, considering previous rheo-optical measurements 31 we can assure that, at this temperature, the liquid-crystalline polymer structures inside the matrix are completely molten, even though for the pure LCP a biphasic structure would be most probably present, since its transition temperature is over 180°C. This technique has already been used to characterize the nonlinear character of LCP/TP blends and other materials.…”

mentioning

confidence: 79%

“…Recently, the present authors 30,31 have resorted to the use of large amplitude oscillatory shear (LAOS) and Fourier transform rheology (FTR) to show that these measurements are more sensitive than both steady-state and linear oscillatory rheology to structure variations in extruded noncompatibilized LCP/TP blends differing in their LCP contents. For example, Filipe et al, 30 reported that the transient shear measurements performed on blends with different LCP contents show an overshoot for the transient stress, the magnitude of which increases with increasing LCP content.…”

Section: Introductionmentioning

confidence: 99%

“…This technique has already been used to characterize the nonlinear character of LCP/TP blends and other materials. 30,31,[33][34][35] The transient measurements were performed applying a shear rate of 1 s Ϫ1 during 600 s. A preshear of 0.3 s Ϫ1 was applied to these samples during 600 s, to guarantee the same starting conditions for all of the samples.…”

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confidence: 99%

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Influence of type of compatibilizer on the rheological and mechanical behavior of LCP/TP blends under different stationary and nonstationary shear conditions

Filipe

Maia

Duarte

et al. 2005

J of Applied Polymer Sci

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ABSTRACT:The addition of small amounts of liquidcrystalline polymers to thermoplastics leads to the formation of in situ-reinforced materials, with improved processability and mechanical properties. Nevertheless, the lack of adhesion between the thermoplastic and the liquid-crystalline polymer often occurs, thus requiring the use of compatibilizers. In this case, the results of several previous works show that there is an improvement of strength, usually accompanied by a decrease of toughness and, thus, the interest of LCP/TP blends for industrial applications will certainly increase if both strength and toughness are obtained. Additionally, the emphasis of previous studies has been on the evaluation of the properties of the blend under stationary conditions and not under non-stationary ones, which are, in fact, those most relevant to processing sequences. Thus, the present work focuses on the influence of type of compatibilizer on the mechanical and rheological properties of polypropylene/LCP blends under nonstationary conditions. In terms of mechanical properties, the traditional increase of tensile strength was obtained for all compatibilizers, which was essentially due to the formation, during processing, of thinner and longer fibrils of LCP dispersed in the matrix than those observed for the noncompatibilized blends. Additionally, an improvement of the impact strength and flexural modulus was also observed for the blend in which a compatibilizer with an elastomeric nature was used. Rheologically, the experiments most sensitive to the structure were those performed in transient shear, with an increase of the transient stress (in the form of an overshoot) of different magnitudes being observed for the different compatibilizers.

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confidence: 79%

Section: Introductionmentioning

confidence: 99%

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Influence of type of compatibilizer on the rheological and mechanical behavior of LCP/TP blends under different stationary and nonstationary shear conditions

Filipe

Maia

Duarte

et al. 2005

J of Applied Polymer Sci

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] One of the advantages of LCP/TP in situ composites arise from the high level of macroscopic molecular orientation developed in these blends (which leads to the formation of fibrillar structures oriented along the flow direction, with consequent mechanical performance enhancement). Another advantage is related with the decrease of viscosity, when compared with other reinforced thermoplastics, like, for instance, those with glass fibers.…”

Section: Introductionmentioning

confidence: 99%

“…One problem concerning this method is that, to avoid phase separation, homopolymers have to be short, crystallizable, and with an appropriate polydispersity, which turned impossible to use this method for our blends, since the synthesis of compatibilizers was just a continuation of a work that we had already started 20,26,27 and our matrix, as will be described in the Material section, was a isotatic polypropylene with a weight-average molecular weight (M w ) of 1200,000 g/mol.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of compatibilizers and characterization of the compatibilized and noncompatibilized blends of PP/Rodrun LC3000

Cidade

Filipe

Duarte

et al. 2007

J of Applied Polymer Sci

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The addition of a liquid crystalline polymer (LCP) to a matrix of a flexible thermoplastic (TP) has been used in the last two decades as an in situ reinforcement of the matrix. Owing to the immiscibility of the two phases and the high degree of orientation typical of LCPs, the dispersed phase is, after processing, essentially constituted by fibrillar structures, which are responsible for the reinforcement of the matrix and the decrease of viscosity with respect to the matrix. The low degree of adhesion typical of LCP/TP blends often requires the use of compatibilizers, which will act reducing the interfacial tension between the two components. In this work, we present the synthesis of three different compatibilizers, as well as the mechanical characterization of the corresponding compatibilized blends. Some scanning electron microphotographs will be also presented to better explain the mechanical results. The mechanical properties of these blends were compared with the noncompatibilized blend, as well as with the ones presented by blends obtained with two commercial compatibilizers, leading to the conclusion that, considering our compatibilizer C, the one that leads to the higher enhancement of the Young's modulus, when compared with the noncompatibilized blend, we obtain a Young's modulus 27% higher than the one presented by the noncompatibilized blend. Comparing this result with those presented by the blends compatibilized with the two commercial compatibilizers, D and E, we conclude that this enhancement is higher than those presented by those blends (increase in Young's modulus of 16% for both compatibilizers).

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A New Extensional Mixing Element for Improved Dispersive Mixing in Twin‐Screw Extrusion, Part 2: Experimental Validation for Immiscible Polymer Blends

2016

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ABSTRACT:In Part 1 of this work, we presented a novel static extensional mixing element (EME) for twin-screw extrusion operations and validated the design in terms of the type of flow experienced by the melt upon dispersive mixing. In Part 2, we experimentally demonstrate the ability of the EME to yield improved dispersive mixing when compared with standard kneading-block-induced mixing for immiscible polypropylene/polystyrene blends of varying viscosity ratios between 0.3 and 10. The extensional flow characteristics of the EME improved the dispersion of polystyrene in the blends over all viscosity ratios, with improvements of 30% and above as measured by the cumulative area ratio measurements of polystyrene phases smaller than 1 μm 2 . The improvement in dispersive mixing seen from the EME for high viscosity ratio blends opens up applications in other areas, such as dispersion of nanoparticles or in reactive extrusion operations. C 2016 Wiley Periodicals, Inc. Adv Polym Technol 2016, 0, 21653; View this article online at wileyonlinelibrary.com.

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Evolution of morphological and rheological properties along the extruder length for blends of a commercial liquid crystalline polymer and polypropylene

Cited by 43 publications

References 32 publications

Influence of type of compatibilizer on the rheological and mechanical behavior of LCP/TP blends under different stationary and nonstationary shear conditions

Influence of type of compatibilizer on the rheological and mechanical behavior of LCP/TP blends under different stationary and nonstationary shear conditions

Synthesis of compatibilizers and characterization of the compatibilized and noncompatibilized blends of PP/Rodrun LC3000

A New Extensional Mixing Element for Improved Dispersive Mixing in Twin‐Screw Extrusion, Part 2: Experimental Validation for Immiscible Polymer Blends

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