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Abstract  

Liquid crystalline polymer/polyamide 66 (LCP/PA66) and LCP/poly(butyl terephthalate) (LCP/PBT) blends were compounded using a Brabender Plasticorder equipped with a mixing chamber. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30 mol% of p-amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). The Flory-Huggins interaction parameters (χ12) of the LCP/ PA66 and LCP/PBT blends are estimated by melting point depression from DSC measurement. The results indicate that c12 values all are negative for LCP/PA66 and LCP/PBT blends, and when the LCP content in these blends is more than 10 mass%, the absolute value of χ12 decreases. Thereby, we can conclude that LCP/PA66 and LCP/PBT blends are fully miscible in the molten state, the molecular interaction between the LCP and PA66 is stronger than that between LCP and PBT. As the LCP content in LCP/PA66 and LCP/PBT blends is more than 10 mass%, the molecular interaction between LCP and matrix polymer decreases.

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Abstract  

Vectra® liquid crystalline polymers (LCP's) were introduced as commercial products in the mid-1980's. The first of these (Vectra A130) was a wholly aromatic thermotropic copolyester ofp-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Vectra A130 is a thermotropic LCP that can be melt spun into filaments that on heat treatment are characterized by high strength and high modulus. Vectra resin can also be extruded into films. In the fiber or film form this material is commercially known as Vectran®. Heat treatment enhances the tensile strength of Vectran fiber variants. Because of this, the elucidation of the physical transformations taking place in the internal structure of the material during heating has always been an important subject. Several thermal techniques are used to indicate clearly that what is observed as a “glass transition” is unlike the conventional glass transition in typical semicrystalline polymers. There is also an indication of the presence of multiple states of mesophase aggregation that collapse into a single state when taken to high enough temperatures.

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Abstract  

The first experimental evidence of the existence of the rigid amorphous phase was reported by Menczel and Wunderlich [1]: when trying to clarify the glass transition characteristics of the first main chain liquid crystalline polymers [poly(ethylene terephthalate-co-p-oxybenzoate) with 60 and 80 mol% ethylene terephthalate units] [2], the absence of the hysteresis peak at the lower temperature glass transition became evident when the sample of this copolymer was heated much faster than it had previously been cooled. Since this glass transition involved the ethylene terephthalate-rich segments of the copolymer, we searched for the source of the absence of the hysteresis peak in PET. There, the gradual disappearance of the hysteresis peak with increasing crystallinity was confirmed [1]. At the same time it was noted that the higher crystallinity samples showed a much smaller ΔC p than could be expected on the basis of the crystallinity calculated from the heat of fusion (provided that the crystallinity concept works). Later it was confirmed that the hysteresis peak is also missing at the glass transition of nematic glasses of polymers. When checking other semicrystalline polymers, the sum of the amorphous content calculated from the ΔC p at the glass transition, and the crystallinity calculated from the heat of fusion was far from 100% for a number of semicrystalline polymers. For most of these polymers, the sum of the amorphous content and the crystalline fraction was 0.7, meaning that ca. 30% rigid amorphous fraction was present in these samples after a cooling at 0.5 K min−1 rate. Thus, the presence of the rigid amorphous phase was confirmed in five semicrystalline polymers: PET, Nylon 6, PVF, Nylon 66 and polycaprolactone [1]. Somewhat later poly(butylene terephthalate) and bisphenol-A polycarbonate [3] were added to this list. In this paper we also report details on a special effect of the rigid amorphous phase (RAP) on the mobile amorphous phase (MAP): the hysteresis peak at the glass transition of the MAF disappears under the influence of the RAP, and this raises the question whether the glass transition of the MAF becomes time independent in semicrystalline polymers.

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. 19. Sahoo NG , Cheng HKF , Pan Y , Li L , Chan SH , Zhao J . Strengthening of liquid crystalline polymer by functionalized carbon nanotubes through interfacial interaction and homogeneous

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selecting the matrix resin, the reinforcing material and their ratio, during which the interphasial interactions play the essential role. A new and exciting field of research represent the composites based on liquid crystalline polymers or reinforcements

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-010-0837-2 . 17. Pisitsak , P , Magaraphan , R 2009 Influences of a liquid crystalline polymer, VECTRA A950, on crystallization kinetics and thermal stability of poly(trimethylene terephthalate) . J Therm Anal Calorim. 95 : 661 – 666

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, W , Wendorff , JH , Hopmeier , M , Feldmann , J . Polarized photoluminescence of liquid crystalline polymers with isolated arylenevinylene segments in the main chain . Adv Mater . 1995 ; 7 : 923 – 925 . 10.1002/adma.19950071112

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, Wang , XJ . Liquid crystalline polymer . Beijing : Science Publishers ; 1999 . 27. Lee , JY , Jang , J . The effect of mesogenic length on the curing behavior and properties of

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electrical and luminescence behaviors of polyacetylenes can be greatly tuned by changing their molecular structures. Generally, the mono- and disubstituted type exert great on the properties of liquid crystalline polymers, such as polynorbornene derivatives

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2011 Mechanical and electrical property enhancement in exfoliated graphene nanoplatelet/liquid crystalline polymer nanocomposites . Compos A Appl Sci Manuf 42 4 371 – 375 10.1016/j.compositesa.2010.12.006 . 6

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