X-ray microscopy of novel thermoplastic/liquid crystalline polymer blends by mechanical alloying (original) (raw)
Poly(caprolacton)/liquid crystalline polymer blends: Phase behaviour and mechanical properties
Journal of Materials Science, 1994
The blend behaviour of a thermoplast (polycaprolacton) and a liquid crystalline polyester was investigated. The blending was performed via a common solution and rapid precipitation, The blends exhibited a two-phase structure with one phase being the pure thermoplast and the second a mixture of the thermoplast with the liquid crystalline polymer (LCP). The mixed phase can be interpreted as a lyotropic LCP phase with the thermoplast acting as the solvent.
Crystallization kinetics of compatibilized blends of a liquid crystalline polymer with polypropylene
Journal of Applied Polymer Science, 1997
Blends of a maleic anhydride-grafted polypropylene (m-PP) and a liquid crystalline polymer (LCP) based on a copolyester of hydroxynapthoic acid and hydroxybenzoic acid were fabricated. The morphology and isothermal and nonisothermal crystallization kinetics behavior of the m-PP copolymer and m-PP/LCP blends were investigated using polarizing optical microscopy, depolarized light intensity, and differential scanning calorimetry. A polarizing optical micrograph revealed that the m-PP is very effective to promote a finer dispersion of the LCP phase in the PP matrix. Consequently, the LCP domains or fibrils acted as potential sites for the spherulite nucleation. The isothermal kinetics measurements also indicated that the rate of crystallization is enhanced in the maleated PP/LCP blends which exhibit transcrystallinity. In general, the nonisothermal kinetics results were in good agreement with those obtained from the isothermal kinetics measurements.
1992
Fibers (strands) with various draw ratios were spun from the liquid crystalline state of a pure aromatic liquid crystalline copoly(ester amide) and the melts of its blend with polycarbonate. Scanning electron microscopy (SEMI, wide angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) were employed to investigate the structure and properties of the resulting fibers. Mechanical properties of the fibers were also evaluated. I t was found that both the crystallite size and heat of fusion of the liquid crystalline polymer (LCP) increase steadily with draw ratio. However, the crystal-nematic transition temperature of the LCP is virtually unaffected by drawing. Moreover, heat of fusion of LCP is much smaller than that of isotropic condensation polymers despite the presence of very sharp dmraction peaks in WAXS measurements. These results are ascribed to the (semi)rigid rod nature of the LCP chains and the persistence of an ordered structure in the LCP melt, i.e., entropy effect. It was further observed that tensile modulus and tensile strength along fiber axis rise with draw ratio for the composite fibers. The elastic modulus of the composite fibers were found to be as high as 19 GPa and tensile strength reached 146 MPa with draw ratios below 40 and an LCP content of 30 wt%. Compared with the thermoplastic matrix, the elastic modulus and tensile strength of the in-situ composite have increased by 7.3 times and 1.4 times, respectively, with the addition of only 30 wt% LCP. This improvement in mechanical properties is attributed to fibrillation of the LCP phase in the blend and the increasing orientation of the LCP chains along the fiber axis during drawing.
Polymer blends containing liquid crystals: a review
Polymer Engineering & …, 1990
This paper reviews the literature of polymer blends containing low and high molar mass liquid crystals. Low molar mass liquid crystals have been used as plasticizers for thermoplastic polymers and in applications such a s electro-optics, optical recording media, and membranes. High molar mass liquid crystalline polymers have been primarily used in polymer blends as processing aids and as an incipient reinforcing phase for "self-reinforced" materials. This review discusses the phase behavior, rheology, and mechanical properties of these blends.
Polymers for Advanced Technologies, 2009
In this study, the potential of recycled poly(ethylene terepthalate) (rPET) as a well-defined reinforcing material for the in situ microfibrillar-reinforced composite (iMFC) was investigated in comparison with that of liquid crystalline polymer (LCP). Each dispersed phase (LCP or rPET) was melt blended with high density polyethylene (PE) by using extrusion process. The rheological behavior, morphology, and the thermal stability of LCP/PE and rPET/PE blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of LCP or rPET into PE significantly improved the processability. A potential of rPET as a processing lubricant by bringing down the melt viscosity of the blend system was as good as LCP. The elongated LCP domains were clearly observed in as-extruded strand. Although the viscosity ratio of the rPET/PE system was lower than that of the LCP/PE blend system, most rPET domains appeared as small droplets. An addition of LCP and rPET into the PE matrix improved the thermal resistance significantly in air but not in nitrogen. The obtained results suggested the high potential of rPET as a processing aid and good thermally resistant material similar to LCP.
2001
The phase behavior, rheology, and morphology of binary blends of semiflexible main-chain thermotropic liquid-crystalline polymers (TLCPs) were investigated. Specifically, binary blends consisting of poly[(phenylsulfonyl)-p-phenylene alkylene-bis(4-oxybenzoate)]s (PSHQn) having five methylene groups (PSHQ5) and 11 methylene groups (PSHQ11) were prepared by solvent casting. It was found from differential scanning calorimetry (DSC) that PSHQ5, PSHQ11, and their blends are glassy thermotropic polymers, exhibiting only glass-to-nematic and nematic-to-isotropic (N-I) transitions. Approximate phase diagrams were constructed for PSHQ5/PSHQ11 blends based on DSC data. Using a cone-and-plate rheometer, transient shear flow experiments were conducted for the PSHQ5/PSHQ11 blends (i) at 160°C in the biphasic region where PSHQ11 forms an isotropic phase and PSHQ5 forms a nematic phase and (ii) at 130°C in the nematic region where both PSHQ5 and PSHQ11 formed the nematic phase. It was found for such PSHQ5/PSHQ11 blends that the steady-state shear viscosity at 130°C (in the nematic region) is lower than that at 160°C (in the biphasic region). However, the first normal stress difference at 130°C exhibits a very large overshoot followed by an oscillatory decay until reaching a steady state, while it is virtually zero at 160°C. The time evolution of morphology for the PSHQ5/PSHQ11 blends, upon shear startup and also upon cessation of shear flow, was investigated using a specially designed optical microrheometer equipped with a polarizing optical microscope. Contrasting observations are reported for the case of nematic PSHQ5 in isotropic PSHQ11 when compared to the nematic PSHQ5/ nematic PSHQ11 blend. Shearing of a nematic/nematic blend induces a much larger birefringence change than does shearing a nematic/isotropic blend, and a shear-induced isotropic-to-nematic transition is observed from a mixture of isotropic phases containing two TLCPs.
The technology to produce compatibilized blends of liquid crystalline polymer and highly amorphous cyclic olefin copolymers through two novel approaches were studied. The first approach was to use silane-functionalized halloysite nanotube as nonspecific compatibilizer and the second method was reactive compatibilization. The study of blends and their resulting microstructure; their thermal, mechanical, and viscoelastic properties were investigated. The kinetic study of blends compatibilized through both routes was performed.
Mechanical properties of blends of liquid crystalline copolyesters with polyprophylene
Mechanics of Composite Materials, 1995
As new composites produced in the form of blends of thermotropic liquid crystals (LCP) with less expensive engineering thermoplastics became very popular recently, increased interest about the production and investigations of these materials is noted during the last few years [1-5]. First, the addition of the LCP permits us to essentially decrease the viscosity of certain engineering thermoplastics and therefore to facilitate the processing considerably. Second, during injection molding the drops of the LCP, as a dispersed phase, are lengthening out themselves into aniso-diametrical, thread-like forms, finally reinforcing the isotropic thermoplastic matrix. It allows us to obtain reinforced composites with improved physicomechanical properties directly during processing. To optimize the selection and the composition of the components as well as the processing conditions, investigations of the melt rheological properties and the mechanical and physical properties of the products are necessary. The main purpose of our work was to determine the mechanical properties of the blend of the LCP with polypropylene and the anisotropy of mechanical properties produced as a result of processing by injection molding. EXPERIMENTAL Material. The isotactic polypropylene (PP), VB 65 11B, produced by NESTE, Finland, and the liquid crystalline copolyester (LCP) of 40% polyethylene terephthalate with 60% p-hydroxybenzoic acid (40 PET/60 PHB), LC-3000, produced by Unitika Ltd., Kyoto, were used in our investigations. Binary blends with LCP content of 0%, 5%, 10%, 15%, and 20% were prepared. Sample Preparation. To exclude the possible degradation of macromolecule chains by hydration, the 40 PET/60 PHB copolyester was dried for 8 h at 130~ the blending was done using a single screw extruder Goettfert ~ = 20 mm (the length/diameter ratio L/D = 20) with a 3 mm cylindrical die. The extruded rods were granulated using a palletizing trait. The temperatures of the heating zones of the barrel were 210~ 200~ and 230~ The screw rotation speed was 55 rpm. Plates with a length of 160 mm, width of 100 ram, and thickness of 2 mm were prepared by injection molding. This was conducted at a rather high temperature to assure the processing of the blend in the liquid crystalline phase and to form the LC-rich regions in the thermoplastic matrix. The machine used was the injection press BILLION with a clamping force of 90 tons. The following injection parameters were applied: temperature of the barrel 170~176176 and 245~ the mold temperature was 20~ filling pressure 530 bars, packing pressure 270 bars, packing time 5 sec, and the cooling time in the mould was 15 sec. To determine the anisotropy of the mechanical properties by tensile test, samples in the form of a dog-bone were cut in the flow direction (MD) (direction of injection) and in the transversal direction (TD) (perpendicular to the flow direction). The dimensions of MD specimens were: thickness 2 turn, length 150 ram, the length of the narrow section 60 ram, and the distance between the clamps 90 mm. For TD specimens, the corresponding dimensions were: 100 ram, 40 mm, and 60 mm.