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Effects of melt viscosity reduction of polycarbonate by low molar mass liquid crystal |
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| รหัสดีโอไอ | |
| Title | Effects of melt viscosity reduction of polycarbonate by low molar mass liquid crystal |
| Creator | Noppawan Motong |
| Contributor | Supakanok Thongyai, Clarke, Nigel |
| Publisher | Chulalongkorn University |
| Publication Year | 2550 |
| Keyword | Polycarbonates, Polymer liquid crystals |
| Abstract | This work is devoted to the investigation of the effect of the reduction in melt viscosity of Polycarbonate by low molar mass liquid crystal chemical. The simple viscoelastic model, Maxwell model, was also chosen to explain the mechanism of the reduction and investigate the rheological parameters of the system. The phase behavior of low molar mass liquid crystal (LLC) and polycarbonate blends is firstly reported. The results of small angle light scattering (SALS) indicate that the LLC is miscible in the mixture for weight fractions of LLC less than 6%. For the study of the rheological properties, mixtures of two different liquid crystals with different molecular weight of polycarbonate were prepared inside the miscible regime of the blend. Both the complex and steady shear viscosities of the blends were found to be significantly decreased upon addition of small amounts of liquid crystal. At low shear rate, the steady state shear viscosity was similar to the pure polycarbonate, whilst, at higher shear rates, three further regimes of behavior, as has been described for liquid crystals and liquid crystal polymers, were found despite the low concentration of LLC; hence, the rheological properties of the blends can be significantly modified by small concentrations of LLC (as low as 1%). The decrease in melt viscosity of polycarbonate that we observe upon addition of LLC is not due to lubrication effects at the interfaces, as shown by reproducible oscillatory shear flow sweeps. The further study the effect of LLC content on the interdiffusion property, the diffusion coefficient was obtained using Nuclear Reaction Analysis (NRA) of bilayer films. An addition of only 1wt% liquid crystal to the polycarbonate significantly increased the diffusion coefficient, but at higher concentration the converse was found. To examine the bulk mechanical property, Dynamic mechanical analysis was used for observe the glass transition temperature of the blend. The decrease in Tg with liquid crystal content was found, in all cases the presence of single Tg indicates that blends are miscible. |
| URL Website | cuir.car.chula.ac.th |
