Effects of carbon nanotubes (CNT) on the dynamic mechanical property, thermal property, and crystal structure of poly(L-lactic acid) (PLLA) were investigated. Dynamic mechanical analysis (DMA) found that CNT via grafting modification with PLLA (CNT-g-PLLA) could result in effective reinforcing effects. Tan d of DMA found that CNT-g-PLLA was compatible with the PLLA matrix, giving a single T g of the composite with a higher CNT-g-PLLA loading giving a higher T g of the composite. Wide angle X-ray diffraction (WAXD) data demonstrated that CNT could assist the disorder-to-order (a 0 -to-a) transition in PLLA crystals but did not lead to a more compact chain packing of the crystal lattice in PLLA composites than in pure PLLA. The equilibrium melting temperature (T 0 m ) obtained from Hoffman-Weeks plots were found to increase with increasing CNT-g-PLLA content. Small angle X-ray scattering data revealed that thicknesses of crystal layer and amorphous layer of PLLA both decreased with increasing CNT contents. V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: [145][146][147][148][149][150][151][152] 2010
A facile and economic modification of polyvinylidene fluoride (PVDF) with an orientation of diamine is presented herein. The physical characterizations of native and diamine-grafted PVDF membranes are analyzed by three different techniques: the ninhydrin test, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The diamine-grafted PVDF is activated by glutaraldehyde for enzyme immobilization. The response surface methodology (RSM) is used to search the optimal immobilization conditions and to understand the significance of the factors affecting the responses of immobilized lipase. The optimal conditions for lipase immobilization are: a reaction time of 90 min, temperature of 35 degrees C, pH of 6, and an enzyme concentration of 7 mg/mL. An experiment performed under the optimum conditions obtains lipase activity of 60 U per g of membrane. A good agreement between the calculated and experimental values is thereby achieved
The ability of immobilized lipase Candida antarctica (Novozyme 435) to catalyze the direct esterification of hydroxyphenylpropionic acid and octanol in a solvent-free system was investigated in this study. Response surface methodology (RSM) and five-level-four-factor central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time, temperature, enzyme amount, and pH memory, on percentage molar conversion of phenolic acid esters. Reaction time, temperature, and enzyme amount were the most important variables. On the basis of canonical analysis and ridge max analysis, the optimum synthesis conditions with 95.9% molar conversion were reaction time of 58.2 h, temperature of 52.9 degrees C, enzyme amount of 37.8% (w/w), and pH memory of pH 7.
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