Synthesis And Characterization On Semi-Aromatic Polyamides Containing Benzoxazole Units

The synthesis and performances of semi-aromatic polyamides containing benzoxazolee units were studied in this thesis.In order to obtain a novel polyamide with excellent heat-resistant properties which could be anticipated as a thermal modifier for aliphatic polyamides, three new semi-aromatic polyamides(BO6, BO8, BO10) were synthesized based on 5-amino-2-(p-aminophenyl)benzoxazole(ABO) and aliphatic acids by means of Yamazaki phosphorylation method. The products were characterized by means of FTIR,1H-NMR, and the heat resistance of the polymer was studied by means of DSC and TG. It was showed that the heat resistance of the new semi-aromatic polyamides was much higher than that of the common aliphatic polyamides, in addition, the products showed a good balance of solubility, crystallization and heat resistances in the ABO-based semi-aromatic polyamides. Therefore, they may be considered as promising thermal modifier of aliphatic polyamides.The effect of reaction temperature on inherent viscosity of the polymers were studied, It was showed that the polymers had the highest viscosity at around 90℃, 130℃and 130℃for BO6, BO8 and BO10 respectively with the inherent viscosity of 1.62dL/g, 1.04dL/g and 0.88dL/g accordingly. The products showed excellent solvent resistance, the presence of the p-phenylene benzoxazolee component in BO6, BO8 and BO10 caused the insolubility in a variety of organic solvents including amide-type solvents (DMF, DMAC), DMSO and pyridine. All of the the polymers were only soluble in concentrated H2SO4, CF3COOH and CH3HSO3. Information from 1H-NMR indicated that the products had a medium average molecular weight. The peaks of XRD curves were separated out by Gauss-Lorentzian fitness and the crystallization percentages of the polymers were figured out, which showed a medium crystallization of these semi-aromatic polyamides. The heat resistance of the polymers was studied by DSC and TG-DTG. The results showed that the heat resistances of the new semi-aromatic polyamides were much higher than that of the common aliphatic polyamides, in addition, the products showed good crystallization properties.The activation energies of heat decomposition of BO6 calculated by Kissinger and Flynn-Wall-Ozawa method were 220.69 kJ/mol and 200.53 kJ/mol, respectively. The kinetic parameters of heat-decomposition reaction of BO6 were determined by differential calculus and the value of frequency factor and reaction order were 2.29405s-1 and 2.98126 individually. According to the value of activation energy obtained, Coats-Redfern method was used to discuss the mechanics of heat decomposition of BO6. The mechanics equation was g(X)= X and the heat decomposition was controlled by phase interface(one dimension).