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Kinetic Study on the Process for Aliphatic-aromatic Copolyester Synthesis

Author: HuLiXia
Tutor: LiBoGeng；WuLinBo
School: Zhejiang University
Course: Chemical Engineering
Keywords: PBST copolyesters Esterification reaction Polycondensation of Dynamics Model Biodegradable
CLC: O631.5
Type: Master's thesis
Year: 2010
Downloads: 69
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Abstract

Polybutylene succinate - butylene terephthalate copolyester (PBST) Recent studies have more of a biodegradable copolyester, which combines an aliphatic polyester and aromatic polyester advantages of having a good biodegradability, thermal and mechanical properties; while its raw materials, succinic acid (SA), butanediol (BDO) can be obtained from biomass resources, can reduce reliance on oil, has a good prospects for development. PBST research focused on the synthesis, structure, properties, degradation, see the end of the whole process of reaction kinetics and modeling studies reported, PBST not yet realize the industrialization production. To promote on the the PBST synthesis process in complex esterification and copolycondensation understanding of the reaction mechanism, optimizing the reactor and its operation process and the copolyester chain structure prediction and regulation, first proposed two kettle parallel esterification and two kettle series co-condensation synthesis process, and its esterification and co-condensation reaction kinetics experiments and model studies, the final synthesis of the different components of the structure PBST examine its composition, structure, thermal and mechanical properties. First, tetrabutyl titanate (TBT) catalyzed SA / of BDO and TPA / of BDO esterification reaction kinetic experiments. Found that during the esterification reaction in the volume of the reaction system and the degree of reaction of the COOH groups changes linearly (linear increase of the TPA system, the SA system linear decrease), and independent of temperature; esterification reaction is transformed to produce 80% ~ 85% BDO water, but only 3% to 6% generated THF, showed relatively few side reactions in the esterification stage. Functional group proposed fitting containing the esterification reaction (κ1 = 2κ2), the polycondensation reaction (κ3) and generate the THF side reactions (κ4, κ5) esterification kinetics model and experimental data obtained in the model kinetic constants and activation energy. SA / BDO system esterification reaction activation energy E1 (59.5kJ-mol-1) smaller than the TPA / BDO E1 (82.2 kJ? Mol-1). SA The reaction temperature is relatively low. SA / BDO system, E1, E3 (59.5,89.6 kJ? Mol-1) is slightly higher than the literature 7. Reported values ??(47.4,85.7 kJ? Mol-1). According to the model, were simulated for different temperatures, different monomer ratio under different system conditions. Found elevated temperature, increasing the alkyd than are conducive to improve the rate of the esterification reaction, but will also generate more THF, but the former is beneficial to increase the degree of polymerization of the oligomer, while the latter Queshi oligomer degree of polymerization of decreased ; heterogeneous system TPA / BDO, due to the low reaction rate, and less effective COOH content in the reaction system, and requires higher temperatures and higher alkyd ratio in order to achieve a higher rate of the esterification reaction. Further TGA method basically TBT common and rare earth catalyst catalytic condensation and co-condensation reaction kinetics of experimental study, found that the prepolymer TGA weight loss curves in theory react completely weightless above the line, and the polymer molecular weight increased linearly. Functional groups are condensation and co-condensation kinetics model. Both first PBT and PBS polycondensation kinetic model with experimental polycondensation kinetic constants by co-condensation model and experimental data obtained the kinetic constants copolycondensation, proposed a complete co-polycondensation dynamics of model. Model are in good agreement with experimental data. The PBT. PBS polycondensation PBST copolycondensation reaction rate constant were kT = 3.15E5 and? E-62200/RT, kS = 80.5E4,? E-62200/RT kST = 2.05E4? E-48770/RT. Research polycondensation reaction rate constant activation energy were lower than reported in the literature without rare earth catalyst under the conditions of the activation energy (the PBS 85.7kJ/mol DNBikiaris, 2008; the the PBT 85.4kJ/mol, PJDarda 2005). Finally, based on experimental and model optimization of reaction conditions, the synthesis of different TPA / SA ratio PBST copolyester, its composition, structure, thermal and mechanical properties. Copolyester composition and the ratio of raw materials is basically the same, when the SA content in the range of 50% to 80%, the degree of randomness are less than 1, the the BT average sequence length is smaller than 3, which is biodegradable; when SA The content is within the range of from 70% to 80%, very close to completely random copolymer; With the increasing the content of aromatic components, melting point and the melting enthalpy is decreased and then increased, is detected when the SA content of 70% less than its melting point, its glass transition temperature of -22.02 ° C. The stretching results show the improvement of PBT unit content is conducive to improve the elongation at break of the PBST, and PBST copolyester secondary deformation during stretching.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > Polymerization,polycondensation reaction
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