Synthesis,Crystallization Behavior and Properties of Poly(butylene Succinate) and Its Copolyesters

Author:Dai Xun

Supervisor:qiu zhao bin

Database:Doctor

Degree Year:2017

Download:153

Pages:143

Size:15562K

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To reduce the pollution arised by polymers and use less fossil resources,biodegradable polymers and bio-based polymers are getting more attention in recent years.Poly(butylene succinate)(PBS)is a biodegradable polyester with promising future and can be prepare by bio-based chemicals.In this work,a series of PBS-based polyesters were successfully synthesized through copolymerization process to enlarge the application field.1.Biodegradable poly(butylene succinate-co-octamethylene succinate)(PBOS)copolyestersA series of PBOS copolymers containing different contents of octamethylene succinate(OS)units were synthesized successfully through a two-step melt polycondensation method and the effects of OS units on the properties of PBOS were studied.The copolymers PBOS had the same crystal structure as the homopolymer,while the crystallinity values of PBOS were smaller than that of PBS and gradually decreased with increasing the OS content,because of its copolymer feature.PBOS possessed relatively high thermal stability,regardless of the OS content.During nonisothermal crystallization process,The increase of the OS content led to a restriction in the crystallization of PBOS.As OS composition and crystallization temperature increasing,the overall isothermal melt crystallization rates of PBOS decreased;however,the crystallization mechanism of PBOS and PBS remained unchanged.Increasing crystallization temperature and OS composition decreased growth rates of PBOS spherulites.The mechanical properties study revealed that the elongation at break obviously increased,while the yield stress,tensile strength and Young modulus of PBOS decreased gradually with increasing the OS composition.The mechanical properties can be adjusted for large-scale applications.The hydrolytic degradation experimental results showed that weight loss increased almost linearly with hydrolytic degradation time for all the samples,and the hydrolytic degradation rates of PBOS copolyesters gradually decreased with increasing OS composition.2.Bio-based poly(butylene succinate-co-decamethylene succinate)(PBDS)copolyestersA series of PBDS copolyesters containing different decamethylene succinate(DS)fractions were successfully synthesized with bio-based chemicals.The crystal structure of PBDS remained unchanged and the degree of crystallinity values slightly decreased with increasing the DS composition.The thermal stability of PBDS remained unchanged,irrelevant to the DS composition.With increasing DS units,the nonisothermal and isothermal melt crystallization of the PBDS copolymers were retarded,while the crystallization mechanism did not chang.The composition dependence of the melting point temperature for the PBDS copolymers was well described by the Flory equation.For PBDS45,the separate crystallization of each phase was clearly observed during cooling from the self-nucleation temperature.With the DS composition and crystallization temperature increasing,the nucleation density and growth rates of PBDS spherulites decreased.A crystallization transition from regime II to regime III was detected for each sample.The copolyesters with higher DS content showed greater elongation at break,while smaller yield stress,tensile strength,Young modulus and hydrolytic degradation rates were observed.3.The effect of diols with different chain lengths on the properties of poly(butylene succinate)copolymersAll the PBS 15 copolyesters and PBS had the same crystal structure and high thermal stability.With increasing the chain lengths of different comonomer diols,the glass transition temperature,the overall crystallization rates,and tensile strength values of copolyesters decreased significantly,while the apparent melting point temperature remained fairly constant.The weight loss of copolyesters and PBS both linearly increased with the degradation time extended.The hydrolytic degradation rates decreased as the chain lengths of comonomer diols increasing.The degradation rates of copolyesters and PBS were ranked from high to low as follows:PBES,PBS,PBHS,PBOS,and PBDS.4.Bio-based poly(butylene succinate-co-butylene oxalate)(PBSO)copolyestersA series of PBSO copolyesters were synthesized similar to those of the previous studies.Thermostability of PBSO were reduced with increasing the SO content.The crystal structures was almost the same as those of PBS.SO units slowed down the crystallization of PBSO both in nonisothermal and isothermal crystallization processes,while the crystallization mechanism did not changed.With SO composition increasing,the spherulitc size of PBSO obviously increased at the same degree of supercooling;moreover,the spherulitic growth rates of PBSO reduced when the crystallization temperature and the SO content increasing.5.Synthesis and thermal properties of novel bio-based poly(decamethylene succinate)(PDS)In this work,we synthesized PDS with bio-based monomers via a two-step melt polycondensation method.The crystal structure of PDS was investigated with WAXD.Thermal stability of PDS was similar to PBS and Poly(ethylene succinate)(PES).The basic thermal behaviors,overall isothermal melt crystallization kinetics,crystal structure,of PDS were systematically investigated for the first time.The overall isothermal melt crystallization kinetics of PDS was investigated at different crystallization temperature values and analyzed by the Avrami equation.Within the investigated crystallization temperature range,the crystallization mechanism of PDS did not change.