| PHBV is a kind of bio-based polyester in the form of starch and discarded fruits synthesized from microbes.PHBV has the advantages that it is green,environmental and renewable.However,a series of defects such as narrow melting window,high crystallinity and large spherulites of PHBV limit its wide application in many fields.Therefore,in order to improve the defects of PHBV,physical and chemical modification are adopted respectively in this paper.The research contents and conclusions of this thesis are as follows:(1)PHBV was physically modified by a new organic/inorganic hybrid material POSS to prepare PHBV/POSS hybrids containing different POSS contents.The results showed that the introduction of POSS slowed the crystallization rate of PHBV and the crystallinity of PHBV/POSS hybrids decreased by 14.3%.The Avrami equation successfully described the isothermal crystallization kinetics of PHBV/POSS hybrids.The higher the isothermal crystallization temperature of PHBV/POSS hybrids,the slower the crystallization rate.The spherulites of PHBV and PHBV/POSS hybrids exhibited characteristic black cross extinction.The addition of POSS could significantly improve the tensile properties of PHBV.PHBV/POSS hybrid containing 20 wt%POSS had the highest stress of 6.1 MPa.(2)Nucleating agent TMC-306 and PLA were used to modify PHBV by melt blending.PHBV/BN/TMC-306,PHBV/TMC-306,PHBV/PLA,PHBV/PLA/TMC-306 four blending systems were prepared.The results showed that in PHBV/BN/TMC-306 blending system,the content of TMC-306 was increased to dilute and slow down the crystallization of PHBV/BN;In PHBV/TMC-306 blending system,the crystallization rate was improved with the addition of TMC-306.In PHBV/PLA blending system,pure PLA had no obvious crystallization peak.With the addition of PHBV in blending system,the crystallization peak gradually increased and the crystallization temperature was about 80°C;In PHBV/PLA/1%TMC-306 blending system,when the content of PHBV was more than 30%,TMC-306 promoted the crystallization of PHBV.The higher the content of PHBV,the sharper the crystallization peak.From the above results,PHBV/BN having a high crystallization rate was selected for spinning.It was concluded that the chain structure of PHBV fibers was consistent with the chemical structure of PHBV raw material;After drawing,PHBV fibers had higher crystallinity and orientation induced crystallization;After secondary stretching,the rate of one roll was 81m/min,the rate of another roll rate was 363 m/min,draw ratio was 5.72,PHBV fibers under this parameter would have better mechanical properties than which with first stretching,a rate of 68 m/min and a draw ratio of 6.8.(3)By chemical block copolymerization,dibutyl dilaurate was used as a catalyst,and hexamethylene diisocyanate(HDI)was used as a coupling agent.A flexible macromolecular PEG and an organic/inorganic hybrid material POSS were introduced into PHBV macromonomer to prepare PHBV/PEG and PHBV/PEG/POSS block copolymers.It was concluded that the average molecular weight of PHBV/PEG block copolymer was 1.9×10~4,and the average molecular weight of PHBV/PEG/POSS block copolymer was 1.1×10~4.The molecular weight distribution of the block copolymers was between 1.30 and 1.85.The content of POSS was so small in PHBV/PEG/POSS block copolymer that POSS could not form a separate crystal phase.The crystallization ability of block copolymer was weak;The introduction of POSS made the thermal stability of PHBV/PEG/POSS higher than PHBV/PEG;The introduction of POSS changed the morphology of PHBV spherulites.With the increasing of isothermal crystallization temperature,the growth rate of PHBV-based block copolymer spherulite was accelerated;The addition of block copolymer was confirmed by electrospinning to increase the spinnability of PHBV. |
PDF Full Text Request