Preparation And Properties Poly(1,3-propylene 2,5-furandicarboxylate)Based Copolyesters And Composites

As the "carbon neutralization" strategy and energy issues have widely been concerned all over the world,furan polyester materials,as a new type of biobased materials,have gradually attracted attention in the traditional biological materials.Among these furan polyester materials,poly(1,3-propylene 2,5furandicarboxylate)(PPF)is an exciting material with high modulus,high glass transition temperature and good gas barrier,which has received much focus.The use and application of PPF is limited in food packaging and agricultural plastic film due to the nature of brittleness and slow crystallization rate.This dissertation aimed at overcoming the inherent defects of PPF and improving the performance of PPF significantly.Specific methods included the introduction of sebacic acid(SA)comonomer to synthesize PPF copolyester and the preparation of PPF/multi-walled carbon nanotubes(f-MWCNTs)composites.The relationship between PPF crystallization behavior and crystal structure was analyzed,which would provide help for the further study of the crystallization mechanism of furan materials.The main research results of this dissertation are as follows:1.Poly(propylene furandicarboxylate-co-propylene sebacate)(PPFSe)copolyestersFully bio-based PPFSe polyesters were synthesized by the two-step melt polycondensation from the biobased monomers,i.e.,1,3-propylene glycol(PDO),dimethyl furanate(DMFD)and SA.The effects of SA content on the thermal properties,crystallization behavior,crystal structure,spherulite morphology and growth,as well as mechanical properties of PPFSe copolyesters were investigated.As the SA content increased,the glass transition temperature,equilibrium melting point,crystallinity,maximum spherulite growth rate,and crystallization transition temperature gradually decreased.In addition,the elongation at break of the PPFSe was significantly improved.2.PPF and f-MWCNTs nanocomposites(PPF-CNTs)PPF-CNTs nanocomposites with different f-MWCNTs contents were prepared by a solution and coagulation method.The dispersion of f-MWCNTs in the matrix,the crystallization behavior,crystal structure,thermal and mechanical properties of the nanocomposites were studied in detail.FMWCNTs could be well dispersed in the PPF matrix,which showed some strong interactions with the matrix.F-MWCNTs effectively enhanced the melt crystallization temperature and isothermal crystallization rate of the PPF-CNTs nanocomposites,while the crystallinity and crystallization mechanism of the PPF remained unchanged.Moreover,f-MWCNTs improved the thermal stability and storage modulus of the composites without changing the glass transition temperature of the nanocomposites.In this dissertation,PPFSe copolyesters were synthesized and PPF-CNTs composites were prepared;therefore,the mechanical properties and crystallization rate of PPF were improved separately.In addition,we further summarized the influence of SA and f-MWCNTs content on the PPF performance.In this dissertation,we also analyzed the factors of affecting the crystallization behavior of PPF,which may provide some insights for the future study of the crystallization mechanism of PPF.