Aggregation Structure And Properties Of Natural Protein Fibers And Aliphatic Polyester Composites

Poly(butylene succinate)(PBS),poly(butylene adipate)(PBA)and poly(L-lactide)(PLLA)are biodegradable aliphatic polyesters.It has been shown that their degradation rate,processing time and thermodynamic stability was greatly affected by the crystalline structure and oriented structre,which can be precisely controlled by means of their intermolecular forces and lattice matching relationships with polyethylene fibers and other synthetic fibers.It is not clear how the protein fibers affect the crystallization behavior of polyesters.However,the further study of the intermolecular interactions between natrual protein fibers and aliphatic polyesters are required.In present study,the composites of PBS/PBA,PLLA/collagen fiber and PBA/silk fiber were chosen as the main research objects.Polarizing microscope(POM),scanning electron microscopy(SEM),differential scanning calorimetry(DSC),Fourier transform infrared spectrometer(FTIR)and wide angle X-ray diffractometer(WAXD)were used to investigate the interface formation mechanism and structure of the composites.The main results are shown below:(1)The DSC and WAXD results show that the oriented PBS crystals strongly induce the PBA nucleation and favor the formation of ?-phase crystals without being affected by the crystallization temperatures.In-situ observation of the PBS/PBA blends sheared at different shear rates by POM clearly indicate that the degree of orientation of the PBS crystals increases with the increase of the shear rate.The highly oriented PBS crystals show a strong ability to induce nucleation and significantly accelerate the crystallization rate of PBA.The Raman and 2D WAXD measurements of PBA on PBS substrate reveal that there is lattice-matched relationship between the ?-PBA(020)plane and the ?-PBS(110)plane.(2)The results show that the network structure of silk fibers hinders the movement of PBA molecular chains,then lowered the crystallization temperature of PBA.However,the increase of PBA's melting temperature after introduce silk fibers indicates that the PBA crystals in their composites are more perfect.The results of DSC and WAXD experiments show that the strong nucleation ability of PBA on the surface of silk fiber results in the formation of ?-PBA crystals.The FTIR results show that there are hydrogen bond interactions between silk fibers and PBA crystals in PBA/silk fiber composites.Such strong intermolecular forces will enable the orderly arrangement and deposition of PBA molecules on the surface of silk fibers.(3)The collagen fibers have high nucleation ability toward the PLLA as demonstrated with the increasing crystallization rate and the formation of ?-form PLLA crystals with more thermodynamic stability.The FTIR results show that collagen fibers affect the crystallization behavior of PLLA by form hydrogen bond interactions between the amide groups of the collagen fibers(before and after denaturatio)and the carbonyl groups of the PLLA materials.SEM studies of the interfacial structure of the collagen fibers and PLLA before and after denaturation show that both the collagen fibers and the PLLA had good binding ability before.