Study On Preparation And Crystallization Behavior Of Polymer Magnetic Composites

Fe₃O₄ nanoparticles have unique superparamagnetism due to its quantum size effect and small size effect.Meantime,it has low toxicity and good biocompatibility,which have been applied in biomedical field.Reverse spinel cobalt ferrite(Co Fe₂O₄)were synthesized through dropping cobalt ions on the basis of the preparation of Fe₃O₄ nanoparticles,which improved the magnetism of the particles and made them more widely used in some fields,such as catalyst,magnetic fluid,magnetothermal,new energy,biological medicine carrier,and so on.The white pollution has been gradually solved due to the usage of degradable polymers(poly(?-caprolactone),polylactic acid,etc.).Meantime,they have been favored by material researchers because of its good biocompatibility.In this paper,Fe₃O₄/poly(?-caprolactone)(PCL)and Co Fe₂O₄/polylactic acid(PLA)composites were prepared by solution casting method,then their structures and properties were studied.(1)The Fe₃O₄/PCL nanocomposites were prepared through solution casting method.The microstructure and crystal size of the composites were analyzed by TEM and XRD,respectively.Differential scanning calorimetry(DSC)and polarizing microscopy(POM)were used to study the effects of Fe₃O₄ nano-particles content on the non-isothermal crystallization and isothermal crystallization behavior of PCL.The thermal stability of the composites was analyzed through thermogravimetric analyzer(TGA).The results show that nano-Fe₃O₄ particles were uniformly dispersed in the matrix with the size of about 5?8 nm.The Fe₃O₄/PCL nanocomposites were successfully prepared by this method.A small amount of nano-Fe₃O₄ particles have obvious heterogeneous nucleation effect on PCL crystallization and promote the matrix crystallization.However,excessive nano-Fe₃O₄ particles have certain hindrance on crystallization.The thermal stability of the nanocomposites was reduced with the addition of nano-Fe₃O₄.The above research results indicate that the effect of nano-Fe₃O₄ particles is not linear,whereas has an optimal filling amount on the crystallization of PCL matrix.(2)The cobalt ferrite(Co Fe₂O₄)precursor was synthesized via chemical coprecipitation method.Subsequently,the precursor was coated by oleic acid to make it uniformly dispersed.Finally,the magnetic particles were obtained through high temperature treatment.Co Fe₂O₄/PLA magnetic composites were prepared by solution casting method.The structure and crystallization properties of the composites were characterized by FTIR spectrometer,XRD,POM,and DSC.The solution crystallization,non-isothermal melt crystallization and isothermal melt crystallization behavior of PLA matrix were studied.FTIR results show that a weak absorption peak gradually appears at 604cm^-1,which belong to the stretching vibration of Co?O–Fe,and its strength increased with the increase of the addition of Co Fe₂O₄ particles.Therefore,Co Fe₂O₄/PLA magnetic composites can be prepared by solution casting method.The XRD results indicated that the characteristic diffraction peak strength of PLA matrix increase firstly and then decrease gradually with the addition of Co Fe₂O₄ particles.The results of non-isothermal crystallization of Co Fe₂O₄/PLA magnetic composites showed that the crystallinity of the composites is significantly improved after the addition of nanoparticles.The results manifested that the crystallization rate of Co Fe₂O₄/PLA composites is faster than that of pure PLA.Under the condition of isothermal melting and crystallization,the density of PLA spherulites in the composites increased obviously and the size decreased with addition of Co Fe₂O₄ particles.