Study On The Modification Of Sr-ferrite/PPS Permanent Magnetic Composites Prepared By Injection Molding

Since the Sr-ferrite and polyphenylene sulfide?PPS?composites possess good permanent magnetic properties and high efficiency in industrial production,they are widely used in the field of polymer-based magnetic composite materials,retaining significant market share.Despite the advantages,the poor mechanical properties of the composite resulted from the PPS resin,which is used as the polymeric binder,limit its application in advanced fields under extreme conditions.To overcame the material's drawbacks of poor impact resistance and brittleness,the TPU elastomers and nano-SiO₂ particles were used as the toughening agents by the melt bending method to modify the composite,aiming at preparing a kind of PPS-based permanent magnetic composites with superior impact strength.In the experiment of modification by two types of TPU elastomers,the TPU-polyether and the TPU-polyester had different effects on the mechanical properties of Sr-ferrite/PPS composites.The TPU-polyether was more suitable as the toughening agent reaching to a critical addition?2 wt%?,after which the impact strength declined.In the experiments,the impact strength and the flexural strength were enhanced to6.02 kJ/m² by 20.2%and 142 MPa by 18.4%respectively compared with those without TPU-polyether addition.However,the TPU-polyester had no effects on improving the impact strength,which was different from the TPU-polyether.The decomposition of the two TPU elastomers at the high process temperatures of PPS resulted in the conspicuous degradation of mechanical properties due to the decrease of the polymer matrix content.The TPU-polyether possessed better chemical bonding with PPS than the TPU-polyester by the formation of sulfuryl carbamate groups,which explained the difference of the effect on the impact strength.The DSC,FT-IR and SEM results also indirectly proved the speculation above in the experiments.In the experiment of modification by nano-SiO₂ particles,the toughening effect on the Sr-ferrite/PPS composite was explored.The results indicated that the composite's impact strength was enhanced up to 6.53 kJ/m² by 30.3%when the nano-SiO₂addition reached to 4 wt%?0.8 wt%in the Sr-ferrite/PPS/nano-SiO₂ ternary system?,at which the flexural strength and tensile strength were hardly affected.Excessive addition of nano-SiO₂ led to evident decline in the mechanical properties.The DSC results showed that proper addition of nano-SiO₂ contributed to the crystallization of PPS,acting as the heterogeneous nucleating agent.But excessive addition resulted in the decline of the crystallinity for PPS.Keeping the crystalline grain of PPS with small size and imperfect structure helped to improve the toughness and impact resistance of the composite.The results of rheological behavior characterization indicated that the addition of nano-SiO₂ led to a decrease in the fluidity of the Sr-ferrite/PPS melt,which would increase the processing difficulty and make the non-Newtonian behavior more prominent.Thus,the actual addition of nano-SiO₂ should not only improve the impact resistance and toughness of the composite,but also make the processing difficulty within the acceptable range.These results above were of guiding significance for industrial production.In addition,the two kinds of modifiers had no significant effect on the permanent magnetic properties of the composites while improving their impact and bending resistance.