Preparation And Properties Of Modified Polystyrene Composite Microspheres

Styrene is the most widely used monomer for the preparation of polymer microspheres by monomer polymerization,but the chemical structure of polystyrene determines that it is a brittle material with very low impact strength.Addition of toughening agents is a traditional and effective way to improve the toughness of polystyrene,but current method of preparing polystyrene microspheres cannot directly prepare polystyrene composite microspheres containing macromolecular modifiers.Another method to toughen polystyrene is to dope polystyrene microspheres with inorganic nanoparticles.For polymer microspheres,polymer microspheres somefunctions can be reached by mixing with special nano-inorganic particles.However,how to increase the bonding strength between nonpolar polystyrene and inorganic particles,and how to improve the dispersion of nano-particles in polystyrene phase are the key problems need to be solved in preparing polystyrene/nano-inorganic particles.In this paper,PS/EVA/ZnO composite microspheres and polymer-modified polystyrene composite microspheres were prepared respectively by a new process.The morphology and properties were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermogravimetric analyzer(TGA),dynamic viscoelasticity spectrometer(DMA),Laser particle size analyzer,and Universal testing machine.The new method of preparing PS/EVA/ZnO composite microspheres studied in this paper can be extended to the preparation of PS microspheres filled with other inorganic nanoparticles;the new method of preparing nano PS microspheres blend with polymer-modifiers studied in this paper can be applied to the preparation of other new kinds polymer-modified PS microsphere.Oleic acid,vinyltriethoxysilane,3-(isobutenyloxy)propyltrimethoxysilane(KH-570)and polydimethylsiloxane were used for surface modification of ZnO nanoparticles to investigate the effect of surface modification on the dispersion of ZnO nanoparticles in styrene monomer and water.It was found that the surface modification of oleic acid,vinyltriethoxysilane,KH-570 and polydimethylsiloxane could significantly improve the dispersion of nano-ZnO in styrene monomer at appropriate amounts,but the surface modification of vinyltriethoxysilane and KH-570 simultaneously improved the dispersion of nano-ZnO in water.The surface modification process of oleic acid was very complicated.Therefore,polydimethylsiloxane was chosen as the ZnO surface treatment agent.A new method involving a phase-inversion process was used to prepare PS/EVA/ZnO composite microspheres.SEM and TEM observations showed that nano-ZnO were both embed in the surface and inside of the microspheres;X-ray diffractograms showed all characteristic diffraction peaks of ZnO,indicating that no change in the crystal structure occurred for ZnO in composite microspheres.The addition of EVA and ZnO increased the particle size and widened the particle size distribution.The results of tensile and impact strength showed that the mechanical properties increase significantly with siutable addition of ZnO and EVA.At 10 wt%of ZnO addition and 17.8 wt%of EVA addition,tensile strength and impact strength respectively reached 25.70 MPa and 13.26 k J/m~2 which were 133%and297%higher than the values of PS microspheres,respectively.The results of antibacterial test showed that the composite microspheres of PS/EVA/ZnO had significant antibacterial effect.By using ionic and nonionic compound emulsifiers and carring a radical polymerization after a phase-inversion process,EVA,EP,and SBS modified PS nano-spheres were prepared.SEM and TEM observations showed that the modified nano-PS microspheres are spherical with a size of 10-200 nm.TEM observation showed that nano-PS/EVA microspheres and nano-PS/EP microspheres have core-shell two-phase structure.Compared with the PS microspheres,the tensile strength and impact strength of PS/EVA and PS/EP microspheres were significantly increased with appropriate toughening agent dosage;the tensile strength of PS/SBS microspheres was slightly increased and the impact strength was significantly increased.