Preparation Of Monodisperse Nano-ZnO And Its Application In Polycarbonate Materials

Polycarbonate(PC)is widely used to prepare protective devices due to its good mechanical properties and high transparency.However,due to the lack of UV shielding ability,PC cannot protect the objects in the device from the damage of UV lights.What's worse,PC is prone to yellowing after being exposed to UV rays,which limits its application.Inorganic UV absorbers(TiO2,ZnO,etc.)with good stability can be used as the functional additives in polymers to improve the UV shielding ability of materials.However,when the inorganic particles added are not small enough or agglomerate in the polymer matrix,Rayleigh scattering of light will be caused,and the transparency and mechanical properties of the optical materials will be decreased.In addition,the processing temperature of PC is high,the surface of inorganic particles modifier will partially decompose in the process of melting extrusion,resulting in the yellowing of materials.Therefore,how to prepare inorganic nanoparticles with small particle size,good thermal stability and uniform dispersion ability in the polymer matrix is the key scientific problem in the development of optically functional organic and inorganic nanocomposites.In this paper,monodisperse ZnO nanoparticles were firstly synthesized by reaction precipitation method combined with the modification technique,then highly transparent PC/ZnO nanocomposites with strong UV shielding ability and light aging resistance were prepared by the solution-melt masterbatch method.In this way,ZnO nanocomposites can be evenly dispersed in PC.The preparation conditions on the thermal stability and dispersion of the nano-ZnO and the effects on the properties of PC/ZnO nanocomposites were studied.The contents and conclusions were as follows.Monodispersed nano-ZnO was prepared by reactive precipitation and in situ grafting modification,and the preparation conditions on the morphology,thermal stability and dispersion of nano-ZnO were studied.The suitable preparation conditions were determined:the reaction medium for methanol/ethanol is 1:1,modifier type is d and e,modifier compound quality ratio is 13:1,modifier total amount is 100 wt%,modification time is 3 h,modification temperature is 70?.The prepared ZnO nanoparticles have an uniform particle size of about 6 nm and good thermal stability.Nano-ZnO can be stable monodispersed in DCM to form a highly transparent monodispersion,which can be deposited for 6 months without precipitation.Monodispersed nano-ZnO was mixed with the DCM solution of PC to form the PC/ZnO liquid phase master material.Then,PC/ZnO solid phase master material was prepared by spray drying.Finally,PC/ZnO nanocomposites was prepared by melting extrusion method after blending with pure PC.The effects of drying method and adding amount of nano-ZnO on the optical properties,mechanical properties and light aging resistance of the composite were studied.The results show that the addition of nano-ZnO can not only significantly improve the strength,toughness and rigidity of the material,and but also make the material have good UV blocking ability while keeping the transparency unchanged.Compared with pure PC materials,the tensile strength,elongation at break and single-notch impact strength of PC/ZnO nanocomposites were increased by 10%,25%and 6%after adding 1 wt%nano-ZnO,and the storage modulus E'was also increased by 16%at 100?.PC/ZnO nanocomposites can completely block UV below 370 nm,while the visible light transmittance at 550 nm is 84.5%.In addition,the addition of nano-ZnO can significantly improve the light aging resistance of the material.The radiation test results showed that the anti-yelloping ability of PC/ZnO nanocomposites were significantly improved before and after UV irradiation,and the visible light transmittance of pure PC and PC/ZnO nanocomposites were decreased by 14%and 5%at 550 nm after 480 h of UV irradiation...