Study The Effects Of Highly Dispersed Silica On The Extinction And Defoaming Of Unsaturated Polyester Resin

Unsaturated polyester resin(UPR)as one of the most widely used thermosetting resins,has the advantages of low cost,low density,high corrosion resistance and excellent processability.Usually,UPR requires further addition of fillers for modification before practical use.Inorganic particles are regarded as optional candidates,but they often exhibit poor dispersion and compatibility.In recent years,our group have developed a series of highly dispersed and reactive silica nanoparticles via in situ surface-modification technique,and studied the reinforcing and toughening effects on silicone rubber,nylon,unsaturated polyester resin and other polymer materials.In this paper,highly dispersed silica surface modified with hydrophobic and(or)reactive groups is used as modifier to study the effects of nano-silica on the extinction,defoaming and toughening performance of unsaturated polyester resins.The main research contents and results are as follows:1?Silica is evenly dispersed in the UPR via emulsification method,to prepare low viscosity matting coatings.A series of characterizations are performed including the multi-angle gloss meter,rotational viscometer,portable pencil hardness tester and Omec laser granulometer,to investigate the effects of particle size,oil absorption value,pore volume and surface hydroxyl content of silica on the extinction performance of UPR.The results show that the silica with small particle size,large pore volume and high oil absorption has better extinction performance,the presence of DNS-3L can reduce the gloss of pure resin from 81.5 to 11.8,exhibiting a prominent extinction effect.In the meanwhile,the presence of hydrophobic organic functional groups on silica surface induces,low viscosity of matting UPR,when the additive amount was 1%,the viscosity enhancement of DNS-3L was 3/5 of unmodified silica(DNS-0),and 1/5 of the gas phase produced silica(EH-5),bringing great convenience for resin processing.2?Highly dispersed silica is mixed with dimethyl silicone oil to prepare cream like antifoam agent.The influence of various types and different particle size of silica on the dispersion stability of the antifoam agent is investigated and the effects of the silica surface hydroxyl content,oil absorption value,and addition amount on the performance of defoaming agent are also evaluated.Experimental results show that the hydrophobic silica has good dispersion stability and antisettling in defoaming agent,the silica with small particle size,small surface hydroxyl content and high oil absorption has better defoaming performance,addition of DNS-3L/PDMS with 0.02 g can eliminate foam within 2~3s in 60 ml foaming liquid.Compared with the commercially available hydrophobic silica,our modified silica shows excellent defoaming property to the foaming liquid.In particular,as-made defoaming agent can obviously suppress defoaming phenomena in UPR,which can reduce the pinholes of UPR coating and make the coating more smooth.3?In order to investigate the effects of silica as matting agent,and defoaming agent on the mechanical behaviors of UPR,different types and different amount of silicon dioxide are chosen to evaluate tensile and impact properties.At the same time the effects of silica on the alkali resistance of the hybrid materials are analyzed.The structure and properties of silica and hybrid materials are characterized by Fourier transform infrared spectroscopy,thermogravimetric analyzer,field emission scanning electron microscope.Experimental results show that addition of DNS-3L with a content of 1% can increase the tensile strength by 18.5%;that addition of DNS-3L with a content of 1.5% can increase the impact strength by 60.7%,respectively,compared with those of the pure UPR.To improve the interaction between silicon dioxide and UPR,further study of silica surface-modified by various degrees of double bonds on the mechanical behaviors of UPR is examined in terms of tensile properties and impact performance of hybrid material.When the addition amount of DNS-D silica is 1% with a double-bond amount of 25 mmol/kg,the tensile strength of the hybrid material is 54.2% higher than that of pure UPR;when the amount of DNS-D silica is 1% with a double-bond amount of 12.5 mmol/kg,the impact strength of the hybrid material is 95.7% higher than that of pure UPR.Furthermore,both the dispersible silica DNS-3L and reactive silica DNS-D can significantly improve the alkali resistance of UPR.The above results show that surface modified,highly dispersed silica can be used to produce UPR-based matting agent and defoaming agent with low viscosity,and simultaneously significantly improve the mechanical properties of resin materials.This product is expected to be used in other coatings,such as epoxy resin and polyurethane coating products.