Shell Powder Modification And Application In Thermal Insulation Coatings

Thermal insulation coatings can effectively reduce the surface temperature of buildings to prevent the indoor temperature from rising,which will reduce the use of refrigeration equipment,thereby save energy.The main materials for reflective in thermal insulation coatings are pigment and filler;the common pigment is titanium dioxide;the common filler is calcium carbonate.Shell powder is made from waste shell,in which the calcium carbonate content is about 95%.Making waste shell to be shell powder,and using shell powder in thermal insulation coatings can protect the environment,while reduce the cost of coating.In this research,the shell powder,which was with chemical surface modification and calcination,was modified to reduce the agglomeration of shell powder and increase the reflectivity of shell powder,at the same time,the property of coating with modified shell powder and the property of coating with unmodified shell powder were studied.Four kinds of modifiers,sodium stearate(SS),oleic acid(OA),maleic anhydride(MA)and titanate coupling agent(TCA),were used to chemically modify the shell powder to reduce the agglomeration of shell powder,and improve the compatibility of shell powder and organic purposes.The oil absorption rate,settlement rate,reflectivity and static water contact angle of shell powder were tested before and after modification.The experimental results show that the modification effect of SS and OA are better than that of MA and TCA.The oil absorption rate of modified shell powder decreases obviously,the settlement rate of modified shell powder increases and the static water contact angle of modified shell powder increases.Mainly because the hydrophilic end of the modifier molecule contacts the shell powder surface,and the hydrophobic end gradually envelopes the shell powder particles,changing the shell powder from hydrophilic to hydrophobic.Use modified shell powder and hollow beads as filler,titanium dioxide as pigment,water-based fluorocarbon emulsion as film-forming material to prepare thermal insulation coatings.The reflectivity,thermal insulation property,static water contact angle,scrub resistance,and adhesion strength of thermal insulation coatings were tested.The experimental results show that the reflectivity,thermal insulation property,static water contact angle,scrub resistance,and adhesion strength of thermal insulation coatings with modified shell powder have increased,thermal insulation coatings with SS and OA modified shell powder have better properties than that of coatings with MA and TCA modified shell powder.Modified shell powder can disperse more evenly in the emulsion,connect stronger with emulsion molecules,so the dry coating can produce more scattering interface,which is the reasons why the thermal insulation coatings with modified shell powder have better properties than that of coatings with unmodified shell powder.In order to remove a small amount of organic matter contained in the shell powder and improve the reflectivity of shell powder,calcine the shell powder for 1h at different temperatures,and use the calcined shell powder with good performance to prepare thermal insulation coatings.The experimental results show that the organic in shell powder decomposes completely at 400 ?,the powder refines and the shell powder reflectivity increases gradually,while the temperature increases from 100 ?to 400 ?.When the calcination temperature is over 400 ?,the shell powder is sticking and the reflectivity decreases.The thermal insulation coatings with 400 ?calcined shell powder have the highest reflectivity and the best thermal insulation properties.The wash resistance times of thermal insulation coatings with calcined shell powder and non-calcined shell powder are about 2000 times,but the thermal insulation coatings with calcined shell powder have improved adhesion strength than that of coatings with non-calcined shell powder.