Study On The Surface Modification And Composite Materials Of Expanded And Vitrified Small Ball

Expanded and vitrified small ball (EVB) was a new type of inorganic thermal insulationmaterial with the light-weight characteristics. It has excellent properties of light and fireproof , stable physical and chemical natures, low water absorption, thermal insulation andso on, which makes EVB was be used as lightweight insulation material that can be widelyused in building industry. However, the surface of some EVB particles is not completelyclosed in the continuous verification process. In another case, EVB are bumped with eachother and then some breakages may be formed. These defects result in the unstablemechanical strength, depressed thermal insulation and evidently degrade the performance ofEVB. Therefore, how to keep its excellent properties and improve strength becomes a keyfactor in its application. In this paper we studied the bulk density, volumetric waterabsorption, thermal conductivity and cylindrical compress strength of the modified EVB, andthe composites boards were studied.The main research work and achievements we gained as follows:This study investigated the effects of the size of expanded and vitrified small ball on itsproperties, such as bulk density, volume water absorption, dehydration rate, moisture sorptionperformance, thermal conductivity and cylindrical compress strength. Except the moisturesorption performance, the others decreased with the size of EVB increasing largely.What’s more, the EVB was modified by the coating of the thermosettingUrea-formaldehyde resin (UF) and Phenol-formaldehyde resin (PF), the effect of resincontent on the bulk density, volumetric water absorption, thermal conductivity andcylindrical compress strength of the modified EVB was studied. The obtained results showedthat, the modified EVB had a better performance on the properties of volume waterabsorption and the cylindrical compress strength. With the increasing of resin content, thevolume water absorption decreased a lot, the cylindrical compress strength increased largely.The thermal conductivity changed a little, still met the requirement of efficient thermalinsulation material. The EVB modified by PF had a better performance on the properties ofthe bulk density, volume water absorption and thermal conductivity than the modified EVBusing UF as modifier, but the latter had higher cylindrical compress strength.In order to broadened application scope of EVB，The EVB/ resin composite wasprepared and the effect of resin content , two kinds of resin, two sizes of EVB on thecompressive strength, the impact strength and thermal conductivity of the duality compositeboard was studied. The EVB/ resin composite were prepared with wt% of 100%, 125%,150%, 175% and 200% by mixing together the appropriate quantities of resin and EVB. Theresults showed that the compressive strength and he impact strength increased with the resincontent increasing, the thermal conductivity changed a little but showed a downward trend.In the same condition, the compressive strength, the impact strength of the phenolic resin/EVB composite were higher than of phenol-formaldehyde resin/EVB composite，the thermalconductivity and the bulk density of the phenolic resin/ EVB composite were smaller than of Phenol-formaldehyde resin / EVB compositeFurthermore, the sisal fiber (SF) was used to reinforce the resin/ EVB composite. TheSF and the EVB weight ratio were 0%、2%、4%、6% and 8%, the SF was about 0.5-1.0mm ,the resin and the EVB weight ratio was 150%, the influence of the content and length of SFon the properties of composite board was also discussed. The results indicated that, thecomposite board showed better mechanical properties and good heat-retaining properties. Asthe SF content increased the impact strength of the composites with a large rise. Thecompressive strength was slightly decreased; the thermal conductivity ranges increasedslightly. The fibers with the length of 15-20mm showed more reinforcement effect than thefibers with the length of 5-10mm.