Application Of Polyvinyl Alcohol Modified By Sodium Ailicate

To improve water resisitance of polyvinyl alcohol(PVA),polyvinyl alcohol was modified by sodium silicate,and applied in paper coating.The dependence of polyvinyl alcohol / sodium silicate solution viscosity on shear rate and temperature was studied by the steady state rheological behavior.To study the relationship between the structure and properties of modified polyvinyl alcohol,it was characterized by infrared spectroscopy(FITR),X-ray diffraction(XRD),dynamic thermo mechanometry(DMA),differential scanning calorimetry(DSC)and thermal gravimetric analyzer(TGA).Polyvinyl alcohol / sodium silicate solution mixed with duplex board coating was used for the surface of whiteboard.The main works and conclusions were shown as follows:1.An organic-inorganic composite was prepared by the reaction of sodium silicate with polyvinyl alcohol at the presence of acidic catalyst,to study the water resistance at different conditions.The results showed the suitable preparation conditions was that phosphoric acid as catalyst,the content of sodium silicate was 12.5-15%,p H was less than 2,the heat treatment temperature was between 120 ℃ to 140 ℃,heat treatment time was more than 40 min.2.Steady state rheological behavior was studied and the results showed the steady shear curves of polyvinyl alcohol/sodium silicate solution indicated three regions at shear rate between 0.1 1/s to 100 1/s,the first thinning region,the first plateau and the second shear thinning region.Compared with pure PVA solution,it had higher viscoisity,stronger dependence on shear rate.3.The relationship between the structure and properties in this polyvinyl alcohol/sodium silicate film was studied and results showed PVA and Na2 Si O3 formed Si-O-C bond,the cross-linked structure was existed.Compared with pure PVA,crystallinity of PVA was reduced,the glass transition temperature increased,the thermal stability and water resisitance improved;the mixture of sodium silicate or phosphate could not improve the water resistance of PVA,but would decrease its thermal stability.With the increase of sodium silicate content,the crystallinity was reduced,the glass transition temperature increased,the thermal stability and water resisitance improved in a certain range of dosage of sodium silicate.4.Polyvinyl alcohol/sodium silicate solution blending with duplex board coating was used for the surface of duplex board,the results showed that water absorption of the white board paper was reduced by adding a small amount of polyvinyl alcohol / sodium silicate solution to the coating.