Study On Preparation Of Low Density Polymer Microspheres

With the rapid development of polymer microspheres in recent years, the advantages of polymer microspheres have been discovered more and more because of the characteristics of high specific surface area, strong light scattering, large cavity volume, sound absorption, thermal insulation and slow release, etc. Now they are widely used in the fields of biological pharmacy, genetic engineering, catalyst, paint, cosmetics, thermal insulation material, and so on.In this paper, hollow polymer microspheres with cavities and permeable surfaces are synthesized firstly by suspension polymerization. Then taking them as the seeds, the pore canals on the surface are closed by seeded suspension polymerization. In this way, low-density and impermeable polymer microspheres with particle size between 50 and 200 μm are prepared. They will be used as acid mist suppressants. So far as we know, there is no report about this new preparation method of low-density and impermeable hollow polymer microspheres and the use for acid mist suppression.The primary contents of this paper include:A:The preparation of low-density and permeable hollow (porous) polymer microspheres;(a) The effect of stirring speed, content of dispersed phase and PVA (polyvinyl alcohol) consumption on particle size distribution and morphology;(b) The effect of the dosage of porogen (toluene) on the density and cavity volume rate;(c) The effect of the dosage of porogen (toluene) on the pelletizing ratio and morphology;B:The preparation of low-density and impermeable hollow polymer microspheres;(a) The influences of amount of pre-coating monomer, stirring speed, amount of dripping monomer, initiator and PVA dosages on the closing results;(b) The optimized preparation of low-density and impermeable hollow polymer microspheres and the experiments for inhibiting acid mist;After the above research, the main conclusions are shown as follows:1、Stirring speed, content of dispersed phase and polyvinyl alcohol consumption have deep effects on particle size distribution. To meet the requirements of acid mist suppression, the effects of above factors on particle size were compared jointly and the optimum preparation conditions were determined. For preparing hollow polymer microspheres between 50 and 200 μm, the reaction conditions are that:the stirring speed is 550rpm, the content of dispersed phase is 16.2%, and PVA consumption is 1%.2、Toluene which is a kind of porogen has an important effect on the cavity volume rate, the density and the pelletizing ratio of hollow microspheres. With the increase of the dosage of toluene, the cavity volume rate will increase, and the density will decrease. When the amount of toluene increases from 10% to 70%, the cavity volume rate adds 6% to 10%, the density drops from 0.989g/cm3 to 0.8898g/cm3. With the further increase of toluene dosage, the pace of the increase of the cavity volume rate slows down, the density also decreases slowly. When the amount of toluene reaches 130%, the cavity volume rate can attain 11%, and the density can be low to 0.8688g/cm3. But the breakage ratio of microspheres grows continuously with the increase of the amount of toluene.3、With the increase of dosage of toluene, the density of polymer microspheres reduces continuously. When the amount of toluene is 130%, the density of microspheres is 0.9645g/cm3.But when the amount of toluene reaches 40%, the floating amount of microspheres is the highest about 36.7%. It shows that the closing technique may be more effective to the small pore canals of microspheres. When the amount of toluene is more than 70%, the floating rate of microspheres will increase continuously with the increase of the dosage of toluene.4、In the experiments of space simulator of acid mist suppression, while 20% (wt%) hydrochloric acid was covered with polymer microspheres prepared, the decrease of pH value of the air in the dryer slowed down obviously. With the increase of the layer thickness of microspheres covered, the change of pH value in the dryer was observed slower. It shows that low-density and impermeable polymer microspheres prepared in this paper are effective to suppress acid mist.