Polyurethane Foam Pore Structure Control Study

The goals for this work are to get a better understanding on mechanism of controlling cellular structure of polyurethane foam and study the effects of some important parameters on the cellular structure. The lab condition of finely foaming has been got by experiment,on the base of which,the work focuses on the controlling of cell structure,especially on cell size. The controlling technology has been found by experiments.Factors including catalysts system,water blowing agent,TDI index as well as temperature,which affect the finely foaming,are studied. And the lab conditions of finely foaming for polyester foam and polyether foam have been got. It was concluded that controlling the equilibrium of blowing reaction and gelling reaction is critical for finely foaming,and the dosage ratio of amine catalyst and stannum catalyst was the main factor,which has an impact on the equilibrium. The change of dosage of water blowing agent,TDI index or temperature can impact the equilibrium.After analyzing the physical process of polyurethane foam formation,such conclusions can be got:bubble nucleation and bubble growth affect cell size primarily. In this system,to improve bubble nucleating and to constrain defoaming during bubble growing can get the foam with fine cells.Stirring speed's increase and adding micropowder may affect cell size by improving bubble nucleating. In fact,Increase of stirring speed has decreased cell size and improved cell size distribution;adding micropowder has not positive effect on improving cell size. The amount of organic stannum catalyst can improved cell size by constraining defoaming,especially for polyether system,which has low viscidity. Organic silicone which acts as surfactant has great influence not only on bubble nucleating,but also on bubble growth,so it can affect the cell size remarkably. But there is selectivity on silicone surfactant for special system. L-600 can make polyether foam's cell smaller but polyester foam's cell bigger. When L-600 and SE-232 are used in polyester foam simultaneously,foam with cell size in 10-60PPI can be controlled optionally by adjusting the dosage ratio. Additional pressure not only constraints the bubble growing,but also increase the number and homogeneity of bubble nucleation. As a result polyurethane foam with fine cells can be got by the technology of foaming under variable pressure.In my study,polyurethane foam with cell size in 10-60PPI can be controlled optional,ait the same time the foam with cell size in 100PPI and narrow distribution also can be got by the technology of foaming under variable pressure.