When the reaction begins, the increase speed of material viscosity is one of the key factors, and the viscosity increase cannot be too fast or too slow. The viscosity increases too fast, the gas generated before foaming reaction solidifies, so that the density of foam increases, the compression setting performance decreases, just like the steamed buns hair is stiff. However, if the viscosity increases too slowly, the bubble will run away before the reaction is completed. This will lead to the formation of small bubbles and big bubbles, collapse and other phenomena, affecting the strength and tear properties of sponge products. Therefore, the speed of material viscosity increase must be controlled by adjusting the amount of catalyst and foaming agent.
Raw material temperature: Summer: PPG 18-22 degrees TDI 18-22 degrees winter: PPG 23-26 degrees TDI 23-26 degrees spring and autumn 22-24 degrees MC constant temperature control at 23-24 degrees
Adjustment of A33: it is generally mixed with polyether 3010 in the proportion of 1:1 or 1:4. The dosage is mainly related to the temperature of raw materials, the ambient temperature and the density of sponge.
Generally, the reaction time under 20 density is controlled in 90-105 seconds. The reaction time of 20-30 density is 105-120 seconds, that of 30-40 density is 115-140 seconds, and that of above 40 density is 135-160 seconds. The dosage of a-33 can be adjusted according to the reaction time. The lower the density, the less the dosage.
D-19 regulation: in a specific formulation, gradually reduce the amount of stannous acid, to a certain extent, the bubble will burst, but if the dosage increases to a certain level, the bubble will appear closed hole phenomenon. At this time, the soft foam has very poor permeability and elasticity, and it is easy to shrink.
Generally, it is mixed with polyether 3010 in the proportion of 1:1 or 1:4. The dosage of sponge D-19 with 30 density without any additives is 0.15 ~ 0.2, and the lower the density is, the higher the dosage is.
The control of the reaction is mainly to adjust the amount of amine and tin, adjust the reaction time and the opening and closing degree of the pores, so that the reaction can reach a good balance.