There are the following factors that affect the resilience of polyurethane soft foam：
(1) Pore opening rate
When the pore opening rate of the product is high, most of the polymer is evenly distributed in the naturally perforated foam meridians, so the resilience of the product is higher; when the pore opening rate of the product is reduced, because the complete pore wall has a higher uncompressibility than the perforated foam, therefore, the resilience of the product decreases.Therefore, the amount of foaming agent can be appropriately increased, and the surface tension of the pore wall can be adjusted to make the pore wall rupture with moderate ease, thereby improving the pore opening rate of polyurethane foam.
(2) Pore shape
When the regularity of the pore shape increases, the resilience of the polyurethane foam increases, and the polyurethane foam with the spherical pore structure has good resilience.Polyurethane foams with needle-like pore structure are prone to pore collapse.Therefore, the foaming temperature can be appropriately reduced to avoid the pores from squeezing and deform each other due to excessive expansion.
(3) Pore size and distribution of pores
In the same system, foams with a larger proportion of small pores will have a larger rebound rate.However, the pore size of the cell is not as small as possible, but there is an optimal value.In addition, the rebound rate of foam plastic increases with the increase of pore density, and the largest possible pore density can only be obtained when the pore size is reasonably distributed.Therefore, the pore stabilizer can be increased in moderation.
(4) Polyether polyol
Within a certain range, the greater the relative molecular weight of polyether polyols, the better the molecular chain flexibility and the better the resilience. Beyond this range, the hardness of foams decreases.However, when using polyether polyols with relatively large molecular mass, measures should be taken to reduce their degradation.For example, add an appropriate amount of antioxidants before the polymerization reaction.
(5) Isocyanate
In the formulation, attention needs to be paid to controlling the isocyanate index, which is the TDI index. The TDI index refers to the ratio of the actual amount of TDI to the theoretical calculation of the required amount.The hardness of the foam can be easily and safely controlled in the range of TDI index 105~115.Within a certain range, with the increase of the TDI index, the hardness and resilience of the foam plastic increase.Therefore, the TDI index can be appropriately increased.
(6) Other factors
As the mass ratio of water to polyol increases, the resilience of the foam increases first and then decreases.Therefore, the amount of water added can be adjusted to maintain high resilience.With the increase of the mass ratio of the chain extender to the polyol, the tensile strength of the product increases and the resilience decreases.Therefore, the chain extender can be appropriately reduced.