The typical characteristic of slow rebound sponges is that when external forces are applied and withdrawn, the deformation process and recovery trajectory are not nearly instantaneous and synchronous response as common sponges. In particular, when reducing, it starts from the outer edge of the stress core point, gradually recovers from the outside, and finally recovers from the stress core point. According to this characteristic of slow rebound sponge, many cushioning products, cushion materials and crafts have been developed. This property of the slow rebound sponge can evenly distribute the pressure exerted on it by irregularly shaped objects, hence the name zero pressure sponge. At the same time, the weak rebound force can maintain the external objects pressed on the sponge to form the geometric shape, which is also the nickname of memory sponge. Formation mechanism of slow rebound sponge As we all know, sponge is made of polyether polyols and isocyanate as the main material, and add the necessary additives. Under normal circumstances, the use of relatively large molecular weight polyether polyols (such as molecular weight 3000 and above 3000) and polymer polyols (molecular weight 60000 and above 6000) and isocyanate reaction, the preparation is a fast rebound sponge, known as ordinary sponge in the industry. In the preparation of slow recovery sponges, high molecular weight polyether polyols/polymer polyols are al always used in combination with low molecular weight polyether polyols (such as molecular weight 700 and 550). In general, we mix polyethers with molecular weight 3000 or above and polyethers with molecular weight 550 or 700 and react with isocyanate to prepare slow recovery sponges. After the reaction of polyether with isocyanate, chain segments of different molecular weight will be formed. The substance produced by the reaction of high molecular weight polyether with isocyanate is called soft segment, and the substance produced by the reaction of low molecular weight polyether with isocyanate is called hard segment. These segments are held together by chemical and physical bonds, which both intertwine, pile up, and cause slight phase separation due to steric effects. As we all know, high molecular weight polyether has low hydroxyl value and low crosslinking density in reaction with isocyanate, so the soft segment has large intramolecular and intermolecular activity space, easy deformation and recovery, that is to say, the soft segment activity is high. However, low molecular weight polyether has high hydroxyl value, high crosslinking density with isocyanate reaction, small intramolecular and intermolecular activity space, and difficult deformation and recovery, that is, low hard segment activity. The above properties of the soft and hard segments, combined with the slight phase separation within the polymer, cause the slow rebound sponge to show asynchronous deformation and recovery of the soft and hard segments during the process of applying and withdrawing external forces. The reason is that soft section deformation and recovery speed is fast, hard section deformation and recovery speed is slow. This is how a slow rebound sponge is formed.

Polyurethane rigid foam with isocyanate and polyether as the main raw materials, under the action of foaming agent, catalyst, flame retardant and other additives, through special equipment mixed, through high pressure spraying site foaming polymer. There are two kinds of polyurethane foam: soft foam and hard foam. The instructions for the use of polyurethane foam, do not understand the hurry to see. a) Remove dirt and grease from the construction surface, and wet the parts to be filled with a little water. b) Use in the temperature range of 5℃-40℃, if construction in cold season, it is recommended to preheat the tank in an environment of 30℃. c) Shake vigorously for more than 1 minute before use. d) Remove the cover, screw on the special construction gun, invert the tank, slowly press the gun handle, the discharge can be normal construction. The tank is in an inverted state during construction. e) After construction, use cleaning agent to remove the residue on the nozzle and valve to avoid solidification and blockage. f) Surface drying in 20-30 minutes, forming an elastic filling structure within 24 hours. g) The molding filler can be cut, polished and sprayed, this product is not UV resistant, it is recommended to further paint.

Clear formation mechanism of slow rebound sponge, can be based on customer needs, design a reasonable formula. For example, the customer requires the sponge rebound speed to be fast, appropriate to reduce the amount of slow rebound polyether, increase the amount of ordinary polyether; The customer requires that the sponge hardness should be high. It can be satisfied by increasing the amount of slow rebound polyether, replacing part of ordinary polyether with white oil, and improving the TDI index. The problem that slow rebound sponge is easy to obturator can also be solved according to the formation mechanism of slow rebound sponge. Generally, the higher the sponge density, the easier to obturator; The higher the TDI index, the easier it is to obturate foramen. In the production of high-density slow rebound sponges, polyether with molecular weight of 550 and hydroxyl value of 306 is ly used. At this time, the crosslinking density increases, chain segment winding and packing are tight, the degree of phase separation is light, and hard segment is the dominant factor, to high obturator rate. Similarly, at a high TDI index, the cross-linking density increases, the hard segment becomes more concentrated, and the obturator tendency increases. The problem can be solved by increasing the amount of opening agent.

Sponge foaming principle: the foam resin, foam additives and adhesive resin (so that the finished product has adhesion) mixed together; Foaming process is carried out. The foam sponge can be prepared by mixing 80 parts of vinyl acetate (EVA), 20 parts of APAO PT 3385, 20 parts of azodimethylamide, l9 parts of CaCO and 0.6 parts of diisopropylbenzene peroxide in the mold to foam, and then breaking the closed hole with mechanical force. Its density (d) is 0.028 g/cm and 25% compression hardness is 1.9 KPa Common sponge foaming treatment method 1. Manual foaming method, which is the convenient method, will accurately weigh all sponge raw materials. 2. One-step foaming method. The polyether or polyester polyol and polyisocyanate, water, catalyst, surfactant, foaming agent, other additives and other raw materials are added in one step, mixed at high speed stirring after foaming. 3, prepolymer foaming method. Refers to the polyether polyol and diisocyanate prepolymer, and then add water, surfactants, catalysts and other additives in the prepolymer mixed under high-speed stirring for foaming, curing at a certain temperature can be matured. 4. Semi-prepolymer foaming method. Is to make part of the polyether polyol and diisocyanate prepolymer, and then the other part of the white and black materials, catalysts, water, surfactants and other additives are added, mixed under high speed stirring for foaming. This foaming method is similar to the prepolymer foaming method. These are the four foam methods commonly used for sponges. After foaming, sponges can obtain better elasticity and water absorption, which can meet the needs of sponges in many industries. 

1. Emulsification Polyether, isocyanate, water, physical foaming agent, catalyst, color and other materials are not compatible with each other because of their different physical properties. Add the right amount of effective silicone oil, you can let them blend together, close contact. It’s like two people trying to fight, only when they can touch each other can the fight start. 2. Stable bubble effect Under the action of catalyst, the carbon dioxide gas produced by the reaction of water and isocyanate is aggregated to form bubbles and escape under the action of gravity of the reaction system. When the physical foaming agent is added, the physical foaming agent also volatilizes and aggregates into bubbles under the action of reaction heat to escape. If the bubbles cannot maintain a certain stability at this time, it is bound to appear side-by-side and burst bubbles. Once the combined bubbles and broken bubbles are large enough to support the stability of the whole system, then collapse of bubbles will occur and foaming will certainly fail. 3. Homogenizing effect Bubbles gathered in the foaming process have different sizes. At the end of the foaming reaction and the end of the gel reaction, the presence of silicone oil will make the bubbles of different sizes as normalized as possible, that is, the large bubble becomes smaller and the small bubble becomes larger. When the gel reaction ends, the bubble is broken and a network structure of open holes is formed. The molecular structure and amount of silicone oil and the amount of tin have obvious influence on the bubble rupture. If the silicone oil activity is high and the amount is large, then the bubble wall formed will be thick and the surface tension will be large. At the end of the gel, the bubble wine is difficult to break completely, and the liquid on the hole wall is difficult to flow to the sponge meridian immediately, forming a residual film. When the amount of tin is large, the gel speed is fast, the liquid viscosity on the foam wall increases quickly, and the bubble hole is not easy to burst. Even if it bursts, the liquid on the foam wall cannot be completely transferred to the meridians, and some film will remain. These films will be reduced in the sponge maturation process, but it is difficult to completely eliminate, so that after the sponge maturation is completely cut, you will see the reflective film distributed on the cutting surface. These films are particularly obvious on the colored cotton, which has a great impact on the product quality, especially the black industrial cotton. Customers are very picky about the highlights. Iii. Solution It can be eliminated in several ways. 1, choose relatively low activity of silicone oil and the appropriate amount, so that the foam wall of the late foaming foam is thin, easy to break. 2. Use acid-sealed delayed amine to replace part of T-9, give the gel in the foaming process to T-9, and give the delayed amine to complete the post-ripening. In this way, the viscosity before the bubble wall is broken can be greatly reduced, and the liquid can maximize the flow to the sponge meridian after the bubble wall is broken. Reduce film residue. 3. Add sponge to remove film brightening agent and remove residual film by chemical method. Based on the principle of interface technology, the use of organosilicon surfactants can reduce the surface tension of some materials, the selection of reactive organosilicon materials, supplemented by advanced fatty alcohol, through reasonable manufacturing process, successfully developed the sponge film removal and lightening agent WM-655, the product has been applied to the production of black sponge, achieved satisfactory film removal effect. Under the condition that the amount of black paste is the same, the residual film is much less than that without removing film agent, and the blackness is obviously higher than that without removing film agent.