Selection of raw materials for polyurethane sheet:
The isocyanate (PAPI) component is selected from Yantai Wanhua PM-200, and this component is fixed. As the amount of PAPI increases, the degree of cross-linking of the foam increases, and the strength and rigidity also increase. However, if the amount of PAPI is too large, the foam will become brittle and the core material is prone to cracks.
First, the choice of polyether polyol is the most important. Polyether polyol is one of the basic raw materials for polyurethane rigid foam, which affects the physical and mechanical properties, dimensional stability and foaming process properties of foam core. After determining the polyether model based on the initiator, hydroxyl value and viscosity, the content of potassium ions in the polyether is selected to be low.
It is preferred that the foam stabilizer has a strong emulsification ability. It mainly controls the cell size, maintains cell stability, and prevents cell collapse. The organosilicone foam stabilizer has a good effect on this, and the amount of the foaming agent can be adjusted in the range of 1.5 to 2.5 (mass fraction) to directly affect the physical properties such as the density and strength of the rigid polyurethane foam. .
The foaming agent can not only adjust and control the density and performance of the foamed product, but also reduce the viscosity of the combined polyether, improve the foaming process, improve the fluidity of the foam, and facilitate foam molding. Taking into account the needs of sustainable development strategies, the use of alternative blowing agents has now been restricted to the use of CFC fluorocarbon compounds that are highly damaging to the ecological environment.
The catalyst can be selected by using a delayed catalytic system to make the whitening time and the gel time interval longer, effectively improve the fluidity of the foaming system, and improve the foaming performance to suit the production process. Factors such as whether the foam is uniform in the cavity, the degree of foaming, and the high closedness of the foam have a great influence on the overall thermal insulation properties of the panel. These factors are related to the firmness of the foam to the cavity wall and the dimensional stability of the foam.
The flame retardant can improve the fire resistance of the foam, but the flame retardant has a destructive effect on the foam during the foaming process, and ensures the use performance and dimensional stability of the foam under the premise of ensuring the flame retardant effect.
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