Methylene chloride is abbreviated as MC, with molecular weight of 85 and gasification heat of 29KJ/mol. It is a commonly used physical foaming agent.
MC has two effects on the temperature of polyurethane soft foam: one is to absorb the reaction heat (gasification heat) and the other is to dilute the exothermic reaction (PV/T = constant).
The increase of MC will obviously increase the elongation of foam, but it will not necessarily increase the tear strength of the foam. The elongated foam is not the same as not being easily torn.
The increase of MC will reduce the side temperature of the foam when the internal temperature rises, which is not conducive to the formation of hard segments. Therefore, adding MC is easy to soften the foam and make it feel elastic, but the elastic resilience of the foam will not be very high.
The small increase or decrease of MC can be balanced by adjusting tin component separately. The large addition or subtraction of MC affects the reaction heat and concentration of the formulation. It is necessary to adjust several components to balance them. For example, the formula of PPG: 100, TDI: 57, water: 4, MC: 3, if MC becomes 4 parts, without considering density and other physical properties, only 3%~4% tin is needed. If MC becomes 14, then adding tin alone is no longer desirable. It is easy to achieve a new balance only if cyanide, water, silicon, amine and tin are changed.
MC gasification can take away heat, so it can be used as raw material to cool down in summer when doing vesicle experiment.
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