Silicone Modified Polyurethane
Jul 24, 2023
Due to the characteristics of its molecular structure, the compatibility of polyurethane and silicone is poor, and the solubility parameters of polyorganosiloxane and polyurethane chain segments differ greatly. The two resins have extremely strong incompatibility. They are in a state of severe phase separation in the blend system, and the mechanical properties of the blend are low. It is necessary to add compatibilizers in the blend system to improve the compatibility of each component of the blend.
Blending modification is only a simple physical mixing without the formation of Chemical bond. The migration of Zhu oil makes silane aging shorter. Moreover, the emulsifiers in silicone oil have a negative impact on the film-forming properties, and the optimal dosage is difficult to determine. Therefore, although the method of modifying polyurethane with organic silicon blending is convenient to operate, it has limitations. Therefore, it is difficult to achieve the expected modification effect using physical mixing methods. When performance requirements are high, organic silicon modified polyurethane can only be obtained through chemical methods.
Chemical Modification of Polyurethane
Chemical modification is to use the active functional group NCO on polyurethane to react with the active group on organic compounds to form a Covalent bond and introduce organic silicon into polyurethane molecules, so as to improve the heat resistance, cold resistance, hydrophobicity and biocompatibility of polyurethane materials. Its modification effect is much better than physical blending, and it is currently the most studied modification method. One of the main uses of light warp based silicone oil is to produce light warp based silicone oil. Light warp based silicone oil utilizes the reactivity of the tibial warp group to react with the functional groups (NCO) carried in the raw material during the synthesis of polyurethane, thereby introducing the polysiloxane chain segments into the corresponding resin structure. In addition, polysiloxane with active end group and compound or prepolymer of isoxanthate can be prepared into silicone modified polyurethane through addition polymerization and Chain reaction.
Synthesis method:
(1) The prepolymerization method involves adding a terminal isocarboxylate compound to the solvent, and then adding a polysiloxane oligomer under the protection of air to raise the temperature for a period of time. After adjusting the temperature, a chain extender dissolved in a polar solvent is added, and the reaction is kept warm for a period of time to complete.
(2) In the semi gel method, pretreated polyester glycol and double ended carbon are added into MDI under stirring and then treated with base silicone oil to prepare prepolymer at a certain temperature. The prepolymer is mixed with cross-linking agent. At room temperature, the slurry is in semi gel state, and then it is molded, heated, pressurized, and cured.
(3) Directly add the pre prepared polyimide (polyester) polyurethane prepolymer to the organosilicon oligomer gradually at a certain temperature, and control the temperature to complete the reaction.
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