Synthesis process of polymethyl methacrylate

In the synthesis process of polymethyl methacrylate, free radical polymerization is a commonly used method, and the selection of initiators is crucial. Benzoyl peroxide (BPO) can effectively initiate polymerization reactions at 60-80 ℃, and the free radicals generated by its decomposition can promote the rapid connection of methyl methacrylate monomers into polymer chains.
In the solution polymerization process, the properties of the solvent have a significant impact on the synthesis of polymethyl methacrylate. For example, using toluene as a solvent can effectively dissolve monomers and polymers, with a boiling point of 1
6 ℃ and good stability within the polymerization reaction temperature range, which helps to control the viscosity of the reaction system. When preparing polymethyl methacrylate by bulk polymerization, the viscosity of the system is low at the initial stage of the reaction. When the monomer conversion is about 10% -20%, the reaction rate will automatically accelerate, which is the gel effect. This effect makes it difficult to control the reaction temperature and requires reasonable arrangements for heat dissipation measures. In the suspension polymerization process, the type and amount of dispersant will affect the size and morphology of polymer particles. If polyvinyl alcohol is used as a dispersant, at a concentration of 0.1% -0.5%, the particle size distribution of polymethyl methacrylate particles can be between 0.1-1mm, and the particles are relatively uniform. Emulsifier plays a key role in the synthesis of polymethyl methacrylate by lotion polymerization. With sodium dodecyl sulfate as the emulsifier, the monomer can be dispersed into small droplets at a proper concentration to form a stable lotion system. Polymerization can be carried out in these droplets to prepare polymer latex particles with a particle size of 50-150 nm.
The addition of chain transfer agents during the synthesis of polymethyl methacrylate can effectively control the molecular weight of the polymer. For example, using n-dodecanethiol as a chain transfer agent with an addition amount between 0.1% and 1% can adjust the molecular weight of polymethyl methacrylate to tens of thousands to hundreds of thousands. The reaction temperature is one of the key parameters in the synthesis process of polymethyl methacrylate. In free radical solution polymerization, the reaction temperature is generally controlled at 70-90 ℃. If the temperature is too high, it may cause thermal degradation of the polymer, while if it is too low, the reaction rate will be too slow, affecting production efficiency. The pressure of polymerization reaction can also affect the synthesis of polymethyl methacrylate. In some special synthesis processes, appropriately increasing the reaction pressure to 2-5 MPa can increase the concentration of monomers, thereby accelerating the reaction rate and improving the yield of polymers. The purity of monomers is crucial in the synthesis of polymethyl methacrylate. The purity of methyl methacrylate monomer needs to reach over 99%. The presence of impurities may affect the activity of initiators, leading to abnormal polymerization reactions or deterioration of polymer properties.
The post-treatment process cannot be ignored for improving the performance of polymethyl methacrylate. For example, through steps such as precipitation, filtration, washing, and drying, impurities such as unreacted monomers and initiator residues can be removed, improving the purity and stability of the polymer.