The synthesis of polyvinyl alcohol PVA from vinyl acetate monomer VAM involves two main steps: polymerization of VAM to polyvinyl acetate PVAc and hydrolysis of PVAc to PVA.1. Polymerization of VAM to PVAc:The polymerization of VAM is typically carried out using free-radical initiators, such as azo compounds or peroxides, in a solution or suspension polymerization process. The optimum reaction conditions for this step are as follows:- Temperature: The reaction temperature is usually in the range of 50-80C. Higher temperatures can lead to faster reaction rates but may also result in increased side reactions and lower molecular weight polymers.- Concentration of catalyst: The initiator concentration is typically in the range of 0.1-1 wt% relative to the VAM. Higher initiator concentrations can lead to faster reaction rates but may also result in lower molecular weight polymers.- Reaction time: The reaction time depends on the desired degree of polymerization and can range from a few hours to several days. Longer reaction times can lead to higher molecular weight polymers.2. Hydrolysis of PVAc to PVA:The hydrolysis of PVAc to PVA is typically carried out using an alkaline catalyst, such as sodium hydroxide NaOH or potassium hydroxide KOH , in an aqueous solution. The optimum reaction conditions for this step are as follows:- Temperature: The hydrolysis temperature is usually in the range of 60-90C. Higher temperatures can lead to faster hydrolysis rates but may also result in increased side reactions and lower molecular weight polymers.- Concentration of catalyst: The alkaline catalyst concentration is typically in the range of 1-5 wt% relative to the PVAc. Higher catalyst concentrations can lead to faster hydrolysis rates but may also result in increased side reactions and lower molecular weight polymers.- Reaction time: The hydrolysis time depends on the desired degree of hydrolysis and can range from a few hours to several days. Longer hydrolysis times can lead to higher degrees of hydrolysis and more complete conversion of PVAc to PVA.The properties of the resulting PVA polymer, such as molecular weight, degree of hydrolysis, and crystallinity, can be affected by the reaction conditions in both steps. For example, higher reaction temperatures and initiator concentrations in the polymerization step can lead to lower molecular weight polymers, while longer reaction times can result in higher molecular weight polymers. Similarly, higher hydrolysis temperatures and catalyst concentrations can lead to higher degrees of hydrolysis and more complete conversion of PVAc to PVA, while longer hydrolysis times can result in more crystalline PVA polymers with improved mechanical properties.