Decomposition Rate Constant
At a given temperature, the polymerization rate of monomers largely depends on the decomposition rate Rd of the initiator, which is directly proportional to the first power of the initiator concentration . Ethyl acetate significantly promotes the decomposition reaction of persulfate, with its decomposition rate constant increasing from 0.248 h⁻¹ to 2.08 h⁻¹ at 80 °C. Methanol also has a significant impact on the decomposition of persulfate; at a methanol concentration of 1 mol/L, the decomposition rate increases by 25 times. Sodium dodecyl sulfate, an emulsifier, also significantly promotes the decomposition of persulfate.
Active Oxygen Content
Active oxygen content, also known as effective oxygen content, represents the number of free radicals generated after the decomposition of a certain mass of peroxide.
Critical Temperature
This refers to the lowest temperature at which a peroxide decomposes to generate free radicals. The critical temperature differs slightly from the decomposition temperature, which is the temperature at which the half-life of the peroxide is 10 h (or 1 min). The critical temperatures of peroxides used as initiators are mostly between 60 and 130 °C. If the temperature is below 60 °C, room temperature is very unstable, making them unsuitable as initiators. Half-life: Half-life refers to the time required for an initiator to decompose to half its initial concentration at a given temperature. It is used to measure the activity of the initiator or the reaction rate. For example, at 60°C, the decomposition temperature of an initiator with a half-life of 10 hours in a solvent (benzene or toluene) is usually called the decomposition temperature of the initiator.
Activation Energ
Activation energy (Ed) is an important factor determining the decomposition rate of an initiator and can be obtained using the Arrhenius empirical formula. A higher activation energy means the initiator is less prone to decomposition but more stable; a lower activation energy means it decomposes more easily, generating free radicals.
The decomposition rate constant, half-life, and decomposition activation energy of an initiator can serve as a basis for selecting initiators, polymerization temperatures, and production cycles.
