Calorimetric Method To Determine Self-Accelerating Polymerization Temperature (SAPT) for Monomer Transportation Regulation: A Heat Balance Approach

In our previous paper, kinetic parameters for the thermal polymerization of methyl methacrylate (MMA) inhibited with 4-methoxyphenol (MEHQ) were determined by isothermal and nonisothermal calorimetric tests. In this paper, the Self-Accelerating Polymerization Temperature (SAPT) was determined based on the heat balance using measured or estimated heat transfer coefficients and the aforementioned kinetic parameters. Herein both the PIT approach and heat balance approach are validated for MMA inhibited with MEHQ in a 1 gallon container, at conditions where the monomer in the container self-increases its temperature from 2°C lower to 6°C higher than the environmental temperature in a period of 7 days (H1 method). Various experimental and computational methods for determining the heat transfer coefficients for these tests are described. A screening method for SAPT based on PIT (Polymerization Induction Time) was proposed, as follows: for monomers having a well-defined PIT at 75°C greater than 7 days with the max heat generation rate much lower than 120 μW/g, their SAPT can be reported as >75 °C. Otherwise, additional testing is needed and SAPT can be estimated based on either the PIT approach or heat balance approach.