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Methyl methacrylate monomer-polymer equilibrium in solid polymer
1Dental Materials Science, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Victoria, Hong Kong.
Summary
Minimizing residual methyl methacrylate (MMA) in poly(methyl methacrylate) (PMMA) dental materials is crucial. This study maps MMA concentration over time and temperature to find optimal processing conditions, reducing irritancy and improving properties.
Area of Science:
- Polymer Chemistry
- Materials Science
- Biomaterials Engineering
Background:
- Poly(methyl methacrylate) (PMMA) is widely used in dentistry.
- Thermal polymerization of methyl methacrylate (MMA) is a common processing method.
- Residual MMA monomer is a concern due to its irritant properties.
Purpose of the Study:
- To investigate the concentration of residual MMA over time and temperature.
- To identify optimal processing conditions for PMMA to minimize residual MMA.
- To improve the safety and mechanical properties of acrylic denture bases.
Main Methods:
- Incubation of PMMA powders with and without MMA at temperatures ranging from 10-170°C for 1-384 hours.
- Quantification of residual MMA concentration using Gas Chromatography (GC).
- Fitting a response surface model to [MMA] versus log(time) and reciprocal temperature.
Main Results:
- Equilibrium concentration of MMA was reached around 100 hours for plain PMMA.
- A quadratic fit better described the equilibrium data of log[MMA] versus 1/T.
- An 'overshoot' phenomenon in the equilibration process was observed and attributed to an intermediate.
Conclusions:
- Minimizing residual MMA is vital for mechanical properties and reducing irritancy in denture bases.
- The developed response surface model enables direct identification of optimal processing conditions.
- Understanding MMA-PMMA interactions under varying conditions enhances material safety and performance.