Fractography of poly(methyl methacrylates)

Area of Science:

• Materials Science
• Polymer Science
• Biomaterials Engineering

Background:

• Clinical prostheses are often fabricated from poly(methyl methacrylate) (PMMA) using powder and monomer mixtures.
• Polymerization of these mixtures results in a two-phase material with PMMA grains dispersed in a PMMA matrix.
• The mechanical properties of these two-phase PMMA materials are often inferior to single-phase polymers.

Purpose of the Study:

• To evaluate the failure mechanisms of two-phase PMMA materials.
• To correlate microscopic fracture surface features with material properties.
• To understand the influence of molecular weight on the fractography of PMMA.

Main Methods:

• Microscopical examination of fracture surfaces of two-phase PMMA materials.
• Distinguishing between transgranular and intergranular fracture modes.
• Controlled degradation of single-phase PMMA using gamma irradiation to study molecular weight effects.
• Analysis of periodic rib markings on fracture surfaces to estimate molecular weight.

Main Results:

• A distinct granular microstructure was observed in the two-phase PMMA.
• Materials exhibited either purely transgranular fracture or a combination of transgranular and intergranular fracture.
• A relationship was established between the spacing of rib markings and molecular weight in single-phase PMMA.
• This relationship was applied to estimate the molecular weight of the PMMA matrix in two-phase materials.

Conclusions:

• Microscopic examination of fracture surfaces is crucial for understanding the failure of two-phase PMMA.
• The presence of intergranular fracture indicates a potential weakness in the material.
• The established fractographic method allows for the estimation of molecular weight in the complex matrix of two-phase PMMA, aiding in material characterization and improvement.