Addition of thermo-plastic polyurethane (TPU) to poly(methyl methacrylate) (PMMA) to improve its impact strength and to change its scratch behavior

The effect of blending PMMA with TPU on both mechanical properties and scratch performance is studied. A higher TPU content leads to an enhanced impact strength and elongation at break but to a lower tensile strength and tensile modulus. PMMA tends to a brittle-ductile scratch behavior including cracks and material removal. Adding TPU changes the scratch behavior towards ductile ploughing without material removal. Fewer cracks occur within the scratch groove as the TPU content increases. The scratch walls show signs of ironing. However, the increasing TPU content also increases the opacity making it impossible to compare the scratch visibility of the blends to the neat material. There seems to be a good linear relation between the Charpy impact strength and the indentation depth of the PMMA/TPU blends. Similar to that, the Shore D hardness seems to linearly correlate to the indentation depth of the blends as well.