The effect of plasticization by fatty acid amides on the scratch resistance of PMMA

Scratch durability of polymer surfaces is becoming crucial for the growing use of these materials in innovative applications, replacing former materials with more resistant surfaces. A variety of physico-chemical processes such as annealing and a range of ion plantation techniques, generally applied to improve surface properties, cannot be applied to transparent polymers like PMMA due to their darkening outcome. Enhancement of the scratch resistance must be investigated for the most part as a consequence due to decreasing the friction coefficient. The recovery of the groove left on the surface increases if the tip is smooth or if the local friction coefficient is low. The effect of three fatty acid amides namely Erucamide, Behenamide and Stearamide on both surface and bulk mechanical properties of PMMA was studied at a wide range of temperature. Experimental results show that a decrease in friction coefficient is possible by the introduction of appropriate plasticizer without having a significant effect on its bulk behaviour and this decrease in friction depends upon the nature and the content of plasticizer. Moreover, Erucamide has been proved more effective in decreasing friction of PMMA than Behenamide or Stearamide. The values of the rear contact angle and in situ photographs during scratching confirm that the decrease in friction is associated with the decrease of yielding of the contact between the tip and the polymer surface. The surface energy analysis shows that the decrease in friction coefficient is without any significant change in surface energy of PMMA.

► The effect of Erucamide, Behenamide and Stearamide on both surface and the bulk properties of PMMA was studied.
► Fatty acid amides are found to be efficient for improving scratch resistance only in presence of very small amounts.
► Erucamide has been proved more effective than either Behenamide or Stearamide.
► Scratch resistance is improved by lowering the friction coefficient and in turn by modifying the nature of the contact.
► Friction coefficient is reduced by enhancing the vicoelasticity in the contact.