Micro mar resistance

Measurement of Depth of Indentation. To calculate the micro mar resistance and the different responses of the coating to marring stresses, the dimension of the... 

Micro Mar Resistance Fn/ Atrgh Elastic Recovery ( Aind - Adit) / Aind %... 

Figure 5. Schematic illustration of how to calculate micro mar resistance (MMR) and how to calculate different responses of the coating to marring stress.

Table I. Micro Indentation Hardness (MIH), Micro Mar Resistance (MMR), and Responses to Marring Stress of Three Coatings at 126ttN...

There may be other ways to evaluate plastic resistance of coatings based on the data of micro-scratch experiment. Nevertheless, mar resistance can be evaluated or ranked mechanistically and objectively with the area under the plastic deformation curve and the critical normal force before fracture. 

Mar resistance of polymeric coatings depends on a number of factors, such as chemical components, molecular weight, crosslink material and its density, additives, processing procedure, etc. In addition, the tribological properties of coatings vary with the depth and age. A scratching test performed at the top surface at nano scale does not necessarily represent the performance in marring test at micro and submicron scales. An intensive study is needed before any conclusive statement can be made. 

JL Courier, EA Kamenetzky. Micro- and nano-indentation and scratching for evaluating the mar resistance of automotive clearcoats. Eur Coatings J 1999(7/8) 3-38, 1999. 

Figure 9 Influence of Grain Depth and Micro Roughness on Mar Resistance...

Use Level 0.5-2.0% (mar/abrasion resist.), 2-5% (matting agent) Micropro 400 [Micro Powders]... 

---