Spreading Behavior and Morphology of Ethylene Methacrylic Acid (EMAA) Deposits via the Flame Spray Process

Abstract

Abstract:A single splat is the building block of a thermal spray coating; thus, investigating single splats is essential to understanding thermal spray coatings and their properties. In this study, the spreading behavior and the morphology of flame sprayed ethylene methacrylic acid (EMAA) splats, deposited at various stand-off distances (SODs) onto glass and mild steel substrates were investigated using optical microscopy, back scattered scanning electron microscopy and secondary electron scanning electron microscopy. The results of this study indicate that the spread factor increases with an increase in the stand-off distance up to 30 cm for glass and 25 cm for steel substrates. Further increase of the stand-off distance results in a decreased spread factor. The aspect ratio of EMAA single splats on both glass and mild steel substrates decreases with increased stand-off distances, indicating that more circular shapes occur at higher stand-off distances. On mild steel substrates, the minimum unevenness ratio (η) occurs at 35 cm SOD. The unevenness ratio (η) on glass substrates decreases from 1.9 (at 20 cm SOD) to 1.77 (at 25 cm SOD), and from 1.8 (at 30 cm SOD) to 1.3 (at 35 cm SOD). The lowest unevenness ratio (η) is found at 35 cm SOD. The highest unevenness ratio (η) is at 25 cm SOD. This paper discusses the effect of surface chemistry on the underside of an EMAA single splat morphology. It includes Raman spectrum analysis of EMAA and the X-ray diffraction of the EMAA powder. This work analyses the splat morphology and classifies the taxonomy of single splats of EMAA.

Ethylene Methacrylic Acid (EMAA) Single Splat Morphology

“…The prime five morphologies of splats [25]; i.e., (i) semi-molten splats; (ii) re-solidified splats; (iii) disc splats; (iv) splashed splats; (v) fragmented splashes, are modeled position on the temperature vs. velocity map. The semi-molten splats and re-solidified splats arose at lower temperatures and velocities, which corresponded to SOD shorter than 25 cm and SOD longer than 30 cm, respectively.…”

“…The EMAA, purchased from Innotek Powder Coatings LLC (TX-USA), exhibited a particle size range from 30 µm to 400 µm and an angular morphology, as expected from the cryogenic grinding process used to manufacture the powders [25].…”

Analysis of EMAA Splats on Glass and Mild Steel Substrates

“…In general, increasing SOD to 35 cm results in the formation of disk-shaped splats. A higher percentage of the splash morphology was observed on mild steel substrates than glass substrates (Ref 23,26,27). It is suggested that more rapid freezing occurs on mild steel than on glass substrates due to the higher thermal conductivity of the steel (Ref 28).…”

Wetting, Solubility and Chemical Characteristics of Plasma-Polymerized 1-Isopropyl-4-Methyl-1,4-Cyclohexadiene Thin Films

“…The chemical composition of the surface determines its surface energy: whereas surfaces rich in non-polar groups (e.g., -CH x , with x = 1-3) have low surface energies and, thus, are hydrophobic, surfaces with a high density of polar groups (e.g., -OH or -C=O) exhibit high surface energies and are hydrophilic [13]. With regard to surface topography, an increase in the surface roughness enhances the surface hydrophilicity of hydrophilic materials and hydrophobicity in the case of hydrophobic surfaces [14]. The micro-and nano-scale variations in the slope on the surface are believed to create physical barriers that directly affect the motion of the contact line, thus affecting CAs observed at the macro scale.…”