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The application of refinish products over original equipment manufacturer (OEM) finishes is a common practice in automotive and industrial maintenance, but requires careful consideration of compatibility, adhesion, and long-term performance. This article examines the technical factors involved in such applications, using diethylene glycol methyl ether (DGME) as a key solvent example and comparing solvent oil properties to illustrate formulation considerations.
| Factor | OEM Finish Characteristic | Refinish Requirement | Potential Issue |
|---|---|---|---|
| Chemical Composition | Typically polyurethane or acrylic | Must have compatible resin system | Delamination if incompatible |
| Surface Energy | High (38-42 dynes/cm) | Proper wetting required | Poor adhesion if mismatch |
| Cure Mechanism | Often thermally cured | Air-dry or low-bake preferred | Under-cure problems |
| Film Thickness | 25-50 microns | Additional 30-60 microns typical | Stress cracking risk |
Diethylene glycol methyl ether (DGME) serves as an effective coalescing solvent in refinish products due to:
High boiling point (194°C) for proper film formation
Balanced hydrophilic/lipophilic character
Effective plasticization of acrylic and polyurethane resins
| Parameter | DGME | Light Naphtha | Heavy Naphtha |
|---|---|---|---|
| Evaporation Rate (n-BuAc=1) | 0.03 | 1.4 | 0.2 |
| Flash Point (°C) | 85 | -7 | 38 |
| Hydrogen Bonding | Strong | Weak | Moderate |
| Resin Compatibility | Broad | Limited | Moderate |
| VOC Content (g/l) | 850 | 750 | 780 |
Degrease with compatible solvent (DGME-based cleaners effective)
Mechanical abrasion (400-600 grit recommended)
Proper flash-off time between coats
Ideal application at 20-25°C, 50-70% RH
DGME's low volatility helps prevent blushing
Force drying at 60-80°C acceptable with DGME formulations
Full cure typically 24-48 hours at ambient
Technical Advantages of DGME in Refinish Systems
Enables viscosity reduction without compromising flow
Reduces surface tension (28 dynes/cm) for better wetting
Acts as coupling agent for waterborne systems
Minimizes solvent popping in high-build applications
Refinish products can be successfully applied over OEM finishes when proper formulation and application protocols are followed. Solvents like diethylene glycol methyl ether provide critical performance benefits in these systems, particularly in achieving proper adhesion without damaging the original coating. The selection of appropriate solvents and understanding their interaction with both OEM and refinish materials remains essential for durable, high-quality results.
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