Definition of Solids Content
Solids content (also known as non-volatile content) refers to the percentage of residue remaining after a paint sample is heated and baked under specified temperature conditions, expressed as a ratio of the residue mass to the original sample mass.
-
Too low solids content may lead to thin films, reduced throwing power, and degraded coating stability.
-
Too high solids content may cause orange peel on the electrophoretic film and increased paint carryout loss.
Therefore, controlling solids content in the electrophoretic bath is a critical parameter in production line management.
Materials and Equipment
-
Analytical balance (sensitivity: 0.0001 g)
-
Electric forced-air drying oven
-
Disposable pipette
-
Aluminum weighing dish
Test Procedure
-
Weigh a clean, dry aluminum dish and record its mass as M₁ using the analytical balance.
-
Add a known amount of the test sample to the dish and weigh the total (M₂). Place it in the forced-air oven at 120°C for 1 hour (start timing when temperature reaches 120°C), or use agreed-upon conditions.
-
Cool under dry conditions and reweigh (M₃). Calculate solids content using the formula:
Results are taken as the average of two parallel tests. The relative deviation between parallel measurements should not exceed 3% (or agreed limit). If it does, retest.
Experimental Results
(Result comparison chart omitted as not provided)
Experimental Conclusions
Based on the test results and comparison chart under different conditions for electrophoretic bath liquid:
1. When sample and equipment are consistent, the following conditions show small deviations (relative deviation within 7% of Condition 2 baseline):
-
(105 ± 2)°C / 3 h
-
(120 ± 2)°C / 1 h
-
(120 ± 2)°C / 2 h
-
(180 ± 2)°C / 0.5 h
→ All are valid for daily solids content monitoring on electrophoretic coating lines.
→ For time-constrained scenarios, (180 ± 2)°C / 0.5 h can replace (120 ± 2)°C / 1 h.
2. The following conditions show larger deviations (significantly higher than other conditions, based on Condition 2):
-
(150 ± 2)°C / 1 h
-
(150 ± 2)°C / 0.5 h
-
(125 ± 2)°C / 1 h
→ Not recommended for routine solids content maintenance in electrophoretic production.
3. Between (150 ± 2)°C / 1 h and (150 ± 2)°C / 0.5 h, deviations are small (within 7% of Condition 4 baseline).
→ Both are acceptable if testing under these conditions is required.