Introduction: Paint seeding (also known as graining) is a common storage defect manifesting as coarse particles in paint, including slight skinning, gelation, agglomerates, or foreign particles. This phenomenon is particularly common in chlorinated rubber mastic coatings and asphalt coatings, affecting not only film appearance but also potentially clogging spraying equipment. This article systematically analyzes the causes of seeding and provides complete solutions from production sources to usage handling.
What is Paint Seeding?
- Granular protrusions and coarsened paint particles after opening
- Common coarse particle types: slight skinning, gelation, agglomerates, or foreign particles
- High-risk systems: Chlorinated rubber mastic coatings, asphalt coatings
- Consequences: Affects film appearance, clogs spraying nozzles
Common Causes of Paint Seeding
- Improper Temperature Control:
- Production temperature of mastic coatings exceeding 40℃, causing pigment particle rheological precipitation
- Moisture Effects:
- Moisture ingress during production or storage, causing pigment particle aggregation
- Excessive moisture in pigments and fillers, forming non-dispersible clumps when hand-squeezed
- Raw Materials and Process:
- Overly coarse pigments, failing particle fineness standards
- Contaminated containers or introduction of finely broken skin
- Insufficient grinding time and process
- Chemical Reactions:
- Reactions between certain resins and pigments, causing pigment particle coagulation and precipitation
Solutions to Prevent and Fix Paint Seeding
- Temperature Control:
- Mastic coatings at 35-40℃ require cooling before use
- Return to factory for regrinding if coarse particles persist
- Moisture Prevention:
- Avoid adding moisture-containing solvents during production
- Avoid production in high humidity conditions
- Ensure dry pigments and fillers; dry or sun-dry if excessive moisture
- Production Process Optimization:
- Appropriately extend grinding time and process
- Strictly control particle fineness of pigments and fillers
- Add suitable polymerization inhibitors to prevent thickening under temperature extremes
- Problem Product Treatment:
- Slight seeding: Thoroughly stir then filter through 80-mesh or finer sieve
- Severe seeding: Return to factory for regrinding
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