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Blooming, the unsightly white haze on rubber boots, is caused by the migration and surface crystallization of excess compounding ingredients, primarily sulfur or zinc stearate.

Causes Analysis:

1. Improper Vulcanization: Under-curing or incorrect curing temperatures prevent sulfur from fully reacting, leaving excess that migrates out.

2. Compound Formulation: Using excessive amounts of sulfur or zinc stearate beyond the rubber's solubility limit is a primary cause.

3. Storage Conditions: Storing uncured or cured products in high humidity and low temperatures can accelerate ingredient migration.

Prevention & Solutions:

1. Optimize Formulation: Precisely control the sulfur-to-accelerator ratio and use insoluble sulfur where possible. Consider the solubility limits of all additives.

2. Refine Vulcanization: Ensure optimal curing time, temperature, and pressure for a complete crosslink reaction.

3. Post-production Handling: Implement a controlled cooling process after curing and store finished products in stable, dry conditions.

By addressing the formulation, curing process, and storage, blooming can be effectively minimized, ensuring a high-quality product surface.