Effects of High-Temperature Storage on Waterborne Coatings
Effects of High-Temperature Storage on Waterborne Coatings
Waterborne paints use water as the dispersion medium, consisting of emulsions, resins, pigments and fillers, additives, neutralizing amines and preservatives. The recommended storage temperature ranges from 5 to 35°C. Long-term exposure to temperatures above 40°C under direct sunlight or in sealed high-temperature environments is strictly prohibited.
I. Destruction of System Stability
Emulsion Demulsification, Delamination and Caking
High temperatures accelerate the thermal motion of resin emulsion particles, causing desorption of the emulsifier adsorption layer and loss of hydrophilic protective effects. Resins agglomerate into coarse particles, forming distinct separate aqueous and paint layers that cannot be restored by stirring, rendering the product completely unusable.
Pigment Flocculation and Hard Sedimentation
High temperatures weaken the adsorption force of dispersants, leading to re-agglomeration of pigments such as titanium dioxide, iron oxide and carbon black. Density differences intensify sedimentation, forming hard compact sediment at the bottom that is extremely difficult to re-disperse, resulting in granular defects and orange peel textures during spraying.
Failure of Thickening Systems & Abnormal Viscosity
1. HEUR (Hydrophobically Modified Ethylene Oxide Urethane) associative thickeners undergo chain scission and degradation at high temperatures, causing a sharp overall viscosity drop.
2. ASE/HASE alkali-swellable thickeners suffer severe viscosity fluctuations under combined effects of high temperature and amine volatilization, triggering sagging during application and uneven roller coating.
II. Degradation of Additives & Comprehensive Deterioration of Coating Properties
Rapid Volatilization of Neutralizing Amines
Waterborne paints rely on triethylamine, AMP-95 and other substances to adjust the pH value to 7.5–9.0. In sealed high-temperature environments, massive escape of amines continuously lowers the pH. Exposed resin acid values trigger re-agglomeration of resins, destabilizing the system and simultaneously reducing water resistance and adhesion of the coating film.
Decomposition of Antiseptic and Mildew Inhibitors
Water-based biocides such as BIT and MIT have poor heat resistance and decompose rapidly at high temperatures. This leaves the paint highly susceptible to mildew, foul odors, and bulging barrels due to gas buildup.
Failure of Defoamers and Wetting Agents
Silicone and polyether defoamers easily delaminate and lose activity under high heat, drastically increasing the risk of bubbling, pinholes and craters during construction.
III. Accelerated Chemical Reactions & Degraded Coating Film Performance
Premature Micro-Crosslinking
Self-crosslinking acrylic and epoxy-modified waterborne resins undergo slow pre-crosslinking during high-temperature storage, generating tiny gel particles inside the paint that lead to fish eyes, particles and orange peel finishes after spraying.
Hydrolytic Aging
Ester linkages and polyurethane structures accelerate hydrolysis when exposed to water at high temperatures, ultimately causing significant declines in coating film hardness, boiling water resistance, salt spray resistance and weathering resistance.
IV. Potential Safety Hazards for Packaging
Inside sealed metal or plastic pails, vaporization of water and amines under heat raises internal pressure, leading to bulging barrels, lifted lids and leakage. In extreme cases, barrel deformation and cracking may occur.
V. Mitigation Measures & Storage Specifications
Optimal Storage Conditions
Store in cool, ventilated warehouses with temperatures ≤35°C. Avoid direct sunlight and proximity to boilers or heating equipment; do not stack outdoors during summer.
Treatment for Paint Deteriorated by High Temperatures
• Minor delamination: Test fineness and viscosity after low-speed stirring.
• Hard caking, foul odor or severe gelation: Discard the product immediately; it cannot be used further.
Emergency Handling for Short-Term High-Temperature Exposure
1. Open the container slightly to vent and cool down the material.
2. Add AMP-95 promptly to readjust the pH value.
3. Supplement a small amount of dispersant, then conduct a small-scale spray test to verify performance.
VI. Summary
1. Slight short-term high-temperature exposure: Viscosity fluctuations and mild sedimentation.
2. Long-term storage above 40°C: Demulsification and delamination, gel caking, mildew and odor, pH collapse, plus complete failure of coating film adhesion and water resistance.
Image Caption Translation
1. Gel caking
2. Demulsification & delamination
3. Poor coating film adhesion
