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Waterborne acrylic sealing sealant belongs to a high solid content paste system, with core requirements: stable consistency without opening the tank, smooth extrusion, no sagging during construction, smooth surface after molding, no water stratification during long-term storage, no hardening at low temperatures, and no thinning at high temperatures. Rheological additives (thickeners) are key to regulating the thixotropy and recovery of paste. Commonly used categories include cellulose ether (HEMC/HEC), HEUR bound polyurethane thickeners, alkali swelling thickeners HASE/ASE, organic bentonite, and gas-phase silica. Different additives directly affect the construction and durability of finished products.

The type of auxiliary agent represents the recommended addition amount of the product (based on the total formula), with core advantages, main shortcomings, and adaptation scenarios

HEMC modified with methyl hydroxyethyl cellulose has a viscosity of 0.3%~0.8% and excellent water retention. It provides a basic low shear viscosity, resistance to water separation, improves paste shaping, and has better salt stability than HEC. The increase in high shear viscosity is limited, and excessive use can easily cause surface wrinkling and a decrease in water resistance. It is commonly used as acrylic joint filler and exterior wall elastic joint filler

HEC hydroxyethyl cellulose non-ionic HEC 0.25%~0.7%, high thickening efficiency, low cost, electrolyte sensitive, easy to be affected by lotion and powder, viscosity attenuation, mold proof pressure, high interior wall economic joint filler

HEUR associative polyurethane thickener hydrophobic modified polyurethane 0.2%~0.6% improves medium to high shear viscosity, with smooth extrusion feel, good leveling, and no significant impact on water resistance; Thixotropic recovery is controllable. When used alone, it has insufficient low shear viscosity, is prone to water separation, and competes with surfactants for compatibility. It is a high-end joint filler with high elasticity, high gloss, and low odor, and has an export system

HASE hydrophobic modified alkali swelling, acrylic anion alkali swelling 0.3%~0.7%, strong thixotropy, anti sagging, moderate cost, synergistic effect with HEUR, strong pH dependence (requiring 8-9.5), weak water resistance, universal sealant for interior walls that reduces viscosity when encountering electrolytes, not recommended for long-term immersion scenarios

ASE ordinary alkali swelling thickener, anionic alkali swelling 0.4%~0.8%, good anti sagging, high cost-effectiveness, slow thixotropic recovery, poor water resistance, large low-temperature viscosity fluctuations, low-end economical formula

Organic bentonite (rheological soil) Water modified bentonite 0.5%~1.2% Strong thixotropy, anti settling, anti sagging, not affected by pH, stable storage at high temperature, dry and hard paste added, high extrusion resistance, easy to pill, high powder, high filling and sealing sealant

Gaseous silica hydrophilic/hydrophobic 0.15%~0.4% thickening enhances bonding strength and weather resistance, with fast recovery of thixotropy and high dispersion difficulty, high cost, and excessive use can easily cause matte and rough polishing of high-end weather resistant exterior wall sealant

3、 Classic compounding solution (commonly used for acrylic sealant)

Compound logic: low shear anti water separation (cellulose/bentonite)+medium shear anti sagging (HASE)+high shear smooth extrusion (HEUR)

Economic interior wall formula: HEC0.4%+HASE0.4% Features: Low cost, decent resistance to sagging; Shortcoming: Poor water resistance, high risk of viscosity decline during long-term storage

Universal exterior wall standard formula: HEMC0.4%+HASE0.3%+HEUR 0.25% Features: balanced water retention, extrusion feel, storage stability, mainstream mature solutions in the market

High end export elastic joint filler: HEMC0.3%+HEUR 0.4%+organic bentonite 0.5% Features: excellent thixotropic recovery, stable high/low temperature storage, better water and weather resistance, low VOC

High filling heavy joint filler: Organic bentonite 0.8%+HEMC0.3% Features: Significant anti powder settling, anti sagging, suitable for high calcium powder and talc powder systems

4、 Key points of production addition process (key points for avoiding pitfalls)

1. Cellulose ether: pre swell, disperse with cold water, mix well before adding lotion to avoid agglomeration; Can be paired with a small amount of ethylene glycol anti agglomeration dry powder

2. HEUR polyurethane thickener: Thickening in the later stage (after feeding or before discharging) to avoid high shear damage to the binding network in the early stage, and direct dry powder addition is prohibited

3. HASE/ASE: Neutralize the system to the target pH before adding, and there is almost no thickening effect in acidic environments

4. Organic Bentonite: Pre dispersed pulping and high-speed shear activation are required, otherwise particles and lumps are prone to occur

5. Compatibility taboos: High content dispersants and wetting agents will seize the hydrophobic groups of HEUR, causing a decrease in viscosity and water separation; The formula needs to control the total amount of surfactant used

5、 Common causes and optimization solutions for rheological faults

1. Open the tank to dilute and store water separately

Reason: Insufficient low shear thickening, HEUR used alone, insufficient cellulose addition; Electrolyte exceeding the standard

Solution: Supplement HEMC/organic bentonite, reduce free surfactants, and use cellulose+HEUR compound

2. Squeezing is laborious, and the paste is dry and hard

Reason: Excessive cellulose and bentonite, strong thixotropy

Solution: Reduce the dosage of inorganic rheological soil and increase a small amount of HEUR to improve lubrication and extrusion properties

3. Construction flow hanging, poor facade forming

Reason: Slow recovery of thixotropy, insufficient HASE/bentonite, high shear viscosity

Solution: Supplement HASE or bentonite, adjust HEUR ratio, optimize thixotropic recovery rate

4. Slow surface drying, cracking and wrinkling after molding

Reason: Excessive addition of cellulose and high water retention

Solution: Reduce the dosage of 4HEMC/HEC and adjust the drying rate with film-forming agents

5. Significant viscosity fluctuations after cold and hot cycles

Reason: Single alkali swelling system, sensitive to temperature and electrolyte

Solution: Introduce HEMC+HEUR compound to reduce the use of ASE alone