Analysis of the Application of Preservatives in Acrylic Waterproof Adhesive
I. Microbial Contamination Risk and Anti-corrosion Necessity of Acrylic Waterproof Adhesive
Acrylic waterproof adhesive takes acrylate polymer as its core component. Its high water content (usually over 50%) and abundant organic matter (such as plasticizers and fillers) provide an ideal growth environment for microorganisms. Microbial contamination can lead to the following problems:
Performance deterioration: Mold decomposes the polymer chains, damaging the flexibility and adhesion of the waterproof adhesive, causing cracks and peeling in the coating.
Sensory abnormality: Bacterial metabolism produces odorous substances such as hydrogen sulfide and ammonia, causing the waterproof glue to stink.
Safety risk: Certain microorganisms (such as Aspergillus Niger) may release toxins that contaminate the building materials or the environment they come into contact with.
Typical case: In a certain construction project, after using acrylic waterproof adhesive without preservatives, mold spots appeared on the bathroom walls within three months, the coating bonding strength decreased by 40%, and the rework cost increased by 25%.
Ii. Mechanism of Action and Selection Principles of Preservatives in Acrylic Waterproof Adhesives
1. Mechanism of action
Disrupting cell structure: For instance, isothiazolinone preservatives penetrate the cell membranes of microorganisms, interfere with enzyme systems, and lead to metabolic arrest;
Inhibiting energy synthesis: Acid-type preservatives such as sodium benzoate lower the pH value and inhibit the ATP synthesis of microorganisms.
Blocking DNA replication: Kathon preservatives bind to microbial DNA, preventing its replication and reproduction.
2. Selection principles
Compatibility: It should have no chemical reaction with acrylic polymers and fillers (such as calcium carbonate, talcum powder) to avoid affecting the flexibility and weather resistance of the waterproof adhesive.
Broad-spectrum property: It has inhibitory effects on bacteria (such as Escherichia coli), molds (such as Aspergillus Niger), and yeasts (such as Candida albicans).
Long-term effectiveness: It continuously functions throughout the service life of the waterproof adhesive (typically 5 to 10 years), resisting the challenges of repeated damp environments.
Environmental friendliness: Complies with regulations such as REACH and RoHS, and avoids the use of harmful substances like formaldehyde and heavy metals.
Recommended types of preservatives
BIT (1, 2-benzoisothiazolin-3-one) : Broad-spectrum and highly efficient, heat-resistant (able to withstand a processing temperature of 80℃), suitable for high-solid-content acrylic waterproof adhesives;
CMIT/MIT (methylchloroisothiazolinone/methylisothiazolinone) : Low cost, but the dosage needs to be controlled (≤15ppm) to avoid skin allergies.
Organic acids (such as benzoic acid, sorbic acid) : Suitable for acidic systems with a pH value of ≤5, compatible with the acidic environment of acrylic adhesives
