Polyhexamethylene Guanidine Hydrochloride (PHMG)

Polyhexamethylene Guanidine Hydrochloride (PHMG) – Broad-Spectrum Polymeric Biocide for Disinfection and Water Treatment

Chemical Structure and Synthesis
Polyhexamethylene guanidine hydrochloride (PHMG) is a cationic polymeric compound belonging to the guanidine family. Its structure consists of repeating hexamethylene units linked by guanidine groups, forming a high-molecular-weight polymer. The synthesis is typically carried out by polycondensation of hexamethylenediamine and guanidine hydrochloride in an acidic medium, yielding a water-soluble, non-volatile, and non-corrosive product.

Mechanism of Action
PHMG exerts its antimicrobial effect through a dual mechanism. The positively charged guanidine groups electrostatically adsorb to negatively charged microbial cell surfaces (bacteria, fungi, viruses), disrupting membrane integrity. This leads to inhibition of intracellular lipid synthesis, leakage of cytoplasmic components, and ultimately cell death. The polymer also inhibits respiration and impairs energy production in microbial cells. PHMG exhibits broad-spectrum activity against Gram-positive and Gram-negative bacteria, fungi, and viruses, with minimum inhibitory concentrations (MIC) as low as 32 µg/mL. Notably, PHMG does not induce microbial resistance.

Key Properties

• High water solubility: Easily dissolves in water, forming clear, colorless, and odorless solutions.

• Broad-spectrum antimicrobial activity: Effective against bacteria, fungi, viruses, and algae.

• Low toxicity: Non-toxic, non-irritating, and free from chlorine, iodine, mercury, aldehydes, phenols, and heavy metals.

• Stability: Maintains activity across a wide temperature and pH range; activity is enhanced in alkaline conditions.

• Biodegradable: Environmentally friendly and breaks down naturally.

• No foaming: Does not produce foam during use.

Applications

• Disinfectants and sanitizers: Active ingredient in surface disinfectants, hand sanitizers, and antiseptic solutions for healthcare, veterinary, and household use.

• Water treatment: Used as a biocide in cooling water systems, swimming pools, and industrial water treatment to control microbial growth.

• Personal care and hygiene: Incorporated into wet wipes, mouthwashes, and topical antimicrobial products.

• Textile and materials: Applied as an antimicrobial finish for textiles, non-leaching coatings, and polymer composites.

• Agriculture: Used in plant protection and crop preservation.

• Food industry: Employed in food contact surface sanitation and preservation.

Recommended Use
Typical concentrations range from 0.01% to 2.0% depending on the application. For disinfection of surfaces and water treatment, concentrations of 0.01–0.1% are commonly effective. Avoid combining with anionic surfactants, which may precipitate the polymer. High organic loads may reduce efficacy.

Safety and Handling
PHMG is considered safe for use at recommended concentrations. It is non-irritating to skin and mucous membranes. However, as with all biocides, appropriate personal protective equipment (gloves, safety goggles) should be used when handling concentrated solutions. Store in a cool, dry place, away from strong oxidizers.

Quality Assurance
Each batch is tested for molecular weight, purity, and antimicrobial efficacy to ensure consistent performance. Typical molecular weight ranges from 2,000 to 3,000 Da.