Preparation and characterization of a permanently antimicrobial polymeric material by covalent bonding

A permanently antimicrobial polypropylene (PP-g-PHMG) was obtained by covalently bonding 0.5% poly(hexamethylendiamine-guanidine hydrochloride) (PHMG), a guanidine-based antimicrobial polymer, based on total weight onto polypropylene (PP) matrix using a melt grafting method in supercritical CO2 (SC CO2) assisted process. Attributed to the higher grafting efficiency, the hydrophilic PHMG is uniformly dispersed in PP matrix without any aggregate, which potentially enhances the antimicrobial activity. The resulting PP-g-PHMG pellets showed quickly and efficiently antimicrobial activity against both Gram-positive and Gram-negative bacteria. Furthermore, the antimicrobial activity of the PP-g-PHMG non-woven fabrics prepared by a spun-bonded method remained even after constant water washing for 10 days, indicating its permanently antimicrobial ability via a contact activity rather than a release mechanism. In addition, animal tests were conducted to evaluate the safety of the antimicrobial PP fabric in the case of direct skin contact and water washing.