A polymer composition and its use. The polymer composition contains antimicrobial material for inhibiting the growth of micro-organisms in close proximity to said polymer composition. The polymer composition comprises a polymeric substrate comprising at least one polymer, a coniferous resin acid(s) dispersed in the polymeric substrate, and a booster material. The booster material comprises at least one of chemicals listed herein: higher alcohols, organic alkali salts or earth alkali salts, alkyl-p-hydroxybenzoates or alkali-poly-phosphates, nitrates, phosphates, and lactylates.
