CARBOXYLIC-ACID FUNCTIONALIZATION OF NYLON-6 BY RADIATION GRAFTING AND CONVERSION TO ZINC SALTS - EFFECTS ON PHYSICAL-PROPERTIES

Functionalization of polymers by grafting monomeric species on to the backbone of molecular chains with the use of gamma-radiation has been used extensively. In this work methacrylic acid was grafted onto a com mercial grade of polycaproamide (Nylon 6) by preirradiating the polyme r granules to 15 kGy at a rate of 1.0 kGy per hour and subsequently im mersing these in a 10% aqueous solution of methacrylic acid in the pre sence of small quantities of FeSO4 as homopolymerization inhibitor. Th e polymer was subsequently neutralized by mixing it with zinc acetylac etonate in a laboratory scale melt mixing device. The acid-grafting po lymer modification resulted in an increase in glass transition tempera ture, while the addition of zinc acetylacetonate gave rise to two tran sitions: The lower transition corresponds to a miscible mixture of fre e polyamide and acid-grafted polymer, both plasticized with undecompos ed zinc compound, while the upper transition corresponds to the zinc s alt of the acid grafted polyamide. Through rheological measurements it was shown that both the acid-grafted polymer and the derived zinc sal t have a branched structure, possibly containing also some crosslinked domains. Large improvements in solvent resistance were observed for b oth type of polymer modifications.