Functional modification of textile polymers via dry-state radical grafting polymerization

Heterogeneous functional modification of textile polymers is always a challenge. So far, only radical grafting polymerization is universally applicable to almost all existing textile polymers to introduce functions such as antimicrobial, antistatic and self-cleaning. However, the large amount of homopolymer byproducts generated during the solution grafting process poses serious problems for its application in the textile industry. This research focused on radical graft polymerization of vinyl/allyl monomers onto textile substrates and aimed at developing novel technologies for surface functional modifications of textiles. The peroxide-initiated grafting of functional monomers onto textile polymers such as cotton cellulose and polyester has been examined under a dry-state condition. Potassium persulfate served as an effective water soluble radical initiator to abstract hydrogen from cotton substrate. The formed cellulosic radical can initiate polymerization of the functional monomer allyl-dimethylhydantion (ADMH) so to graft ADMH onto cotton cellulose. The grafting sites and grafted polymer chain lengths on cellulose were studied by using hydrolysis of the grafted cellulose and mass spectrometer. The reaction mechanisms were proposed and rationalized thermodynamically. The grafting poly(allyl-dimethylhydantion) (PADMH) can not be cleaved off from cotton cellulose during a chlorine bleaching process, by which the grafted cotton is converted to a biocidal halamine structure. Mechanistic understanding of the grafting reactions led to the idea of adopting acyclic amide monomers to introduce biocidal function into textiles. Polyacrylamide (PAM) and polymethacrylamide (PMAM) grafted cotton samples were converted to acyclic chloramides to get a chlorine loading as high as 600ppm. Similar to the cyclic chloramides, the thus formed acyclic ones were able to provide powerful biocidal function: 6 log reducation of E.Coli at contact time of 15 minutes. For poly(ethylene terephthalate) (PET), the initiators with even higher ratio of abstraction vs. addition such as benzoyl peroxide were chosen for the grafting initiation. The ADMH grafting mechanism was studied using the similar methodology: hydrolysis following by IR, HPLC-MS and NMR analysis. It is the first time that real chemical grafting on cotton and polyester under dry-state condition are chemically confirmed.