TWO-STEP GRAFTING ONTO POLY (ETHYLENE TEREPHTHALATE) USING BENZOYLPEROXIDE

Abstract

Two-step grafting onto commercial poly (ethylene terephthalate) (PET) fabrics was carried out with benzoyl peroxide (BPO) as initiator. The 1st step was the pretreatment of PET with the emulsion of BPO, and the 2nd step was the grafting of pretreated PET in the aqueous solution or the emulsion of vinyl monomers.In the pretreatment, it was considered that the diffusion of BPO into PET and the decomposition of BPO during the pretreatment had opposite effect on generating the active species for grafting. From this point of view, the effect of conditions of pretreatment on grafting of acrylic acid onto PET was discussed. When PET was pretreated for 30min. at 80-85°C, the highest grafting per cent was obtained.The organic solvents used in the pretreatment also had an effect on grafting and higher grafting per cent was obtained by using solvents of which solubility parameters were 9.0-10.5.In view of the stability of the active species for grafting, it was supposed that the active species were not radicals but BPO or hydroperoxides.In the grafting, maximum grafting per cent was obtained by the reaction at 100-110°C for 1hr. From the results of grafting of various monomers, it was found that vinyl monomers having lower propagation constants and higher affinity for PET had a tendency to give higher grafting per cent.When the mixture of two hydrophilic vinyl monomers were used for grafting, grafting per cent varied with mixing ratio of these monomers; e. g., acrylic acid (AA)/methacrylic acid (MAA), had a maximum grafting in the ratio 4/6-5/5 (mol./mol.). This phenomenon might be explained by a mutually aiding effect of each monomer in grafting.There was little difference among the hygroscopic properties of AA, MAA and AA/MAA grafted PET's. Na-salt form of 15% AA/MAA grafted PET showed the same level of moisture regain as cotton.