THE EFFECT OF N,N-DIMETHYLFORMAMIDE AND POLYMER GRAFTING ON THE MORPHOLOGY OF POLYESTER FIBERS IN FABRIC SUBSTRATE

Photo-induced graft polymerization of acrylic acid (AA) and methyl acr ylate (MA) in the liquid and vapor phase, respectively, onto N,N-dimet hyformamide (DMF)-pretreated poly(ethylene terephthalate) (PET) fibers in fabric substrate was studied. The effect of various synthesis cond itions and DMF pretreatment on the graft yields on PET was investigate d. The internal morphology and properties of DMF-pretreated and grafte d PET fibers in the fabric were characterized using density and birefr ingence measurements, differential thermal analysis (DTA), Fourier tra nsform infrared spectroscopy (FTIR), dyeing methods, and critical diss olution times. The grafting was promoted by increasing DMF pretreatmen t temperature and the amount of DMF retention in the PET. Increasing b iacetyl and monomer flow time and irradiation time enhanced grafting. DMF pretreatment resulted in increases in total void content, degree o f crystallinity, trans-isomer content, chain folding, segmental mobili ty, and molecular packing of the PET, but caused decreases in its amor phous orientation, intermolecular forces, and individual void size thr ough longitudinal shrinkage, lateral swelling, and removal of oligomer s. Subsequent graft copolymerization led to further changes in the int ernal morphology and properties of the PET. PET grafted with AA had a higher cohesive energy density, lower degree of molecular packing, and larger individual void size, but less total void content, lower segme ntal mobility, less chain orientation, and a lower degree of crystalli nity. PET grafted with MA showed increases in total void content, indi vidual void size, segmental mobility, and molecular packing, but showe d decreases in chain orientation and degree of crystallinity. (C) 1996 John Wiley & Sons, Inc.