Ultraviolet-irradiated Graft Polymerization Modification,Microstructure, Properties And Applications Of Polypropylene Fabrics

China’s synthetic fiber production accounts for ca.50%of the world’s total throughput, but the variety of functional fibers is limited. In recent years, the polymer modification techniques with y-ray, and electron-beam irradiation and plasma treatment have gained rapid progresses and found a lots of applications, which makes up for the shortage in the development of synthetic and fabrication technologies. Furthermore, the ultraviolet-irradiated graft polymerization has the features of low equipment cost, fast response, and easy operation. Particularly, the low UV penetration can strictly direct grafting to be taken place on the polymer surface, and thus does not damage the polymers. Therefore, UV grafting has already shown important application for improving the hydrophilicity and dyeability of polypropylene (PP).In this dissertation, the seven unsaturated monomers were grafted onto the surfaces of PP fabrics to improve their hydrophilicity via the UV-initiated graft copolymerization. The effects of three types of monomers, three kinds of morphologically different PP fabrics, and three different pretreatments on the grafting and the hydrophilicity of the grafted were investigated in detail. The adsorptive separation of simulated dyes and heavy metal ions waste waters were carried out. The major findings and conclusions are listed as follows.(1) The order of the graft polymerization reactivity was obtained based on the selected experimental conditions:MAPTAC> GMA> AA> HEMA> DADMAC> MAA-AA> MAAEssentially, the high reactivity, and the good wettability of the monomers on the surface of PP fibers, and the preferable solubility of the grafting polymer chains in the grafting solvent will result in a high grafting.(2) Among the three kinds of PP fabrics, SMS gave the highest degree of grafting since the inner ultrafine meltblown fiber layer soaked a large volume of grafting monomers, while the heavy monofilament MPF had the lowest. The hydrophilic monomer but the hydrophobic polymer of MAPTAC led to reduced crystallinity, whereas the twin hydrophilicity of monomer and polymer was no effect on crystallinity.(3) The water wettability of the grafted depends on the grafted polymer component, and fabric structure. The water contact angle of hydrophobic GMA grafts slowly reduced with grafting, while that of hydrophilic HEMA grafts decreased significantly. Although the grafting of hydrophilic AA and MAPTAC prefered to happen in the melt-blown layer in SMS, a lot of MAPTAC grafts produced wicking, whereas the low grafting AA still presented hydrophobic. Graft modification reduced the water flux of the fabrics, and the fluxes of the grafted rely on the fabric structure and the grafted polymer components. When the actual degree of grafting is equivalent to the theoretical degree of unit area and unit mass, the spun-boned fabrics have the largest fluxes. The hydrophobic grafting polymers caused a remarkably decreased flux whereas the hydrophilic polymer led to a trivial reduction.(4) The semi-crystalline PP fiber surface enriched free radicals after the electron-beam, and y-ray irradiation and the corona discharge pretreatment respectively, which significantly promoted the grafting of the hydrophobic GMA, with no effect on the grafting of hydrophilic HEMA and DADMAC. Among them, the corona discharge pretreatment is the most effective. The combination of radiation pretreatment, pre-soaked photo-sensitizer and neutralization of acrylic acid significantly improved the grafting of the PP monofilament cloth with uniformly thin layer covered.(5) It is the weak acid red aggregation that low initial dye concentration resulted small dye removal unexpectedly. Weak interaction between the dye molecules and grafted polymers led to the adsorption insensitivity towards temperature. Two kinds of dye molecules’adsorption kinetics and equilibrium obeyed Lagergren’s quasi-second-order kinetic equation and Freundlich isotherm respectively. The adsorption of strong alkaline polyelectrolyte PMAPTAC wasn’t interfered by small molecule electrolyte and acidity, vice verse for weak acidic poly(acrylic acid). The filtration results of simulated heavy metal ions and dyes wastewaters showed that the size of adsorbate, and the force between adsorbate and adsorbent determine the separation efficiency. The removal of heavy metal ions was low, but the adsorption capacity was high, vice verse for the dye molecules. This features and innovations of the dissertation include:(1) The comprehensive UV-grafting polymerization was carried out on the spun-bonded PP nonwovens, and the results indicated that monomer reactivity, the wettability of the monomer on the fiber surface and the solubility of the grafting polymer chains in solvent dominate the grafting.(2) The graftability of five kinds of polypropylene was investigated, and the results showed that fiber crystallinity, the type of crystalline, and fiber fineness are determining factors for grafting.(3) The grafting polymerization of monofilament fabric with the three pretreatments of y-ray, and electron-beam irradiation and corona discharge was studied, and the results demonstrated all pretreatments promote the grafting of hydrophobic glycidyl methacrylate onto the monofilament PP fabric. The combination of the pre-irradiation, the pre-soaking of photosensitizer and neutralization of acrylic acid improve significantly grafting.