Study On Modification Of Poly(Ethylene Terephthalate) By Free Radical Grafting Polymerization And Its Performance

Poly(ethylene terephthalate) (PET) has been widely used for engineering plastics and textile fibers due to its excellent physical and mechanical properties and processing characteristics. However, the high degree of crystallinity and poor moisture regain more or less spoils the clothing cosiness while the production capacity of PET fibers has climbed up to well over 10 million tons. In this dilemma, the improvement of PET fiber hydrophilicity and the expansion of PET fiber usage in engineering and decoration applications could be two effective measures. In this work, the hydrophilic polymers have been successfully grafted on PET fiber surfaces confirmed with infrared spectroscopy and scanning electron microscopy. The effect of the grafting ratio on the clothing properties, such as moisture regain, water imbibition, air permeation and mechanical properties, were investigated in detail. The cationic dye (5GN) and copper ions (II) removals from aqueous solutions were conducted carefully and the ion-polymer adsorption mechanisms were unveiled. The most important findings could be as follows:(1) Polyacrylic acid was grafted onto the PET fabrics by using reverse microemulsion polymerization after the fabrics being irradiated with argon plasma, with grafted polymer particle sizes around a few micrometers. The irradiated fabrics can be added intermittently during polymerization. This will be benefit to controlling the production cost and minimization of the environmental impact.(2) The moisture regain and hydrophilicity were improved markedly via irradiation and graft polymerization. The moisture regain was up to 7% when the grafting ratio was 20%. The negative effect on air permeation can be neglected if the grafting ratio was relatively small. The relationship between the hand handle and the grafting ratio presented U type curve due to the counterbalancing of physical crosslinking and hydrophilicity. The mechanical properties of PET fabrics were improved after grafting as well.(3) The copper ions and cationic red dye can be effectively removed by polyacrylic acid(PAA) aqueous solution, with copper ion removal 99% at the molar ratio of carboxylic group to copper ion 20, and with the dye removal 96% at the molar ratio of carboxylic group group and dye 2. (4) The adsorption and removal process with PAA and PAA grafted PET fabrics could be described by Langmuir and Freundlich isotherms and Lagergren pseudo-second kinetics. The activation energy for the copper ion adsorption was 48.9 kJ/mol whereas the dye adsorption process showed non-temperature dependence. The adsorption efficiency and rate of grafted PAA were far lower than those of virgin PAA. The adsorptions of copper ion and cationic dye would follow the ion exchange mechanism.(5) The PET fibers grafted with poly(acrylamide) (PAAM) indicated an efficient removal of copper ions. Lagergren pseudo-second kinetics can be applied to explain the adsorption behaviour of PAAM grafted fibers. The adsorption activiation energy was 23.9 kJ/mol. The interaction between copper ions and PAAM functional groups seemed to observe the ion coordination mechanism.The main features and innovation points of the thesis may include the following aspects:(1) The combination of argon plasma irradiation and reverse microemulsion polymerzation was firstly implemented to improve the hydrophilicity of PET fabrics. The novel idea was patented.(2) The Langmuir and Freundlich isotherms were firstly attempted to account for the dynamic adsorption processes of copper ions and cationic dye, and the interesting results were obtained.