AbstractsEngineering

Kinetics and Mechanisms of the Oxidation Processes for Unsaturated-Hydrocarbon-Modified Scavengers

by Hao Li




Institution: University of Toledo
Department: College of Engineering
Degree: PhD
Year: 2010
Keywords: Chemical Engineering; Materials Science; Polymers; PET; Poly ethylene terephthalate; Packaging; Active Barrier; Oxygen Scavenger; Polymer; Polymer Processing; Shelf Life; Oxygen; Permeation
Record ID: 1873740
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279218555


Abstract

Poly(ethylene Terephthalate) (PET) is a prominent packaging material which is widely used in the plastic packaging industry. When compared with traditional packaging materials, such as steel and glass, the oxygen barrier property of PET is moderate at ambient temperature. The moderate oxygen barrier property of PET limits the application of PET for packaging some oxygen sensitive products, such as beer. Several approaches have been made to enhance “shelf life” of PET packaging material, especially for oxygen sensitive foods. The active barrier packaging technique, which absorbs oxygen during its permeation route into packaged article, was studied in this research. Unsaturated hydrocarbons were used to modify PET to develop an oxygen scavenging system which can react with oxygen as an oxygen scavenger. In this research the unsaturated hydrocarbon is low molecular weight hydroxyl terminated polybutadiene. After the modification, the modified PET should maintain the favorable properties of PET and have an oxygen scavenging capability. The reason for blending hydroxyl terminated polybutadiene (HTPB) and PET was that the hydroxyl end group of HTPB was expected to react with end groups of PET to form a copolyester. The PET/HTPB copolyester will have different optical, thermal and mechanical properties than those of a unreacted PET/PBD physical blend. In this research, the oxidation mechanisms and kinetics of pure polybutadiene was studied first. Factors such as the molecular weight and composition of polybutadiene, which can affect oxidation mechanisms and kinetics, were analyzed. Activation energies of unsaturated olefin groups in the oxidation reactions were obtained. In the second portion of this research, low levels of hydroxyl terminated polybutadiene were reactively extruded with PET to form a polybutadiene modified PET. The oxidation kinetics and mechanism of this polybutadiene modified PET were also studied. Factors that can affect oxidation kinetics, such as the molecular weight of polybutadiene, concentration of polybutadiene, dispersion effect of polybutadiene in the modified PET and catalyst effect on oxidation kinetics, were included in the study of this unsaturated hydrocarbon modified PET. The reactions between hydroxyl terminated polybutadiene and PET during the reactive extrusion process were also confirmed and identified by infrared end group analysis method, a proton NMR method and a content extraction method. The evaluation of reactive extrusion process between polybutadiene and PET, were also studied. Finally suggestions were made on the future study of oxygen scavenging packaging techniques.