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|Title:||Engineering of Hyperbranched Polyethylene and its Future Applications|
|Keywords:||Chemical Engineering;Chemical Engineering|
|Abstract:||<p>The present study is concerned with the modification of hyper branched polyethylene (HBPE) via peroxide initiation and grafting with maleic anhydride. High-temperature solution modification using xylene as solvent was conducted, and the resultant material was characterized in terms of its structural, rheological, and physical properties, and compared to its unmodified counterpat. Moreover, the susceptibility of hyperbranched polyethylene to degradation/ crosslinking is investigated and compared to other commercially available polyolefins. Nevertheless, crosslinking of maleic anhydride grafted hyperbranched polyethylene is conducted in exploration of potential applications for this material.</p> <p>Peroxide initiated modification of hyper branched polyethylene was conducted to examine its vulnerability to degradation/ crosslinking relative to other commercially available polyolefins. Creep recovery was used to measure the percentage change in zero shear viscosity upon modification while <sup>13</sup>C-NMR was used to give the number of methyl, methylene, and methane groups. The work elucidated that the dominant reaction undergone by hyperbranched polyethylene upon peroxide initiated modification is degradation, in a fashion similar to polypropylene, which is due to its high degree of branching.</p> <p>Peroxide initiated grafting of hyper branched polyethylene with maleic anhydride was conducted and the effects of reaction time, reaction temperature, monomer concentration, initiator type, and initiator concentration were systematically examined. The structure of the resultant functionalized polymer was confirmed via FTIR and <sup>13</sup>C-NMR, and a maximal grafting density of 1.7 % was achieved using 2 wt.% MAH and 2 wt.% DCP in the preparation process. Alternating dominancy between the grafting reaction and other side reactions was noticeable when varying the initiator and the monomer concentrations. Moreover, a drop in the water contact angle upon modification suggested that the grafted polymer is more compatible with polar substrates. Furthermore, rheological characterizations showed that functionalized HBPE exhibits a Newtonian behavior, which is characteristic of its unmodified counterpart; however showed some slight shear thinning behavior at low temperatures.</p> <p>Crosslinking of HBPE-g-MAH using a diamine was conducted in solution and in melt in an effort to find a potential application for the resultant polymer. The structure of the resultant polymer was confirmed through FTIR and the effect of reaction time, reaction temperature, and diamine concentration on the degree of cross linking was investigated. A maximal degree of crosslinking of 70% was achieved, where the structure of the polymer was found to have tremendous effect on the concentration of diamine necessary to gel the polymer. Nonetheless, the formation of a soft solid material from two liquid reactants suggested that HBPE-g-MAH could be a potential material for reaction injection molding applications.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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