Browsing by Subject "thermal oxidation"

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    Determination of Low Density Polyethylene Water Permeability, Transport Activation Energy, and Mechanical Properties after Thermal Oxidation and Immersion in Water
    (2019-08) Munir, Noumon
    Low Density Polyethylene (LDPE) thin film was exposed to oxygen gas overpressure and water. in a Parr Instruments pressure vessel at four temperatures 22, 50, 70 and 80°C; and, at 30 and 50 psi initial oxygen pressures. Sheet polypropylene (PP) and high-density polyethylene (HDPE) as well as injection molded HDPE, HDPP, and LDPE dogbones were exposed at 70°C and 30 psi initial oxygen pressure. Immersion of LDPE films was done under and above water at 80°C and 50 psi initial oxygen pressure. Permeation cup tests were done to determine the permeability of water vapor across the LDPE film at 60, 70, and 90°C. The extent of oxidation and functionality was monitored using ATR-FTIR and was consistent with previous work on polyethylene-oxygen reaction pathways. The permeability of the LDPE films and carbonyl content increased linearly with temperature, oxidation time, and oxygen pressure. The dogbones studied showed little change in mechanical properties.
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    The Formation Of 4-Hydroxy-2-Trans-Nonenal (HNE), A Toxic Aldehyde, In Beef, Pork And Chicken Fats Heated At Frying Temperature (185°C)
    (2017-09) Cao, Yan
    4-Hydroxy-2-trans-nonenal (HNE), a secondary lipid oxidation product, is of special interest because of its abundance and toxicity. In this study, the HNE formation and secondary lipid oxidation of varies types of beef, pork and chicken fats undergoing heat treatment at 185°C frying temperature was investigated. Beef, pork and chicken fats were selected based on their different degrees of unsaturation and fatty acid distribution. Beef, pork and chicken fats from different sources were chosen to give comprehensive result. These fats were heated at 185°C for up to 6 hours. Lipid oxidation and secondary oxidation product formation of these fats were measured every hour by the thiobarbituric acid reactive substances (TBARS) assay. The formation of HNE in fats heated at 185°C for 0, 1, 3 and 5 hours were measured as 2,4-dinitrophnyhydrazone derivatives using HPLC system. The results show that 1) the formation of HNE and total secondary lipid oxidation products from all fat sources were increased with the heating time; 2) HNE formation and total secondary lipid oxidation products levels in beef, pork and chicken fats are correlated with their linoleic acid and PUFA percentage, respectively; 3) the HNE formation and total secondary lipid oxidation products of fat extracted from ground meats were lower than that from fat tissues, this may be related to antioxidants content in the meat. Overall, beef fats produce less HNE and total secondary lipid oxidation products under thermal treatment, compared to pork and chicken fats as well as most vegetable oils.