Amount Of Diene Research Articles

Effect of third monomer type and content on the UV stability of EPDM

Various uncompounded ethylene–propylene–diene (EPDM) elastomers were photo-oxidized using standard Weather-O-Meter (WOM) aging and oxygen absorption measurements during UV irradiation. The influence of the type and amount of diene on the UV stability was investigated. FTIR (ATR) measurements of the carbonyl absorbance after WOM aging were comparable with the outcome of the oxygen absorption tests. Both techniques showed a decrease in UV stability with increasing diene content. In addition, EPDM containing 5-ethylidene-2-norbornene (ENB) as the third monomer showed a higher UV stability compared to EPDM containing dicyclopentadiene (DCPD) as the third monomer. Furthermore, a linear relation was found between the carbonyl absorbance after WOM aging and the third monomer content for DCPD- and ENB-containing EPDM samples with comparable ethylene/propylene (C 2/C 3) ratio. The microhardness (International Rubber Hardness Degree) and the Young's modulus of the various EPDMs as function of the WOM irradiation time showed a maximum. This maximum is the result of parallel photo-crosslinking and chain-scission reactions, the latter being dominant in the later stages of the oxidation process. Combining the results from the FTIR measurements with the Young's modulus showed that DCPD-containing EPDM has a higher propensity to crosslinking reactions compared to ENB-containing EPDM.

Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7–35.8%), palmitoleolinolein (20.3–22.8%), dioleolinolein (15.0–15.4%) and trilinolein (8.8–10.7%) were the main components during roasting. However, roasting for 10 min at 220 °C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 °C, ensuring that a good-quality product would be attained. © 2000 Society of Chemical Industry

Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7–35.8%), palmitoleolinolein (20.3–22.8%), dioleolinolein (15.0–15.4%) and trilinolein (8.8–10.7%) were the main components during roasting. However, roasting for 10 min at 220 °C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 °C, ensuring that a good-quality product would be attained. © 2000 Society of Chemical Industry

Microwave roasting and molecular species of triacylglycerols in soybean embryonic axes

AbstractEmbryonic axes were separated from soybeans roasted in a microwave oven. Molecular species and fatty acid distributions of triacylglycerols (TAG) isolated from total lipids in the embryonic axis were analyzed by a combination of argentation thin‐layer chromatography (TLC) and gas‐liquid chromatography. A modified argentation‐TLC procedure, developed to optimize the separation of the complex mixture of total TAG, provided 15 different groups of TAG, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each band. Fifteen molecular species of TAG were still found in the embryonic axes following roasting treatment. Microwave roasting for 6 min did not change the molecular species of the embryonic axis TAG (with a few exceptions), nor cause a loss of unsaturated fatty acids. However, microwave roasting for 12 min caused a significant decrease (P&lt;0.05) not only in molecular species containing more than four double bonds but also in the amount of diene and triene species present in TAG. These results suggest that no significant changes in molecular species or fatty acid distribution of TAG would occur within 6 min of microwave roasting, ensuring that a good quality product would be attained.

Effects of Microwave Heating on the Molecular Species of Soybean Triacylglycerols

ABSTRACTMicrowave heating of whole soybeans resulted in an apparent increase of the total lipids. Molecular species of triacylglycerols were isolated from total lipids by a combination of silicic acid column chromatography and AgNO3‐thin layer chromatography (TLC). Fifteen molecular species of triacylglycerols were still found in whole soybeans following heat treatment. Microwave heating for about 5 min did not change all molecular species of soybean triacylglycerols nor cause a loss of unsaturated heat fatty acids. However, heat treatment for 8 min significant decrease not only in molecular species containing more than four double bonds, but also in the amount of diene and triene present in a triacylglycerol.

Copolymers of ethylene with bicyclic dienes

AbstractThe copolymerization of ethylene (E) with dicyclopentadiene (DCP), ethylidene norbornene (ENB) or methyl endomethylene hexahydronaphthalene (MEHN) by ZIEGLER‐NATTA catalysts in presence of H2 affords low‐mol.‐wt. products over a wide range of unsaturation. In this paper some characteristic features of the copolymerization and some physical properties of the raw products are discussed.For the catalytic system VOCI3‐Al2Et3Cl3 differences in catalyst efficiency, copolymer composition, diene incorporation and viscosity can be seen as a function of type and amount of diene monomer.Physical properties of the copolymers are strongly dependent on composition. Incorporation of dience results in lowered melting points of the parent PE. In case of E‐DCP and E‐ENB the materials become amorphous beyond 15‐20 mole‐% diene. At this composition minimum glass transition temperatures are seen.