Vegetable oils thermal stability

Nag and Haidar reported the purification of vegetable oil extracted from the seeds of Pongamia glabra and its ability to substitute commercially available factices [33]. Factices are usually used for mastication of NR during production of tubing, automobile parts, and window seals. The authors reported improvement in thermal stability of the NR vulcanizate after the factice was added. 

The stability of C60 and C70 solutions in vegetable oils has been studied in air and under inert atmosphere, after thermal processing and under the action of UV radiation. In all cases it has been found that C60 and C70 are prone to form adducts with the fatty acid chains of the vegetable oils. The adducts are formed both by radical and Diels-Alder mechanisms. The pharmaceutical valency and potential of such adducts has also been discussed. 

The thermal stability of oxytetracycline in liquid media, as indexed by the antimicrobial activity retained following heating at 71 C, has been shown to be much less than that of other antibiotics such as aminoglycosides and -lactams (71, 72). Recent investigation on the thermostability of oxytetracycline in water and vegetable oil showed that the drug is unstable in water at 100 C with a half-life of 2 min, but more stable in oil at 180 C with a half-life of 8 min. 

The physical properties and thermal stability of SPEs are comparable with those of conventional fats and oils with the same fatty acid prohles. The physical characteristics of SPEs, similar to those of TAGs, are determined by the properties of the fatty acid side chains (38). Eor instance, SPEs produced from predominantly highly unsaturated fatty acids are clear liquids resembling conventional vegetable oils. On the other hand, SPEs made with more saturated fatty acids are opaque solids, resembling solid fats with a higher melting point (41). 

Current research efforts are directed toward improving the thermal and low-temperature stability of vegetable oils by chemical modification, blending with functional fluids and additive response studies. 

Thermal analysis methods, such as pressurized differential scanning calorimetry (PDSC), are popular for the determination of oxidative stabilities of vegetable oils (33, 36, 37). 

Javni, I. Z.S. Petrovic A. Guo R. Fuller. Thermal stability of polyurethanes based on vegetable oils. /. Appl. Polym. Sci. 2000, 77, 1723-1734. 

The presence of repeating units of ester (—COO) and amide (—NHCO) in the polymeric chain of vegetable oil-based poly(ester amide) resins improves the ease of application, thermal stability and resistance against... 

The initial degradation of vegetable oil-based polyurethanes occurs at a faster rate than in synthetic poly(propylene oxide) (PPO)-based polyurethanes, although at relatively high temperatures, PPO-based polyurethanes display a faster loss. However, the situation is reversed in an oxygen atmosphere (air). Thus, vegetable oil-based polyurethanes exhibit better oxidative thermal stability than standard PPO-based polyurethane. ... 

A variety of poly/dihydric oils are used for the preparation of glyddyl ether-type epoxy resins. These include bisphenols, namely bisphenol-A (BPA), bisphenol-F (BPF), bisphenol-S (BPS) and bisphenol-H (BPH) and so on. Other aromatic diols and polyols such as phenolic resin, MF resins and hyperbranched polyol may also be used in the preparation of vegetable oil-based epoxy resins. Bisphenol-A (2,2-bis(4-hydroxyphenyl)propane) is one of the most widely used aromatic diols for the synthesis of epoxy resin. The resins are commonly used as lacquers for coated metal products such as food cans, bottle tops and water pipes. There are also reports on the use of bisphenol-S (BPS) (bis(4-hydroxyphenyl) sulphone), in the synthesis of epoxy resin. The advantages of resistance to deformation by heat and improvement of thermal stability were observed for such epoxy resins. The presence of sulphone group (BPS-based epoxy resin) in the epoxy resin exhibits better gel time than BPA-based epoxy. Another important diol, namely bis(4-hydroxydiphenyl)methane or bisphenol-F (BPF) is used for the synthesis of low viscosity epoxy resins. BPF generally comprises several isomers such as bis(2-hydroxylphenyl)methane (i.e. ortho-ortho isomer), bis(4-hydroxylphenyl)methane (i.e. para-para isomer) and... 

As with other polymers and resins, the modification of epoxy resins eliminates a number of disadvantages including brittleness, low thermal stability and high flammability to give the required properties for end applications. Considerable effort has therefore been made to improve the thermal and mechanical properties of vegetable oil-based epoxy resins. These may be grafted or blended with other flexible resins such as polyester, polyacrylate and polyurethane to improve their flexibility and other performance characteristics. 

A study of glass fibre reinforced soybean oil-based polyurethane indicates that the mechanical properties such as tensile strength (259 c 270 MPa), flexural strength (418 cf. 444 MPa), tensile modulus (17 ct 18.6 GPa) and flexural modulus (18 cf. 27 GPa) of the soybean-based composites, were comparable with those of composites based on petrochemical (Jeffol) polyurethane. Since this soybean oil-based polyurethane composite offers better thermal, oxidative and hydrolytic stability than those based on petrochemicals, vegetable oil-based polyurethane composites could offer a viable alternative to petrochemical-based composites. 

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