Oxidative stability, blending

Physical properties of carbon black-filled EPR and EPDM elastomers have been found to be comparable with the suUur-cured analogues [372]. Aromatic oils increase the optimum dose requirement for these compounds due to the reaction of the transient intermediates formed during radiolysis of the polymer with the oil as well as energy transfer which is particularly effective when the oil contains aromatic groups. The performance and oxidative stability of unfilled EPDM as well as its blend with PE [373], and the thermal stabdity and radiation-initiated oxidation of EPR compounds are reported by a number of workers [374,375]. 

Attempts have also been undertaken to improve the processability of PMR imide resins through molecular weight adjustments and exchange of the monomers employed. LARC 160 as an example here Jeffamine AP22, a eutectic blend of MDA type amines, was used as a polyamine instead of the crystalline MDA. This modification provided a quasi melt processable PMR resin (15). Other modifications were studied with the aim of improving the thermal oxidative stability by using hexafluoroisopropylidene dipthalic anhydride as a monomer (16). 

Fig. 4. Effects of phosphoric acid (PA) treatment on the thermo-oxidative stability of PBI and PBI/PEI blend films aged in air at 315 °C...

Blend systems with significantly improved thermo-oxidative performance can be achieved through incorporation of carefully designed polyimide molecules. As shown in Table 1, a copolyimide containing the sulfone and 6F moieties which exhibits a Tg above 300 °C (see Fig. 5), as well as extraordinary short-term thermo-oxidative stability can be synthesized. 

T50I(NPG)/PMDA was of particular interest because of its adhesive characteristics, oxidative stability, and polymer cost. Table III shows the improvement in adhesion obtained when various substrates were coated with blends containing this polyester (acid number 39). As indicated in the table, the ease of obtaining adhesion on the different substrates decreased approximately in the following order brass > steel > copper > chrome-coated steel > aluminum > nylon 66 > poly (ethylene terephthalate). In spite of the wide differences in structure and polarity of the various polymers, the carboxylated polyester significantly improved the adhesion of the coatings. 

Though FAME has limited oxidation stability, they remain a valid alternative for diesel. Conventional diesel fuel has a boiling range of 180-340 °C, with a composition of n-alkanes, cycloalkanes, alkyl benzenes, and polyaromatic compounds. Fossil diesels have a CN in the range 40-100. FAME has properties that are close to all these basic diesel properties. FAME can also easily blend with fossil diesel at any level due to their similar solvent behavior the viscosity of fossil diesel and biodiesel are also in the same range. 

Growing interest in polymer blends is due to the feasibility of varying properties of the materials within wide limits which may modify tensile strength, impact strength, etc. Numerous papers have appeared in connection with the preparation and mechanical properties of polyolefin blends. However, there appears to be a lack of information regarding oxidative stability of this type of blend. 

Hydrogenation of a fat and oil basestock increases the oxidative stability. As a rule, the lower the base IV the better the oxidative stability. However, as base hardness is increased, the level of hardstock required to reach a desired consistency must decrease. Hardstock reduction reduces the plastic range and heat tolerance. Therefore, oxidative stability improvements are achieved at the expense of plasticity and a wide plastic range can be at the expense of oxidative stability. The extent that one attribute can be compromised to improve another must be determined by the requirements of the intended food product. Oxidative stability is directly related to the level and type of unsaturated fatty acids present therefore, oxidative stabihty results do not average. For example, a 50 50 blend of a 40-hour AOM basestock and a 100-hour AOM basestock will not have an AOM stabihty of 70 hours, but rather will be closer to the component with the lower AOM stabihty (152). 

---