Antioxidants and Thermal Stabilizers

Why do the resins used in rotational molding processes typically contain a higher level of antioxidants and thermal stabilizers than the resins used to manufacture parts, by injection molding ... 

Mesitylene. One of the principal derivatives of mesitylene is the sterically hindered phenol of the structure shown in Figure 4. Its trade name is Ethanox 330 and it is produced by Albemade Corporation (formedy Ethyl Corporation) (31). Ethanox 330 is an important noncoloring antioxidant and thermal stabilizer for plastics, adhesives, rubber, and waxes (qv) (32,33) (see Antioxidants). The oral toxicity of Antioxidant 330 is extremely low (oral 1D. in rats > 15 g/kg) since its large size, Cc4H7 0, effectively eliminates absorption from the gastrointestinal tract. 

BNX lOlOTF, Antioxidant and thermal stabilizer, Product Data Sheet. Mayzo Corp ... 

Chem. Descrip. 2-(2H-Benzotriazoie-2-yi)-4-methyiphenyl CAS 2440-22-4 EINECS/ELiNCS 219-470-5 Uses UV absorber for use in piastics (rigid and piasticized PVC, unsat. polyesters, PU, acrylic poiymers, and poiycarbonates), coalings, rubber (nat. rubber, ABS, carboxyiated SBR latex, IPS, ASA, and SBS copolymers), adhesives, and org. polymers exhibits antioxidant and thermal stabilization props. 

Depending on the purpose of stabilizers, it is now customary to divide them basically into photostabilizers, antioxidants, and thermal stabilizers. However, such a division is rather arbitrary in character, since many of them can simultaneously perform various functions, depending on the type of material to be stabilized, the conditions of its reprocessing, use, etc. For example, the so-called antioxidants and thermal stabilizers are equally designed to inhibit oxidation processes and differ only in that they operate under different conditions. 

The condensation products of phenol and its all l derivatives with styrene or a-methylstyrene are receiving especially widespread use as antioxidants and thermal stabilizers of polymer materials. Under the action of styrene on phenol in the presence of an acid catalyst, a mixture of mono-, dl-, and trisubstituted derivatives is formed [127, 128, 131, 132, 158] ... 

It has been only found that some antioxidants and light stabilizers show the ability for partial inhibition of thermal destruction of the polyolefins. 

Chemical and thermal stabilizers both inactivate the byproducts of degradation processes, preventing them from causing further damage to the polymer. Their chemical structure and mobility in the part define their effectiveness in any given polymeric system. The most common type of chemical stabilizers are antioxidants. 

Cursory comparison of the character and behavior of flame retardants and thermal stabilizers including antioxidants yields the following ... 

HALS exhibit a complex behavior when present in combination with other antioxidants and stabilizers. Effective synergism in both melt and thermal stabilization has been achieved when secondary and tertiary HALS were used in combination with both aromatic and aliphatic phosphites the synergistic optimum depends on the structure of the phosphite. HALS also synergize the action of UV-absorbers, e.g., benzo-triazoles, in different polymers such as polypropylene, polystyrene, and ABS. " ... 

Traditionally, synthetic PAOs have had significant performance advantages over equiviscous mineral base oils by their higher viscosity index, lower pour point, reduced volatility and improved oxidation stability in the presence of antioxidants. GTL base oils now challenge PAOs in performance and can be very cost competitive with the relatively expensive synthetics. A review in 2006 described performance comparisons of base oils with a viscosity of 4 cSt at 100°C [37]. It is suggested that the GTL fluids can match the PAOs in Noack volatility, oxidation resistance and thermal stability, whereas the PAOs retain some superiority in their extreme low-temperature fluidity. 

Antioxidant technology To indicate the oxidation and thermal stability of a variety of ZnDTP-containing and ashless anti-wear hydraulic fluids, TOST and Cincinnati Milacron data - both relevant tests for this type of fluid - have been compiled and summarised. Table 4.9, from both published [80, 81] and in-house results. The data show that oxidation resistance and thermal stability of the premium fluids, both ashless and stabilised ZnDTP, are comparable and clearly outperform the normal-grade fluids. The normal ashless grade at 0.4-0.5% additives is superior to the normal ZnDTP-based grade, especially for thermal stability, which may be due to the use of thermally unstable secondary ZnDTPs. 

The presence of stabilizer has little effect on poly (vinyl chloride) carboxylation (Table VIII). Since the other polymers were also subjected to the carboxylation process without removing commercial additives such as antioxidants, UV and thermal stabilizers, antiblocking agents, etc.—the additives inhibit neither the polymerization of the styrene-maleic anhydride complex nor the grafting reaction. 

Polymers, during fabrication or storage or in service, may be exposed, sometimes for long periods, to the separate or combined effects of moderate or high temperatures, ultraviolet radiation, and air or other potential oxidants. Under these environmental conditions, polymers are susceptible to thermal, UV, and/or oxidative degradative reactions initiated, in most cases, by the generation of free radicals. Polymer stabilization, therefore, involves incorporation of antioxidants and thermal and UV stabilizers to minimize, if not avoid, such degradative reactions. 

It is true. As for things, some of them resist to degradation much better than others Like other polymers, PUs are subjected to thermal and photo-oxidative degradations, even during their synthesis. In order to reduce these effects polymers can be treated with suitable antioxidants and light-stabilizers [64,317]. 

Several companies now offer combinations of phenolic antioxidant with a phosphite in the same product. Cytec Industries markets a phenolic antioxidant combined with a hydrolysis-resistant phosphite, called Cyanox XS4. The components are both high molecular weight substances, so as to increase permanence and thermal stability. Cyanox XS4 was first targeted at polyolefins, where it was claimed to widen the processing window and reduce costs by allowing less stabiliser to be used, while still achieving minimal discoloration and melt flow. 

The use of phenolic and amino-based antioxidants (ie, thermal stabilizers) by this approach has been limited because they inhibit the free-radical polymerization process (polymerization inhibitor) leading to lower efficiency. One of the few commercial products produced is based on the polymerizable chain breaking antioxidant (AO 12b, Table 3), designed for NBR rubbers (Chemigum HR 665) that has been shown to offer superior antioxidant performance, especially imder aggressive (hot oil/high temperature) conditions, compared to low molecular mass conventional aromatic amine antioxidants (165). In spite of the successful synthesis and copoljmierization of a large number of reactive antioxidants, there is a lack of major commercial development and production of antioxidant systems... 

In applications involving no undue mechanical stresses, PP articles will withstand 100 °C for a long period of time, depending on the stabiliser systems. Consequently, the heat and thermal stability of PP is closely related to its maximum continuous use temperature (Section 4.2.2). Short-term exposure to 140 °C is also possible. It has been observed that a properly heat stabilised and properly processed material ean undergo up to five processing cycles without noticeable reduction in molecular weight or the level of antioxidant content. 

A unique phosphite which contains sulfur. It can be used as an effective heat and thermal stabilizer for a variety of polymers. It is particularly effective in polyolefins, where it acts to ii rove processing and UV stability. Can also be used as an antioxidant and a sulfur deactivator in lubricants while improving antifriction and antiwear characteristics. 

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