Polymeric materials react with molecular oxygen in a process called autoxidation that can be initiated by heat, UV light, mechanical stress, catalyst residues or through reaction with other impurities. Free radicals are generated, which react rapidly with oxygen to form peroxy radicals. Antioxidant protection is particularly critical under high temperature processing and other thermo-oxidative operation conditions. Antioxidants prevent polymer degradation through oxidation by controlling molecular weight changes that lead to a loss of physical and aesthetic properties as well as destroys functional properties. Most polymers except PS, PMMA and general purpose LDPE require antioxidant systems. Polypropylene requires antioxidants at a higher level as it is prone to oxidative degradation. PVC uses only a very small amount of antioxidant during stripping operation for removing free vinyl chloride. Polypropylene and some polyethylene resins in their natural state are inherently unstable and degrade when exposed to oxygen. During degradation, the polymers change color and begin to flake away until the material becomes useless. When PP or PE degrades, chain scission occurs- the breaking up of the polymer chains into smaller pieces. The physical properties of the polymer deteriorate and its average molecular weight (chain length) decreases, melt flow rate increases leading to formation of a powdery surface. Polymers that contain unsaturated carbon-carbon bonds are particularly prone to oxidation. For this reason, unsaturated polymers, such as natural and synthetic rubber and ABS plastic resins, which contain isoprene and butadiene components respectively, could be oxidized easily without antioxidant protection. Polymer degradation is a natural phenomenon that cannot be totally stopped. What resin producers seek to achieve is to stabilize the color and physical properties of polymers for a reasonable life span. Oxidation may occur at relatively low temperatures, including ambient storage. The ease of oxidation of organic materials is related to the tendency of the polymer to participate in free-radical reactions with oxygen. Typically antioxidant is required at about 0.1-0.25% of polymer weight and is incorporated by polymer producers after the completion of polymerization process and before melt homogenization to form pellets. The global antioxidant demand for 2009 as per SpecialChem could be close to about 850,000-900,000 tons valued at US$2-2.2 bln. The estimates for 2014 could be at just above 1.1 mln tons valued at about US$2.75 bln showing AAGR of 4% despite weaker demand of polymers in 2008 and 2009. North America was the largest user of antioxidant so far but demand growth is China has been very rapid. According to www.adhesivesmag.com, degradation can occur more rapidly at elevated use temperatures, as well as during exposure to significantly higher temperatures while mixing or compounding, and during extrusion coating or application to various substrates (as in the case with hot-melt pressure-sensitive adhesives). Polymers endure oxidation at almost every stage in their life cycle right from manufacturing and processing to storage and end use. Hot-melt adhesives are kept at elevated temperatures, often above 300°F, for proper application, and must be sufficiently stable in these temperature ranges. Degradation is initiated by some input of specific energy that may be in the form of either thermal or mechanical energy. Impurities, catalyst residues or an inherently oxidation-prone component can lead to the generation of a free radical species, that rapidly reacts with oxygen to form peroxy radicals. Peroxy radicals are capable of abstracting hydrogen atoms from somewhere in the adhesive matrix to form hydroperoxides, ROOH, and another free radical, R•. Hydroperoxides are quite unstable and can be easily decomposed into alkoxy, RO•, and hydroxy, •OH, radicals. These two radicals may then react with other labile hydrogen atoms and continue to propagate more and more radical species. Left unchecked, this cycle can rapidly lead to gross degradation of the adhesive. Stabilizers are not equally effective at all temperatures. Some stabilizers, such as phosphites and hydroxylamines, are most effective at elevated temperatures and are most commonly used as melt process stabilizers, as their effectiveness is greatest during processing and compounding. Phenolic antioxidants are useful during processing and as long-term antidegradants. The mechanism of radical scavenging by phenolic antioxidants is well understood. An oxygen-centered free radical is capable of abstracting the phenolic hydrogen to form the relatively stable phenoxyl radical. This phenoxyl radical is then capable of scavenging additional radicals contributing to the stability of the adhesive. While the phenolic antioxidant plays the role of a sacrificial scavenger, it is chemically transformed by successive radical reactions. Ultimately, if the radical generating mechanisms are too great, the transformation of the antioxidant can lead to the generation of a chromophore, which can lead to noticeable discoloration of the material. Although this discoloration may be undesirable, in the absence of a stabilizer the adhesive may discolor at an even faster rate and/or suffer from loss of adhesive properties with the possibility of product failure. The use of secondary antioxidants, such as phosphites and thioesters, can often improve stabilization during extrusion and compounding, and may also provide improvements in color. Phosphites decompose hydroperoxides into non-radical generating byproducts. Thioesters are typically used in combination with phenolic antioxidants. Thioesters are commonly used in adhesives requiring long-term, high-temperature performance. Diphenylamines, when used in combination with phenolic antioxidants, also provide excellent long-term thermal aging while maintaining good color control. Hydroxylamine antioxidants are multifunctional and can react with both radicals as well as hydroperoxides.