Antioxidants and UV stabilizers

More degraded than HDPE by heat, light, and oxygen because of tertiary hydrogens. Antioxidants and UV stabilizers can be added. 

Polyolefin resins contain only carbon and hydrogen, and additives, such as some antioxidants and UV stabilizers. Moreover, the presence of hetero-elements, such as chlorine and bromine is undesirable, as these elements distribute over the three product phases-gas, liquid, and solids, reducing the market potential and value of each of these. Studying their elimination is a major consideration in developing processes for mixed plastics. 

Investigation of antioxidants and UV stabilizers from plastics Part I. Comparison of HPLC and SEC Preliminary SEC/MS study. J. High Resolut. Chromatogr. 1990, 13, 5-12. 

Nerfin, C. Salafranca, J. Cacho, J. Rubio, C. Separation of polymer and on-line determination of several antioxidants and UV stabilizers by coupling size-exclusion and normal-phase high-performance liquid chromatography columns. J. Chromatogr., A 1995, 690, 230-236. 

Rubber-modified plastics (e.g, ABS), which are available in latex form, have also been modified with thio antioxidants and UV stabilizers. The 2-hydrobenzophennone (IX) reacts to give a 30% concentrate of which 80% of the UV stabilizer used becomes chemically attached to the polymer (24). The concentrates can be used either as... 

Antioxidants inhibit oxidation and are usually employed in combination with UV absorbers. Most antioxidants used for urethane coatings fall into the following classes substituted phenols, aromatic amines, condensation products of aminophenols with aldehydes, thio compounds, and phosphites. Often combinations of antioxidants from the above categories exhibit a synergistic effect. More recently Mathur et al. (125) carried out an extensive study involving the use of one to six stabilizers, selected from the above antioxidants and UV stabilizers, employing several independent test methods, to study the thermooxidation of urethane and urethane-urea films. 

Antioxidants and UV stabilizers for WPC roofing shingles, tiles, and slates... 

As it was mentioned above, polypropylenes are more prone to oxidation, hence, requiring significantly higher amounts of antioxidants and UV stabilizers compared to PE. It was shown that oxygen intake is much faster in polypropylene compared to that in PE [10], The primary reason is in the microbranched chemical structure of PP (see above), containing tertiary hydrogens that makes formation of hydroperoxides in PP much easier compared to that in polyethylenes. Overall, the mechanisms of oxidation (both photo- and thermooxidation) in PP and PE are quite different. For example, the termination reaction rates for oxidation in PE are 100-1000 times faster compared to PP [11]. 

Cedar-colored composite containing wood flour (50% w/w) and HDPE without antioxidants and UV stabilizers (AO/UV) showed a Af shift of 8.4 and 6.8 units in a weathering box and outdoors, respectively, while the same composite loaded with AO/UV (5% w/w) showed a A shift of 5.6 and 5.2, respectively. A decrease in fading was 50 and 30% in the box and at the natural weathering, respectively. However, with the same composition but colored differently (redwood), a A shift of 10.0 and 6.8 units was observed in a weathering box and outdoors, respectively, while the same composite loaded with AO/UV (5% w/w) showed a A shift of 9.2 and... 

Elvax 150 softens to a viscous melt above 70°C, and therefore Is not suitable for temperature service above 70°C when employed In a fabricated module. A cure system was developed for Elvax 150 that results In a temperature-stable elastomer ( ). Elvax 150 was also compounded with an antioxidant and UV stabilizers, which Improved Its weather stability and did not affect Its transparency. The formulation of the encapsulation grade ethylene vinyl acetate Is given In Table I. These Ingredients are compounded Into Elvax... 

Figure 8 FID chromatogram of antioxidants and UV stabilizers. Column PS-089, 20m x 0.3mm, glass. Carrier gas H2. (Reproduced from Blum W and Damasceno L (1987) High temperature glass capillary gas chromatography using OH-terminated polysiloxane stationary phases. Separation of antioxidants and UV stabilizers. Journal of High Resolution Chromatography and Chromatography Communications 10 472-476.)...

Poly(ethylene) is usually supplied with antioxidants and UV stabilizers already added. For industrial purposes, 2% carbon black, which is a good UV stabilizer, is worked in in the form of a master batch. A master batch, which is a polymer concentrate of the additive, makes the addition simpler. 

Polyurethanes obtained from aromatic diisocyanates undergo slow oxidation in the presence of air and light causing discoloration, which is imacceptable in some applications. In contrast, polyurethanes obtained from aliphatic diisocyanates are color stable, although it is necessary to add antioxidants and uv-stabilizers to the formulations to maintain the physical properties of the polymers with time. 

The schematic separation shown in Fig. 2 represents the molecular-weight (MW) distribution of the polymeric gum base used in chewing gum, followed by the lower-MW components in decreasing order of size. A similar example could be a chromatogram of PVC with a mixture of plasticizers, antioxidants, and UV stabilizers. 

Figure 13 Polymer additive analysis by HPLC of a synthetic mixture of antioxidants and UV stabilizers (Alliance reproducibility study). An analysis of this type could be used to deformulate a competitive material.

Some titanates have low flash points, and products should be handled as instructed by the suppliers. In the presence of phenolic compounds such as antioxidants and UV stabilizers, titanates can cause discoloration. 

Figure 6.9 ALKANOX 240 Chemtura sold its antioxidant and UV stabilizer business to SK Capital Partners in May, 2013.

Vargo and Olsen used absorbance and mass spectrometric detectors to detect antioxidant, and UV stabilizers leaving an hplc column in acetonitrile extracts of polypropylene. 

The fourth factor, and one which is least understood from both a commercial and scientific point of view, is the nature and mode of the interaction with antioxidants and UV stabilizers. ... 

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