discoloration of polymers by phenolic antioxidants in philippines
Discoloration of polymers by phenolic antioxidants
Discoloration of polymers by phenolic antioxidants. However, some products of their thermolysis are discolouring and accumulate slowly in the polymer matrix. The principal contribution to polymer discoloration is due to formation of quinone methides. Their discolouring effect is reduced in propionate-type phenolics,...
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Discoloration of polymers by phenolic antioxidants
Part of colour development in aged polyolefins stabilized with phenolic antioxidants can be attributed to the formation of conjugated diene compounds, arising as a consequence of sacrificial trapping of alkylperoxy radicals by phenolics. The discoloration depends on the structure and concentration of the phenol transformation products.
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Color Inhibition of Phenolic Antioxidants in Ziegler-Natta
antioxidants and therefore enhance the discoloration in the polymer [13]. Early studies demonstrated that the combination of titanium with phenolic antioxidants results in the formation of colored species [15, 20]. Some thiobi-sphenols have been reported to afford good color stability, and they perform as well as primary antioxidants, owing to the phenolic groups that they possess [21]. Good color
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Discoloration phenomenon induced by the combination
Heat treatment of the phenolic antioxidant BHT in combination with an HALS light stabiliser promotes oxidation of BHT by the HALS, resulting in discoloration. Discoloration of BHT by an HALS is accelerated the higher the HALS concentration and the stronger the basicity of the HALS.
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Polyolefin Discoloration: New Additive Solutions Solve
Polymers stabilized with phenolic antioxidants can be susceptible to discoloration if the stabilization system is “over-used” due to harsh processing conditions, or the reactivity of phenol with oxides of nitrogen (NxOy).
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Phenolic Antioxidants
Phenolic antioxidants inhibit autooxidation of organic polymers by reducing the amount of peroxyl radicals during processing, storage and service. They are strong hydrogen / electron donors and, in addition, their radical intermediates are relatively stable due to aromatic resonance stabilization of the unpaired electron.
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Antioxidants Stabilizers Selection for ... - Polymer Additives
Antioxidants Stabilizers Selection for Polyolefins (PP, PE) Polymer degradation is a natural phenomenon that cannot be totally stopped. It tends to deteriorate the physical & mechanical like molecular weight, melt flow rate, appearance, processing and thermal stability properties of the polymer.
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INTRODUCTION TO POLYMER ADDITIVES AND STABILIZATION
polymer at various stages throughout the polymer lifecycle. – An organophosphite, may be used as a short-term antioxidant to protect the polymer during the high temperature and shear conditions of processing. – A phenolic antioxidant may then be used for long-term protection. Additives may be incorporated into a product either
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Antioxidants as Sources of Plastics Discoloration
Polymers & Polymer Composites, Vol. 10, No. 1, 2002 41 Antioxidants as Sources of Plastics Discolouration: Structural Effects degradation is coloured and can contribute to the overall discoloration effect. QUINONE METHIDES Quinone methides 16 (QM) are final and oxidation-resistant transformation products of most phenolic
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Antioxidants: hindered phenols
Pospíšil, J. (1993) Chemical and photochemical behaviour of phenolic antioxidants in polymer stabilization — a state of the art report, Parts I, II, Polymer Degradation and Stability, 39, 103–115; 40, 217-232. CrossRef Chemical Scholar
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Discoloration of polymers by phenolic antioxidants | J. Pospıšil
Although discoloration of plastic polymers arises from many causes, additives, especially phenolic antioxidants, are the major reason forThe sacrificial reaction of phenolic antioxidants forms byproducts having quinonoidal structures that cause yellowing of the polymer (Cooper, 1987;Epacher
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Phenolic Antioxidants | Polymer Chemistry
Phenolic antioxidants inhibit autooxidation of organic polymers by reducing the amount of peroxyl radicals during processing, storage and service. They are strong hydrogen / electron donors and, in addition, their radical intermediates are relatively stable due to aromatic resonance stabilization of the
Send InquiryAntioxidant effect of polyphenols and natural phenols
A polyphenol antioxidant is a type of antioxidant containing a polyphenolic substructure and studied in vitro. Numbering over 4,000 distinct species mostly from plants, many of these compounds have antioxidant activity in vitro, but are unlikely to be antioxidants in vivo.
Send InquiryPhenolic Antioxidant - an overview | ScienceDirect Topics
Use of phenolic antioxidants, in spite of a large number of commercial products available, is quite limited in PVC. The major use is polymerization, but also some formulations used inDiscoloration and staining: In general, phenolic antioxidants tend to be nondiscoloring and amines are discoloring.
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Disentangling structure-dependent antioxidant mechanisms in
Excellent and selective correlations between the electron-transfer (ET) or hydrogen atom transfer (HAT) capacity (DPPH and lipid peroxidation inhibition assays) and EPR indices of π-electron spin delocalization delineate specific structural determinants of antioxidant activity in biomimetic phenolic
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Discoloration Effects of High-Dose γ-Irradiation and Long-Term
The International Journal of Polymer Science is a peer-reviewed, Open Access journal that publishes original research articles as well as review articles on theJ. Pospíšil, W.-D. Habicher, J. Pilař et al., “Discoloration of polymers by phenolic antioxidants,” Polymer Degradation and Stability, vol. 77
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Antioxidants & Antidegradants | Ozone | Polymers
Multifunctional phenolic antioxidants are very high performance antioxidants, exhibit extremely low volatility and do not cause contact / migratory staining or discoloration of the rubber products. Higher molecular weight of multifunctional phenolic antioxidants also contributes to practically no.
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Polyolefin Discoloration: New Additive Solutions Solve Common
Polymers stabilized with phenolic antioxidants can be susceptible to discoloration if the stabilization system is “over-used” due to harsh processing conditions, or the reactivity of phenol with oxides of nitrogen (NxOy). The discoloration-resistant stabilizer system DRS-C provides equivalent melt flow
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Investigation of Discoloration of Packaged Fortified Salt under
Most antioxidants contain phenol, oxidation of these phenolic compounds results in yellow discoloration.The discoloration was most likely due to an interaction between potassium iodate (an oxidizing agent) and antioxidants in the packaging material.
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Hindered Phenols | Antioxidants for Plastics | amfine.com
Hindered phenols are primary antioxidants that function by scavenging peroxy radical intermediates in theDuring end use at elevated temperatures, hindered phenols can reduce discoloration and also improveAO-50 General purpose hindered phenolic antioxidant for polyolefins, styrenic polymers
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