MARC details
| 000 -LEADER |
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| fixed length control field |
03905nam a2200313Ia 4500 |
| 003 - CONTROL NUMBER IDENTIFIER |
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| control field |
MX-MdCICY |
| 005 - DATE AND TIME OF LATEST TRANSACTION |
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| control field |
20250625160144.0 |
| 040 ## - CATALOGING SOURCE |
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| Transcribing agency |
CICY |
| 090 ## - LOCALLY ASSIGNED LC-TYPE CALL NUMBER (OCLC); LOCAL CALL NUMBER (RLIN) |
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| Classification number (OCLC) (R) ; Classification number, CALL (RLIN) (NR) |
B-16051 |
| 008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION |
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| fixed length control field |
250602s9999 xx |||||s2 |||| ||und|d |
| 245 10 - TITLE STATEMENT |
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| Title |
Current trends in mode of action of Hindered Amine Light Stabilizers |
| 490 0# - SERIES STATEMENT |
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| Volume/sequential designation |
Polymer Degradation and Stability, 40(2), p.167-215, 1993 |
| 520 3# - SUMMARY, ETC. |
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| Summary, etc. |
The stabilization mechanisms of Hindered Amine Light Stabilizers (HALS)involving mainly various oxidation products of HALS do not account for the most important experimental facts. Part of these facts pertains to the dependence of HALS performance on their concentration. In polypropylene the performance increases linearly with HALS concentration as long as this concentration is not too high. In high density polyethylene the performance is a linear function of the square root of HALS concentration. Another part of the experimental facts concerns the decrease of the concentration of the light stabilizers on UV exposure of HALS stabilized polyolefins. The decrease is first-order in both PP and PE-HD. However, this decrease, independent of initial HALS concentration in PE-HD, decreases with increasing HALS concentration in PP. The role of the oxidation products of HALS in polyolefin stabilization is discussed in detail. It is found that there is a fundamental difference between the tertiary hydroxylamine ethers mainly formed in polypropylene and the secondary hydroxylamine ethers formed in polyethylene. The latter are postulated to be much more reactive than the former under photooxidative conditions because they contain an a-hydrogen atom prone to attack by peroxy radicals. Various mechanisms are proposed for this reaction. They account for the products found in polymers as well as in model systems. New stabilization mechanisms are proposed to explain the experimental facts. They are based on modified photooxidation mechanisms of unstabilized polymers. Initiation of photooxidation of polyolefins by excited polymeroxygen complexes is of prime importance. This type of initiation remains essential throughout polyethylene photooxidation during which hydroperoxides do not build up. It usually becomes rapidly negligible in polypropylene in comparison with initiation by tertiary hydroperoxides. Initiation of photooxidation in HALS stabilized polyethylene involves HALS-oxygen complexes throughout the useful lifetime of the polymer. Initiation of photooxidation of HALS stabilized PP is attributed to photolysis of tertiary hydroperoxides as long as the concentration of HALS is not too high. The HALS stabilization mechanisms proposed involve quenching of excited polymer-oxygen complexes. Formation of complexes between peroxy radicals and secondary HALS is another important aspect of these mechanisms. The peroxy radical/HALS complex can either react photolytically on absorption of UV light or react with a second peroxy radical. The latter leads to a termination reaction between two peroxy radicals as it is observed in the absence of HALS. The formal kinetics based on the mechanisms envisaged explain the experimental results obtained with HALS stabilized PP and PE-HD. It is postulated that the mechanisms discussed are valid, at least in part, for many polymers other than polyolefins. © 1993 |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
AGENTS |
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COMPLEXATION |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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COMPOSITION EFFECTS |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
FREE RADICALS |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
HIGH DENSITY POLYETHYLENES |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
OXIDATION |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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PEROXIDES |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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PHOTOCHEMICAL REACTIONS |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
PHOTOLYSIS |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
POLYPROPYLENES |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
REACTION KINETICS |
| 650 14 - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
STABILIZATION |
| 700 12 - ADDED ENTRY--PERSONAL NAME |
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| Personal name |
Gugumus, F. |
| 856 40 - ELECTRONIC LOCATION AND ACCESS |
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| Uniform Resource Identifier |
<a href="https://drive.google.com/file/d/10JFCuIDhHaXACam-UgY-jw2gnW5HQsMd/view?usp=drivesdk">https://drive.google.com/file/d/10JFCuIDhHaXACam-UgY-jw2gnW5HQsMd/view?usp=drivesdk</a> |
| Public note |
Para ver el documento ingresa a Google con tu cuenta: @cicy.edu.mx |
| 942 ## - ADDED ENTRY ELEMENTS (KOHA) |
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| Source of classification or shelving scheme |
Clasificación local |
| Koha item type |
Documentos solicitados |
