PHOTOOXIDATIVE STABILITY

Finishing. AH acetal resins contain various stabilizers introduced by the suppHer in a finishing extmsion (compounding) step. The particular stabilizers used and the exact method of their incorporation are generally not revealed. Thermal oxidative and photooxidative stabilizers have already been mentioned. These must be carefully chosen and tested so that they do not aggravate more degradation (eg, by acidolysis) than they mitigate. 

Schnurpfeil G, Sobbi AK, Spiller W, Kliesch H, Wohrle D. Photooxidative stability and its correlation with semi-empirical MO calculations of various tetraazaporphyrin derivatives in solution. J Porphyrins Phthalocyanines 1997 1 159-167. 

Table 4 presents data on conservation of molecular mass of the crumb of dyed and undyed PCA samples before and after irradiation, and this shows great increase of photooxidative stability of dyed PCA samples. 

The reason of increased photooxidative stability is not only stabilizing activity of bis-aroilenbenzimidazoles derivatives but also the effect of these compounds on supermolecular structure of polymer matrix. As it is seen from the Table 6 physico - mechanical indexes of polymer do not practically depend on the method of additives introduction. Data of Table 6. agree with data of Table 5. In all cases the greatest degree of conservation of polymer initial properties is registered at the concentration of XLY compound - 1 mass %. 

Thus, the dye enters into small SMV filling in space of pores and, in addition, facilitates fibre hardening, which, in its turn, influences photooxidative stability of PCA-fibres. These data are proved by the results of physico-mechanical researches showing that dyed fibres greatly exceed initial ones in photooxidative stability (Table 6). 

All this shows that photooxidation of impurities in PCA at the initial stage does not influence further course of the process of PCA oxidation. That is why the rate of oxidation in stationary mode may be used for quantitative evaluation of photooxidative stability of PCA fibres. 

Thus, we may come to a conclusion that dyeing of polymers, containing free OH-groups, by active dyes considerably improves their thermal and photooxidative stability this is connected with substitution of hydrogen labile atom by more volumetric molecule. 

G. Geuskens, P. Bastin, Q. Lu Vinh, and M. Rens, Photooxidation of polymers. Part IV. Influence of the processing conditions on the photooxidative stability of polystyrene, Polym. Degrad. Stab. 1981, 3, 295-306. 

Antiphotooxidative effect of carotenoids on the induction lime of soybean oil as measured by the Rancimat method. The effect of 100 ppm or 200 ppm capsanthin, P-carotene, or lutein on the photooxidative stability of soybean oil containing 200 ppm chlorophyll was measured by the Rancimat method after 4 hours light exposure at 2S°C. Preliminary studies showed that the induction lime of purified soybean oil containing 100 or 200 ppm carotenoids without chlorophyll was slightly lower than that of the blank sample which contained no carotenoids (data not shown. Therefore, there is no anti-autoxidative effect of carotenoids on the soybean oil- Table I shows that as the concentration of the carotenoids increased from 100 to 200 ppm, the induction time as well as the anti-photooxidation index (API) increased. The induction time of soybean oil containing the carotenoids was longer than that of (he control sample which contained no carotenoid however, it was still shorter than that of the blank sample which contained no carotenoid and no chlorophyll. 

Photooxidative Stability and Photoyelloi ng of Electron-Beam- and UV-Cured Multifunctional Amine-Terminated Diacrylates... 

The same relative order was found for the decrease in the 2812 and 2878 cm band indices as shown by the data in Tables VI and VII. The infra-red data shows that the photooxidative stability of the amine acrylates depends on the nature of the polymer backbone. The order of decreasing stability is linked directly to the level of methylene protons alpha to the ether oxygen in each system. With the diethylamine derivative of TMPTA there is no ether functionality and this is the most photostable. The amine acrylate based on GPTA contains three alpha methylene protons adjacent to an ether oxygen. The amine acrylate based on TMPETA contains four alpha methylene protons adjacent to an ether oxygen. 

White, N. J., PhD Thesis, "Photooxidative Stability of UV and EB cured Acrylates", Manchester Polytechnic, UK, (CNAA), 1988. 

The influence of light exposure on the photooxidative stability of aqueous acrylic-based latices was examined using FTIR and hydroperoxide analysis. The nature of impurities and oxidation products generated during manufacture of PMM A and polybutyl acrylate latices were characterised and inter-related to their influences on subsequent photooxidative degradation. 20 refs. 

This research work focuses on process characteristics of pol5mier solutions, such as viscosity and electrical conductivity, as well as the parameters of electrospiiming using poly-3-hydroxybutyrate modified by titanium dioxide nanoparticles, which have been optimized. Both physical-mechanical characteristics and photooxidation stability of materials have been improved. The structure of materials has been examined by means of X-ray diffraction, differential scanning calorimetry (DSC), IR-spectroscopy, and physical-mechanical testing. The fibrous materials obtained can find a wide application in medicine and filtration techniques as scaffolds for cell growth, filters for body fluids and gas-air media, and sorbents. 

Finally, it should be stressed that the high interface area in nanocomposite materials enhances the total catalytic activity of clays [92], Indeed, the higher the dispersion degree achieved, the stronger effects on thermal and photooxidative stability of nanocomposite material were observed [91],... 

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