Hindered Amine Stabilizers Research Articles

Investigation on the Durability of a Polypropylene Geotextile under Artificial Aging Scenarios

Geosynthetics are widely used in various civil engineering applications, such as geotextiles in coastal protection, and display a sustainable alternative to natural mineral materials. However, the full benefits of using geosynthetics can only be gained with a long service lifetime of the products. With the use of added stabilizers to the polymers, service lifetimes can be achieved in the range of 100 years. Therefore, accelerated aging methods are needed for the assessment of the long-term performance of geotextiles. In the present study, the behavior of geosynthetic materials made of polypropylene was investigated under artificial aging conditions involving elevated temperatures ranging from 30 to 80 °C, increased oxygen pressures ranging from 10 to 50 bar in water-filled autoclaves, and UV irradiation under atmospheric conditions. ATR-IR spectroscopy was employed to detect the increase in the carbonyl index over various aging durations, indicating the oxidative degradation of the geotextile. The most pronounced increase was observed in the case of aging through UV irradiation, followed by thermal aging. Elevated pressure, on the other hand, had a lower impact on oxidation. High-temperature size exclusion chromatography was utilized to follow the reduction in molar mass under different degradation conditions, and the results were consistent with those obtained from ATR-IR spectroscopy. In polyolefins such as polypropylene, Hindered Amine Stabilizers (HAS) are used to suppress oxidation caused by UV radiation. The quantitative analysis of HAS was carried out using a UV/Vis method and HPLC. The degradation of UV stabilizers during the aging of geotextiles is responsible for the oxidation and the reduction in the molar mass of polypropylene. From the results, it can be concluded that applications of PP geotextile without soil or sand cover might cause the risk of the formation of microplastic particles. Material selection, design, and maintenance of the construction must follow best practices, including the system’s removal or replacement at end-of-life. Otherwise, a sustainable use of geotextiles in civil engineering is not possible.

A non-target screening study of high-density polyethylene pipes revealed rubber compounds as main contaminant in a drinking water distribution system

Polyethylene (PE) pipes are often the material of choice for water supply systems, thanks to their favorable properties, such as high strength-density ratio and corrosion resistance. However, previous studies have shown that organic compounds can migrate from PE pipes to the water. This study aimed to identify potential organic compounds migrating from high-density PE (HDPE) pipes used to distribute drinking water in Denmark, based on laboratory experiments and sampling in the distribution system using a two-tiered study design.In the first tier, migration of volatile and semi-volatile organic compounds (VOCs and semi-VOCs) from HDPE pipes were investigated over one, three, and nine days in laboratory experiments, performed according to modified standards for migration testing (EN 12,873–1). The analytical workflow consisted of solid-phase extraction (SPE) for 10,000 times enrichment and gas chromatography – mass spectrometry (GC–MS) analysis from the water phase after migration. A total of 133 compounds originating from the PE pipes were detected. Thirty-one compounds were detected by suspect screening (SS), while the remaining 102 compounds were detected by non-target screening (NTS) analysis. Among the detected compounds were also hindered amine stabilizers (HALS), flame retardant, and plasticizer tris(2-chloroethyl) phosphate.In the second tier, drinking water from a water distribution system in Copenhagen, Denmark, with a newly installed HDPE pipe was sampled and analyzed with GC–MS and liquid chromatography high-resolution mass spectrometry (LCHRMS). A total of 51 compounds were detected in the water, 12 of which were assigned to migration from HDPE. Surprisingly, HDPE antioxidants and their degradation products contributed only a relatively small percentage of the total measured compound intensities in the drinking water distribution system. Instead, a larger proportion of the compounds detected were assigned to rubber seals, used upstream in the water system from the abstraction site to delivery at the consumer tap. Seals are considered trifle in the larger picture of materials in contact with drinking water, however these results may cause a reconsideration of this position.

Exploring stabilizer formulations for light-induced yellowing of polystyrene by high-throughput experimentation and machine learning

In this study, a high-throughput experimental protocol was established for yellowing inhibition of transparent plastics on the basis of solution film casting on microplates and ultraviolet/visible (UV/Vis) spectroscopic evaluation using a microplate reader. A combination of the protocol and a genetic algorithm realized a large-scale exploration of stabilizer formulations that consist of commercially available hindered amine stabilizers and UV absorbers, etc. The found formulations were highly effective in inhibiting the photo-induced yellowing of polystyrene, compared to the most efficient single stabilizer at the fixed concentration. The obtained data, which corresponded to seven years of aging (when sequentially acquired), were analyzed and validated based on decision tree classification, force-directed network visualization, and so on. A formulation design guideline was successfully derived that it is essential to combine as many stabilizers that are complementary and synergistic with each other as possible.

Pro-oxidant activity of biocompatible catechin stabilizer during photooxidation of polyolefins

Polymer plaques made of high-density polyethylene (HDPE) or cycloolefin copolymer (COC) were stabilized with natural phenolic stabilizer (+)-catechin (CAT) and aged using accelerated weathering technique (WOM; accelerated photooxidation). The efficiency of the phenolic stabilizer was compared with a well-established hindered amine stabilizer (HAS) Tinuvin®770 (Tin770). In pursuit of the stabilization and identification of short-living radicals generated in the process of photooxidation of the polymers, a spin trapping agent 2,4,6-tri-tert-butylnitrosobenzene (TTBNB) was added to selected samples. Profiles of oxidation products and crystallinity inside the HDPE plaques were determined by IR microspectroscopy, oxidation products in COC copolymers were identified using ATR spectroscopy, concentration profiles of radicals generated inside polymer plaques during WOM exposure were determined by ESRI, the changes of local mechanical properties at the surface of polymer plaques were characterized using microindentation hardness testing (MHI), and the surface morphology changes were studied by light and/or scanning electron microscopy. All methods are in accordance with the conclusion that the natural phenolic stabilizer CAT exhibited pro-oxidant activity during accelerated photooxidation of both polymers, i.e. higher concentration of oxidation products, bigger changes of local mechanical properties and/or more microcracks on the exposed surfaces in comparison with non-stabilized systems and systems stabilized with Tin770.

Thermal oxidation of poly(dicyclopentadiene) - Effect of phenolic and hindered amine stabilizers

The thermal oxidation of stabilized polydicyclopentadiene was deeply studied here for the first time. Three kinds of antioxidants (phenolic antioxidant BHT, monomeric hindered amine in alkoxylated form Tinuvin 123 and oligomeric hindered amine Chimassorb 2020) were compared at the same concentrations. Tinuvin 123 was observed to me more efficient than Chimassorb 2020 because of the “activated” nature of alkoxyamine in Tinuvin 123. Results were simulated using a completed version of previously established kinetic model for thin PDCPD films in order to be able to make reliable lifetime prediction of stabilized PDCDP.

Profluorescent nitroxide sensors for monitoring the natural aging of polymer materials

The utility of profluorescent nitroxides (PFNs) as sensitive probes to detect early stage photodegradation in a cyclic olefin copolymer, TOPAS®, during both natural aging and accelerated aging under laboratory conditions is reported. PFN additives in TOPAS® capture radicals to form fluorescent adducts as the material degrades. The levels of fluorescence detectable from the polymer reflect the degree of free-radical degradation in the material, with the PFN probes delivering enhanced sensitivity over traditional analytical methods for the detection of photodegradation of TOPAS®. The probes are able to highlight polymer degradation occurring within the oxidation “induction” period, where little change can be observed using infrared spectroscopy; however, their efficacy does not extend far beyond this period. The effective probe lifetime however can be significantly extended through the use of common additives such as the UV absorber (Tinuvin P) and a hindered amine stabiliser analogue (1,1,3,3-tetramethylisoindol-2-yloxyl, TMIO).

Global and Local Aging in Differently Stabilized Polypropylenes Exposed to Hot Chlorinated Water with and without Superimposed Mechanical-Environmental Loads.

The influence of chlorinated water on the global and local aging behavior of polypropylene (PP) was investigated for three differently stabilized PP grades consisting of the same PP base polymer. While one of the PP grades contained only a processing stabilizer (PP-S0), the other two were modified with a primary phenolic antioxidant (PP-S1) and a combination of a primary phenolic antioxidant and a hindered amine stabilizer (PP-S3). To study global aging effects, micro-sized specimens were pre-exposed to chlorinated water (5 mg/L free chlorine) at 60 °C for up to 750 h. Over the entire exposure period, significant material aging was detected by monitoring a continuous decrease in stabilizer content, oxidation induction temperature, mean molar mass, and mechanical strain at break. In terms of aging resistance and ultimate mechanical performance, PP-S1 was found to outperform the other two material formulations under these test conditions. Moreover, superimposed mechanical-environmental fatigue tests with cracked round bar specimens were carried out with the three PP grades in non-chlorinated (0 mg/L free chlorine) and chlorinated (5 mg/L free chlorine) water at 80 °C and 95 °C to study local crack tip aging effects. While the fatigue crack growth resistance substantially deteriorated for all three materials in chlorinated water, a significantly stronger effect was found for the higher temperature, with crack growth rates at a given stress intensity factor range in chlorinated water being ca. 30 to 50 times faster than in non-chlorinated water, depending on the material. Molar mass measurements of material samples taken from various positions of the tested CRB specimens provided clear evidence of enhanced local crack tip aging due to the chlorinated water environment.

Prooxidant activity of phenolic stabilizers in polyolefins during accelerated photooxidation

Polymer plaques made of high density polyethylene (HDPE) and of two types of cycloolefin copolymer (COC) differing in glass transition temperature, were stabilized with 0.2 or 1.0 wt % of natural (α-tocopherol) or synthetic (Irganox®1010) phenolic stabilizer or hindered amine stabilizer (Tinuvin®770) and aged using accelerated weathering technique (WOM). The efficiency of the phenolic stabilizers was compared among themselves and with well-established Tinuvin®770. Concentration profiles of radicals generated inside polymer plaques during WOM exposure were determined by ESRI, profiles of oxidation products and crystallinity inside the HDPE plaques were determined by IR microspectroscopy, oxidation products in COC copolymers were identified using ATR, the changes of local mechanical properties of the polymer plaques were characterized using microindentation hardness testing, and their morphology was studied by light and/or scanning electron microscopy. All the techniques evidenced high stability of neat COC against photooxidation processes, whereas neat HDPE exhibited fast photooxidation of the surface layers. Tinuvin®770 was found to provide long term protection to both HDPE and COC against photodegradation. In contrast, the same polymers stabilized with the natural phenolic antioxidant α-tocopherol (the most active component of vitamin E) or synthetic phenolic antioxidant Irganox®1010 exhibited an increase in the surface oxidation in comparison with the neat polymers during WOM exposure, proving prooxidant activity of phenolic stabilizers during WOM exposure in all polymers studied. The prooxidant activity α-tocopherol was stronger in comparison with Irganox®1010. We conclude that neither of the two phenolic stabilizers was able to provide long term protection of the investigated polymers against photooxidation.

Chemical functionalization of graphene oxide by a hindered amine stabilizer and evaluation of the product as a UV-stabilizer for polypropylene

The present work was devoted to synthesis of a novel UV-stabilizer based on graphene oxide for polypropylene. Hence, we grafted a hindered amine compound on graphene oxide through an amidation reaction. Fourier transform infrared (FTIR) spectroscopy and thermo-gravimetric analysis confirmed the grafting reaction. Also, X-ray diffraction together with scanning electron microscopy showed that the grafting reaction transforms the compact layered structure of graphene oxide into finer aggregation of loosely connected particles. Polypropylene film samples containing either of graphene oxide and the functionalized graphene oxide were prepared by solution mixing/anti-solvent precipitation followed by compression molding. Transmission electron microscopy showed significantly better dispersion of the modified graphene oxide in the polymer matrix compared to the pristine graphene oxide. Afterwards, the film samples were exposed to an artificial sunlight at 25 °C. It was proved by FTIR spectroscopy and tensile test that the modified graphene oxide at a concentration of 0.5 wt. % can efficiently retard the rate of the photo-oxidation of PP.

UV degradation of styrene-butadiene rubber versus high density poly(ethylene) in marine conditions studied by infrared spectroscopy, micro indentation, and electron spin resonance imaging

UV irradiation and thermal degradation were studied in marine conditions for styrene-butadiene rubber (SBR) and high density poly (ethylene) (HDPE) containing a Tinuvin® 770 hindered amine stabilizer. Electron spin resonance imaging (ESRI) was used to monitor degradation process in various depths and compare the polymers in terms of robustness to UV irradiation. In addition, both oxidative degradation and mechanical properties were studied by microscale methods, such as infrared microspectroscopy (IR) and microindentation hardness testing (MHI), enabling us to compare the material changes locally, i.e. both at the exposed surfaces and inside the samples. In SBR/Tin770 system, Tinuvin®770 stabilizer failed to protect the polymer matrix against photooxidation as clearly seen from IR/ATR spectra. The Weather-Ometer (WOM) aging resulted in strong oxidative degradation of both non-stabilized and stabilized SBR and caused remarkable changes in three regions of IR/ATR spectra. The strong photooxidative degradation was also manifested through the micromechanical properties of SBR/Tin770 systems. The change of the local properties was the same (within the standard deviations) for both stabilized and non-stabilized samples, which confirmed negligible stabilization efficiency of Tinuvin® 770 in the SBR system. In contrast to the SBR systems, similar experiments showed very dramatic stabilization effects in the HDPE/Tin770 system. ESR and 2D spectral-spatial ESRI directly proved the different degradation behavior of the two types of the composites: whereas in the SBR composites fast degradation was observed, high density poly (ethylene) showed much slower degradation. We attributed such striking difference to the modification of Tinuvin® 770 hindered amine stabilizer after vulcanization during preparation of SBR rubber, which apparently eliminated most of its protective activity.

Heterogeneity of Accelerated Photooxidation in Stabilized Bulk Commodity Polymers Studied by X-Band ESRI

Heterogeneity of photooxidation processes in plaques made of commodity polymers, high-density polyethylene, and cyclic olefin copolymer poly(ethylene-co-norbornene) (Topas® 8007) stabilized with various hindered amine stabilizers; some of them in combination with UV stabilizers exposed to accelerated weathering were studied using electron spin resonance imaging (ESRI) and three independent microscopic-scale methods: scanning electron microscopy, infrared microscopy, and microhardness testing. Concentration profiles of nitroxides mapping photooxidation process inside polymer plaques along the direction of incident radiation (perpendicular to the irradiated surface of the plaques) were determined by ESRI technique in dependence on the duration of the accelerated photooxidation. ESRI data were complemented with profiles of oxidation products, crystallinity, and microhardness measured inside the plaques along the same direction. Selection of stabilizers in the study was completed with α-tocopherol that is considered as the most active component of excellent processing stabilizer vitamin E.

A review on the mechanism of action and applicability of Hindered Amine Stabilizers

Hindered Amine Stabilizers (HAS) are by far the best performing UV-stabilizers and in a number of applications they are the best performing long-term heat stabilizer too. In this paper an overview is given of the different mechanisms proposed that can explain the high activity as well as the applicability of HAS as UV-stabilizer and as long-term heat stabilizer.

Stabilization of \u03b3-sterilized low-density polyethylene by synergistic mixtures of food-contact approval stabilizers

In our previous studies, we have found the synergistic combinations of stabilizers which follow different mechanisms of stabilization and are approved for food contact applications. The present attempt is to test the potentials of those systems in stabilizing γ-sterilized low-density polyethylene (LDPE). The results were discussed by comparing the stabilizing efficiency of mixtures with and without phenol systems as well as with their counterparts of isotactic polypropylene (iPP) and ethylene-propylene copolymers (EP) matrices. LDPE has been melt-mixed with tertiary hindered amine stabilizer (tert-HAS), oligomeric HAS stabilizer, phenolic and organo-phosphite antioxidants and subjected to γ-sterilization. Stabilization in terms of changes in oxidation products, tensile properties, yellowing and surface morphology was evaluated by FT-IR spectroscopy, Instron, colorimetry, and scanning electron microscopy (SEM), respectively. The results of the present study confirm the validity of those systems for protecting various polyolefins against γ-sterilization. The results showed that the synergism, antagonism and the trend in stabilization efficiency of the binary, ternary and quaternary stabilizer systems were almost similar in LDPE, iPP and EP matrices. The binary system of oligomeric HAS and tert-HAS has shown the antagonistic effect of stabilization, whereas their combination with organo-phosphite has exhibited synergistic effect even at higher doses of γ-sterilization. The combination of oligomeric HAS, tert-HAS, organo-phosphite and hindered phenol exhibited improved stabilization efficiency than single or binary additive systems. The phenol systems have shown long term of stability than that of phenol-free systems. It was found that the consumption of oligomeric stabilizer significantly depends on the components of stabilization mixture. It was concluded that the stability of polyolefins (LDPE, iPP and EP) against γ-sterilization can be achieved by blends of different stabilizers which are approved for food contact applications.

The effect of common agrichemicals on the environmental stability of polyethylene films

The impact of commonly used agrichemicals (Paraquat, Mancozeb, Chlorpyrifos and Sulfur) on the environmental stability of polyethylene films has been evaluated under accelerated photo-oxidative conditions. Paraquat and Mancozeb when applied to unstabilized clear polyethylene film, followed by exposure to UV radiation, resulted in direct attack of the polymer, evident by faster rates of oxidation and shorter times to embrittlement compared to a polyethylene control. Reapplication of these chemicals during exposure, as often occurs in agricultural practice, resulted in even faster degradation. In contrast, Sulfur and Chlorpyrifos did not have a significant effect on the photodegradation of exposed unstabilized polyethylene film. When the polyethylene film was pigmented (white top layer containing rutile titanium dioxide and carbon black in the bottom layer) and stabilized with the addition of hindered amine stabilizers (HAS), differences in oxidation susceptibility were seen with repeated exposure to Paraquat showing the most dramatic effect. This was evident by an increased carbonyl index, decrease in elongation at break and an increase in tensile stress at yield compared to a control film and other agrichemical treatments. These studies enable degradation from accelerated consumption of stabilizers by the agrichemicals (and their degradation products) to be differentiated from enhanced photochemical initiation of the polyethylene degradation.

Effects of electron beam irradiation on the property behaviour of poly(ether-block-amide) blended with various stabilisers

Abstract Radiosterilisation can induce modifications and/or degradation to transpire in poly(ether-block-amide) (PEBA) following irradiation. The current investigation utilises combined synergistic mixtures of stabilisers to minimise these effects, by melt blending them with the PEBA material. Hindered amine stabilisers (HAS), primary antioxidants and secondary antioxidants were the stabilisers incorporate to reduce/eliminate the effects of 50 kGy electron beam irradiation dose on the material. Results were discussed by comparing the stabilising efficiency of mixtures on the PEBA material in contrast to the control sample. Dynamic frequency sweeps demonstrated the formation of crosslinks, where the degree of crosslinking was dependent on the combination of stabilisers mixed in the base material (PEBA). The storage modulus displayed that PEBA blended with Irganox 565 had very slight changes in contrast to all other samples following irradiation. However, since this sample is a phenol containing system, severe discolouration was observed in comparison to other samples due to the oxidation of the hindered phenol. Overall, this study provides compelling evidence that a combined synergistic mixture of Irganox 565 (multifunctional phenolic antioxidant) and Tinuvin 783 (hindered amide light stabiliser) with PEBA, resulted in the best radiation stability.

Versatile strategy for fabrication of polypropylene nanocomposites with inorganic network structures based on catalyzed in-situ sol–gel reaction during melt mixing

Abstract A versatile strategy based on a catalyzed in-situ sol–gel reaction in melt mixing is presented for the fabrication of polypropylene (PP) nanocomposites that equip inorganic network structures. PP nanocomposites with TiO2 network structures were obtained by melt mixing PP powder which was preliminarily impregnated with titanium alkoxide and a catalytic component. The addition of catalytic components, especially hindered amine stabilizer, was found to be effective not only for the acceleration of the in-situ sol–gel reaction but also for improved dispersion of formed inorganic nanoparticles. The obtained PP/TiO2 nanocomposites exhibited the disappearance of the terminal flow at ca. 3 wt% of the TiO2 content, indicative of the network formation. Moreover, the PP/TiO2 nanocomposite films exhibited distinct optical properties: Not only high transparency for visible lights due to the excellent dispersion of the made nanoparticles but also absorption of UV lights, where absorption edges are tunable through a quantum effect for nanosized particles.

Heterogeneity of accelerated photooxidation in commodity polymers stabilized by HAS: ESRI, IR, and MH study

Heterogeneity of the photooxidation processes in plaques made of four commodity polymers, polypropylene (PP), polyethylene (PE), polystyrene (PS) and poly(ethylene-co-norbornene) (Topas®, TP) stabilized with hindered amine stabilizer (HAS) were studied using Electron Spin Resonance Imaging (ESRI) and three independent microscopic-scale methods: scanning electron microscopy (SEM), infrared microscopy (IR) and microhardness (MH). Concentration profiles of nitroxides mapping photooxidation process inside polymer plaques along the direction perpendicular to their surface were determined by electron spin resonance imaging technique (ESRI) in dependence on the duration of accelerated photooxidation. We present data characterizing stabilization activity of Chimassorb® 119, Chimassorb® 944, Tinuvin® 770 in combination with UV stabilizer Tinuvin® 320 or Tinuvin® 327, nitroxide HAS Prostab® 5415, and alkoxyamine derivative of HAS Tinuvin® NOR 371 and compare them with the previously published data. Comparison of profiles of oxidation products, crystallinity and microhardness measured inside the aged plaques made of non-stabilized semicrystalline polymers PE and PP and inside the plaques made of the polymers stabilized with Chimassorb® 944 together with SEM micrographs of the irradiated surface layers were found to confirm efficacy of the stabilizer used.

Sensitive luminescence techniques to study the early stages of polymer oxidation

This paper describes recent developments in the use of chemiluminescence (CL) and profluorescent nitroxides (PFNs) in probing the “induction period” of polymer oxidation. CL measures the instantaneous rate of reaction of hydroperoxides responsible for initiating degradation and the spreading of oxidation, while PFNs can be used to measure the concentration of alkyl radicals produced in oxidation events and thus provide an integrating sensor for the extent of cumulative damage. The PFN additive acts as an oxidation retarder by competing with oxygen to scavenge the alkyl radicals that generate chain carrying peroxy radicals and so mirrors the performance of hindered amine stabilisers (HAS) in one part of their stabilisation cycle. Using the example of polypropylene (PP) and cis-polyisoprene (PIP) as substrates which can rapidly spread oxidative damage, the factors controlling the reaction of PFNs can be determined from CL and fluorescence as well as infra-red (IR) spectroscopy through the detection of oxidation products as measured by the carbonyl index. Matrix effects on the reactivity are demonstrated using a polyethylene-norbornene copolymer (TOPAS) as carrier for both PIP and the PFN and it is seen that the PFN is a radical scavenger only above Tg of the carrier. When PIP alone is oxidized, the PFN is an integrating sensor for free radical production under ambient conditions for up to twelve months while also stabilizing the polymer. Critically, it is thus able to determine the underlying rate of radical production in the oxidation induction period.

Preparation of core–shell nanoparticle‐based hindered amine stabilizer and its application in polyoxymethylene

AbstractCore–shell nanoparticles chemically functionalized by hindered amine stabilizer (HAS), poly(BA‐MMA‐co‐PMPA) (PBMP), were prepared by two‐stage emulsion polymerization from butyl acrylate, methyl methacrylate, and 1,2,2,6,6‐pentamethylpiperidin‐4‐yl acrylate. The incorporation of HAS into the particles was confirmed by nuclear magnetic resonance (1H‐NMR) and the core–shell microstructure of PBMP particles was revealed by transmission electron microscopy. Furthermore, PBMP capable of one‐step toughening and photostabilizing, was melt‐blended with polyoxymethylene (POM), and its dispersion in POM was investigated by scanning electron microscope. The results showed that the core–shell nanoparticles could be well dispersed in POM matrix, indicating its good compatibility with POM. The UV resistance and impact resistance of POM were obviously improved by the HAS‐functional core–shell nanoparticles simultaneously. In addition, the core–shell nanoparticles could confer excellent protection to the surface of POM from UV‐light damage, regardless of the adverse effects on the thermal‐oxidative stability of POM, as investigated by thermogravimetry analysis under aerobic condition. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

NOR and nitroxide-based HAS in accelerated photooxidation of carbon-chain polymers; Comparison with secondary HAS: An ESRI and ATR FTIR study

Understanding processes resulting in heterogeneous degradation in polymers is of extreme importance for improving their stabilization and minimizing negative impact of photooxidation on the material properties. We adopted modern physical techniques for studies of spatial distribution of intermediates and products of photodegradation during accelerated ageing of four commodity polymers, polypropylene (PP), polyethylene (PE), polystyrene (PS) and poly(ethylene-co-norbornene) (Topas ®, TP) stabilized with hindered amine stabilizer (HAS). Concentration profiles of nitroxides inside polymer plaques along the direction perpendicular to their surface were determined by electron spin resonance imaging (ESRI) as a function of the duration of the accelerated photooxidation. We present data characterizing stabilization activity of three alkoxyamine derivatives of HAS (Tinuvin ® NOR 123, Tinuvin ® NOR 371, Flamestab ® NOR 116), Chimasorb ® 119 structurally similar to Flamestab ® NOR 116, and nitroxide-based HAS Dastib ® 1045 and compare them with the data characterizing stabilization activity of the secondary HAS (>NH) Tinuvin ® 770. ESRI data are complemented by ATR FTIR spectroscopic detection of oxidation products on the surface and inside the plaques and by data characterizing diffusive optical transmittance of the polymer plaques in the spectral region 280–400 nm (terrestrial range of the solar UV radiation).