Time Evolution of the Concentration Profiles of HALS Stabilizers and of the Corresponding Oxidation Forms across Poly(propylene) Plaques Irradiated with UV-Visible Light

Spatially resolved degradation in heterophasic polymers by ESR imaging and FTIR: The case of propylene-ethylene copolymers

“…The higher nitroxide content in HPEC1 in the early stages of thermal treatment can be explained by the expected higher diffusion of oxygen, HAS, and 2.7 × 10 -10 cm 2 /sec in the temperature range 298-348 K, and much higher in PE (74 × 10 -10 cm 2 /sec) in a similar temperature range (328-353 K). [24][25][26] The lower nitroxide content in HPEC1 as the treatment time increased cannot be explained if the only difference between the two HPEC samples is the rate of diffusion of oxygen and the mobility of other reactants. The explanation we offer is a higher consumption of nitroxides due to a higher degradation rate in HPEC1, as compared to HPEC2.…”

EPR Imaging Determination of High Molecular Weight Nitroxide Radicals in the UV Degradation of Polycarbonate-Poly(acrylonitrile-butadiene-styrene) Polymers

“…The different radical profile found in the pigmented and not-pigmented samples is related to the different rates of degradation since, when the degradation is fast compared to oxygen diffusion, [12] as in the not-pigmented samples, where the light is capable of crossing the whole plaque, the nitroxide formation is observed only in the proximity of the surfaces. [5,9] On the other hand, when the rate of degradation is slow as in thermally treated samples, a large nitroxide concentration is observed also in the inner part of the plaque. The different results obtained in our experiments with respect to those reported by Schlick and coworkers, [9] should be attributed to the different temperatures of the sample during the irradiation, 362 K and 318 K, respectively.…”

“…[5][6][7][8] The joined use of EPR and EPRI provides information not only on the nature of the radical present in a given sample and on its concentration in the bulk, but also on its distribution at various depths of the sample. These information may be very important both in clarifying the mechanism of polymer stabilization as well as in the technological search of better additives or of mixtures of additives exhibiting a synergetic protective action for polymers.…”

“…The EPRI technique has been successfully used in our laboratory to determine the nitroxide distribution within polypropylene plaques containing amine stabilizers exposed to accelerated aging processes by irradiation under air for several months. [5][6][7][8] Blends of polycarbonate (PC) with various styrene polymers represent an important family of materials for automotive usage. In particular blends of PC and poly-(acrylonitrile-butadiene-styrene) (ABS) are experiencing significant growth for automotive interior.…”

Spectral spatial electron paramagnetic resonance imaging as a tool to study photoactive dimethacrylate-based dental resins

“…They originated from hindered amines used as stabilizers. Lucarini et al carried out detailed studies on PP using 1D EPRI [23][24][25], Marek et al extended the work to polystyrene [26], while Schlick and collaborators used both 1D EPRI and 2D SSI to study the degradation of heterophasic system such as poly(acrylonitrile-butadiene-styrene) and propylene-ethylene copolymers [27,28], or very recently to measure diffusion coefficients of nitroxide radicals in propylene-ethylene copolymers [29] (for review on this topic see Refs. [30][31][32] by Schlick).…”