Combined oligomeric light and heat stabilizers

The synthesis of graphene-based antioxidants to promote anti-thermal properties of styrene-butadiene rubber

An immobile antioxidant (GO-RT) was successfully synthesized and possessed outstanding anti-oxidation performance in an SBR matrix.

Spectroscopic, Physical and Topography of Photochemical Process of PVC Films in the Presence of Schiff Base Metal Complexes

The photostability of poly(vinyl chloride), PVC, containing various Schiff base metal complexes (0.5% by weight) was investigated. Various indices corresponding to a number of functional groups were monitored with irradiation of polymeric films to determine their photostabilization activities. The quantum yield of the chain scission (Φcs) of modified polymeric films was found to be (1.15–4.65) × 10⁶. The surface morphology of a PVC sample was investigated by the use of atomic force microscope (AFM). The photostability of PVC films in the presence of Schiff base additives was found to follow the following order: PVC < PVC + CuL₂ < PVC + CdL₂ < PVC + ZnL₂ < PVC + SnL₂ < PVC + NiL₂. Various mechanisms for PVC films photostability containing the Schiff base additives have been suggested.

Photoinduced Copolymerization of APMP-MMA: The Role of Reactive Hindered Amine APMP

4-Acryloyl-1,2,2,6,6-pentamethyl-piperidinol (APMP) is a reactive hindered amine that prolongs the service life of the polymeric materials and exhibits high stability, good resistance to extraction, and low toxicity. In this paper, a photoinduced free radical copolymerization of APMP and methyl methacrylate (MMA) is accomplished at ambient temperature in solution. APMP plays a key role in the copolymerization, owing to the nitroxides generated in situ from the moiety of 1,2,2,6,6-pentamethyl-piperidine under UV irradiation, and mediates the copolymerization, which is confirmed by the linear kinetics. With the increment of initial monomer feed ratios of APMP/MMA, both the copolymerization rate and the average molecular weight increase. According to the reactivity ratios from the extended Kelen-Tüdos (KT) method at high conversion by1H NMR spectroscopy, a nonlinear model is established and the sequential distribution in the copolymers is also investigated. The dispersion of APMP units is regulated by the feed ratios and reactivity ratios.

Antioxidation efficiency and reinforcement performance of precipitated-silica-based immobile antioxidants obtained by a sol method in natural rubber composites

This precipitated-silica-based immobile antioxidant (P-RT) possesses outstanding reinforcement and anti-oxidation performance in an NR matrix. E.g. the NR/P-RT composite is far longer than NR composites containing the general antioxidant 4010NA.

Effects of climate change and UV-B on materials

The outdoor service life of common plastic materials is limited by their susceptibility to solar ultraviolet radiation. Of the solar wavelengths the UV-B component is particularly efficient in bringing about photodamage in synthetic and naturally occurring materials. This is particularly true of plastics, rubber and wood used in the building and agricultural industries. Any depletion in the stratospheric ozone layer and resulting increase in the UV-B component of terrestrial sunlight will therefore tend to decrease the service life of these materials. The extent to which the service life is reduced is, however, difficult to estimate as it depends on several factors. These include the chemical nature of the material, the additives it contains, the type and the amount of light-stabilizers (or protective coatings) used, and the amount of solar exposure it receives. Concomitant climate change is likely to increase the ambient temperature and humidity in some of the same regions likely to receive increased UV-B radiation. These factors, particularly higher temperatures, are also well known to accelerate the rate of photodegradation of materials, and may therefore further limit the service life of materials in these regions. To reliably assess the damage to materials as a consequence of ozone layer depletion, the wavelength sensitivity of the degradation process, dose-response relationships for the material and the effectiveness of available stabilizers need to be quantified. The data needed for the purpose are not readily available at this time for most of the commonly used plastics or wood materials. Wavelength sensitivity of a number of common plastic materials and natural biopolymers are available and generally show the damage (per photon) to decrease exponentially with the wavelength. Despite the relatively higher fraction of UV-A in sunlight, the UV-B content is responsible for a significant part of light-induced damage of materials. The primary approach to mitigation relies on the effectiveness of the existing light stabilizers (such as hindered amine light stabilizers, HALS) used in plastics exposed to harsh solar UV conditions coupled with climate change factors. In developing advanced light-stabilizer technologies, more light-resistant grades of common plastics, or surface protection technologies for wood, the harsh weathering environment created by the simultaneous action of increased UV-B levels due to ozone depletion as well as the relevant climate change factors need to be taken into consideration. Recent literature includes several studies on synergism of HALS-based stabilizers, stabilizer effectiveness in the new m-polyolefins and elucidation of the mechanism of stabilization afforded by titania pigment in vinyl plastics.