Interactions between light stabilizers and pigment particles in polymeric coatings

Adsorption experiments have been carried out to understand the interactions responsible for UV light stabilizer adsorption on pigments in coatings. Light stabilizer adsorption on various pigments was studied in xylene solutions to eliminate potential interference from the cure process. Adsorption isotherms were determined for UV absorbers and hindered amine light stabilizers (HALS) compounds. Infrared spectral analysis revealed that chemical interactions at the pigment surface are responsible for the observed effects. In some cases the chemical surface interactions are likely to prevent the adsorbed molecules from functioning as light stabilizers.     

Studies on the interaction of photoreactive light stabilizers and UV-absorbers

Coatings, like all organic substances, are submitted to photoageing during their life time. Ultraviolet light absorbing additives (UVAs) and hindered amine light stabilizers (HALS) often are added to improve their performance. These additives can be lost by migration to the surface, where they are exposed to physical depletion, as well as through photodegradation of the molecule itself. Modifying hindered amine light stabilizers by introducing a photoreactive site gives the possibility to fix the stabilizing molecule onto the polymer matrix. The influence of the presence and the type of UV absorbers onto the photografting reaction will be discussed.     

Effect of penta- and tetramethyl HALS on the radiation resistance of polypropylene

2,2,6,6-Tetramethyl-4-piperidinyl methacrylate (TMPM), a new pentamethyl HALS 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate (PMPM), their homopolymers (PTMPM and PPMPM), and their copolymers, [i.e., TMPM or PMPM copolymerized with monomers methyl methacrylate (MMA), methacrylic acid (MAA), acrylic acid (AA), and styrene (St) separately] were synthesized. PMPM shows an extremely excellent stabilizing effectiveness on improving the radiation resistance of polypropylene (PP) in comparison with other low molecular weight (LMW) HALS or polymeric HALS. Polymeric HALS shows a much higher thermal stability and better extraction resistance than that of LMW HALS. It is found that the Eb values of the PP-added pentamethyl HALS series are higher than those of PP with the corresponding tetramethyl HALS series at a given irradiation dose. A conclusion can be drawn that the pentamethyl HALS series has a higher stabilizing effectiveness than that of the tetramethyl HALS series. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2649–2656, 1998     

Modifications of carbon for polymer composites and nanocomposites

The various forms of carbon used in composite preparation include mainly carbon-black, carbon nanotubes and nanofibers, graphite and fullerenes. This review presents a detailed literature survey on the various modifications of the carbon nanostructures for nanocomposite preparation focusing upon the works published in the last decade. The modifications of each form of carbon are considered, with a compilation of structure-property relationships of carbon-based polymer nanocomposites. Modifications in both bulk and surface modifications have been reviewed, with comparison of their mechanical, thermal, electrical and barrier properties. A synopsis of the applications of these advanced materials is presented, pointing out gaps to motivate potential research in this field.