Sol-gel derived silica and hybrid films from tetraethoxysilane (TEOS) and 3-glycidyloxypropyltrimethoxysilane (GLYMO) were deposited by dip-coating, in order to find the best treatment. GLYMO-based treatments preserved textile feel of the material. The coatings were characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and water contact angle measurement. IR spectra confirmed the existence of silicate network and successfully conducted modification for both precursors. DSC and TGA showed that the conditions of hydrolysis had greater influence on TEOS than GLYMO-based treatments. Both treatments shifted the degradation onset to higher temperatures. SEM images showed that polyurethane surface and pores were completely covered and filled by silica or hybrid thin films forming a composite organic-inorganic coating. Hydrophobic effect was preserved for all the samples, except for a single treatment of the GLYMO, due to its polar epoxy group.

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Ever increasing ozone concentrations in the earth's atmosphere polluted by photochemical smog raise the question of possible ageing of fibers in such an environment. This paper investigates polypropylene fibers characterized by pronounced ageing in the natural environment under the impact of sunlight. Fibers are exposed to ozone for varying times and temperatures in a concentration range that can be expected in a heavily polluted urban industrial environment. Changes in the level of chemical composition and molecular configuration are investigated, together with morphological characteristics and end-use properties. Results indicate that, even under relatively mild ozone conditions, hydroperoxide groups are created, morphological surface changes occur, fibers become more brittle and lose strength, and the isotacticity of the configuration is pronounced, but there are some rather positive effects as well. I The investigation described in this paper is primarily aimed at determining the possibly detrimental influence of ozone on polypropylene (PP) fibers. These fibers are highly sensitive to atmospheric factors, especially ultraviolet rays [3, 4, 11 ], so the question arises whether (and if so, how much) the increased amount of ozone in the troposphere influences the problem of PP fiber ageing in atmospheric conditions. The literature on the subject indicates a lack of research on this topic, especially where fibers, as a specific form of the material, are concerned.Oueslati et al. have made some interesting investigations of the impact of ozone on chemical and morphological changes in PP fibers [8, 9, 101, which were exposed to ozone concentrations of -4.5 x 106 pphm, a very intensive treatment. This amount of ozone is a few thousand times higher than the average concentrations in polluted environments registered for a number of years in various parts of the world (Los Angeles, California; Arkon, Germany; Basel, Switzerland; Sydney, Australia). All the concentrations registered were in the range between 1.5 and 4 pphm [ 12], while occasional peaks of pollution reached-115 pphm (Los Angeles) or -75 pphm (Zurich). Using IR-and ESR spectroscopy, the authors investigated chemical changes in PP macromolecules [9, 10], and with electronic microscopy, they showed what this level of &dquo;ozonization&dquo; does to the core/sheath structure of PP fibers [8]. Similar morphological changes were also observed by Catoire et al.[2] at somewhat milder, but still highly intensive, ozone treatments (3.1 x 105 pphm).The literature does not offer proof of the impact of ozone on other relevant physicomechanical properties of the fibers, which is important for assessing ageing during use in real conditions of air pollution with ozone. For this reason, our investigation deals with ozone concentrations slightly higher than peak values in polluted urban environments. We focus on end-use properties, but we also consider other relevant properties for a complete overview of the problem.. MethodologyAll the tests involved undyed PP filaments...

ABSTRACT:The influence of exposure to artificial light (ultraviolet and visible spectrum) on the thermal degradation process of polypropylene fiber has been investigated. The activation energy E as a kinetic parameter of the fiber thermal decomposition has been defined by means of the Flynn-Wall and Freeman-Carroll methods. The fiber melting temperature range was also defined. The investigations have been made on the basis the of thermal gravimetric analysis and differential thermal gravimetric analysis curves determined at various heating speeds, in the temperature range from 100°-600°C. It was found that thermal stability of polypropylene fiber is reduced by light treatment (i.e., fiber softens and melts at a lower temperature). Activation energy values determined for thermal decomposition of the fiber samples exposed to the influence of light are considerably higher than the values determined on unexposed samples. The decomposition process of aged fiber is more complex and occurs in a larger temperature range. Both the methods used show almost similar results.