Resistance to UV Radiation

A series of accelerated exposure tests was performed to investigate the effect of UV radiation on the coating material, the stress-strain state in tension and shear, and the color fastness of the coating material. The tests were carried out according to ASTM Standards ASTM D4329, G151 and G154. 

The UV light source was the UVA 340 lamp with spectral characteristics in a range of wavelengths corresponding to a spectrum of sunlight, and an emission peak of 343 nm. Typical lamp irradiance is 0.77 W/m2/nm. 

The lamp was set in the test chamber, which was equipped with a temperature and radiometric control system. The specified uninsulated black panel sensor was used for measurement of temperature. The sensor was mounted on a support within the specimen exposure area so that it received the same radiation and cooling conditions as the test samples. The ambient temperature at a distance of 150 mm from the chamber was maintained within the 18°C-23°C range. Ventilation and air conditioning systems eliminated superfluous heat and humidity. 

Samples of two types were made Type KB (crack-resistant) for concrete and ceramic substrates, and type KM (anticorrosive) for metal and other substrates. Three series of various color samples (white, yellow, and green) were submitted on three substrate samples in each test series. All samples had a rectangular form, and measured 120 x 120 x 0.5 mm in size. Samples were fixed on a contour in special stainless steel frames, and used an aluminum substrate with a thickness of 0.635 mm. Samples were exposed in a vertical orientation. 

The UV test exposure procedure corresponded to the cycle A [4] and provided an 8-hour UV exposure test with uninsulated black panel temperature control at 60 3°C. 

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Other Properties. Polyester fibers have good resistance to uv radiation although prolonged exposure weakens the fibers (47,51). PET is not affected by iasects or microorganisms and can be designed to kill bacteria by the iacorporation of antimicrobial agents (19). The oleophilic surface of PET fibers attracts and holds oils. Other PET fiber properties can be found ia the Hterature (47,49). 

Ethylene-vinyl acetate EVAs (in the polyolefin family) have exceptional barrier properties, good clarity and gloss, stress-crack resistance, low temperature toughness/retains flexibility, adhesion, resistance to UV radiation, etc. They have low resistance to heat and solvents. 

EVA shows a good resistance to UV radiation. Further, it has a good clarity. 

Many polyphosphazenes form strong films and membranes when solutions are spread on a flat surface and the solvent is allowed to evaporate. Some of these films have special properties such as resistance to UV radiation, and are thus of interest as coatings for solar cells, aircraft, or space craft. The polymer [NP(OCH2CF3)2] and related mixed-substituent derivatives have been studied from this viewpoint.1... 

Vinyl fluoride is an interesting monomer, precursor of PVF or Tedlar (produced by the Dupont Company), known for its good resistance to UV radiation. But in telomerisation, the most intensive work was achieved by Tedder and Walton who used several telogens exhibiting cleavable C-Br or C-I bonds, under UV at various temperatures (Table 17). Their surveys were mostly devoted to the obtaining of monoadduct and to their kinetics (e.g., determination of relative rate constants of formation of normal and reverse isomers and of Arrhenius parameters). 

Inert to almost all chemicals and solvents Reduction of the coefficient of friction Improvement of wear characteristics Resistance to UV radiation and weadiering Improvement in nonstick and release properties Increase of mb resistance... 

BPs are used not only in specialized cosmetic preparations for skin protection against the carcinogenic effect of UV radiation they are also added to pharmaceuticals and many everyday products such as body lotions, shampoos, bubble baths, and hair sprays. These compounds are used for the packaging of synthetic materials in order to extend the shelf life of stored products that could be affected by the influence of sunlight. Other application areas are tire additives, castings, coatings, pigments, textiles, and other products, to increase their resistance to UV radiation [49,64,73,74]. 

The Intercide OBF microbiocides are based on the active ingredient 2-n-octyl-4-isothiazolin-3-one (OIT). The products are effective fungicides which are widely used in paints and coatings. Characteristics and applications are described for Intercide grades OBF-8-DINP, and OBF-8-ED6. OIT is highly compatible with PVC and offers advantages over OBPA in terms of resistance to UV radiation. 

Possibility to design eye-catching, durable color solutions (according to the RAL-colors chart do not fade for a very long period of time—resistant to UV radiation)... 

The UV-induced generation of cyclobutane dimers is greatly dependent on double-helix conformational factors. In dormant spores of various bacillus species, for example, a group of small, acid-soluble proteins specifically bind to DNA, thereby enforcing a particular conformation that is unfavorable for the formation of harmful cyclobutane-type lesions. As a consequence, these dormant spores are much more resistant to UV radiation than the corresponding grooving cells, in which DNA strands reassume conformations favorable for the formation of cyclobutane-type lesions [31]. 

PROPERTIES OF SPECIAL INTEREST Thermal stability, low temperature performance and minimal temperature effect. Good resistance to UV radiation. Excellent release properties and surface activity. High permeability to gases. Good damping behavior, antifriction and lubricity. Hydrophobic and physiological inertness. 

Sericin biopolymer, an amorphous glue-like substance, is made up of 18 amino acids most of which 70% have a polar terminal functional group, such as -OH, -COOH, and -NH2 groups, which are responsible for its solubility as well as water absorption and desorption [72, 143]. Biocompatibility, blodegradablllty, excellent antimicrobial activity, resistance to UV radiation, and moisture absorption ability inherent properties along with its availability have facilitated its potential applications in different fields, including textiles [72, 77,143]. 

Liquid crystal polymers (LCP) are highly ordered crystalline aromatic polyesters with high mechanical strength. They are exceptionally inert, having very high thermal and chemical stability, are highly resistant to UV radiation and are inherently flame retardant and antistatic. 

The current concentration on the use of synthetic instead of natural fibrous materials stems from the desire to standardize the physical and mechanical characteristics of materials and to adapt them to the demands of the technical designers and users of membrane constructions. Above all, characteristics such as mechanical firmness, flexibility, workability, durability, resistance to UV radiation and chemicals, dirt resistance and cleaning behaviour, flammability, moisture stability and environmental compatibility determine the costs and therefore the choice of materials. 

Uncoated fibreglass fabrics are not, without special treatment, sufficiently resistant to UV radiation and the deposition of dirt. Efforts are being made to reduce these disadvantages with coatings of PTFE or silicone, which will be discussed in later sections. 

The fibre must also be able to withstand prolonged exposure to sunlight, specifically irradiation by UV light. The twin considerations of thermomechanical stability up to 200 °C and resistance to UV radiation do rule out several types of commodity fibre. These fibres include most natural fibres, as well as commercial polyolefin and acrylic fibres, all of which melt or begin to decompose below 200 °C. Nevertheless, polyethylene terephthalate (PET) fibres are potentially suitable substrates they melt at 260-270 °C and exhibit good stability to UV radiation [6]. They are also commercially... 

When 2% silicone is added to acetal copolymer, as an internal lubricant, the compound has good rigidity and toughness, creep resistance, low coefficient of friction, and resistance to most solvents but it also has disadvantages associated with unmodified acetal copolymer, high mold shrinkage, and poor resistance to UV radiation [14]. Typical thermal properties for 2% silicone lubricated acetal copolymer include of 190 to 210°C... 

Acetal homopolymer with PTFE lubricant shows good solvent resistance typical of standard-grade homopolymer, good hydrolytic stability, and lower coefficient of friction than unmodified grades. Disadvantages include poor resistance to UV radiation, acids, and bases and lower stiffness, toughness, and strength properties compared with unmodified acetal homopolymer [12]. Thermal properties include a of 210 to 230°C (410... 

Though not completely resistant to UV radiation, being a linear aliphatic polyester, PHA has been reported to have better resistance to UV radiation than polypropylene. Due to this property, a PHA (reported as a PHA-I6001 from Metabolix with a crystallinity of 25%) was blended with PVC (a UV sensitive polymer) to provide this latter higher UV resistance without promoting biodegradation. PHA, being miscible with PVC, did not lead to phase... 

Polyphosphazenes are a diverse class of polymers with an inorganic backbone of phosphorus and nitrogen atoms. Because these polymers have two substituents at each phosphorus, it is possible to widely vary the properties of this polymer system by simple changes in these substituents. In fact, several hundred such polymers are known and their potential applications include materials that are flame retardant, resistant to UV radiation and chemicals, semiconductors, conductors, insulators, water soluble, biologically inert or active, etc. (1,2)... 

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