Rubber, pollution effect

Materials The damage that air pollutants can do to some materials is well known ozone in photochemical smog cracks rubber, weakens fabrics, and fades dyes hydrogen sulfide tarnishes silver smoke dirties laundry acid aerosols ruin nylon hose. Among the most important effects are discoloration, corrosion, the soiling of goods, and impairment of visibility. 

Biopolymers have diverse roles to play in the advancement of green nanotechnology. Nanosized derivatives of polysaccharides like starch and cellulose can be synthesized in bulk and can be used for the development of bionanocomposites. They can be promising substitutes of environment pollutant carbon black for reinforcement of rubbers even at higher loadings (upto SOphr) via commercially viable process. The combined effect of size reduction and organic modification improves filler-matrix adhesion and in turn the performance of polysaccharides. The study opens up a new and green alternative for reinforcement of rubbers. 

Effects on materials vary widely, depending on the composition of the material and on the particular air pollutant. For example, rubber products and polymers are especially susceptible to 03, whereas metals such as iron are particularly sensitive to acids. Indeed, Haa-gen-Smit and co-workers (1959) used the cracking of rubber by 03 to measure its concentration in air in the early days of photochemical air pollution. A detailed description of the effects of air pollutants on various types of materials is found in the article by Graedel and McGill (1986). 

Materials and Structures. Building materials have become soiled and blackened by smoke, and damage by chemical attack from acid gases in the air has led to the deterioration of many marble statues in western Europe. Metals are also affected by air pollution for example, S02 causes many metals to corrode at a faster rate. Ozone is known to oxidize rubber products, and one of the effects of Los Angeles smog is cracking of rubber tires. Fabrics, leather, and paper are also affected by S02 and sulfuric acid, causing them to crack, become brittle, and tear more easily. 

Ozone is a major atmospheric pollutant in urban areas. In addition to its damaging effect on lung tissue and even on exposed skin surfaces, ozone attacks the rubber of tires, causing them to become brittle and crack. But in the stratosphere, where ozone absorbs much of the short-wavelength UV radiation from the sun, it provides a vital protective shield for life forms on earth. 

These few examples show the desperate need for further research and assessment in the chemistry and all aspects of air pollution. One might question whether we have knowledge of all urban sources of hydrocarbons that are important to atmospheric interactions. Does all rubber dust from automotive tires remain as dust What is the contribution of asphalt roadways to atmospheric hydrocarbons Is the contribution from such unassessed and other unknown anthropogenic sources sufficient in itself to account for health-damaging levels of ozone These and other questions require immediate attention if we are to realize the goal of effective pollution control. 

Cycles of pollution and cleaning of silicone rubber samples show that hydrophobicity transfer is a dynamic process that depends on the amount of freely diffusible fluid components. It seems probable that the transfer effect is present during the whole lifetime of a silicone rubber for high-voltage insulators. 

Fifty percent of the total energy needed to produce plastic materials is used in the polymerization process. Thus at first sight, it seems sensible to re-use plastic and rubber waste materials (8 ). But Re-use processes have a negative influence on the macro-molecular structure which is mainly a chain depolymerisation effect (9 ). Therefore Re-use by itself is not a satisfactory process. In addition,a large proportion of the plastic waste is polluted and mixed with other types of waste so that Re-use is impossible. 

Ozone is an important component of the upper atmosphere, where it screens out ultraviolet radiation and so protects us from the effects of these high-energy rays. For this reason, depletion of stratospheric ozone is a major scientific concern, -xc (Section 18.2) In the lower atmosphere, ozone is considered an air pollutant and is a major constituent of smog. <3 (Section 18.2) Because of its oxidizing power, ozone damages living systems and structural materials, especially rubber. 

The term antiozonant denotes any additive that protects rubber against ozone deterioration. Most frequently, the protective effect results from a reaction with ozone, in which case the term used is chemical antiozonant. Ozone is generated naturally by electrical discharge and also by solar radiation in the stratosphere. These sources produce ground-level ozone concentrations of 1-5 parts per hundred million (pphm). In urban environments, however, ozone reaches much higher levels, up to 25 (pphm) due to the ultraviolet photolysis of pollutants. Only a few parts per hundred million of ozone in air can cause rubber cracking, which may destroy the usefulness of elastomer products. Some desirable properties of an antiozonant additive are as follows ... 

---