ECOLOGY and COATINGS

Post 359 – by Gautam Shah 

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Coatings (Paint, Varnish, etc.) consist of organic as well as inorganic substances. Both the categories of materials can be hazardous at several levels such as: production, application, curing or drying, functional use, and disposal level.

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At production level the handling and use of certain raw materials can be hazardous. Typically handling of extenders and pigments can pose air-bourne particle spread. Some of these silica containing materials are toxic and carcinogenic and not eco-friendly. Resins (amino) with styrene and formaldehyde are carcinogenic. Solvents are known fire prone materials. At application level, the primary hazard occurs, due to high amounts of volatile organic content going into air. Its vapours or odours are noxious, allergic and unpleasant. The odour suppressants added to coatings are not necessarily benign. At application level, old coated surfaces are rubbed or scrapped, the particulate matter of which causes air pollution and the constituents are often unfamiliar.

Aerosols cause high level of air pollution

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Post application, the wearing surfaces and peel-off cause, dust pollution. Some of the plastic materials continue to deteriorate, evolving pollutants. Coatings used on kitchen shelves, utensils, equipments cause contamination. Accidental high heating and fire scorch a coating. Planned removal of coating by sanding and chemical etchings (paint scrubbers or removers) can also leave unwanted residual products. Disposal of coated items by sawing, forced removal, hammering, chiselling, sanding, scrapping, etc. can desecrate the environment.

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Prolonged or high intensity exposure to paint and paint fumes can affect three main organs, lungs, kidney and lever. These manifest as headache, allergies and asthmatic reactions, irritation of skin and eyes, burning in nose, airways, urinary tracts.

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The trend world over is to design entities with their own or integrated surfaces. A variety of metal and polymer surface treatments are available that molecularly change the quality of the surface. Such `surface systems‘, rather than `surface finishes‘ often do not require any application of foreign substances. A variety of single or a combination of treatments like temperature, radiation, sonar, mechanical finishing, stress induction and relief, cathodic protection etc. can eliminate organic coating systems. Such surfaces do not have any applied finishes, but rather have a generated finish.

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There are many inorganic coating systems that are akin to metallizing systems. In such systems the role of medium is to carry and spread the pigment and other substances. On baking or firing the medium is evaporated or burnt off leaving metallic or alloying compounds on the surface. Such substances are generally heat or flame cured to cross links with the substrate material.

Volatile Organic Compounds VOCs

VOCs are volatile solid or liquid organic compounds that evaporate readily due to high vapour pressure (volatility or low boiling point) at ordinary room temperature. VOCs are of many varieties, like natural or man-made materials. Most of the scents or odours have VOC components.

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There are broadly two classes of VOCs, Anthropogenic (caused or produced by humans), are in low concentrations but with cumulative or long-term health effects, and Biogenic (caused through biological processes). VOCs. Anthropogenic, A-VOCs constitute substantial hazards in Urban areas. B-VOCs occur everywhere. Some VOCs are labelled as carcinogenic (cancer causing). Indoor environments may not have very high emissions of VOCs, but the concentrations can reach to be 2 to 5 times (or even more) than in outdoor air. Indoor environments of new buildings generate large amounts of VOC in the immediate time period. VOC concentration in an indoor environment during winter is 3 to 4 times higher than during the summer. High VOC levels in indoor areas are also due to the poor dilution of air resulting from barriers and resulting in air stagnancy.

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VOCs exposure mainly occurs through inhalation and to a smaller extent through skin or touch. Health hazards include, respiratory and allergic effects resulting in burning sensation in eye, nose, throat, nausea, fatigue, dizziness, loss of coordination and damage to the liver, kidney, and central nervous system.Some major sources of man-made VOCs are coatings, especially paints and other coatings (solvents, waterproofing compounds, gums, sealants, paints, thinners, paint removers, cleaning agents, soaps, cosmetics, rubber goods ). Water-based coatings produced from gums, casein, egg-whites etc. and with cementious compounds like lime, gypsum, etc., water emulsified, polymer paints help meet the ecological concerns for VOCs.

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Managing the VOCs

  • Avoid use of VOC products.
  • Reduce exposure to VOCs.
  • Increase indoor ventilation while applying such products.
  • Purchase and consume entire mass of VOC products as immediately as possible.
  • Isolate areas of high VOC such as application and storage rooms, if required exploit means of passive micro ventilation.
  • Never mix household care products unless permitted.
  • Some VOCs, such as styrene and limonene, can react with nitrogen oxides or with ozone to produce new oxidation products and secondary aerosols.

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