Powder Coating

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Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat or with ultraviolet light. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminium extrusions, drum hardware, automobiles, and bicycle frames. Advancements in powder coating technology like UV curable powder coatings allow for other materials such as plastics, composites, carbon fiber, and MDF (medium-density fibreboard) to be powder coated due to the minimum heat and oven dwell time required to process these components.

Because powder coating does not have a liquid carrier, it can produce thicker coatings than conventional liquid coatings without running or sagging, and powder coating produces minimal appearance differences between horizontally coated surfaces and vertically coated surfaces. Because no carrier fluid evaporates away, the coating process emits few volatile organic compounds (VOC). Finally, several powder colors can be applied before curing them all together, allowing color blending and bleed special effects in a single layer.

While it is relatively easy to apply thick coatings that cure to smooth, texture-free coating, it is not as easy to apply smooth thin films. As the film thickness is reduced, the film becomes more and more orange peeled in texture due to the particle size and glass transition temperature (Tg) of the powder.

Most powder coatings have a particle size in the range of 2 to 50 μm, a softening temperature Tg around 80 °C, a melting temperature around 150 °C, and are cured at around 200 °C for a minimum of 10 minutes to 15 minutes (exact temperatures and times may depend on the thickness of the item being coated). For such powder coatings, film build-ups of greater than 50 μm may be required to obtain an acceptably smooth film.

Advantages of Powder Coating :

  1. The Color is Thicker. Paint technique powder coating produces colour that are more stable and thicker than other techniques. The thickness reaches 350 microns, while the thickness of oil paint is generally arround 30 – 40 microns.
  2. Hard Surface. In addition to the bold colour, the surface will be harder, thus making the metal or metal protection more scratch resistant.
  3. Stronger Adhesive Properties. The strong adhesive properties cause the powder to blend better with the metal. The chemical pre-treatment and the bake oven process up to 200 degrees Celcius resulted in the melting process of the powder being more integrated with the media.
  4. Closes The Pores Perfectly. The Powder Coating process is even the colour is thick. It will make the pores of the object completely closed. In contrast to oil paint, for a certain period of time there will be small cracks that are invisible to the nake eye, where over time these cracks can become a pathway for water, dew or steam to enter the pores which over time can trigger rust.
  5. Efficient. Powder coating is considered more efficient and economical compared to other techniques. The spread of colour can save the use of paint material directly.
  6. Environmentally Friendly. Media that uses powder coating is safe for health and very environmentally friendly. There are no special ingredients to dissolve the paint, which can peel off the paint and cause environmental waste. Even though the paints material is still in the form of wet powder, it does not cause a strong odor.
  7. Safety. Powder paint ingredients are safe for health, both for the respiratory, tract and skin if they are exposed to direct contamination. However, the use of security devices must still be necessary to reduce unwanted risks.
  8. Good Quality. The powder coating process at high temperatures and the rust removal techniques used before hand will create a good quality and corrosion resistant result. Objects protected with powder coating paint can withstand heat and rain far better than ordinary paint. The durability of powder coating can be up to 10 years.

Weaknesses of Powder Coating :

  1. It is difficult to find other colour dimensions that are more suitable, for example for this type of mettalic paint
  2. Can only be applied to Iron, Allumunium or metal. Can’t be used for rubber materials and can only be touched after the paint is dry
  3. The object to be painted must be completely sterile and free of seals of rubber because it will be heated to a temperature of 220 °C.

 

Carbonization

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Carbonization is the complex process of concentrating and purifying carbon by denaturing organic matter with heat in the presence of little to no oxygen.

Carbonization is a pyrolytic reaction, therefore, is considered a complex process in which many reactions take place concurrently such as dehydrogenation, condensation, hydrogen transfer and isomerization.

Carbonization differs from coalification in that it occurs much faster, due to its reaction rate being faster by many orders of magnitude.

For the final pyrolysis temperature, the amount of heat applied controls the degree of carbonization and the residual content of foreign elements. For example, at T ~ 1200 K the carbon content of the residue exceeds a mass fraction of 90 wt.%, whereas at T ~ 1600 K more than 99 wt.% carbon is found. Carbonization is often exothermic, which means that it could in principle be made self-sustaining and be used as a source of energy that does not produce carbon dioxide.

The carbonization of wood in an industrial setting usually requires a temperature above 280 °C, which frees up energy and hence this reaction is said to be exothermic. This carbonization, which can also be seen as a spontaneous breakdown of the wood, continues until only the carbonised residue called charcoal remains. Unless further external heat is provided, the process stops and the temperature reaches a maximum of about 400 °C. This charcoal, however, will still contain appreciable amounts of tar residue, together with the ash of the original wood.

The gas produced by carbonization has a high content of carbon monoxide which is poisonous when breathed. Therefore, when working around the kiln or pit during operation and when the kiln is opened for unloading, care must be taken that proper ventilation is provided to allow the carbon monoxide, which is also produced during unloading through spontaneous ignition of the hot fuel, to be dispersed.

The tars and smoke produced from carbonization, although not directly poisonous, may have long-term damaging effects on the respiratory system. Housing areas should, where possible, be located so that prevailing winds carry smoke from charcoal operations away from them and batteries of kilns should not be located in close proximity to housing areas.

Wood tars and pyroligneous acid can be irritant to skin and care should be taken to avoid prolonged skin contact by providing protective clothing and adopting working procedures which minimize exposure.

The tars and pyroligneous liquors can also seriously contaminate streams and affect drinking water supplies for humans and animals. Fish may also be adversely affected. Liquid effluents and waste water from medium and large scale charcoal operations should be trapped in large settling ponds and allowed to evaporate so that this water does not pass into the local drainage system and contaminate streams. Kilns and pits, as distinct from retorts and other sophisticated systems, do not normally produce liquid effluent – the by-products are mostly dispersed into the air as vapours.

Coating

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A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Powder coatings.

Paints and lacquers are coatings that mostly have dual uses of protecting the substrate and being decorative, although some artists paints are only for decoration, and the paint on large industrial pipes is for preventing corrosion and identification e.g. blue for process water, red for fire-fighting control etc. Functional coatings may be applied to change the surface properties of the substrate, such as adhesion, wettability, corrosion resistance, or wear resistance. In other cases, e.g. semiconductor device fabrication (where the substrate is a wafer), the coating adds a completely new property, such as a magnetic response or electrical conductivity, and forms an essential part of the finished product.

A major consideration for most coating processes is that the coating is to be applied at a controlled thickness, and a number of different processes are in use to achieve this control, ranging from a simple brush for painting a wall, to some very expensive machinery applying coatings in the electronics industry. A further consideration for ‘non-all-over’ coatings is that control is needed as to where the coating is to be applied. A number of these non-all-over coating processes are printing processes. Many industrial coating processes involve the application of a thin film of functional material to a substrate, such as paper, fabric, film, foil, or sheet stock. If the substrate starts and ends the process wound up in a roll, the process may be termed “roll-to-roll” or “web-based” coating.

Coatings are not just designed to be aesthetically pleasing and for decorative purposes, but also have other functions. Sometimes a coating can be both decorative and have a specific function. An example would be the coating of a pipe carrying water for a fire suppression system that is coated with a red (for identification) anticorrosion paint to reduce degradation. In fact, most surface coatings or paints are to some extent protecting the substrate e.g. general maintenance coatings/paints for metals and concrete. The decorative aspect of coatings is not just to impart a specific color, but also to create a particular reflective property such as high gloss, satin or flat/matt appearance. Some coatings though, are specifically designed to be very chemically resistant.

A major use of coatings is to protect metal, and these are generally known as anticorrosion coatings. This use includes preserving machinery, equipment and structures. Automobiles have improved in design over the years. Most are still made of metal for crashworthiness. The external coating and the underbody are coated.

Coatings are also used to seal the surface of concrete. This would include Seamless polymer/resin flooring, bund wall/containment lining, Waterproofing and damp proofing of concrete walls, and concrete bridge decks.

Roof coatings have been developed and improved over the years. They are designed primarily for waterproofing and also sun reflection to help keep a building cool. They tend to be elastomeric to allow for movement of the roof without cracking the coating membrane.

The coating, sealing and waterproofing of wood has been going on since biblical times, with God commanding Noah to build an ark and then coat it. Wood was and is a key material of construction since ancient times so its preservation by coating has received much attention. Efforts to improve the performance of wood coatings continues.

Coatings are used to alter tribological properties and wear characteristics. Other functions of coatings include :

  • UV coatings
  • Anti-reflective coatings for example on spectacles.
  • Non-stick PTFE coated cooking pots/pans.
  • Optical coatings are available that alter optical properties of a material or object.
  • Anti-Friction, Wear and Scuffing Resistance Coatings for Rolling-element bearings
  • Coatings that alter or have magnetic, electrical or electronic properties.
  • Antimicrobial coatings.
  • Anti-fouling coatings
  • Flame retardant coatings.

Coating analysis and characterization

Numerous destructive and non-destructive evaluation (NDE) methods exist for characterizing coatings. The most common destructive method is microscopy of a mounted cross-section of the coating and its substrate. The most common non-destructive techniques include ultrasonic thickness measurement, X-ray fluorescence (XRF), X-Ray diffraction (XRD) and micro hardness indentation. X-ray photoelectron spectroscopy (XPS) is also a classical characterization method to investigate the chemical composition of the nanometer thick surface layer of a material. Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX, or SEM-EDS) allows to visualize the surface texture and to probe its elementary chemical composition. Other characterization methods include transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning tunneling microscope (STM), and Rutherford backscattering spectrometry (RBS). Various methods of Chromatography are also used, as well as thermogravimetric analysis.

Thermal Cleaning

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Pyrolysis is also used for thermal cleaning, an industrial application to remove organic substances such as polymers, plastics and coatings from parts, products or production components like extruder screws, spinnerets and static mixers. During the thermal cleaning process, at temperatures between 310 C° to 540 C° (600 °F to 1000 °F), organic material is converted by pyrolysis and oxidation into volatile organic compounds, hydrocarbons and carbonized gas. Inorganic elements remain.

Several types of thermal cleaning systems use pyrolysis:

  • Molten Salt Baths belong to the oldest thermal cleaning systems; cleaning with a molten salt bath is very fast but implies the risk of dangerous splatters, or other potential hazards connected with the use of salt baths, like explosions or highly toxic hydrogen cyanide gas.
  • Fluidized Bed Systems use sand or aluminium oxide as heating medium; these systems also clean very fast but the medium does not melt or boil, nor emit any vapors or odors; the cleaning process takes one to two hours.
  • Vacuum Ovens use pyrolysis in a vacuum avoiding uncontrolled combustion inside the cleaning chamber; the cleaning process takes 8 to 30 hours.
  • Burn-Off Ovens, also known as Heat-Cleaning Ovens, are gas-fired and used in the painting, coatings, electric motors and plastics industries for removing organics from heavy and large metal parts.

Ethylene and Semiconductors

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Ethylene

Pyrolysis is used to produce ethylene, the chemical compound produced on the largest scale industrially (>110 million tons/year in 2005). In this process, hydrocarbons from petroleum are heated to around 600 °C (1,112 °F) in the presence of steam; this is called steam cracking. The resulting ethylene is used to make antifreeze (ethylene glycol), PVC (via vinyl chloride), and many other polymers, such as polyethylene and polystyrene.

Semiconductors

The process of metalorganic vapour-phase epitaxy (MOCVD) entails pyrolysis of volatile organometallic compounds to give semiconductors, hard coatings, and other applicable materials. The reactions entail thermal degradation of precursors, with deposition of the inorganic component and release of the hydrocarbons as gaseous waste. Since it is an atom-by-atom deposition, these atoms organize themselves into crystals to form the bulk semiconductor. Silicon chips are produced by the pyrolysis of silane:

SiH4 → Si + 2 H2.

Gallium arsenide, another semiconductor, forms upon co-pyrolysis of trimethylgallium and arsine.

Methane Pyrolysis for Hydrogen

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Methane pyrolysis is a industrial process for “turquoise” hydrogen production from methane by removing solid carbon from natural gas. This one-step process produces hydrogen in high volume at low cost (less than steam reforming with carbon sequestration). Only water is released when hydrogen is used as the fuel for fuel-cell electric heavy truck transportation, gas turbine electric power generation, and hydrogen for industrial processes including producing ammonia fertilizer and cement.

Methane pyrolysis is the process operating around 1065 °C for producing hydrogen from natural gas that allows removal of carbon easily (solid carbon is a byproduct of the process). The industrial quality solid carbon can then be sold or landfilled and is not released into the atmosphere, avoiding emission of greenhouse gas (GHG) or ground water pollution from a landfill. Power for process heat consumed is only one seventh of the power consumed in the water electrolysis method for producing hydrogen.

Liquid and Gaseous Biofuels

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Pyrolysis is the basis of several methods for producing fuel from biomass, i.e. lignocellulosic biomass. Crops studied as biomass feedstock for pyrolysis include native North American prairie grasses such as switchgrass and bred versions of other grasses such as Miscantheus giganteus. Other sources of organic matter as feedstock for pyrolysis include greenwaste, sawdust, waste wood, leaves, vegetables, nut shells, straw, cotton trash, rice hulls, and orange peels. Animal waste including poultry litter, dairy manure, and potentially other manures are also under evaluation. Some industrial byproducts are also suitable feedstock including paper sludge, distillers grain, and sewage sludge.

In the biomass components, the pyrolysis of hemicellulose happens between 210 and 310 °C. The pyrolysis of cellulose starts from 300–315 °C and ends at 360–380 °C, with a peak at 342–354 °C. Lignin starts to decompose at about 200 °C and continues until 1000 °C.

Synthetic diesel fuel by pyrolysis of organic materials is not yet economically competitive. Higher efficiency is sometimes achieved by flash pyrolysis, in which finely divided feedstock is quickly heated to between 350 and 500 °C (660 and 930 °F) for less than two seconds.

Syngas is usually produced by pyrolysis.

The low quality of oils produced through pyrolysis can be improved by physical and chemical processes, which might drive up production costs, but may make sense economically as circumstances change.

There is also the possibility of integrating with other processes such as mechanical biological treatment and anaerobic digestion. Fast pyrolysis is also investigated for biomass conversion. Fuel bio-oil can also be produced by hydrous pyrolysis.

Coke, Carbon, Charcoals, and Chars

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Carbon and carbon-rich materials have desirable properties but are nonvolatile, even at high temperatures. Consequently, pyrolysis is used to produce many kinds of carbon; these can be used for fuel, as reagents in steelmaking (coke), and as structural materials.

Charcoal is a less smoky fuel than pyrolyzed wood. Some cities ban, or used to ban, wood fires; when residents only use charcoal (and similarly-treated rock coal, called coke) air pollution is significantly reduced. In cities where people do not generally cook or heat with fires, this is not needed. In the mid-20th century, “smokeless” legislation in Europe required cleaner-burning techniques, such as coke fuel and smoke-burning incinerators as an effective measure to reduce air pollution.

A blacksmith’s forge, with a blower forcing air through a bed of fuel to raise the temperature of the fire. On the periphery, coal is pyrolyzed, absorbing heat; the coke at the center is almost pure carbon, and releases a lot of heat when the carbon oxidizes.
Typical organic products obtained by pyrolysis of coal (X = CH, N).

The coke-making or “coking” process consists of heating the material in “coking ovens” to very high temperatures (up to 900 °C or 1,700 °F) so that the molecules are broken down into lighter volatile substances, which leave the vessel, and a porous but hard residue that is mostly carbon and inorganic ash. The amount of volatiles varies with the source material, but is typically 25–30% of it by weight. High temperature pyrolysis is used on an industrial scale to convert coal into coke. This is useful in metallurgy, where the higher temperatures are necessary for many processes, such as steelmaking. Volatile by-products of this process are also often useful, including benzene and pyridine. Coke can also be produced from the solid residue left from petroleum refining.

The original vascular structure of the wood and the pores created by escaping gases combine to produce a light and porous material. By starting with a dense wood-like material, such as nutshells or peach stones, one obtains a form of charcoal with particularly fine pores (and hence a much larger pore surface area), called activated carbon, which is used as an adsorbent for a wide range of chemical substances.

Biochar is the residue of incomplete organic pyrolysis, e.g., from cooking fires. It is a key component of the terra preta soils associated with ancient indigenous communities of the Amazon basin. Terra preta is much sought by local farmers for its superior fertility and capacity to promote and retain an enhanced suite of beneficial microbiota, compared to the typical red soil of the region. Efforts are underway to recreate these soils through biochar, the solid residue of pyrolysis of various materials, mostly organic waste.

Carbon fibers produced by pyrolyzing a silk cocoon. Electron micrograph, scale bar at bottom left shows 100 μm.Carbon fibers are filaments of carbon that can be used to make very strong yarns and textiles. Carbon fiber items are often produced by spinning and weaving the desired item from fibers of a suitable polymer, and then pyrolyzing the material at a high temperature (from 1,500–3,000 °C or 2,730–5,430 °F). The first carbon fibers were made from rayon, but polyacrylonitrile has become the most common starting material.

Pyrolysis is the reaction used to coat a preformed substrate with a layer of pyrolytic carbon. This is typically done in a fluidized bed reactor heated to 1,000–2,000 °C or 1,830–3,630 °F. Pyrolytic carbon coatings are used in many applications, including artificial heart valves.

Caramelization

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Pyrolysis has many applications in food preparation.

Caramelization is the pyrolysis of sugars in food (often after the sugars have been produced by the breakdown of polysaccharides). The food goes brown and changes flavor. The distinctive flavors are used in many dishes; for instance, caramelized onion is used in French onion soup. The temperatures needed for caramelization lie above the boiling point of water. Frying oil can easily rise above the boiling point. Putting a lid on the frying pan keeps the water in, and some of it re-condenses, keeping the temperature too cool to brown for longer time.

Reaction of Caramelization :  

Pyrolysis of food can also be undesirable, as in the charring of burnt food (at temperatures too low for the oxidative combustion of carbon to produce flames and burn the food to ash).

Pyrolysis

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The word is Pyrolysis coined from the Greek-derived elements pyro “fire”, “heat”, “fever” and lysis “separating”.

The Pyrolysis (or devolatilization) Process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition.

In this treatment, material is exposed to high temperature, and in the absence of oxygen goes through chemical and physical separation into different molecules. The decomposition takes place thanks to the limited thermal stability of chemical bonds of materials, which allows them to be disintegrated by using the heat.

Thermal decomposition leads to the formation of new molecules. This allows to receive products with a different, often more superior character than original residue. Pyrolysis products always produce solid (charcoal, biochar), liquid and non-condensable gases (H2, CH4, CnHm, CO, CO2 and N). As the liquid phase is extracted from pyrolysis gas only during it’s cooling down, in some applications, these two streams can be used together when providing hot syngas directly to the burner or oxidation chamber.

Pyrolysis is one of the various types of chemical degradation processes that occur at higher temperatures (above the boiling point of water or other solvents). It differs from other processes like combustion and hydrolysis in that it usually does not involve the addition of other reagents such as oxygen (O2, in combustion) or water (in hydrolysis). During the pyrolysis, a particle of material is heated up from the ambient to defined temperature. Pyrolysis produces solids (char), condensable liquids (tar), and uncondensing/permanent gasses.

The process is used heavily in the chemical industry, for example, to produce ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood, to produce coke from coal. It is used also in the conversion of natural gas (primarily methane) into hydrogen gas and solid carbon char, recently on an industrial scale. Aspirational applications of pyrolysis would convert biomass into syngas and biochar, waste plastics back into usable oil, or waste into safely disposable substances.

Specific types of pyrolysis include:

  • Carbonization, the complete pyrolysis of organic matter, which usually leaves a solid residue that consists mostly of elemental carbon.
  • Methane pyrolysis, the direct conversion of methane to hydrogen fuel and separable solid carbon, sometimes using molten metal catalysts.
  • Hydrous pyrolysis, in the presence of superheated water or steam, producing hydrogen and substantial atmospheric carbon dioxide.
  • Dry distillation, as in the original production of sulfuric acid from sulfates.
  • Destructive distillation, as in the manufacture of charcoal, coke and activated carbon.
  • Caramelization of sugars.
  • High-temperature cooking processes such as roasting, frying, toasting, and grilling.
  • Charcoals burning, the production of charcoal.
  • Tar production by destructive distillation of wood in tar kilns.
  • Cracking of heavier hydrocarbons into lighter ones, as in oil refining.
  • Thermal depolymerization, which breaks down plastics and other polymers into monomers and oligomers.
  • Ceramization involving the formation of polymer derived ceramics from preceramic polymers under an inert atmosphere.
  • Catagenesis, the natural conversion of buried organic matter to fossil fuels.
  • Flash vacuum pyrolysis, used in organic synthesis.

Pyrolysis generally consists in heating the material above its decomposition temperature, breaking chemical bonds in its molecules. The fragments usually become smaller molecules, but may combine to produce residues with larger molecular mass, even amorphous covalent solids.

In many settings, some amounts of oxygen, water, or other substances may be present, so that combustion, hydrolysis, or other chemical processes may occur besides pyrolysis proper. Sometimes those chemicals are added intentionally, as in the burning of firewood, in the traditional manufacture of charcoal, and in the steam cracking of crude oil.

Conversely, the starting material may be heated in a vacuum or in an inert atmosphere to avoid chemical side reactions (such as combustion or hydrolysis). Pyrolysis in a vacuum also lowers the boiling point of the byproducts, improving their recovery.

When organic matter is heated at increasing temperatures in open containers, the following processes generally occur, in successive or overlapping stages:

  • Below about 100 °C, volatiles, including some water, evaporate. Heat-sensitive substances, such as vitamin C and proteins, may partially change or decompose already at this stage.
  • At about 100 °C or slightly higher, any remaining water that is merely absorbed in the material is driven off. This process consumes a lot of energy, so the temperature may stop rising until all water has evaporated. Water trapped in crystal structure of hydrates may come off at somewhat higher temperatures.
  • Some solid substances, like fats, waxes, and sugars, may melt and separate.
  • Between 100 and 500 °C, many common organic molecules break down. Most sugars start decomposing at 160–180 °C. Cellulose, a major component of wood, paper, and cotton fabrics, decomposes at about 350 °C. Lignin, another major wood component, starts decomposing at about 350 °C, but continues releasing volatile products up to 500 °C. The decomposition products usually include water, carbon monoxide CO and/or carbon dioxide CO2, as well as a large number of organic compounds. Gases and volatile products leave the sample, and some of them may condense again as smoke. Generally, this process also absorbs energy. Some volatiles may ignite and burn, creating a visible flame. The non-volatile residues typically become richer in carbon and form large disordered molecules, with colors ranging between brown and black. At this point the matter is said to have been “charred” or “carbonized”.
  • At 200–300 °C, if oxygen has not been excluded, the carbonaceous residue may start to burn, in a highly exothermic reaction, often with no or little visible flame. Once carbon combustion starts, the temperature rises spontaneously, turning the residue into a glowing ember and releasing carbon dioxide and/or monoxide. At this stage, some of the nitrogen still remaining in the residue may be oxidized into nitrogen oxides like NO2 and N2O3. Sulfur and other elements like chlorine and arsenic may be oxidized and volatilized at this stage.
  • Once combustion of the carbonaceous residue is complete, a powdery or solid mineral residue (ash) is often left behind, consisting of inorganic oxidized materials of high melting point. Some of the ash may have left during combustion, entrained by the gases as fly ash or particulate emissions. Metals present in the original matter usually remain in the ash as oxides or carbonates, such as potash. Phosphorus, from materials such as bone, phospholipids, and nucleic acids, usually remains as phosphates.

Other Uses and Occurrences

 

Pyrolysis is used in the production of chemical compounds, mainly, but not only, in the research laboratory.

The area of boron-hydride clusters started with the study of the pyrolysis of diborane (B2H6) at ca. 200 °C. Products include the clusters pentaborane and decaborane. These pyrolyses involve not only cracking (to give H2), but also recondensation.

Other Occurences :

  • Pyrolysis is used to turn organic materials into carbon for the purpose of carbon-14 dating.
  • Pyrolysis of tobacco, paper, and additives, in cigarettes and other products, generates many volatile products (including nicotine, carbon monoxide, and tar) that are responsible for the aroma and negative health effects of smoking. Similar considerations apply to the smoking of marijuana and the burning of incense products and mosquito coils.
  • Pyrolysis occurs during the incineration of trash, potentially generating volatiles that are toxic or contribute to air pollution if not completely burned.
  • Laboratory or industrial equipment sometimes gets fouled by carbonaceous residues that result from coking, the pyrolysis of organic products that come into contact with hot surfaces.