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Flame treatment is the application of a gas flame to the surface of a material to improve
Fuel gas is pre-mixed with air, and the resulting
Comparing Flame, Plasma, and Corona Treatments
Industrial processes Plastics industry {{tech-stub
adhesion
Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another).
The forces that cause adhesion and cohesion can ...
.
Polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...
s, especially polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including b ...
and polypropylene
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.
Polypropylene
belongs to the group of polyolefins a ...
bond poorly, because they consist of long non-polar
Polar may refer to:
Geography
Polar may refer to:
* Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates
*Polar climate, the cli ...
molecules. Without special treatment, adhesives, ink, and other coatings cannot be applied to these materials. By rapidly applying intense heat to a surface, molecular chains are broken and polar functional groups are added. Flame treatment also burns off dust, fibers, oils, and other surface contaminants.
Flame treatment is faster than corona treatment
Corona treatment (sometimes referred to as air plasma) is a surface modification technique that uses a low temperature corona discharge plasma to impart changes in the properties of a surface. The corona plasma is generated by the application of ...
, but requires more complicated and expensive equipment.
Process
Fuel gas is pre-mixed with air, and the resulting flame
A flame (from Latin '' flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density the ...
is directed at the surface to be treated. The flame has a light blue inner cone, called primary, and a dull blue outer cone, called secondary. The hottest part of the flame is the primary, which may be up The tip of the inner cone (primary) contains an assortment of highly reactive chemicals, including unburned oxygen, carbon dioxide, water vapor, and free radicals
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.
With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spon ...
atomic oxygen (O1) and hydroxyl (OH).
To treat a surface quickly and evenly, many gas jets, similar to the one on the right, are lined up in a long row on a single burner. The material being treated is quickly passed directly in front of or under the inner cones. The surface is in contact with the flame for less than a second. The surface is treated quickly, without time for the material to melt.
The reactive chemical species
A chemical species is a chemical substance or ensemble composed of chemically identical molecular entities that can explore the same set of molecular energy levels on a characteristic or delineated time scale. These energy levels determine the wa ...
in the gas flame break the long-chain molecules in the plastic material, and attach themselves to the break points, resulting in polar point charges on the surface. On a microscopic scale, the surface also becomes rougher.
See also
*Chemistry of pressure-sensitive adhesives
The chemistry of pressure-sensitive adhesives describes the chemical science associated with pressure-sensitive adhesives (PSA). PSA tapes and labels have become an important part of everyday life. These rely on adhesive material affixed to a bac ...
* Plasma activation Plasma activation (or plasma functionalization) is a method of surface modification employing plasma processing, which improves surface adhesion properties of many materials including metals, glass, ceramics, a broad range of polymers and textiles ...
* Corona treatment
Corona treatment (sometimes referred to as air plasma) is a surface modification technique that uses a low temperature corona discharge plasma to impart changes in the properties of a surface. The corona plasma is generated by the application of ...
* Polymeric surface
* Stone flaming
* Surface finishing
References
External links
Comparing Flame, Plasma, and Corona Treatments
Industrial processes Plastics industry {{tech-stub