Surface Treating Glossary

Provided below is a glossary of surface treating terms. For answers to more detailed questions see our Surface Treating FAQ.
AFM
Atomic Force Microscopy, surface analytical method comprising the scanning of a surface by a tiny needle on a thin lever. Examination of the forces between needle and surface allows detailed depictions of the surface structure.
Active species
The interaction of a plasma with material in contact with the plasma is due to a multitude of active species such as ions, free radicals, electrons, molecular fragments and photons.
Additive/Additive Loads
Any substance that is added to another substance. Usually a material added in minor amounts to alter the properties of a resin or compound. The additives that concern surface treatment are slip, anti-block, colorants, chill roll release, etc.
Air Plasma
An electrical ionization of air by an electrode assembly.
Air/Gas Ratio
Known as the stoichiometric ratio, or the ratio of the number of parts of air required to combust one part of a hydrocarbon gas for flame treating.
Amorphous
Devoid of crystallinity - no definite order. At processing temperatures, the plastic is normally in the amorphous state
Bare Roll
The Bare-Roll design eliminates the need for a dielectric covering on the treater roll. This saves the cost of a spare dielectric roll. The Bare-Roll also prevents the loss of film and production time due to roll covering burn out. The system treats any web, including: plastic, foil, metalized film or paper. The patented airflow design aids in electrode temperature stability and provides ozone removal for an ozone safe work area. The high-efficiency ceramic electrodes are long-lasting and provide higher treatment levels.
Binding energy
Amount of energy necessary to break a covalent chemical bond. As the binding energies of most chemical bonds are rather high (300 – 900 kJ/mol), high temperatures are necessary for the thermal cleavage of covalent bonds. Because of the high energies of the charged particles (ions and electrons) in a plasma, chemical bonds are easily cleaved in a plasma, resulting in the generation of highly reactive radicals and cations
Bonding
Contacting method largely employed in semiconductor industry, connecting conducting contacts of chips with conductive strips and housings. Bonding is often disturbed by organic residues from prior production steps, which can be removed by plasma treatment
Coating
Coating is a process whereby a coating is applied to a substrate. The coating can be solvent based, water based, UV curable or electron beam curable. Sometimes coating can mean extrusion coating whereby a substrate is coated with a molten polyolefin.
Coating/Laminating
Coating is accomplished by the use of numerous types of roll coating methods and slot die coating techniques. Laminating consists of combining and bonding diverse substrates with either wet or dry adhesives, thermally or by the use of hot-melt adhesives. Substrates most commonly used include papers, film materials (nylon, cellophane, polyester, polyethylene, polypropylene, etc.), aluminum or steel foils, non woven, textiles, fabrics and carbon fibers.
Contact angle
The angle between the surface of a liquid phase on a solid phase and the solid’s surface. Used as measure for the interaction of the liquid with the solid: the higher the contact angle, the smaller is the interaction. When the solid’s surface energy is larger than the liquid’s surface energy, the contact angle becomes zero.
Corona
Corona treatment is a common method used to increase the surface energy of plastic by means of a high voltage electrical discharge, thus improving its wettability and adhesion characteristics for printing and laminating. Although there are numerous theories explaining the principles behind the process of corona treating, the most commonly accepted theory appears to be the theory of high speed oxidation. Basically, this theory states that the energy of the corona breaks the molecular bonds on the surface of the non-polar substrate. The broken bonds then recombine with the free radicals in the corona environment to form additional polar groups on the film surface. These polar groups have a strong chemical affinity to the polar inks and adhesives, which results in improved adhesion. Similarly, the polar surface results in an increased surface energy which correlates with improved wettability.
Covalent Bonding
The sharing of pairs of electrons between atoms, or between atoms and other covalent bonds. In short, the attraction-to-repulsion stability that forms between atoms when they share electrons.
Covered Roll
The Covered-Roll treater system is equipped with covered ground rolls and segmented or tube stainless steel electrodes. The electrode assembly configuration and method of ozone extraction and electrode cooling assures that the inside of the station is ozone-free. This permits painted steel frame and enclosure-type construction with no risk of corrosion. The cooling system also reduces the temperature of the electrodes which, in turn, reduces the reflected heat into the web and ground roll. The highly efficient system of electrode cooling prevents any warping or distortion of the stainless steel electrode segments.
Cross-cut tape test
The cross-cut tape test is applied to characterize the adhesion of coatings. Herein, the surface of a sample is cut cross-wise after coating. Afterwards, an adhesive tape is stuck onto the cut surface and then peeled off. If parts of the coating remain on the tape, the coating’s adhesion is insufficient.
Cross-Linking
Applied to polymer molecules, the setting-up of chemical links between the molecular chains. When extensive, as in most thermosetting resins, cross-linking makes one infusible super-molecule of all the chains.
Crystallinity
A state of molecular structure in some resins which denotes uniformity and compactness of the molecular chains forming the polymer. Normally can be attributed to the formation of solid crystals having a definite geometric form.
Deflashing
Covers the range of finishing techniques used to remove the flash (excess, unwanted material) on a plastic molding.
Degradation
The deteriorization of highly reactive organic species on the surface of treated materials, leading to a reduction in surface tension.
Desmear process
The desmearing process is established in circuit board manufacturing: after drilling of the circuit boards (mostly composed of glass fiber enforced epoxies) residues of the board material remain at the edges of the holes. These residues are removed by plasma treatment.
Dyne Level
Dyne level is a measurement of the surface energy of a substrate. Both (PP) and (PE) are low energy plastics. Untreated PP and PE have a low dyne reading (usually 30 to 32 dyne). Using Fluoro-Seal surface modification treatment will raise the surface energy level and allow adhesives to achieve maximum surface adhesion.
Dyne Solution
Dyne solutions have been used to measure wetting and predict adhesive potential of plastics and coated paperboard. This method is widely used to test the treatment level of plastic films intended for printing, laminating, and coating. Test results are based on how varying surface tension solutions react when applied to a non-absorptive surface: If a given solution wets the surface, its dyne level is lower than the substrate's; if, instead, it rapidly forms beads, its dyne level exceeds that of the substrate. This method offers adequate precision and replicability for most capability studies, materials research, and process control.
Dynes/cm or Newtons/meter
Dynes/cm or Newtons/meter is the unit of force in the centimeter-gram-second absolute system, the force which imparts an acceleration of 1 centimeter per second per second to a body having a mass of 1 gram. Symbol, dyne. In SI units, one dyne = 10 -5 newton. To convert from to Multiply by dyne (dyn) newton (N) 1.0 E-05.
Electrode
An electrical conductor used to discharge high voltage.The word was coined by the scientist Michael Faraday from the Greek words elektron (meaning amber, from which the word electricity is derived).
Electrode / Dielectric / Ground Roll
The corona treating system in its simplest form can be portrayed as a capacitor. Voltage is applied to the top plate which, in the case of a corona treating system, would be the electrode. The dielectric portion of the capacitor would be made up of some type of roll covering, air and substrate in the corona treating system. The final component, or bottom plate, would take the form of an electrically grounded roll.
ESCA
Electron Spectroscopy for Chemical Analysis, also designated IEE (Induced Electron Emission) or XP(E)S (X-Ray induced Photoelcetron Spectroscopy). Spectroscopic method for the analysis of chemical bonding. Often applied in the investigation of sample surfaces, e. g. to determine oxidation states. All elements except for hydrogen and helium can be analyzed.
Etching
Process in which a surface, in most cases of a metal, is cleaned by removing surface oxide or passive films. Etching can either be accomplished by dipping into an acid or alkaline solution or by plasma treatment (“plasma etching”) in an appropriate process gas. Examples for the application of etching processes are silicon, SiO2 and Si4N3 in microelectronics as well as metals with surface oxide and nonadherent polymers such as PTFE.
Extrusion
Extrusion is the process of introducing plastic resin pellets into an extruder then raising the temperature of the resin to its melting point and pumping the melted resin through a die to produce plastic film, sheet or a blown film.
Flame
A flame plasma is formed when a flammable gas and atmospheric air are combined and combusted to form an intense blue flame. The surface of materials are made polar as species in the flame plasma affect the electron distribution and density on the surface. This polarization is made through oxidation. In addition, functional groups are deposited on the surface.
Flame Plasma
The ionization of an air/hydrocarbon gas mixture from a flame burner. High temperature (adiabatic flame temperature is approximately 33,000'F) is sufficient to dissociate nitrogen and oxygen molecules into free atoms (8). In addition, this high-temperature plasma contains carbon, free electrons, positively charged oxygen, and other ions and excited species. Because of this reaction, polar functional groups such as ether, ester, carbonyl, carboxyl, and hydroxyl are contained in a flame plasma; these are incorporated into the surface and affect the electron density of the polymer material. The result is that the polymer surface is polarized.
Functional Groups
Specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.
Functionalization
Surface functionalization introduces chemical functional groups to a surface. This way, functional materials can be designed from substrates with standard bulk material properties. Prominent examples can be found in semiconductor industry and biomaterial research. In both cases, plasma processing technologies were successfully employed.
Gap
The distance between the face of the discharge source to the material surface.
Hydrophilicity
Affinity for water of a substance caused by isolated charges or by highly polar groups able to interact strongly with the highly polar water molecules. There are also molecules with a hydrophilic moiety whereas the other moiety is hydrophobic, e. g. in detergents. This composition is crucial for their cleaning effect.
Hydrophobicity
Surfaces containing no polar groups and therefore featuring hydrophobic properties. Hydrophobic layers can be produced by plasma polymerization, e. g. using HMDSO (hexamethyl disiloxane) as monomer.
Ionization
Process in which an atom, molecule or ion loses an electron. Ionisation can be caused by an high-energetic electron or photon. An atom can also be ionised by contact with excited atoms or with a hot surface.
kVA vs kW
kVA is kilovolt-ampere; kilovolt-amperes and kW is a unit of power equal to 1000 watts.
Laminar Flow
Laminar flow of thermoplastic resins in a mold is accompanied by solidification of the layer in contact with the mold surface that acts as an insulating tube through which material flows to fill the remainder of the cavity. This type of flow is essential to duplication of the mold surface.
Line Speed
Speed at which the production line operates. The maximum line speed is the preferred metric so the treating system is sized appropriately.
Modification
Change of a surface’s chemical composition or constitution. A surface modification is accomplished by liquid etching processes, by oxidation or reduction or by physical methods such as corona or plasma treatment.
Modulus of Elasticity
The ratio of stress to strain in a material that is elastically deformed.
Nip Roll
Pneumatically operated rubber covered roll that applies pressure to the substrate onto the ground roll.
Non-Polar
A non-polar molecule is one that the electrons are distributed more symmetrically and thus does not have an abundance of charges at the opposite sides. The charges all cancel out each other.
Oxidation
The addition of oxygen to a compound or the reduction of hydrogen.
Ozone
A colorless gaseous substance obtained (as by the silent discharge of electricity in oxygen) as an allotropic form of oxygen, containing three atoms in the molecule. It is a strong oxidizer, and probably exists in the air, though by he ordinary tests it is liable to be confused with certain other substances, as hydrogen dioxide, or certain oxides of nitrogen. It derives its name from its peculiar odor, which resembles that of weak chlorine. Ozone generators deliver high ozone concentration at minimal power levels. Ozone generators are used to advance adhesion in extrusion coating and laminating. * Adding ozone to your process allows for lower extrudate temperatures and the use of lower temperature resins (Eves). * Reduced air gaps reduce "neck-in", translating into greater productivity. * Some companies have improved production speeds by as much as 50% by adding ozone to their process. * Ozone can also enhance product value by improving bonding characteristics, heat sealabilty, color and odor.
Peel Adhesion Test
This test method covers a laboratory procedure for determining the strength and characteristics of the peel properties of a substrate relative to an ink, coating or adhesive before and after surface treatment.
Plasma
Electrical conducting gas involving electrons and ions. The name plasma goes back to Irving Langmuir (1928). Plasmas show collective behavior, e.g. for screening and plasma oscillation.
Plasma - Atmospheric vs Vacuum
Both atmospheric and vacuum plasma treating process introduce an inert gas and apply a high voltage to the gas providing an enhanced treating process. While atmospheric plasma introduces this gas at atmospheric pressure, the vacuum process evacuates all air from a chamber and then introduces the gas. One advantage to atmospheric plasma treating is a continuous web of material can be treated. However, vacuum plasma only allows a batch of items to be treated which is limited by the size of the vacuum chamber.
Plasticers
Chemical agent added to plastic compositions to make them softer and more flexible.
Power Supply / Generator
The power supply accepts standard 50/60 Hz utility electrical power and converts it into single phase, higher frequency (nominally 10 to 30 kHz) power that is supplied to the corona treater station.
SEM
Scanning Electron Microscopy, most widespread method for the high resolution imaging of solid surfaces. The surface is irradiated with electrons, the backscattering by secondary electrons is measured, resulting in a direct depiction of the surface landscape.
Surface Activation
Increase of energy and decrease of contact angle, usually correlates directly with improved bonding.
Surface energy
Surface energy, also designated surface tension, is a value characterizing the interaction of a condensed phase’s (solid or liquid) surface with its environment, given in mN/m. Surface energy is a criterion for the coatability of a material and can be increased by different plasma processes (e. g. plasma cleaning, plasma etching, etc.).The surface energies of solids range from below 20 mN/m (e. g. PTFE) up to several thousand mN/m (metals, diamond).The surface energy of a solid can be estimated by means of test inks, a precise determination of disperse and polar portion is feasible by wetting angle determination of different liquids on the respective surface.
Surfactant
A compound that affects interfacial tensions between two liquids. It usually reduces surface tension.
Thermoplastic
Capable of being repeatedly softened by heat and hardened by cooling (n.) - A material that will repeatedly soften when heated and harden when cooled. Typical of the thermoplastics family are the styrene polymers and copolymers, acrylics, cellulosics, polyethylenes, vinyls, nylons, and the various fluorocarbons materials.
Thermoset
A material that will undergo or has undergone a chemical reaction by the action of heat, catalysts, ultra-violet light, etc., leading to a relatively infusible state. Typical of the plastics in the thermosetting family are the aminos (melamine and urea), most polyesters, alkyds, epoxies, and phenolics.
Treat Width
Maximum width at which the treating system must be sized to treat the substrate configuration on a production line.
Treatment Head
The electrode or burner assembly utilized to impart treatment.
Universal Roll
The design contains a special coated roll which in combination with our unique ceramic electrode assembly treats consistently to high levels. The system treats any web including plastic, foil, metalized film or paper. The patented air-flow design provides enhanced treatment levels and creates unique ozone removal capabilities for a safe work area. High-efficiency rectangular ceramic electrodes provide highest treatment levels.
Watt Density
Watt Density is a measurement of the amount of energy being applied to the web. It is measured in Watts/ft2/minute. Watt density takes into account the amount of power being applied (watts), the time it is being applied (minute) and the amount of material it is being applied to (ft2). Once the watt density is known to get a particular material to a certain dyne level, it can be used to predict the results if any of the parameters change such as line speed.
Weld Mark
A mark on a molded plastic piece made by the meeting of two flow fronts during the molding operation.
Wettability
The contact between a liquid and a solid surface, resulting from intermolecular interactions when the two are brought together. The amount of wetting depends on the energies (or surface tensions) of the interfaces involved such that the total energy is minimized.
Wetting Tension
The object of surface treating is to improve the wettability of the surface, thereby improving the ability to bond to solvents, adhesives, coatings, and extrusion coating. In order for a surface to be properly wet by a liquid, the surface energy of the plastic must be higher than the surface tension of the liquid. Surface energy is measured in dynes per centimeter. This surface energy is the wetting tension.