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Glossary of Terms

Powder Coating Terms & Definitions
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Take up –
A device that maintains tension on a conveyor chain during operation.

Tape Adhesion –Test used to check for adhesion of a coating to a surface.  (ASTM Test D3359)

TDS – Total desolved solids, a measurement of the solids content of water in parts per million (ppm).

Technical  Data  Sheet    (TDS)    A  document provided by a supplier that details the properties and  expected  performance  of  a  material.  Also known as Product Data Sheet.

Telegraphing – Phenomenon that occurs when a surface defect on an uncoated part is visible in the cured powder after the coating is applied.

TGIC    Triglycidyl  Isocyanurate,  a  common crosslinker for carboxyl polyester resins.

Theoretical Coverage – The capacity of a given mass  of  a  specific  powder  to  coat,  in  a  cured state, an area of substrate at a determined film thickness.

Thermocouple    A  pair  of  dissimilar  metal wires that generate an electric force at the point of  connection  which  varies  in  proportion  to temperature.

Thermoplastic – A powder coating which will repeatedly  melt  when  subjected  to  heat  and solidify  when  cooled.  Typical  examples  are vinyls (PVC), nylons, and polyolefins.

Thermosetting    Powder  coating  chemistry that undergoes an irreversible chemical change during  thermal  cure.  Examples  are:  epoxy, polyurethane, acrylic.

Threshold Limit Value (TLV) – The concentration of a compound that a worker can be exposed to day-to-day  without  experiencing  any  adverse effects. TLV’s are established by the ACGIH.

Throughput – The production output of a system at a given line speed using a predetermined part density or hang pattern.

Time Weighted Average (TWA) – The legal limit of exposure of a chemical measured as average exposure  over  an  eight  hour  period  of  time. TWA’s are established by OSHA and are used to define Permissible Exposure Levels (PEL).

TLV – See Threshold Limit Value.

Tooth – Profile. Mechanical anchorage. Surface roughness.

Totes    Large  containers  for  shipping  bulk powder coatings.

Toxic – Poisonous.

Toxicity    Degree  of  poisonousness  or harmfulness.

Transfer Efficiency – The ratio of the powder deposited compared to the amount directed at the part to be coated.

Transformer,  Pneumatic    Device  used  for regu lation  of  pressure  in,  and  removal  of moisture from, an air supply line.

Tribocharging    A  method  to  impart electrostatic charge on a powder coating by the friction or contact of the powder with a material of dissimilar dielectric constant.

Triglycidyl  Isocyanurate  (TGIC)    A  tri- functional epoxide compound that is commonly used  as  a  crosslinker  for  carboxyl  polyester resins.

Triggering    Intermittent  squeezing  and releasing of a spray gun trigger, or turning them on and off intermittently for some systems.

Turbulent Flow – Air currents within a spray booth that may be strong enough to negatively affect the application of powder. Good transfer efficiency is dependent on laminar air flow.

TWA – See Time Weighted Average.

Two–stage  Compressors    Compressors  in which compression from initial to final pressure is completed in two distinct steps or stages.

Ultraviolet Absorber (UVA) –
A chemical that absorbs  harmful  UV  energy  and  dissipates it  into  heat  energy.  UVA’s  are  used  to  reduce coating  degradation  due  to  exposure  to  solar energy.

Ultraviolet  Radiation    Light  energy  having a  wave length  of  about  0.4  to  80  milimicrons. Such energy can break certain chemical bonds and contribute to the fading and wearing away of coatings.

Underatomized – Not enough atomizing air in ratio to supply air, resulting in a spray pattern that  surges  and  is  not  fine  enough  for  good charging efficiency.

Undercured    A  coating  that  has  not  had enough  exposure  to  the  combination  of  heat and time to completely cure.

Upper  Explosive  Limit    Concentration  of solvent  vapor  or  coating  powder  particles  in air above which the mixture will not explode if ignited.

Urethane – The product of the reaction between a  hydroxyl  functional  compound  and  an isocyanate. Hydroxyl polyester resins cured with blocked isocyanate curing agents are commonly referred to as urethane or polyurethane powder coatings.

UV  Flame  Detection  System    A  device  that senses  the  UV  light  emission  cause  by  an ignition source. In powder coating application systems  these  devices  are  used  to  shut  down the spray process when a spark is detected.

UV  Flame  Detection  System    A  device  that senses UV light in a powder booth and shut the equipment off when it detects a spark.

Vacuum Wand –
Vacuum cleaner or wand for twin air belt booth or a tool used with a vacuum system for cleaning up powder.

Valve,  Check    Direction  control  valve  that allows air to pass in only one direction.

Valve,  Flow  Control    Valve  whose  primary func tion is to control flow rate.

Valve, Shut–off – Valve that operates fully open or fully closed.

Valve, Throttling – Valve used to regulate the pressure/flow of solutions in the washer.

Velometer – Device to measure the speed of air in feet per minute.

Venturi – A constricted throat in a powder pump that uses compressed air to lift and transport powder from the feed hopper to the application equipment device, from the bulk feeder to the feed hopper, from the cartridge module to the feed hopper, etc.

Vertical  Zoning    Triggering  only  the  guns needed  to  coat  a  given  part  length  to  reduce overspray when a conveyor is loaded with parts of  various  lengths.  Multiple  photo–eye  inputs can be used to control which guns are used on any given part.

Vestibule – Small entrance hall to pretreatment washer, powder booth, or oven.

Vibratory Box Feeder – A device allowing the powder  to  be  pumped  directly  from  the  box container  utilizing  vibration  to  keep  powder moving.

Vibratory Sieve – See Sieve, Vibratory.

Vinyl    A  popular  name  for  thermoplastic polyvinylchloride (PVC) materials.

Vinyl Coating – A coating in which the major portion of the binder is a vinyl resin.

Vinyl Copolymer – Resins produced by copoly– merizing vinyl monomers such as vinyl acetate and vinyl chloride.

Vinyl Resin – Synthetic resins made from vinyl compounds.

Virgin Powder – Unsprayed powder as opposed to sprayed or reclaimed powder.

VOC – See Volatile Organic Compound.

Volatile Content – The quantity, expressed as a  weight  percent  of  the  powder,  which  is  lost under specified conditions of temperature and time.

Volatile  Organic Compound (VOC) Hydrocarbon chemicals that can evaporate into the atmosphere and are recognized by the US EPA  as  contributors  to  photochemical  smog. VOC’s are commonly emitted from solventborne paints.

Voltage Tester – Instrument used to measure voltage  output  at  the  corona  tip  of  an electrostatic powder spray gun.

Voltmeter – Instrument used to measure poten- tial differences in volts.

Volume  Resistivity    Resistance  in  ohms per unit of volume. The property of a material that deter mines its resistance to the flow of an electrical current.

Volumetric Efficiency – The ratio of the actual capacity  of  the  compressor  to  displacement, expressed in percent.

W Pattern  Calculation 
  Calculation  of  the coverage  for  combined  motions  of  part  travel and gun oscillation.

Waggler – See Oscillator.

Washer Drain Zone    The  space  in  between spray zones within the washer tunnel.

Washer  Process  Zone    The  spray  treatment zone within the washer tunnel.

Washer Vestibule – The portion of the washer tunnel at the entrance and exit.

Water  Spotting    Whitish  blemishes  on  a pretreated  part  where  minerals  in  the  water have left a deposit on the surface.

Weathering Resistance – Also Weatherability. The ability of a surface to withstand the outdoor elements without degradation.

Weld  Splatter    Beads  of  metal  left  adjoining a weld.

W.C.    A  measurement  of  pressure  in  inches of water column. The pressure to be measured is introduced into one end of a u–shaped tube filled with colored water and the measurement is deter mined by how far up a tube the water is pushed.

White  Blast    Blast  cleaning  to  white  metal surface.

Wrap  A characteristic of powder coatings in electrostatic application to seek out and adhere to  areas  of  the  substrate  not  in  direct  line  of sight of the delivery system end point.

Yellowing –
Development of yellow color or cast in  a  light–colored  powder  formulation  due  to aging or improper cure cycle.

Zinc Phosphate Coating –
Conversion coating used  on  steel  and  galvanized  steel  parts  to improve coating adhesion and corrosion resistance.