Applying Plural Component Spray Applying Plural Component Spray Presented By: Art Webb, Naval...

Applying Plural Component Applying Plural Component SpraySpray

Presented By: Art Webb, Naval Presented By: Art Webb, Naval Research LaboratoryResearch Laboratory

ScopeThis webinar provides an

introduction and overview of plural component spray methods of applying industrial/marine protective coatings.

Learning Outcomes At the end of this webinar the student will

be able to: Recognize the use of plural component

application Define a high solids coating Identify plural component application systems

available Recognize the methods for properly mixing

material or coating components (e.g., Part A, Part B)

Why the Interest in Plural Component Application

EconomicsEnvironmental ComplianceApplication ReadinessSafetyApplication Quality

High-Solids CoatingsFor our purposes, high-solids coatings

are considered to be at least 90% solids

A Component B Component

Base Catalyst

Resin Amines

Prepolymer Isocyanate

Polyol Accelerator or Promoter

Activator

Various Names for A and B Components

Plural Component CoatingsTypes

e.g., Epoxies / Polyurethanes / Polyureas

Components of a Typical Epoxy Component (A): Resin or Base Component (B): Co-reactant or Curing

Agent

Curing Mechanism Reaction of Components A and B to

form a chemically crosslinked protective film

Characteristics of Two Component Epoxies Ratio

Volume by ratio of Components A to B (i.e.. 1:1, 4:1)

Induction Time (Sweat-in-Time) Time mixed components must stand to allow

for initial chemical reaction prior to application

Pot Life Time mixed components remain usable

without affecting applied coating performance

Characteristics of High Solids Epoxies

Solids by Volume

Primer Characteristics

Topcoat Characteristics

Characteristics of High-Solids Epoxies Viscosity (resistance to flow)

Generally twice that of solvent based epoxies Higher pressure required to pump and atomize Heating coating reduces viscosity

Pot Life Measured in minutes vs. hours (ex. 45 minutes

@ 77°F) Exothermic reaction (heat generated by mixed

components in container)

Characteristics of Polyurethane Coatings

Polyurethane Coatings Advantages Limitations

Characteristics of Moisture-Cured Urethane Coatings

Moisture-Cured Urethane (MCU) Coatings Advantages Limitations

Polyurethane Advantages

Turn Around Time100% SolidAbility to Apply During Winter

MonthsUnique “Self-Inspecting” Property

Plural Component Application Process - Summary Components A and B are power mixed/agitated

separately Components are heated to reduce their

viscosities and re-circulated uncombined from the reservoir to the mixer and back until the desired temperatures and viscosities have been reached and maintained

Both components are pumped separately in their desired proportions (flow rates) toward the spray gun

Components are combined in a manifold/mixer immediately before reaching the gun

Examples of Plural Component Spray Examples of Plural Component Spray UnitsUnits

A B C

55 gal. “B” SupplyAgitator and Elevator

55 gal. “A” SupplyAgitator and Elevator

To Catalyst (B) Inlet

To Resin (A) Inlet

30:1 Solvent Flush toMix Manifold

Heated Hose to Manifold

“A” Inlet

Gun 2

Mix

Gun 1

“B” Inlet

“B”

“A”

Proportioner

Heater A

Heater B

Plural Component Equipment SchematicPlural Component Equipment Schematic

System Components

Feed systemPump/proportioning systemHosesHeating systemMixing manifold systemSpray gun

Feed System

Feed Pumps

Characteristics of Pump SystemsAvailable Spray PressureNormal atomization/spray pressure Flow rate Compatibility of wetted parts with

materials pumpedPower source

Characteristics of Pump Systems - Impact on SystemFeed pumps must be of a sufficient

size Need sufficient spray pressure

Power Sources for PumpsAir-powered supply pumpsHydraulic supply pumps

Photo of Proportioning (Metering) Pumps

Courtesy of WIWA

Courtesy of Graco, Inc.

Critical Nature of Mixing RatioProper RatioCheck RatioOff-Ratio Monitoring System

Unit Control Panel

Digital Heat Controls Digital Pressure Control

Cycle Counter

PSI or Bar

F° or C°

Park “A” pump

Target and Actual Temp

Error Codes

Stop

Remote Mountable Controls - Up to 30.5 m

Heated/ Insulated Hoses

Portable Unit with Spray Hose

Heating System (In-line)

Coating Material Temperature Requirements

Too low a temperature will restrict flowToo low a temperature may also cause

amine blush or amine bloom as it is sometimes called

Amine Blush on Steel

Taking Material Temperature Using Infrared Gun

Critical Material Temperature Check PointsStorage Temperature Reservoir/supply container Pump Manifold Gun

Mixing Manifold System

The mix manifold is where the material components A & B are brought together to be mixed at proper ratio.

Manifold Mixer

Mix Manifold SystemMix ManifoldMix Manifold Assembly and

ConnectionsMixing Manifold Maintenance & Care

Mixing Block (isolated)

Solvent Purge SystemUsed to flush mixed components

from manifold, spray hose, and gun

Purging of Mixed Components After Interruption of WorkMixed components must be solvent

purged or flushed from the gun whenever application is interrupted for several minutes

Equipment Clean-up Plural-component application

equipment must be thoroughly cleaned after use, especially interiors of pumps, manifold, hoses, guns and tips

Cut-away of plural component impingement gun with component hoses joined at the tip

Airless Spray Gun

Proper AtomizationAtomization occurs in airless

spraying when coating is forced under high pressure through tip orifice

Factors Affecting Spray Pattern Size

Size of tip orifice (typically 0.017 to 0.021)

Wear of tipFan angleDistance of gun from substrate

being painted

Tip WearHigh solids coatings wear tips more

rapidly than traditional solvent borne coatings

Diagram of Changes in Airless Spray Pattern with Tip Wear

Application ThicknessTheoretically, wet film thickness of

high-solids coatings is the same as the dry film thickness

Area with restricted working space can easily become coated with excessive film builds

Matching of System Components All system components should be

properly matched for size and capacity The heating system should also match the

components Clean, lubricate and otherwise maintain

equipment parts for best service Never modify equipment without

consulting with manufacturer

Plan the WorkApplication team should be briefed

about planned work before beginning it.

SummaryIn this Unit, we covered:

Why industrial/marine customers are considering use of plural component spray technology to apply 100% solids coatings

Brief introduction to high solids material Plural component application systems Mixing methods

Questions?