All About Polyurea 

Markets and Applications for Spray Polyurea

Polyurea is a remarkable technology with a range of uses limited only by your imagination. As with any coating system, proper surface preparation, correct application equipment and the use of compatible primers is required.  Read on to see where and how polyureas are being used successfully around the globe.

Pipe / Pipeline Coatings & Linings 
Polyurea Coatings and linings are increasingly being used to protect steel pipes from corrosion. Polyurea has demonstrated its ability to last longer than paint and maintenance services and costs are reduced. Polyurea is a great protective coating system for pipes that are insulated with polyurethane foam. Polyureas are also being used to line the inside of water and sewer pipes for infrastructure rehabilitation work.

Bridge Coating 
Polyurea's ability to outlast paint and fight off corrosion is a major reason these systems are being specified for bridge deck and structure coating by State DOT's around the nation. The most common applications of polyurea coatings on bridges are over steel and concrete.

Joint Fill / Caulk 
Polyurea is being successfully used as a multi-purpose joint fill, caulking and sealant material. It can provide a flexible, durable, weather-tight and traffic resistant seal for all types of building joints, such as expansion joints and control joints in masonry floors, perimeter joints, panels and doors, water reservoirs, etc. It has excellent crack-bridging properties with high elongation and tensile strength. The fast cure time and insensitivity to moisture allows for a quicker installation with a wider application window. Proper surface preparation and substrate condition is always necessary.

Tank Coatings 
Polyurea coatings protect steel tanks from corrosion, chemicals, and other natural weather and jobsite elements. With proper surface preparation, substrate condition, formulation choice, primers, and installation procedures, polyurea goes on fast and stays on long. Polyureas are great for extending the life of older tanks and can offer limited structural characteristics as well. These systems can be applied during primary construction or in a retrofit environment. With their fast cure times they are ideal for retrofit since down time is significantly minimized compared to some competing materials.

Tank Linings 
Polyurea linings are resistant to many chemicals and industrial liquids. With their fast application advantages and ability to adhere to properly prepared substrates, polyureas are ideal for new storage tank primary lining and rehabilitation projects.

Marine 
Above the water line and below, polyurea can be very effective in protecting steel, aluminum, and fiberglass in a variety of water sport and commercial marine applications. From sound attenuation for fishing canoes, to fish hold liners, to hull protection and bilge liners, polyureas are used in many abrasion, chemical and corrosion resistant marine applications.

Roof Coating 
Polyurea coatings make an excellent protective covering for polyurethane foam roofs. Polyurea can be formulated to meet specific performance requirements due the wide range of physical properties that can be formulated. Some systems have the "Cool Roof" ENERGY STAR® rating for color and reflectivity. These reflective coatings can help reduce the amount energy consumption buildings use for heating and cooling. The fast cure time and insensitivity to moisture allows for a quicker installation with a wider application window. Proper surface preparation and substrate condition is always necessary.

Waste Water Treatment Linings 
Fast cure, chemical and abrasion resistant, concrete primary and secondary containment linings. What more can you say about Polyurea applications for the Wastewater Treatment industry?

Manhole & Sewer Linings 
Polyurea manhole lining is a rapidly growing market due to polyurea’s ability to solve many current issues with groundwater infiltration and installation speed. Many municipal and private water systems are in great need of lining and structural repair. With proper surface preparation and substrate conditions, primers and Polyurea can be applied fast to return the cavity to service faster than most competitive systems. Polyurea’s ability to form a monolithic, durable liner protects the cavity from sediment and groundwater infiltration into municipal wastewater systems.

Truck Bed Liners 
Polyurea truck bed liners form a durable, water and air-tight, permanent liner for the exterior of pick up trucks, dump trucks and steel containers. These durable, easy to clean and abrasion resistant liners protect utility trucks from their harsh duty environments. They also protect against rust and corrosion from damaging trucks and containers. Polyurea liners can also be applied in varied thickness to meet any specific application demand. Sprayed on truck bed liners are available in many colors and can be wrapped over the top edge of the truck bed to provide added protection from impact and abrasion.

Theme Park & Decorative Design 
Theme Parks often use polyurea as a protective coating over foam, EPS and other structures to create ornamental building fascia, themed characters, artificial rocks, pools and environments.

Flooring and Parking Decks 
Polyurea flooring systems are most popular for their rapid turnaround installation capabilities. Other benefits are available with polyurea flooring systems as well. Polyureas are very durable and great for use in areas of high traffic. They are used in clean/dirty rooms as a waterproofing and protective coating from daily pressure cleaning operations. Polyurea can be formulated to be flexible and resilient allowing the flooring system to protect objects that may fall upon them.

Aquarium Lining 
Aquariums have also found benefits with polyurea. The ability to form to properly prepared custom shaped walls and themed ornaments make this system desirable. A spray applied, water resistant liner, available in a variety of colors with rapid return to service installation is why facility owners are turning to polyurea.

Landscape & Water Containment 
Landscape designers and contractors have found similar benefits with polyurea. Polyurea is often used to contain water for ponds and pool decorations to form a primary containment liner. Use of geotextile material is common when applying polyurea over dirt. Proper surface condition is vital when applying over concrete and most other substrates.

Architectural Design 
Polyurea has much the same uses in architectural design as it does in theme park applications. Polyurea is used as a protective coating over foam, EPS and other structures to create ornamental building fascia, themed characters, artificial rocks, pools and environments. There are many uses for movie set and theater stage design as well.

Automotive Fascia OEM Molded Parts 
Polyurea can be spray, open pour or reaction injected into molds. Many automotive fascia parts have been molded from polyurea RIM systems. Now many spray in mold uses are becoming popular in replacing parts commonly made from fiberglass. Water park chutes, plaques, automotive aftermarket fascia and spoilers, architectural decorative molding, and more...

Water Parks & Playgrounds 
Molded slides, protective coating of seats for wet/dry amusement rides, tank linings, water containment, aquariums, concrete stadium seats are just a few of the many applications polyureas are commonly used for in the amusement and theme park industry. Polyureas usage is rapidly growing in applications to replace paint and fiberglass due its fast cure and ability to reduce maintenance cycles.

Railcar Lining & Track Containment 
Polyureas are commonly used to line liquid containment railcars for their waterproofing and chemical resistance benefits. Hopper style rail cars have benefited from the strength of polyurea and its ability to resist abrasion. These cars often carry coal, sand, and other abrasive materials. Polyurea can be applied quickly and it will last longer than many other conventional systems if properly applied.

Line Striping 
Polyurea is a very fast set material, which makes it ideal for use in line striping and pavement marking. It can be returned to service for traffic and pedestrian use in only a few minutes (depends on formulation) after application.

Polyurea is is much more durable than paint and typically lasts much longer between maintenance cycles. Polyurea is the clear choice when it comes to cost/performance payback and operation.

Spray Molding 
The use of Polyureas for spray in mold processes are gaining momentum with the advent of low output spray guns. Polyureas have very fast reaction times and are meter mixed and dispensed through plural component equipment. These materials are dry to the touch within seconds after application reducing demold time dramatically. Physical properties of these materials can be altered by the system formulator to meet application requirements.

Other Applications:
• Race Car Body Parts
• Mold Making
• Artificial Rock

Fuel Storage & Containment 
Polyurea is resistant to many fuels and chemicals. It is commonly used in fuel pits and pipeline secondary containment. Polyurea is not resistant to all chemicals and necessary compatibility tests and surface preparation are always required.

Polyurea Formulations & Raw Materials

A typical polyurea consists of a multi-ingredient chemical formulation commonly shipped in 55-gallon drum sets or 5-gallon pales. Part A is a dark colored viscous liquid called isocyanate. Part B is commonly called the amine resin blend.  It is often colored, or pigmented, and normally requires agitation or stirring before use.

When the liquids are thoroughly mixed, they result in an immediate chemical reaction that becomes viscous and ultimately solid.  This reaction is very fast and typically sets up dry to the touch within seconds.  Ultimate cure usually takes up to 24-48 hours, however longer and shorter cure time durations are quite possible depending on specific formulation and characteristics of mix.

The use of different types, and/or different volumes, of isocyanates, polyether, or polyester amines, chain extenders and other additives can have a significant effect on the ultimate physical properties and final characteristics of the polyurea coating/lining system.

Technical Aspect of Polyurea Formulations

Polyureas have been described as the resin from a polyurethane reacted with the curative of an epoxy. This is a good description, as polyurea coatings do seem to take the best from both of these polymer technologies. They have improved chemical and solvent resistance, and higher temperature resistance compared with the polyurethanes. They also have better impact resistance and higher elongation vis-à-vis the epoxy.

A polyurea is formed when amines react (cure) with the isocyanate. This reaction is fast, auto-catalytic (that means it does not need a catalyst to react – even at cold temperatures) and leads to many of the special properties that allow polyureas to distinguish themselves from the other polymers.

There are three main properties:

1. Polyurea reactivity is independent of the ambient temperature. Polyurea reacts fast – and it will react at the same speed regardless of the temperature. It can be 100 F or -25 F and the reactivity is almost the same. Polyurethanes can be catalyzed to also react very fast, but a system designed for 70 F, will take forever to cure at -20 F. A polyurethane system that will cure properly (fast) at -20 F will be too fast to handle at 70 F. Epoxy cannot cure at these very low temperatures. 
2. Polyurea reactivity is independent of the ambient humidity. It can be 98% RH and the polyurea coating will spray bubble-free. (Be careful of the dew point – that’s a different story) A polyurethane must have catalysts to complete the reaction. These catalysts are designed to catalyze either the polymer reaction (gelation) or the “blowing” reaction (many polyurethanes use this well known use of water to react with the isocyanate to release CO2 to use as the blowing agent in polyurethane foams). Unfortunately, either types of catalyst will catalyze BOTH reactions – to some degree. The choice of a good gelation catalyst will still catalyze the ISO/water (from the humid air) reaction – and when it does you WILL have bubbles. 
3. Polyurea develop their physical properties FAST. This gives the polyurea “FAST RETURN TO SERVICE”, that is you can drive on the coated floor; use the coated product within 12 hours of application. Polyurethanes take up to 14 days to fully develop their physical properties. Epoxy require several days.

As mentioned before, polyureas have improved chemical and solvent resistance and higher temperature resistance compared with polyurethanes. They have improved impact resistance and elongation compared with epoxies. All of the properties can be impacted by the formulating chemist.

The formulating chemist will always want to know the application for which his polyurea system is intended. The proper selection and amount of raw material components will effect the performance – both processing and physical properties.

A-Side Polyisocyanate Pre-Polymer

The selection of the isocyanate prepolymer will influence most of the properties of the polymer. The % of NCO will influence hardness, stiffness, strength properties, speed of reactivity. The “backbone” will influence the type of chemical/solvent resistance, as well as strength properties. The functionality (number of reactive sites per molecule) of the prepolymer will affect the temperature resistance, hardness, stiffness, impact resistance and elongation. The isocyanate can be aliphatic or aromatic. This selection will affect the UV stability, as well as other physical properties. The formulator may add other chemicals to the prepolymer, especially a diluent to lower the viscosity, and slow down the reactivity of the system. The viscosity of the system will greatly affect the processing of the polyurea.

B-Side: Resin Blend Formulation

The Resin blend consists of various amine terminated molecules of varying sizes and types.

The choice of which amines to include and the ratio among the amines, will determine the performance and the processing of the polyurea. To be a “pure polyurea” there can be NO (zero) “intentional hydroxyls” added to the system. If there are hydroxyl containing products (polyols) it will be a ‘hybrid’ coating.

Hybrid systems have their place. They are good systems for certain applications. There has been significant confusion in the marketplace between a true “Pure” polyurea and a hybrid. A coating system with hydroxyls (hybrid) will require a catalyst to complete the reaction. This catalyst will cause the polymer to have the difficulties sited above.

The choices of amines include: long chain “backbone” polyetheramines like BASF’s PEA D-2000 and PEA T-5000. These are the basis of the system. While PEA T-5000 is tri-functional, it does not act like a traditional cross-linker. This is due to the high chain length between the cross-links, or better in this case – branching. It is important to add some of the PEA T-5000 however because this “branching” will give the polymer a tighter network. All polymers oxidize or degrade over time. Some, more than others. Polyureas do not have a particular problem with this, but the addition of T-5000 will give the polymer a much longer life. This is especially true in submersion applications.

The short chain curatives may be aliphatic or aromatic. Aliphatic diamines like BASF PEA D-400 are very fast reacting. If cross-linking is desired, BASF’s PEA T-403 is short compact and tri-functional to provide efficient cross-linking. Higher cross-linking will give higher temperature resistance, higher tensile, improved solvent and chemical resistance, but will lower the elongation, tear strength, impact strength. Aromatic diamines like DETDA build in the polymers strength and rigidity.

Secondary diamines like PolyLink 4200 slow down the reaction times and help them process easier. PolyLink 4200 improves the polymer properties with better flexibility, lower water absorption, higher impact strength, better abrasion resistance, better chip resistance, less “orange peel” effect, better flow out, better self-leveling, and less shrinkage. PolyLink 4200 also gives you better substrate wetting and flow, better substrate adhesion, better inter-coat adhesion, and longer “open times” between multiple passes. You will get smaller droplets, less “fingering” and “roping” lower mix viscosity, Less build-up on the gun tip, less nozzle plugging, improved mechanical mixing, greater control on the thickness per pass, and higher productivity with lower down time. The ratio of the PolyLink 4200 to the DETDA will determine the speed of reactivity, the rigidity and hardness of the coating.

Various additives may also be included in the B-Side Resin blend. Adhesion promoters such as PolyGrab ES-187 and PolyGrab AS-1100 will help improve substrate adhesion and should always be used on concrete applications. In applications where UV resistance is important, all aliphatic systems should be used. UV stabilizers, such as PolyStab 100 should also be added to these aliphatic coating systems. In pure polyurea systems, pigments dispersed in BASF PEA D-2000 like those from Rebus Inc. should be used.

In caulk systems, the reaction times need to be much longer than in coating applications. Many of the same chemicals are used but in different ratios. For example, significantly higher levels of PolyLink 4200 will help delay the gel times and give better mixing and flow out at the lower mix pressures usually used for the caulk application.

In all polyurea applications, the coating formulation is only 1/3 of the critical success. Proper substrate preparation is necessary and proper equipment and mixing at proper temperatures and pressures is critical.

 With energy prices subject to significant volatility and the growing pressure to reduce carbon dioxide emissions caused by fossil fuels, the need for energy saving insulation is immense. Governments are recognizing this with new energy efficiency legislation and national and international commitments. As a leading global producer of MDI (methylene diphenyl diisocyanate), which is used to make polyurethane insulation, Huntsman plays a key role in conserving energy and contributing to a sustainable planet.