OLD COAT, NEW THREADS

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1 OLD COAT, NEW THREADS Todd Gomez, PCS, John Winfrey and Dudley J Primeaux II, PCS, CCI VersaFlex Incorporated, 686 S. Adams Street, Kansas City, KS USA Learning Objectives: Discuss new aliphatic polyurea technology vs. traditional polyester gel coat systems. Achieve an understanding that the aliphatic polyurea gel coat products are: Green materials, have longer predicted life cycles, enable faster production rates and quicker return to service. New advanced aliphatic polyurea technology offers superior advantages over non-voc compliant polyester gel coat technology for coating / lining applications. Abstract: Gel coat has traditionally been used in environments where color, gloss and relative long-term performance are important. This premise is still true today; however, a much more advanced technology has been developed that provides improved characteristics of color and gloss stability, higher mechanical properties and zero Volatile Organic Compounds (VOC s). This newest advancement in coating technology can be utilized in a wide variety of applications and substrates including concrete, fiberglass, and metal while meeting SSPC (The Society for Protective Coatings) standards. The belief is that this new advancement of technology is significant to the protective coatings industry in an ongoing effort to develop green products, those products that contain no solvents, no heavy metal catalysts and limited waste through plural component processing. The makeup of emitting no VOC s and very low odor further enhance the benefits of using an overall safer product. INTRODUCTION: The spray-applied, two-component, ambient-cured aliphatic polyurea technology, which features no VOC s and low odor, can be applied at colder temperatures than current available coatings. This wider temperature application range extends the season for restoring outdoor substrates. The technology provides quick dry times; leading to faster return-to-service and helping applicators and owners meet tight deadlines. Additionally, the system may be applied over existing coatings such as epoxy, polyurethane, polyester or polyurea. Historically, gel coat products are comprised of unsaturated polyester resins specially formulated with thixotropic ingredients for increased viscosity and non-sag properties and pigments for desired color. Additional additives may be utilized for controlling flow-out, gel and cure times. Unfortunately, gel coat prematurely fades, oxidizes, chalks, cracks and looks dull within 1-2 years. The resin is unreinforced and heavily filled, which contributes to the low tensile properties and high fracture possibility.

2 Gel coat contains styrene, a hazardous chemical that is now considered a carcinogen by the U.S. Department of Health and Human Services. Styrene is a reactive diluent that both helps reduce the viscosity of the polyester resin, as well as provides additional bonds in the polymer matrix. Unfortunately, styrene is an aromatic molecule that is susceptible to UV damage. Once gel coat oxidizes, it is nearly impossible to restore the gel coat surface to its like-new color appearance because the polymer has been permanently damaged by the UV rays of the sun. Product Design: Gel coat has the purpose in a fiberglass reinforced product to protect the reinforcement resin utilized from the environmental challenges that damage the polymer. Initial gel coat formulations were nothing more than pigmentation of the reinforcement resin. The opacity of the coating derived through pigmentation blocked and reflected much of the damaging UV energy that attacks the aromatic portions of the polyester matrix. As the technology developed, more complex polymers were introduced to enhance performance. Transitioning from orthophthalic to isophthalic backbones, enhancements in pigment treatments as well as processing improvements aided in the advancement of polyester gel coat products. Unfortunately, the concerns of styrene to both worker exposure and the environment forced manufacturers to compromise the advancements of their labor to comply with new regulations on styrene. And, while the reduction of styrene from the coating minimized color change (having less aromatic molecules), it had a devastating influence on other properties, due to manipulations that were made to the polymer to accommodate less styrene. Gel coat, by nature of being on the outer surface of a structure, is subject to the highest strain of the entire laminate. The tensile or compressive strain in a loaded laminate increases with distance from the neutral axis of the load. In the illustration (Figure 1) of a typical laminate placed under a flexural load, the highest tensile strain is recorded at the top surface, while the highest compressive strain is at the bottom surface. There is no strain at the interior of the laminate, at the neutral axis. Because of the critical positioning of the gel coat film in a laminate structure, both the laminate and the supporting structure must take into account the strain imposed by anticipated operating loads. (1) Figure 1: Typical Flexural Laminate Load Illustration

3 Ask any fabricator that uses polyester gel coat and they will tell you the primary issue in achieving a part that can be sold is overcoming the processing issues, which can result in stress fractures in the coating. Obviously, having a coating that will be more resilient to the fabrication process with higher mechanical properties will be beneficial in overcoming cracks/fractures during the fabrication process. THE POLYUREA INFLUENCE: Many years after original gel coats were introduced into the marketplace, newer and more advanced technology came about to rival traditional gel coats. Reaction spray molding (RSM) using polyester/urethanes hybrids became a big player in boat fabrication. However, even with this new technology, problems were still evident. There became a tendency to have air voids and defects. Also, blisters appeared if it was exposed to immersion conditions, not to mention the glass pattern transfer which occurred from a polyester laminate that used a heavily textured mat. In general, the finished result of this system produced 20% less weight than traditional fiberglass maintaining similar type properties higher gloss retention and ability to accept fasteners in the structure. (2) Following this, aliphatic spray polyurea systems began an appearance in the coating / lining marketplace. While derived from the fast set aromatic polyurea spray coating / lining systems, this technology presented some very unique challenges in spray processing characteristics. (3) Unlike aliphatic polyurethane spray systems, the aliphatic polyurea systems possess extremely fast reactivity / gel times. Though sometimes doubted by others, the aliphatic polyurea systems have extremely good UV and UV Color stability. (4) Generation 1: Taking advantage of the excellent performance characteristics of the fast set aliphatic polyurea spray technology, gel coat applications were first employed for in-mold coating work. Utilizing the fast set, 100 % solids characteristics, plural component aliphatic polyurea systems have been employed in a variety of recreational item related applications. The polyurea is first applied to a polished mold surface, then backed using a high stiffness thermoset technology to produce a part. Given the compatibility of the polyurea gel coat and the backing material, excellent adhesion is noted in the formed composite layer. The fast set / cure of this concept allows for rapid part de-mold and production rates, all without any solvent / VOC emissions. Additionally, the finish surface was porosity free. Examples are shown in Figures 2 and 3.

4 Figure 2: Applying Polyurea Gel Coat Figure 3: A Completed Part, Polyurea Gel Coat Surface

5 A more recent technique of this fast set aliphatic polyurea gel coat, is the use for coupling nontypical technologies. In this case, the polyurea gel coat is applied first to a polished sheet tool / mold, which is then closed and a thermoplastic polyethylene resin system is injected molded behind. This can produce parts with high gloss, color stable and relatively scratch resistant surfaces. (5). An example is shown in Figure 5. Figure 5: Aliphatic Polyurea Gel Coat / PE Molding For this Generation 1 technology, conventional high pressure, high temperature plural component spray equipment is required. Due to the fast reactivity nature, impingement mix spray guns are used to achieve proper mix. These spray guns are either air or mechanical purge. Generation 2: Spraying into a mold is one thing, but trying to achieve the same surface qualities from a mold surface to the actual spray finish surface is another challenge. While that fast set, aliphatic polyurea technology of Generation 1 is good, it is not very applicable for field application work and achieving nice surface finish characteristics. In order to achieve the slower set times, this Generation 2 has relied on the use of the polyaspartic ester (aspartic ester) technology for formulation work. Now there has been discussion that this is not a polyurea. However, since the reaction of the aliphatic isoscyanate component with the secondary amine containing resin blend does yield a urea linkage, this is in fact a polyurea system. (6)

6 Since these systems are slower in reactivity, smoother, higher gloss surface finishes were achieved for coating work. But most systems were formulated as a 2:1 volume ratio, meaning typical 1:1 high pressure plural component equipment had to be modified for use. Work then progressed to also include certain high molecular weight plasticizer / non-reactive material to allow for 1:1 processing, thus utilizing equipment in place by the applicators. (7, 8) This Generation 2 polyurea Gel Coat technology then found use in a variety of theme park and decorative coating application areas. An example is shown in Figure 6, where the high gloss and good color retention can be noted. Figure 6: Theme Park Slide Re-coat, Polyurea Gel Coat Since these type systems are much slower than Generation 1, spray guns could employ various options. In some cases, a mix manifold has been used, where the in-line static mixed material is delivered to a conventional airless spray gun. Or, impingement mix, solvent purge spray guns are used. In either case, solvent is then required to flush mixed material from the high pressure hose or spray gun, and presents environment issues. This is shown in Figures 7 9. Figure 7: Mix Manifold Figure 8: Conventional Spray Figure 9: Solvent Purge

7 The New Threads: By using the lessons learned in the previous generations, the New Threads has evolved. This generation of aliphatic polyurea gel coat systems utilizes the same plural component equipment for fast set aromatic polyurea systems, and is 1:1 by volume. While still a fast set technology, it still meets industry requirements for a tough, high gloss, smooth finish. (9) The following Table 1 includes typical properties of this new generation aliphatic gel coat system. Table 1 Next Generation Aliphatic Polyurea Gel Coat Test Method * Results Tensile strength, psi ASTM D 638, Type IV Elongation, % ASTM D 638, Type IV 3-6 Gloss, 60 ASTM D Shore D Hardness ASTM D Processing ratio, by volume 1 to 1 Gel Time 90 seconds Hard to touch 6 7 minutes VOC Content ASTM D % Solids 100% Adhesion to fiberglass, psi ASTM D 4541 > 500 Adhesion to base membrane, psi ASTM D 4541 > 500 Coefficient of Friction ASTM F 609 Neolite feet, dry 0.51 Leather feet, dry 0.20 * Latest Revision This brings the gel coat technology into more conventional coatings work, adding opportunities outside of the theme park based use. Use in special tank lining application provides a smooth, easy release surface for stored product, Figure 10.

8 Figure 10: Steel Tank Lining, Aliphatic Polyurea Gel Coat In the food processing industry, typical wall systems are based upon attached fiberglass panels, which contain seams. Over time, the seam area will undergo separation and allow for the collection of bacteria, etc. It then makes cleaning / sanitizing very difficult. By removal of the existing fiberglass panels, these concrete or concrete block wall areas are prepared, followed by priming and application of a base coat of an aromatic polyurea spray elastomer system. (10, 11) The Aliphatic polyurea gel coat system is then applied to the aromatic polyurea base coat, providing for a high gloss, hard finish that can easily be cleaned / sanitized using the Nitric / Phosphoric acid based cleaning systems. Figures show examples over a concrete block and metal wall applications.

9 Figures 11 & 12: Aliphatic Polyurea Gel Coat in Food Processing Facility Figure 13: Aliphatic Polyurea Gel Coat, Food Processing, Metal Walls

10 This new generation gel coat technology also proves useful in more architectural / decorative applications where high gloss, smooth finish, color stability and waterproofing properties are required. Given the aliphatic backbone base of the technology, excellent resistance is noted when exposed to harsh oxidizing agent, such as chlorine treatment. Figure 14 shows an example of a reflecting pond lining application over concrete for a major business in Detroit, Michigan. Figure 14: Polyurea Gel Coat use in Reflective Pond Lining Work

11 An important key feature to the new generation of aliphatic polyurea gel coat system is the higher thermal stability of the polymer. This is very important in cleaning / sanitizing applications using the conventional Nitric / Phosphoric acid based cleaning systems as well as immersion use. The following Figure 15 gives a comparison of the Tg characteristics. Figure 15: Thermal Analysis of Aliphatic Polyurea Gel Coat Systems

12 A summary of the evolution of the aliphatic polyurea gel coat systems is shown in Table 2: Table 2 Polyurea Gel Coat Evolution / Characteristics & Properties Generation 1 Generation 2 New Threads Processing ratio, volume 1 : 1 2 : 1 1 : 1 1 : 1 with solvent Gel time 3 to 6 seconds ~ 2 to 3 minutes ~ 90 seconds Dry Time 20 seconds ~ 30 minutes ~ 7 minutes Tensile strength, psi Elongation, % 50 ~ 5 ~ 5 Shore D Hardness 60 + ~ Gloss, initial CONCLUSION: As with any coating / lining technology, product evolutions occur so as to meet the never-ending challenges that are faced. The progression from solvent based systems to the high to 100% solids materials has been a very important evolution in the sciences. This has then allowed us to take conventional coating / lining applications and expand into various other areas to meet the ever expanding needs of our industry. (12) The work is progressing with excellent application and performance results. This New Generation Aliphatic Polyurea Gel Coat technology is bringing new life to existing food processing and clean room facilities, as well as other applications, and many are proud to show off these New Threads!

13 References: (1) Lacovara, Bob, "Getting A Handle on Gel Coat Cracking, Convergent Composites: Volume 82, No. 18, Nov (2) Jarboe, Rodney, RSM Challenges FRP Boat Construction, Reinforced Plastics, December, 1995, pp (3) Primeaux II, D. J., Application of 100% Solids, Plural-Component Aliphatic Polyurea Spray Elastomer Systems, Journal of Protective Coatings and Linings, March, 2001, pp (4) Primeaux II, Dudley J., Polyurea Thick-Film Elastomeric Coating / Lining Systems, Accelerated Weatherometer Testing vs. Real Life Exposure, PACE The Power of Paint & Coatings, Phoenix Convention Center, Phoenix, AZ, February 7 10, (5) Moch, Dr. Thomas, The Colorform Processing A World s First to Realize High Gloss and Scratch-resistant Surfaces with Polyurea, PDA Europe th Annual Conference, Polyurea is Taking Off!, Hotel Belair, The Hague, The Netherlands, November (6) Primeaux II, Dudley J., Two-Component Polyurea Coatings / Linings, Selecting Coatings For Industrial and Marine Structures, Dr. Richard W. Drisko, Editor, SSPC: The Society for Protective Coatings, 2008, Chapter 7, pp (7) Reinstadtler, Steven, Site Applied Gel Coat Refurbishment Using Polyaspartic Technology, PDA Europe th Annual Conference, Polyurea is Taking Off!, Hotel Belair, The Hague, The Netherlands, November (8) Lane, Sam, et. al., New UV/Color Stable Spray Aliphatic Polyurea Coating Technology, PDA Europe th Annual Conference, Polyurea is Taking Off!, Hotel Belair, The Hague, The Netherlands, November (9) SSPC-Paint 39, Two-Component Aliphatic Polyurea Topcoat, Fast or Moderate Drying, Performance Based, SSPC: The Society for Protective Coatings, Pittsburgh, PA, April (10) SSPC-SP 13: Surface Preparation of Concrete, SSPC: The Society for Protective Coatings, Pittsburgh, PA. (11) ICRI Guideline No : Guide for Surface Preparation for the Repair of Deteriorated Concrete Resulting from Reinforcing Steel Corrosion; Concrete Surface Profile (CSP), International Concrete Repair Institute, Des Plaines, IL. (12) SSPC-PA 14, Application of Thick Film Polyurea and Polyurethane Coatings to Concrete and Steel Using Plural-Component Equipment, SSPC: The Society for Protective Coatings, Pittsburgh, PA, September 25, 2012.

14 ASTM International Methods (latest version) West Conshohocken, PA noted: ASTM D 523 Standard Test Method for Specular Gloss ASTM D 638 Standard Test Method for Tensile Properties of Plastics ASTM D 2240 Standard Test Method for Rubber Property Durometer Hardness ASTM D 3960 Standard Practice for Determining Volatile Organic Compound (VOC) Content of Paints and Related Coatings ASTM D 4541 Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers ASTM F 609 Standard Test Method for Using a Horizontal Pull Slipmeter (HPS) Figures 10, 11, 12 & 13 courtesy of FIXXUS Rehabilitation Systems, Inc., Greensboro, North Carolina.