Introduction
The fiberglassing of the interiors of swimming pool and spas has enhanced the appearance, durability' and chemical resistance of the surface over traditional surfaces. This enhancement has been instrumental in increasing consumer satisfaction and confidence in their pool or spa investment. Because of its durability and chemical resistance, many fiberglass resurfacer have approached the industry with the belief that fiberglass coating are so forgiving that anything done with fiberglass has to be far superior to more traditional plastered surfaces.
Over the past three decades, the swimming pool industry has seen a number of different types of fiberglass applications. The most common are the one step chopper gun lamination, and the one step hand lay-up application. These two methods utilize a waxed, filled, pigmented resin applied to the swimming pool surface by either spraying, or rolling with paint rollers. Fiberglass roving is chopped into the resin with chopper guns; or, in hand lamination. a chopped strand mat is pasted up against the resin coated surface. The final step of this application is the application of an additional amount of resin over the fiberglass to saturate the surface. Both of these techniques, when improperly applied, can have serious drawbacks. The application of a waxed primary coat does not allow much latitude for corrective action. Incomplete primary bonding is always a potential problem. The waxed coat in this type of process inhibits secondary bonding. The result is often times blisters (see Appendix). In addition, the one step hand lamination does not always fully saturate the fiberglass mat, leaving a "stringy" looking surface. The fiberglass then has to be lightly sanded to knock down the rough areas. Sanding may often lead to the problem of breaking the sealer finish coat and opening small pinholes, which increase the hydroscopic tendencies oft he glass laminate, leading to delamination. Another problem that plagues the fiberglass coating industry is the application of fiberglass to poorly prepared substrates. It is absolutely imperative that the surface to be fiberglassed is solid, clean, and free of paint or any other material that may inhibit primary bonding. Also, the fiberglass resurfacers have many choices as to which types of re ins would be the best to use. Unfortunately, the majority of fiberglassers get into the industry with very little knowledge of resins, fillers, pigment loads, surfacing agents, and catalyst percentages. Problems resulting from the above applications, which are somewhat of a low-tech "standard", have been responsible for creating skepticism among consumer and service industry technicians. If the fiberglassing industry is to remain a viable and valuable part of the swimming pool and spa industry, it must address these issues to promote consistent, superior results and to increase consumer confidence. Fiberglass technology for swimming pool and spa coating can legitimately be a low maintenance viable alternative to plaster, and especially re-plaster.
Problems and Corrective Measures
The remaining content of this paper will address some of the current problems with fiberglass coatings and what corrective measures should be taken to truly make fiberglass coating viable.
1. Delamination (pull-away from the substrate) is a common problem that ha given fiberglass critics plenty of ammunition. There are several causes of delamination.
A. Moisture on the surface at the time of laminating.
B. Improper preparation of the substrate, leaving dirt, grit, dust or oily film on the surface, or glassing over soft plaster.
C. Breakdown of materials in water due to the use of non-pH table fillers in the fiberglass mixture, i.e., calcium carbonate. Too many tillers used to extend and thicken resin (Lim 1996).
D. Water absorption through tiny fibers that are not completely encapsulated.
E. Glassing over painted services.
F. Pinhole in laminate due to improper cure (usually too fat).
G. Improperly cutting and sealing around fixtures and at tile line.
The solution for the above problems can be addressed as follows: A dry, clean surface is imperative to the success oft he laminate -use a moisture meter, grinders for scoping, and a vacuum for cleaning. Check all areas for soft spots on the surface to be glassed. Any painted surface must first be sand-blasted to ensure complete paint removal. Last, an excellent primer or bonding coat, using an unwaxed high grade vinyl resin, is very important. Vinyl e tel'S are more water-tight than polyesters. When the vinyl ester is catalyzed with MEK-P, cross-linking take place, with the vinyl e tel' molecules linking together in such tight strands that moisture cannot penetrate the coating (Aldridge 1994). Vinyl e tel'S also have a high corrosion resistance factor even in acidic environments and temperatures above 200°F. Note: Besides their high cost, the only negative factor about vinyl ester resins is that they do not hold pigments as well a polyesters, which may present a problem if used in finish coating. Also, vinyl e tel'S are not as UV table as polyester resins. Again, this is only a problem if it is used as a finish or top coat.
2. Chalking (flaky or milky look when rubbed) is caused by improper cure due to the incorrect percentage of surfacing agent. A surfacing agent is a paraffin wax in a styrene liquid solution. The following suggestions will greatly decrease the occurrence of chalking.
A. A surfacing agent is used in the finish coat of fiberglass laminate. Chemically, when the MEK-P is introduced to the resins, a catalystor hardening reaction starts to take place. The resin reacts to the catalyst and a heating or exotherm begins. This heating causes the surfacing agent to rise to the top of the resin. If the surfacing agent is mixed thoroughly, it rises and creates an oxygen void to the laminate. It is this oxygen deprivation that allows the laminate to fully cure. After the cur~ut stage, the surface will feel bard and smooth. Conversely, an improperly cured surface will be softer, more susceptible to breaking down and water absorption.
Re in manufacturers suggest a minimum of 5% unfacing agent by weight to ensure a fully cured laminate (Lim 1997). An important point is to control the mixing of the surfacing agent into the coating material. It must be continually mixed with a solid agitator that will not absorb wax and change the ration of surfacing agent to resin.
B. To be avoided is the use of non-pH stable fillers, especially calcium carbonate to thicken the material. Many of the larger coating companies still use calcium carbonateasfJllersorextendersofthere ·ins. It is like taking ground sirloin and adding "Hamburger Helper" to make meatloaf. It is no longer "pure beef'. The resins used by most fiberglass coating installers is an is ophthalic polyester resin. These resin were designed to be resistant to corrosive environments, even under high temperatures. The fillers added to the mix inhibit the corrosion resistant qualities of the laminates.
C. The improper percentage and mixing of the MEK-P. Methyl Ethyl Ketone-Peroxide is the catalyzing agent introduced to the t'esin which sets off the chain reaction that results in polymerization or hardening. Note: An area of debate 1S which system offers the best cured surface -hand lamination or gun lamination. The hand lamination method relies on the accurate measurement of catalyst to resin by a worker pouring exact amounts proportionately with every batch to ensure an evenly catalyzed surface. The gun laminating method employs the use of a spray gun that sprays the resin through a center nozzle and injects catalyst from side orifices into the resin. The amount of catalyst is regulated by a slave pump which can be set to deliver exacting amounts of catalyst to the resin. The typical mixture of catalyst
to resin 1S between 1% and 2% by volume, depending upon ambient air tempiture.
D. The ambient air temperatme is critical to a well cured laminate. As noted above, fiberglassing should be done in a moisture free environment. The ideal ambient air environment is 77' F. All laminates are tested at that temperature. Fiberglass lamination may still be successful done at temperatures as low as 55°F and as high as 95°F (Lim). The percentages of catalyst would range from approximately 3% at 55°F to 3/4% at 95°F. It is not recommended going below 1% MEKP (Lim). Research and field studies have demonstrated that the best laminations are between 70°F and 80°F. Fiberglassing below 60°F it is not recommended because of the long gel-time. Caution should be used in temperatures above 90°F, especially when using a surfacing agent (wax) in the coating material. It 1S critical that the surfacing agent has enough time to migrate to the surface in order to seal off the oxygen which results in surface cure. A gel time of 14-20 minutes is adequate to allow the migration of the surfacing agent. Shorter gel times may inhibit the migration of the surfacing agent, resulting in unevenly cured surfaces. Note: To double check the surface cure, pour acetone onto a clean rag, then rub rag on cmed fiberglass surface. When it is tack free, then surface cure has been achieved. A tacky surface indicates oxygen inhibition, which suggests that the air did not allow the surface to cure adequately. A minimum of 24 hours should be allowed for finish coat to cure before the acetone test. Amore accurate test for the cured surface 1SaBarcolhardness test. A Barcol gun presses a needle into the laminate and measures the hardness. The hardness measurement should be 90% of the manufacturer's specifications. For example, if the manufacturer's test the cured resin at a 50 for Barcol hardness, the field test should be at least 45. Generally, a well fabricated, well cured laminate will have a minimum Barcol reading of 30 (Ashland Chemical 1965). The pinholes from the Barcol gun should always be filled with a small amount of top coat or finish coat.
3. Cobalting is the manifestation of black spots on the fiberglass surface, sometimes with trails. This is commonly called the "black plague." Cobalt Naphthenate is a promoter that, along with Dimethylanilile COMA), is used in the resin so it will react to the Methyl Ethyl Ketone Peroxide (MEK-P) for cure. The cobalt actually does not complex with the polyesters. It is susceptible to attack by high levels of chlorine that may be present in pool water. If there is a small pinhole in the laminate where the cohalt can be exposed to chlorine, the result would be the leaching out of a black chloride salt which leaves and unsightly stain. There are two arguments on how to avoid cobalt stains:
A. One argument, which to my knowledge has not been successfully demonstrated, is to eliminate cobalt as a promoter and instead employ a BPa (Benzyl Peroxide) cure system. The BPa system is not widely used in fiberglass laminations because it is more difficult to mix into the resin system and it may cause higper exotherm (curing) temperatures and uneven cures because of its mixing difficulty. Another problem with the BPa cure system is the need to increase pigment loads to achieve an acceptable color. The amount of pigment needed inhibits the cure and the corrosion resistance of the fiberglass composite (Lim).
B. The second argument is to eliminate many of the fillers, such as calcium carbonate, Alumina Tryhydrate and dry pigments. Anything added to the resin formula that is dry often times does not mix well, leaving a particulate that can eventually slough off in water, resulting in pinholes which then can potentially expose the cobalt to chlorinated water. If fillers are eliminated from the polyester, and only paste pigments and thixotropes are high sheared into the resin, the chances for cobalting is very minimal.
An added caution is to advise service technicians not to allow the pool water to have a free available cWorine level above 3ppm for long periods at a time. Chlorine levels of 2ppm or lower are les likely to react with the cobalt.
4. Blisters have the appearance of round bubbles or protrusions in the finish coat, usually one to six inches in diameter.
The cause of blisters is mainly a problem with secondary bonding, i.e., top coat with wax bonding to previously waxed resin. In fiberglass resurfacing, it is not possible to apply a second finish coat over an already cured finish. The waxin the finish will prohibit secondary bonding. Even when vigorous sanding is employed it is extremely difficult to remove the wax from the finish, especially with the dimpled surface of a chop strand mat laminate.
Another cause of blistering is again the plague of a highly filled resin. Filled resins are more susceptible to pinholes which allow water absorption.
The problem of blistering can be avoided by using a high grade i ophthalic, corrosion resistant resin without fillers, especially in the finish coat. Only apply finish coat, unwaxed laminating surface to achieve optimum secondary bonding. The desired thickness of the finish coat should be approximately 15 mils thick when cured. This provides an excellent seal to avoid water penetration and protection again t cobalt stains (Lim).
I have addressed a variety of problems within the fiberglass coating industry, as well as outlining how to avoid some of the more common mistakes made when fiberglassing. I want to articulate some of the virtues of a fiberglass coated pool.
Since fiberglass cures dry, once the pool is filled, there is no need for labor intensive start up costs. The start up i "goof proof', allowing swimmers back into the pool as soon as the water is sanitized-no more blaming the pool technician.
A well cured fiberglass surface is easy to clean, stain resistant, stays smooth, and is user friendly. The fiberglass liner also has a superior thermal coefficient; thus, it stays warmer and has a longer life expectancy than other more traditional surface . Some fiberglassers even offer custom colors that can have a high degree of color uniformity, as well as cutting down heating cot. Fiberglass is totally water-tight. It eliminates exposed rebar, does not pall or chip, and has a flexural strength that accommodates many expansive soil area.
The research technical support and field testing ha been accomplished so that when done correctly, taking all precautions into account, resurfacing a swimming pool and spa with fiberglass makes the fines, long lasting pool surface. The fiberglass resurfacing industry has the opportunity to alleviate the most common concerns and make the necessary corrections, adjustments and changes to produce the very best fiberglass coated surface.
In closing, all individuals and companies involved in the fiberglass coating of swimming pools and spa should form a fiberglass coating industry. There must be an agreement on which types of applications and products used will meet the necessary standards. The chemists for the resin manufacturers could serve on an advisory committee along with respected people in the industry to create a standard for certification. Those companies that meet the industry criteria will then be able to use the certification logo in advertisements and sale. The resin manufacturers and suppliers can assist in "policing" the industry by selling only the approved products to the fiberglass resurfacing companies.
Let us take this opportunity to advance our technology to a new and higher level and give legitimacy to fiberglass surface a truly viable alternative for swimming pool and spa coatings.
When done correctly and taking all precautions into account, resurfacing a swimming pool or spa with fiberglass will make for the very best, long lasting surface. Our research and field testing has allowed us to address the common concerns and make corrections, adjustments, and changes to produce the very best fiberglass coating materials.
References
The installation of fiberglass liners in swimming pools has been used with varying degrees of success for approximately 25 years. This paper will discuss the viability of fiberglass as a low maintenance alternative to traditional plaster surfaces, and discuss specific problems resulting from the application and maintenance of the product, along with strategies to avoid these problems.