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How spray-up will survive the '90s; environmental concerns are forcing FRP open molders to spray new materials with more efficient equipment or switch to closed molding processes.

How Spray-UpWill:Survive the '90s

Environmental concerns are forcing FRP open molders to spray new materials with more efficient equipment or switch to closed molding processes.

Even more than in most areas plastics processing, environmental issues are shaping the future of open-mold spray-up of fiber-reinforced plastics (FRP). To reduce styrene monomer and other volatile organic compound (VOC) emissions, FRP processors will move away from conventional spraying toward methods that involve improved catalyst mixing and higher transfer efficiency. Greater use of new catalyst formulations or novel materials may also lead to emissions reductions.

Relatively new equipment alternatives to conventional spraying, such as so-called impregnators or saturators, are also expected to grow in popularity, as are incremental steps toward automatic control of the spray-up process. Although greater use of closed molding is expected, the growth of reaction injection molding (RIM) and resin transfer molding (RTM) in the traditional spray-up market may be limited by higher tooling costs, especially for low-volume projects. FRP spray-up remains a very cost-sensitive business, and it will most likely retain a niche in areas where low tooling costs and equipment are paramount, such as in prototyping and short runs.

MATERIALS DRIVE EQUIPMENT R&D

In the next 10 years, John Raymer, marketing manager at Venus-Gusmer, foresees "even more emphasis on styrene reduction, greater emphasis on quality-control issues such as intensive mixing of catalyst, and more concern over health issues pertaining to worker safety, such as exposure to MEKP catalyst and organic solvents." The push for recycling also may influence spray-up development.

Material supplies are scrambling to reduce the styrene content in unsaturated polyester resins, but a consequence of this is that many materials have become more sensitive and difficult to handle. These more viscous materials are harder to atomize and mix. "Try laying down a thin film of something that's three times as viscous as what you're used to, and you've got a real problem," says Robert McCullough, general manager of the PRED Div. of Binks Manufacturing Co.

"With the tremendous advances in material technology in the last five years, you'd have to be a little bit crazy to project too much," McCullough adds. "We will see a lot more new materials, some automation, and a lot more sophisticated processors, but substantially fewer of them. If the styrene problem solved by the material suppliers, then the heat will be taken off the FRP fabricators."

Use of polyesters made with monomers other than styrene--vinyl toluene or paramethyl styrene, for example--will be limited by the relatively high price of these alternate monomers. Some FRP processors currently use polyesters with suppressant additives that form a wax film during curing to prevent styrene from escaping. However, this creates a need for secondary finishing in order to ensure adequate secondary bonding integrity.

Presenting a challenge to the equipment suppliers are hybrid materials such as urethane/polyesters from Cook Composites and Polymers, Amoco Chemical Co., and Polymer Development Labs (PDL); as well as a phenol/resorcinol blend from Indspec Chemical Corp. The low-styrene hybrids and phenolics are expected to grow in popularity, but due to their nontraditional mixing ratios and higher viscosities, they will require greater technological capability to process.

"Unlike conventional FRP, where your catalyst content may be 1.5% and the other 98.5% resin, the ratios in hybrid materials are more like 2:1 or 3:2, so you can't take a conventional chopper system and use these new materials," according to Mike Keegan, FRP market manager at Glas-Craft. Indspec's two-component phenolic systems use a 1.3:1 mix ratio. Equipment suppliers expect unusual mixing ratios to become much more common, at least until material chemistries catch up with government styrene-emissions requirements.

Gary Smith, president of GS Manufacturing, considers spray-up equipment for hybrid resins to be the most promising component of his business. GS now offers an internal-mix system specifically designed for spray-up of urethane/polyester hybrids. Like a cross between RM and standard polyester spray-up equipment, the system uses a drum preheater and hose heater for the B-side of the material. To vary ratios, the A-side pump is adjusted, while the B-side pump remains fixed. The B-side material can be filled with 15-30% alumina trihydrate.

Binks is introducing an external-mix spray gun that reportedly allows reduced VOC emissions via more efficient mixing of the catalyst and resin (see accompanying news story). McCullough anticipates that this new mixing technology "will allow some people who are considering going into closed molding to stay in open molding because of the very low atomization pressure and very efficient mix of the catalyst and resin."

Although external-mix spraying has been the most popular choice in recent years, environmental concerns appear to have spurred a resurgence of interest in internal-mix guns (see PT, Feb. '89, p. 47). Any mixing of catalyst in air will lead to some emissions, and for this reason, internal mixing may continue to gain in popularity, regardless of improvements in external-mix technology. Dwight Goodman, president of Glas-Craft, feels that "internal mix will probably carry the day in the end."

CAN RECYCLING WORK?

Although somewhat lower down on the list of environmental issues driving FRP technology, the push to recycle may lead some processors to savings in material costs. A system for using reground FRP scrap as a reinforcing filler in fresh spry-up is available from Seawolf Design Group. The system grinds FRP scrap to lengths of 1/4 in. to 5/16 in., without destroying the fiber, the company says. The ground material is then mixed at up to 45% loadings with a syntactic polyester foam and sprayed through a modified FRP gun. This is said to allow reduction in both the amount of virgin resin used and freshly chopped glass. Current customers are whirlpool manufacturers, and some boatmakers are interested in the system.

Throwing yet another twist on the future of materials are the problems in the Mideast. With higher oil and resin prices, Binks' McCullough expects spraying of heavily filled materials such as syntactic foams to increase. The new Binks gun mentioned above is said to work with heavily filled materials. Binks is also developing a new internal-mix gun that will have larger passageways to accommodate high filler content.

A COMEBACK FOR BPO?

Benzoyl peroxide (BPO) was a popular spray-up catalyst in the early days of pressure-pot premix dispensing, before the advent of continuous catalyzation and BPO's displacement by MEK peroxides. The initial success of MEKP was due to the disadvantages of BPO's particle form and its shock sensitivity when dry.

In recent years, with greater attention to the need for safe transportation, storage and use of "yellow-label" products like MEKP, aqueous, "wet" BPO emulsions (usually 40% active) in sprayable, fine-particle form have re-emerged. These are available from suppliers such as Atochem North America and Akzo Chemicals, and they are being developed by Witco Corp. and Norac Co. However, the main marketing thrust for BPO in spray-up as come from Abco Industries. Its Abcure product, like other BPO emulsions in said to have safety advantages over MEKP, largely because it needs no refrigeration. Although there are plenty of skeptics who question its suitability for FRP spray-up, Abcure is nonflammable and contains no VOCs. It is also said to be less hazardous than conventional BPO formulations when left to dry. This is reportedly due to the use of a noncombustible diluent that controls the shock sensitivity of BPO when it dries.

Abcure is said to provide a more controllable exotherm and faster Barcol development than MEKPs, which may lead to less styrene emissions while curing. Abco v.p. Edward Page says that some of the company's customers have been able to obtain both a lower peak exotherm and faster cure. The company is currently studying a hypothesis that may account for reduced styrene emissions during the actual spraying of material. The water in the dispersion may be acting to reduce the amount of styrene that escapes from the sprayed resin, possibly via a viscosity increase at the surface of the resin spray.

All of the major spray-up equipment suppliers sell some sort of BPO-compatible equipment or retrofit kit. Glas-Craft has sold "quite a number of BPO systems" and expects to see "more and more of it [BPO]," Keegan says. Binks' McCullough feels that "if the benefits far outweigh the hassle, then BPO growth will happen."

The difficulties in using BPO can include abrasiveness and wear on equipment. While MEKP's viscosity resembles that of water, BPO emulsions are more viscous and harder to atomize, requiring equipment modifications such as bigger hoses and nozzle holes, along with some sort of flushing method to ensure that the BPO particles do not air-dry and pack out.

Jim Hedger, president of Magnum Industries, feels that "spraying BPO will become a bigger trend each year." In addition to larger internal passageways, Magnum's BPO gun design includes harder surfaces to accommodate the abrasiveness of BPO particles. Hedger says that some BPO formulations work very easily whereas others do not, due to varying viscosity ranges. This makes it difficult to come up with standard BPO equipment.

Many processors are reluctant to switch to BPO because the reported benefits have yet to be proven worthwhile. According to some equipment suppliers, BPO gives a different textural look to the finished product. Moreover, because the dispersion contains water, not all resin suppliers feel comfortable in fully supporting the BPO approach. There is a concern about jeopardizing surface finish and structural integrity with pinholes and voids.

Although Binks' Poly-Craft Systems Div. makes equipment to handle BPO, general manager Jim Cavanaugh feels that this catalyst may not necessarily become an important trend. "The high percentage of water content in BPO limits its use; especially where integrity of the laminate is important," he says.

Even the machinery suppliers who acknowledge the potential benefits of BPO are somewhat skeptical of its prospects, because of the inherent resistance to change among FRP fabricators. McCullough says that equipment from Binks and a lot of other companies "handles Abcure well. However, we just don't see the growth that people talk about in BPO. Most of the processors are saying, `I already know how to make my system work with MEKP, so why do I need to change? This stuff's going to cost me more money."

Aside from the cost of new equipment and the problems involved in trying anything new, BPO may cost more per lb than MEKP. Abco's Page feels that this has not been a serious problem, but he admits that many processors are taking a cautious approach. He also points out that "some of the people who were the most skeptical when we introduced Abcure are our biggest supporters now." Currently, approximately 30 processors use Abcure on a production basis, he says.

For those processors who want to consider alternative catalysts, computer databanks can provide information on reactivity. As an indicator of this potential, Atochem North America recently developed a personal-computer database program that supplies half-life information on all of its peroxide products, including BPO and MEKP formulations. The program, which is being supplied free of charge to customers, provides single data points or a graphical range, based on trade name and temperature selections entered by the user. The company is also offering a Lotus-compatible spread sheet file for determination of residual peroxide concentrations at various time/temperature conditions.

As an alternative curing agent for FRP spray-up, Atochem is optimistic about the prospects for its Lupersol 221, a fire-resistant 2,4-pentanedione peroxide. This ketone peroxide is less corrosive, less toxic, and less flammable than MEKP. While Lupersol 224's water content is lower than that of BPO emulsions, it is much higher than that found in MEKP formulations. Similar products are also available from Akzo Chemicals, Norac, and Witco.

OUTLOOK FOR AUTOMATION

Numerous FRP processors have expressed an interest in automated spray-up systems in the past, although far fewer of them have been willing to invest the time and money to make them work. Robots are complicated and expensive, but could improve product uniformity, reduce waste, and minimize human exposure to styrene and other fumes. Requirements for full automation would include monitoring of catalyst and resin flow rates and pressures, along with glass ratios and part positions. A fully robotic spray gun with all the necessary sensors and controls would look quite different than current models, and the plan layout of the typical spray-up facility would have to be changed also.

Automated guns are available from most manufacturers, but there has not yet been any great demand for them. Comments one equipment supplier, "The people who own and run FRP businesses aren't willing to pay their existing spray people a good enough wage to get quality spray, so one thing's for sure: If they put in a robot, they're definitely not going to spend the money to hire a technician to keep the robot running. And the people who sell the robots don't know much about the FRP business."

It appears that the typical FRP processor is not financially capable of a serious interest in robotics. "The biggest market segment for FRP is still the boating industry," Binks' McCullough says, "and a robotic plant would need air conditioning and conveyorized mold-handling lines to ensure that the mold winds up in exactly the same location each time. They wouldn't be able to hand-push they parts throughout the plant like they do now, and a robot would be up and running all the time in an environment full of overspray. There have been a lot of robotic system failures and cancellation of equipment programs in simpler operations than FRP, such as robotic painting."

Magnum's Hedger isn't sure how mechanized FRP spray-up can become. Most processors do not use continuous production lines, "which would be the most efficient way for a robot to work," he says. Since the majority of FRP processors are small shops, automation is unlikely. Only large manufacturers building a small variety of parts on a production line are likely to automate. Hedger feels that "if the marine industry is ever to automate, it will be with impregnators or gantry-style robotics. On the other hand, the tub-and-shower manufacturers, some truck-cab makers and RV parts fabricators could automate on their production lines."

Rather than full-blown robotics, we will probably see more "automatics" in the next 10 years for repetitive, high-volume operations. More processors figure to use "smart" reciprocators with three axes (x-y-z) of motion and wrist-rotation ability. These reciprocators are run by programmable controllers to apply materials with a fixed stroke length, pattern, and spray duration.

An even more likely addition to the typical spray-up shop will be some sort of automated catalyst pressure sensing. This can be accomplished with a device that either warns the operator or shuts the system down completely when the catalyst flow exceeds or falls below preset limits. This would provide a degree of quality assurance by stopping the process before bad parts are made.

Binks has been offering such a monitoring device for some time, while Magnum introduced one earlier this year. Later this month, Glas-Craft is introducing one at the Fiberglass Fabrication Association conference in New Orleans, and GS Manufacturing is also developing such a device. Venus-Gusmer expects to offer a catalyst monitoring device that uses flow meters, rather than just pressure sensing, within the next few months.

Binks' McCullough predicts, "We will see prices on this kind of equipment come down and improvements made to the point where you will see it on typical chopper and gelcoat systems. It's going to be necessary whether you are automated or not to include more monitoring systems on all kinds of flow-control equipment for either polyesters, urethanes, or epoxies. You want to stop production before making bad parts."

But even these improvements are difficult to sell to FRP processors. "Everybody talks quality," McCullough says, "but almost to a man, they buy price. It's easy to get into the FRP business with low capital investment, and a low-cost investment generally stays that way." The tide of the market can also hurt. as during slowdowns like at present, during which companies frequently seek cost savings first and worry about maintenance problems later. However, McCullough stresses that "companies that really aspire to quality do invest to get it."

Poly-Craft's Cavanaugh doubts that spray-up equipment will become much more mechanized and automated, because "Spray-up has always been labor intensive. However, there will always be some people marrying robots and reciprocators to reduce labor," Goodman of Glas-Craft points out that "all of our guns are designed so they can be attached to a robot arm," but he adds, "We have not had a lot of calls for automation. There have been some in the Far East, but it has been very market-driven."

Venus-Gusmer is one of the few suppliers that is optimistic about prospects for greater automation in the 90s. "Based on our own experiences," Raymer says, "most large-scale molders of panels for construction and transportation are moving toward large, enclosed machinery, which isolates the worker from the spray-up process through mechanization. Reciprocating or robotic spray heads, and automated mat or woven roving wet-out systems will replace traditional hand-held spray guns within the next 10 to 20 years. The cost of computer motion control equipment is very rapidly declining to the point where fully developed robots should be commonplace in every spray-up industry."

Adds Magnum's Hedger, "We believe that if robotics continue to get better and simpler to use and understand, then more shops will be willing to go to automation. Most of the shops out there were started by individuals and families that grew up using hand lay-up and spray-up, and they understand this very well. To bring in an automated robot would be taking away that hands-on understanding. It takes time to break old ways, and maybe with more schools teaching composite lay-up procedures, we will begin to see more of a trend toward automation. But some spray-up will always be done manually as there will continue to be many small shops."

Regardless of how automation fares, Venus-Gusmer's Raymer feels that "there will probably never be a total elimination of spray-up as an application process due to the efficiency of the method for applying large amounts of material at fact application rates."

However, Binks' McCullough thinks that in 10 years, "we will see more large FRP companies and fewer smaller ones, because of advancing technology requirements. Processors will have to be more sophisticated to survive, whether that means operating advanced equipment or meeting government regulations. Spray-up is going to diminish as a volume method. It's feasible that it won't be around at all in 10 years, which would cause a lot of products to be made otherwise."

GREATER USE OF IMPREGNATORS

Mechanized impregnators, used with mat or fabric reinforcement, may become more popular in the next decade for making parts that are typically sprayed-up today. The impregnator first mixes catalyst and resin together, and then it compresses the mixture into fabric that is continuously fed from a roll. The system often operates from an operator-controlled gantry that drapes the wetted fabric over the mold (see PT, April '90, p. 35).

These machines are typically used on large parts now, reportedly providing 20-30% reduction of styrene emissions compared with spraying. "The more transfer-efficient your spray-up equipment is, then the lower the percentage improvement if you switch to an impregnator," Binks' McCullough says. "But if you cut out spraying totally, then you obviously reduce all of that styrene emission to zero. So then the only emissions come from the exothermic reaction during part curing."

Magnum has just introduced a fabric impregnator, joining Binks and Venus-Gusmer, who also supply such machinery. Hedger says that Magnum's customers opt for the purchase of higher-efficiency equipment such as impregnators and internal-mix spray systems because of the reduction of styrene fumes. The company also offers conversion kits to turn late-model conventional spray equipment into these more efficient setups.

CLOSING THE MOLD FOR RTM

There are some similarities between RTM and FRP spray-up that have led spray-up equipment suppliers to also sell RTM equipment. Spray pumps can be adapted for RTM, although the internal mixing of RTM requires a few more controls than does external mix. Some existing spray-up systems can be converted RTM although plenty of them cannot, suppliers say. Necessary features for RTM are said to include the internal-mix head, positive-displacement catalyst pump, flow controls, pressure regulators, and backpressure valves. Benefits of RTM over open-mold spray-up include greater control over processing, reduced emissions, higher glass content, and the freedom to put items such as inserts and intends into the mold.

Suppliers say typical FRP processors want to learn more about RTM. Two years ago, Glas-Craft started RTM systems, a joint venture with Plastech TT, of the U.K., which offers RTM training, equipment, and mold building technologies. "Every FRP shop that you go into, small or large, has thought about RTM," according to Glas-Craft's Keegan. "A lot of open-mold FRP parts will go to RTM using the same resins and glass, but you can't just put a lid on an open mold," he says.

Venus-Gusmer's Raymer expects a continuing shift from open molding to RTM, and Hedger says that Magnum gets "many more customer inquiries on RTM than in the past." He expects the company's spray-up machines to continue to sell in the 90s, but at a slower pace. "There will always be spray-up machines," he said, "because they are inexpensive and allow any entrepreneur to try his hand in building a fiberglass product. Hand spray-up machines will always be used as a back-up and for small work, though much of the small work could eventually be done with RTM if the quantities are right."

An example of a high-volume FRP processor involved in RTM is the Bayliner Div. of Brunswick's US Marine Corp., Everett, Wash. The boatmaker currently uses RTM to produce platforms with urethane cores and glassmat reinforcement. Bayliner hopes to expand the process into other applications in the future, according to Rich Lathrop, manager of FRP development and methods.

Regardless of what happens in the marine industry, one area that figures to remain a promising market for open-mold spray-up is that of architectural components and fascia. Wesley Shamp, architectural product manager at Molded Fiber Glass Companies in Union City, Pa., says that if open molding was not available for the company's recent work on Donald Trump's Taj Mahal casino, "it would have been done in another material or not done at all. The components are too large, too intricate, and there are too few of them. The future in that market wouldn't lend itself to the cost that would be involved for a closed molding process such as RTM."

Poly-Craft's Cavanaugh sees some large-volume motor-home parts manufacturers switching to closed molding, and most makers of boats, swimming pools, and architectural shapes staying with spray-up. "Tooling costs really dictate what process is employed. Spray-up will always be the process of choice whenever tooling costs for RIM and RTM are not justified," he says.

Goodman of Glas-Craft is confident that "open molding is going to be around forever because of economics--the low cost of tooling. And if you want a Class-A or show surface, you're still going to have to spray gelcoa even if you inject the mold. Also, extremely large parts will be difficult to RTM. Processors will use spray-up to start projects, and if the part catches on, they may shift to RTM," he says.

According to Binks' McCullough, "RTM is definitely going to grow, but I don't think the growth will be tremendously rapid. It has been talked about since 1975 or 1976, and it still encompasses only a very small percentage of the market. I doubt that more than 25% of the FRP population will invest in high-tech methods or RTM. Government pressure will be the strongest motivator, and cost-effective payback is an economic necessity."

PHOTO : Improved catalyst mixing and higher resin/glass transfer efficiency will characterize

PHOTO : spray-up equipment R&D in the '90s. Environmental challenges will drive these innovations

PHOTO : into practice. (Photo: Dow Chemical)

PHOTO : Even if processors switch to RTM to make a part, they may still need to spray gelcoat to

PHOTO : assure a Class A, showroom finish on products such as boats, bathroom fixtures, and

PHOTO : whirlpools. (Photo: Glas-Craft)

PHOTO : Molding architectural fascia will remain a promising opportunity for spray-up processors.

PHOTO : Much of the fascia for Donald Trump's Taj Mahal casino in Atlantic City (left) was

PHOTO : produced via open-mold spray-up (above) by Molded Fiber Glass/Union City. The company used

PHOTO : 517 molds to make 500,000 sq ft of FRP laminate for the project.
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Title Annotation:fiber-reinforced plastics
Author:Evans, Bill
Publication:Plastics Technology
Date:Oct 1, 1990
Words:4106
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