Different FRP Resin Chemistries for Different Chemical Environments

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Jeffry Potter
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1 Differet FRP Resi Chemistries for Differet Chemical Eviromets Do Kelley, Jim Graham, Thom Johso Ashlad Performace Materials ABSTRACT The corrosio challeges posed by differet chemical eviromets madate the use of a variety of resis for the fabricatio of durable fiberglassreiforced plastic (FRP) equipmet. Differet resi chemistries ca provide widely differet performace i a give chemical eviromet. To a great extet, the chemical resistace of FRP depeds largely upo the resi compositio used to ecapsulate glass fiber reiforcemets ad lock them ito a desired shape. The purpose of this paper is to provide a overview ad history of FRP resi chemistries that ca be used i various chemical eviromets ad how these chemistries ca affect FRP corrosio performace. INTRDUCTIN Sice the itroductio of fiberglass-reiforced plastic (FRP) ito chemical processes more tha half a cetury ago, improvemets i resi chemistry ad fabricatio techiques have made FRP highly competitive with corrosioresistat metal alloys such as stailess steel ad Hastelloy. May factors go ito makig FRP projects successful, but success always begis with choosig the appropriate resi for the chemical eviromet i which the equipmet will be used. I corrosio applicatios, resis ecapsulate glass fiber reiforcemets to provide them with protectio from chemical attack. I order for a resi to be suitable for a give chemical eviromet, it must be resistat to the chemical at the various cocetratios ad operatig temperatures to which it will be subjected. Followig a brief descriptio of early FRP use, this paper will look at the chemistry of corrosio-resistat FRP resis startig i the 1950 s, ad the trace their evolutio ito the 21 st Cetury. Followig World War II, FRP first gaied promiece as a costructio material for radar domes ad marie vessels. I fact, the first large-scale use of FRP was i the pleasure boat idustry. Fiberglass vessels were lightweight, less expesive to costruct tha woode vessels, ad possessed excellet corrosio resistace to seawater. However, the polyester resis used for buildig boats, (Figure 1), were ot suitable for most chemical-resistat applicatios. These resis have multiple ester groups alog the backboe - from which the ame polyester was derived. Ester groups are ofte susceptible to chemical attack. As a result these resis were ot cosidered to be suitable for more aggressive eviromets such as chlorie, bleach, caustic, ad strog acids. 1

2 H H = 3 to 6 Figure 1. Typical Polyester Resi Backboe with Multiple Ester Groups By the late 1950's, the use of FRP equipmet had expaded to chemical processig eviromets as well as pulp bleachig plats. I these applicatios FRP materials replaced more expesive ad ofte less durable metal alloys, rubber lied steel, ad wood. I the late 1960's, epoxy viyl ester resis were itroduced, sigificatly improvig FRP service life via further ehaced chemical resistace ad toughess. The use of FRP i aggressive chemical eviromets was further improved with the itroductio of ovolac epoxy viyl ester resis i the early 1970 s with greater resistace to both heat ad orgaic solvets. Corrosio-resistat resi techology cotiues to evolve ad improve as it adapts to the ever-growig demads of the corrosio market. EARLY CHEMICAL RESISTANT RESIN CHEMISTRY I the 1950 s, chemically resistat FRP resis were foud primarily i the pulp ad paper ad chemical process idustries. The first polymers used to fabricate corrosio-resistat composites were polyester resis sythesized from Bispheol A ad Fumaric acid. I the pulp ad paper idustry, Bispheol Fumarate based FRP replaced the wood ad tile materials which were curretly employed i chlorie dioxide storage ad pulp bleachig. The chemical structure for this type of polyester resi is show i Figure 2. FRP made from these resis has superior resistace to both oxidizig ad caustic eviromets as compared to the earlier polyester resis used to make boats. Cosequetly, these resis have also bee used extesively i the chemical process idustry, (e.g. Chlor Alkali productio). H H Figure 2. Bispheol A Fumarate Polyester Resi Polymer Structure 2

3 The ext chemical-resistat resi to be itroduced was Chloredic Acid Polyester resi (show i Figure 3). FRP made with Chloredic Polyesters is particularly resistat to wet chlorie gas as well as oxidizig acids such as Nitric acid, Sulfuric acid, ad Chromic acid. It is still widely used by chlorie maufacturers today. However, it ad most polyester resis are ot suitable for caustic eviromets. H H Figure 3. Chloredic Polyester Resi Polymer Structure Both Chloredic ad Bispheol Fumarate resis provided a big improvemet i corrosio performace over earlier polyester resis. Ufortuately, FRP made from these resis teded to crack, ot oly durig use, but also durig fabricatio ad trasport. New techology was eeded to make tougher, crack-resistat FRP without reducig its chemical resistace. EPXY VINYL ESTER RESINS I the late 1960 s, Bispeol A Epoxy Viyl Ester resis aswered this challege. FRP made with Bispheol A Viyl Esters was much tougher tha earlier polyester techology. These tougher composites were also much more resistat to mechaical ad thermal stress. As a result, FRP made from Bispheol A Viyl Esters could be used i a wide variety of chemical eviromets. Moreover, they possessed a icreased level of chemical resistace equal to or better tha more expesive high ickel alloys such as C- 276 ad superior to 2205 duplex (ferritic / austeitic) stailess steel (see Table1). 3

4 Table1. The Chemical Resistace of FRP Made From Epoxy Viyl Ester Resi Compared to 2205 Stailess Steel ad Alloy C-276 Materials Sulfuric Acid Hydrochloric Acid Acid Chloride Salts FRP Made with Epoxy Viyl Ester Resi 2205 Stailess Steel 100ºC to 30% 30ºC to 30% 80ºC to 15% 60ºC to 1% 100ºC all cocetratios 65ºC to 2000 low ph Alloy C ºC to 30% 80ºC to 15% 65º to 50,000 ppm@ low ph Figure 4 highlights the chemical structure of Bis Pheol A Viyl Ester resis. Note that these resis have oly two ester groups per molecule (highlighted below). This is sigificat i that ester groups ca be susceptible to chemical attack. Fewer ester groups geerally traslates to better chemical resistace. The Bispheol A epoxy group, show i the brackets, imparts toughess to the resi makig it more resistat to thermal ad mechaical stress. These resis also have multiple ether likages which further add to their chemical resistace. Fially, the resi backboe has multiple hydroxyl groups (-H) that fuctio to ehace adhesio to fibers ad other composite materials (through hydroge bodig). FRP equipmet based upo Bispheol A Epoxy Viyl Ester resis has bee so successful i chemical service that they have largely displaced Bispheol Fumarate resis ad have become the idustry stadard i the corrosio-resistat resi market. C H 2 C H 3 H H 3 C H H C H 2 CH 3 = 1 to 3 Figure 4. Bispheol A Epoxy Viyl Ester Resi Polymer Structure 4

5 Epoxy Viyl Ester resis were agai improved i the early 1970 s with the icorporatio of Novolac chemistry. Novolac fuctioality eables FRP equipmet to withstad higher service temperatures. Novolac Epoxy Viyl Ester resis are also characterized by ehaced resistace to orgaic solvets. Reviewig Figure 5, oe ca see that the Novolac Epoxy Viyl Ester has three viyl groups per molecule. Whe these groups polymerize, they form a highly cross-liked polymer. Cross-likig makes it more difficult for solvets to peetrate the lamiate structure ad also icreases the polymer s glass trasitio temperature thus providig improved heat resistace. H C 2 H H H H C H 2 C H 3 C 3 H = 1 to 6 H 2C Figure 5. Epoxy Novolac Viyl Ester Resi Structure The ext major developmet was the itroductio of bromiated epoxy viyl ester resis. These resis delivered fire retardace i additio to corrosio resistace a key requiremet for FRP equipmet i may idustrial applicatios. Fire retardace is achieved through the icorporatio of bromie ito the polymer backboe as show i Figure 6. The bromie fuctioality ot oly provides superior fire retardace, but it also ehaces the resi s resistace to corrosio i sodium hypochlorite (bleach) service. omiated epoxy viyl ester resis additioally deliver ehaced FRP toughess ad fatigue resistace over stadard epoxy viyl ester resis. H 2 C C H 3 H H 3 C H H CH 2 CH 3 = 1 to 3 Figure 6. omiated Epoxy Viyl Ester Resi Structure 5

6 SUMMARY Resi chemistry is the key to FRP performace i ay eviromet, especially where chemical resistace is required. Early chemical-resistat polyester resis while superior to may metal alloy alteratives had problems with mechaical ad thermal stress which ca be directly attributed to their chemical structure. With a uusual combiatio of chemical resistace ad toughess, epoxy viyl ester resis have come to domiate the chemicalresistat resi market for FRP. Kowledge of resi chemistry is the key to uderstadig why differet resi chemistries are required for differet eviromets. 6

POLYMERS

POLYMERS Short Aswer Questios: **1.What is PHBV? How is it useful to ma? As. PHBV is Poly β-hydroxy butyrate-co- β-hydroxy valerate.it is a biodegradable polymer. It is used i speciality packig, orthopaedic