Overview of Resins used in FRP Equipment

Corrosion Mining, and Infrastructure Symposium 2013 Digging Down and Building Up With Composites May 15-16 – Denver, Co

Overview of Resins used in FRP Equipment

Michael Stevens

Principal Scientist Ashland Performance Materials

Resin fundamentals Importance of veil Requirements for Successful applications Testing for corrosion resistance Summary and conclusions

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Presentation Notes

Text points as shown in slide text above

• Resin Selection

• Design/Engineering

•Writing Specifications

• Fabrication

• Inspection

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A successful application must include these factors.

• Chemicals • Concentrations (Max./Min.) • Temperatures (Operating/Max./Min.) • Upsets • Flame Resistance • Abrasion • Insulation •Manufacturing Process

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These factors must be considered in selecting a resin for an application.

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Thermoset Thermoplastic

Candle Egg

Resins / Polymers

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The HETRON and AROPOL vinyl ester and polyester resins used for corrosion control applications are unsaturated thermosetting resins. Once cured, thermosetting resins cannot be reshaped with the application of heat (egg). They are not the same as the saturated polyester resins such as used in Mylar film or clothing which are commonly referred to as simply polyesters. Polyethylene, PVC and so forth are thermoplastic materials which can be reformed with the application of heat (candle). The advantage of thermosets is how easily they process - investment in equipment is minimal and custom molding is about the same cost as production line cost. The advantage of thermoplastics is the performance in relationship to the raw material cost of the resin. Since one has to basically melt the thermoplastic to do anything with it, it has to melt well above its end use temperature. This takes expensive and highly specialized equipment.

Thermoset Resins Unsaturated Isophthalic Polyester resins Chlorendic Polyester resins Bisphenol A Fumarate Epoxy vinyl ester resins Epoxy Resins Furfural Alcohol Resin

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Bisphenol-A Fumarate Polyester

1950 1960 1970 1980 2000

Chlorendic Polyester

Isophthalic Polyester

Dual Laminates

Vinyl Ester

Novolac V.E. Hi-Performance V.E.

1990

Improved HDT EVERs

Improved Toughness EVERs

“50 Years of Proven Performance”

Unsaturated Isophthalic Polyester resins

Chlorendic Polyester resins

Bisphenol A Fumarate

Epoxy vinyl ester resins

Epoxy Resins

Furfural Alcohol Resin

General Purpose

Strong acids and oxidizers

Acids and bases

Acids, bases, tough

High pressure piping Organic solvents and caustic

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Polyester resins are a reaction of a difunctional acid and a difunctional alcohol (glycol). The reaction forms an ester with water given off as a by-product.

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Polyester Components

Cross linking acid

Glycol

Functional Acid

Glycols

Propylene glycol (PG)

Dipropylene glycol (DPG)

Ehtylene glycol (EG)

Diethylene glycol (DEG)

Neopentyl glycol (NPG) Functional Acids

Orthophthalic acid

Isophthalic acid

Terephthalic acid

DCPD

Adipic acid

Presenter

Presentation Notes

There are two basic components in making a polyester resin – a bifunctional acid and a bifunctional alcohol. To build a polyester you combine an acid to a glycol and build the polymer. There are many acid type that will assist in defining viscosity, physical properties, corrosion resistance, reactivity. The various types of glycols affect the properties of the polymer similarly.

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Crosslinks with styrene

CH CH2 = liquid styrene monomer

A) SOLVENT B) COREACTANT

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The resulting polymer is a solid at room temperature. The components that make up the polymer have been chosen specifically for specific applications and product properties.

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Common POLYESTER Resins

OH C O

C O OH

O HO C =

OH = =

OH

OH

C O

C O HC HC

UNSATURATED THERMOPLASTIC POLYESTER

isophthalic acid

+

propylene glycol

+

fumaric acid

OH HC CH3

HC OH

Presenter

Presentation Notes

Now, we’re finally getting to unsaturated polyesters. As the name states, these are polyesters with unsaturation, or vinyl groups, or double bonds in them. Every unsat. PE we sell has either fumaric or maleic acid in it. This is a molecule with a double bond, or vinyl group in it, and two acid groups on it. The vinyl groups allow it to react with styrene, which is what you do, and the two acid groups allow it to react with alcohols to form polyesters, which is what we do.

Typical Applications: Aqueous environments Gasoline tanks Acids

Typical Applications: Aqueous environments Filament winding Impact resistance Thermal shock resistance

Presenter

Presentation Notes

NOTES: Make sure that the audience understands C-581, and are familiar with the corrosion guide.

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Cl Cl

Cl ClCl Cl

OO

O O

HO

CH3

O

CH3

CH3

O

O

O

H

• Exceptional corrosion properties in oxidizing acidic environments • Inherently fire resistant • Limited toughness

Typical Applications

Premium Corrosion Service Unmatched Corrosion

Properties in Oxidizing Acidic Environments

Presenter

Presentation Notes

NOTES: Fabrication critical refers to the need to avoid resin richness in a laminate.

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NOTES: Fabrication critical refers to the need to avoid resin richness in a laminate. This classic HETRON picture (white composite vs. rusty metal structure) shows the expected attack on the metal downflow tower which are now largely made out of FRP composite. Rather than being replaced, composites offer the versatility of being relined and rebuilt back to their original thicknesses which is particularly important for low cost life cycle and fast plant turnarounds. This is a pulp and paper application. This part would now be made from 980/35 or FR998/35. The demister blades are generally made from 197 although some are made from a BPA EVER. The cell covers were made by Ancor.

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CH3

CH3

O O

CH3

HO

CH3

O

O

O

O H

n

• Date back to the 1950’s • Originally used in pulp bleaching and chlorine dioxide storage • Later used in chlor-alkali production • Superior to earlier polyesters in both oxidizing and caustic environments

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Pulp & Paper

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EPOXY RESIN

O CH3

C CH3

O

bisphenol A

H2 C O

C H

C H2

Cl

+ epichlorohydrin

EPOX

Y

HO CH3

C CH3

OH

C H2

C H

CH2

O C H2

C H

CH2

O

Presenter

Presentation Notes

for whatevver reason, we have a special group of products we call vinyl esters. It is debatable what makes a vinyl ester a vinyl ester. Everyone agrees that they have a mono functional (only one acid or one alcohol) group with a vinyl group. What this means is you have terminal unsaturation, and much shorter polymers.

Epoxy resin properties dependent on hardener used to cure resin

Typical hardeners Aromatic amines Aliphatic amines Anhydrides

Ashland does not make Epoxy resins Used in high pressure pipe applications

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Chemical Structure

Features and Benefits

Novolac, Brominated, and Elastomer Modified Epoxy Vinyl Ester Resins

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What is an Epoxy Vinyl Ester Resin ?

• Epoxy methacrylate

• A reaction product of epoxy resin and methacrylic acid with a reactive diluent

• Styrene acts as a reactive diluent

• Cures at room and elevated temperature

• Compatible with all fabricating processes

Formation of Epoxy Vinyl Ester Resins - General Reaction Scheme

OO

OOH

O OO

O

OH

O OOH

O O

OH OHO

O

O

O

+

n=0-2

n=0-2

Bisphenol-A Epoxy ResinMethacrylic Acid

Polymerisation-

Catalyst

DT

Bisphenol-A Epoxy Vinyl Ester Resin

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Features of an Epoxy Vinyl Ester Resin

• Molecular Structure

OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

1. Terminal Carbon-Carbon double bonds promote reactivity & complete cure

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• Molecular Structure 2. Ester groups are subject to chemical attack or hydrolysis. An epoxy vinyl ester only has two ester

groups, a polyester has many

OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

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• Molecular Structure 3. Ester groups that do occur are protected from

hydrolysis and chemical attack by Methyl- shielding

OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

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• Molecular Structure 4. Multiple secondary Hydroxyl groups along the

molecule chain promote wetting and adhesion to glass fibers

OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

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• Molecular Structure 5. Less reactive (stable) ether bonds hold the chain

together

OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

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OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

• Molecular Stucture 6. Tough Epoxy Backbone

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OOH

O

CH3 CH3

OOH

OOOH

O

O

CH3

CH2

OCH3

CH2

n

CH3 CH3

• Summary Structure/Property Relations

Epoxy Backbone Toughness Sec. OH-Groups Adhesion & Wetting Methyl-group shielding Chem. Resistance Terminal C=C-Bonds Reactivity

Only two Ester groups per chain

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Bisphenol A Epoxy Vinyl Ester Resins

• Benefits – Broad corrosion resistance

superior to high alloy metals • Acids • Bases • Bleach • Salts • Solvents

– Tougnness – FDA Compliance

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Tough Resin Typical Applications:

Aqueous Mild organic solvents Acids Bases

Presenter

Presentation Notes

NOTES: 922 L HDT is 210

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O O H

O

O

C H 3

C H 2

n = 1 to 6

O O H

O

O

O H O

C H 3

C H 2

n

O

O

O O H

O O

C H 2 C H 3

High Crosslink Density = improved heat and solvent resistance

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Epoxy Novolac Resin Based Benefits

• Excellent Resistance to Oxidizing Acids • Superior High-Temperature Stability • Superior Solvent Resistance

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O O H

O O O H

O

O

C H 3

C O

O H O

C H 3

C H 2

n

C H 3 H 3 C

H 2

n = 1 to 3

O

O

Br Br

Br Br

Bromine on backbone = chemical stability and fire retardancy

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Brominated Epoxy-Based

Benefits • Fire Retardancy (By Bromination, Not

Additives)

• Broad Chemical Resistance • Excellent Toughness

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Presenter

Presentation Notes

NOTES: FR992-27 resin is available as a restricted product

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POLYESTERS

VINYL ESTERS

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One can think of VE’s and UPE’s like this. It is not accurate, but it is a good representation.

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CURING

R O : O R1 + + PROMOTER

R O •

R1 O PROMOTER

MEKP cobalt napthenate

free radical

LEVEL OF CATALYST LEVEL OF PROMOTER ANILINE

Presenter

Presentation Notes

You guys actually carry out this process in your shops. You take a peroxide, such as MEKP, and mix it into a promoted resin - usually with cobalt, and the MEKP starts breaking down to generate free radicals. If the cobalt is not diluted in the resin, this reaction is so powerful, it results in an explosion. Diluted in a resin, it just generates a steady stream of free radicals.

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VIS

CO

SIT

Y

TIME

GELATION

SOLID

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Used for its Solvent Resistance To 300° F. Fabrication Critical

Typical Applications

Excellent solvent resistance Acidic and basic resistance Reduced oxidizing resistance

Presenter

Presentation Notes

NOTES: These resins are cured with HETRON 803L-1, an acid catalyst. The resin is black opaque, has its own distinctive odor, laminates are very rigid, requires a high labor cost cure and post cure.

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ISOPHTHALIC CHLORENDIC BISPHENOL VINYL ESTER NOVOLAC VE FURAN

BASES SALTS ACIDS SOLVENTS

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Primary corrosion barrier – minimum of 100 mils – 2.6 mm

Chemical environment

Alternate layers of

mat/ woven roving

or filament winding

Optional Nexus veil layer

Resin/wax Topcoat With U.V. protection

C-veil or Nexus polyester veil - 10 mils - 0.25mm- 90% resin

Chopped strand mat - 1.5 oz/ft2 - 450g/m2 - 70 - 75% resin

Woven roving - 24 oz/yd2 - 800 g/m2 - 50 - 60% resin Or filament winding

• ASTM C581 Standard Construction

• Corrosion Barrier is Tested • Evaluation of Test Coupons

– Barcol Hardness – Flexural Strength – Flexural Modulus – Appearance – Weight and Thickness

Presenter

Presentation Notes

The standard practice for measuring the performance of the corrosion barrier for FRP equipment is the ASTM C581 Standard which is called, "Determining Chemical Resistance of Thermosetting Resins Used in Glass Fiber Reinforced Structures Intended for Liquid Service." The purpose of the ASTM C581 corrosion test is to evaluate the resin. A standard reinforcement and thickness is chosen to remove them as variables. This test determines how well the corrosion barrier protects the structure. The measurements of Barcol hardness, flexural strength, flexural modules, appearance, weight, and thickness changes are made over a period of one year to evaluate the performance of the corrosion barrier.

10 mil glass veil

3 plies 1.5 oz. glass mat

ASTM C-581 Test Coupon Standard Construction

*Not to Scale

Presenter

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The standard construction of the ASTM C581 laminate is basically a corrosion barrier with veil on either side. It is 1/8” thick, with the edges sealed to prevent wicking from the exposed glass fibers. The exposure to the chemical environment is accelerated because the corrosive attack is double sided. In actual service the attack is one sided. The test cannot be accelerated by increasing the temperature of the corrosive environment because the response is non-linear which makes the information not predictable.

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A typical laboratory set up where samples are totally immersed.

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Laminates from just one of the five test periods prior to their evaluation. As you can see, the type of resin has a significant impact on corrosion resistance. While one resin performs satisfactorily, another may fail. Many hundreds of laminates are being tested at any one time in our laboratory.

D, 1/4” thick

100

0 0 1 3 6 12

Months Exposure

F

% S

tren

gth

Ret

entio

n A

C B

D, 1/8” thick E

ASTM C-581 Laminate Strength Retentions Profiles

Pass

Fail

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When we actually run a C-581, the environment penetrates from either side. Because of this, the drop in physical properties is exaggerated. We have to remember, even this exaggerated drop in only in the corrosion barrier. Beyond this, we measure flexural properties, which focus on the surface of the laminate. Whereas tensile properties give a measurement of the average strength across the cross section, flexural measurements fail at the surface. The lines on the graph show the percent drop in flex strength different resins may have. This shows how thermosets differ from thermoplastics. The same graph for a TP would show no difference between 1/8” and 1/4”. There is no crosslinking, so a steady state, across the entire cross section is eventually reached. In a thermoset, we are looking for stabilization after an initial drop. E would be preferred to D. In aggressive, oxidizing environments, D is often the best choice available. One simple has to realize that a relining will be required after many years. An example of a “D” would be ClO2 / pulp & paper application where D is still better than the alternatives.

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C-glass, ECR glass or Boron free E glass = Chemically resistant glass.

Suitable for most environments except those attacking glass such as: hydrofluoric acid, sodium hydroxide and other chemicals.

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Polyester veil.

Polyacrylonitrile (PAN) veil. Developed for hydrofluoric acid and

sodium hydroxide applications. Apertured version best for visual and

corrosion properties.

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Used for certain chemicals, instead of C-veil, such as sodium hydroxide and hydrochloric acid. Used for electrical conductivity, such as for

FRP electrostatic precipitators and FRP fans, with grounding. Can be substituted by graphite used with

the resin in the corrosion barrier. Also used as target for spark testing behind

thermoplastics in a dual laminate construction.

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Veils

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E = Electrical grade glass. ECR or boron-free E Glass = Electrical corrosion resistant glass. ECR glass is less soluble in most acids than E- glass. It improves acid resistance at all acid concentrations and dramatically reduces strain corrosion at all acid concentrations.

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Type: E-glass = OK. ECR-glass or boron-free = better.

Applied in a corrosion barrier as two or three 1.5 oz/ft2 - 450 g/m2 layers with a 75% resin content .

Standard corrosion barrier: V/M/M - 100 mils – 2.6 mm.

Four or more plys may be specified depending on the chemical nature of the environment: 200 mils - 5.2 mm. This could go to 500 mils - 13 mm (for hot wet chlorine service).

Applied by hand lay up with the resin and rolled up for air

releasing. Used in alternate layers with woven roving in the laminate

structure.

FRP has been used for over 50 years in corrosion applications

Resin selection critical Corrosion barrier construction critical Reinforcements used will depend on required

structural properties

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Michael Stevens

Principal Scientist Ashland Performance Materials

Contact Information Email: [email protected] Phone: 614-790-3483 Cell Phone 614-264-1545

Documents

Overview of Resins used in FRP Equipment