Tensile Strength Of EpoxiesTensile Strength Of Epoxies

Santa Rosa Junior CollegeEngineering 45

Peter Breyfogle, Michael Eddy, Ben Valdovinos, Ibrahim Mansour9 December 2009

History of Epoxies

• The word epoxy is derived from two Greek prefixes - epi, which means "upon" and oxy, which means "sharp/acidic".

• The first commercial attempts to prepare resins from epichlorohydrin were made in 1927 in the United States. Credit for the first synthesis of bisphenol-A-based epoxy resins is shared by Dr. Pierre Casta of Switzerland and Dr. S.O. Greenlee of the United States in 1936.

www.axminster.co.uk/images/products/ZPOX5_l.jpg

History• Dr. Castan's work was licensed

by Ciba, Ltd. of Switzerland, which went on to become one of the three major epoxy resin producers worldwide.

• Ciba's epoxy business was spun off and later sold in the late 1990s and is now the advanced materials business uni of Huntsman Corporation of the United States.

Applications

• Paints and coatings• Adhesives• Industrial tooling and composites• Electrical systems and electronics• Consumer and marine applications• Aerospace applications• Art

Epoxy-Paintings and Coatings

• "2 part waterborne epoxy coatings" are used as ambient cure epoxy coatings.

• These non-hazardous, two-part epoxy coatings are developed for heavy duty service on metal substrates and use less energy than heat-cured power coatings.

• The coating dries quickly providing a tough, UV resistant, protective coating with excellent ultimate hardness, and good mar and abrasion resistance.

• They are designed for rapid dry protective coating applications.

www.prestwich.ndirect.co.uk/.../epoxyresin.jpg

Epoxy-Paintings and Coatings• Low volatility and water clean up.

– factory cast iron – cast steel – cast aluminum applications

• For automobile and industrial uses• Polyester epoxies are used as powder coating

for washers, driers and other "white goods". • Epoxy coatings are also widely used as primer.

– improve the adhesion of automotive and marine paints

– Metal cans and containers are often coated with epoxy to prevent rusting.

product-image.tradeindia.com/.../Epoxy-Paint.jpg

Epoxy-Adhesive• Epoxy adhesives are a major part of the

class of adhesives called "structural adhesives" or "engineering adhesives"

• Exceptional adhesives for wood, metal, glass, stone, and some plastics

• Can be made flexible or rigid, transparent or opaque/colored, fast setting or extremely slow setting

• Some epoxies are cured by exposure to ultraviolet light. Such epoxies are commonly used in optics, fiber optics, optoelectronics and dentistry.

• Used in the construction of aircraft, automobiles, bicycles, boats, golf clubs, skis, snow boards,.– and other applications where high

strength bonds are required http://www.made-in-china.com/showroom/magpow/product-detailDoBxteiJOEYF/China-Super-Strong-Epoxy-Adhesive-Glue-.html

Epoxy-Industrial Tooling and Composites

• Used in producing fiber-reinforced or composite parts. • This "plastic tooling" replaces metal, wood and other traditional

materials, and generally improves the efficiency.• Lowers the overall cost• Shortens the lead-time for many industrial processes • Epoxy systems are used in industrial tooling applications.

– Produce: • Molds• master models• Laminates• castings• Fixtures• and other industrial production aids.

Epoxy-Industrial tooling and composites

http://www.directindustry.com/prod/master-bond/epoxy-casting-resin-17407-198115.html

http://esciencenews.com/files/images/200903261308930.jpg

Epoxy-Electrical Systems and Electronics• employed in motors, generators,

transformers, switchgear, bushings, and insulators

• epoxy resins are the primary resin used in overmolding integrated circuits, transistors and hybrid circuits, and making printed circuit boards.

• Flexible epoxy resins are used for potting transformers and inductors.

• The cured epoxy is an electrical insulator and a much better conductor of heat than air.

• Transformer and inductor hot spots are greatly reduced, giving the component a stable and longer life than unpotted product.

http://www.robotroom.com/Flashing-Sneakers/Epoxy-Encapsoluted-Circuit-With-Coin-Cell.jpg

Epoxy-Consumer and marine applications• Amateur building projects including

aircraft and boats • Epoxy materials tend to harden

somewhat more gradually, while polyester materials tend to harden quickly.

• Epoxies are used for commercial manufacture of components where a high strength/weight ratio is required

• Polyester thermosets typically use a ratio of at least 10:1 of resin to hardener (or "catalyst"), while epoxy materials typically use a lower ratio of between 5:1 and 1:1.

• Used during boat repair and assembly • Sold as:

– separate resin and hardener – repair resins for marine applications http://www.morrison-marine.com/service_and_repair_

project_pages/epoxy_current/epoxy2.jpg

Chemistry of Epoxy

•Epoxies consist of two components•Part A consists of an epoxide (resin)•Part B is the curing agent (hardener)•A chemical reaction occurs between the two parts generating heat and hardening the mixture into a hard inert plastic.

Part A: Resin

• Most epoxy resins are produced from a reaction between epichlorohydrin and bisphenol.

• When epichlorohydrin and bisphenol-A mix together to form a covalent bond, the resulting polymer is rigid and strong.

• Also used for protective coatings, high performance composites, and adhesives.

Part B: Hardener

• Hardeners consist of Polyamine monomers• Play a major role in:

– Tensile Strength– Compression– Gel Time– Viscosity– Demolding Time

Mix

• Most epoxies mix at a 1-1 ratio• Allows consumers to measure by eye-balling.• Measure by either volume or weight, depending on

the epoxy.• Extra resin or hardener weakens the epoxy.• Other specialized epoxies require other ratios and

more careful measuring.

Mix

• After being mixed together the epoxy goes through a curing process.

• Process can be controlled through temperature and choices of resin and hardener compounds.

• The curing process can take minutes to hours.• Some formulations benefit from heating during

curing.• Others simply require time, and ambient

temperatures.

Epoxy

• Epoxy adhesion is due to the strong polar bond the epoxy makes with the surface.

• After the two epoxy parts are combined there is a working time (pot life) during which the epoxy can be applied or used.

• The pot life will be anywhere from minutes to one hour or longer.

Facts

• After cured, epoxies can handle temperatures well below freezing.

• They mostly soften at about 140°F, but will harden when cooled.

Our Project

• Our purpose was to test the tensile strength of six different types of epoxy– In addition to the base epoxies, two epoxy-carbon fiber

composite samples were tested• To contrast the behavior of epoxies under tension, we tested

a sample of Nylon 101

Procedure

1. Cast a mold in the shape required by the tensile strength testing machine.

2. Use this mold to cast the epoxies into tensile specimens.

3. Test to find the yield and tensile strengths, as well as Young’s Modulus of Elasticity for each epoxy.

•The mold was made using a Silicone RTV system. •This system is a TAP plastics proprietary two-part silicone that need to be mixed together. • After mixing, the solution was poured into a rectangular column with the original standing upright in the middle• After 48 hours, the silicone solution sets in the desired shape

Making the Mold

Casting the Tensile Specimens

The four Devcon epoxies were generously donated by the Devcon company.http://www.devcon.com

Devcon 5-MinuteTensile Yield Strength: 1860 PSIUltimate Tensile Strength: 1860 PSIModulus of Elasticity: 179,977 PSI

Shafting EpoxyTensile Yield Strength: 1504 PSIUltimate Tensile Strength: 1504 PSIModulus of Elasticity: 108,169 PSI

System 3Tensile Yield Strength: 1310 PSIUltimate Tensile Strength: 1540 PSIModulus of Elasticity: 67,874 PSI

Devcon 5-Minute GelTensile Yield Strength: 300 PSIUltimate Tensile Strength: 598 PSIModulus of Elasticity: 57,622 PSI

Devcon 2-ton with Carbon Fiber Strands

Tensile Yield Strength: 1774 PSIUltimate Tensile Strength: 1774 PSIModulus of Elasticity: 223,899 PSI

Devcon 2-ton with Chopped Carbon Fibers

Due to a sizable air bubble running throughout the length of the tube, the Devcon 2-ton with chopped carbon fibers failed before any meaningful data could be collected.

Nylon 101 and SiliconTensile Yield Strength: 1184 PSIUltimate Tensile Strength: 3774 PSIModulus of Elasticity: 161,724 PSI

Tensile Strength of Epoxies

Tensile Strength of Epoxies (Zoomed)

Conclusion• Tensile Strengths

The epoxy with the highest yield strength was the Devcon 5- minute epoxy, which tested at a maximum of 1860 PSI,

and a Young’s Modulus of 179,977 PSI The Devcon 2-ton with the addition of carbon fiber strands

came in second place, with a maximum tensile strength of 1774 PSI, and a Young’s Modulus of 223,899 PSI The System 3 epoxy yielded the third highest tensile strength of

1540 PSI, and a Young’s Modulus of 67,874 PSI, followed closely by the Shafting Epoxy, which failed at a maximum tensile strength of 1504 PSI, and a Young’s Modulus of 108,169.

The quick-set 5 minute epoxy failed at a tensile strength of 598 PSI, and a Young’s Modulus of 57,622 PSI resulting in the lowest maximum tensile strength and Young’s Modulus.

Errors and Oversights

To try and eliminate the amount of air bubbles in the shafts, we could have elevated the temperature at which the epoxy was poured, cast it in a vacuum, or had a different mold set-up.

Image from Materials Science and Engineering: An IntroductionBy Callister, 7th ed

Works Cited

•Materials Science and Engineering: An IntroductionBy Callister, 7th ed

•http://en.wikipedia.org/wiki/Epoxy•http://www.epotek.com/•http://www.hempel.com/Internet/InecorporateC.nsf/vHEMPELDOC/085E68EB4DA0

1C29C1256EBB0034D1C1?OpenDocument&1•http://www.absoluteastronomy.com/topics/Epoxy•http://www.epoxyandepoxyflooring.com/epoxyresins/epoxyresins.htm•http://www.epoxyproducts.com/25points4u.html