Tensile Strength Of Epoxies Santa Rosa Junior College

Tensile Strength Of Epoxies Santa Rosa Junior College Engineering 45 Peter Breyfogle, Michael Eddy, Ben Valdovinos, Ibrahim Mansour 9 December 2009

History of Epoxies www. axminster. co. uk/images/products/ZPOX 5_l. jpg • 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 Dr. S. O. Greenlee of the United States in 1936.

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 1990 s 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 http: //www. made-in-china. com/showroom/magpow/productdetail. Do. Bxtei. JOEYF/China-Super-Strong-Epoxy-Adhesive-Glue-. html • 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

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-17407198115. 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/epoxy 2. 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.

Making the Mold • 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

Casting the Tensile Specimens • Six epoxies were tested for this experiment • Devcon 5 -minute • Shafting Epoxy • System 3 • Devcon 5 -minute gel • Devcon 2 -ton with carbon fiber strips • Devcon 2 -ton with chopped carbon fibers The four Devcon epoxies were generously donated by the Devcon company. http: //www. devcon. com

Devcon 5 -Minute Tensile Yield Strength: 1860 PSI Ultimate Tensile Strength: 1860 PSI Modulus of Elasticity: 179, 977 PSI Devcon 5 -min 2000 1800 Stress (PSI) 1600 1400 1200 1000 800 600 400 200 0 0 0. 002 0. 004 0. 006 Strain 0. 008 0. 012 0. 014

Shafting Epoxy Tensile Yield Strength: 1504 PSI Ultimate Tensile Strength: 1504 PSI Modulus of Elasticity: 108, 169 PSI Shafting Epoxy 1600 Stress PSI 1400 1200 1000 800 600 400 200 0 0 0. 002 0. 004 0. 006 Strain 0. 008 0. 012 0. 014

System 3 Tensile Yield Strength: 1310 PSI Ultimate Tensile Strength: 1540 PSI Modulus of Elasticity: 67, 874 PSI System 3 1800 1600 Stress (PSI) 1400 1200 1000 800 600 400 200 0 0 0. 02 0. 04 0. 06 Strain 0. 08 0. 12 0. 14

Devcon 5 -Minute Gel Tensile Yield Strength: 300 PSI Ultimate Tensile Strength: 598 PSI Modulus of Elasticity: 57, 622 PSI 5 -Min Gel 700 Stress (PSI) 600 500 400 300 200 100 0 0 0. 01 0. 02 0. 03 0. 04 Strain 0. 05 0. 06 0. 07

Devcon 2 -ton with Carbon Fiber Strands Tensile Yield Strength: 1774 PSI Ultimate Tensile Strength: 1774 PSI Modulus of Elasticity: 223, 899 PSI Devcon 2 -ton w/CF 2000 1800 1600 Stress (PSI) 1400 1200 1000 800 600 400 200 0 -0. 002 0. 004 Strain 0. 006 0. 008 0. 01

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 Silicon Tensile Yield Strength: 1184 PSI Ultimate Tensile Strength: 3774 PSI Modulus of Elasticity: 161, 724 PSI Nylon 101 4000 3500 Stress (PSI) 3000 2500 2000 1500 1000 500 0 0 0. 02 0. 04 0. 06 0. 08 0. 1 Strain 0. 12 0. 14 0. 16 0. 18 0. 2

Tensile Strength of Epoxies Comparitive Stress Strain Curves for all Samples 4000 3500 3000 Nylon 101 Devcon 2 -ton w/CF 5 -Min gel Stress (PSI) 2500 2000 System 3 Tennis Club 1500 Devcon 5 min 1000 500 0 -0. 02 0. 04 0. 06 0. 08 0. 1 Strain 0. 12 0. 14 0. 16 0. 18 0. 2

Tensile Strength of Epoxies (Zoomed) Comparitive Stress Strain Curves for all Samples 2500 2000 Stress (PSI) Nylon 101 Devcon 2 -ton w/CF 5 -Min gel 1500 System 3 Tennis Club 1000 Devcon 5 min 500 0 -0. 01 0 0. 01 Strain 0. 02

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 1. Air Bubbles Air bubbles presented a major issue throughout this experiment. Since the epoxy was being poured into the mold lengthwise, it was almost impossible to completely eliminate bubbles from the tensile specimens, no matter how slowly and carefully the epoxy was poured. Air bubbles seemed to be the leading cause of most of the failures. Only the System 3 epoxy failed at the most narrow point, which means that defects acted as stress raisers. Examination of the break-surface of the other specimens showed the failure radiated from the imperfection 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 setup.

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

2. Surface Defects A surface defect (probably due an air bubble) on the surface of the Devcon 5 minute Gel caused the failure to happen at a considerable distance from the expected break point

Works Cited • Materials Science and Engineering: An Introduction By Callister, 7 th ed • http: //en. wikipedia. org/wiki/Epoxy • http: //www. epotek. com/ • http: //www. hempel. com/Internet/Inecorporate. C. nsf/v. HEMPELDOC/085 E 68 EB 4 DA 0 1 C 29 C 1256 EBB 0034 D 1 C 1? Open. Document&1 • http: //www. absoluteastronomy. com/topics/Epoxy • http: //www. epoxyandepoxyflooring. com/epoxyresins. htm • http: //www. epoxyproducts. com/25 points 4 u. html