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Polymers in Civil Engineering

Polymers in Civil Engineering. “Poly” “meros” = many parts Monomer = non-linked “mer” material Polymers = long continuous chain molecules formed from repeated sequences of small organic units (mers). molecular weight in excess of 10,000. Polymerization .

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Polymers in Civil Engineering

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  1. Polymers in Civil Engineering • “Poly” “meros” = many parts • Monomer = non-linked “mer” material • Polymers = long continuous chain molecules formed from repeated sequences of small organic units (mers). molecular weight in excess of 10,000.

  2. Polymerization • the use of heat, pressure or a chemical catalyst to link monomer material into polymer chains.

  3. Thermosetting plastic a polymer material that cannot be reformed after manufacturing cross linked chain networks less creep, isotropic good structural properties injection molded Thermo plastic a polymer that can be remolded after manufacturing. softens upon reheating substantial creep, isotropic properties extrusion (PVC pipe) or molding (PET soda bottles) Plastic Types

  4. Natural Polymers • · wood • · leather • · cotton • · rubber • · wool • · asphalt

  5. Manufactured Polymers • Epoxy (thermosetting) • Polyesters (thermoplastic or thermoset) • Sulfur Concrete (thermoplastic) • Methyl Methacrylate (MMA) • Polyurethane • Polystyrene (thermoplastic) • Polyvinyl chloride, PVC (thermoplastic) • Polyethylene (thermoplastic)

  6. Epoxy (thermosetting) • Physical Properties • Strength and Moduli vary with temperature and formulation • Thermal coefficient greater than concrete • Brittle behavior (more brittle than concrete) • Excellent adhesion - tenacious bond • High tensile and compressive strength • Highly resistant to chemical attack and wear

  7. Epoxy • Disadvantages and limitations • Properties are very sensitive to mixing and proportioning procedures • Some cannot be used in moist environments • Strong Allergenic, safety • Some have strong oder prior to polymerization • Physical properties are substantially different from other materials

  8. Epoxy • Applications • Adhesive (old concrete to new concrete, welding cracked concrete, bonding diverse materials) • Patching voids • Durable overlays and coatings

  9. Polyesters • Thermoplastic or Thermoset • Physical Properties • Strength and Moduli vary with temperature and formulation • Thermal coefficient greater than concrete

  10. Advantages Good Chemical Resistance Easy to use Good strength Good ductility Inexpensive Disadvantages and Limitations Some have marginal bond quality More expansion and shrinkage than concrete Polyesters

  11. Applications of Polyester • · Floor coatings • · Protective coatings • · Adhesive bonder or sealer • · Binder for fiberglass or artificial wood • · Sealer for Epoxy injection • · Anchoring for drilled holes • · Binder for polymer mortar

  12. Sulfur Concrete (thermoplastic) • Physical Properties • Modulus of Elasticity similar to concrete • Thermal expansion greater than concrete • Advantages • Exceptional chemical resistance • Cold joints preventable • Rapid Strength gain (80%@ 2 h; 100%@ 24 h) • High strength (7000 psi) • Will set below freezing

  13. Disadvantages Requires special equipment Special handling required - high temperature (280°F) Will melt at 246°F Few applicators Applications High chemical resistance floors, etc. Rapid pavement repair or construction Sulfur Concrete

  14. Methyl Methacrylate (MMA) • Thermoset • Physical Properties • clear or any color • thermal expansion higher than concrete • low viscosity (< water) • high strength

  15. Advantages Rapid Strength Good bond to dry surfaces Easy to mix Pre-packaged mixes Impermeable to water resistance to acids excellent abrasion resistance Disadvantages expensive hazardous (fire) odor more shrinkage than concrete MMA

  16. MMA • Applications • Plexiglas • Pavement of bridge decks • Thin Overlays (3/16"+) • Impregnation • precast elements

  17. Advantages water resistant dimensional stability inexpensive Disadvantages low tensile strength low modulus poor heat resistance poor weather resistance brittle, low toughness Polystyrene (thermoplastic)

  18. Polyvinyl chloride, PVC • Thermoplastic • Physical Properties • Tensile 10-41 MPa (1500 - 6000 psi) • Compressive 55-110 MPa (8000 - 16000 psi) • 200 - 15 % elongation • t = 75 x 10-6 in./in./°C • E = 3.6 Gpa (5 x 105 psi)

  19. Advantages excellent insulator diverse applications chemical resistance long-term stability flame resistant weather resistant Adhesion to glass resistance to oil Disadvantages low modulus Moisture sensitivity in production PVC

  20. PVC • Applications • pipe • raincoats • window frames and moldings • electrical cables • floor tiles • siding

  21. Polyethylene (thermoplastic) • Physical Properties • E = .13 GPa (.19 x 105 psi) • t = 1.0 x10-4/°F • tensile strength 13.8 MPa (2 ksi) • Advantages • tough, durable, weather resistant • chemical and moisture resistance • excellent electrical properties

  22. Polyethylene • Applications • sheet plastic, membranes, liners • pipe, electrical conduit • tanks, bottles

  23. Polyurethane • Physical Properties • Sensitive to temperature and RH • low elastic moduli 4- 400 ksi • Advantages • Resistant to Chemicals • lightweight and resistant to wear • Closed Cell material when used with foams • Cryogenic performance

  24. Polymer Composites An Overview

  25. Composites with Thermoplastics • Glass Fiber Composites (20-40% wt) • Monofilament • Braided Strand • Chop Fiber • Polymer • Polypropylene (PP), Polycarbonate (PC), Polyethylene Terephthalate (PET), Polybutylene Terephthalate (PBT), Nylon

  26. Typical Properties

  27. What is FRP? • FRP stands for Fiber Reinforced Plastic • FRP is used in structural shapes, repair materials or as reinforcement for concrete • FRP is a composite material consisting of artificial fibers encased in a resin matrix

  28. Fiber Types Glass Poly-Vinyl Alcohol (PVA) Carbon Aramid (Kevlar) Resin Types Epoxy Polyester Resins are thermosetting Materials Used in FRP

  29. Manufacture of FRP Rods • Pultrusion • Enables a high percentage of fibers to be included in the cross section • Braiding • Creates surface deformations which enhance the FRP to concrete bond • Hybrid Rods

  30. Engineering Properties of FRP • High Tensile Strength • On average, the tensile strength of FRP is 10% to 500% greater than steel • Low Moduli of Elasticity • With the exception of Carbon rods, FRP has only 1/10 to 1/2 the modulus of steel • Linear Stress-Strain Relationship

  31. Applications of FRP • Reinforcement bars for Concrete • Prestressing Tendons for Concrete Members • FRP sheets can be used to increase flexural strength in weakened or underdesigned members

  32. Advantages of FRP • Will Not Corrode In Field Conditions • Lightweight • Strong in Tension • Methods of Construction Same as Steel Reinforcement

  33. Disadvantages of FRP • Low Moduli of Elasticity • Cannot be Shaped in the Field • More Expensive than Steel • Coefficients of Thermal Expansion are Different than Those of Steel or Concrete

  34. Conclusion FRP Reinforcement is an Engineered Material that Shows Great Promise In the Future of Civil Engineering

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