Polymers in Civil Engineering Poly meros many parts

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

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

Natural Polymers · · · wood leather cotton rubber wool asphalt

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

Epoxy (thermosetting) Physical Properties n n n 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

Epoxy Disadvantages and limitations n n n 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

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

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

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

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

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

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

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

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

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

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

Polyvinyl chloride, PVC Thermoplastic Physical Properties n n n Tensile 10 -41 MPa (1500 - 6000 psi) Compressive 55 -110 MPa (8000 - 16000 psi) 200 - 15 % elongation t = 75 x 10 -6 in. /°C E = 3. 6 Gpa (5 x 105 psi)

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

PVC Applications n n n pipe raincoats window frames and moldings electrical cables floor tiles siding

Polyethylene (thermoplastic) Physical Properties n n n E =. 13 GPa (. 19 x 105 psi) t = 1. 0 x 10 -4/°F tensile strength 13. 8 MPa (2 ksi) Advantages n n n tough, durable, weather resistant chemical and moisture resistance excellent electrical properties

Polyethylene Applications n n n sheet plastic, membranes, liners pipe, electrical conduit tanks, bottles

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

Polymer Composites An Overview

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

Typical Properties E, GPa Ft, MPa ey PP 5 70 -90 0. 02 PC & PBT 8 120 0. 02 Aramid 80 -170 3500 - Carbon 34 -800 5000 - 200 400 0. 002 Steel

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

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

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

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

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

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

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

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