6.3

Cards (41)

  • Polymers
    • Generally organic compounds based on carbon, hydrogen, and other non-metallic elements
    • Have large molecular structures
    • Typically have low densities and may be extremely flexible
  • Polymers
    • Plastics
    • Rubbers
  • Polymer applications
    • PVC pipes
    • Rubber tires
    • Polyurethane coated polyester raincoat
    • Kevlar helmet
  • Polyethylene
    Easily formed into thin, airtight film
  • Kevlar
    High tensile strength
  • Plastics
    Materials that have some structural rigidity under load, and are used in general-purpose applications
  • Classification of Plastics
    • Polyethylene
    • Polypropylene
    • Poly(vinyl chloride)
    • Polystyrene
    • Fluorocarbons, epoxies, phenolics
    • Polyesters
  • Plastics
    • Some are very rigid and brittle
    • Others are flexible and experience considerable deformation before fracture
    • Either thermoplastic or thermosetting
  • Plastics applications
    • Polystyrene and poly(methyl methacrylate) are used when optical transparency is critical
    • Fluorocarbons is used for coatings on nonstick cookware, bearings and bushings, and high temperature electronic components
  • Trade Names, Characteristics, and Typical Applications for a Number of Plastic Materials
    • See table
  • Elastomers
    • Properties depends on the degree of vulcanization and on whether any reinforcement is used
    • Mechanical properties, even vulcanized rubbers, are not satisfactory and may be improved by additives such as carbon black
  • Natural rubber
    Still utilized to a large degree because it has an outstanding combination of desirable properties
  • SBR
    The most important synthetic elastomer (Automobile tires, reinforced with carbon black)
  • NBR
    Used when highly resistant to degradation and swelling is required
  • Silicone elastomers

    • Posses a high degree of flexibility at low temperatures (to -90°C) and yet are stable to temperatures as high as 250°C
    • Used in automobile engine compartment
  • Biocompatibility
    Property of silicone elastomers
  • Fibers
    • Polymers that are capable of being drawn into long filaments having at least a 100:1 length-to-diameter ratio
    • Used in textile industry, being woven or knit into cloth or fabric
    • Aramid fibers are employed in composite materials
    • Convenience in washing and maintaining clothing depends primarily on the thermal properties of the fiber polymer
    • Must exhibits chemical stability to a rather extensive variety of environments, including acids, bases, bleaches, dry cleaning solvents, and sunlight
    • Must be Relatively nonflammable and amenable to drying
  • Coatings
    • Applied to the surface of materials to protect the item from the environment that may produce corrosive or deteriorative reactions, to improve the items appearance, or to provide electrical insulation
    • Mostly organic polymers
  • Coatings
    • Paint
    • Varnish
    • Enamel
    • Lacquer
    • Shellac
  • Latex
    A stable suspension of small insoluble polymer particles dispersed in water, most common coatig
  • Adhesives
    • Substance used to bond together the surfaces of two solid materials (termed "adherends")
    • Mechanical bonding - There is an actual penetration of the adhesive into surface pores and crevices
    • Chemical bonding - Involves intermolecular forces between the adhesive and adherend
  • Adhesives
    • Natural adhesives (animal glue, casein, starch, and rosin)
    • Synthetic polymers (Polyurethanes, Polysiloxanes (silicones), Epoxies, Polyimides, Acrylics, Rubber material)
  • Films
    • Polymeric materials fabricated and used extensively as bags for packaging food products and textile products
    • Characteristics are low density, high degree of flexibility, high tensile and tear strength, resistance to attack by moisture and other chemicals, and low permeability to some gases
    • Having thicknesses between 0.025 and 0.125 mm (0.001 and 0.005 in.)
  • Foams
    • Plastic materials that contain a relatively high volume percentage of small pores and trapped gas bubbles
    • Both thermoplastic and thermosetting materials are used as foams (Polyurethane, rubber, polystyrene, poly(vinyl chloride))
    • Commonly used as cushions in automobiles and furniture as well as in packaging and thermal insulation
  • Composites
    • Consists of more than one material type
    • Designed to display a combination of the best characteristics of each of the component material
  • Composites
    • Fiberglass (Glass fibers embedded within a polymeric material, acquires strength from the glass and flexibility from the polymer)
    • Plywood
    • Fiberglass automotive spoiler
    • Carbon fiber bicycle frame
  • Composites
    Most are made of 2 phases: Matrix phase (continuous phase present throughout the material) and Dispersed phase (surrounds and binds by matrix phase)
  • Composites
    • Properties varies depending on the concentration, size, shape, distribution, and orientation of the dispersed phase
  • Composites applications
    • Aerospace
    • Underwater
    • Transportation
  • Classifications of Composites
    • Particle Reinforced Composites
    • Fiber Reinforced Composites
    • Structural Composites
  • Particle Reinforced Composites
    • Uses tiny particles as its dispersed phase
    • Classified based on reinforcement - Large Particle Composites and Dispersion Strengthened Composites
  • Large Particle Composites
    • The filler material replaces some volume of the material and modifies its properties
    • Examples are Concrete (cement - matrix, sand and gravel - particles) and Cermets (metal Cobalt or Nickel - matrix, ceramic Tungsten carbide or Titanium cabide - particles)
  • Dispersed Strengthened Composites

    • Phase interaction takes place at atomic or molecular level
    • Matrix phase - Metal / Metal Alloys,
    • Dispersed phase - Metal / Non-metal
    • Example is Thoria Dispersed Nickel -Type of Nickel Alloy with 3 % Thoria
  • Fiber Reinforced Composites
    • Fibers are characterized to their length to diameter ratio
    • Have high strength, stiffness, and greater elastic modulus
    • Classified as Continuously Arranged Fiber Reinforced Composites and Discontinuously Arranged Fiber Reinforced Composites
  • Continuously Arranged Fiber Reinforced Composites
    Have orderly aligned fibers
  • Discontinuously Arranged Fiber Reinforced Composites
    Discontinuous and/or Randomly arranged
  • Structural Composites

    • Made of Homogenous and composite materials
    • Classified as Laminar Composites and Sandwich composites
  • Laminar Composites
    • Composed of two-dimensional sheets or panels that have a preferred high-strength direction such as is found in wood and continuous and aligned fiber-reinforced plastics
    • Example is Plywood
  • Sandwich Composites
    • Designed to be light-weight beams or panels having relatively high stiffnesses and strengths
    • Consists of two outer sheets, or faces, that are separated by and adhesively bonded to a thicker core
    • Used in roof, floors, walls
  • Biomaterials
    • Components planted into the human body for replacement of diseased or damaged parts
    • Must not produce toxic substances (inert) and must be compatible with body tissues
    • All material types may be used