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Polymers for Heavy Engineering

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Title: Polymers for Heavy Engineering


1
Polymers for Heavy Engineering
2
Silicones, or polysiloxanes
  • Silicones, or polysiloxanes, are
    inorganic-organic polymers with the chemical
    formula R2SiOn, where R organic groups such
    as methyl, ethyl, and phenyl.
  • These materials consist of an inorganic
    silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...)
    with organic side groups attached to the silicon
    atoms, which are four-coordinate.

3
Silicones, or polysiloxanes
  • In some cases organic side groups can be used to
    link two or more of these -Si-O- backbones
    together. By varying the -Si-O- chain lengths,
    side groups, and crosslinking, silicones can be
    synthesized with a wide variety of properties and
    compositions.
  • They can vary in consistency from liquid to gel
    to rubber to hard plastic. The most common type
    is linear polydimethylsiloxane or PDMS

4
Silicones, or polysiloxanes
  • Service temperature to about 260C
  • Good chemical resistance, low water absorption,
    good electrical properties, available in flame
    retardant grade
  • In the plumbing and automotive fields, silicone
    grease is often used as a lubricant. In plumbing,
    the grease is typically applied to O-rings in
    faucets and valves.

5
  • In the automotive field, silicone grease is
    typically used as a lubricant for brake
    components since it is stable at high
    temperatures, is not water-soluble

6
Epoxy
  • Epoxy or polyepoxide is a thermosetting epoxide
    polymer that cures (polymerizes and crosslinks)
    when mixed with a catalyzing agent or "hardener"
  • The family of epoxy resin includes
    epichlorohydrin with bisphenol-A (range from low
    viscosity liquids to high molecular weight
    solids).

7
Epoxy
  • Epoxy adhesives are a major part of the class of
    adhesives called "structural adhesives" or
    "engineering adhesives"
  • These high performance adhesives are used in the
    construction of aircraft, automobiles, bicycles,
    golf clubs, skis, snow boards, and other
    applications where high strength bonds are
    required.
  • In general, epoxy adhesives cured with heat will
    be more heat- and chemical-resistant than when
    cured at room temperature.

8
Epoxy
  • Novolacs are another important class that offer
    higher thermal properties and improved chemical
    resistance
  • The cycloaliphatics types important for the
    applications requiring high resistance to
    wheatering

9
  • Epoxies typically are not used in the outer layer
    of a boat because they are deteriorated by
    exposure to UV light
  • In the aerospace industry, epoxy is used as a
    structural matrix material which is then
    reinforced by fiber. Typical fiber reinforcements
    include glass, carbon, Kevlar, and boron.

10
Rubber Applications in Earthquake Bearing Industry
11
INTRODUCTION
  • Bearings - structural joints that are installed
    between a structure and its foundation.
  • The bearing is very stiff and strong in the
    vertical direction, but flexible in the
    horizontal direction.

1.0 Introduction
12
HOW THE BEARING WORKS
Figure Base-Isolated and Fixed-Base Buildings
  • A base isolated structure is supported by a
    series of bearing pads which are placed between
    the building and the building's foundation

13
2.0 How The Bearing work?
  • As a result of an earthquake, the ground beneath
    each building begins to move.
  • Each building responds with movement which tends
    toward the right.
  • The building's displacement in the direction
    opposite the ground motion is actually due to
    inertia.

14
2.0 How The Bearing work?
  • In addition to displacing toward the right, the
    un-isolated building is also shown to be changing
    its shape-from a rectangle to a parallelogram.
    deforming
  • The primary cause of earthquake damage to
    buildings is the deformation which the building
    undergoes as a result of the inertial forces
    acting upon it.

15
2.0 How The Bearing work?
  • The base-isolated building retains its original,
    rectangular shape.
  • It is the elastomeric bearings supporting the
    building that are deformed.
  • It implies the inertial forces acting on the
    base-isolated building have been reduced.

16
ELASTOMERIC BEARINGS
Fig Basic structure of rubber bearing
3.0 Elastomeric Bearings
  • Consist of thin rubber sheets bonded onto thin
    steel plates and combined with an energy
    dissipation mechanism.
  • The rubber sheets are vulcanized and bonded to
    the thin steel plates under pressure and heat.
  • it is designed in such a way that bearing is very
    stiff and strong in vertical direction, but
    flexible in horizontal direction.
  • Thick mounting steel plates are bonded to the
    bottom and top surfaces allowing the isolator to
    be firmly connected to the foundation below and
    the superstructure above.

17
TYPES OF ELASTOMERIC1. LEAD RUBBER BEARINGS (LRB)
  • a bigger laminated bearing
  • manufactured from layers of low-damping natural
    rubber sandwiched together with layers of steel
    and a lead cylinder plug firmly fitted in a hole
    at its center to deform in pure shear.
  • lead inserted as center core of bearing
    dissipates the energy of earthquake while the
    rubber, reinforced with steel plates, provide
    stability, supports structure and isolate
    vibration.
  • LRB provide initial rigidity, due to the high
    elastic stiffness of lead, which is essential for
    minor lateral loads.

4.0 Types Of Elastomeric Bearing
18
2. HIGH DAMPING RUBBER BEARING (HDRB)
  • Consists of thin layers of high damping rubber
    sandwiched between steel plates.
  • High-damping rubber is filled rubber compound
    with inherent damping properties due to the
    addition of special fillers, such as carbon and
    resins. The addition of fillers increases the
    inherent damping properties of rubber without
    affecting its mechanical properties.
  • When shear stresses are applied to high-damping
    rubber, a sliding of molecules generates
    frictional heat which is a mechanism of energy
    dissipation.

4.0 Types Of Elastomeric Bearing
19
3. Hybrid type Lead High-damping Rubber Bearing
(LHDRB)
  • Consist of layers of high-damping rubber
    sandwiched between steel plates and a smaller
    diameter lead cylinder plug firmly fitted in a
    hole at its center.
  • LHDRB has both an initial rigidity, due to the
    presence of the lead plug, and a continuous
    energy dissipation mechanism, due to the damping
    properties of the high-damping rubber.

4.0 Types Of Elastomeric Bearing
20
Requirements for Rubber Bearings
5.0 Requirements
  1. Mechanical and damping properties of the bearing
    must remain constant over the whole life of the
    structure
  2. Ability to return to its original configuration
    and dimensions when unloaded
  3. Elastomeric bearings must be strong and stiff for
    vertical loadings and flexible under shear
    stresses
  4. The base isolator must support the vertical load
    of the structure with a large safety factor.
  5. The sheer stiffness of the isolator must be low
    enough to attenuate the majority of the frequency
    components in an earthquake on that site.

21

5.0 Requirements
  1. The isolator must be stiff enough vertically to
    power significantly amplification of any vertical
    component in the earthquake.
  2. During an earthquake, the building will move
    sideways on the isolators. At the extremes of the
    movements, the bearing must continue to support
    the vertical load of the structure.
  3. The damping in the isolators must be sufficient
    to prevent a build- up of amplitude in the
    structure during an earthquake.
  4. Motion of the structure during high winds should
    not be sufficient to disturb the occupants.
  5. The isolator should provide a restoring force so
    the building will always return to its original
    rest position.

22
BEARING MATERIALS
6.0 Raw Materials
  • Natural Rubber and Polychloroprene
  • Ethylene Propylene Rubber as a promising
    alternative to Natural Rubber and
    Polychloroprene will be consider as the raw
    material for earthquake bearing elastomer.

23
Processing Flow Chart - Seismic Rubber Bearings
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