Polymers for Heavy Engineering

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Polymers for Heavy Engineering
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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.

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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

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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.

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• 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

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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).

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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.

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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

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• 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.

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Rubber Applications in Earthquake Bearing Industry
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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
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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

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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.

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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.

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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.

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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.

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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
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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
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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
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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.

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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.

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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.

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Processing Flow Chart - Seismic Rubber Bearings