The Chemistry of Silly Putty

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The Chemistry of Silly Putty
Composition of Silly Putty
Bond Types
Tetrahedral structural unit of silica (SiO2),
The siloxane unit

• The polymers in silly putty have covalent bonds
  within the molecules, but hydrogen bonds between
  the molecules.
• These hydrogen bonds are easily broken, when only
  small amounts of stress are slowly applied to the
  putty. Only a few bonds are broken and thats why
  the putty can stretch".
• When larger amounts of stress are applied
  quickly, there are many hydrogen bonds that
  break, and that is why it can also rip apart

65 - Dimethyl Siloxane 17 - Silica   9 -
Thixotrol ST (castor oil derivative)   4 -
Polydimethylsiloxane   1 - Decamethyl
cyclopentasiloxane   1 - Glycerine   1 -
Titanium Dioxide
Glycerine

Titanium Dioxide
Polydimethylsiloxane
Cyclopentasiloxane
Structure of the major component of caster oil
Silicones
What is an Inorganic Polymer?
This is a single boric acid

• Polyorganosiloxanes have empirical formulas of
  R2SiO, and are called silicones.
• Silicones are viscoelastic materials. They behave
  like liquids at high temperature or when allowed
  to flow over a long period of time. They behave
  like elastic solids or elastomers at low
  temperature. The elastic behavior comes from the
  very flexible silicon-oxygen bonds. When the
  molecular weight is high, these flexible chains
  become loosely entangled which imparts a high
  level of viscoelasticity.
• Polydimethylsiloxane has repeating (CH3)2SiO.
  Altering the number of repeat units (value of n)
  in the chain and the degree of cross-linking
  which ties multiple polymer chains together
  generates polymers possessing different physical
  properties. Since silicon-chlorine bonds are very
  susceptible to cleavage by water,
  polydimethylsiloxane can be synthesized by
  hydrolyzing dichlorodimethylsilane.
• The initial hydrolysis reaction exothermically
  generates a silanol Si(CH3)2(OH)2 which condenses
  through the loss of water to form the siloxane
  polymer. Since dichlorodimethylsilane is
  bifunctional (has two chlorines). The Chain will
  then spread in two directions, and this generates
  high molecular weight polymers which retain some
  residual hydroxyl groups. The residual hydroxyl
  groups react with boric acid B(OH)3 to form
  Si-O-B linkages between polysiloxane chains.
  Since boric acid is trifunctional, a single boron
  has the ability to join three polysiloxane chains
  together. This joining of chains is called
  cross-linking. Cross-linking produces a high
  molecular weight polymer that is a soft and
  flexible.

This is an example of boric acid hydrogen bonding.
It is large molecules, usually linear or branched
chains with atoms other than carbon in their
backbone
Thixotrol
A Thixotropy is the property of certain gels or
fluids that are thick (viscous) under normal
conditions, but flow (become thin, less viscous)
over time when shaken, agitated, or otherwise
stressed.
How its Made
Fun Fact
You can actually make your own homemade version
of silly putty. solution of 55 Elmer's glue
solution in water solution of 16 sodium borate
(Borax) in water food coloring (optional)
Ziploc bags Mix together 4 parts of the glue
solution with one part of the borax solution. Add
food coloring, if desired. Refrigerate the
mixture in the sealed bag when not in use.

• Silly Putty is an inorganic polymer
• One way to make the polymer is by reacting
  dimethyldichlorosilane in diethyl ether with
  water. The ether solution of the silicone oil is
  washed with an aqueous sodium bicarbonate
  solution. The ether is evaporated off. Powdered
  boric oxide is added to the oil and heated to
  make the putty.
• The initial reaction is also known to be violent