Cellulose Plastics

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Cellulose Plastics
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Cellulose Plastics

• Introduction
• Cellulose is a natural polymer produced from
  wood via wood pulp.
• Woven grade cotton contains about 90 cellulose
  while an average wood has about 50 and the
  balance is composed of lignin and
  polysaccharides.
• Cellulose resins include four organic esters,
  cellulose acetate (CA), cellulose acetate
  butyrate (CAB), cellulose acetate propionate
  (CAP) and cellulose acetate triacetate (CAT).

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• In 1927, Eastman Kodak Co. commercialized
  cellulose acetate into photographic film base.
• Molding grade of CA was introduced in 1935.
• In 1938, Eastman introduced CAB.
• CAP was introduced in 1960.

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Polymerization

• The cellulose esters are prepared by reacting
  chemical cellulose with organic acids and
  anhydrides using sulfuric acid as a catalyst.
• In the standard synthesis of CA, the reaction
  proceeds with acetic acid and acetic anhydride
  to the triester stage. CA is prepared by
  hydrolyzing the triester to remove some of
  its acetyl groups. Plastic grade CA contains 38
  to 40 acetyl.

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• The propionate and butyrate esters are made by
  substituting propionic acid and propionic
  anhydride or butyric acid and butyric anhydride
  for some of the acetic acid and acetic
  anhydride.
• Plastic granules of CAP contain 39 to 47
  propionyl and 2 to 9 acetyl. CAB contains 26 to
  39 butyryl and 12 to 15 acetyl.

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When A is and B is Plastic is H
H Cellulose CCH3 CCH3 Cellulose
acetate
O
O   CCH3
CCH2CH3 Cellulose acetate propionate
O
O   CCH3
CCH2CH2CH3 Cellulose
acetate butyrate
O
O   CCH2CH3
CCH2CH3 Cellulose propionate
O
O   CH2CH3
CH2CH3 Ethyl cellulose   NO2

NO2 Cellulose Nitrate
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Cellulose Esters

• Cellulose Acetate
• Introduction
• Manufacturing of cellulose acetate was done in
  1865 using a process in which cotton was heated
  with acetic anhydride in sealed tube at
  130-1400C but the process was difficult to
  control.
• With further research various new techniques of
  manufacturing of cellulose acetate are
  developed.

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• One of the methods available today is
  homogenous acetylation.
• In this process cellulose is pretreated with
  glacial acetic acid to open up the cellulosic
  matter.
• After pretreating, acetylation is done by
  mixing pretreated cellulose with acetylating
  agent like acetic anhydride, a catalyst like
  concentrated sulphuric acid and acetic acid as
  diluent.

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Properties

• - High water absorption
• - Poor electrical insulation characteristics
• - Limited aging resistance
• - Limited heat resistance
• - Dissolved by wide variety of reagents

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Properties of Cellulose acetate
Name Value Unit
Specific gravity 1.28 --
Tensile Strength 40 MPa
Tensile modulus 2174 MPa
Flexural modulus 1794 MPa
Elongation at break 38
Impact Strength (Izod ) 160 J/m
Hardness R62 ---
HDT (under 1.82 MPa load.) 61 C
Melting point 240-260 C
Glass transition temperature 157 C
Dielectric Strength 13.4 KV/mm
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Applications
CA Different applications
Spectacles
Tool handles
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Cellulose Acetate Butyrate (CAB)
Bleached Wood Pulp 40-50 H2SO4
Pretreated for 12 hours
Drying with Acetic acid
Etherification of treated cellulose with mixture
of Butyric acid and acetic anhydride H2SO4
( Catalyst)
Cellulose acetate butyrate
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Properties

• - Good toughness
• - Excellent appearance
• - Giving good coating with hard glossy surface
• - Lower water absorption
• - Better flow properties
• - Lower density

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Properties of Cellulose Acetate Butyrate
Name Value Unit
Specific gravity 1.19 --
Tensile Strength 34.5 MPa
Tensile modulus 1725 MPa
Flexural modulus 1449 MPa
Elongation at break 50
Impact Strength (Izod ) 187 J/m
Hardness R75 ---
HDT (under 1.82 MPa load.) 65 C
Dielectric Strength 13.4 KV/mm
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Applications

• - Toys, tools handles, tabular keys, telephone
  housing, pipes for conveying water, outdoor
  display signs, vacuum formed products and
  protective coating for metals.

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Cellulose Acetate Propionate

• - Cellulose Acetate Propionate having shorter
  side chain and it is harder stiffer, and posses
  higher tensile strength than Cellulose Acetate
  Butyrate.
• - Easy to vacuum form and also tend to be used
  for applications like tool handles, safety
  lockers, steering wheels, etc.

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Properties

• - Cellulose Acetate Propionate have shorter side
  chain and it is harder, stiffer and possess
  higher tensile strength than Cellulose Acetate
  Butyrate. Like cellulose acetate butyrate, this
  is easy to vacuum form and also tends to be used
  for applications like tool handles, safety
  lockers, steering wheels, etc.

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Cellulose Nitrate

• - Cellulose Nitrate is manufactured by the
  reaction between cellulose, nitric acid and
  sulphuric acid.
• - It is possible to vary degree of
  etherification according to the root hydroxyl
  group which is replaced by nitrate group.
• - Fully nitrated cellulose, cellulose
  tri-nitriate is an explosive.
• - Cellulose nitrate is precipiticised with
  camphor in order to make it easy processable.

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Properties of Cellulose Nitrate

• Good rigidity
• Water white transparency
• Poor chemical resistance
• Reasonable toughness
• Capable of forming highly attractive
  multi-coloured sheeting
• Highly inflammable.

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Applications

• The one time important application was in
  photographic film.
• Today the principal outlet are knife
  handles,table tennis ball and spectacle frames.
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