In-situ polymerization

1. AMINA.P.E
2nd M Sc BPS
CBPST, KOCHI

2. Introduction to composites:
 Definition:A composite material can be defined as a
macroscopic combination of two or more distinct material
having arecogenisable interphase between them.
 It consist of a continuous phase & discontinuous phase.
 continuous phase is called matrix & discontinuous phase is
called reinforcement, which is stronger than the
continuous phase

3. Category of fibers &matrix for
composites:
 Fibers:
Natural fibers
Synthetic organic fibers
Aramid fiber
Polyethylene fiber
Synthetic inorganic fibers
Glass fibers
Alumina fibers
Boron fibers
Carbon fibers
Si C fibers
Whiskers(SiC is available in the form of whiskers, i.e., small
single crystals):A few tens of microns in length and less than
one micro in diameter.

4.  Matrix:
Polymer (polymeric composites)
Metals (metal matrix composites)
Ceramic (ceramic matrix composites)
Carbon (carbon/carbon composites)

5. Nanocomposites:
 Polymer nanocomposites are also called polymer nanostructured materials.
 They are materials of which composition includes at least one constituent with
dimensions less than 100 nm.
 Their feature is that the nanoscale constituents can drastically improve and/or
modify properties and functionality of the macroscopic material.
 A challenge in developing the nanocomposites is to make exceptional
properties (mechanical, optical, etc.) of the nanomaterials obvious at the
micro- and macroscale levels of the hosting bulk materials.

6. Nanoparticle classification:
 Isodimensional or zero-dimensional; the same size in all directions;
aspect ratio is close to unity (L/D ~1). examples: spherical silica,
metallic nanoparticles, carbon black, fullerenes.
 Fibrillar; examples: carbon nanotubes and cellulose nanofibrils.
 Layered; examples: clay mineral and synthetic.
 The most common nanofillers used (inorganic):
Clays,
Carbon nanotubes,
Carbon black,
Fumed silica,
Cellulose-based fibrils as organic nanofiller.

7. Basic preparation methods:
 Solution dispersion,
 Melt dispersion,
 Sol–gel processing,
 In situ polymerization,
 Self-assembly (layer-by-layer technique).

8. What is In Situ?
In situ is a Latin phrase which translates literally
to 'In position'.
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9. What is In –situ technique?
 Involve a chemical reaction resulting in the formation
of a very fine and thermodynamically stable
reinforcing phase within a matrix.

10. In -situ polymerization process:
 Nanoparticles are dispersed in a liquid monomer or
relatively low-molecular-weight precursor as well as in
their solution.
 When a homogeneous mixture is formed, initiator is added
and it is exposed to appropriate source of heat, light, etc.
 The polymerization performed in situ results in the
nanocomposite.
 Polymers thus synthesized are called thermoset.

11.  Polymerization can be processed either within a mould cavity or
in some other in situ situation.
 Thermosets are usually covalently cross-linked that does not
allow them to reshape. They can be reused by granulating and
using as a filler.
 Nylon-6 was first used to develop nanocomposites by in situ
polymerziation of caprolactam monomer.
 Epoxy, phenolic, bismaleimide and cyanate polymers as
thermosets are applied to manufacture nanocomposites.

12.  To promote the crosslinking process, the curing of these
polymeric material usually needs the use of a hardener or
catalyst.
 In a case, for example, epoxies, such cross-linkers as
amines, anhydrides, and Lewis acids are applied.
 The disadvantage of use of curing agents is that they
modify the physical properties and influence the
functionality of nanocomposites.

13. Advantages :
• There is thermodynamic compatibility at the matrix-
reinforcement interface.
• Also, the reinforcement surfaces are likely to be free of
contamination~ Therefore, stronger matrix dispersion bond
can be achieved.
• Important for the preparation of insoluble and thermally
unstable polymer composites, which cannot be processed by
solution or melt processing.
• For preparation of polymer composites with high nanotube
loading, in-situ provides very good miscibility with almost any
types of polymers.

14. In -situ polymer processing:
• In-situ polymerization methods used to fabricate CNT-
PMMA composites by incorporating CNTs during the
course of polymerization of MMA.
• Basic starting materials:
1. Nanotubes
2. MMA monomer
• Method: In-situ free radical polymerization method
involves polymerization of monomer using a radical
initiator such as 2.2´-azobisisobutyronitrile (AIBN).
• CNTs are dispersed through ultrasonication in the
prepolymer.

15.  Adding CNT at prepolymer provides good dispersion in
the low viscosity of the prepolymer.
 As the polymerization progresses, the viscosity of the
solution increases and the polymer grows and wraps
around the dispersed CNTs.
 Benefits:
a) Higher interfacial strengths as CNTs interact with the
growing polymer, thus forming stronger CNT-polymer
bonds via non-covalent or covalent interactions.
b) Composites with enhanced mechanical, electrical
and tribological were obtained.

16. Ingot Metallurgy
(Synthesis of composites)
Al (99.9%) +
Ti (99.7%)
Graphite powder
(40-50 μm)
Heated
1100 °C – 1200°C
1h
1300 °C – 1400°C
10 minutes
Mixture direct chill
cast into ingot bars
Melt in
graphite-lined
induction
furnace with
argon gas flow.
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17. Example of ingot metallurgy:

18. PRECIPITATION

19. PMMA/GO COMPOSITE:
• The method for achieving controlled dispersion of graphene
oxide(GO) , in PMMA via the precipitation polymerisation
process in a water/methanol mixture.
• GO act as surfactant and adsorbs on the interface between
polymerised PMMA particles and solvent mixture.
• SEM confirmed that the precipitate consist of particles
surrounded by the GO sheets. Compression molding of the
precipitate yields a polymer nano composite with GO organized
into a regularly spaced 3D network which percolates at 0.2 wt %
GO.

20. DIAGRAM