LITERATURE SURVEY ON POLYMER NANOCOMPOSITE.

RAVI NARAIAN PANDEYM Tech.-2nd year.

DTU—DELHI.

INTRODUCTIONThe particles with small size in the range from a few to several tens of nanometers

are called quasizero-dimensional mesoscopic system,

quantum dots, quantized or Q particles, etc.

According Jordan et. al (2004) the nano-sized inclusions are defined as those that

have at least onedimension in the range 1 to 100 nm.

NANOCOMPOSITE STRUCTUREIn general, the structure of polymer/clay

nanocomposites are classified according to the level of intercalation and exfoliation of polymer

chains into the clay galleries.Various parameters including clay nature,

organic modifier, polymer matrix and method of preparation are effective.

PHASE SEPARATED STRUCTURE.

When the organic polymer is interacted with inorganic clay(unmodified),the polymer is

unable to intercalate within the clay layers and the clay is dispersed as aggregates or particles

with layers stacked together within the polymer matrix. The obtained composite structure is

considered as “Phase separated”.

INTERCALATED STRUCTURE.

When one or more polymer chains are inserted into the inter layer space and

cause to the increasing of the inter layer spacing , but the periodic array of the clay

layer is still exist ,the intercalated nanocomposite is formed.

EXFOLATED STRUCTURE.Exfoliated or delaminated structure is

obtained when the insertion of polymer chains into the clay galleries causes to the separation of the layers

one another's and individual layers are dispersed within the polymer matrix.

PREPARATION OF POLYMER/CLAY NANOCOMOPOSITES.

Many efforts have been made for the preparation of intercalated and exfoliated

polymer/clay nanocomposites with improved properties. A wide variety of polymer

characteristics including polarity, mol. Wt, hydrophobicity, reactive groups as well as clay characteristics such as charge density and its

modified structure and polarity are effective on the intercalation of polymer chains within the

clay galleries.

SOLUTION INTERCALATION.This is based on a solvent system in

which the polymer is soluble and the silicate layers are swellable. The silicate layers is first swollen in a

solvent ,such as chloroform. When the polymers and layered silicate solutions

are mixed ,the polymer chain intercalate and displace the solvent

within the remains ,resulting in nanocomposite.

INSITU INTERCALATIVE POLYMERIZATION.

In this method ,the layered silicate is swollen within the liquid monomer ,or a

monomer solution, so the polymer formation can occur between the inter calated sheets. polymerization can be initiated by heat or radiation, by the

diffusion of suitable initiator or by organic initiator.

TEMPLATE SYNTHESIS .This method is particularly adapted to

water soluble polymers and some attempts have been achieved with polymers such as

poly(vinyl pyrrolidine),HPMC,PANI,and PAN etc. The method for in situ

hydrothermal crystallization of a polymer hectorite nanocomposite consist in

refluxing for 2 days a 2 wt ℅gel of silica sol, MGOH sol , LIF and desired polymer in

water.

MELT INTERCALATION.Clay is mixed within the polymer

matrix in molten temperature .The conventional methods such as

extrusion and injection molding are used for dispersion of clay layers

within the polymers matrix.

THERMOPLASTICS NANOCOMPOSITE. Thermoplastics such as Polypropylene,

Polyethylene ,Ethyl vinyl acetate, Ethylene propylene diene

monomer ,Polyamide ,Poly ethylene terpthalate and polystyrene have

been used as polymer matrices for the preparation of nanocomposites.

ELASTOMERIC NANOCOMPOSITES.Burnside and giannelis have described

the two step preparation of silicone rubber based nanocomposites .first,

silanol-terminated poly(dimethyl siloxane) (Mw=18000) was melt

blended at room temperature with dimethyl –ditallow ammonium –

exchanged MMt, followed by cross linking of the silanol end groups with

tetra ethyl ortho silicate.

THERMOSET NANOCOMPOSITES.In situ polymerization has also been used for the preparation of different

of different thermosets nanocomposites. The studies of epoxy

system considered the ring opening polymerization of epoxides to form

polyether nanocoposites.

BIO DEGRADEBLE NANOCOMPOSITES.Natural and biodegradable polymers

are a new generation of polymers that are relatively friendly to the

environments with little or no impact when disposed.e.g. PLA,

Starch,Cellulose etc.

KEY FACTORS DURING SURVEING.(1) XRD and TEM are used routinely to measures basal spacing of organ clays,

and by inference to determine the conformation of the surfactants

hydrocarbons chains.No one has attempts to study the relationship between the spatial

distributions of charge within the clay lattice and surfactants structure.

(2)Wetting of organ clay is essential conditions ,but not a

single study exists in the literature in which attempts has been made

to measure the critical surface energy of the organoclay surface.

(3)Lack of recognition within the nanocomposite community that

the organoclay structure is in fact a lamellar liquid crystal.

CHALLENGES.

1. EXFOLIATION.

2.ORIENTATION.

3.COMPATIBILTY.

4.REAGRREGATION

CONCLUSION.

Polymer reinforced with as little as 2-5wt ℅ of nano-particles via polymerization

exhibits dramatic improvements in thermo-mechanical properties, barrier

properties and flame retardency.