Cashewnut
shell liquid
Cashewnut
shell liquid is a by-product of the cashew industry. The nut has a
shell of about 1/8 inch thickness inside which is a soft honeycomb
structure containing a dark reddish brown viscous liquid. It is called
the cashewnut shell liquid, which is the pericarp fluid of the
cashewnut.
Cost
Effective Modern Materials
In
the search for the cost effective modern materials, CNSL and its
products have a significant role to play. Being renewable, it offers
much advantage over synthetics. Its versatility stems from its
innumerable applications in many areas. Recent research has shown that
the constituents of CNSL possess special structural features for
transformation into speciality chemicals and high value polymers. This
involves a value addition of many orders of magnitude and the chemical
transformation provides 100% chemically pure products. Thus, CNSL
offers vast scope and opportunities for the production of speciality
chemicals, high value products and polymers. |
 |
Advantages
of CNSL based Polymers |
 |
Improved
Flexibility and reduced brittleness. |
|
Solubility in
Organic Solvents. |
|
Improved
Processability. |
|
Low Fade
Characteristics for Friction. |
|
Resistance to
'Cold Wear'. |
|
Good Electrical
Resistance. |
|
Better Water
Repellence. |
|
Improved alkali
and acid resistance. |
|
Compatibility with
other polymers. |
|
Antimicrobial
Property. |
|
Termite and Insect
Resistance. |
|
Structural
Features for Transformation into High Performance Polymers. |
|
Polymerisation
Characteristics of CNSL |
| CNSL
can be polymerised by a variety of methods: |
|
Addition
Polymerisation through the side chain double bonds using cationic
initiators such as sulphuric acid, diethylsulphate etc.. |
|
Condensation
Polymerisation through the phenolic ring with aldehydic compounds. |
|
Polymerisation
after Chemical Modification to introduce speciality properties. |
|
Oxidative
Polymerisation. |
|
Various
Combinations of the above. |
|
Industrial
Significance of CNSL |
|
Low
Cost Phenol. |
|
Versatility
in Polymerisation and Chemical Modification. |
|
Possibilities
for Development of High Performance Polymers. |
|
Property
advantage over phenolics in certain applications such as impact
resistance, flexibility, faster heat dissipation etc. |
|
Reactivity |
| CNSL
undergoes all the conventional reactions of phenols. Cardanol differs
from phenol only in the C15 side chain. It undergoes the
well known formaldehyde condensation reaction of phenols that gives rise
to phenolic polymers. Moreover, it can be polymerised through the
unsaturation in the side chain although the bulky nature of the side
chain restricts the molecular weight attainable to oligomers. One of the
significant advantage of the cardanol is its amenability to chemical
modification to effect desirable structural changes so as to get
specific properties for making tailor-made polymers of high value. Thus,
structural changes could be effected at the hydroxyl group, on the
aromatic ring and on the side chain. |
Cardanol |
| Distillation
of CNSLunder reduced pressure gives cardanol. The residue will be rich
in cardanol and is generally known as residol, which is conveniently
used in the preparation of friction dust for brake linings, and also in
rubber compounding formulations. ( The process know-how for the
production of cardanol and conversion of residol into friction dust is
available with RRL, Thiruvanathapuram). |
ISI
Specification of the untreated CNSL IS : 840(1964) |
| Specific Gravity/30° C |
0.950 - 0.970 |
| Viscosity at 30° C cps,
Max. |
550.0 |
| Moisture % by weight, Max.
|
1.0 |
| Matter Insoluble in Toluene
% by weight, Max. |
1.08 |
| Loss in Weight on heating, %
by Weight, Max |
2.0 |
| Ash % by weight, Max.
|
1.0 |
| Iodine Value, Min |
1.0 |
 1.
Wij's method |
250 |
| 2.
Catalytic method |
375 |
| Polymerisation
Time |
| a) Time in minutes, Max. |
4 |
| b) Viscosity at 30° C,
cps, Min |
30 |
| c) Viscosity after acid
washing at 30° C cps, Min |
200 |
| Color
shall be not deeper than dark brown when viewed by transmitted
light. |
|
|
Specification
for Treated Cashewnut Shell Liquid |
The
cashewnut shell liquid as extracted has a strong vesicant dermatatic
action. Before this liquid is utilized for preparation of resins, it
requires treatment to get rid of metallic impurities as well as traces
of sulphur compounds. The liquid thus treated is known as " Treated
Cashewnut Shell Liquid ".
The specification of treated
cashewnut shell liquid is as follows: |
| Specific Gravity at 25°
C / 24° C |
0.955 - 0.975 |
| Viscosity at 25° C (
max.) |
800 cps |
| Lodine Value ( min. )
|
240.00 |
| Ash ( max ) |
1% |
| Moisture ( max. ) |
0.5% |
| Acid Value ( max. ) |
14 |
|
|
Specification
for Cold Pressure Cashewnut Shell Liquid |
| Cashewnut shell liquid
is also produced by the 'Cold Pressed' method in solvent extraction
plant. The specification of the liquid is as follows: |
| Specific Gravity at 26°
C |
0.9668 - 1.0131 |
| Refractive Index at 41.50°
C |
1.5158 |
| Saponification number |
106 - 119 |
| Iodine number |
270 - 296 |
| Acid number |
94 - 107 |
|
|
|
