Cashewnut Shell Liquid
Cashewnut Shell Liquid

Cashewnut Shell Liquid

Cashew nut Shell Liquid is a by-product of the cashew industry. The nut has a shell of about 0.1 inch thickness inside which is a soft honeycomb structure containing a dark reddish brown viscous liquid. It is called the cashew nut shell liquid, which is the pericarp fluid of the cashewnut.

Cost Effective Modern Materials
In the search for 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.

Specification of CNSL

Colour : Dark Reddish brown Liquid
Viscosity at 30°C : 110 – 120 cps (Brook Field)
Specific Gravity : 0.95 – 0.955
Moisture : <1%
Ash Content : <2%
Matter insoluble in toluene : <1%
Iodine Value : Minimum 280(By Wig’s Method)
pH : 8 – 10
Polymerization Time at 176’c : < 4 minutes (Test Tube Gel Method di-ethyl sulphate + sulphuric acid)

Friction Lining Materials
CNSL and cardanol based resins have found extensive uses in automotive brake lining applications as binders/friction dust. Although CNSL-Formaldehyde Specifications of CNSL(CF) resins alone wouldn't meet the required mechanical properties, it improves impact properties and reduces fade considerably by dissipating heat faster than phenol-formaldehyde (PF) resins. Moreover, it imparts better water repellence, which is required in wet condition? CF resins give rise to a softer material, which is more efficient in 'cold wear'. Above all, the cost of CF resins is always lower by factor of 3 or more than that of PF resins. Addition of friction dust gives a silent braking action, which is highly desirable in modern times. About 12,000 -15,000 tonnes of brake linings are produced for use in motor cars every year in the country with the increasing use of automobiles, there is large scope for increase in demand for brake linings.

In brake lining materials, two types of CNSL products are used:
• CNSL resin as matrix resin as a partial substitute for phenolic resin to reduce cost
• CNSL based friction material (friction dust) to modify the friction and wear properties of brake linings
Property Advantages of CNSL Resins in Brake Linings over Phenolics
• Faster Heat Dissipation
• Lower Fade
• Better 'Cold Wear'
• Improved moisture resistance

CNSL based Friction Dust
Friction dust is added to brake linings to modify the frictional and wear properties of brake linings. It also provides similar properties as that of CNSL matrix resin. Formulations for improved skid resistance and low brake noise have been reported. The friction dust is generally prepared by cross-linking CF resin with hexamine/ par formaldehyde and powdering the product to the required specifications. Modified friction dust for applications in 'hot wear' conditions can be prepared from Modified CNSL Resin or from borated CNSL resin. Borated friction dust is known to be especially used in the production on air brake pads. Additionally, they wouldn't catch fire during transportation as is reported to have happened in the case of CF based friction dust.

Surface Coatings
CNSL based surface coatings possess excellent gloss and surface finish with optimum levels of toughness and elasticity It is widely known that CNSL resin is added to synthetics by paint/varnish manufacturers to control properties and to reduce cost. Its anti-termite and anti- microbial properties are well known from very ancient times as its use in protecting bottom of the boat hulls speaks out. Because of its dark colour, its outlets are restricted to anticorrosion primers, black enamels, marine paints etc. Recently, the Regional Research Laboratory, Thiruvananthapuram, has developed a transparent resin from CNSL that can be used as a base for paints of all colours.

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.