More on Products from CNSL

Distillation of CNSL under reduced pressure gives cardanol. The residue will be rich in cardol and is generally known as residol, which is conveniently used in the preparation of friction dust for brake linings, ana aiso in ruDoer compounding formulations.

Friction Lining Materials

CNSL and cardanol based resins have found extensive uses in automotive brake lining applications as binders/friction dust. Although CNSL-Formaldehyde (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 ofPF 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

Modified CNSL Resin

Modified CNSL Resin can substitute PF totally and meet all the specifications of brake linings. Additionally, it improves impact properties, reduces fade. Cashew modified phenolics and CNSL-furfural reaction products, although expensive, give superior properties to that of straight cashew binder.

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/ paraformaldehyde 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.

CNSL resins give excellent lacquers with superfine surface finish and gloss. The dried film of this lacquer is superior to ordinary oil paints in resistance against vegetable and mineral oils, grease, moisture and chemicals. CNSL resins based varnishes possess good insulating properties apart from its high water repellence and low dielectric properties. Although CNSL and its resins are highly susceptible to fire and burn easily, they can be successfully made fire resistant by incorporating flame retardant elements chemically or flame retardant fillers physically. Chlorinated CNSL pigmented with sodium silicate, red mud titanium dioxide, mica powder or similar materials is known to be prepared and used by industries as flame retardant varnish. This flame retardant has to be blended with the surface coating for optimum performance and a self-extinguishable coating will be obtained.

CNSL resins alone or in combination with other resins show excellent water and weather proofing and can be used for protection of roofs. An anti-corrosive primer developed from CNSL shows excellent properties for application as protective coating for ships' bottoms. The coating withstand alkalinity normally encountered with cathodically protected steel hulls. Rust inhibiting zinc rich primers can be prepared from CNSL. Coatings giving tough elastic films are reported from CNSL-glycerine reaction products. A coating based on residol is used to protect the interior of ferro-concrete domes used for the collection of gobar gas.

Foundry Core Oil and Other Chemicals

Application of CNSL as foundry core oil shows its versatility CNSL resins are known to impart good scratch hardness to sand cores after baking them. It also provides resistance to moisture and weathering, good green strength and surface finish to moulded articles. It particularly replaces linseed oil in this respect. Modified CNSL Resin when used as core binder was found to improve collapsibility of the core and enhances bench life and anti-damp behaviour in comparison to conventional core binders.

Laminating Resin

To reduce brittleness and to improve flexibility of the laminates, CNSL or cardanol derivatives are extensively used in the laminating industry Resins of this type are produced by the co-condensation of phenol, CNSL and formaldehyde. The resins also exhibit improved age hardening and better bonding to the substrate. The lamination industry uses 900-1000 tonnes of CNSL for production of cardanol and for the manufacture of laminating resins. A typical formulation for resin production for particle board contain CNSL resin 90, xylene-10, 40% formaldehyde -35-85, sodium hydroxide-2, and water-10.

Rubber Compounding Resins

The rapid growth of rubber industry has accelerated demand for new ingredients which are used in the compounding of rubber for vulcanisation. Incorporation of CNSL products in rubber improves tensile strength and abrasion resistance, reduces fatigue, enhances self adhesion and rubber to cord adhesion and contributes to antioxidant and antiozonant activity. The fast curing cashew modified phenol-formaldehyde resins enhance the resistance of the product to ageing, chemical attack and the action of solvents and acids. The residol mentioned earlier is said to have properties much superior to that of pine tar, which thus gets replaced in rubber formulations.

Cashew Cements

Polymer based cements are now widely used because they give good adhesion and are unaffected by moisture, acids and alkalis. The phosphorus modified CNSL resin is most suitable for this purpose. This material adheres well to porous bricks, steel and concrete and could be set by gentle heat or by addition of curing agents. Thus, Anorin-38 bonds bricks much more efficiently and is resistant to acids and alkalis so that it could be used to cement floors which are subject to chemical attack. One of the most useful applications will be to seal leaks in the concrete roofs. This material can be admixed with a curing agent and made in the form of a putty which can be introduced to the cavities of the leaks by mild heating when it sets to a solid to fill the cavities.

Epoxy Resins

Epoxy resins offer properties much superior to those of polyester and phenolics. A subsidiary of 3M company USA is known to market a high impact adhesive by name 'Cardolite5' made from cardanol. It is reported that the epoxy polymer is made by acid catalysed electrophilic reaction of phenol with cardanol to get a'biphenol which is then epoxidised. The presence of the side chain assures improved flexibility and impact resistance over that of the conventional epoxies available in the market.

Wood Composites and CNSL based Adhesives

Speciality wood products have been made and marketed, by in-situ polymerisation of certain monomers after suitably incorporating them in wood. As cardanol as such fails to get polymerised by the conventional free radical or high energy irradiation methods, it requires special methods). CNSL based adhesives, however, are reported to exhibit admirable properties to meet the growing demand for quality and durability in bonding plywood. Various cashew-aldehyde resins when impregnated in low grade woods such as rubber wood show remarkable upgrading of quality These resins are equally applicable to the preparation of particle boards, bamboo boards, coconut leaf based boards etc. where both quality and cost effectiveness could be simultaneously achieved. Anorin-38 with a bonding capacity 500 times more than that of CF resins and with capabilities to reduce the flammability of the material stands a good chance for plywood and particle boards, particularly as there is a price advantage two to three times lower than the conventional phenolics adhesives.

Surfactants

CNSL can be advantageously used in the manufacture of anionic and non-ionic surface active agents. Like long chain fatty acids, cardanol possesses a typical lipid structure with a hydrocarbon hydrophobic group and a hydrophilic phenolic end group. This structure could be modified suitably to incorporate improved ion exchange capabilities such as introduction of a sulphonic acid group on the phenolic ring. The ion exchange resins are said to be good emulsifiers for oil-in-water and water-in-oil systems.

Industrial Chemicals and Intermediates for Chemical Industry

CNSL forms the basic raw material for a vast number of industrially important chemicals and chemical intermediates. Patents and reports cite a number of applications such as antioxidants, bacericides, fungicides, disinfectants, insecticides, dispersing and emulsifying agents, dye stuffs etc. Hydrogenation of cardanol gives 3-pentadecylphenol which stands a good chance for industrial utilisation. Reports suggest its utiliation as a replacement for nonyl phenol and as a starting material forthe preparation of 6-tertiarybutyl-3-pentadecylphenol and 3-pentadecyl-phenyl-glycedyl-ether. It's copolymerised product with phenol and formalehyde has been processed into speciality coatings by the Japanese. Suitable chemical modiication can convert the material into plastiizers that can replace the costly petrochemial based plasticizers.