Cardanol resins

An epoxy resin-based on epichlorohydrin, bisphenol-A and cardanol was evaluated as a binder for a paint system and was found to offer better properties in terms of increase in tensile strength, elongation, bonding with steel and lowering of water vapour transmission than epoxy resin. In addition, iron oxide-based paints in epoxy-cardanol resin showed better performance than zinc phosphate-based paints." " ... 

L. K. Aggarwal, P. C. Thapliyal and S. R. Karade, Anticorrosive properties of the epoxy-cardanol resin based paints . Prog Org Coat, 2007,59,76-80. 

A paint based on an epoxy-cardanol resin has been produced and then characterized in order to compare its performance (i.e. physico-mechanical properties, chemical resistance and corrosion protection efficiency) with that of paints made with unmodified epoxy resin (Aggarwal et al., 2007). It was found that the new bio-based paints show better anticorrosive properties than the unmodified paints and thus the cardanol-based epoxy resin represents an optimal binder medium for the formulation of paints. 

Synthetic resins, such as phenoHc and cresyUc resins (see Phenolic resins), are the most commonly used friction material binders, and are usually modified with drying oils, elastomer, cardanol [37330-39-5] an epoxy, phosphoms- or boron-based compounds, or even combinations of two. They ate prepared by the addition of the appropriate phenol and formaldehyde [50-00-0] in the presence of an acidic or basic catalyst. Polymerization takes place at elevated temperatures. Other resin systems are based on elastomers (see Elastomers, synthetic), drying oils, or combinations of the above or other polymers. 

The cationic polymerization of cardanol under acidic conditions has been referred to earlier [170,171], NMR studies [16] indicated a carbonium ion initiated mechanism for oligomerization. PCP was found to be highly reactive with aldehydes, amines, and isocyates. Highly insoluble and infusible thermoset products could be obtained. Hexamine-cured PCP showed much superior thermal stability (Fig. 12) at temperatures above 500°C to that of the unmodified cardanol-formaldehyde resins. However, it was definitely inferior to phenolic resins at all temperatures. The difference in thermal stability between phenolic and PCP resins could be understood from the presence of the libile hydrocarbon segment in PCP. 

CF = cardanol-formaldehyde resin (cured) MCPAF = monocar-danyl phosphoric acid-formaldehyde resin (cured) BrCF = bromo derivative of CF BrMCPAF = bromoderivative of MCPAF PF = phenol-formaldehyde (cured) MPPAF = monophenyl phosphoric acid-formaldehyde (cured), BrPF = bromo derivative of PF BrMPPAF = bromoderivative of MPPAF PPF = phenol-formaldehyde resin phosphorylated (cured). 

The lower thermal stability of cardanol-formaldehyde resin and their derivatives were expected because of the presence of the libile side chain in the system. Although phenolics are superior in their properties, their bromo derivatives exhibit very low char yields. Oxidation of the char by a decomposition product is suspected. Evaluation of the LOI data with char yields individually for phosphorus and bromine suggests a positive interac-... 

Interpenetrating network polymer. In a separate study, it was shown that cardanol-formaldehyde resins foiTn semi-interpenetrating networks with polymethylmethacrylate (PMMA). Although interpenetration of CF... 

Substituted phenols such as cresols, p-fcrf-butylphenol, / -phcnylphenol, resorcinol, and cardanol (derived from cashew nut shells) have also been used as precursors for phenolic resins. Alkylphenols with at least three carbons in the substituent lead to more hydrophobic phenolic resins that are compatible with many oils, natural resins, and rubbers.7 Such alkylphenolic resins are used as modifying and crosslinking agents for oil varnishes, as coatings and printing inks, and as antioxidants and stabilizers. Bisphenol-A (2,2-p-hydroxyphenylpropane),... 

Novolac resins containing cardanol moieties have also been converted to cyanate ester resins.107 The thermal stability and char yields, however, were reduced when cardanol was incorporated into the networks. 

Cardanol, a main component obtained by thermal treatment of cashew nut shell liquid (CNSL), is a phenol derivative having mainly the meta substituent of a C15 unsaturated hydrocarbon chain with one to three double bonds as the major. Since CNSL is nearly one-third of the total nut weight, a great amount of CNSL is obtained as byproducts from mechanical processes for the edible use of the cashew kernel. Only a small part of cardanol obtained in the production of cashew kernel is used in industrial fields, though it has various potential industrial utilizations such as resins, friction-lining materials, and surface coatings. Therefore, development of new applications for cardanol is very attractive. 

Many efforts have been made to base polymers on furfural made from pentoses.159 The polymers may be useful, but tend to have lower thermal stability than the usual synthetic polymers. Polyesters based on furfural were mentioned earlier. The acid-catalyzed polymerization of furfuryl alcohol is used in foundry cores.160 Furfural has been condensed with cardanol (m-pentadecadienylphenol) from cashew nut shell oil in the presence of other phenols to produce polymeric resins.161 Cardanol and hydrogenated cardanol have been polymerized with horseradish peroxidase to soluble polymers in up to 85% yield.162 Plasticizers that are effective in polyvinyl chloride, such as (12.31), have been made from furfural.163... 

By reaction of phosphorylated materials with aldehydes, amines or with isocyanates highly thermally stable products have been then produced. TGA studies have indicated their superior properties compared to conventional cardanol/formaldehyde resins of the novolac type. It was also found that a phosphorylated CNSL polymer had improved adhesive properties when compared with conventional CNSUformaldehyde resins (ref.248) and certain compounded products had wear, fade and frictional properties comparable to those of conventional PhOH/formaldehyde/copolymer brake Hnings (ref.249). The phosphorylated product from CNSL and its bromination derivative possessed good fire-retardant characteristics (ref. 250). Phosphorus derivatives of cardanol and of 3-pentadecylphenol have been studied by reaction with phosphorus oxychloride and its thio analogue (ref. 251). 

The resins in the friction dust area tend to be rigid and the flexibility and plasticity associated with the long alkyl chain of phenolic lipids have been used in natural rubber vulcanisation by for example incorporating crosslinking with phosphorylated cardanol (ref. 252). Unpolymerised CNSL phenols have been used in natural or diene rubber compositions for tyre treads to give an improved dynamic elastic modulus but with the same hardness as formulations without the phenolic addition (ref. 253). 

The method was extended to novolak and resol cardanol/formaldehyde copolymers. HO-protected phenolic lipids have also been reacted. Thus, cardanol methyl ether and esters have been hydrosilated with HSiClj and then reacted with methanol to afford methoxysilyl products useful as coupling agents for phenolic resins in sand cores (ref. 256). 

Rashes have been reported in persons coming in contact with the resin, wood, and, less frequently, the fruit of Brazilian peppertree (Morton 1978). An irritant compound, cardanol, was identified in Brazilian peppertree fruit (Stahl et al. 1983). 

A particularly promising route is to treat the fiber with a phenolic resin based on cardanol formaldehyde (CF). This is a natural alkyl-phenol, in which the methylol groups are able to react with the hydroxyl groups of the cellulose, while the long C-15 alkyl group of cardanol facilitates the formation of an adhesive bond with non-polar TPs. It is concluded that Jute fiber thermoplastic RPs can bear comparison with glass fiber RPs. However, the best solution may well be a combination of treated jute with glass. 

Epoxy resin-based epichlorohydrin,bisphenol-A and cardanol was evaluated as a paint binder and found to show increased tensile strength, elongation, adhesive strength with steel and low water vapour transmission when compared to epoxy resin without cardanol. ... 

Cardanol, a component of the agricultural by-product cashew nut shell liquid, also has a phenolic nature and can react with aldehydes under several conditions (Raqueza et al, 2010). Phenolic-type resins based on cardanol have been investigated for such applications as civil engineering structures (Cardona et al, 2010). 

Cardanol has also been used in benzoxazine-type resins prepared from cardanol-based monobenzoxazine monomer, which in turn was produced by the reaction of cardanol with ammonia and formaldehyde (Calo et al., 2007), or from a monofunctional benzoxazine monomer synthesized by the condensation of aniline and formaldehyde with cardanol (Rao and Palanisamy, 2011). 

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