Cashew Nut Shell Liquid (CNSL) Based Bio-Derived Resin And Composites for Advanced Structural, Automotive, Electronic Packaging and Medical applications- A Review.
As India is a world class producer of sugarcane, sugar beet, other tubers like potato and vegetables with starch, cashew and badam, castor oil and soybean, the quantum of bio resins and bio plastics that can be produced from these conventional, organic and genetically modified plants is immense. As on date, advanced and state of the art plastics and composites are being used in many applications as there is no incentive for farmers to produce plants and vegetables for the plastics and resins market exclusively. The use of advanced composites in varied applications escalates costs and shifts the material consumption that would deplete the natural resources, through excessive usage at one end and lack of demand for natural resources at the other end as bio derived composites become under-utilized. This review paper attempts to project the actual possibilities of the bio resin and bio plastic market in this country and provides the knowhow for the production of bio-phenolic cashew nut shell resin which are more than a substitute for the synthetically produced epoxies. Their true potentialities in composites product applications involving structural, thermal, electronic, pharmaceutical and petroleum engineering markets is discussed in this paper. A novel working model with an economically feasible option is also provided for those concerned about their safe disposal, recycling, reuse and conversion into useable fuel with virtually no impact to the environment. Cashew Nut Shell Liquid (CNSL) is an abundant natural source for synthesizing phenolic compounds. The excellent monomer, Cardanol is isolated from CNSL for polymer production. These are polymerized with aldehydes and acids at a particular mole fraction in the presence of catalysts like alkalis to convert into rigid resins. Differential Scanning Calorimetric (DSC) and Thermo Gravimetric Analysis (TGA) were studied for the thermal characterization of the synthesized CNSL Resins. Characterization of the synthesized resins was also carried out with respect to the evaluated mechanical properties such as hardness, strength, elastic modulus and fracture toughness. The synthesized CNSL resins yielded many interesting compositions with varied properties increasing the possibilities of various resin formulations which could be used for composites applications in vibrational damping. The electronic packaging applications of nano-composites with high dielectric strength produced with the CNSL matrix are also highlighted.