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Nowadays, the chemical industry is looking for sustainable chemicals to synthesize nanocomposite bio-based polyurethane foams, PUs, with the aim to replace the conventional petrochemical precursors. Some possibilities to increase the environmental sustainability in the synthesis of nanocomposite PUs include the use of chemicals and additives derived from renewable sources (such as vegetable oils or biomass wastes), which comprise increasingly wider base raw materials. Generally, sustainable PUs exhibit chemico-physical, mechanical and functional properties, which are not comparable with those of PUs produced from petrochemical precursors. In order to enhance the performances, as well as the bio-based aspect, the addition in the polyurethane formulation of renewable or natural fillers can be considered. Among these, walnut shells and cellulose are very popular wood-based waste, and due to their chemical composition, carbohydrate, protein and/or fatty acid, can be used as reactive fillers in the synthesis of Pus. Diatomite, as a natural inorganic nanoporous filler, can also be evaluated to improve mechanical and thermal insulation properties of rigid PUs. In this respect, sustainable nanocomposite rigid PU foams are synthesized by using a cardanol-based Mannich polyol, MDI (Methylene diphenyl isocyanate) as an isocyanate source, catalysts and surfactant to regulate the polymerization and blowing reactions, H2O as a sustainable blowing agent and a suitable amount (5 wt%) of ultramilled walnut shell, cellulose and diatomite as filler. The eect of these fillers on the chemico-physical, morphological, mechanical and functional performances on PU foams has been analyzed.

Two different novolac resins, named Nov-I and Nov-II, containing an amount of unreacted cardanol of 35 wt % and 20 wt %, respectively, were synthesized by the condensation reaction of cardanol and paraformaldehyde using oxalic acid as catalyst. Cardanol is the main constituent of cashew nut shell liquid, a renewable natural resource. The cardanol-based novolacs were tested as curing agents of the diglycidyl ether of bisphenol A epoxy resin employing 2-ethyl-4-methyl-imidazole as catalyst and differential scanning calorimeter and thermogravimetric studies were performed to identify the final thermal properties of the cured resins. In addition, tensile tests were carried out to evaluate the mechanical properties of the epoxy resin cured with the novolacs, which showed to deserve consideration as effective epoxy curing agents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Publisher Summary Benzoxazine chemistry is well known and offers many advantages. Only recently polybenzoxazines with enhanced structural properties are successfully synthesized, alone or formulated with suitable additives. Benzoxazines offer many advantages compared with epoxies and other chemical structures, as they are halogen-free, exhibit better flame-resistance and electrical properties than epoxies, and are characterized by an excellent high temperature resistance and low water absorption values. With this combination of properties, benzoxazines hold great promise for performing in applications such as composites, coatings, adhesives, encapsulants, and others. It focuses on the synthesis of new low viscosity cardanol-based benzoxazines, as possible alternatives to the standard petroleum-based ones. This chapter describes that Cardanol is an industrial oily alkyl-phenolic product obtained by the vacuum distillation of “cashew nut shell liquid” (CNSL), a renewable natural resource obtained from the cashew nut as a byproduct during the process of removing the cashew kernel from the nut. A monofunctional liquid cardanol-based benzoxazine is prepared and used as a reactive diluent and toughening agent for a bisphenol A-based benzoxazine. The thermal, viscoelastic, and mechanical properties of benzoxazine resins obtained from the mixture of a low viscosity CA-a and the BA-a are studied in this chapter. Three different mixtures of BA-a and CA-a, containing 10%, 20%, and 30% by weight of CA-a, are prepared and studied to illustrate how different amounts of the cardanol derivative affect the properties of the final benzoxazine resins. The results obtained from the nonisothermal DSC analysis suggested a copolymerization reaction between the two benzoxazines BA-a and CA-a, occurring in a temperature range similar to that shown by the BA-a resin.

The aim of this work is the development of composite pipes using renewable resources. The pipes, manufactured by filament winding technology, were obtained using an epoxy resin crosslinked with a cardanol based novolac as matrix and jute fibres as reinforcement. Cardanol is a natural oil extracted from the shell of the cashew (Anacardium occidentale L.) nut. An amount of natural materials higher than 50% by weight was achieved in the final composites. Tensile and parallel plate compression tests were carried out on the composite pipes.

Benzoxazines are a class of phenolic compounds extensively studied in polymer science because of their properties as fiber reinforcements, fire-retardants and curing agents. In this article is described a solvent-less process, based on a Mannich reaction involving a primary amine and an aldehyde, for the preparation of new benzoxazines deriving from cardanol (a well known phenol obtained as a renewable organic resource and harmful by-product of the cashew industry). Particular attention is given to the synthesis and chemical characterization (both by 1H NMR spectroscopy and HPLC), while the thermal polymerization process has been monitored by differential scanning calorimetry.