Abstract
The preparation and thermal characteristics of new polyesters from cardol, a renewable monomer obtained as a by-product of the cashew industry, are reported. Cardol - a diol component of the natural product cashew nut shell liquid (CNSL) was isolated and reacted with adipoyl chloride and terephthaloyl chloride in a 1:1 molar ratio in hexane and toluene as solvents at 170 °C under nitrogen atmosphere. The cardol based polyesters [poly(cardyl adipate) and poly(cardyl terephthalate)] were produced in good yields of up to 63 and 54%, respectively. The polymers were analysed by FT-IR for functional groups elucidation and by combined thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for thermal stability. The cardol-based polyesters were thermally stable up to about 400 °C. The thermal stability of poly(cardyl terephthalate) was higher than that of poly(cardyl adipate) under similar conditions. All prepared polyesters were insoluble in common laboratory solvents at room temperature. KEY WORDS : Cashew nut shell liquid, Cardol, Polyesters, Renewable polymers Bull. Chem. Soc. Ethiop. 2016 , 30(2), 273-282. DOI: http://dx.doi.org/10.4314/bcse.v30i2.11
Highlights
Polymers dominate the chemical industry, making up around 80% of its output [1]
The delay in weight loss at higher temperatures observed during thermal treatment of the cardol-based polyesters in inert atmosphere could be attributed to the fact that in air, the measured weight losses are associated with both the decomposition and release of volatile components and combustion of solid by-products of pyrolysis whereas in inert atmosphere the combustion of solid by-products is suppressed
Sample masses used in the differential scanning calorimetry (DSC) ranged from 11.4-14.3 mg and the DSC traces for cardol-based polyesters in air and their derivative curves are shown in Figures 4b and 5b
Summary
Polymers dominate the chemical industry, making up around 80% of its output [1]. Globally, the annual polymer production is approximated at 250 million tonnes [2]. The components of solvent-extracted CNSL include anacardic acid (60-65%), cardol (15-20%), cardanol (10%) and traces of methyl cardol (Figure 1). Thermal extraction of CNSL causes polymer formation and decarboxylation of anacardic acid to cardanol.
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