Medium chain glycerides of coconut oil for microwave- enhanced conversion of polycarbonate into polyols Hynek Beneš ⇑ , Aleksandra Paruzel, Olga Trhlíková, Bartosz Paruzel Institute of Macromolecular Chemistry AS CR, v.v.i. Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic article info Article history: Received 25 October 2016 Received in revised form 24 November 2016 Accepted 28 November 2016 Available online 1 December 2016 Keywords: Medium chain triglycerides Coconut oil Polycarbonate Chemical recycling Renewable resource Microwave abstract In this paper, the medium chain glycerides of coconut oil were used as solvolysis reagents for microwave-enhanced conversion of polycarbonate into recycled polyols. First, triglyc- erides of coconut oil were transesterified with glycerol to monoglycerides bearing func- tional hydroxyl groups, which were able to react with carbonate linkages resulting in cleavage of polycarbonate chain. The important accelerating effect of microwave irradia- tion on kinetics of polycarbonate solvolysis was observed. The developed recycling process produced a mixture of low-molecular weight polyols applicable for synthesis of novel polyurethanes. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Polycarbonate (PC) waste might be as other thermoplastic wastes re-processed at elevated temperatures by means of physical (mechanical) recycling. However, the negative aspect of this relatively simple way how to re-use PC waste is con- nected with the unwanted degradation of PC during re-processing resulting from the presence of impurities and contami- nants. As the example, siloxane coatings from waste automotive headlamps negatively affected the mechanical properties of the reprocessed PC [1]. Contrary to that, methods of chemical recycling might lead even in certain amount of present impurities to recover raw materials, monomers applicable for manufacture of new polymer materials. A number of chemical recycling methods for PC waste have been mentioned in the literature. Alkali-catalyzed methanol- ysis of PC was firstly described by Yakubovich et al. [2]. Hu et al. studied the basic methanolysis of PC in toluene and dioxane [3]. The use of solvent led to significant decrease of reaction time (from 330 min to 70 min) and increase of yield 2,2-bis(4- hydroxyphenyl)propane, commonly called bisphenol A (BPA) up to 96%. Liu et al. also used the addition of organic solvents to accelerate the rate of basic methanolysis and hydrolysis of PC [4]. However, very high excess of solvent and high amount of catalyst (NaOH) had to be applied. The methanolysis of PC under mild conditions (105 °C) and in the presence of ionic liquid (1-n-butyl-3-methylimidazolium chloride) led to 95% BPA recovery and carbonate formation after 2.5 h of the reaction [5]. Non-catalyzed methanolysis and glycolysis of PC is described by Kim et al. [6,7]. The maximal yield of BPA was reached after 85 min of the reaction with ethylene glycol (EG) at 220 °C. However, the high excess of EG was applied; the used mass ratio of EG/PC was 4/1. Lin et al. reported the glycolysis process for PC waste in which the use of molar excess of urea and zinc oxide as the catalyst in the second stage of the process led to high yields of bishydroxyalkyl ethers of BPA [8]. The basic gly- http://dx.doi.org/10.1016/j.eurpolymj.2016.11.030 0014-3057/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: benesh@imc.cas.cz (H. Beneš). European Polymer Journal 86 (2017) 173–187 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj