期刊
JOURNAL OF HAZARDOUS MATERIALS
卷 403, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.jhazmat.2020.123957
关键词
BPA; Polycarbonate; Polyureas; Waste plastic valorization; Circular economy
资金
- Universita degli Studi di Bari Aldo Moro (Fondi di Ateneo)
This study presents a novel approach to valorize potentially hazardous PC wastes by regenerating BPA monomers and repurposing waste PC into PUs through a non-isocyanate route. The PUs obtained showed thermally stability and high processing suitability, making them promising materials for various applications.
The present study describes an unprecedented approach to valorize potentially hazardous poly-(bisphenol A carbonate) (PC) wastes. In THF, under non-severe conditions (120 degrees C), the reaction of PC with long-chain di amines H2NRNH2 (2 equivalents) provided a tool to regenerate the monomer bisphenol A (BPA; 83-95%, isolated) and repurpose waste PC into [-NHRNHCO-](n) polyureas (PUs; 78-99%, isolated) through a non-isocyanate route. Basic diamines (1,6-diaminohexane, 4,7,10-trioxa-1,13-tridecanediamine, meta-xylylenediamine, paraxylylenediamine) reacted with PC without any auxiliary catalyst; less reactive aromatic diamines (4,4'-diaminodiphenylmethane, 2,4-diaminotoluene) required the assistance of a base catalyst (1,8-diazabicyclo[5.4.0] undec-7-ene, NaOH). The formation of [-NHRNHCO-](n) goes through a carbamation step affording BPA and carbamate intermediates H[-OArOC(O)NHRNHC(O)-](n)OArOH (Ar=4,4'-C6H4C(Me)(2)C6H4-) that, in a subsequent step, convert into [-NHRNHCO-]n and more BPA. All the PUs were characterized in the solid state by CP/MAS C-13 NMR (delta(C=O) = 152-161 ppm) and IR spectroscopy. The positions of nu(N-H) and nu(C--O) absorptions are typical of hydrogen-bonded ordered bands suggesting the presence of H-bonded groups in network structures characterized by some degree of order or regularity. DSC and TGA analyses showed that the PUs are thermally stable (T-d,T-5%: 212-270 degrees C) and suitable for being processed since their degradation begins at temperatures about 100 degrees C higher than their T-g or T-m.
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