Abstract
In this work, several bio-based main-chain type benzoxazine oligomers (MCBO) were synthesized from eugenol derivatives via polycondensation reaction with paraformaldehyde and different diamine. Afterwards, their chemical structures were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance Spectroscopy (1H-NMR). The curing reaction was monitored by Differential Scanning Calorimetry (DSC) and FT-IR. The polybenzoxazine films were prepared via thermal ring-opening reaction of benzoxazine groups without solvent, and their thermodynamic properties, thermal stability, and coating properties were investigated in detail. Results indicated that the cured films exhibited good thermal stability and mechanical properties, showing 10% thermal weight loss (Td10%) temperature as high as 408 °C and modulus at a room temperature of 2100 MPa as well as the glass transition temperature of 123 °C. In addition, the related coatings exhibited high hardness, excellent adhesion, good flexibility, low moisture absorption, and outstanding solvent resistance.
Highlights
Polybenzoxazines play an indispensable role in the thermosets market
The objective of this work is to develop bio-based benzoxazine precursors with good processability and film-forming properties at room temperature, to prepare high performance organic coatings derived from eugenol
The following were all purchased from Aladdin Reagent (Shanghai, China): 1,1,3,3-tetramethyl disiloxane (99%), chloroplatinic acid hexahydrate (99%), toluene (99%), petroleum ether (99%), and isopropyl alcohol (99.5%)
Summary
Polybenzoxazines play an indispensable role in the thermosets market. They are widely applied in the areas of coatings, adhesives, microelectronics, and aerospace due to their exceedingly good properties, such as excellent chemical resistance, good thermal stability, minimal water absorption, nearly zero shrinkage, and good electronic properties [1,2,3,4,5,6]. A variety of bio-based benzoxazines have been prepared from renewable phenolic resources, such as arbutin [10], cardanol [11,12], cellulose derivative (diphenolic acid) [13,14,15], and lignin derivatives (vanillin, guaiacol, eugenol) [16,17,18,19,20,21,22].
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