Greening Biobased Polybenzoxazine Network: Three Benefits in One Go

Abstract

Eco-friendly initiators and environmentally safe flame-retardant (FR) adhesives are highly desired to empower sustainability in polymers. However, incorporating all of the properties simultaneously in a single step is challenging to achieve high-performance biomass sourced polymers. Herein, biobased benzoxazine monomers sourced from agro-waste phenol (cardanol, C) were synthesized using a facile solventless catalyst-free approach. Owing to their requirement of high ROP temperature (∼ 250 °C), prolonged polymerization cycle, issues of high flammability, and poor adhesive strength of the resultant polybenzoxazines limit their applications. To alleviate these issues, blends of naturally occurring phytic acid (PA) with the monomers resulted in fast polymerization kinetics (∼90% monomer conversion in 1 h) with the formation of hybrid polybenzoxazine networks at a mild temperature (∼100 °C). PA enacted as a green initiator and reactive halogen-free biobased FR and revealed favorable interactions across the polymer framework. Benefitting from the design, physical, ionic, and covalent cross-linking network of polymers with PA accounted for the extra-strong adhesive strength (71.1 kg/cm 2 , nearly 3.7 times higher than that of the pristine polybenzoxazine). Upon burning, the hybrid polybenzoxazines exhibited extremely low flammability, superior smoke suppression and formed intumescent char as supported by the limiting oxygen index, vertical burning, and cone calorimetry measurements. The present study indicated that the benign by design approach is a way forward to green thermosets offering excellent combination properties and potential applications in the future.

Facile and eco-friendly synthesis of hydrogen bonding-rich bio-based bisbenzoxazine resins with low surface free energy, strong adhesion strength and high thermal stability

“…The interactions between the adhesive and the substrate, as well as the wettability and viscosity of the adhesive, all affect the adhesive strength to a surface. 76 The lap shear test was performed to evaluate the adhesion strength of all the newly obtained bio-based polybenzoxazines. Schematic diagrams of the sample size and lap shear test, as well as the test results, are shown in Fig.…”

Isolation of Cardanol Fractions from Cashew Nutshell Liquid (CNSL): A Sustainable Approach

“…Cashew nutshell liquid (CNSL), a reddish-brown viscous liquid (~25-30 wt.%), is derived from the most diffused roasted mechanical processes of cashew shells and is generally discarded as a pollutant from the cashew agro-industry [22]. Cardanol-based polymer offers specific properties, such as strong corrosion, heat and chemical resistance, and good adhesion properties, enabling their usage in many applications such as paints [23,24], surfactants [25], coatings [26][27][28], bio-plasticizers [29], larvicidal [30], antibacterials [31,32], adhesives [33][34][35], flame retardants [36,37], self-healing [38,39] cathode [40], and photovoltaic [41] materials, etc., for naval constructions, industrial machinery, and automotive components. Interestingly, even food, drug, and beverage industries also extensively use CNSL due to its antioxidant properties [42,43] and possible flavoring and mineral oil additive.…”

The Preparation of Electrolyte Hydrogels with the Water Solubilization of Polybenzoxazine

“…A green, high-performance PBZ resin from cardanol, an agro-waste phenol obtained from cashew nut shells, has been reported [27]. The research and development of green, high-performance PBZs from a sugar-based chemical, isosorbide [28], and cardanol [29] have been reported. In addition, an attempt to obtain PBZ from bio-based feedstock has been reported [30].…”