Flame retardant eugenol-based thiol-ene polymer networks with high mechanical strength and transparency

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2019-07, Vol.368, p.359-368
• Main Authors: Liu, Tao, Sun, Lichao, Ou, Rongxian, Fan, Qi, Li, Liping, Guo, Chuigen, Liu, Zhenzhen, Wang, Qingwen
• Format: Article
• Language: English
• Subjects: Eugenol-based cyclophosphazene monomer; Flame retardancy; Mechanical strength; Thiol-ene photopolymerization; Transparency
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.02.200

[Display omitted] •A hexa-eugenol substituted phosphazene monomer (HEP) was synthesized and identified.•HEP-SH polymer networks are built by photo induced thiol-ene copolymerization between four multi-thiol monomers and HEP.•HEP-TEMPIC and HEP-PETMP networks exhibit outstanding intumescent flame retardancy.•HEP-TEMPIC and HEP-PETMP networks also possess high mechanical strength and transparency. Exploring renewable bio-based polymer materials with intrinsic flame retardancy and high mechanical strength will greatly increase the potential to meet fire safety and practicability requirements. In this study, a hexa-substituted cyclophosphazene monomer (HEP) is synthesized from abundant and renewable eugenol and then copolymerized with multi-thiol monomers to establish HEP-SH polymer networks by thiol-ene photopolymerization. Four HEP-SH polymer networks (HEP-TEGDT, HEP-TTMP, HEP-PETMP, HEP-TEMPIC) were prepared by varying the number of thiol groups or the backbone of thiol monomers. Among these polymer networks, HEP-PETMP and HEP-TEMPIC networks exhibit excellent flame retardancy (LOI > 27 vol.%, achieved UL 94 V-0 rating). The combustion parameters and flame retardant mechanism are further studied by cone calorimetry and combined scanning electron microscopy/energy-dispersive spectroscopy (SEM-EDS), which confirm the intumescent flame retardancy of HEP-SH networks is simultaneously affected by the contents of phosphorus and nitrogen element, as well as the structural features of the polymer network. In addition, the HEP-TEMPIC and HEP-PETMP networks also exhibit high mechanical strength and transparency. These eugenol-based thiol-ene polymer networks open a new pathway to develop sustainable high-performance flame retardant bio-based polymer materials for practical application.