Revealing the flame retardancy mechanism of highly transparent cellulose nanopapers fabricated by vacuum filtration assisted layer-by-layer deposition

Suyeon Lee; Donggi Seong; Yangyul Ju; Hyo Won Kwak; Woo Sik Kim; Doojin Lee

doi:10.1016/j.carbpol.2020.116628

Revealing the flame retardancy mechanism of highly transparent cellulose nanopapers fabricated by vacuum filtration assisted layer-by-layer deposition

Carbohydr Polym. 2020 Oct 15:246:116628. doi: 10.1016/j.carbpol.2020.116628. Epub 2020 Jun 12.

Authors

Suyeon Lee¹, Donggi Seong¹, Yangyul Ju², Hyo Won Kwak³, Woo Sik Kim⁴, Doojin Lee⁵

Affiliations

¹ Department of Polymer Science and Engineering, Pusan National University, Busan 46241, South Korea.
² Department of Polymer Science and Engineering, Chonnam National University, Gwangju 61186, South Korea.
³ Department of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea.
⁴ Fibrous Ceramics and Aerospace Materials Center, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, South Korea. Electronic address: wskim@kicet.re.kr.
⁵ Department of Polymer Science and Engineering, Chonnam National University, Gwangju 61186, South Korea. Electronic address: dlee@chonnam.ac.kr.

PMID: 32747264
DOI: 10.1016/j.carbpol.2020.116628

Abstract

We fabricate transparent cellulose nanopapers with significantly enhanced flame retardancy by a vacuum filtration assisted layer-by-layer deposition method. Flame retardancy is enhanced by increasing the layer-by-layer thickness while not hampering optical transparency of the nanopapers. Thermal degradation and combustion behaviors show that the nanopapers have been successfully functionalized by phosphorus and amine compounds that act effectively as intumescent and blowing agents. Based on the heat release rate of the various nanopapers herein, we propose that the area of the second peak in the heat release rate can serve as an indicator for coating efficiency of these flame retardant materials. We also suggest a possible mechanism behind the material's flame retardancy where by the phosphorus and blowing materials promote intumescent carbonaceous and porous char layers that prevent diffusion of oxygen and heat penetration into the underlying cellulose nanopapers.

Keywords: Flame retardancy mechanism; Layer-by-layer deposition; Self-extinguishing; Transparent cellulose nanopapers.