title: Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly.
abstract: The highly flammable character of cellulose-rich fibers from wood limits their use in some advanced materials. To suppress the flammability and introduce flame-retardant properties to individual pulp fibers, we deposited nanometer thin films consisting of cationic chitosan (CH) and anionic poly(vinylphosphonic acid) (PVPA) on fibers using the layer-by-layer (LbL) technique. The buildup of the multilayer film was investigated in the presence and absence of salt (NaCl) using model cellulose surfaces and a quartz crystal microbalance technique. Fibers were then treated with the same strategy, and the treated fibers were used to prepare paper sheets. A horizontal flame test (HFT) and cone calorimetry were conducted to evaluate the combustion behavior of paper sheets as a function of the number of bilayers deposited on fibers. In HFT, paper made of fibers coated with 20 CH/PVPA bilayers (BL), self-extinguished the flame, while uncoated fibers were completely consumed. Scanning electron microscopy of charred paper after HFT revealed that a thin shell of the charred polymeric multilayer remained after the cellulose fibers had been completely oxidized. Cone calorimetry demonstrated that the phosphorus-containing thin films (20 BL is ∼25 nm) reduced the peak heat release rate by 49%. This study identifies a unique and highly effective way to impart flame-retardant characteristic to pulp fibers and the papers made from these fibers.
authors.affiliation: Fiber and Polymer Technology, KTH Royal Institute of Technology , Teknikringen 56, 100 44 Stockholm, Sweden.
authors.forename: Oruç
authors.initials: O
authors.lastname: Köklükaya
authors.affiliation: Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino , Alessandria Site Viale Teresa Michel 5, 15121, Alessandria, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Carosio
authors.affiliation: Department of Mechanical Engineering, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Jaime C
authors.initials: JC
authors.lastname: Grunlan
authors.affiliation: Fiber and Polymer Technology, KTH Royal Institute of Technology , Teknikringen 56, 100 44 Stockholm, Sweden.|Wallenberg Wood Science Center, KTH Royal Institute of Technology , SE-100 44 Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Wågberg
mesh_terms: D002151:Calorimetry; D002482:Cellulose / Q000737:chemistry; D048271:Chitosan / Q000737:chemistry*; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D063065:Organophosphonates / Q000737:chemistry*; D010209:Paper; D011145:Polyvinyls / Q000737:chemistry*; D058525:Quartz Crystal Microbalance Techniques; D014934:Wood / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D008567:Membranes, Artificial; D063065:Organophosphonates; D011145:Polyvinyls; C000602303:poly(vinylphosphonic acid); D002482:Cellulose; D048271:Chitosan
keywords: chitosan; flame-retardant; layer-by-layer assembly; poly(vinylphosphonic acid); thermal stability; wood fibers