Fire Properties of Novel Cellulosic Material Modified with Expandable Graphite

Abstract

Expandable graphite (EG) is an intumescent additive known to improve fire properties of various materials. Intumescent fire retardant (IFR) based on EG is a protection method for flammable materials taking the attention of researchers in the past few years (Xie et al., 2000). New studies indicate that EG is a good source of carbonization agent for effective and environmentally friendly intumescent systems (Feng et al. 2013). Although EG is used in a growing number of IFR systems as a blowing agent that will suppress flammable gases up to 75%, while reducing the flame spread index, its application to cellulosic material is not so popular in the cellulose industry today (Krassowski et al., 2012). The current study focuses on flammability, concerning cellulose modified material(CMM). The objective of this work was CMM encrusted with EG. The general aim of the research was to determine its basic fire resistance properties. The scope of the research included measurement of the following parameters: time to ignition (Ti), time to flame out (Tf), total heat peak (THR) and mass loss (ML). Samples of CMM sheets were manufactured with the use of hydropulper and rapid-koethen devices. Two types of EG (i.e. ES20 C200 and ES100 C10) were used. Sodra Black Cellulose fibres (700 kg/N3) was used in this experiment. Cellulose milling time was 30 min. and drying time of 40 min. The drying temperature of the final sheets was controlled and kept at 930C to avoid graphite activation. Final sheets were conditioned at room temperature at 200C and relative humidity 60%. With heat flux of 35 kW/m2 , all samples were tested on MLC apparatus. The addition of EG was found to increase the flame retardant effectiveness of cellulosic material. Although Ti for all CMM species were lower than that of control samples, this fact actually favored the promotion of char forming, which led to a longer combustion process for all CMM.

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