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Wood-Plastic Composites preservation against fire: Nanofillers as fire retardant alternative
2018 - IRG/WP 18-40843
The purpose of this study is to improve fire resistance of Wood-Plastic Composites (WPCs) by adding inorganic nanofillers. Indeed, the main components of WPC, namely wood and polymer are both flammable materials despite the fact that WPCs are used in the field of construction. The effect of nanofillers on fire retardancy of Wood-High density polyethylene Composites was studied with three nanofillers, an organically modified nanoclay and fumed nanosilica and nanoalumina with percentages of 1%, 3% and 5% respectively. Samples had been prepared by twin-screw extrusion with percentages of 20%, 30% and 40% of Aspen fibers. The thermal stability was evaluated from thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC), while the flammability behavior was tested using cone calorimetry. It was found that the nanocomposites showed better thermal stability than non-filled WPC. Measurements from the Cone calorimetry test (Heat Release Rate, Total Heat Release, Carbon monoxide and Carbon dioxide) makes it possible to observe trends in fire behavior. Fire resistance improves with the increasing percentage of nanofillers. The nanoclay exhibits the lowest values of Peak Heat Release Rate (PHRR), Flashover Propensity Index (FPI) and Mass Loss Rate (MLR) as well as the highest ignition time (TTI). It is therefore considered to be the most efficient nanoparticle for fire retardancy. The char yield based on TGA analyses correlated with the PHRR in cone calorimetry tests and a high correlation coefficient between the char yield and PHRR (R2 = 0.909) was found. Furthermore, the char yield correlated with melting enthalpy based on DSC measurements and a high correlation coefficient R2 = 0.9229 was obtained.
D Ben Ammar, A Koubaa, S Migneault, H Bouafif


Green approach in wood mineralization for improvement of fire properties
2022 - IRG/WP 22-30769
Various treatments have been developed in order to improve fire properties of wood. Because the use of some flame retardants can release toxic compounds in the event of a fire, leading to poisoning or even death of people from smoke inhalation, the use of no-toxic and more ecologically acceptable flame retardants is preferable. Mineralization of wood with the incorporation of carbonates has proven to be a promising method for improving fire properties. The paper presents fire properties of two wood species (spruce and beech) modified using recently proposed eco-friendly mineralization process. Method is based on vacuum pressure impregnation using water solution of calcium acetoacetate which transforms to CaCO3 deep inside the wood structure. The parameters for determining the classification of reaction to fire were investigated. The increase in time ignition, decrease in the total heat release and the fire growth rate index were observed for mineralized wood. Moreover, reduced weight loss in different pyrolysis process of mineralized wood determined by thermogravimetric analysis indicates improved fire performance of such material.
A Pondelak, R Repič, L Škrlep, N Knez, F Knez, A S Škapin


Protection mechanisms of modified wood against decay by white and brown rot fungi
2010 - IRG/WP 10-10713
The resistance of beech and pine wood blocks treated with 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU) against T. versicolor and C. puteana increased with increasing WPG. Full protection (mass loss below 3%) was reached at WPGs of approximately 15% (beech) and 10% (pine). Metabolic activity of the fungi in the wood blocks was assessed as heat or energy production determined by isothermal micro-calorimetry. Fungal activity in the wood decreased with increasing WPG. Still, activity was detected even in wood blocks of highest WPG and showed that the treatment was not toxic to the fungi. The infiltration of untreated and DMDHEU-treated wood blocks with nutrients and thiamine prior to fungal incubation did not result in an increased mass loss caused by the fungi. This shows that the destruction or removal of nutrients and vitamins during the modification process has no influence on fungal decay. In order to study the effect of cell wall bulking and increased surface area, the cell wall integrity was partly destroyed by milling and the decay of the fine wood flour was compared to that of wood mini-blocks. The mass losses caused by the fungi, however, also decreased with increasing WPG and showed comparable patterns like in the case of mini-blocks.To study the effect of the chemical change of cell wall polymers, cellulose was treated with DMDHEU and the product was subjected to hydrolysis by a cellulase preparation. The release of sugar during the incubation was clearly reduced as compared to untreated cellulose. Pre-treatment of modified cellulose with Fenton’s reagent increased the amount of released sugar due to the cellulase activity. Pine micro-veneers were subjected to Fenton’s reagents in acetate buffer over 48h. While untreated specimens and veneers treated with low DMDHEU concentration displayed strong and steady tensile strength loss, veneers treated to a higher WPG did hardly show tensile strength loss.
C Mai, P Verma, Yanjun Xie, J Dyckmans, H Militz


Measurements of rot fungal activity as a function of moisture content by isothermal calorimetry
2010 - IRG/WP 10-20428
Measurements of heat production rate have been made on wood samples with the brown rot fungus Postia placenta at different moisture contents. The results clearly indicate that the heat production rate (a measure of respiration rate and activity) is moisture dependent. When the moisture content is decreased, less heat is produced, and when the moisture content is increased, more heat is produced. Isothermal calorimetry seems to be a measurement technique well suited to the study of rot fungal activity as a function of temperature and moisture content.
L Wadsö, A Pilgård, G Alfredsen


Effects of intumescent formulation of vinyl acetate-based coating on flame-retardancy of thin painted red lauan (Parashorea spp.) plywood
2011 - IRG/WP 10-40537
Using intumescent coatings on wood-based materials is an effective method for fire safety. The intumescent coatings consist of four major components: (1) binder resin (BR), (2) carbonizing substance (CS), (3) foam producing substance (FPS) and (4) dehydrating agent (DA). Previous studies have demonstrated that the formulation of the four components strongly influences the performance of coatings. This study investigated the effect of intumescent formulation of vinyl acetate-based coating on flame-retardancy of plywood. Two sorts of widely used binder resin (BR) for vinyl acetate-based coating, ethylene vinyl acetate copolymer (EVAc) and vinyl acetate acrylic copolymer (VAC), were used. The fire retardancy of coatings on plywood was assessed by a cone calorimeter. Total heat release and time to peak heat release rate are the two primary parameters. The data showed that lower BR and FPS content decreased total heat release and lengthen time to peak heat release rate. This mechanism to achieve better fire performance was verified by using oxygen bomb calorimeter and thermogravimetrical analysis, exhibiting lower heat of combustion and weight loss. The lower BR and FPS content can extend the survival duration of phosphor-carbonaceous chars. The results provide information for designing vinyl acetate-based coating.
Chih-Shen Chuang, Kuang-Chung Tsai, Te-Hsin Yang, Ming-Kuang Wang, Chun-Han Ko


Activities of moulds on wood as a function of relative humidity during desorption and absorption processes
2013 - IRG/WP 13-10794
Three different types of indoor moulds: Penicillium brevicompactum, primary colonizer; Alternaria tenuissima, secondary colonizer and Trichoderma harzianum, tertiary colonizer, grown on wood were measured for their activities under different relative humidity levels. The activities were measured by isothermal calorimetry. The activities of the moulds changed with the change of the relative humidity levels. The optimal relative humidity levels are different for these three moulds. The mould activities were also different from desorption to adsorption processes under the same relative humidity levels. This might be caused by the moisture hysteresis properties of wood. Therefore, besides of relative humidity, water availability also plays an important role for mould growth. Such information should be taken into account for modelling mould behaviour on building materials.
Yujing Li, L Wadsö


The activity of a wood-decaying fungus during drying and rewetting cycles measured by isothermal calorimetry
2013 - IRG/WP 13-20526
Wood decaying fungi are an essential part of any ecosystems as they are the main decomposers of cellulose and lignin-containing materials. But as wood is a common building material the risk for decay fungi growth and subsequent degradation of our construction material is a concern. There are important physiological aspects of the growth and activity of decay fungi that are unknown today, and without knowledge on these factors it is not possible to make physiological relevant models for decay fungi. Measurements of heat production rate have been made with isothermal calorimetry on wood samples with the brown rot fungus Postia placenta at different moisture contents. Isothermal calorimetry gives a direct measurement of an organism’s activity as it measures the heat produced when the organism respires and it is has shown to be a very suitable method to study fungal activity as a function of different parameters. The results clearly show the heat production rate (a measure of respiration rate and fungal activity) is moisture dependent. For most cases, less heat was produced when the moisture content was decreased, and more heat was produced when the moisture content was increased. It was also found that when the moisture content increased after a dry period, the increase in activity was significantly delayed. However, if the moisture state was then kept constant at a high level the activity slowly increased, showing that the fungi need time to recover back to the original activity level after drying. Isothermal calorimetry is a measurement technique well suited for the study of the activity of wood-decaying fungi as a function of temperature and moisture content.
S Johansson, L Wadsö, A Pilgård, G Alfredsen


Curing kinetics of nano cupric oxide (CuO) modified PF resin as wood adhesive: Effect of surfactant
2013 - IRG/WP 13-40620
The effect of nano cupric oxide (CuO) in combination with surfactants on the curing kinetics of phenol formaldehyde (PF) resin, as well as the bonding strength of plywood prepared using the modified resin were investigated in this study using dynamic and isothermal differential scanning calorimetry (DSC). The result showed that the incorporation of nano CuO along with alkane surfactant made in the laboratory clearly reduced the apparent activation energy of the PF resin and improved the addition and condensation reactions of the PF resin. Inclusion of the surfactant had the further effect of compensating the influence of diffusion control caused by nano CuO alone. The shear strength of plywood suggested that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosolfonate (0.55%) in the PF resin mixture was sufficient to meet the requirement of wood-based composites manufacturing.
Wei Gao, Guanben Du


Combustion and thermal characteristics of Korean wood species
2016 - IRG/WP 16-40727
This study examined the combustion and thermal characteristics of domestic woods in Korea. Wood was confirmed by a cone calorimeter according to the KS F ISO 5660-1 standard. The combustion properties of the wood were measured in terms of the heat release rate (HRR), total heat released (THR), mass lose rate (MLR), and ignition time (time to ignition; TTI). Also, the thermal properties were measured by thermogravimetric analysis (TGA) to determine the thermal stability of wood. The result of this experiment would be useful for fundamentals of guiding the combustion properties and thermal stability using wood application.
Huyun Jeong Seo, Jung-eun Park, Dong Won Son, Won-Joung Hwang


Selection of heat flux value for wood fire retardants testing using MLC
2018 - IRG/WP 18-40846
One of more crucial elements of investigating treated wood combustion properties with the use of a cone calorimeter is a proper selection of heat flux (HF). The HF level is directly reflected in time to ignition and a thermal degradation degree. The ignition of raw wood or of wood ineffectively protected against fire occurs at a low HF level, i.e. 10-20 kW/m2. By contrast, the ignition of wood which is effectively protected against fire, may occur no sooner than at HF 50 or even at 75 kW/m2. The aim of the paper was to analyse the problem of the selection of heat flux intensity in both experimental and standard fire testing with the use of a mass loss calorimeter (MLC). The subject of the analysis was wood treated with protective agents of various durability and fire resistance. On the one hand, the high HF value for wood samples of low fire resistance restricts or even excludes practical applications of an MLC as a tool for the evaluation of fire protection efficiency. On the other hand, too low value of HF prevents wood either from ignition or from determination of its thermal degradation degree. It especially applies to the situation when wood is effectively protected against fire. In both cases, the problem arises at the interpretation stage of obtained results. The identified problem was presented on the example of wood treated with chemical compounds which are ingredients of commonly used fire retardants, i.e. MAP – monoammonium phosphate, DAP – diammonium phosphate and PC – potassium carbonate, well known for their fire retardant properties. They are also known for their high solubility, which proves their high leaching from wood resulting consequently in a significant decrease in fire retardant properties. Unfortunately a versatile research procedure was not proposed in the performed study. However, the necessity for the individual selection of physical properties of a combustion process was emphasised. The above forces an unconventional method of result interpretation.
B Mazela, W Perdoch, W Grześkowiak, A Batista


The development of a suitable fire retardant for Radiata pine and other species
2019 - IRG/WP 19-30744
The use of fire retardant chemicals, with the overarching aim of creating a safer environment is not a new one, however it is generally under-developed and is often afflicted with an image of environmental and health issues and misperceived high costs. There is an ever-increasing need and desire for effective fire retardancy in timbers to inhibit or suppress the combustion process. This is paramount throughout the world, ever more so now with the effects of climate change driving the need for better protection of building timbers both in commercial and domestic use. Year on year, fires around the globe, on average are becoming larger and seemingly more destructive. These fires are affecting not only forest, bush and scrub land but populated areas too. Fire is unpredictable, destroying residences and taking lives. By slowing combustion, lives can be saved by giving people longer to evacuate. In this study we have investigated enhanced fire resistance properties for a number of timber species in relation to the heat release values (of various species of timber). Unlike many traditional fire retardants which are painted or sprayed onto the timber, this new innovative chemistry is applied by vacuum/pressure impregnation with a fire retardant based on phosphorus and nitrogen synergy. We have conducted a number of trials here in New Zealand and will continue to do so on Radiata pine (Pinus radiata), Western red cedar (Thuja plicata), American white oak (Quercus alba) and Silver beech (Nothofagus menziesii). Variability within material and species plays a key role in retention of the fire retardant and subsequent performance of these wood products when subjected to intense heat. The fire testing results from a research laboratory utilising the small-scale test method ISO 5660 – cone calorimeter test confirm the proven benefits of this fire retardant.
B R Derham, M R Fortune