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Effect of flue gas density on combustion of wood-based panel products

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  • Save International Journal of M aterials and Chemistry 2012, 2(5): 225-228 DOI: 10.5923/j.ijmc.20120205.07 Evaluation of Smoke Density on Combustion of Wood Based Panel Products K. Ch. Varada Rajulu*, Anand Nandanwar, M. C. Kiran Indian Plywood Industries Resarch and Training Institute IPIRTI, P. B. No 2273, Tumkur road, Bangalore Abstract Smo ke density of wood based panel materials like General purpose plywood, Marine Plywood(BWP g rade), Medium Density Fibre Board (M DF), Bamboo Mat Board (BM B), Pre-laminated Part icle Board (PPB) were measured using chamber method (ASTM D 2843-70). The specimens are tested inside closed chamber and readings of light transmission were taken at 5-seconds interval. Measurements were made in terms of loss of light transmittance through an accumulated volu me of s moke. It was observed that pre-laminated particle board and general purpose plywood with 22.20% &22.47% of smo ke accumu lation area respectively resulted lower values as compared to other panel products such as marine plywood (BWP grade), MDF, BM B etc. A uniform rate of s moke build-up was recorded. Th is study provides the basis for predicting the smoke production rate, time to ignite (TTI), and To xicity index which can be developed by combustion of the wood product. Keywords Smoke Density, Wood-Based Panels, Smoke Production Rate, Fire Tests 1. Introduction The smoke-limit ing requirements in current building codes have been established as an attempt to regulate and to reduce the potential light-obscuration hazard fro m smo ke generated by the interior building finish materials applied to walls, ceiling and floors in case of fire[1]. These requirements are co mmonly based on the results from tests devised principally for measuring co mparat ive surface flammability. Unfortunately the relationship between the results of such tests and the visual-obscuring qualities of smoke are not well established. The most common method for s moke suspension measurements today employs a light source and a photoelectric cell, so that the electrical output of the cell may be used as a measure of the attenuation of light by smoke[2,3]. In previous study, an attempt was made to relate the smo ke density rating for a variety of building materials with visual and photoelectric observations in a chamber which is computer interfaced[4-8]. The immediate objectives of the present study is to measure smoke density under prescribed chamber method as per ASTM D 2843[9], ASTM F814[10] and ASTM D 618 [11]in standardized exposure conditions and evaluate the appropriate optical properties of s moke which obstruct human vision in build ing fires, without regard to the chemical nature of the smoke or fundamental processes of its * Corresponding author: varadaraju6@gm (K. Ch. Varada Rajulu) Published online at Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved generation. The effects of the smoke produced by a fire depend on the amount of s moke produced and on the properties of the smoke. W ith respect to defining the hazard when a person is t rapped in a room where smoke is being generated or accumulated, three important aspects should be considered: 1. Maximu m smo ke accumu lated quantity from a given area of material under the prescribed exposure. 2. Maximu m s moke accu mulat ion rate represents how quickly the smoke level increased as averaged over a time period (2min). 3. Time to reach a prescribed s moke density represents the time period prior to attaining a critical smo ke level. Approaches have been made to predict effects of smoke in fires[12,13]. Smoke is generally considered to be the gaseous products of burning organic materials in which s mall solid and liquid particles are also dispersed. The major cause of the loss of life in a fire involv ing wood appears to be the generation of carbon mono xide through thermal break-down of cellulose, partial o xidation of carbon, nitrogen oxides, and hydrogen based chemicals. The rate of thermal degradation of wood depends upon the heat transfer through the wood, type of char formed and the rates of diffusion of the gaseous decomposition products and degradation of products during their passage through the char. This research article presents experimental results on smoke emission for a variety of wood based panel materials such as general purpose plywood, marine p lywood/BWP grade, MDF(med iu m density fib re board), BMB (bamboo mat board) and PPB(pre-laminated particle board)of 12mm thickness. Which are most commonly used in applications such as partitions, cupboards, furniture’s, etc. 226 K. Ch. Varada Rajulu et al.: Evaluation of Smoke Density on Combustion of Wood Based Panel Products Figure 1. Computer interfaced Smoke density equipment 2. Experimental Procedure The method of measuring smoke density using simple light transmission measurements has been developed by the Roh m and Haas Co mpany. In this method, test apparatus consists of a smoke chamber with a light source located on one side. The light beam traverses the 300mm path through the chamber and strikes a photoelectric cell located on the opposite wall. The specimen was burned inside the closed chamber, and light transmission was recorded at 5-seconds interval. These data were plotted against time, the smo ke production rate (slope of the curve) and the total smoke produced (area under the curve) was determined. The maximu m s moke density was also read fro m the curve. Samples of size 25x25x12mm different types of wood based panel materials were conditioned at 27±2O C and 65±5%relative humidity fo r unless constant mass was obtained. After conditioning the samples were tested at controlled environ ment of temperature 27± 2OC and 65±5% relative hu midity. The specimen were then placed on the supporting metal screen (wire mesh) and burned in test chamber as shown in fig.1.The flame was generated using a propane burner operated at pressure of 276kPa (40psi). The size of 300x300x790 mm test chamber is instrumented with a light source, d.c.voltage at 5mV, a photoelectric cell, 25mm h igh ventilation openings around the bottom and a meter to measure light absorption horizontally across the 300mm light beam path. The test specimen was exposed to flame for duration of 9min and the smoke generated was trapped in the chamber in wh ich co mbustion occurs. 3. Results and Discussion A dedicated calibration was performed using reference samples whose density was previously determined by measuring the volu me and mass by a balance with an accuracy of 0.001g. Sample of thickness is about 12 mm were taken for samp les viz. M DF, BM B, PPB etc. 4specimenswere taken for determining s moke density. Density and volume of d ifferent types of panel p roducts are given in table1. Table 1. Density and volume of wood panel materials Name of the Sample Den sity (g /cc) Volume (cm3) General purpose plywood Marine Plywood(BWP grade) MDF BMB PP B 0.763 0.755 0.759 0.849 0.826 9.355 7.965 8.103 9.556 8.631 The reduction of the light transmittance caused by smoke was converted to specific optical density using the relation: where, Ds= G log10(100%/T) T is the light transmission (%), Ds is maximu m smo ke density G is geometrical factor for the chamber (=132), the optical path length of the light beam and the exposed specimen surface area. International Journal of M aterials and Chemistry 2012, 2(5): 225-228 227 Measurements were made in terms of loss of light transmittance through a collected volume of s moke and effluent of a test specimen produced in a fixed volu me chamber under controlled standardised conditions. The burning conditions were simu lated by the smoke density chamber: rad iant heating in the absence of flaming in the presence of supporting radiations. Generally, wood based panels are hygroscopic in nature at high humidity p roducts absorb moisture and thereby increase in density and vice versa. Fro m table 1 it is observed that density of BMB is more than other wood composite materials. Fro m the results it is observed that the general purpose plywood has low smoke density, in comparison with other materials studied. The results of smo ke density of diffe rent panel products are given in table 2. One can observe from the table 2 that the major wood and BM B wh ich are used for exterior and interior applicat ions of building materials shows uniform rate of smoke build-up in the chamber. This is evidenced by almost similar t ime taken to achieve maximu m density (Ds) in all samples except MDF. This may be the fact that the MDF having fibres, which catches fire easily and start charring at early stage. Almost similar trend of Absorption % versus time curves was observed for all tested panel products as shown in fig.2. A linear increase (Except M DF) in smo ke generating p rocess was observed and approach to final reading, representing maximu m accumu lated smo ke. During and after a typical test smoke was disappears due to settling and coagulation, the rate being greater at higher concentrations. No adjustments were made to the measurements for these losses, since it may be supposed that a similar, though generally not identical process of smoke bu ild-up occurs in chamber or room of other size. It may be concluded from the above results that the pre-laminated part icle board as well as general plywood resulted lower values of the specific optical density of smoke generated. Table 2. Results of smoke area, maximum Smoke density and time Name of the Sample General purpose plywood Marine Plywood (BWP Grade) MDF BMB PP B Maximum smoke accumulation (area) % 22.42 36.57 30.36 24.29 22.20 Maximum smoke density(Ds) 40.59 62.81 55.03 47.15 47.11 Time (T), Min 5:15 5:45 2:45 5:00 5:45 Fi gure 2. Light absorpt ion in various samples with t ime 228 K. Ch. Varada Rajulu et al.: Evaluation of Smoke Density on Combustion of Wood Based Panel Products 4. Conclusions [4] Lee, Kin chung, “Fire-resistant coating compositions”, U.K. Pat Appl. G.B, 2088400, (1980). The results clearly presenting the reaction of smoke optical density properties of wood based products. Specific optical density provides the basis for predict ing the smo ke [5] Pearson, Geenn A., “Fire retardant composition”, U.S. Pat. 4,427,745, (1984). production rate, time to ignite (TTI), and To xicity index [6] Wittbecker F.W., “Smoke Detectors and Escape Times”, Fire which can be developed by the same product in the other fire Europe, 4, 5-8, (1997). involved areas in the other enclosure volumes. General [7] Bankston C.P., Cassanova R.A., Powell E.A.,Zinn B.T., purpose plywood has lowest smoke density (40.59) and “Initial Data on the Physical properties of Smoke Produced by marine plywood has highest smoke density (62.81) in comparison with other studied materials. Results were Burning M aterials under Different Conditions”, J.F.F., 7,165,(1976). presented which illustrate the variation in s moke production [8] Jin T., “Visibility through fire smoke” journal of fire and between materials. This new knowledge can be used to flammability, 9,135-155, (1978). estimate the smoke toxicity and conventional toxicity index for wood and wood based panel products. [9] “Standard Test M ethod for Density of Smoke from the Burning or Decomposition of Plastics”, ASTM D2843, (2004). ACKNOWLEDGEMENTS The authors would like to sincerely thank to Director, IPIRTI, Bangalore for permission and for providing necessary research facilit ies. [10] “Test M ethod for Specific Optical Density of Smoke Generated by Solid M aterials for Aerospace Applications”, ASTM F814 - 84B, (1995). [11] “Standard Practice for Conditioning Plastics for Testing”, ASTM D618, (1994). [12] ISO 13344 Determination of the Lethal Toxic Potency of Fire Effluents. REFERENCES [1] Baker, Dennis S.,” Wood in fire, flame spread and flame retardant treatments”, Chem. Ind. (London), 14, 485-490 (1981). [2] Stoecker, Wilbert F., “Smoke density measurement”, M ech. Eng. 72,793-798,(1950). [13] SO TR 13387,1-8: The application of fire performance concepts to design objectives; Design fire scenarios and design fires; Assessment and verification of mathematical fire models; Initiation and development of fire and generation of fire effluent; M ovement of fire effluent; Structural response and fire spread beyond the enclosure of origin; Detection, activation and suppression; Life safety: Occupant behavior, location and condition. [3] Dev, “Studies on fire retardant cum preservative composition”. J. Timber Dev. Assoc. India, 28, 30-33, (1982).

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