RELATIONSHIP BETWEEN MOISTURE CONTENT AND FLAMMABILITY OF CERRADO SPECIES IN SOUTHERN TOCANTINS

This study aimed to analyze the relationship between moisture content and flammability of nine plant species from the Cerrado in southern Tocantins. The species studied were: Machaerium brasiliense, Qualea grandiflora, Luehea grandiflora, Campomanesia guaviroba, Astronium fraxinifolium, Curatella americana, Bauhinia forficata, Vatairea macrocarpa, and Anacardium Occidentale. The plants were analyzed at four moisture contents (M1, M2, M3, and M4). For each level, 50 samples (1 g ± 0.1 g) of each species were collected, and 50 repetitions of burning were performed. The parameters analyzed were: time to ignition (TI), frequency of ignition (FI), duration of combustion (DC), combustion index (CI), flammability value (FV), and height of flames (HF). Our results showed that moisture contents influence flammability in Cerrado plant species. The correlation coefficients between moisture and flammability parameters were r = 0.951 (TI), r = -0.962 (DC), r = -0.977 (HF), and r = -0.988 (FI).

High-speed camera test of newly developed igniter’s charges for artillery rounds

The article presents the results of the high-speed camera test of newly developed igniter’s charges for artillery rounds. The test was performed to take a closer look at the ignition process of mixtures, that is, to check the time-to-ignition of samples, and to assess the presence and quantity of solid igniting particles (if any). Five compositions were tested: Three of them contained the new igniter’s charges developed by the Military Institute of Armament Technology, and the other two contained black powder in different granularity classes as a comparison mixture. This article presents the collated test results.

Determination of Time-to-ignition and Flaming Duration of Biomasses in a Muffle Furnace

Measuring the energy characteristics of solid biofuels can help to determine the most suitable species for combustion. The objective of this study is to propose a new methodology for determining the ignition time and flaming duration in lignocellulosic biomass. A muffle furnace was used, instead of an epiradiador, to measure the variables. The optimal oven temperature was defined according to the average time-to-ignition of biomasses in the literature. Ten biomasses were analyzed to obtain their high heating value, volatile matter, fixed carbon content, ash content, time-to-ignition, and flaming duration. The results showed a high correlation between the biomass volatile content, time-to-ignition, and flaming duration. In the literature, it is described that high levels of volatile materials accelerate the ignition of the material. Thus, the association between the volatile matter and the variables analyzed justifies the use of the muffle furnace methodology. Furthermore, biomasses with high levels of volatile matter have longer flaming durations than other solid biofuels.

Ignition of Fuel Beds by Cigarettes: A Conceptual Model to Assess Fuel Bed Moisture Content and Wind Velocity Effect on the Ignition Time and Probability

A conceptual model based on the balance of energy in a system composed of a burning cigarette, ambient flow and a porous fuel bed is proposed to study the burning of a single cigarette and the process of fuel bed dehydration, pyrolysis and its eventual ignition or combustion extinction. Model predictions of time to ignition and of the probability of ignition as a function of fuel bed moisture content and ambient flow velocity are compared with results obtained in laboratory ignition tests of straw fuel beds for various ambient conditions. According to this study, the main parameters influencing the models developed are the fuel bed and tobacco moisture content, as well as the flow velocity.

Silver nanoparticle modified carbon fiber-reinforced polymer material for resistance against thermal damage induced by irradiation

We investigated the resistance of carbon fiber-reinforced plastics (CFRP) to thermal radiation when silver nanoparticles are added to the resin. An epoxy based CFRP material filled with up to 10 wt.% silver nanoparticles, with respect to the polymer matrix, shows an increase in time to ignition of up to ∼ 30% when irradiated from one side with an electrical heater with heat fluxes of 35 and 80 kW/m2. Scattering and specular reflectance of infrared light was analyzed before thermal irradiation, showing enhanced scattering of samples with increasing silver particle content, which correlates linearly to the time to ignition. The reaction to fire properties of the CFRP, analyzed by cone calorimetry, are also influenced positively by the silver nanoparticles. The thermal conductivity, as measured by laser-flash-analysis, shows no influence by the nanoparticles. Therefore, the increase in time to ignition, as well as the more homogeneous combustion, are not due to changes in conductivity, but to scattering and reflection effects caused by the nanoparticles. The modified material shows no decline in interlaminar shear strength, representing structural properties. Health and environmental risks by nanoparticle release during production, combustion, and machining of the modified CFRP are also investigated. The preliminary results show no additional hazards.

The effect of fibre length and matrix modification on the fire performance of thermoplastic composites: The behaviour of PP as an example of non-charring matrix

The fire performance of fibre-reinforced polypropylene (PP) was investigated with respect to fibre length and modification of the matrix. Fibre lengths of 3 mm, 12 mm, and continuous fibres were used as reinforcements. E-glass continuous fabrics were melt impregnated with PP and consolidated via compression moulding. E-glass fibre-reinforced PP pellets of 3 and 12 mm were compression moulded. Cone calorimetry tests with incident radiant fluxes of 20, 30 and 35 kW m−2 were used to investigate the fire properties of PP glass fibre composites. Results showed that continuous glass fibre reinforced PP exhibits the best fire performance at 20 kW m−2, while 3-mm fibre has the best performance at 35 kW m−2; 12-mm fibre-reinforced PP exhibitedthe lowest performance in comparison with 3-mm and continuous glass fibre reinforcement. Melic-anhydride (MA)-modified PP was found to increase the heat release rate (HRR) by up to 44% and time to ignition by up to 10% depending on the heat flux applied in comparison with unmodified PP. The glass fibre-reinforced composite made with MA-modified PP has 5–12% lower mean HRR and similar time to ignition in comparison with glass fibre composite made by unmodified PP. This suggests improved fibre adhesion plays a role of the fire performance of glass fibre-reinforced PP.

Comparative Analysis of Peat Fibre Properties and Peat Fibre-Based Knits Flammability

A very promising cellulose-based natural fibre that is suitable for use in the textile industry is peat fibre. This fibre is a by-product of peat excavation, purified by separating it from other components. In this study, the morphological, chemical and mechanical properties of peat fibres as well as flammability of peat-based knitted fabrics were analysed. The average diameter of the peat fibres is ~60 μm, but it varies in very wide ranges – 25–150 μm; however, the number of fibres with diameter more than 100 μm is very low. As the peat fibre contains a high amount of lignin, lignin amount in the mixed peat/cotton yarn is relatively high too. Lignin is responsible for enhanced flame retardancy; therefore, time to ignition of the peat knit is ~30% higher than that of the cotton knit. Consequently, peat fibre can be used in the knitted structure in order to significantly reduce its flammability. In order to increase the flame retardancy, the knits have been treated by flame retardant in various concentrations. It was found that around the burned hole on the peat knit, treated by very low concentration flame retardant, forms charred area and the knit stops to burn even if the flame source is not removed.