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Flame-Retardant Waterborne Polyurethanes
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Pursuing this research, very recently, the same group [43] exploited an addition reaction between hydroxyl-terminated polybutadiene acrylonitrile and DOPO; the resulting product was employed as a reactive-type flame retardant in the formulation of WPUs at three concentrations, namely 0.5, 1.0, and 2.0 wt.%. The presence of increasing amounts of the DOPO derivative turned out to increase the LOI values (that achieved 26.8%—vs. 18.4% for neat WPU—when 2.0 wt.% of modified DOPO was employed), as well as to enhance the vertical flame spread rating (from not rated, for neat WPU, up to V1, for the counterpart containing 2.0 wt.% of DOPO derivative). Besides, as assessed by forced combustion tests under 35 kW/m2 irradiative heat flux, the proposed flame-retardant strategy was very effective in decreasing either the thermal or the smoke parameters, as presented in Table 8.4.
Combustion Properties
Published in WeiQiang Pang, Luigi T. De Luca, XueZhong Fan, Oleg G. Glotov, FengQi Zhao, Boron-Based Fuel-Rich Propellant, 2019
WeiQiang Pang, Luigi T. De Luca, XueZhong Fan, Oleg G. Glotov, FengQi Zhao
Higher energy requirement is proposed for fuel-rich propellant to achieve satisfactory ramjet performance.18 It has been demonstrated through extensive testing and theoretical research that boron must be incorporated into the propellant to improve the energy of fuel-rich propellant (e.g. to achieve a specific impulse more than 10 kN·s kg−1). In addition, certain prerequisites shall be considered for the burning rate of propellant to ensure enough thrust from the motor,19–21 which obviously comes from the structure and shape of burning surface of the propellant grain inside the combustion gas generator. For example, with a specific impulse of 10 kN·s·kg−1 and flying with an M of 2 at sea level, the burning rate of an end surface burning grain shall be over 10 mm·s−1; while that of an internal perforation burning grain shall be about 1.5 mm·s−1. Below 3–7 MPa, the reference formulation of a fuel-rich propellant with 40% of B and 40% of oxidant is as follows: 10% of magnalium with 40% of B, 40% of oxidant mixture consisting of 33% of potassium perchlorate (KP) and 67% of AP, and 20% of hydroxyl-terminated polybutadiene (HTPB). In this reference formulation, the addition of Fe2O3 could increase the burning rate of propellant, while the addition of LiF might reduce the burning rate; the specific testing formulation is listed in Table 6.2 and the burning rate is indicated in Figures 6.1 and 6.2.
Advancements and Potential Prospects of Polymer/Metal Oxide Nanocomposites: From Laboratory Synthesis to Commercialization
Published in Shakeel Ahmed, Saiqa Ikram, Suvardhan Kanchi, Krishna Bisetty, Biocomposites, 2018
In the last few years, there has been an elevated interest in embedding inorganic nanoparticles into the polymer matrix. The introduction of inorganic nanoparticles into the polymer gives rise to magnetic, optical, and thermal properties in the nanocomposites. During in situ polymerization, there is in situ synthesis of nanoparticles followed by the polymerization of monomer, which acts as a solvent. Thus, there is a formation of intercalated nanocomposites [12]. In this process, the nanoparticle aggregation can be avoided since the nucleation process takes place inside the polymer matrix and particles grow within the matrix. Additionally, polymer chains have functional groups, which have a stabilizing effect on the formation of nanoparticles. Thus, this effect provides a uniform spatial distribution of nanoparticles in the polymer matrices, thereby preventing their aggregation. Stable nanocomposites are formed with potential properties. The strong interaction between the inorganic precursors and polymer matrix is the predominant factor for controlling the particle size and polydispersity. Polyurethane- TiO2 nanocomposites have been reported to be synthesized by the in situ synthesis approach with improved nanoparticle dispersion where the nanoparticles were prepared in a solution of prepolymer hydroxyl-terminated polybutadiene (HTPB). The resulting nanocomposite showed a higher performance as solid propellant binder than the nanocomposite fabricated by conventional powder or solution methods [13].
Effect of Polymeric Additives on Ignition, Combustion and Flame Characteristics and Soot Deposits of Crude Oil Droplets
Published in Combustion Science and Technology, 2023
Gurjap Singh, Mehdi Esmaeilpour, Albert Ratner
In the context of solid propellant applications, research has focused on thermal decomposition of polymers such as hydroxy-terminated polybutadiene (HTPB) which are commonly used as solid propellant binders or fuels. Chen & Brill (Chen and Brill 1991) have analyzed the combustion of HTPB doped with cross-linking agents. They found that when the HTPB is subjected to combustion-like conditions, the cross-linking agents evaporate out first, which is followed by HTPB exothermically cross-linking and cyclizing. This is followed by depolymerization and evolution of volatile products. All these processes are exothermic, proportional to the number of double bonds in parent polymer. Arisawa & Brill (Arisawa and Brill 1996) have investigated the pyrolysis of HTPB and concluded that evolution of gaseous products from the polymer is controlled by the bulk-phase decomposition reactions.
Combustion Characteristics of Boron-HTPB-Based Solid Fuels for Hybrid Gas Generator in Ducted Rocket Applications
Published in Combustion Science and Technology, 2019
Syed Alay Hashim, Srinibas Karmakar, Arnab Roy
The ramjet engine is considered to be an attractive propulsive device which offers simplicity, higher thrust, higher specific impulse, safety and working stability as compared to an equivalent rocket motor (Fry, 2004). Refinement of the fundamental design of solid fuel ramjet (SFRJ) engine has happened over last several decades and continues to be an active research area till date. In this field, Gany and Netzer and few other researchers have been working for last several years to build a small-scale ramjet combustion chamber which could be utilized to support analytical and numerical studies (Mady et al., 1978; Netzer, 1978; Netzer and Gany, 1991). The SFRJ have also been used to examine high-density fuel formulations containing polymer with embedded metal particles (Gany and Netzer, 1986; Natan and Gany, 1991). The most commonly used fuel is hydroxyl-terminated polybutadiene (HTPB) which also works as a binder for additives (Chiaverini et al., 1999) and provides higher specific impulse (Jain, 2002). Use of HTPB is significant to the propulsion community due to its extensive application in solid propellant rocket motors. The widespread use of HTPB is due to its desirable mechanical properties at a wide range of temperatures, even when it is highly loaded with metal particles (Muthiah et al., 1992, 1991).
Thermal decomposition and combustion characteristics of HTPB-coarse AP composite solid propellants catalyzed with Fe2O3
Published in Combustion Science and Technology, 2018
Manisha B. Padwal, Mohan Varma
Composite solid propellants (CSPs) contain oxidizer particles embedded in a matrix of organic fuel cum binder, along with additives to adjust mechanical, rheological, and ballistic properties. Ammonium perchlorate (AP) is a widely used inorganic oxidizer due to large oxygen content and good energetics, among other favorable factors. Hydroxyl-terminated polybutadiene (HTPB) is a commonly used polymeric fuel that supports higher solid filler loadings, gives superior performance, and enhances mechanical properties. HTPB-AP propellant system is very important to rocket propulsion and it continues to be a topic of investigations (Korokikh et al., 2017; Lu et al., 2012; Marothiya et al., 2017). The interest is spurred in part by many factors that affect the performance of HTPB-AP, many aspects of which are still being discovered (Korokikh et al., 2017; Marothiya et al., 2017). Korokikh et al. (2017) found that iron ultrafine powder in aluminized HTPB-AP increased the burning rate along with agglomeration tendency in the products. Random packing simulations (Marothiya et al., 2017) confirm that enhancement in burning rate of HTPB-AP-nano-Al by nano-Fe2O3 over micro-Fe2O3 is due to more uniform distribution of nano-Fe2O3 on AP.