https://orcid.org/0000-0003-3868-181X
Abstract
The high flammability of rigid polyurethane foams has limited emerging applications (sensors, space travel, and others). Enhancing the mechanical, thermal, and flame-retardant properties of RPUF is an important theme in flame retardant science and technology. This study compares the fire performance of polyurethane foams (PUF) containing four different flame retardants: tris (2-chloro-1-methylethyl) phosphate (TCPP), tris (1,3-dichloro-2-propyl) phosphate (TDCP), melamine phosphate (MP), and aluminum trihydrate (ATH). The flame retardants were added at 10% and 20% rates, and the resulting PUFs were characterized for their morphological, mechanical, and thermal properties using various analytical techniques. The fire performance of the PUFs was evaluated using ISO 11925-2 and UL-94 tests. The results demonstrated that all four flame retardants enhanced the fire performance of the PUFs, with TCPP and TDCP exhibiting the most favorable outcomes. The study highlights the importance of using flame retardants in PUFs to improve their fire performance in various applications.
1. Introduction
Polyurethane (PU), a polymer formed by establishing a carbamate (urethane) bond of organic components, has a wide range of applications and is known for its versatility and high performance. PU products are used in the aerospace industry, bedding, building materials, construction, electronics, furnishings, food packaging, footwear, the automotive industry, toys, medical devices, and more due to their chemical diversity and unique physical properties. PUs are typically used for comfort applications or as thermal and sound insulation materials [Citation1–5]. Polyurethanes are versatile polymeric materials with advantages such as their excellent abrasion resistance, high toughness, chemical resistance, flexibility, and low film-forming temperatures. They have been widely used in coating, foam, adhesives, and composites [Citation4–6].
The disadvantage of rigid polyurethane foam is its high flammability. The foam quickly catches fire, and the flame spreads rapidly due to its highly porous structure and the large specific surface area [Citation7,Citation8]. When polyurethane foam burns, it releases toxic gases such as carbon monoxide (CO), hydrogen cyanide (HCN), hydrogen halides, irritant gases, and nitrogen oxides (NOX), as well as various thermal decomposition products [Citation7–10]. Therefore, using environmentally friendly and non-hazardous flame retardants is important to prevent the burning of polyurethane foam products.
Effective flame retardant agents should have high thermal and mechanical stability and sufficient flame retardancy. They should also be cost-effective, non-toxic, non-volatile, and suitable for industrial use. Furthermore, they should not leach from the polymer structure and should not compromise the mechanical properties of polyurethane foam.
There are two types of flame retardants: additive and reactive. Additive flame retardants are physically mixed with the polymer, while reactive flame retardants are incorporated through chemical reactions. Additive flame retardants can be categorized into inorganic flame retardants (such as metal hydroxides, antimony, boron, and phosphorus compounds), halogenated organic flame retardants (including brominated and chlorinated flame retardants), organophosphorus flame retardants (including non-halogenated compounds and halogenated phosphates), and nitrogen-based flame retardants.
Halogenated flame retardant agents are highly effective in improving fire resistance. However, their use has been restricted and even banned due to their tendency to migrate from the surface over time and release toxic and carcinogenic gases when burned. These factors have also raised concerns about their potential adverse effects on human health and the environment. As a result, there has been extensive research on developing non-halogenated flame retardant agents as alternatives [Citation11,Citation12].
Tris (1-chloro-2-propyl)phosphate (TCPP) is soluble in water and organic solvents and toxic to aquatic life, and is commonly used as a flame retardant. It is relatively stable but can hydrolyze in water and react with specific oxidizing agents. It should be handled cautiously, and proper safety protocols should be followed when working with this chemical [Citation13].
Tris (1,3-dichloro-2-propyl) phosphate (TDCP) is considered to be toxic to aquatic life and may cause long-term adverse effects in the environment. It can also be harmful if ingested or inhaled. It is commonly used as a flame retardant in various applications, such as plastics, textiles, and foam. TDCP can react with potent oxidizing agents and can decompose under high temperatures or in the presence of specific catalysts [Citation14].
Aluminum trihydrate (ATH) is insoluble in water and most organic solvents. ATH is an effective flame retardant and is commonly used in applications such as plastics, rubber, and textiles. ATH is relatively stable under normal conditions but can decompose at high temperatures. Non-halogen flame-retardant melamine phosphate (MP) is insoluble in water but is soluble in organic solvents such as ethanol and acetone. MP is an effective flame retardant and is commonly used in applications such as plastics, coatings, and textiles. It is compatible with a wide range of polymers and other additives [Citation15].
The study investigates and compares flame retardancy, thermal stability, physical and mechanical properties, and other relevant characteristics of polyurethanes containing different TCPP, TDCP, ATH, and MP concentrations. The study can provide valuable insights into the effectiveness of varying flame retardants and their ratios in polyurethane foam. This can help develop safer and more efficient flame retardant formulations for industrial applications.
2. Experimental
2.1. Materials
The following materials were used in the work: polymix is formulized polyether-based polyol consists of blowing agents, surfactants, and catalysts (Flokser Chemical, Turkey), polymeric methylene diphenyl diisocyanate (PMDI, Merck, Germany), tris (1-chloro-2 propyl) phosphate (TCPP, pure, Flokser Chemical, Turkey), tris (1,3-dichloro-2-propyl) phosphate (TDCP pure, Flokser Chemical, Turkey), melamine polyphosphate (MP, pure, Flokser Chemical, Turkey), aluminum trihydrate (ATH pure, Flokser Chemical, Turkey).
2.2. Preparation of polyurethane foam (PUF)
Rigid polyurethane foams (PUFs) were synthesized using the specified amounts in a one-pot preparation method. The PUF synthesis involved the addition of isocyanate to the polymix mixture for 3 s, using a brushless type stirrer operating at 3000 rpm and room temperature. The flame retardants (FRs) weight ratios in the polymix solution were approximately 10% and 20%. The formulations of the samples are presented in Table .
Table 1. Formulation of each PUF sample.
2.3. Characterization methods (morphological, mechanical, and thermal properties)
The viscosity of the PUF was measured using a Brookfield Viscometer according to ASTM D4878. The reaction parameters of the PUF, including cream time, gel time, and tack free time, were recorded by mixing both the polymix and FR. Surface morphology changes of the PUF were analyzed using a JEOL JMS-7001F model scanning electron microscope (SEM). The cell size of the PUF was measured using image analysis from the SEM results. Thermogravimetric analyses (TGA) were carried out using an EXSTAR (SII TG/DTA7200) by measuring sample mass of 3,0–10,0 mg under a nitrogen atmosphere at a heating rate of 10°Cmin−1 from 30°C to 700°C. Compressive strength was tested using an INSTRON according to TS EN ISO 844. The compressive stress at 10% relative deformation of the PUF samples was measured. PUF density was calculated according to DIN 51757 from the weight and dimensions of the samples (8 cm × 4 cm × 4 cm). Differential scanning calorimetry (DSC) was performed by heating the samples from −90°C to 200°C under a nitrogen atmosphere at a heating rate of 10°Cmin−1 using aluminum pans. The small flame test for determining the ignitability of PUFs was analyzed based on ISO 11925-2. The UL-94 vertical burning test was performed using the Marestik brand UL-94 test cabinet. The test sample was vertically mounted in the cabinet and exposed to a small flame for a specified duration. The flame was then removed, and the sample was observed for a certain period to determine whether it continued to burn or self-extinguished. The test was repeated three times for each sample, and the results were recorded. The flammability test was conducted using an LOI test apparatus (Stanton Redcroft FTA unit, East Grinstead, UK) according to the ISO4589 standard. The specimens used for LOI measurement had dimensions of 100 × 10 × 3 mm3 (Length × Width × Thickness), and five specimens per sample were measured. The reported values represent the average LOI values obtained from the measurements.
3. Results and discussion
3.1. Relative viscosity
Polyurethanes are polymers that can be tracked for molecular weight by measuring their viscosity. Viscosity measures the resistance of a solution or liquid and is directly related to molecular weight. Therefore, the viscosity of polyurethanes provides information about their molecular weight and is an important parameter for ensuring consistency in polymer production.
Table illustrates the impact of the mixture of polymix and flame retardant on viscosity. When TCPP is added to the polymix mixture in a range of 10–20 wt %, it acts as a plasticizer, reducing the intermolecular forces between the polymers in the mixture. This decrease in intermolecular forces leads to a reduction in the viscosity of the mix. On the other hand, when different combinations are added to the polymix, they can act as cross-linking agents, increasing the intermolecular forces between the polymers and increasing viscosity. Cross-linking agents form chemical bonds between the polymer chains, creating a three-dimensional network, which can restrict the polymer chains’ movement and increase the mixture’s viscosity.
Table 2. The viscosity of mixture polymix and the flame retardants.
3.2. Reaction profile
The reaction profile of polyurethane foam (PUF) containing flame retardants refers to the changes that occur during its synthesis, which are evaluated based on its cream time, gel time, and tack-free time. These parameters were tested at 21°C with a structural shaping of 3000 rpm, and Table presents the values for neat PUF and four different additives.
Table 3. Reaction profile of PUFs.
The cream time indicates the duration between mixing the components and the expansion of the mixture to form bubbles. The gel time is the time it takes for the mixture to become a semi-solid gel state. The tack-free time refers to the duration until the foam surface is dry to the touch and not sticky anymore.
The data presented in the table reveals that the addition of flame retardants generally reduces the cream time, with the lowest value of 5.1 s being observed for TDCP at 20% weight. However, the impact of flame retardants on gel time and tack-free time is more variable, depending on their type and concentration. Hence, it is crucial to carefully choose the flame retardant for optimizing foam properties, as it can significantly affect the reaction profile of the foam.
3.3. Scanning electron microscopy (SEM)
The microstructure of polyurethane materials, including the morphology, size, and distribution of pores, significantly impacts their physical and mechanical properties. Figure shows SEM images of the samples.
Figure 1. Scanning electron microscopic microphotographs of polyurethane samples.
Polyurethane foam can have an open-cell or closed-cell structure, depending on the production method and the specific application. In the case of pure polyurethane foam, it typically has a closed-cell structure, which means that the individual cells of the foam are sealed and do not interconnect with each other. This type of foam is often used in insulation and packaging applications, as it has excellent thermal and acoustic insulation properties due to the trapped air in the cells. The cells themselves can take on a variety of shapes, including spherical, polyhedral, or irregular, depending on the production method and the specific formulation of the foam [Citation16].
Adding flame retardants to polyurethane can significantly impact the material’s properties. Liquid flame retardants such as TCPP and TDCP reduce the foam’s flammability by reacting with and inhibiting the combustion process. They do not significantly affect the pore formation or distribution of the foam, so its overall morphology and cell structure remain largely unchanged [Citation17].
SEM images of polyurethane foam with added liquid flame retardants such as TCPP and TDCP may show little to no change in cell morphology compared to pure polyurethane foam. This is because liquid flame retardants do not significantly affect the pore formation or distribution of the foam. Instead, they work to reduce the flammability of the foam by reacting with and inhibiting the combustion process. As a result, SEM images of foam with liquid flame retardants may appear similar to those of pure polyurethane foam, with uniform spherical or polyhedral-shaped cells.
On the other hand, adding powder flame retardants such as MP and ATH can affect the pore formation and morphology of the foam. They can lead to the formation of spherical-shaped pores, and the uniform distribution of powder flame retardants can result in better mechanical properties and structural morphology. However, excessive powder flame retardants can also negatively impact the foam’s properties, such as its thermal and acoustic insulation performance [Citation18]. The powders with uniform size distribution can lead to better mechanical properties and structure morphology [Citation19]. These substances can influence pore formation by facilitating nucleation during foam formation. As a result of this interaction, the use of MP and ATH can reduce pore size.
3.4. Thermogravimetric analysis (TGA)
TGA analysis is a method used to evaluate the thermal stability of polyurethane foam (PUF) under air and inert atmosphere. Flame retardants added to PUF can decompose at high temperatures and react with the polymer, creating a char layer on the surface of the material. Figure shows the TGA plots of PUF degradation, and the results are summarized in Table .
Figure 2. TGA curves of TCPP (a), TDCP (b), MP (c), ATH (d) containing PUFs.
Table 4. The thermal properties of the PUFs.
The results show that the addition of flame retardants affects the thermal stability of the PUF samples. The neat PUF sample (BYT-STD) has a Tmax temperature of 356,76°C and an ash amount of 14,13%.
The reduction of Tmax is not solely due to the decomposing of TCPP, TDCP, MP, ATH flame retardants, but also due to the interaction between the polymer and the partly decomposed flame retardant. The shift in Tmax indicates a change in the decomposition mechanism of the polymer and can be explained by the interaction of the polymer with the flame retardant additives.
Adding TCPP and TDCP flame retardants to the PUF samples causes a decrease in the Tmax temperature, but it also increases the char yield, as indicated by the ash amount [Citation1,Citation2]. When the data is examined, it can be observed that the thermal stability of the PU samples with flame retardant additives decreases compared to the pure sample. This effect increases as the TCPP ratio increases, and it is attributed to the plasticizing effect of the increasing additive ratio [Citation20].
As the amount of TCPP or TDCP is increased, the char yield also increases. Adding MP also increases the char yield, but to a lesser extent than TCPP and TDCP [Citation21]. Adding ATH flame retardants to the PUF samples has a negligible effect on the Tmax temperature and ash amount. Overall, the results indicate that adding flame retardants to PUF samples can improve their thermal stability by increasing the char yield. Still, it also reduces their Tmax temperature, which can limit their maximum operating temperature [Citation2].
3.5. The compressive strength (TS EN ISO 844)
The mechanical properties of PUFs are an essential performance indicator in their applications.
It is well known that foam mechanical strength depends on the foam density, cell structure and size, decreasing for larger cell sizes and lower densities [Citation18]. While adding an FR into the PU matrix causes a reduction in the mechanical properties, the compressive strengths of the polyurethane foam could also improve [Citation22–25].
The mechanical properties of PUFs are a critical measure of their performance in various applications. The strength of foam is influenced by its density, cell structure, and size, with larger cell sizes and lower densities leading to decreased strength [Citation23]. While the addition of FRs to the PU matrix can reduce in mechanical properties, it can also enhance the compressive strengths of the foam [Citation22,Citation23,Citation25].
Table shows the compressive stress values at 10% deformation and density values of different PUF samples with varying amounts of flame retardants (FR). Density affects the cost of physical-mechanical properties of the PUFs [Citation25]. The addition of flame retardant agents can enhance the fire resistance properties of the polymer matrix in the foam. This is due to the flame retardant agents causing the polymer to shrink and tighten the bonds between cells. This process can result in the formation of a tighter cellular structure, leading to an increase in density. Flame retardant agents can also inhibit the formation of combustible gases and distribute heat when exposed to fire, thereby preventing the degradation of the foam structure. This can contribute to an improvement in the foam’s compressive strength as it possesses a tighter structure [Citation26].
Table 5. The compressive strength properties of the PUFs.
As shown in the table, the compressive stress at 10% deformation of the neat PUF sample (BYT-STD) is 370,30 kPa, and its density is 53,69 kg/m3. When 10% TCPP or TDCP flame retardants are added, the compressive stress at 10% deformation increases to 423,12 or 403,24 kPa, respectively, with a slight increase in density. When the amount of TCPP or TDCP is increased to 20%, the compressive stress at 10% deformation further increases to 535,70 or 515,79 kPa, respectively, with a higher density.
The addition of MP and ATH flame retardants has a more significant effect on the density of the foam than on its compressive strength (Figures and ). The compressive stress at 10% deformation of the PUF samples containing 10% MP or 20% MP is lower than that of the neat PUF sample, with a moderate increase in density. The addition of 10% or 20% ATH flame retardants has a negligible effect on the compressive strength of the foam, with a slight increase in density.
Figure 3. Compressive strength at 10% nominal relative deformation and density values of samples.
Figure 4. Compressive strength and density values of samples.
Overall, the results indicate that adding certain flame retardants to PUF samples can improve their compressive strength properties. The figure demonstrates a linear increase in density as the amount of flame retardant (FR) additives increases. The increase in density in foam composites can be attributed to the higher density of FRs compared to that of the original foam (RPUF), as well as the increased viscosity that hinders the foaming process when FRs are present [Citation26–28].
3.6. Differential scanning calorimetry (DSC)
A DSC Q2000 was used for analyzing the thermal properties of samples. Samples were put into aluminum pans and heated from −90°C to 200°C at a heating rate of 10°Cmin−1 under a nitrogen atmosphere.
The DSC curves of PUs are shown in Figure , and the data are listed in Table . Table shows the Differential Scanning Calorimetry (DSC) results of the PUF samples with varying amounts of flame retardants (FR). Figure shows the glass transition temperature of the soft segment (Tg) and PU samples’ endothermic melting peak (Tm).
Figure 5. DSC curves of pure (a), TCPP (b), TDCP (c), MP (d), ATH (e) containing PUFs.
Table 6. DSC results of the PUFs.
The Tg value represents the glass transition temperature, which is the temperature at which the polymer transitions from a glassy to a rubbery state. The Tm value represents the melting temperature, which is the temperature at which the polymer melts.
The table shows that the Tg and Tm values of the PUF samples vary depending on the type and amount of flame retardant added. The neat PUF sample (BYT-STD) has a Tg range of 66,75–88,11°C and a Tm value of 85,81°C. When 10% TCPP or TDCP flame retardants are added, the Tg and Tm values slightly decrease compared to the neat sample. However, when the amount of TCPP or TDCP is increased to 20%, the Tg and Tm values decrease further.
The addition of MP and ATH flame retardants has a more significant effect on the Tg and Tm values of the foam than on its density or compressive strength. The Tg and Tm values of the PUF samples containing 10% MP or 20% MP are lower than those of the neat PUF sample, with a moderate decrease in Tg values and a slight decrease in Tm values. The addition of 10% or 20% ATH flame retardants has a negligible effect on the Tg and Tm values of the foam.
In summary, the DSC analysis results suggest that adding flame retardants, particularly TCPP and TDCP, can slightly decrease the Tg and Tm values of the PUF samples. Meanwhile, adding MP and ATH flame retardants can moderately or slightly decrease the Tg and Tm values, respectively.
Tm refers to the temperature at which the maximum rate of decomposition occurs during the thermal degradation of a material. In this case, the shift in Tm suggests that the main decomposition step of the polymer is interacting with the flame retardant, causing a change in the thermal properties of the material. This interaction may lead to the formation of char layers or other protective mechanisms during combustion, which can improve the flame retardancy properties of the foam. Therefore, Tmax is a useful parameter for evaluating the effect of flame retardants on the thermal degradation behavior of polymers [Citation29,Citation30].
3.7. Reaction to fire tests (ISO 11925-2)
The small flame test for determining the ignitability of PUFs was analyzed based on ISO 11925-2.
During the test, the flame is applied to the bottom edge of the sample using a small Bunsen burner flame for 15 s. The flame is then removed, and the sample is observed for 15 s to determine if it continues to burn or self-extinguishes. The test is repeated three times for each sample, and the results are recorded. Based on the results, the sample is classified into different classes ranging from A1 to F, with A1 being the highest level of performance (self-extinguishing within 5 s and without flaming droplets) and F being the lowest level of performance (burns for more than 30 s and flaming droplets are allowed). In TCPP-added PU foams, the progression of the flame is much slower compared to the pure foam, accompanied by reduced smoke emission. It has been observed that the flame progression is slower and smoke emission is lower in PU foams with 10% and 20% TCPP content [Citation20]. The ISO 11925-2 small flame test results showed that while PU/ATH (10%) burned, other foams showed less flame progression as the fireproofing agent additive increased (Figure ).
Figure 6. Fire tests results of PUFs.
3.8. Flame retardancy and burning behaviors
3.8.1. Vertical burning test (UL-94)
The UL-94 vertical burning test is a widely used method to assess the flammability of flame retardant polyurethane materials. In this test, samples of different PUF compositions were subjected to a vertical flame ignition and their behavior during and after exposure to the flame was evaluated.
The test results are shown in Table , which lists the UL-94 rating, flame extinguishing time, combustion time up to the holding clamp, and cotton ignition for each sample. The BYT-STD sample did not receive any UL-94 rating, indicating that it did not meet the criteria for any rating category. The other samples that included different flame retardant additives received UL-94 ratings of V-0 or V-1, with the latter indicating a lower level of flame retardancy.
Table 7. UL-94 vertical burning test.
The results indicate that adding flame retardant additives to PUF compositions can significantly improve their flammability characteristics. Specifically, increasing the amount of TCPP or TDCP flame retardant additives led to a lower flame extinguishing time and improved UL-94 rating. Adding MP and ATH flame retardant additives also had an impact but to a lesser extent. Overall, the UL-94 vertical burning test provides important insights into the flammability characteristics of PUF materials and the effectiveness of flame retardant additives in improving their fire safety properties.
PUF-containing additives are currently restricted due to their potential toxicity and environmental problems [Citation31]. Therefore there is a great need to develop environmentally friendly FRs to replace these halogen-based compounds.
3.9. Limiting oxygen index (LOI)
LOI values of polyurethane foams containing TCPP, TDCP, MP, and ATH additives are summarized in Figure .
Figure 7. The LOI values of the polyurethanes containing TCPP, TDCP, MP, and ATH.
The PU samples containing 20 wt% of TCPP, TDCP, and MP exhibit high thermal stability, excellent flame retardant properties, UL94 V-0 rating, and LOI values of 22.9%, 31%, and 33%, respectively. The pure PU has a very low LOI value of 19.1, and it does not have a UL-94 rating. This value indicates that the material has low flame resistance.
With the addition of ATH, The LOI value has increased from 20.5% to 21.9%. The flame retardant additive ATH (Aluminum trihydrate) has slightly increased the material’s flame resistance.
In conclusion, flame retardant additives such as TCPP, TDCP, MP, and ATH increase the LOI values, thereby enhancing the material’s flame resistance. Higher LOI values indicate better flame resistance and lower propensity for combustion, while lower LOI values can increase the material’s tendency for combustion and its burning rate.
4. Economic analyses
It is estimated that flame retardants, with a market volume of over 7.2 billion dollars in 2022, will reach an approximate value of 12 billion dollars by 2027, with an annual growth rate of 4.9%. The primary drivers of market growth are the expansion of end-use industries and the implementation of stricter fire safety regulations. There is a growing need for flame retardants across various sectors to mitigate fire-related risks. However, environmental and health concerns associated with traditional flame retardants, particularly brominated and chlorinated compounds, hinder the market’s progress. As a result, the demand for more environmentally friendly flame retardants like phosphorus and nitrogen has surged [Citation32]. Globally, brominated chemicals, organophosphorus, and antimony oxide hold approximately 78% of the market volume, valued at around 6 billion dollars. Chlorinated compounds account for 6%, while aluminum trihydrate (ATH) holds a smaller share at 7% [Citation33]. TCPP is commonly used as a flame retardant, and its cost can be moderate compared to other options. It provides good fire-retardant properties and is widely available. TDCP is another flame retardant that falls within the cost range of TCPP. Its price can vary depending on the specific supplier and market conditions. (Chlorinated phosphorous-based flame retardants in children’s articles containing foam, 2016, The Danish Environmental Protection Agency) MP is typically more expensive compared to the previous flame retardants mentioned above. Its cost can be higher due to factors such as production processes and availability. Aluminum trihydrate (ATH), zinc borate (ZnB), and clay are often considered cost-effective flame retardant option. It is relatively inexpensive compared to other flame retardants [Citation34].
5. Conclusion
This study examined the effects of different flame retardant additives, namely TCPP, TDCP, MP, and ATH, on the properties of polyurethane foams. The research showed that flame retardants performed similarly at both 10% and 20% concentrations. TCPP acted as a plasticizer, reducing intermolecular forces and viscosity, while other flame retardants acted as cross-linking agents, increasing viscosity. The addition of flame retardants generally decreased cream time, with TDCP at 20% weight showing the lowest value. When TCPP or TDCP was added, the foam exhibited increased compressive strength at 10% deformation and slightly higher density due to the enhanced intermolecular forces and a stronger polymer network. In contrast, MP and ATH primarily affected foam density rather than compressive strength. They acted as fillers, increasing viscosity and resulting in thicker foam. The study highlighted the positive impact of flame retardants on the flammability properties of polyurethane foam. Higher concentrations of TCPP or TDCP led to shorter flame extinguishing time and better UL-94 rating, indicating superior fire resistance. While MP and ATH also had an effect, it was comparatively weaker. The findings emphasized the importance of the UL-94 vertical burning test in evaluating fire safety and the efficacy of flame retardant additives in enhancing fire protection capabilities in PUF materials. Overall, the flame retardant performances of TCPP, TDCP, MP, and ATH at 10% and 20% concentrations were found to be similar.
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No potential conflict of interest was reported by the author(s).
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References
- Dong F, Wang Y, Wang S. et al. Flame-retarded polyurethane foam conferred by a bio-based nitrogen-phosphorus-containing flame retardant. React Funct Polym. 2021;168:105057. doi:10.1016/j.reactfunctpolym.2021.105057
- Hamidov M, Çakmakçi E, VezirKahraman M. Autocatalytic reactive flame retardants for rigid polyurethane foams. Mater Chem Phys. 2021;267:124636. doi:10.1016/j.matchemphys.2021.124636
- Datta J, Kosiorek P. Synthesis, structure and properties of poly(ether-urethane)s synthesized using a tri-functional oxypropylated glycerol as a polyol. J Therm Anal Calorim. 2017;128:155–167. doi:10.1007/s10973-016-5928-2
- Gama NV, Ferreira A, Barros-Timmons A. Polyurethane foams: past, present, and future. Materials (Basel). 2018;11(10):1841. doi:10.3390/ma11101841
- Thirumal M, Khastgir D, Nando GB. Halogen-free flame retardant PUF: effect of melamine compounds on mechanical, thermal and flame retardant properties. Polym Degrad Stab. 2010;95(6):1138–1145. doi:10.1016/j.polymdegradstab.2010.01.035
- Rong Y, Bo W, Mengdi L. Preparation, characterization and thermal degradation behavior of rigid polyurethane foam using a malic acid based polyols. Industrial Crops Products. 2019;136:121–128. doi:10.1016/j.indcrop.2019.04.073
- Chen HB, Shen P, Chen MJ, et al. Highly efficient flame retardant polyurethane foam with alginate/clay aerogel coating. ACS Appl Mater Interfaces. 2016;8:47. doi:10.1021/acsami.5b09730
- Rao WH, Hu ZY, Xu HX, et al. Flame-retardant flexible polyurethane foams with highly efficient melamine salt. Ind Eng Chem Res. 2017;56:7112–7119. doi:10.1021/acs.iecr.7b01335
- Son MH, Kim Y, Jo YH, et al. Assessment of chemical asphyxia caused by toxic gases generated from rigid polyurethane foam (RPUF) fires. Forensic Sci Int. 2021;328:111011. doi:10.1016/j.forsciint.2021.111011
- McKenna ST, Hull TR. The fire toxicity of polyurethane foams. Fire Sci Rev. 2016;5:3. doi:10.1186/s40038-016-0012-3
- Dufour P, Charlier C. Brominated flame retardant: environmental and exposed individuals' health impact. Ann Biol Clin (Paris). 2017;75(2):146–157. doi:10.1684/abc.2017.1221
- Sykam K, Sivanandan S, Basak P. 1,2,3-Triazole mediated, non-halogenated phosphorus containing protective coatings from castor oil: flame retardant and anti-corrosion applications. Prog Org Coat. 2023;178:107475. doi:10.1016/j.porgcoat.2023.107475
- Ji C, Lu Z, Xu L, et al. Global responses to tris(1-chloro-2-propyl)phosphate (TCPP) in rockfish sebastes schlegeli using integrated proteomic and metabolomic approach. Sci Total Environ. 2020;724:138307. doi:10.1016/j.scitotenv.2020.138307
- Wang C, Chen H, Li H, et al. Review of emerging contaminant tris(1,3-dichloro-2-propyl)phosphate: environmental occurrence, exposure, and risks to organisms and human health. Environ Int. 2020;143:105946. doi:10.1016/j.envint.2020.105946
- Silva EHP, Aguiar JCF, Ribeiro M. et al. Compression and morphological properties of a bio-based polyurethane foam with aluminum hydroxide. J Mater Des Appl. 2022;236(7). doi:10.1177/14644207211059077
- Bartczak P, Siwińska-Ciesielczyk K, Haak N, et al. Closed-cell polyurethane spray foam obtained with novel TiO2–ZnO hybrid fillers – mechanical, insulating properties and microbial purity. J Build Eng. 2023;65:105760. doi:10.1016/j.jobe.2022.105760
- Zhang T, Yu M, Huang Y, et al. Design and manufacturing of cost-effective tannin-based polyurethane foam as an efficient and reusable absorbent for oil and solvents. Ind Crops Prod. 2022;189:115815. doi:10.1016/j.indcrop.2022.115815.
- Hoffendahl C, Fontaine G, Duquesne S. The combination of aluminum trihydroxide (ATH) and melamine borate (MB) as fire retardant additives for elastomeric ethylene vinyl acetate (EVA). Polym Degrad Stabil. 2015;115:77–88. doi:10.1016/j.polymdegradstab.2015.03.001
- Al-Maharma AY, Patil SP, Markert P. Effects of porosity on the mechanical properties of additively manufactured components: a critical review. Mater Res Express. 2020;7(12):122001. doi:10.1088/2053-1591/abcc5d
- Zengin Küçükşenlik N. Investıgatıon the effects of flame retardants on thermal and mechanıcal propertıes of PU foams [Gebze Technıcal Unıversıty Graduate School of Natural and Applıed Scıences Master Thesıs]; 2019.
- Salasinska K, Borucka M, Leszczyńska M, et al. Analysis of flammability and smoke emission of rigid polyurethane foams modified with nanoparticles and halogen-free fire retardants. J Therm Anal Calorim. 2017;130:131–141. doi:10.1007/s10973-017-6294-4
- Yang R, Wang B, Han X, et al. Synthesis and characterization of flame retardant rigid polyurethane foam based on a reactive flame retardant containing phosphazene and cyclophosphonate. Polym Degrad Stab. 2017;144:62–69. doi:10.1016/j.polymdegradstab.2017.08.008
- Wang SX, Zhao HB, Rao WH, et al. Inherently flame-retardant rigid polyurethane foams with excellent thermal insulation and mechanical properties. Polymer. 2018;153:616–625. doi:10.1016/j.polymer.2018.08.068
- Liu L, Wang Z, Zhu M. Flame retardant, mechanical and thermal insulating properties of rigid polyurethane foam modified by nano zirconium amino-tris-(methylenephosphonate) and expandable graphite. Polym Degrad Stab. 2019;170:108997. doi:10.1016/j.polymdegradstab.2019.108997
- Bhoyate S, Ionescu M, Kahol PK, et al. Castor-oil derived nonhalogenated reactive flame-retardant-based polyurethane foams with significant reduced heat release rate. J Appl Polym Sci. 2019;136:47276. doi:10.1002/app.47276
- Izarra I, Borreguero AM, Garrido I, et al. Comparison of flexible polyurethane foams properties from different polymer polyether polyols. Polym Test. 2021;100:107268. doi:10.1016/j.polymertesting.2021.107268
- Bhoyate S, Ionescu M, Kahol PK, et al. Sustainable flame-retardant polyurethanes using renewable resources. Ind Crop Prod. 2018;123:480–488. doi:10.1016/j.indcrop.2018.07.025
- Akdoğan E. Effects of some additives on the properties of rigid polyurethane foams: flame retardancy, thermal conductivity and compressive strength [Eskişehir Anadolu University, MSc. thesıs]; 2018.
- Sykam K, Meka KKR, Donempudi S. Intumescent phosphorus and triazole-based flame-retardant polyurethane foams from castor oil. ACS Omega. 2019;4:1086–1094. doi:10.1021/acsomega.8b02968
- Vasiljevi J, Colovi M, Korošin NC, et al. Effect of different flame-retardant bridged DOPO derivatives on properties of in situ produced fiber-forming polyamide 6. Polymers (Basel). 2020;12:657. doi:10.3390/polym12030657
- Matusinovic Z, Wilkie CA. Degradation, stabilization, and flammability of polymer blends. Polymer Blends Handbook. 2014: 1395–1430. doi:10.1007/978-94-007-6064-6_16
- https://www.marketsandmarkets.com/Market-Reports/flame-retardant-chemicals-market-686.html. Accessed 09 June 2023.
- Yücel MB. The existence and economy of huntite in Turkey. Natural Resources Economy Bull. 2018;25:31–37.
- Thirumal M, Singha NK, Khastgir D, et al. Halogen-Free flame-retardant rigid polyurethane foams: effect of alumina trihydrate and triphenylphosphate on the properties of polyurethane foams. J Appl Polym Sci. 2010;116(4):2260–2268. doi:10.1002/app.31626