Preparation and characterization of new flame retardant polyurethane composite and nanocomposite

In this work, a new flame retardant additive [2‐phenyl‐1,3,2 oxazaphospholidine 2‐oxide (POPO)] containing phosphorus and nitrogen is synthesized using phenyl phosphonic dichloride, ethanol amine, and copper (II) chloride, as catalyst. POPO is characterized by ¹H‐NMR, ¹³C‐NMR, and ³¹P‐NMR and used as additive in polyurethane composites. Moreover, two commercial flame retardant additives [tricalcium diphosphate and hexabromocyclododecane (HBCD)] as well as nanoclay are used to compare flame retardancy of the synthesized additive. Limited oxygen index (LOI) and time burning (flammability test) of polyurethane composites and nanocomposites are evaluated. The results of the LOI test demonstrate that POPO is an excellent flame retardant additive and can be used to improve flame retardancy of polyurethane composites. In addition, increasing the additive content leads to an improvement of the flame retardancy of the samples. The LOI results show, however, that POPO is a good flame retardant, but the high synthesis cost of this flame retardant is a major disadvantage. Thermogravimetric analysis results show that using POPO in polyurethane matrices leads to low thermal stability and high char residue. Moreover, the nanocomposite has better thermal stability than the other samples. Scanning electron microscope micrographs have been used to evaluate the char residue of the samples. These micrographs indicate that POPO is an intumescent flame retardant and HBCD follows a nonintumescent mechanism. Exfoliated/intercalated structures have been shown for nanocomposites by transmission electron microscope. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and Thermal Characterization of Polyurethane/Clay Nanocomposites Based on Palm Oil Polyol

Polyurethanes (PUs) are very versatile polymeric materials with a wide range of physical and chemical properties. PUs also have desirable properties, such as high abrasion resistance, tear strength, shock absorption, flexibility, and elasticity. Although they have poor thermal stability, it can be improved by using treated clay.

The objective of the present work is to study the thermal stability of polyurethane, polyurethane/montmorillonite (PU CTAB-mont 3% wt), and polyurethane/montmorillonite containing moca (PU Moca CTAB-mont 3% wt) nanocomposites based on palm oil polyol.

The interest of investigating the synthesis of polyurethane/clay nanocomposites based on palm oil polyol is to explore the use of palm oil polyol to partially replace petrochemical-based polyol.

Polyurethane/clay nanocomposites were prepared by a pre-polymer method and evaluated by Fourier Transform Infrared Spectra (FTIR) to determine micro-domain structures of segmented PU, PU CTAB-mont 3% wt, and PU Moca CTAB-mont 3% wt. The morphology of the nanocomposites was characterized by X-ray diffraction (X-RD), and flame retardant was investigated with thermogravimetric analysis (TGA). The result showed that in comparison with the virgin polyurethane, adding clay and moca demonstrated better thermal stability.     

Preparation and properties of in‐situ polymerized polyurethane/stearate intercalated layer double hydroxide nanocomposites

The present work deals with the effect of stearate intercalated layered double hydroxide (St‐LDH) loadings on the morphological, mechanical, thermal, adhesive and flame retardant properties of polyurethane (PU)/St‐LDH nanocomposites prepared by the in situ polymerization method. X‐ray diffraction and transmission electron microscopy studies confirmed that exfoliation takes place at 3 wt% loading followed by intercalation at higher filler loadings in the PU matrix. The exfoliated structure has been further verified by atomic force microscopy. The measurements of stress‐strain, thermogravimetric analysis, dynamic mechanical analysis, lap shear strength and peel strength analysis showed that the nanocomposites containing 3 wt% St‐LDH exhibit excellent improvement in tensile strength (ca 175%) and log storage modulus (ca 14%), while PU/St‐LDH (5 wt%) possesses optimum improvement in glass transition temperature (ca 6 °C), lap shear strength (200%) and peel strength (130%) over neat PU. In addition, the gradual improvements in limiting oxygen index value with St‐LDH loading indicated the higher effectiveness in providing better barrier properties as well as better flame retardant behavior. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of polyurethane/bentonite nanoclay based nanocomposites using toluene diisocyanate

Polyurethanes (PUs) prepolymers blended with bentonite nanoclay and without bentonite nanoclay were prepared by the reaction of toluene-2,4-diisocyanate (TDI) and hydroxyl terminated polybutadiene (HTPB), and the chain was further extended with 1,4-butane diol (1,4-BDO) to get final polyurethane nanocomposites (PUNC). A mixture of polymer and bentonite clay enriched in montmorillonite (MMT) was formed in solution polymerization, in which MMT dispersed depending on interaction of MMT with polymer chains. The molecular structure of the monomers and the prepared PU nanocomposites was confirmed by FTIR. A series of PUNCs were prepared by varying the percent compositions of bentonite nanoclay into the PU matrix. The existence of the clay in to the PU was confirmed by scanning electron microscope (SEM). SEM images verified the good dispersion of the bentonite nanoclay in PU matrix.     

Synthesis and characterisation of novel flame retardant polyurethanes containing designed phosphorus units

In this study, 2-carboxyethyl(phenyl)phosphinic acid (CEPPA) and trimethylolpropane (TMP) are used to synthesise a novel flame retardant containing phosphorus units: 5-hydroxy-3-(2-hydroxyethyl)-3-methylpentyl-3-[2-carboxyethylphenylphosphine]propanoate (HMCPP). Then, 4,4′-diphenylmethane diisocyanate (MDI) is taken as a hard segment, with HMCPP and polycaprolactone diol (PCL) as soft segments, and 1,4-butanediol (BD) is used as a chain extender to prepare a novel polyurethane (HMCPP/PUs). The results of ¹H NMR and FT-IR reveal the successful synthesis of the HMCPP flame retardant. The gel permeation chromatography analysis demonstrates that an increase in the HMCPP content is accompanied by a decrease in the molecular weight of PU. The FT-IR analysis reveals the complete NCO group exhaustion of PU and HMCPP/PUs. The thermal analysis shows that the initial decomposition temperature of PU is higher than that of HMCPP/PUs by 19 °C. Both DMA and DSC analyses show that the Tg and the dynamic Tg of PU are higher than those of HMCPP/PU. Stress-strain tests indicate that the HMCPP content is increased, the maximum stress and Young’s modulus of HMCPP/PUs are decreased, and the elongation at break is increased. All of the HMCPP/PUs exhibit excellent flame retardancy, obtaining higher than 27.7 in limiting oxygen indices and a V-0 rating in the UL-94 test.     

Diffusion and sorption of benzene vapor through polybutadiene‐, polybutadiene/styrene‐, and polybutadiene/acrylonitrile‐based polyurethanes

A series of polyurethane (PU) films made from toluene diisocyanate (TDI), 1,4‐butanediol (BDO), and hydroxyl‐terminated polybutadiene (HTPB), hydroxyl terminated polybutadiene/styrene (HTBS), or hydroxyl terminated polybutadiene/acrylonitrile (HTBN) was synthesized by solution polymerization. The absorption of benzene vapor was found mainly in the soft phase. The equilibrium adsorption (M_∞) was reduced with increasing hard segment content for all the PUs. The values of M_∞ were in the sequence of HTBN‐PUs > HTBS‐PUs > HTPB‐PUs, which could be explained by the different interaction parameters between soft segments and benzene. The HTBN‐PU film showed the lowest degree of phase segregation and had more hard segments intermixed in the soft phase, restricting the movement of soft segments, and therefore resulted to non‐Fickian behavior, while the HTPB‐PU is antithetical. FTIR and atomic force microscopy were utilized to identify the hydrogen bonding behavior and morphology change of the PU films before and after the absorption of benzene vapor. The tensile strength of the HTBN‐PUs showed a greater decrease than that of HTBS‐PUs and HTPB‐PUs after absorbing benzene vapor. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2984–2991, 2004     

A polymeric flame retardant and surfactant‐free montmorillonite nanocomposites: Preparation and exfoliation mechanism discussion

A polymeric flame retardant (PDEPD) and various amounts of sodium montmorillonite (Na‐MMT) nanocomposites with exfoliation structure were prepared via one‐step polycondensation, attempting to prepare flame‐retardant nanocomposites. The nanocomposites exhibited high thermal stability at high temperature. Based on several comparative studies, we investigated and proposed the possible exfoliation mechanism of Na‐MMT in PDEPD substrate. The microscale combustion calorimeter and cone calorimeter results showed the PDEPD/Na‐MMT nanocomposites could significantly improve the flame retardancy of polystyrene and polyurethane elastomer (TPU), especially the TPU matrix. This study provides new viewpoint for preparing flame‐retardant nanocomposites without surfactants. POLYM. COMPOS., 35:167–173, 2014. © 2013 Society of Plastics Engineers     

Synthesis and characterization of inherently flame‐retardant and anti‐dripping thermoplastic poly(imides‐urethane)s

A series of thermoplastic poly(imide‐urethane)s (TPIUs), based on 4,4′‐diphenylmethane diisocyanate (MDI) and pyromellitic anhydride (PMDA) as hard segments and poly(tetrahydrofuran) (PTMG) as soft segments, has been prepared by a two‐step polymerization process. The objective of this study is to prepare a type of intrinsically flame‐retardant polyurethane by incorporating PMDA as a flame retardant in the main chains. The thermal behavior and flame retardancies of the TPIUs have been characterized by thermal gravimetric (TG) analysis and limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter tests. The results indicate that the TPIUs display outstanding performance. The temperature at 5% mass loss (T_5%) and LOI value increase with the hard‐segment contents, while the total heat released (THR) and peak heat release rate (p‐HRR) show the opposite trend. Furthermore, the T_5% of TPIU211 (molar ratio: MDI : PTMG : PMDA = 2 : 1 : 1) is 33.2°C higher than that of the conventional thermoplastic polyurethane TPU211 (molar ratio: MDI : PTMG : 1,4‐butanediol = 2 : 1 : 1), and the THR and p‐HRR of TPIU211 are 14.62% and 64.02% lower than the respective parameters of TPU211. In addition, UL‐94 vertical burning tests show that the TPIUs exhibit excellent antidripping effects. The ultimate tensile strengths of the TPIUs reached 23.1?37.6 MPa with increasing hard segment contents, which meets the requirement of mechanical properties with regard to practical use. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40801.     

Newly Modified MMT and Its Application with Intumescent Additives as New Flame Retardant System for Polyurethane Polymer

Montmorillonite (MMT) clay was modified using the new modifier butyl acrylate resin. The new modified MMT have better thermal stability in comparison with butyl acrylate. The newly modified MMT mixed with polyurethane (PU) and formed a new nanocomposite PU formulation, and the structure has been proven by atomic force microscopy (AFM). New flame retardant systems containing the modified nanoclay were added to the polyuerethane polymer. The flammability properties of the new PU formulations were evaluated by cone calorimeter and ISO 1210 tests. The thermal stability of the formulations was studied by TGA and DSC. The new flame retardant systems gave the PU higher fire properties and good thermal stability.     

用于超纤革PU浆料的无卤阻燃改性

选择了有机磷系和磷氮协同两种不同的无卤阻燃剂与溶剂型PU进行共混制备无卤阻燃PU,对其力学性能、阻燃性能及耐碱性能进行了系统研究。结果发现:相较于磷氮协同阻燃剂(SN-605),采用有机磷系阻燃剂(JL-30)改性PU显示出更好的阻燃性能与耐碱性能;当阻燃剂质量分数为11.1%时,阻燃PU的LOI可以达到29.1%,垂直燃烧测试达到V-0级;并且具有较好的耐碱性能,在90℃、30 g/L NaOH溶液中碱处理40 min后,其LOI仍然可以达到28.7%,垂直燃烧测试等级没有下降;但两种阻燃剂的加入均会使PU的抗张强度出现不同程度的下降。此外,热失重测试(TG)显示,两种阻燃PU的阻燃机制不同,JL阻燃剂的加入使PU的热分解温度降低,并且在800℃时的残炭量没有明显增加,呈现明显的气相阻燃机制;而SN阻燃剂的加入使PU的残炭量明显增加,呈现明显的凝聚相阻燃机制。     

Graphene and poly(ionic liquid) modified polyurethane sponges with enhanced flame‐retardant properties

Graphene (Gr) and poly(ionic liquid) (PIL) modified polyurethane (PU) sponges with enhanced flame‐retardant properties were prepared by the direct dip coating of Gr and ionic liquid (IL) monomers onto a PU sponge followed by the polymerization of IL monomers under thermal initiation. With a content of 1.5% Gr in IL, the limiting oxygen index (LOI) of PU–PIL–Gr was 26.1%, whereas the neat PU sponge showed an LOI of only 17.9%. The horizontal flame test results indicate that PIL–Gr prevented horizontal flame spread and eliminated melt dripping. Compared with that of the neat PU sponge, the peak heat release rate of PU–PIL–Gr decreased about 22.0%. These improvements on flame retardancy might have been due to a hybrid flame retardant originating from Gr (which acted as carbon source) and PIL (which contained the flame‐retardant elements) in the PU sponge and the formation of protective layers, which isolated the oxygen and heat more effectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45477.     

New intumescent flame‐retardant agent: Application to polyurethane coatings

The first part of this investigation focused on the synthesis and characterization of a new type of intumescent flame‐retardant (IFR) agent. Four steps were used in the synthesis process. The structure was characterized by FTIR, magic‐angle spinning nuclear magnetic resonance (MAS‐NMR) ¹³C spectroscopy, and elemental analysis. The addition of an IFR agent into polyurethane (PU) varnish led to an improvement in its carbonization and flame‐retardant (FR) properties. The second part focused on the evaluation of such characteristics as FR property, thermal stability of IFR/PU‐based coatings, rheology of IFR/PU‐based coating solutions, and mechanical properties such as hardness, adhesion, and flexibility of IFR/PU‐based dry coating films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1193–1206, 2004     

A flame‐retardant composite foam: foaming polyurethane in melamine formaldehyde foam skeleton

A composite foam, polyurethane–melamine formaldehyde (PU/MF) foam, was prepared through foaming PU resins in the three‐dimensional netlike skeleton of MF foam. The chemical structure, morphology, cell size and distribution, flame retardancy, thermal properties and mechanical properties of such composite foam were systematically investigated. It was found that the PU/MF foam possessed better fire retardancy than pristine PU foam and achieved self‐extinguishment. Moreover, no melt dripping occurred due to the contribution of the carbonized MF skeleton network. In order to further improve the flame retardancy of the composite foam, a small amount of a phosphorus flame retardant (ammonium polyphosphate) and a char‐forming agent (pentaerythritol) were incorporated into the foam, together with the nitrogen‐rich MF, thus constituting an intumescent flame‐retardant (IFR) system. Owing to the IFR system, the flame‐retardant PU/MF foam can generate a large bulk of expanded char acting as an efficient shielding layer to hold back the diffusion of heat and oxygen. As a result, the flame‐retardant PU/MF foam achieved a higher limiting oxygen index of 31.2% and exhibited immediate self‐extinguishment. It exhibited significantly reduced peak heat release rate and total heat release, as well as higher char residual ratio compared to PU foam. Furthermore, the composite foam also showed obviously improved mechanical performance in comparison with PU foam. Overall, the present investigation provided a new approach for fabricating a polymer composite foam with satisfactory flame retardancy and good comprehensive properties. © 2018 Society of Chemical Industry     

Highly flame‐retardant bio‐based polyurethanes using novel reactive polyols

Poor flame retardancy of polyurethanes (PU) is a global issue as it limits their applications particularly in construction, automobile, and household appliances industries. The global challenge of high flammability of PU can be addressed by incorporating flame‐retardant materials. However, additive flame‐retardants are non‐compatible and depreciate the properties of PU. Hence, reactive flame‐retardants (RFR) based on aliphatic (Ali‐1 and Ali‐2) and aromatic (Ar‐1 and Ar‐2) structured bromine compounds were synthesized and used to prepare bio‐based PU using limonene dimercaptan. The aromatic bromine containing foams showed higher close cell content (average 97 and 100%) and compressive strength (230 and 325 kPa) to that of aliphatic bromine containing foams. Similar behavior was observed for a horizontal burning test where with a low concentration of bromine (5 wt %) in the foams for Ar‐1 and Ar‐2 displayed a burning time of 12.5 and 11.8 s while, Ali‐1 and Ali‐2 displayed burning time of 25.7 and 37 s, respectively. Neat foam showed a burning time of 74 s. The percentage weight loss for neat PU foam was 26.5%, while foams containing 5 wt % bromine in Ali‐1, Ali‐2, Ar‐1, and Ar‐2 foams displayed weight loss of 11.3, 14, 7.9, and 14%, respectively. Our results suggest that flame retardant PU foams could be prepared effectively by using RFR materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46027.     

Thermal induced shape‐memory and self‐healing of segmented polyurethane containing diselenide bonds

Herein, we synthesized a series of polyurethane copolymers (PUs) with poly(1,4‐butylene adipate) glycol as soft segment and 2,4‐toluene diisocyanate as well as extenders including 1,4‐butanediol and di(1‐hydroxyethylene) diselenide as hard segment. The chemical structure, thermal property, crystallization behavior, shape memory, and self‐healing performances of the PUs were systematically characterized by a series of experiments. It was found that the PU2 containing a higher diselenide component (～33 mol %) exhibited both shape memory and self‐healing behaviors under a moderate temperature (～57 °C). Meanwhile, the PUs showed a good repeatability of shape memory function, and their fixity and recovery ratios were all above 90%. Additionally, the dynamic exchangeable feature of diselenide bonding endues the PUs chains with an acceptable reprocessability and self‐healing performances, and the PU2 sample could be healed for five times by thermal treatment with the healing efficiencies above 70%. This work provides a heuristic perspective for the development of shape memory and self‐healing materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46326.     

Aliphatic polycarbonate‐based polyurethane elastomers and nanocomposites. II. Mechanical,thermal, and gas transport properties

Thermal, thermomechanical, tensile and gas transport properties of aliphatic polycarbonate‐based polyurethanes (PC‐PUs) and their nanocomposites with bentonite for organic systems were studied. Hard segments are formed from hexamethylene diisocyanate and butane‐1,4‐diol. All PC‐PUs and their nanocomposites feature high degree of the phase separation. Three phase transitions were detected by temperature‐modulated differential scanning calorimetry (TMDSC) and dynamic mechanical thermal analysis. TMDSC revealed the filler affinity both to soft and hard segments, even though the affinity to hard segments is much stronger. Elongation‐at‐break at ambient temperatures is mostly over 700%, which leads together with high tensile strength (in some cases) to very high toughness values (over 200 mJ/mm³). The addition of 1 wt % of bentonite does not practically affect mechanical properties implying its very good incorporation into the PU matrix. Permeabilities and other gas transport properties depend on regularity of PC‐diol and on hard segment content, but the variations are insignificant. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effects of soft‐segment molecular weight and organic modifier on properties of organic‐modified MMT‐PU nanocomposites

The effects of soft‐segment molecular weight and organic modification of montmorillonite (MMT) on thermal and mechanical properties of segmented polyurethane (PU) elastomers were investigated. The PU/MMT nanocomposites were prepared by in situ polymerization, and the compositions included soft segments with number average molecular weights of 1000, 2000, and 2900, and organic‐modified MMT (including MMT‐30B and MMT‐I30E). The nanocomposites produced were characterized using wide‐angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and mechanical testing. The TEM and XRD results revealed that both MMT‐30B and MMT‐I30E were intercalated, and partially exfoliated by the PU. Mechanical tests showed that the PU1000 series in soft‐segment molecular weight yielded superior tensile properties compared with the PU2000 and PU2900 series. Also, for a given molecular weight of soft segment in PU, the MMT‐30B nanocomposites exhibited greater increases in Young's modulus, tensile strength, and elongation at break than the MMT‐I30E counterpart, and the crystallinity of PU was enhanced by the clays. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of an intercalating agent on the morphology and thermal and flame‐retardant properties of low‐density polyethylene/layered double hydroxide nanocomposites prepared by melt intercalation

The effects of an intercalating agent on the morphology and thermal and flame‐retardant properties of low‐density polyethylene (LDPE)/layered double hydroxide (LDH) nanocomposites were studied with Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, microscale combustion calorimetry, thermogravimetric analysis, and mechanical property measurements. X‐ray diffraction and transmission electron microscopy demonstrated that after intercalation with stearate anion (SA) or dodecyl sulfate anion (DS), organo‐LDH could be nanodispersed in an LDPE matrix with exfoliated structures or intercalated structures simultaneously with partially exfoliated structures, respectively, via melt intercalation. However, the unmodified LDH composites yielded only microcomposites. Microscale combustion calorimetry, thermogravimetric analysis, and dynamic Fourier transform infrared spectra showed the following order for the flame‐retardant and thermal properties: LDPE/SA‐modified LDH > LDPE/DS‐modified LDH > LDPE/NO₃‐modified LDH > LDPE. The higher performance of the LDPE/LDH nanocomposites with respect to flame retardance and thermal stability could be attributed to the better dispersion state of the LDH layers in the LDPE matrix and the greater hindrance effect of LDH layers on the diffusion of oxygen and volatile products throughout the composite materials when they were exposed to burning or thermal degradation. The tensile strength and elongation at break of the LDPE/LDH nanocomposites decreased to some extent because of the decrease in the crystallinity of the LDPE matrix. A transmittance test showed that the transparency of the exfoliated LDPE/SA‐modified LDH nanocomposite was very close to that of neat LDPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011