聚氨酯／聚磷酸胺体系的阻燃及力学性能

应用热重量分析，水平燃烧，应力－应变和扫描电镜等实验手段，研究了聚氨酯／聚磷酸胺（ＰＵ／ＰＰＡ）体系的热分解特性以及阻燃和力学性能，实验结果表明，随阻燃剂ＰＰＡ添加量的增加，ＰＵ的热分解峰明显地移向 温，并与阻燃机理有关，在ＰＵ中加入ＰＰＡ可显著改善ＰＵ的阻燃性能，但同时也使的力不性强度明显下降。     

Bi-phase flame-retardant effect of hexa-phenoxy-cyclotriphosphazene on rigid polyurethane foams containing expandable graphite

The flame-retardant rigid polyurethane (PU) foams with hexa-phenoxy-cyclotriphosphazene/expandable graphite (HPCP/EG) were prepared through box-foaming in our laboratory. The flame retardancy of PU foams was characterized using the limiting oxygen index and cone calorimeter. The results show that the incorporation of HPCP into the PU foams containing EG enhanced flame retardancy. The main degradation process of HPCP in PU foams was investigated by pyrolysis gas chromatography/mass spectroscopy. HPCP during combustion generated phenoxyl and PO₂ free radicals, which could quench the flammable free radicals produced by the matrix and hamper the free radical chain reaction of combustion. This observation shows that HPCP produced a gas-phase flame-retardant effect in this specimen. Additionally, micro-morphology, elemental composition and content of residual char of the flame-retardant PU foams after the cone calorimeter test were also characterized using scanning electron microscope and energy dispersive X-ray microanalyser. The results exhibit that the partial phosphorus from HPCP remained in the residual char, and HPCP significantly enhanced the strength and compatibility of the char layer formed by the PU foams containing EG. These results indicate the important function of HPCP in condensed phase. Thus, HPCP exhibited gas-phase and condensed-phase flame-retardant effects on the PU/EG foams.     

Exceptionally flame-retardant flexible polyurethane foam composites: synergistic effect of the silicone resin/graphene oxide coating

A facile strategy was developed to fabricate flexible polyurethane (PU) foam composites with exceptional flame retardancy. The approach involves the incorporation of graphene oxide (GO) into a silicone resin (SiR) solution, which is then deposited onto a PU foam surface via the dip-coating technique and cured. Fourier-transform infrared spectroscopy, scanning electron microscopy, and Raman spectroscopy measurements demonstrated that the SiR and GO were successfully coated onto the PU skeleton and the intrinsic porous structure of the PU foam remained intact. The effects of SiR and GO on the mechanical and thermal stability and flame retardancy of PU composites were evaluated through compression tests, thermogravimetric analysis, vertical combustion tests, and the limiting oxygen index. The measurement results revealed that the composites (PU@SiR-GO) showed superior flame retardancy and thermal and mechanical stability compared to pristine PU or PU coated with SiR alone. The mechanical and thermal stability and the flame-retardant properties of the PU composites were enhanced significantly with increasing GO content. Based on the composition, microstructure, and surface morphology of PU@SiR-GO composites before and after combustion tests, a possible flame-retardance mechanism is proposed. This work provides a simple and effective strategy for fabricating flame-retardant composites with improved mechanical performance.     

Molecular design and properties of intrinsic flame-retardant P-N synergistic epoxy resin

In recent years, the poor weather resistance and aging resistance of additive flame retardants have caused researchers to pay attention to reactive flame retardants. A novel P-N coacting epoxy curing agent with intrinsic flame retardancy was designed and synthesized. The mechanical properties, crosslinking curing properties and flame-retardant properties of intrinsic flame-retardant epoxy resin were characterized. The results show that the cross-linking curing performance of hexa (3,5-diamino-1,2,4 triazolyl)-cyclotriphosphonitrile) (VCP) is lower than that of DDM. This is due to the decrease in cross-linking density caused by the VCP ring molecular structure. Therefore, the mechanical properties of the epoxy resin cured with VCP decreased, but the flame-retardant properties of the material significantly improved. The limiting oxygen index of the VCP/EP flame retardant epoxy thermosets was 27.3%, reaching the UL 94 V-1 level. The peak heat release rate and total heat release rate of the VCP/EP flame retardant epoxy thermosets were significantly reduced. The flame retardancy mechanism was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and x-ray photoelectron spectroscopy. The results show that the intrinsic flame-retardant P-N coacting epoxy resin has excellent curing and flame-retardant properties.     

Synthesis of a green reactive flame-retardant polyether polyol and its application

The low-flame retardancy properties of pure rigid polyurethane (PU) foams hindered its practical application in many cases for the safety and environmental concern. Although rigid PU foams with flame retardants can achieve standard of fire resistance, addition of flame retardants in PU can worsen its mechanical properties, enlarge production cost, and induce safety problems. Therefore, green reactive flame-retardant polyether polyols (GPP) have been considered as one of the best solutions. In this work, the GPP by the ring-opening polymerization of the self-made environmentally friendly melamine resin (EFMR) with propylene oxide are synthesized with their hydroxyl number of 390 ~ 420 mg KOH/g, and the structure of GPP product was identified by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The flame-retardant rigid polyurethane foams (RPUFs) were successfully prepared with GPP as the polyol, the results showed that the addition of GPP can greatly improve the thermal stability and flame retardancy of the RPUFs prepared. The RPUF were prepared by fully GPP with 30.4% of limiting oxygen index and 350 kpa of compressive strength. These properties are qualified for commercial utilization. Therefore, this GPP provides great prospect in the development of specified flame-retardant PU materials.     

Polyurethane coatings based on linseed oil phosphate ester polyols with intumescent flame retardants

The effect of intumescent flame retardants on the properties of polyurethane (PU) coatings based on 2 kinds of phosphate ester polyol was studied. Synthesizing polyols, phosphorylation of epoxidized linseed oil with phosphoric acid was performed in the presence of isopropyl alcohol (IPA polyol) or diethylene glycol butyl ether (DGBE polyol). The obtained polyols were characterized by Fourier transform infrared (FTIR) and ³¹P nuclear magnetic resonance (NMR) spectroscopy. The properties of neat PU coatings based on 2 polyols and those filled with different content (up to 25 wt%) of melamine (Mel), ammonium polyphosphate (APP), and expandable graphite (EG) were studied using thermal gravimetric analysis (TGA), and tensile and cone calorimeter tests. It was found that IPA polyol contained not only phosphate monoesters and diesters, as DGBE polyol, but also phosphate triester and pyrophosphate monoester. Due to this difference, IPA neat and filled coatings had higher tensile characteristics and char residue in a TGA test. Also, the flame retardancy of IPA coatings, compared with that of DGBE coatings, was higher. In a cone calorimeter test, coatings filled with Mel showed a small increase of flame retardancy, but the total smoke release (TSR) of wood samples with coatings decreased noticeably. The effect of APP on the flame retardancy of coatings was higher, but in contrast, the TSR of samples increased with increasing APP content. Even greater decrease of flammability parameters and a simultaneous significant decrease of TSR were shown by the samples with IPA coatings filled with EG.     

光敏性含磷聚氨酯丙烯酸酯(P-PUA)阻燃预聚物的合成与性能

合成了4种不同结构的光敏性含磷聚氨酯丙烯酸酯阻燃预聚物,并对其结构进行了表征。研究了以所制预聚物为基料的光固化涂料的柔韧性、附着力、硬度等基本物理性能和耐热防火性能。结果表明,该涂料能达到市售PUA涂料的基本物理性能,并具有较高的分解温度,800℃下形成的炭渣能达到涂层原重的20%左右,具有一定的耐热防火性能;以结构相似的阻燃预聚物为基料的涂层,其耐热防火性能随含磷量的增加而提高;预聚物主链中芳环含量也影响涂层的耐热防火性能,相对分子质量相近的预聚物,其主链上的芳环数量增加一倍,涂层在800℃下w(炭渣)能增加5个百分点。     

A novel DOPO-containing HTBN endowing waterborne polyurethane with excellent flame retardance and mechanical properties

A novel flame-retardant DHTBN (hydroxyl-terminated polybutadiene acrylonitrile modified with DOPO) with phosphorus-containing pendant groups is synthesized based on addition reaction between the hydroxyl-terminated polybutadiene acrylonitrile and DOPO, which is followed to prepare flame-retarded WPU (FR-WPU). The chemical structures of DHTBN and FR-WPU are confirmed via ³¹P NMR, XPS, and FT-IR. The mechanical properties, thermal stability, and flame retardancy of FR-WPU are conducted a series of tests. The tensile strength and elongation at break for the FR-WPU films first increased and then decreased with increasing of DOPO contents. The results show that the incorporation of DHTBN into the WPU backbone slightly reduces the thermal stability of FR-WPU. However, the incorporation of DHTBN into WPU improves the flame retardancy. The TGA-FIR and Py-GC-MS results indicate the gas phase flame-retardant effect of DHTBN. Furthermore, the morphology, elemental composition, and content of residual char from the FR-WPU exhibited condensed-phase flame-retardant effects on the WPU films.     

Preparation and performance of waterborne polyurethane coatings based on the synergistic flame retardant of ferrocene,phosphorus and nitrogen

A synergistic reactive flame-retardant polyol (AFeDH) containing ferrocene, phosphorus, and nitrogen elements was synthesized from ferro-formaldehyde, 5-amino-1,3, 4-thiadiazole-2-mercaptan, 9,10-dihydro-9-oxa-10-phos-phaphenanthrene-10-oxide and hydroxyl terminated polybutadiene acrylonitrile, and then applied for flame retarding waterborne polyurethane (WPU). The chemical structures of intermediates and final products were well characterized to confirm the successful preparation of ternary P-N-Fe flame retardant. The effects of incorporated AFeDH on thermal stability, flame retardancy and mechanical properties of AFeDH/WPU films were systematically studied. The results indicated that LOI value increased with the increase amount of AFeDH, while the value then decreased as the loading content above 6 wt%. This increase in flame retardancy results from the competition between the catalytic degradation of iron and the catalytic carbonization. Benefiting from the good synergistic effects among each element of AFeDH, the WPU/AFeDH films perform the decreased heat release and smoke production. Moreover, the flame retardant films also show the enhanced tensile strength of 33.8 MPa and elongation at break of 763.3%. Therefore, this novel halogen-free flame retardant shows an excellent synergistic effect among P, N, and Fe elements, which has a great potential in the application of flame retardant WPU.     

Preparation and performance evaluation of phosphorus-nitrogen synergism flame-retardant water-borne coatings for cotton and polyester fabrics

Three phosphorus-nitrogen content effective synergist flame-retardant water-borne coatings have been synthesized, and their structures were characterized by infrared spectroscopy. Cotton and polyester fabrics have been treated by coatings to improve their flame retardancy. The thermal performances and flame retardant properties of treated samples were investigated by thermogravimetric analysis (TGA), horizontal flame test, vertical burning test, limiting oxygen index (LOI), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), respectively. The combustion performances of cotton and polyester fabrics have proven to be strongly affected by flame-retardant coatings and HFD-coating performed the best. As a result, the LOI value of treated cotton increased to 22.5, and the UL-94 value of treated polyester achieved V-0. In addition, the antistatic behavior, hydrostatic pressure, tearing strength and wrinkle recovery angle of samples were studied carefully, and the results showed that all of these performances were improved.     

Preparation and characterization of polyurethane flame‐retardant coatings using pyrophosphoric lactone‐modified polyesters/isophorone diisocyanate–isocyanurate

Pyrophosphoric lactone‐modified polyester containing two phosphorous functional groups in one structural unit of base resin was synthesized to prepare a nontoxic, reactive flame‐retardant coatings. Then, the pyrophosphoric lactone‐modified polyester was cured at room temperature with isocyanate and isophorone diisocyanate (IPDI)–isocyanurate to get a two‐component polyurethane flame‐retardant coatings (TAPPU). Comparing the physical properties of the films of TAPPU with the film of nonflame‐retardant coatings, no deterioration of physical properties was observed with the incorporation of a flame‐retarding component into the resin. Three kinds of flame retarding tests were conducted, including the 45° Meckel burner method, limiting oxygen index method (LOI method), and oxygen combustion method with Cone calorimeter. It was observed that the char lengths were 3.1～4.5 cm and LOI values were 27～30%. These results indicate that the prepared coatings are good flame‐retardant ones. It was also found that the flame retardancy of those coatings was increased with the contents of phosphorous. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2316–2327, 2001     

阻燃环氧树脂胶黏剂的研制

采用以KH-560硅烷偶联剂包覆三聚氰胺多聚磷酸酯（MPP）为阻燃剂,以环氧树脂E-44为基体,制备阻燃环氧树脂胶黏剂。通过对所制得胶黏剂进行剪切强度测试、热失重测试以及阻燃性能测试,研究了包覆阻燃剂对环氧树脂胶黏剂力学性能、热稳定性和阻燃性能的影响。结果表明,采用包覆处理MPP为阻燃剂制备的阻燃环氧树脂胶黏剂综合性能较好,其剪切强度为19．9MPa,氧指数为31．2。最佳配方为100份环氧树脂、30份阻燃剂、30份固化剂、温度为70℃。     

层状硅酸盐纳米复合材料的阻燃研究及现状分析

聚合物/层状硅酸盐(PLS)纳米复合材料是国内外阻燃材料领域中近年来研究的热点。它满足了新型阻燃材料发展的要求,在提高阻燃性能的同时能够很少降低或者不降低材料原有的其他性能,有时甚至可以提高部分聚合物基体的机械性能、气体阻隔性能、环保性能等。本文综述了聚合物/层状硅酸盐纳米复合材料的研究近况;简要介绍了该纳米复合材料的特点及阻燃性能的测试;讨论了其燃烧性能和阻燃机理;重点研究了以聚酰胺(PA)等聚合物为基质、以层状硅酸盐为无机阻燃添加剂的纳米复合材料的阻燃性能。通过与常规阻燃剂进行比较,发现聚合物/层状硅酸盐纳米复合材料在阻燃性能、机械性能、加工性能和环保等方面均优于常规阻燃剂;最后本文还指出了该材料在阻燃研究中目前尚存在的问题,并对其开发应用前景进行了展望。     

Carbon nanotubes coated with phosphorus-nitrogen flame retardant and its application in epoxy thermosets

ABSTRACT

Carbon nanotubes coated with phosphorus-nitrogen flame retardant (PDAP-CNTs) were produced. The compositions and structures of PDAP-CNTs were systematically characterized, and the flame retardancy of PDAP-CNTs/EP composites were also tested. The results indicated that PDAP-CNTs demonstrated excellent flame retardancy performance on the flame-retardant EP composites (FR-EP), incorporation of 5.0wt% PDAP-CNTs improved the LOI values of EP from 26.0% to 31.8% and reached UL-94 V-0 classification. The analysis of flame-retardant mechanism indicating the flame-retardant ability of PDAP-CNTs was ascribed to the synergism of the phosphorus-nitrogen containing coating layer (PDAP) and CNTs.     

Intrinsic flame-retardant epoxy resin composites with benzoxazine: Effect of a catalyst and a low curing temperature

Three kinds of inherent flame-retardant epoxy resin (EP) composites with 20 wt % benzoxazine (BOZ) were prepared with different curing processes with 2-methyl-1H-imidazole (MI) as a catalyst or/and changes in the curing temperature. The effects of the curing process on the flame retardancy, thermal stability, mechanical properties, and curing behaviors were investigated. The composite with added MI cured at low temperature (EBM–LT) had the best properties. It possessed a 35.3% limiting oxygen index and achieved a UL 94 V-0 rating. Thermogravimetric analysis indicated that EBM–LT had the best thermal stability among the three kinds of EP composites with BOZ. The EP composites with BOZ mainly displayed a condensed-phase flame-retardant mechanism. The mechanical properties improvement was attributed to the formation of a heterogeneous network. Differential scanning calorimetry indicated that MI reacted with EP and catalyzed the homopolymerization of BOZ, and EP reacted with BOZ. Fourier transform infrared spectroscopy analysis indicated that curing at lower temperature caused the formation of more homopolymers of BOZ. The relationship of the curing process, network structure, and properties of EP composites with BOZ was established; this could help with the design of high-performance EP composites with BOZ. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47847.     

Recent trends in environmentally friendly water-borne polyurethane coatings: A review

Environmentally friendly waterborne polyurethane (WPU) coatings are used extensively due to their low VOCs emission than solvent based PU coatings. Additionally, WPU coatings have low temperature flexibility, pH stability, water resistance, superior solvent resistance, outstanding weathering resistance and desirable chemical and mechanical properties. This review provides an overview on the recent developments of WPU coatings and their value added applications in the coatings and paint industry. UV-cured WPU coatings provide an important class of green and ecofriendly coatings with outstanding mechanical properties and rapid curing system. Hyper-branched polyurethanes (PUs) show interesting properties, such as high solubility, reactivity and good rheological behavior owing to multiple end groups, compact molecular structure and diminishing chain entanglement. Inherently, WPU coatings have reduced stiffness and mechanical strength that can be increased by the addition of nanoparticles, like Ag, Cu, TiO₂, SiO₂ and many more. Fire retardants, commonly phosphorous, are incorporated in the WPU structure to increase the flame retardancy of WPU coatings.     

Thermal Stability and Flame Retardancy of Rigid Polyurethane Foams/Organoclay Nanocomposites

The thermal stability and flame retardancy of a new kind of rigid polyurethane (PU) foams/organoclay nanocomposites developed by our research group were investigated by using thermogravimetry analysis (TGA) and cone calorimeter test. Results indicate that compared with pure PU foams, rigid PU foams/organoclay composites show significantly enhanced thermal stability and flame retardancy. The reasons leading to the results were discussed in detail by relating with the morphology of the composites. The discussion suggests that the enhancement degree of thermal stability and flame retardancy of composites compared with that of PU foams coincides well with the sequences of gallery spacing of organoclay in the PU matrix.     

Synthesis and properties of a modified unsaturated polyester resin with phosphorus-containing pendant groups

A novel modified-unsaturated polyester resin (M-UPR) with phosphorus-containing pendant groups was successfully prepared by employing a bifunctional acid, 2-[10-(9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide-10-yl)]-maleic acid (DOPO-MA) as monomer. Characterization of DOPO-MA and M-UPR was performed using element analysis, ¹H-NMR, or FT-IR. The curing of M-UPR was measured by differential scanning calorimetry, and the optimal cure temperature was calculated with DSC curves at different heating rates. The thermal stability was investigated with thermogravimetric analysis and comparative FT-IR analysis for char residue before and after heating. The flame-retardant property was determined by limiting oxygen index measurements and UL94 flammability meter. The viscoelastic property was measured with dynamic mechanical analysis. Owing to the incorporation of the rigid structure of pendant phosphorus groups, both thermal stability and flame retardancy of the resultant M-UPR have been improved.     

Polylactic acid flame-retardant composite preparation and investigation of flame-retardant characteristics

Polylactic acid (PLA) is a new type of biodegradable material with good mechanical properties, and is widely used in many fields. However, as PLA is highly flammable, it is necessary to conduct flame-retardant modification research on PLA. Phosphorus heterophilic flame retardants are low smoke, non-toxic and have high flame-retardant efficiency, and also have broad application prospects. In this study, a phosphazene flame retardant, 9,10-dihydro-9-oxa-10-phosphazene-10-yl-hydroxy-phenol (abbreviated as DOPO-PHBA), was synthesized. The PLA/ECE/DOPO-PHBA flame-retardant composites were prepared by adding DOPO-PHBA and epoxy chain extender (ECE) into PLA. Thermal, mechanical, and flame-retardant properties, as well as microscopic morphology of the PLA flame-retardant composites were characterized and analyzed, and the flame-retardant mechanism was discussed. Results show that when the flame-retardant DOPO-PHBA is added at 5 wt%, the PLA composites can reach the V-0 level of combustion, and the corresponding LOI value is 30.0% at this time, and the LOI value increases from 22.5% to 33.6% with the increase of the flame-retardant content. In addition, PLA composites still have good mechanical properties, and the cone heat, carbon residue and the thermal decomposition process shows that the flame-retardant causes a two-phase flame-retardant mechanism on PLA with the gas and condensed phases acting in synergy. High flame retardancy is mainly attributed to free radical quenching, gas dilution, and the thermal barrier caused by the carbon layer. This work provides a simple and scalable method for the preparation of high-performance flame-retardant PLA materials.