UV Curable Flame Retardant Research Articles

Preparation and Characterisation of UV-Curable Flame Retardant Wood Coating Containing a Phosphorus Acrylate Monomer

The application of a flame retardant coating is an effective solution to enhance the fire retardancy of wood flooring. However, finding the right balance between reducing the flame propagation and good overall coating properties while conserving wood appearance is complex. In order to answer this complex problem, transparent ultraviolet (UV)-curable flame retardant wood coatings were prepared from an acrylate oligomer, an acrylate monomer, and the addition of the tri(acryloyloxyethyl) phosphate (TAEP), a phosphorus-based monomer, at different concentrations in the formulation. The coatings’ photopolymerisation, optical transparency, hardness, water sorption and thermal stability were assessed. The fire behaviour and the adhesion of the coatings applied on the yellow birch panels were evaluated, respectively, using the cone calorimeter and pull-off tests. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses were performed on the collected burnt residues to obtain a better understanding of the flame retardancy mechanism. Our study reveals that phosphorus monomer addition improved the coating adhesion and the fire performance of the coated wood without impacting the photopolymerisation. The conversion percentage remained close to 70% with the TAEP addition. The pull-off strength reached 1.12 MPa for the coating with the highest P-monomer content, a value significantly different from the non-flame retarded coating. For the same coating formulation, the peak of heat release rate decreased by 13% and the mass percentage of the residues increased by 37% compared to the reference. However, the flame-retarded coatings displayed a higher hygroscopy. The action in the condensed phase of the phosphorus flame retardant is highlighted in this study.

Preparation and flame retardancy of castor oil based UV-cured flame retardant coating containing P/Si/S on wood surface

In this paper, a multifunctional castor oil based bio-mercaptan (abbrev. COSH) was synthesized by esterification between castor oil (abbrev. CO) and 3-mercaptopropionic acid (MPA). In addition, [(6-Oxido-6H-dibenz [c,e][1,2] oxaphosphorin-6-yl) methyl] butanedioic acid (DDP) and allyl glycidyl ether (AGE) were used to synthesize the organic phosphorus flame retardant containing a double bond of allyl ether DDP-AGE (abbrev. DA) via a ring-opening reaction. The synergistic flame-retardant UV-cured coating containing phosphorus (P), silicon (Si) and sulfur (S) was prepared on wood surface with varying molar content of COSH, DA and 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (TTC) via the thiol-ene click reaction. The results show that when the molar ratio of COSH, DA and TTC is 5: 3: 3, the UV-cured coated wood samples pass the vertical UL-94 V-0 rating; the limiting oxygen index (LOI) value can reach 27.52%; the second peak of heat release rate (P2HRR) and the second smoke production rate peak (P2SPR) of the coated wood samples can be effectively suppressed, while the total heat release (THR) of 16.99 MJ/m2 is much lower than other samples and the total smoke production (TSP) is equivalent to that of uncoated wood sample; the final char residue rate can reach 14.41% during the cone calorimetry (CONE) tests. Moreover, the thermogravimetric analysis (TGA) demonstrates that COSH promotes the degradation of films at a lower temperature, while it reduces the maximum degradation rate and delays the decomposition process simultaneously. Besides, the scanning electron microscope (SEM) shows that the coated wood internal tracheid basic skeleton remains basically intact and the char layer tends to exhibit a more compact morphology after the CONE tests if the wood is coated following the molar ratio of COSH, DA and TTC of 5: 3: 3. Energy dispersive spectrometer (EDS) was used to compare the content of C, O, N, P, Si and S of the char layers formed by the coatings on the surface of coated wood samples after CONE tests, which addresses the synergistic flame retardance of P, S and P, Si.

Study on degradation of phosphorus and nitrogen composite UV-cured flame retardant coating on wood surface

A novel wood flame retardant coating has been obtained using acrylate oligomers and functional monomers containing elements phosphorus, nitrogen and sulfur as raw materials and applied on the wood surface based on thiol-ene click reaction. The UL-94, limiting oxygen index (LOI) test and thermal gravimetric analysis/infrared spectroscopy (TGA-FTIR) were used to examine the flammability and pyrolysis property of the coatings, respectively. The experimental data showed that the coating has better fire resistance on wood surface when the molar ratio of phosphorus and nitrogen monomer was 2: 4. The volatile products generated in the degradation processes of the coating were confirmed by TGA-FTIR, which are carboxylic acid, ammonia (NH3), carbon dioxide (CO2) and acid anhydride, with a temperature of maximum release rate corresponds to 99.80 °C, 170.96 °C, 346.75 °C and 358.80 °C, respectively. In addition, the coating released NH3 and CO2 as nonflammable gases during the degradation process, which diluted the oxygen concentration during combustion and was favorable to generate the intumescent char layer. The TGA curves of the coating showed three degradation, corresponding to the water loss and the C–S bond breaking of crosslinking networks, the degradation of phosphate and acrylates, the decomposition of unstable char layers, the main chain in poly N, N-dimethylacrylamide (PDMAA) and the formation of poly (phosphoricacid), respectively. The char yield of the coating reaches to 27.16% at 600 °C under nitrogen atmosphere, showing excellent flame retardant properties.

Flame retardancy and thermal property of novel UV-curable epoxy acrylate coatings modified by melamine-based hyperbranched polyphosphonate acrylate

A novel melamine-based hyperbranched polyphosphonate acrylate (MHPA), successfully synthesized via the Michael addition polymerization of 2-(2-amino-ethylamino)-4,6-bisethylamino-1,3,5-triazine with tri(acryloyloxyethyl) phosphate, was blended with the epoxy acrylate (EA) to prepare UV-cured flame retardant coatings. The study of their flammability revealed that MHPA can improve the flame retardancy and the sample with 45wt% MHPA (EA3) showed a good intumescent behavior when combusted. The results of their thermal degradation displayed that MHPA had a dual effect on the thermal stability of EA: leading to its earlier degradation catalyzed by acidic species from the relatively weak phosphorus-bearing parts, but improving the thermal stability of the char layer at high temperature due to the formed intumescent phosphorus–carbon compounds. Besides, the total release amount of gas products of EA3 was much lower than that of pure EA and various flammable gases like hydrocarbons and highly toxic CO were also reduced

Flame retardancy and thermal properties of novel UV-curing epoxy acrylate coatings modified by phosphorus-containing hyperbranched macromonomer

A novel phosphorus-containing hyperbranched macromonomer (PHM), successfully synthesized via Michael addition polymerization of tri(acryloyloxyethyl) phosphate (TAEP) with n-butylamine (BA), was blended with epoxy acrylate resin (EA) to prepare UV curable flame retardant coatings. The study of thermal degradation of these coatings revealed that PHM can catalyze the degradation of EA, contributing to the formation of thermally stable char layer. The residues of EA3 (which contains 45 wt.% PHM) at various temperatures were analyzed by X-ray photoelectron spectroscopy (XPS) and the results displayed that the formation of phosphorus-carbon structure can well protect the carbonaceous char from thermal-oxidative degradation at 800 °C. Besides, the investigation of the flammability illustrated that the addition of PHM increased the limiting oxygen index (LOI) value and reduced the peak heat rate release (HRR) and total heat release (THR).

Functionalization of Cotton with UV-Cured Flame Retardant Coatings

A novel phosphorus monomer (PDHA) was synthesized and incorporated onto the surface of cotton fabric via UV-induced graft polymerization to improve flame retardancy and thermal stability. The structure of PDHA was characterized by 1H nuclear magnetic resonance (1H NMR), 31P NMR, and Fourier transform infrared spectra (FTIR) and the grafting processes were followed by IR (ATR) spectroscopy and scanning electron microscopy (SEM). The thermal stability and flame retardancy of the treated fabrics were studied by thermogravimetric analysis (TGA), thermogravimetric analysis/infrared spectrometry (TGA-IR), and microscale combustion colorimeter (MCC). Test performed on real time FTIR analysis for treated cotton showed that the coatings containing phosphorus could catalyze the dehydration and char formation of cotton textiles at a lower temperature. The enhanced flame retardant action may be caused by the thermal decomposition of phosphate acrylate producing acidic intermediates, which could react with fabrics to ...

Flame retardancy and thermal degradation of cotton textiles based on UV-curable flame retardant coatings

The flame retardant coatings were prepared through UV-curable technique using tri(acryloyloxyethyl) phosphate (TAEP) and triglycidyl isocyanurate acrylate (TGICA). Results from FTIR-ATR spectroscopy and scanning electron microscopy (SEM) showed that flame retardant coatings were successfully coated onto the surface of cotton fabrics. The flame retardancy of the treated fabrics was studied by Micro-scale Combustion Calorimeter (MCC) and limited oxygen index (LOI). The cottons coated flame retardant coatings had the lower peak heat release rate (PHRR), heat release capacity (HRC), total heat of combustion (THC) and higher LOI value compared with untreated cotton. The results from TGA test showed that the flame retardant coatings lowered the decomposition temperature of treated fabric. The thermal decomposition of cottons was monitored by real time FTIR analysis and thermogravimetric analysis/infrared spectrometry (TGA-IR). The enhanced flame retardant action might be caused by thermal decomposition of TAEP structure, producing acidic intermediates, which could react with fabrics to alter its thermal decomposition process.

Combustion and Thermal Behavior of Polyurethane Acrylate Modified with a Phosphorus Monomer

A series of UV curable flame retardant resins were obtained by blending bis(2-acryloxyethyl) 2.6.7-trioxa-1-phosphabicyclo[2.2.2.]octane-4-methylol-1-oxide phosphate (MDMPE) in certain ratios with a commercial polyurethane acrylate (PUA). It has been found that the cured film shows good flame retardancy when the MDMPE is at 30% additive level. The cone calorimeter results show that the heat release rate decreases in comparison with the pure PUA. The thermogravimetric analysis (TGA) and real time Fourier-transform infrared spectroscopy measurements (RTFTIR) results show that the phosphate group in MDMPE first degrades to form poly(phosphoric acid) before the degradation of PUA. Then, the formed poly(phosphoric acid) effectively promotes the conversion of PUA to form char, which prevents the sample from further burning. It can be concluded that MDMPE could catalyze the degradation of PUA to form char residue, and could be used as a UV curable flame retardant which acts by a condensed phase mechanism.

Synthesis and properties of a novel hyperbranched polyphosphate acrylate applied to UV curable flame retardant coatings

A series of hyperbranched polyphosphate acrylates (HPPAs) being used for UV curable flame retardant coatings were prepared by the reaction of tri(acryloyloxyethyl) phosphate (TAEP) with piperazine at given ratios, and characterized using FTIR, 1H NMR and GPC measurements. HPPA was blended with TAEP in different ratios to obtain a series of UV curable resins. Their maximum photopolymerization rates ( R P max ) and final unsaturation conversion ( P f) in the cured films at the presence of a photofragmenting initiator were investigated. The results showed that the P f increased along with HPPA content and the pure HPPA has the maximum value of 82.1% in the photo-DSC analysis. The data from dynamic mechanical thermal analysis showed that HPPA has good miscibility with TAEP. The crosslinking density and T g of the cured film decrease along with the content of HPPA in the blend. The mechanical properties of the cured films were also investigated. Less than 20% HPPA addition improved both the tensile strength and elongation at break without damaging the modulus. The HPPA 20TAEP 80 film with 20% HPPA addition has the highest tensile strength of 31.7 MPa and an elongation at break two times that of cured TAEP. The flame retardancy of the UV cured films was investigated by the limiting oxygen index (LOI). The cured TAEP/HPPA samples greatly expanded when burning, and the degree of expansion increased along with HPPA content. However, the LOI values decreased from 47.0 to 34.0 along with HPPA content, which can be ascribed to that the flame retardancy of TAEP is mainly acting in the gas phase, whereas HPPA mainly acting in condensed phase, and the gas phase mechanism holds the dominant effect while their blends are burning.

Synthesis and properties of poly(bisphenol A acryloxyethyl phosphate) as a UV curable flame retardant oligomer

Poly(bisphenol A acryloxyethyl phosphate) (BPAAEP) being used for UV curable flame retardant coatings and adhesives, was synthesized from phosphorus oxychloride, hydroxylethyl acrylate and bisphenol A as raw materials, and characterized using 13C NMR, 31P NMR, FTIR, MS and GPC measurements. A series of formulations with different ratios of BPAAEP to urethane acrylate, EB220, were prepared to obtain flame retardant resins. The flame retardancy of the UV cured films was investigated by the limiting oxygen index (LOI). A synergistic effect between phosphorus and nitrogen was observed when 1.5 wt% phosphorus was presented in the resin. Their maximum photopolymerization rates ( R p max ) and final unsaturation conversion ( P f) in the cured films at the presence of a 3 wt% photofragmenting initiator were investigated. The results showed that the P f increased with increasing EB220 content photo-DSC analysis. The data from dynamic mechanical thermal analysis showed that BPAAEP has good miscibility with EB220. Moreover, the crosslink density and T g of the cured film decreased along with the content of BPAAEP in the blend.

Different effects of tri(acryloyloxyethyl) phosphate on the thermal degradation of photopolymerized epoxy acrylate and polyurethane acrylate films

AbstractTri(acryloyloxyethyl) phosphate (TAEP) was blended in different ratios with epoxy acrylate EB600 and polyurethane acrylate EB270 to obtain a series of UV curable flame retardant resins. The thermal degradation mechanisms of their cured films in air were studied by thermogravimetric analysis, in situ Fourier‐transform infrared spectroscopy, and direct pyrolysis/mass spectrometry measurements. The results showed that the phosphate group in TAEP first degraded to form poly(phosphoric acid) before the degradation of EB600. Then, the formed poly(phosphoric acid) effectively promoted the conversion of EB600 to form char, which prevented the sample from further burning. However, urethane group in EB270 degraded simultaneously with phosphate group in TAEP, leading to not effectively increase the conversion of EB270 to char during the thermal degradation. It was thus found that the addition of TAEP more effectively improved the thermal stability, flame retardance, and the char yield during combustion of EB600 than those of EB270. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3130–3137, 2006

Thermal degradation and flame retardancy of a novel methacrylated phenolic melamine used for UV curable flame retardant coatings

Methacrylated phenolic melamine (MAPM) was synthesized as a flame retardant multifunctional oligomer for UV curable systems, and characterized by FTIR, 1H NMR and elemental analysis. A series of formulations was prepared based on MAPM and a commercial UV curable epoxy acrylate EB600. Their thermal behaviours were investigated by thermogravimetric analysis, indicating that MAPM had no effect on the char formation of EB600. The flammability was monitored by the limiting oxygen index (LOI); the LOI value of EB600 increased from 21.5 for pure EB600 to 26.5 for the blend containing 50% MAPM addition. The “composite bar test” result showed that the vapour phase action flame retardant mechanism was the dominant mode for MAPM. The thermal degradation mechanism of MAPM was investigated by in situ FTIR, DP–MS and elemental analysis. The results showed that MAPM first degraded to form melamine at around 300 °C, which would further undergo condensation on heating with elimination of ammonia. Nitrogen underwent about 19% conversion to the residue and 81% had vapourized below 500 °C.

Kinetics and mechanism of thermal oxidative degradation of UV cured epoxy acrylate/phosphate triacrylate blends

Tri(acryloyloxyethyl)phosphate (TAEP) was blended in different ratios with a commercial epoxy acrylate to obtain a series of UV curable flame retardant resins. The thermal oxidative degradation mechanism of their cured films in air was studied by thermogravimetric analysis and in situ Fourier-transform infrared spectroscopy. The cured film with TAEP addition showed improved thermal stability at elevated temperature with higher char yield. The kinetics of their thermal decomposition were evaluated by Kissinger, Friedman and Vachuska–Voboril methods. The results showed that the activation energies of the blends were lower than that of pure epoxy acrylate at lower degree of degradation, whereas higher activation energies were obtained at higher degree of degradation.

Combustion behaviour and thermal properties of UV cured methacrylated phosphate/epoxy acrylate blends

Methacrylated phosphates (MAPs) were blended in certain ratios with a commercial epoxy acrylate to obtain UV curable flame retardant resins. The flame retardancy and thermal properties of their UV cured films were investigated by the combustion behaviour, limiting oxygen index (LOI), thermal degradation and glass transition temperature ( T g). The results showed that the peak and average heat release rates decreased to the approximate levels of pure MAPs when 17 wt.% of MAPs was added, and no obvious effects were observed from the films with higher loading levels. The LOI increased along with the content of MAPs, and the total heat release, contrarily, decreased. The total smoke production was suppressed by MAPs addition as it leads to an effective decrease of mass loss, although MAPs have no effect on the specific extinction area. The T g decreased with increasing content of MAPs due to the reduction in rigidity of the polymer chains, and the lower cross-link density of the cured film.

Synthesis and photopolymerization of hyperbranched polyurethane acrylates applied to UV curable flame retardant coatings

Synthesis and photopolymerization of hyperbranched polyurethane acrylates applied to UV curable flame retardant coatings

Synthesis and photopolymerization of hyperbranched polyurethane acrylates applied to UV curable flame retardant coatings

AbstractA series of hyperbranched polyurethane acrylates containing phosphorus were prepared by reaction of a phosphorus‐containing triol with toluene‐2,4‐diisocyanate and hydroxylethyl acrylate at given ratios. The resins obtained were found to polymerize rapidly in the presence of a photofragmenting initiator under UV irradiation, and the maximum polymerization rate increased with temperature up to 125 °C, then decreased quickly. The UV cured films have flame retardancy with a limiting oxygen index of 27.0.© 2002 Society of Chemical Industry

Flame retardant mechanism of hyperbranched polyurethane acrylates used for UV curable flame retardant coatings

A hyperbranched polyurethane acrylate containing phosphorus was found to display flame retardance with a limiting oxygen index of 27.0 after being UV cured. The retardant mechanism was investigated by observing the site where retardance take places and the synergistic effect of phosphorus and nitrogen. It is shown that the best synergistic effect happens when the phosphorus content is around 0.7 wt.%. The thermo-degradation process was monitored by in-situ FTIR. The P–O–C bonds break more easily than C–O–C bonds, forming P–O–P bonds. The morphological characteristics of the charred crust of the product were studied by scanning electron microscopy based on comparison with that of the urethane acrylate without phosphorus. The presence of phosphorus promotes the formation of compact char, which protects the underlying polymeric materials from further attack from flame or heating.