Improving the flame retardancy of PET fabric by photo-induced grafting

Photo-induced surface grafting with glycidyl methacrylate (GMA) as monomer in association with a pad-curing treatment by using a flame retardant (FR) solution which contains 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP) and sulfamic acid (H₂NSO₃H) has been used to improve the fire performance of PET fabric in this study. The effects of initiator concentration, monomer concentration and the irradiation time on the grafting percentage were investigated. The chemical structure of grafted surface of the PET fabric was characterized by an attenuated total reflection-infrared (ATR-IR) spectroscopy. The fire performance was evaluated by the LOI and the vertical flammability tests, and the results indicate that the photo grafting treatment could improve the flame retardancy and dripping resistance of PET fabric. Thermal behaviour of treated PET fabric samples was investigated by thermogravimetric (TG) and differential scanning calorimetric (DSC). The morphology of the sample char residue was also investigated by scanning electron microscope (SEM).     

Combination effect of nanoparticles with flame retardants on the flammability of nanocomposites

Polystyrene based nanocomposites (PNCs) with and without flame retardant additives were successfully prepared through a single-screw extrusion technique. The combination effect of nanoparticles and flame retardants was investigated with nanosilica and attapulgite clay as nanofillers, and with a NASA formulated SINK flame retardant. A comprehensive study was done by Cone Calorimetry, UL94 and TGA.The addition of nanoparticles to polystyrene generally improved the OI of polystyrene. The horizontal burning tests suggested that nanofiller types have different impacts on the flammability of nanocomposites. According to the vertical burning tests and oxygen indices, it was found that polystyrene/silica and polystyrene/attapulgite clay PNCs alone are not flame retardant. In fact, the materials burned faster. However, the combination of nanocomposites with the SINK flame retardant significantly altered the thermal stability, and flammability of the materials. A remarkable reduction in heat release rates of polystyrene was achieved for both silica and attapulgite with flame retardant nanocomposites. For instance, the introduction of 20% SINK into PS reduced the PHRR of PS from 1212 to 838 (−31%); 10% silica reduced it from 1212 to 1060 (−13%), while the combination of silica and SINK reduced it to 530 (−56%), which clearly shows interaction between nanosilica and SINK.     

Bio-waste derived,phosphorus decorated composite for highly efficient flame retardant for cotton fabric

In this, an efficient flame retardant composite has been prepared using biowaste derived phosphorous groups decorated graphene supported nanomaterial. The eggshell was utilized as a source of calcium carbonate, which was converted to monocalcium phosphate (CP) by phosphoric acid treatment. As-prepared monocalcium phosphate was functionalized with graphene to prepare graphene functionalized monocalcium phosphate (GCP). The GCP-coated fabric didn't ignite during the flame test and sustained more than 600 s on continuous exposure to flame without changing its initial length and shape. Whereas, graphene oxide (GO), and CP coated cotton fabric burnt out very easily within a short time. The efficient flame retardant property of as synthesized GCP coated cotton fabric was confirmed with a high limiting oxygen index (34.1) and char length of 2.5 cm was generated from the VFT test. The synthesized GCP coated cotton fabric also confirmed efficient flame retardant properties. This facile method enables an easy process for mass production of cost-effective, bio-waste derived nanomaterial for a significantly highly efficient candidate for different applications in sustainable chemistry, including flame-retardant applications.

Graphical abstract

     

The anti-dripping intumescent flame retardant finishing for nylon-6,6 fabric

Nylon-6,6 fabric has been widely used in military and civilian area for many years. However, the melting drip problem has not been effectively solved despite the efforts made in the last two decades. An intumescent flame retardant system, containing ammonium polyphosphate, melamine and pentaerythritol, has been proved to be effective on preventing melting drip during burning of nylon-6,6 fabric in this study. The LOI and the vertical flammability test indicate that this IFR (intumescent flame retardant) system could improve the flame retardancy and impart dripping resistance to nylon-6,6 fabric. Thermal behaviour of nylon-6,6 fabric treated with IFR system was investigated by thermogravimetric (TG) and differential scanning calorimetric(DSC) experiments. The results indicate that char residue of treated samples are above 13%, and the highest value could reach up to 24% at 750 °C which is much higher than that of the untreated fabric. SEM graphs of residue of treated and untreated nylon-6,6 fabric show that IFR could promote formation of residual char which impart anti-dripping property to nylon-6,6 fabric. The tensile property test shows that tensile strength of treated fabric decreased.     

Formaldehyde-free flame retardant finishing of silk using a hydroxyl-functional organophosphorus oligomer

Flame retardancy is a desirable property for silk textiles, and it becomes necessity when silk textiles are for interior decorative use in building with public access. However, the flame retardant finishing technology available for silk has significant limitations. In this research, we studied the use of the combination of a hydroxyl-functional organophosphorus oligomer (HFPO) and 1,2,3,4-butanetetracarboxylic acid (BTCA) as a formaldehyde-free flame retardant finishing system for silk. When BTCA is applied to silk, most of BTCA reacts with the hydroxyl group on silk by single ester linkage. In the presence of HFPO, BTCA is able to bond HFPO onto silk by either a BTCA “bridge” between silk and HFPO or a BTCA-HFPO-BTCA cross-linkage between two silk protein molecules. We evaluated the flammability and physical properties of the silk fabric treated with HFPO and BTCA. The treated silk fabric demonstrated a high level of flame retardancy with modest loss in fabric tensile strength. The treated silk passed the vertical flammability test after 15 hand wash (HW) cycles. Increasing the HFPO concentration from 20% to 30% does not show significant improvement in the flame retardant performance of the treated silk. The thermal analysis data demonstrated that HFPO reduces silk's initial thermal decomposition temperature and promotes char formation.     

A New Nano‐Structured Flame‐Retardant Poly(ethylene terephthalate)

A modified nano‐hydrotalcite was used as inorganic flame‐retardant fillers for poly(ethylene terephthalate) (PET) polymers. A flame‐retardant compound was obtained from layered hydrotalcite (LDH) dispersed in brominated polystyrene (PBS) solution and then solvent evaporation from the dissolved PBS samples. The compound of PBS/LDH was characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) and was found to have high aspect ratio LDH dispersed in the PBS matrix. Flame‐retardant PET composite was prepared by melt‐compounding the flame‐retardant compound of PBS/LDH and PET. Improvement in the fire retardancy of the nano‐flame‐retardant PET composite obtained was found by measuring the oxygen index. The nanostructure of flame‐retardant PET composite was chirecterized by scanning electron microscopy (SEM) of flame‐retardant PET composite. The mechanical properties of the flame‐retardant PET nano‐composite were also characterized.     

Applications of micro-scale combustion calorimetry to the studies of cotton and nylon fabrics treated with organophosphorus flame retardants

Effective testing methods are critical for developing new flame retardant textiles by the industry. However, the current testing methods all have limitations. In this research, we applied micro-scale combustion calorimetry (MCC) for evaluating the flammability of the cotton woven fabric treated with a traditional reactive organophosphorus flame retardant in combination with a synergistic nitrogen-containing additive and the nylon-6,6 woven fabric treated with a hydroxyl-functional organophosphorus oligomer and crosslinkers. We found that MCC is capable of differentiating small differences among the treated fabric samples with similar flammability. MCC is able to make quantitative measurement of the peak heat release rate, the most important parameter related to fire hazard of materials, of textile whereas such analysis is more difficult using cone calorimetry due to textile fabrics’ low thickness. By using the thermal combustion parameters measured by MCC, we were able to calculate the limiting oxygen index (LOI) of various treated cotton fabric samples with near-perfect agreement between the experimentally measured and the predicted LOI values of treated cotton fabrics. We also compared the capability of MCC and differential scanning calorimetry for analyzing flame retardant cotton textiles.     

An improved method for the durability of the flame retardant PA66 fabric

This paper describes an attempt in order to improve the durability of the flame retardant polyamide 66 (PA66) fabric prepared by the reaction of surface photografting with acrylamide (AM) under UV irradiation. In this study, N,N′-methylene bisacrylamide (MBAAm) combined with acrylamide has been used as a photosensitive monomer during flame retardant finishing of the PA66 fabric sample. “Durable efficiency” has been introduced to evaluate the durability of AM/MBAAm-g-PA66 fabric after 50 times washing with the 0.5 % commercial grade detergent solution. The result indicates that durable efficiency reaches its maximal value of 94.5 % when the MBAAm concentration is 5.0 mass%. The effect of MBAAm on the flame retardancy, thermal stability and tensile properties of the treated PA66 fabric has been investigated, respectively. And an interesting phenomenon shows that although MBAAm could improve the thermal stability of the treated fabric significantly at high temperature, it could have a negative effect on the flame retardancy and tensile properties of the fabric sample when its concentration is high. Its possible mechanism has been discussed here.     

Synthesis and characterization of a novel phosphorus–nitrogen‐containing flame retardant and its application for textile

The economic and environmentally friendly flame‐retardant compound, tetramethyl (6‐chloro‐1,3,5‐triazine‐2,4‐diyl)bis(oxy)bis(methylene) diphosphonate ( CN‐1 ), was synthesized by a simple two‐step procedure from dimethyl phosphate, and its chemical structure was characterized by ¹H, ¹³C, and ³¹P nuclear magnetic resonance and gas chromatography mass spectroscopy. Using the traditional pad–dry–cure method, we obtained several different add‐ons (wt%) by treating cotton twill fabric with flame retardant ( CN‐1 ). Thermogravimetric analysis, in an air and nitrogen atmosphere, of the modified cotton showed that decomposition occurred ~230°C with 16% residue weight char yield at 600°C, indicating high thermal stability for all treated levels. Limiting oxygen index (LOI) and the vertical flammability test were employed to determine the effectiveness of the flame‐retardant treatments on the fabrics. LOI values increased from ~18 vol% oxygen in nitrogen for untreated fabric to maximum of 34 vol% for the highest treatment level. Fabrics with higher levels of flame retardant also easily passed the vertical flammability test. Furthermore, Fourier transform infrared and scanning electron microscopy were utilized to characterize the chemical structure as well as the surface morphology of the flame‐retardant treated twill fabrics, including char area and the edge between unburned fabric and char area. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation of a novel phosphorus‐containing organosilicon and its effect on the flame retardant and smoke suppression of polyethylene terephthalate

A novel phosphorus‐containing silicone flame retardant (PDPSI) was prepared by Mannish reaction, and a series of PDPSI/PET composites were prepared by melt blending method. The nuclear magnetic resonance (¹H NMR), Fourier transformation infrared (FTIR), and the thermogravimetric analyzer (TGA) results indicated that PDPSI showed network structure and owned good thermal stability, with the char residue of 62.2% at 800°C. The flame retardancy of PDPSI/PET composites was characterized by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter (CCT). The results revealed that the addition amount of PDPSI was 5%, the LOI value of PDPSI/PET composites increased to 27.3%, and UL‐94 test passed V‐0 rating. When the PDPSI loading was 3%, PET composites showed excellent flame retardancy and smoke suppression, with a decrease in the peak heat release rate (PHRR) by 71.19% and the total smoke release (TSP) reduced from 14.4 to 11.1m². The scanning electron microscopy (SEM) and FTIR results of char residue demonstrated that the flame‐retardant mechanism of PDPSI was solid phase flame retardant. PDPSI catalyzed the aromatization reaction of PET to promote the formation of a dense and continuous carbon layer, finally improving the flame retardancy and smoke suppression properties of PET.     

表面化学接枝改性阻燃棉织物的制备与性能

采用高碘酸钠对棉织物表面进行选择性氧化生成醛基,选取乙二胺与醛基反应,通过膦氢化加成反应将阻燃剂亚磷酸二甲酯接枝到棉织物表面,最后通过三羟甲基三聚氰胺对棉织物表面进行接枝改性,制备了含三羟甲基三聚氰胺/乙二胺/亚磷酸二甲酯阻燃棉织物.通过傅里叶红外光谱（FTIR）对改性后棉织物的结构进行了表征,通过极限氧指数（LOI）测试研究了其阻燃性能,通过锥形量热测试研究了其燃烧行为,通过在40℃皂水中洗涤10次考察了其耐水性能,通过扫描电子显微镜测试了其表面及燃烧后炭层的形貌.研究结果表明,经表面改性后,棉织物的LOI值由（19.5±1.0）%提高到了（43.1±1.0）%,经耐水洗测试后,LOI值仅下降至（42.6±1.0）%,保持了非常好的阻燃性能,表明通过表面接枝方法制备的三羟甲基三聚氰胺/乙二胺/亚磷酸二甲酯阻燃棉织物具有非常好的耐水洗性能.表面阻燃改性提高了棉织物在燃烧过程中的成炭性能,形成的连续膨胀的炭层较好地保护了内部织物,抑制了织物的降解和燃烧,从而提高了棉织物的阻燃性能.     

Comparison of different reactive organophosphorus flame retardant agents for cotton. Part II: Fabric flame resistant performance and physical properties

N-Methylol dimethylphosphonopropionamide (MDPA) is one of the most commonly used durable flame retardant agents for cotton. In our previous research, we developed a new flame retardant finishing system based on a hydroxy-functional organophosphorus oligomer (HFPO) and bonding agents, such as dimethyloldihydroxyethyleneurea (DMDHEU) and trimethylolmelamine (TMM). In this research, we compared the flame resistant performance as well as physical properties of the cotton fabric treated with these two flame retardant finishing systems. The cotton fabric treated with MDPA/TMM has a higher initial limiting oxygen index (LOI) than that of the fabric treated with HFPO/TMM due to higher nitrogen content in the system. The LOI of the cotton fabric treated with the HFPO and MDPA systems becomes identical when the treated fabric contains equal amount of phosphorus and nitrogen. The MDPA/TMM shows higher laundering durability on cotton than HFPO/TMM system. The fabric treated with HFPO/TMM and MDPA/TMM has low wrinkle resistance and low strength loss whereas the fabric stiffness significantly increases when the TMM concentration is increased.     

Growth and fire resistance of colloidal silica-polyelectrolyte thin film assemblies

Thin films of colloidal silica were deposited on cotton fibers via layer-by-layer (LbL) assembly in an effort to reduce the flammability of cotton fabric. Negatively charged silica nanoparticles of two different sizes (8 and 27 nm) were paired with either positively charged silica (12 nm) or cationic polyethylenimine (PEI). PEI/silica films were thicker due to better (more uniform) deposition of silica particles that contributed to more than 90% of the film weight. Each coating was evaluated at 10 and 20 bilayers (BL). All coated fabrics retained their weave structure after being exposed to a vertical flame test, while uncoated cotton was completely destroyed. Micro combustion calorimetry confirmed that coated fabrics exhibited a reduced peak heat release rate, by as much as 20% relative to the uncoated control. The 10 BL PEI-8 nm silica recipe was the most effective because the coating is relatively thick and uniform relative to the other systems. Soaking cotton in basic water (pH 10) prior to deposition resulted in better assembly adhesion and flame-retardant behavior. These results demonstrate that LbL assembly is a useful technique for imparting flame retardant properties through conformal coating of complex substrates like cotton fabric.     

Permanent flame retardant finishing of textile materials by a photochemical immobilization of vinyl phosphonic acid

A new photochemical method for a permanent flame retardant finishing of textiles made of cotton (CO), polyamide (PA) and polyester (PET) is described. Using a mercury vapour UV lamp vinyl phosphonic acid (VPA) can be fixed durable to different fabrics made of CO, PA and PET in the presence of a cross-linking agent and a photo-initiator. After a home laundering cycle up to 50 wt% of the reaction mixture is retained on the fabrics and the absolute phosphorus content was found to be more than 2.0% in all investigated cases. The photochemically modified textiles showed high levels of flame retardant performance and passed a vertical flammability test for protective clothing.     

Thermal properties of cotton fabric modified with poly (propylene imine) dendrimers

For the first time, thermal stability and flame retardant properties of cotton fabrics modified with poly (propylene imine) dendrimer (PPI-dendrimer) using cross linking agents have been reported. The PPI-dendrimers can be considered as novel nitrogen flame retardant agents, because they contain a large number of nitrogen-containing groups (amine end groups), which may release nitrogen gas or ammonia. In this paper, the effect of the PPI-dendrimers on thermal behavior of cotton fabric is investigated through thermogravimetric analysis, differential scanning calorimetry, flammability (in vertical configuration) and limiting oxygen index tests. Indeed, both thermal stability and flame retarancy of the modified fabrics have significantly enhanced. Furthermore, field emission scanning electron microscopy micrographs have been studied in order to evaluate morphology of the cotton samples. Crystallinity and physical properties including crease recovery angle, breaking strength, whiteness index and hygroscopicity of the samples have been also assessed.     

用DSC研究阻燃PET的结晶性和结晶动力学

<正> 聚对苯二甲酸乙二酯(PET)是一种熔点较高的结晶性聚合物,其结晶性和结晶动力学已得到了广泛的研究。我们最近合成的一种含磷聚合物(或齐聚物)聚苯基磷酸二苯砜酯(PSPPP),可作为PET纺丝较为理想的阻燃剂。当PET中添加5wt％的这种阻燃剂时,其极限氧指数可达到30。然而,有关这种阻燃剂的加入对PET结晶特性的影响方面的研究鲜见报道。本文用DSC方法研究了阻燃剂添加量的多少对PET结晶程度的影响,并且对纺制阻燃PET纤维的实用添加量5wt％的试样进行了结晶动力学研究。     

The Effect of Glass Fibre and a Phosphorus-Containing Flame Retardant on the Flammability of Recycled PET

The availability of scrap poly(ethylene terephthalate) (PET) from post-consumer bottles is increasing as the post-consumer collecting systems are becoming more usual in daily life. PET is well known as a high-performance engineering thermoplastic because of its good thermal stability, chemical resistance, and excellent mechanical properties. Many efforts have been carried out to use this material in housings of electronic applications. However, the flammability of PET is a shortcoming in some of these applications. In this study, our attempt is to incorporate a non-halogenated flame retardant, in form of a phosphorus-containing compound, together with a commercial glass fibre grade to achieve UL94 test V-0 rating for PET. An investigation of thermal stability and flammability (HDT, UL94 V-test) and mechanical (tensile, flexural and impact tests) properties of glass fibre filled PET samples is reported as a function of fraction of flame retardant. This work shows the influence of the filler content and the interfacial filler/matrix adhesion on the flame retardant and the mechanical properties.     

Immobilization of flame retardant onto silica nanoparticle surface and properties of epoxy resin filled with the flame retardant‐immobilized silica

To prepare silica nanoparticle having flame retardant activity, the immobilization of flame retardant onto hyperbranched poly(amidoamine) (PAMAM)‐grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent‐free dry‐system using PAMAM dendrimer synthesis methodology. The immobilization of bromine flame retardant, poly(2,2′,6,6′‐tetrabromobisphenol‐A) diglycidyl ether (PTBBA), was successfully achieved by the reaction of terminal amino groups of PAMAM‐grafted silica (Silica‐PAMAM) with epoxy groups of PTBBA. The immobilization of PTBBA was confirmed by FTIR and thermal decomposition GC‐MS. The amount of PTBBA immobilized onto Silica‐PAMAM was determined to be 60 wt %. PTBBA‐immobilized Silica‐PAMAM (Silica‐PAMAM‐PTBBA) was dispersed uniformly in a epoxy resin, and the epoxy resin was cured in the presence of hexamethylenediamine. Flame retardant activity of the epoxy resin filled with Silica‐PAMAM‐PTBBA was estimated by limiting oxygen index (LOI). The LOI of epoxy resin filled with Silica‐PAMAM‐PTBBA was higher than that filled with untreated silica and free PTBBA. It was confirmed that the flame retardant activity of epoxy resin was improved by the addition of the Silica‐PAMAM‐PTBBA. The elimination of PTBBA from the epoxy resin filled with Silica‐PAMAM‐PTBBA into boiling water was hardly observed by immobilization of PTBBA onto silica surface. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6145–6152, 2009     

An amino trimethylene phosphonic acid-based chelated boric acid complex that works as a synergistic flame retardant for enhancing the flame retardancy of cotton fabrics

The chelating ligands of boric acid and amino trimethyl phosphonate prepared a novel flame retardant (BAP) for the cotton fabric. A stable chemical and coordination bond was formed on the surface of the cotton fibers by a simple three-curing finishing process to make the fabric exhibits excellent durable flame retardancy. Cotton fabrics' tensile strength and whiteness got substantially retained after BAP treatment. 90 g/L BAP-treated samples (3 curing times, 50 laundry cycles) showed good flame retardancy and durability, holding the largest limit oxygen index, 29.7%, and the shortest damage length, 61 mm. A condensed phase and gas phase synergistic flame retardant mechanism was concluded by thermogravimetric, cone calorimeter tests, and thermogravimetric infrared analysis.     

Flame-retardant Coating by Alternate Assembly of Poly（vinylphosphonic acid） and Polyethylenimine for Ramie Fabrics

A novel intumescent flame retardant coating,consisting of poly(vinylphosphonic acid)(PVPA) as the acid source and branched polyethylenimine(BPEI) as the blowing agent,was constructed on the surface of ramie fabrics by alternate assembly to remarkably improve the flame retardancy of ramie.The PVPA/BPEI coating on the surface of individual fibers of ramie fabric pyrolyzes to form protective char layer upon heating/burning and improves the flame retardancy of ramie.Thermogravimetric analysis reveals that the PVPA/BPEI-coated ramie fabrics left as much as 25.8 wt% residue at 600 °C,while the control(uncoated) fabric left less than 1.4 wt% residue.Vertical flame test shows that all PVPA/BPEI-coated fabrics have shorter after-flame time,and the residues well preserved the original weave structure and fiber morphology,whereas,the uncoated fabric left only ashes.Microscale combustion calorimetry shows that the PVPA/BPEI coatings greatly reduce the total heat release by as much as 66% and the heat release capacity by 76%,relative to those of the uncoated fabric.