The effect of metal ions on thermal oxidative degradation of cotton cellulose ammonium phosphate

The thermal oxidative degradation of cellulose, and of cellulose ammonium phosphate and its metal complexes products were studied by thermal analysis, infrared spectroscopy and elemental analysis. The temperature of decomposition was lower for metal complexes of cellulose ammonium phosphate than those samples untreated by metal ions and the values of char yield were greater for treated cellulose than those untreated. This indicates the metal ions can catalyze the reaction of degradation and form more char. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of nitrogen additives on flame retardant action of tributyl phosphate: Phosphorus-nitrogen synergism

The effects of three nitrogen additives (urea, guanidine carbonate, and melamine formaldehyde) on the flame retardant action of cotton cellulose treated with tributyl phosphate (TBP) were investigated in this research. The limiting oxygen index (LOI) of treated cotton cellulose clearly revealed the synergistic interactions of TBP and nitrogen compounds. The Kissinger method was used to evaluate the kinetics of thermal decomposition on treated cellulose. The results show that adding nitrogen additives increases the activation energy at a higher degree of degradation, thus indicating better thermal stability at higher temperatures. Scanning electron microscope pictures of chars formed after a LOI test show the formation of protective polymeric coatings on char surfaces. Evaluating char surfaces using attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggests that these coatings are composed of species containing phosphorus-nitrogen-oxygen. Possible chemical interactions of phosphorus and nitrogen compounds during the burning process and the formation of a protective coating could be the reason for the observed synergism. Potential reaction pathways contributing to the formation of this protective polymeric coating have also been proposed.     

Thermal decomposition and burning behavior of cellulose treated with ethyl ester phosphoramidates: Effect of alkyl substituent on nitrogen atom

This research explores the structural effect of phosphoramidates as flame retardants (FRs) for cotton cellulose. Flame retardant (FR) and thermal decomposition actions of phosphate such as triethyl phosphate (TEP), primary phosphoramidate such as diethyl phosphoramidate (DEPA) and secondary phosphoramidates such as phosphoramidic acid, N(2-hydroxy ethyl) diethylester (PAHEDE), diethyl ethyl phosphoramidate (DEEP) and diethyl 2-methoxyethylphosphoramidate (DEMEP) on cotton cellulose were investigated. Limiting oxygen index (LOI) of treated cotton cellulose showed that all phosphoramidates exhibited better flame retardant properties as compared to TEP. Secondary phosphoramidate PAHEDE had better flame retardant properties as compared to DEMEP and DEEP which indicate that flame retardancy of secondary phosphoramidates is structure related. Test performed on pyrolysis combustion flow calorimeter (PCFC) for treated cellulose showed higher reduction in heat of combustion for efficient FRs (PAHEDE, DEPA). Evolved gas analysis using thermogravimetric analyzer-Fourier transform infrared spectroscopy (TGA-FTIR) and thermogravimetric analyzer-mass spectrometer (TGA-MS) of treated cellulose showed that phosphoramidates could catalyze the dehydration and char formation of cellulose at a lower temperature. The enhanced flame retardant action of phosphoramidate may be due to the catalytic thermal decomposition of the phosphoramidate structure to produce acidic intermediates which could react with cellulose to alter its thermal decomposition.     

High resistance to thermal decomposition in brown cotton is linked to tannins and sodium content

Brown cotton fibers (SA-1 and MC-BL) studied were inferior to a white cotton fiber (Sure-Grow 747) in fiber quality, i.e., a shorter length, fewer twists, and lower crystallinity, but showed superior thermal resistance in thermogravimetric, differential thermogravimetric, and microscale combustion calorimetric (MCC) analyses. Brown cotton fibers yielded 11–23 % smaller total heat release and 20–40 % greater char. Washing fibers in water and a 1 % NaOH solution showed that rich natural inorganic components and the condensed tannins present in brown cotton are responsible for the unusual thermal property. The loss of inorganics from white cotton during a water wash increased the thermal decomposition temperature of cellulose, resulting in no char yield. However, the stronger binding of metal ions for brown cotton as well as its dominant adsorption of sodium ions after a 1 % NaOH wash facilitated the low-temperature thermal-reaction route; the sodium content showed a significant negative correlation with the heat release capacity of the fiber. Condensed tannins greatly enhanced the adsorption of sodium ions to the fiber and exhibited inherent thermal stability. The limiting oxygen indices (LOI) calculated from the MCC parameters indicated the slower burning characteristic of brown cotton, and its LOI was further increased upon adsorption of sodium ions.     

Development of an environmentally friendly halogen‐free phosphorus–nitrogen bond flame retardant for cotton fabrics

A novel flame retardant diethyl 4‐methylpiperazin‐1‐ylphosphoramidate (CN‐3) containing phosphorous and nitrogen was prepared. Its chemical structure was confirmed by nuclear magnetic resonance (¹H‐, ¹³C‐, and ³¹P‐NMR), Fourier transform infrared spectroscopy, and elemental analysis. Print cloth and twill fabrics were treated with CN‐3 to achieve different levels of add‐on (7–22 wt% add‐ons for print cloth and 3–18 wt% add‐ons for twill). Thermogravimetric analysis, vertical flame test, and limiting oxygen index (LOI) were performed on the treated cotton fabrics and showed promising results. When the treated print cloth and twill fabric samples were tested using the vertical flame test (ASTM D6413‐08), we observed that the ignited fabrics self‐extinguished and left behind a streak of char. Treated higher add‐ons fabrics were neither consumed by flame nor produced glowing ambers upon self‐extinguishing. LOI (ASTM 2863–09) was used to determine the effectiveness of the flame retardant on the treated fabrics. LOI values increased from 18 vol% oxygen in nitrogen for untreated print cloth and twill fabrics to maximum of 28 and 31 wt% for the highest add‐ons of print cloth and twill, respectively. The results from cotton fabrics treated with CN‐3 demonstrated a higher LOI value as well as a higher char yield because of the effectiveness of phosphorus and nitrogen as a flame retardant for cotton fabrics. Furthermore, FT‐IR and SEM were used to characterize the chemical structure on the treated fabrics as well as the surface morphology of char areas of treated and untreated fabrics. Published 2012. This article is a US Government work and is in the public domain in the USA.     

Investigation of the flammability of different textile fabrics using micro-scale combustion calorimetry

Evaluating and analyzing the performance of flame retardant (FR) textiles are a critical part of research and development of new FR textiles products by the industry. The testing methods currently used in the industry have significant limitations. Most analytical and testing techniques are not able to measure heat release rate (HRR), the single most important parameter in evaluating the fire hazard of materials. It is difficult to measure HRR of textile fabrics using cone calorimetry because textile fabrics are dimensionally thin samples. The recently developed micro-scale combustion calorimetry (MCC) is able to measure the following flammability parameters for textile using milligram sample sizes: heat release capacity, HRR, temperature at peak heat release rate (PHRR), total heat release and char yield. In this research, we applied MCC to evaluate the flammability of different textile fabrics including cotton, rayon, cellulose acetate, silk, nylon, polyester, polypropylene, acrylic fibers, Nomex and Kevlar. We also studied the cotton fabrics treated with different flame retardants. We found that MCC is able to differentiate small differences in flammability of textile materials treated with flame retardants. We were also be able to calculate the limiting oxygen index (LOI) using the thermal combustion properties of various textile samples measured by the MCC. The calculated LOI data have yielded good agreement with experimental LOI results. Thus, we conclude that MCC is an effective new analytical technique for measuring textile flammability and has great potentials in the research and development of new flame retardants for textiles.     

Effect of urea additive on the thermal decomposition of greige cotton nonwoven fabric treated with diammonium phosphate

This study showed that greige cotton nonwoven fabric can effectively be flame retardant by applying the phosphorus of diammonium phosphate (DAP) as low as 0.8 wt% with the addition of urea. At such a low content of phosphorus, the char length and limiting oxygen index (LOI) were continuously decreased and increased, respectively, as the concentration of urea increased. The effect of urea additive on the thermal decomposition of flame retardant greige cotton nonwoven fabric was investigated by thermogravimetry, ATR-FTIR, XRD, ¹H → ¹³C CP/MAS NMR, and SEM. The results indicated that, upon heating, urea not only facilitated the phosphorylation reaction of DAP but also introduced carbamate groups into cellulose to decrease the degree of crystallinity prior to the decomposition of the crystalline cellulose. Compared with DAP treatment alone, the addition of urea accelerated the decomposition of glycosyl units, which resulted in a slight increase of weight loss and decrease of char yield. The char morphology observed after LOI tests indicates that urea released nonflammable gases, which blew the carboneous char layer to protect the underlying substrate.     

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.     

阻燃超疏水棉纤维的制备及性能

将氢氧化镁(Mg(OH)₂)凝胶沉积到棉纤维上,以提高棉纤维表面粗糙度和阻燃性能,随后将含有Mg(OH)₂的棉纤维浸渍到聚二甲基硅氧烷(PDMS)溶液,获得阻燃超疏水棉织物。 并对棉纤维进行了傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)、疏水性、热稳定性、阻燃性能和耐久性测试。 结果表明,Mg(OH)₂负载到织物上,使得织物表面具有一定的微/纳米结构,形成了粗糙涂层。 当Mg(OH)₂浓度为1.0 mol/L时,Mg(OH)₂/PDMS改性的织物接触角(CA)可达158°,极限氧指数(LOI)提升至24.5%,导热系数为0.0525 W/(m·K), 具有超疏水和阻燃性能。 整理后织物经过20次洗涤,100次磨擦,极端条件处理后,CA仍大于150°,LOI值高于23%,显示了较好的耐久性。     

Thermal behaviour and infrared spectroscopy of cellulose carbamates

Cotton linters, swelled cotton linters and carbamated cotton linters of different nitrogen content were followed by IR spectroscopy and thermal analyses. Crystallinity indexes of the swollen and carbamated cotton linters are lower than untreated cotton linters. The decomposition temperature is lower in the case of swelled and carbamated cotton linters than untreated ones. Also the rate constant of thermal treated samples decrease by carbamation and swelling.     

Flame retardant epoxy resins based on diglycidyloxymethylphenylsilane

Silicon‐containing epoxy resins were prepared from diglycidyloxymethylphenyl silane (DGMPS) and diglycidylether of bisphenol A (DGEBA) by crosslinking with 4,4′‐diaminodiphenylmethane (DDM). Several DGMPS/DGEBA molar ratios were used to obtain materials with different silicon contents. Their thermal, dynamomechanical, and flame‐retardant properties were evaluated and related to the silicon content. The weight loss rate of the silicon‐containing resins is lower than that of the silicon free resin. Char yields under nitrogen and air atmospheres increase with the silicon content. The LOI (limited oxygen index) values increased from 24 for a standard commercial resin to 36 for silicon‐containing resins, demonstrating improved flame retardancy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5580–5587, 2006     

Physicochemical and tensile properties of alkaline-treated new natural cellulosic Gossypium arboreum fiber

This article describes the characterization of novel natural lignocellulosic bark fibers extracted from the stem of the Gossypium arboreum (cotton) plant. The G. arboreum stem fibers were treated with 5% (w/v) aqueous NaOH solution for different soaking times, and the Fourier transform infrared spectroscopy analysis was conducted to examine the chemical compounds of the raw and treated fibers. The cellulose content improved from 70.06 to 83.91% after the treatment. The X-ray diffraction results indicate that the crystalline index and size were enhanced. Thermogravimetric analysis was performed to study the thermal properties and found that the thermal stability was higher for the treated fibers. The tensile strength and modulus were increased for the alkaline-treated fibers compared to the untreated fibers.     

Chemical Graft of Cellulose with the Ion-Pair Emulsion Containing the Reactive Groups and Its Dyeing Properties

Chemical graft of cellulose with ion-pair disperse emulsion containing the reactive groups was investigated. The ion-pair disperse systems were consisted of a 1,3,5-triazine derivative containing the reactive groups, 2,4,6-tri[(2-hydroxy-3-trimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-HTAC) and 2,4,-bichloro[(6-sulfanilic acid)-1,3,5-triazine (Bi-CSAT). Compared with unmodified cellulose, the modified cotton exhibited different behavior towards dyeing. The modified cotton could be dyed with reactive dyes without the addition of salt. The color yield was higher than that on untreated cotton, despite of the addition of large amounts of salt in the latter case. Cotton fabric modified with ion-pair disperse emulsion was imparted good level dyeing properties. The dyeing rate was slower in the presence of the ion-pair compounds than that in the present of the only cationic compounds.     

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.     

A simple method for determining the total amount of physically and chemically bound water of different cements

A novel environmentally friendly flame-retardant compound, diethyl 3-(triethoxysilanepropyl) phosphoramidate (DTP) was synthesized via a simple one-step procedure with good yield and characterized by FT-IR and ¹H-NMR, ³¹P-NMR and ²⁹Si-NMR. The synthesized compound was coated onto cotton fabrics with different levels of add-ons (5–17 mass%) using the traditional pad-dry-cure method. SEM and XPS were conducted to characterize the surfaces of the coated cotton fabrics. The XPS results showed that DTP was attached to cotton through covalent bond. Cone calorimeter test showed that the cotton fabric treated with DTP became less flammable due to the lower HRR, THR and CO₂/CO ratio. The modified cotton fabrics exhibited efficient flame retardancy, which was evidenced by limiting oxygen index (LOI) and vertical flammability test. Cotton fabrics treated with DTP in 5–17 mass% add-ons had high LOI values of 23–32%. Thermogravimetric analysis results show that the usage of DTP promotes degradation of the cotton fabrics and catalyzes its char formation.     

Durable flame‐retardant finishing for polyamide 66 fabrics by surface hydroxymethylation and crosslinking

This paper describes an attempt to develop a durable finishing method in order to improve the fire performance of polyamide 66 fabrics. Hydroxymethylation with a 36% formaldehyde aqueous solution in association with a pad‐curing process to enable the fabric to react with flame‐retardant solutions was used in the finishing process. The fire performance of treated samples was characterized by limiting oxygen index (LOI) and vertical flammability tests, and the results show that the LOI value can increase from 21.6% to 46.2%. The thermal behavior of untreated and treated polyamide 66 fabrics was investigated by using thermogravimetic analysis and differential scanning calorimetry. Furthermore, residual char of treated fabric sample is much higher than that of untreated fabric sample. Fourier transform infrared spectroscopy proves that the substituted hydroxymethyl groups do exist on the molecular chain of polyamide fabric sample after surface modification. The morphology of residue char of polyamide 66 fabric samples was analyzed by scanning electron microscope, and the mechanical properties were also investigated and discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Investigation into the removal of an easy-care crosslinking agent from cotton and the subsequent regeneration of lyocell-type fibres

Dimethylol dihydroxyethylene urea (DMDHEU)-treated cotton fabrics were treated with alkali or alternatively acid followed by alkali for increasing time periods, and their effectiveness in removing the crosslinking agent was investigated by surface (X-ray photoelectron spectroscopy) analysis, bulk analysis, crease recovery angle performance and solubility in specific solvents. The cellulose yield after the chemical stripping processes was established and the effect of the acid and alkali treatments on the degree of polymerisation of the resultant cellulose determined. Surface and bulk analyses and solubility tests suggested that alkali alone could not remove the DMDHEU from the crease-resist-treated cotton fabric. However, a sequential acid/alkali treatment effectively removed the easy-care finish from the cotton fabric and produced a commercially viable yield of cellulose.     

Using a fully recyclable dicarboxylic acid for producing dispersible and thermally stable cellulose nanomaterials from different cellulosic sources

We fabricated cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) from different cellulose materials (bleached eucalyptus pulp (BEP), spruce dissolving pulp (SDP) and cotton based qualitative filter paper (QFP) using concentrated oxalic acid hydrolysis and subsequent mechanical fibrillation (for CNFs). The process was green as acid can be easily recovered, and the prepared cellulose nanomaterials were carboxylated and thermally stable. In detail, the CNC yield from the different materials was similar. After hydrolysis, the DP of the cellulose materials decreased substantially, whereas the mechanical fibrillation of the cellulosic solid residues (CSRs) did not dramatically reduce the DP of cellulose. CNCs with different aspect ratios were produced from different starting materials by oxalic acid hydrolysis. The CNCs and CNFs obtained from BEP and QFP possessed more uniform dimensions than those from SDP. On the other hand, CNFs derived from SDP presented the best suspension stability. FTIR analyses verified esterification of cellulose by oxalic acid hydrolysis. The results from both XRD and Raman spectroscopy indicated that whereas XRD crystallinity of CNCs from BEP and QFP did not change significantly, there was some change in Raman crystallinity of these samples. Raman spectra of SDP CNCs indicated that the acid hydrolysis preferably removed cellulose I portion of the samples and therefore the CNCs became cellulose II enriched. TGA revealed that the CNCs obtained from QFP exhibited higher thermal stability compared to those from BEP and SDP, and all the CNCs possessed better thermal stability than that of CNCs from sulfuric acid hydrolysis. The excellent properties of prepared cellulose nanomaterials will be conducive to their application in different fields.     

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. I. Identification of the cyclic anhydride intermediate

The mechanism of esterification of cotton cellulose by a polycarboxylic acid was investigated using Fourier transform infrared spectroscopy (FT-IR). The infrared spectroscopic data indicate that a polycarboxylic acid esterifies with cotton cellulose through the formation of an acid anhydride intermediate. A five-member cyclic anhydride intermediate was identified in the cotton fabric treated with poly(maleic acid). The five-member cyclic anhydride is a reactive intermediate and readily esterifies when reaction sites are available. We also found that those polycarboxylic acids, which form five-member cyclic anhydride intermediates, crosslink cotton cellulose more effectively than those polycarboxylic acids which form six-member cyclic anhydride intermediates. © 1993 John Wiley & Sons, Inc.     

Effect of phosphorus flame retardants on thermo-oxidative decomposition of cotton

The effect of six organophosphorus compounds, including Pyrovatex CP (PCP), diammonium phosphate (DAP), phosphoric acid (PA), tributyl phosphate (TBP), triallyl phosphate (TAP) and triallyl phosphoric triamide (TPT) on the flame retardancy of cotton cellulose was studied. PCP, PA, and DAP are more efficient compared with the other three compounds in improving the limiting oxygen index (LOI) of cotton. The effectiveness of these compounds was investigated using scanning electron microscope (SEM) images of char formed after LOI tests, char content, activation energy of decomposition and heat of combustion data. SEM images showed that DAP, PCP and PA chars maintain the surface morphology during the burning process, which might be due to the formation of a protective layer or crosslinking effect. PA, PCP, and DAP treated fabrics have a higher activation energy of decomposition, higher char content and lower heat of combustion.