Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 2(10), 20-25, October (2012) Res.J.Chem. Sci. International Science Congress Association 20 Adaptation of Pyrolytic Conduit of Polyester Cotton Blended Fabric with Flame Retardant Chemical ConcentrationsMuralidhara K.S.1 and Sreenivasan S.Laboratories, Textiles Committee, Govt of India, Mumbai, INDIA CIRCOT, Matunga, Mumbai, INDIAAvailable online at: www.isca.in Received 25th April 2012, revised 1st May 2012, accepted 6th June 2012Abstract Thermal degradation of polyester – cotton blended fabric material was analysed after addition of phosphorous based flame retardant chemical at different concentration levels viz., 50GPL, 150GPL, 250GPL, 300GPL and 350GPL. The thermogravimetric curve of control sample showed two steps of degradations with two major onset points. A step wise and progressive budging in thermal degradation kinetics with increase in concentration level was observed for this material. The thermal degradation onset point was progressively shoved to lower temperature with increase in chemical concentration. Two step mass loss observed in control sample was modified to be in three steps in treated samples. The mass loss curve progressively became flat with increasing chemical concentration in the sample. As a result of chemical application, an additional endotherm was emerged near 200C. The depth of this endotherm increased with increasing chemical concentration. Mass loss was also analysed in three different temperature intervals. The mass loss in first and third temperature interval increased from 9% (control) to 24% (350GPL) and 11% (control) to 39% (350GPL) respectively as the concentration increased. Also, the mass loss decreased from 70.9 % in control to 35 % for 350GPL treatment implying that the less amount of mass was decomposed due to non accessibility of free oxygen. There observed a drastic decrease in exotherm energy with minor shifting in peak point after the treatment. The activation energy was observed to be progressively decreasing from 267.6kJ/mole for control to 140.3 kJ/mole for sample of 350GPL treatment. Keywords: Polyster, pyrolytic, conduit, cotton blended fabric. Introduction Hendrix et al., in their flammability measurement and thermal decomposition of textiles article have demonstrated that calorimetric method of measurement of thermal decomposition of textile fibres are best method to measure the efficiency modification due to added FR chemicals in fibre. They have clearly established the efficiency modification of phosphorous based FR chemical on cotton in their research article. Further, they stated that the phosphorous based compounds which decompose prior to their interaction with cellulose have efficiencies which are limited by inherent efficiency of phosphorous oxides and acid. Thus molar efficiency could only be altered by the use of treating reagents which are either thermally stable up to the temperature of cellulose pyrolysis or which thermolyse to form some different types of intermediates. Phosphorous based FR chemicals are known to be effective on cellulose substrates. It has been postulated that the phosphorous based FR chemical acts completely in condensed phase to alter the fuel producing reaction in cellulose substrate. While discussing the action of phosphoric acid on degradation of cotton substrate, Hendrix et. al., have argued that the endothermic pyrolysis reaction of cotton fabric occurred at progressively lower temperature as increasing amount of phosphoric acid present in the substrate. They further exhibited that the incorporation of increasing amount of phosphoric acid reduces over all heat of combustion and also resulted in increasing amount of char formation. In another study, Barker has shown that the endothermic decomposition reaction becomes two-stage pyrolysis decomposition in presence of phosphoric acid. They related this two-stage decomposition to catalysed decomposition and catalysed phosphorylation of cotton. Flammability of cellulose and synthetic textile fibres has been independently recognized as an important area of textile research for many years. Due to their unique nature, cotton, polyester and their blends are normally found as general textile. Cotton cellulose normally decomposes below 300C and under dehydration, depolymerization and oxidation, releasing CO, CO, and carbonaceous residual char results at later temperatures4 . On the other hand polyester normally melts and flows under the influence of the temperature at above 260C. In case of polyester, the thermal decomposition is initiated by scission of an alkyl – oxygen bond, and the material decomposes via the formation of cyclic or open chain oligomers, with olefinic or carboxylic end group at above 510. Due to the tremendous differences in the physical and chemical properties of polyester and cotton, the blend of polyester-cotton (P/C blend) poses problems as far as the flammability and thermal degradation of blend fabric is concerned. During the thermal degradation of P/C blend, cotton begins to decompose at a temperature well below that required for thermal decomposition of polyester. Thus the cotton acts as Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 2(10), 20-25, October (2012) Res. J. Chem. Sci. International Science Congress Association 21 the initial source of ignition in the blend. The polyester which has melting point at 250–260C, tends to wick on the cotton char resulting in the phenomenon called scaffolding. The polyester component furnishes the additional fuel to the gas phase and as the polymer temperature is raised, the heat is produced from the combustion of cotton decomposition products. The additional fuel increases the vigour of the gas phase oxidation. Because of this, predicting the flammability of cotton – polyester blended fabric on the basis of knowledge of individual fibres is a doubtful phenomenon7-9. Phosphorous containing flame retardants (FR) have been regarded as most simple but effective chemical treatments for celluloses and for polyesters as well10,11. As the result, the phosphorous based FR chemicals are used to chemically treat P/C blended textile fabric to modify them as flame retardant textiles. FR textile materials have also been studied on the basis of their fundamental properties of thermal analysis which may include thermal degradation, decomposition and heat flow12. Since the thermal degradation is a combination of both physical and chemical processes that involve decomposition and oxidation and depend upon the activation energy (E), it is thought to be an important factor in the study of the material. Many studies have been reporting thermal degradation kinetics of cotton and polyester fibres as individual. However, the kinetic data on blend of these materials are very few13,14. Also, we find hardly any studies on thermal degradation kinetics of P/C blended material with varying FR chemical concentration. Material and MethodsMaterial: An upholstery P/C blended fabric (polyester 62% and cotton 38%, GSM 502) was treated with phosphorous containing flame retardant (Flamex DP 100 Nova-Transfer, India). Concentrations selected for application were 50 gram per litre (GPL), 150 GPL, 250 GPL, 300 GPL and 350 GPL. The chemical solution was prepared in water and applied using pad-dry-cure method. After the application, differential thermal analysis (DTA) and thermogravimetry (TG) were carried out on the control and treated fabric samples by using a SDT – 600 model instrument (TA instruments, USA). Method: The samples were subjected to controlled heating condition in a closed furnace and temperature was raised from ambient to 800C with 10C/min ramp under normal atmosphere. Thermograms associated with TG and DTA for control given in figure 1 and treated samples given in figure 2 were obtained from the instrument output. The weight loss curves of all samples were pooled in one plot given in figure 3a and heat flow curves of all the samples were pooled together in one plot given in figure 3b. This is done to establish the stepwise modification in decomposition patter with varying FR chemical concentration. Detailed information with respect to mass loss, degradation onset temperature was obtained from these thermograms given in figure 1 and 2 for samples of control and after treatment given in table 1. To evaluate the mass loss pattern during thermal degradation, mass loss data obtained from TG curve was analysed at three different temperature intervals viz., 30–250C (A), 250–500C (B) and 500–800C (C) and the same is presented in table 2. The other aim of the thermogravimetric analysis was to find out reliable values of activation energy of degradation. The method advocated by Broido was adopted for calculating the activation energy, E15. The Briodo’s equation employed to evaluate the activation energy are as follows.    \r   (1) Where, y is fraction of initial molecules not yet decomposed, T is absolute temperature (K), Tmax the absolute temperature of maximum reaction rate, is rate of heating (C/min), A the Arrhenius pre-exponential factor (s-1) and E is the activation energy (kJ/mol), R is universal gas constant (8.314 J/mol). A plot of ln (ln 1/y) versus 1000/T for various stages of weight yielded straight line and slope of which is equal to E/R. E was calculated from intercept of slope of the plot given in table 3. Results and Discussion Mass loss and Heat flow observation: Before treatment the sample lost about 9% of mass mainly due to desorption of moisture. Two major mass loss was, one around 303C (41.5%) and 393C (47.1%) observed. The onset point of this mass loss was respectively placed at 290C and 374C. This mass loss was mainly attributed to the loss of polymer due to decomposition. There observed an endotherm around 65C with enthalpy of reaction 2351 J/g. A sharp and shooting exotherm was observed with relatively high enthalpy of reaction (5225 J/g) with peak at 478C. Compared to mass loss curve of control sample given in figure 1, the mass loss curves of treated samples given in figure 2 are shaper and have least slope. From the figure 1, it is noted that the control sample exhibited two major stages of mass loss. Due to high enthalpy of exothermic reaction no residual char was left out in the final stage (after 400C). This may be due to the reason that the char component of cotton portion of blend served as additional fuel to the decomposition of polyester which under the influence of heat degrade completely without leaving any char remnant. After the treatment, it can be observed the treated samples of all the treatments have three distinct stages of mass loss given in figure 2. Also from the table 1, it is noted that the onset point of first stage was 290C for control sample was shifter to lower temperature 214C for sample of 350 GPL treatment. It is pertinent to note that the onset point of second stage observed at 374C for control sample was abruptly shoved to 402C for 50GPL treatment and progressively heaved for samples at subsequent higher concentration and finally settled at lower temperature at 326C. In contrast to the control sample, the treated samples exhibited three major mass loss events. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 2(10), 20-25, October (2012) Res. J. Chem. Sci. International Science Congress Association 22 Table-1 Thermogravimaetric data of samples Concentration (GPL) On Set Point Max Weight Loss Endotherm Exotherm ( 0 C) (%) Temp ( 0 C) Energy Temp ( 0 C) Energy Temp ( 0 C) Control 290 41.5 303.6 1605 67 5225 478 374 47.1 393.4 50 207 20.5 246 2256 61 3276 433 402 45.0 449 438 201 588 601 27.5 622 150 214 24.0 240 2252 63 3636 442 395 35.5 447 603 201 571 612 15.3 607 250 212 22.7 238 1959 60 2840 556 389 33.5 442 853 202 739 630 32.0 627 300 214 20.7 240 1750 58 2690 330 323 40.0 372 797 203 460 634 29.0 632 350 214 22.7 234 2523 51 3959 332 326 32.6 384 866 200 412 667 34.7 628 Table-2 Mass loss data of samples at different temperature intervals Concentration (GPL) Major Mass Loss Events Activation Energy (E) (kJ/mole) 30 0 C-250 0 C Stage A 250 0 C-500 0 C Stage B 500 0 C-800 0 C Stage C Control 8.9 82.0 0.0 267.7 50 27.6 42.6 27.6 141.1 150 29.8 36.0 30.8 135.6 250 27.3 37.0 32.8 132.8 300 25.0 35.7 36.9 140.0 350 23.7 35.0 39.2 140.6 Figure-1 Weight loss and heat flow curved of control P/C sample -2020406080100Heat Flow (W/g) 20406080100Weight (%) 020406080Time (min) 100200300400500600700792Temperature (°C) Exo UpUniversal V4.7A TA Instruments Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 2(10), 20-25, October (2012) Res. J. Chem. Sci. International Science Congress Association 23 a. After 50GPL treatment b. After 150GPL treatment c. After 250GPL treatment. d. After 300 GPL treatment (e: After 350GPL treatment) Figure-2 Weight loss and heat flow curved of treated P/C sample (Figure a-d) Figure 3a Shift in weight loss curve due to treatment -14-9-4Heat Flow (W/g) 20406080100Weight (%) 01020304050607080Time (min) 100200300400500600700800Temperature (°C) Exo UpUniversal V4.7A TA Instruments -12-10-8-6-4-2Heat Flow (W/g) 20406080100Weight (%) 01020304050607080Time (min) 100200300400500600700800Temperature (°C) Exo UpUniversal V4.7A TA Instruments -12-10-8-6-4-2Heat Flow (W/g) 20406080100Weight (%) 01020304050607080Time (min) 100200300400500600700800Temperature (°C) Exo UpUniversal V4.7A TA Instruments -10-8-6-4-2Heat Flow (W/g) 20406080100Weight (%) 01020304050607080Time (min) 100200300400500600700Temperature (°C) Exo UpUniversal V4.7A TA Instruments -11-6-1Heat Flow (W/g) 102030405060708090100Weight (%) 01020304050607080Time (min) 100200300400500600700Temperature (°C) Exo UpUniversal V4.7A TA Instruments 20406080100Weight (%) 01020304050607080Time (min) ––––––– Untreated – – – – 350GPL ––––– · 50GPL ––– – – 150GPL ––– ––– 250GPL ––––– – 350GPL Universal V3.9A TA Instruments Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 2(10), 20-25, October (2012) Res. J. Chem. Sci. International Science Congress Association 24 Figure 3b Shift in heat flow curve due to treatment The DTA curve of the all samples demonstrated that an endotherm at a temperature 60C associating with a weight loss 5 - 6% due to desorption of moisture. This endotherm in control sample progressively grew broader with increasing concentration in treated samples. This wide endotherm in treated samples suggests that application of FR chemicals enabled the blended fibres to absorb more moisture, which is expelled by absorption of more thermal energy. The DTA curve of treated samples exhibits a second endotherm at 200C given in figure 2. This large endotherm peaking around 200 – 205C was associated with a concomitant weight loss (30 – 40%). This second endotherm was entirely absent in control sample given in figure 1 and therefore it is entirely accredited to the applied FR chemical in samples. The presence of second endotherm in treated samples may be explained as follows. Phosphorous FR chemical releases inert or not easily oxidizable phosphorous radicals, which slow down the process of oxidative decomposition of substrate. The release of phosphorous radical in the form of ammonia, phosphoric acid, and water vapour leads to mass loss along with an endotherm at around 200C 16. As a result of application of FR chemical, a quantity of mass is left out after 500C for 50GPL treatment. This mass is regarded as char. The char degraded at higher temperature at 601C for 50GPL treatment and progressively rose at 667C for 350GPL treatment. The control sample showed a sharp and shooting exotherm with single peak at hovering 478C. The exotherm in treated samples was found reduced but developed into broader, prolonged and got split into bimodal with peak temperature point of exotherm reducing progressively with increasing concentration. In the control sample this exotherms was much sharper and the peak was at higher temperature (100C). This indicates that the heat release is distributed within a broad exotherm covering wide area resulting in major decrease in releasing rate of heat and the combustible gases which fuel the flaming combustion reaction. When compared to the control samples, it is evident that the treated samples posses lower decomposition temperature, decreased heat release rate and increased char yield. The mass loss observed in the samples was analysed between three temperature ranges. Table 2 reveals that the added FR chemical gradually customized the pyrolytic path of P/C blend sample. The two stage mass loss observed in control sample was altered to three stages after the treatment. It is noted that the most of the mass (82.0%) in control samples was decomposed in the temperature range B. Only 9% of mass was decomposed in range temperature A and no was mass left out for decomposition at C. After the treatment, the mass loss in range A increased to 27.6% for 50GPL treatment and to 29.8% for 150GPL treatment. The mass loss was then decreased slightly in samples of further higher treatment. The mass loss observed for 350GPL treatment was 23.7%. At this range the mass loss was mainly due evolution of various non flammable gases from added chemical and augmented moisture from textile fibre. The observed mass loss in range B was reduced to 43% after the 50GPL treatment. In the range B, the moss decomposed was mainly textile fibre. The FR chemical containing phosphorous as active content released inert or not easily oxidizable phosphorous radicals. These radicals are poor in oxygen and hindered the process of oxidative decomposition of P/C blend. As the result and due to non accessibility to atmospheric oxygen, hindered oxidations lead to reduced mass loss in the range B. The mass loss in range C was increased considerably to 25%. As the increase in concentration to 50 GPL, 150GPL, 250GPL, 300 GPL and 350GPL, the mass at stage C was also increased to 25%, 28%, 31%, 33%, 37% and 39% respectively. Therefore it may be stated that more and more char was created due to hindered fibre decomposition at temperature range B. This char gets decomposed at higher temperature (stage C). As a result of FR chemical application, the one major step mass loss (82%) observed in control samples was split into three major events. And the decrease/increase in mass loss at all the three stages is gradual and ensued with increase in chemical concentration. Activation energy (E): As there are two distinct stages of mass decomposition in the control sample, one pertaining to decomposition of cotton and other pertaining to polyester, the activation energy (E) for control and treated samples was calculated for two stages given in table 2. The control sample exhibited 146.3 kJ/mole and 121.4 kJ/mole in the first and second part of decomposition respectively. It may be seen from the table 2, that the 2nd step mass loss leads more E value than the first step. The application of FR chemical at different concentrations gradually reduced the E to minimum. The drastic decrease in Ea values occurred for all the treatment17. The progressive reduction in E implies that the amount of burning material in the last stage is considerably less. This is due to the fact that less flammable products are formed or continuous burning of products is hindered. The overall thermal decomposition and E profile of the sample under decomposition has changed after treatment with flame retardant chemicals which corroborates the fact that treated samples are highly flame retardant. -15-10-5Heat Flow (W/g) 01020304050607080Time (min) ––––––– Untreated – – – – 350GPL ––––– · 50GPL ––– – – 150GPL ––– ––– 250GPL ––––– – 300GPL Exo UpUniversal V3.9A TA Instruments Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 2(10), 20-25, October (2012) Res. J. Chem. Sci. International Science Congress Association 25 ConclusionAs a result of FR chemical application, the one major step mass loss (71%) observed in control samples was split into three major events. The mass loss in temperature range B decreased drastically. The mass loss increased considerably in other two stages. And the decrease/increase in mass loss at all the three stages is gradual and ensued with increase in chemical concentration. in the treated samples, an additional endotherm (near 200C) was observed in addition to one at around 60C. This additional endotherm was entirely due to release of non oxydizable phosphorous radicals which, by the way of heat consuming, reduced the mass loss in stage B. As the result more mass was observed at stage C. The reduction in exotherm during decomposition of mass at the stage C indicates that the material was decomposed less vigorously leading to decreased activation energy. The increasing in FR chemical concentration, the P/C blend material progressively became non thermal degradable. Reference1.Hendrix J.E., Drake G.L. and Barker R.H., Pyrolysis and Combustion of Cellulose, III. Mechanistic Bases for the Synergism involving organic Phosphate and Nitrogenous Bases, J. of Appl. Polymer Sci.,64, 257 (1972)2.Hendrix J.E., Anderson T.K., Clayton T.J., Olson E.S. and Barker R.H., Flammability Measurement and Thermal Decomposition of Textiles, Flammability of Fabrics, Flame and Flammability series, Edited by Hilado C.J., Technomic Publishing Co. Inc, , 41–73 (1974)3.Barker R.H., H.B.S. Special Publication 411, Proceedings of Symposium held at NBS, Gaithersburg, Md. (1973)4.Tian C.M., Xie J.X., Guo H.Z. and Xu J.Z., The effect of metal ions on thermal oxidative decgradation of cotton cellulose ammonium phosphate, J Therm Anal Cal, 73, 827–834 (2003)5.Montaudo G., Puglisi C. and Samperi F., Primery Thermal Degradation Mechanism of PET and PBT, Polymer degradation stability, 42, 13–28 (1993)6.Hossein Najafi, Improvement of Burning Propetores on the Cottn/Polyester/Lacra Blend Fabric with Nano Silicone Material in Nano Silicone, World Applied Sciences J., 6(11), 1532 – 1539 (2009)7.Hendrix J.E. and Robert H. Barker, Flammability and Flame Retardation of Cotton– Polyester Blend, 8.Shukla L. and Arya P., Flame Retardant based on Poly (Flourophosphanzene) and organo brominated compound for the polyester/cotton shirting, Textile Dyer and Printer, 35/5, 16–18 (1998) 9.Kubakawa H., Takahashi K., Nagatini S. and Hatakeyama T., Thermal Decomposition behavior of Polyester/Cotton blended fabric treated with Flame Retardants, (Japanese) World Textile Abstract, 5517, 298–305 (1999)10.Drake G.L. (Jr), Flame Retardant for Textiles in Kirk – Othmer Encyclopedia of Chemical Technology, 3rd edition, 10, (1980) 11.Weil E.D., Recent developments in Phosphorous based Flame retardants, Proc 3rd Beijing Sym, Flame Retardants and Flame Retardant matter, Beijing, 177–83 (1999)12.Leonard E. and Godfrey A., Thermogravimetric Analysis (TGA) Studies of Flame-Retardant Rayon Fibers, Textile Research Journal, 40(2), 116-126 (1970)13.Anderson D.A. and Freeman E.S., The kinetics of the thermal degradation of Polysterene and Polyethylene [J], J. of Polymer Sci., 54, 253–261 (1961) 14.Kaur B., Gur I.S. and Bhatnagar H.L., Thermal Degradation Studies of Cellulose Phosphates and Cellulose Thiosulphates, Angew. Makromol. Chem, 147, 157–183, (1987)15.Broido A., A simple, sensitive graphical method of treating thermogravimetric analysis data: Part A - 2 [J], J. Polym Sci, 7, 1761-1773 (1969)16.Levchik S.V., Camino G., Costa L. and Levchik G.F., Mechanism of action of Phosphorous based flame retardant in Nylon 6, I. Ammonium Polyphosphate, Fire Mat, 19, 1 – 10 (1995) 17.Dahiya J.B. and Krishnakumar, Flame Retardant Study of Cotton coated with Intumescents Kinetics and effect of Metal ions, J. Sci & Ind Res.,68, 548–554 (2009)