Effect of sodium triphosphate on thermal decomposition of hydrated cellulose fibres

Abstract

There are several types of carbon fibre materials (CFM) fabricated by carbonization of hydrated cellulose (HC) fibres. In particular, the following brands of CFM are manufactured at Khimvolokno Scientific and Industrial Association: UVK, Uglen, UUT-2, Ural (Viskum), etc. [ 1, 2]. These materials not only differ in textile form, but also in the final heat treatment temperature (HTT). Thermal decomposition of HC fibre raw material in the presence of a catalytic additive, which significantly affects the physicomechanical characteristics of the f'mal product (CFM), is the basic technology for their production.The analysis of the published data on thermal decomposition of HC fibres in the presence of different additives [3][4][5][6][7] suggests that when they are correctly selected, the yield of CFM can be increased to 28-30 wt. %, the physicomechanical characteristics of the CFM can be improved, and the duration of the heat treatment stage, and formation of active groups in the structure of the CFM can be decreased, etc. In this respect, we considered studies of the effect of inorganic additives on thermal decomposition of HC fibres to be urgent and of scientific and practical interest.We investigated the features of thermal decomposition of HC fibres in the presence of sodium triphosphate in the 20-900"C temperature region and with different concentrations (0.05-0.1 M) of additives by physicochemical methods. The advantages of using triphosphates as additives in thermal decomposition of polymer fibres consist of the following: Triphosphates, also known as tripolyphosphates, are nontoxic, do not degrade fibres of any type, are incombustible, and do not corrode the equipment used for carbonization.HC twist fibre from Mogilev Khimvolokno Industrial Association was used for our studies, and sodium triphosphate was used as the inorganic additive. The samples of HC fibre were impregnated with aqueous solutions of Na5P3010 of different concentration for 0.5 and 1 h, then the excess solution was squeezed out and the samples were dried in air. The dried samples of HC fibres were carbonized in the setup shown in the diagram in Fig. 1. The reaction of thermal decomposition was conducted in a quartz reaction vessel 2 in helium medium with a temperature elevation rate of 2~ to 400~ The temperature was subsequently increased to the given temperature at the rate of 3.3 ~The sample was then raised to the top of the reaction vessel, cooled to 80-90~ and the yield and strength characteristics of the f'mal product were determined [81.The temperatures in furnace 1 were monitored with chromel alumel thermocouple 3, and the temperature elevation rate was regulated with a RIF-107 instrument. The derivatograms were made on a Q-1500D instrument. Calcined aluminum oxide was used with ethanol. The reaction of thermal decomposition of samples of HC was conducted in a current according to the following method: weighed portions of samples of HC fibres (--0.25 g) were taken and placed in a platinum crucible, and the temperature was raised at the ...

Carbon fibers prepared from ionic liquid-derived cellulose precursors

“…By decreasing the heating rate from 70 • C/h to 0.03 • C/h, the carbonization yield at 900 • C increased from 11 to 28 wt.-% [17]. An increased carbonization yield can also be archived by oxidative pretreatment [18][19][20][21][22], the use of a reactive atmosphere [23] or the application of carbonization aids, like catalysts for dehydration in the form of Lewis acids and bases (AlCl 3 , borax, boronic acid, KHCO 3 , NaH 2 PO 4 , ZnCl 2 ,NH 4 Cl, ammonium phosphates, and ammonium sulfates) or reagents like cross linkers (urea) [20,[24][25][26][27][28][29][30][31][32][33]. These compounds can be applied on commercial fibers from solution.…”

Cellulose‐Derived Carbon Fibers with Improved Carbon Yield and Mechanical Properties

“…For this purpose, different strategies for stabilization of rayon fibers prior to their carbonization at temperatures of 900–1500 °C have been reported allowing for carbonization yields of 25–30 wt%. Examples are the use of low heating rates during pyrolysis up to 400 °C, oxidative pretreatment, the use of a reactive atmosphere, or the application of carbonization aids, including catalysts for dehydration (AlCl 3 , borax, boronic acid, KHCO 3 , NaH 2 PO 4 , ZnCl 2 , NH 4 Cl, and ammonium phosphates and sulfates) and crosslinking reagents, e.g., urea . Recently, we reported on an ionic liquid (IL)‐derived cellulose phosphonate precursor fiber for CFs .…”

“…Examples are the use of low heating rates during pyrolysis up to 400 °C, [30][31][32] oxidative pretreatment, [33][34][35][36][37] the use of a reactive atmosphere, [38] or the application of carbonization aids, including catalysts for dehydration (AlCl 3 , borax, boronic acid, KHCO 3 , NaH 2 PO 4 , ZnCl 2 , NH 4 Cl, and ammonium phosphates and sulfates) and crosslinking reagents, e.g., urea. [35,[39][40][41][42][43][44][45][46][47][48] Recently, we reported on an ionic liquid (IL)-derived cellulose phosphonate precursor fiber for CFs. [24] During carbonization of the fibers at 1400 °C, a very high carbonization yield of 36 wt% (81.1% of theory) was reached.…”

Processing of Cellulose Using Ionic Liquids

“…successfully increased the carbon yield up to 35–38 wt% by using cellulosic derivate (cellulose tosylate/phosphate) precursor fibers spun with IL‐technology . Alternatively, other strategies have been developed to achieve higher carbonization yields of 25–38 wt% such as low heating rates during pyrolysis up to 400 °C, oxidative pretreatment, and application of carbonization aids, including catalysts for dehydration, for example, ammonium phosphates and sulfates . Nonetheless, all these can so far not compete with the above‐outlined IL‐technology, whether in space‐time yields or CF properties.…”

“…[37] Alternatively, other strategies have been developed to achieve higher carbonization yields of 25-38 wt% such as low heating rates during pyrolysis up to 400 °C, [56][57][58] oxidative pretreatment, [59][60][61][62][63] and application of carbonization aids, including catalysts for dehydration, for example, ammonium phosphates and sulfates. [62,[64][65][66][67][68][69][70][71][72][73][74] Nonetheless, all these can so far not compete with the above-outlined IL-technology, [37] whether in space-time yields or CF properties.…”