Phosphoric acid changes to pyrophosphoric
acid above 180[degrees]C and then detached from the main chain.
In chemical activation the biomasses are impregnated in various chemical activating agents such as phosphoric acid (H3PO4) , zinc Chloride (ZnCl2) , potassium hydroxide (KOH) , sulfuric acid (H2SO4) , hydrochloric acid (HCl) , nitric acid (HNO3) , pyrophosphoric
acid (H4P2O7) , sodium hydroxide (NaOH) , sodium chloride (NaCl) , potassium carbonate (K2CO3) , ammonium chloride (NH4Cl) , sodium carbonate (Na2CO3) , ferric chloride (FeCl3) , hydrogen peroxide (H2O2)  etc.
acid produced during this second PCR is later detected electrochemically.
To do this, we first synthesized tetramethylene bis(orthophosphate) intermediate (TBOP) from pyrophosphoric acid and 1,4-butanediol.
(12) The flame retarding reagents used were phenylphosphonic acid (PPA, first grade, Tokyo Kasei Industry Co.), pyrophosphoric acid (PYPA, first grade, Aldrich Chemical Co.) and tetramethylene bis(orthophosphate) (TBOP, synthesized and purified in our lab).
(9) Park, H.S., Kim, D.W., Hwang, K.H., Yoon, B.S., Wu, J.P., Park, J.W., Hahm, H.S., and Im, W.B., "Preparation and Characterization of Polyurethane Flame-Retardant Coatings Using Pyrophosphoric Lactone-Modified Polyesters/Isophorone Diisocyanate-Isocyanurate," J.
A continuous weight loss started at about 200[degrees]C was attributed to the thermal changes in phosphoric acid which was the autopolymerisation of the -P[O.sub.4] units to pyrophosphoric
([P.sub.2][O.sub.7]) and triphosphoric (-[P.sub.3][O.sub.10]) ones [25, 26], The degradation of PBI main chain occurred over 550[degrees]C.
(2) Chemical degradation, e.g., leaching of the phosphoric acid [35, 37] caused by the alteration of phosphoric acid to less conductive pyrophosphoric
acid at high temperatures [34, 38, 39]; carbon support corrosion and dissolution/sintering of platinum (Pt) catalyst in acid medium [32, 33, 35, 37].