Synthesis and thermal properties of spiro phosphorus compounds

Abstract

Abstract Intumescent materials, 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxideand 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane having the capacity to produce dehydratingagent, blowing agent, and undergo carbonization duringburning have been synthesized. The thermal behavior ofthe synthesized materials was investigated using differen-tial thermal analysis, thermal volatilization analysis, pro-grammed vacuum pyrolysis–mass spectrometry, flashpyrolysis–mass spectrometry and off-line pyrolysis–gaschromatography–mass spectrometry. The materials showexothermic degradation after 250 C. Monitoring therelease of hydrogen chloride and water, the blowing agentsfor the production of carbon foam, clearly indicated thesuperior performance of the pentavalent phosphorus com-pound over the trivalent phosphorus compound. The majorgaseous degradation products released during pyrolysisshowed the presence of sufficient quantities of severalalkyl-substituted benzenes and fused aromatics. Suitabledegradation mechanism has been proposed and discussedto explain the formation of various organics during thermaldegradation.Keywords Spiro phosphorus compounds Intumescence Thermal analysis Flash pyrolysis–mass spectrometry Off-line pyrolysis–GC–MSIntroductionIn the modern world, we the people live with flammableproducts such as chemicals, textile, upholstery, computers,mobile phones, etc. Flammability depends on the chemicalcomposition of the materials which generate huge amountof heat, subsequently release toxic corrosive gases oncombustion/pyrolysis [1]. Hence, it is necessary to developthermally stable products by modifying the chemicalstructure or to make the material thermally stable bycompounding it with flame retardants [2]. Usually, theincorporation of flame retardant additives or the develop-ment of flame retardant coating for flammable materials isa cost effective and easiest method for improved thermalstability.Flame retardant is a chemical substance, which inhibitsor retards physically or chemically the combustion processby releasing non-flammable products or altering the deg-radation path and allows more time for people to escapefrom the fire hazard [3, 4]. Halogenated flame retardantsremove reactive H and OH radicals, which are producedduring combustion. According to environment concerns theuse of halogenated flame retardant systems are restricted[5–7]. Inorganic metal hydroxides such as aluminumhydroxide, magnesium hydroxide, etc., are used to retardthe flammability, for effective achievement relatively highloadings are used and hence it alters the existing property[8]. Compounds having phosphorus can be effectively usedto impart flame retardancy. It traps the radicals formed in