Synthesis and characterization of a novel modified expandable graphite and its application in rigid polyurethane foams

Abstract

Abstract. In this work, an intermediate product DOPO-A was firstly synthesized through an addition reaction between triethoxyvinylsilane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Then DOPO-A was hydrolyzed to form DOPO-A' (silanol of DOPO-A) and the surface of expandable graphite (EG) was modified by DOPO-A' to prepare a novel modified expandable graphite (MEG). The effects of MEG on the flame-retardant and mechanical properties of rigid polyurethane (RPU) foams were investigated. It is found that MEG is more effective in improving the limiting oxygen index (LOI) of RPU foams than EG. The cone calorimeter studies indicate that MEG flame retarded RPU foams have lower peak heat release rate，total heat release, peak smoke production rate, and CO yield than those of the EG flame retarded RPU foams. Compressive strengths of the MEG flame retarded RPU foams have a great improvement compared with those of EG flame retarded RPU foams.

Synthesis of Mono Ethylene Glycol (MEG)-Based Polyurethane and Effect of Chain Extender on Its Associated Properties

“…Hydroxyl is an important functional group and the knowledge of its content is required in many intermediate and end-use products such as polyols, resins, lacquer raw materials, and fats (petroleum industry). The most frequently described method for determining the hydroxyl number is the conversion with acetic anhydride in pyridine with the subsequent titration of the acetic acid released [ 23 , 24 , 25 , 26 ]; however, this method suffers from some drawbacks, such as the sample having to be boiled under reflux for 1 h (a long reaction time, laborious and expensive sample handling) [ 26 , 34 ], the method cannot be automated, small hydroxyl numbers cannot be determined exactly [ 20 ] and pyridine has to be used, which is both toxic and foul-smelling [ 25 ].…”

“…Five different glycols have been utilised to synthesise polyester polyols (PEs), including ethylene glycol (EG) [ 12 , 13 , 14 , 15 ], diethylene glycol (DEG) [ 16 ], triethylene glycol (TEG) [ 17 , 18 , 19 ], butanediol (BD) [ 20 , 21 , 22 ], and hexanediol (HD) [ 23 , 24 ]. Moreover, it can change the density, hardness, blowing, coating, and insulating properties of the synthesized polyurethanes [ 25 , 26 ]. There has been little research on the resilience of PUs, particularly the effect of the content concentration of the chain extenders such as mono ethylene glycol on the physical properties of polyurethanes [ 27 , 28 ].…”