The quality of polyiso foam depends on how far the trimerization reaction was converted during the foaming, but what is the best way to measure it?
You should consider first: is it a standard flexible foam, a standard rigid foam, or a polyisocyanurate foam. The formation of trimers in the first is negligeable, in the second depends on catalyst and temperature (foaming agent physical or water?), in case of DABCO it may be measurable. In the latter case you wasnt to produce trimers besides urethanes (or ureas?).
The determination maybe done on two ways: FTIR in solid form or after liquification of the foam, e. g. by a mixture of dipropylene glycol and di-n-butyl amine (95 : 5 parts). In the spectrum, please, consider the bands at 1709, 1420, and 1385 cm-1 (in case of MDI or polymeric MDI) but you have to calibrate your system by using a standard.
Another way is based on the difference of consumption of di-n-butyl amine by the splitting of the urethane groups. You calculate the total isocyanate amount and dissolve the material in a mixture of di-n-butyl amine and dimethyl formamide. You determine the amine content by titration with hydrochloric acid against bromophenol blue. You run the splitting of the urethane by heating under stirring and reflux for 3 hours boiling. By back titration you receive the amount of spit groups and from the difference the amount of isocyanurate.(in case of water as a foaming agent the error is rather large).
Other methods such as temperature control via thermo element or resistance thermometer are dubious because of the close heat rate evolved by any of the isocyanate reactions involved.
You can use FTIR, but various types of carbonyls may overlap, so sometimes deconvolution is necessary
http://irs.ub.rug.nl/dbi/43789bd038782.
https://www.researchgate.net/publication/223721112_An_experimental_method_for_evaluating_isocyanate_conversion_and_trimer_formation_in_polyisocyanatepolyurethane_foams
http://www.thefreelibrary.com/Isocyanate+trimerization+kinetics+and+heat+transfer+in+structural...-a015935863
http://www.grimminger-online.net/Polyurethane/Papers/New%20Polyisocyanurate%20Catalysts%20for%20Rigid%20Polyurethane%20Foams%20SPI%201994.pdf
Article Experimental method for evaluating isocyanate conversion and...
You should consider first: is it a standard flexible foam, a standard rigid foam, or a polyisocyanurate foam. The formation of trimers in the first is negligeable, in the second depends on catalyst and temperature (foaming agent physical or water?), in case of DABCO it may be measurable. In the latter case you wasnt to produce trimers besides urethanes (or ureas?).
The determination maybe done on two ways: FTIR in solid form or after liquification of the foam, e. g. by a mixture of dipropylene glycol and di-n-butyl amine (95 : 5 parts). In the spectrum, please, consider the bands at 1709, 1420, and 1385 cm-1 (in case of MDI or polymeric MDI) but you have to calibrate your system by using a standard.
Another way is based on the difference of consumption of di-n-butyl amine by the splitting of the urethane groups. You calculate the total isocyanate amount and dissolve the material in a mixture of di-n-butyl amine and dimethyl formamide. You determine the amine content by titration with hydrochloric acid against bromophenol blue. You run the splitting of the urethane by heating under stirring and reflux for 3 hours boiling. By back titration you receive the amount of spit groups and from the difference the amount of isocyanurate.(in case of water as a foaming agent the error is rather large).
Other methods such as temperature control via thermo element or resistance thermometer are dubious because of the close heat rate evolved by any of the isocyanate reactions involved.
Thank you Dr. Gyorgy and Dr Gerhardt for your valuable information.
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