Title: Structural effect of alkyl substituent on oxygen atom for the thermal and flame retardant behaviors of phosphoramidates Authors
Submitted to: Industrial and Engineering Chemistry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 2013
Publication Date: March 28, 2013
Citation: Nguyen, T.D., Chang, S., Condon, B.D., Slopek, R.P., Graves, E.E., Yoshioka-Tarver, M. 2013. Structural effect of alkyl substituent on oxygen atom for the thermal and flame retardant behaviors of phosphoramidates. Industrial and Engineering Chemistry Research. 52(13):4715-4724. Interpretive Summary: Flame retarded chemicals can alter the mechanism of the burning process of the treated materials as compared to untreated ones. Flame retardant structure affects greatly the combustibility, resistance to ignition and flame propagation, toxicity of combustion gases, and performance of the base material. The present study is aimed at developing two flame retardants containing phosphorus and studying their structural effect on the thermal and burning behaviors of treated cotton twill. The synthesized phosphorus compounds were grafted onto the surface of cotton fabrics and the standard test methods were utilized to examine the above behaviors of treated fabrics at different levels concentration of add-ons. Our study has proved that the two phosphorus containing flame retardants with similar structures have obviously displayed different mode of action resulting in different combustibility and flammability. With this finding we hope to add another approach to designing phosphorus containing flame retardants as a highly effective flame retardant that meets the needs of its intended end-use.
Technical Abstract: The present research is aimed at studying the structural effect of two phosphoramidate derivatives EHP Diethyl 3-hydroxypropylphosphoramidate and MHP Dimethyl 3-hydroxypropylphosphoramidate as flame retardants (FRs) for cotton cellulose. EHP and MHP were obtained in very high yield and purity by one step procedure. Cotton twill fabrics treated with the two compounds at different add-ons (5 - 20 wt%) were characterized. Vertical flammability, Limiting oxygen index (LOI), Thermogravimetric (TGA), and Microscale combustion calorimeter (MCC) analyses were performed, and all resulted in better flame retardancy and thermal behavior for MHP compared to EHP. Study on the functional groups appeared on the treated fabrics by attenuated total reflection infrared (ATR-IR) spectroscopy revealed different binding mechanisms between each compound and cotton cellulose. Analysis of the released gas products by thermogravimetric analysis-fourier transform infrared (TGA-FTIR) spectroscopy showed some distinctive details in the degradation of the treated fabrics during the burning process. The difference in flame retardant action of the two compounds on the treated fabrics may be due to the catalytic thermal decomposition of their structures that made EHP form an early acidic intermediate without binding with cellulose and MHP bind with cellulose covalently.