Maria Soledad Larrechi

This study presents the first results of composition measurement in an ammonia/water mixture determined at real time using near-infrared (NIR) spectroscopy in an absorber test bench. Two cells were designed and constructed; a static cell for calibrating and a dynamic cell for measuring in the absorber test bench. The ammonia absorption band was not significantly affected by the solution flow rate and neither by small variations in the temperature and pressure. A linear regression model between the absorbance value at 1033 nm and the ammonia concentration was established. This model was used to estimate the concentration in an ammonia/water absorber test bench. The methodology was validated by density measurements of the samples. The value of the mean deviation was 0.0024.

Flame-retardant polybenzoxazine foams containing 1% phosphorus were prepared from diphenolic acid-based benzoxazine and 9,10-dihydro-9-oxa-10-(1-hydroxy-1-methylethyl)phosphaphenanthrene-10-oxide. Statistical predictive models were developed to determine the influence of the foaming time ( t_f) and foaming temperature ( T_f) on the density, compressive modulus, and compressive strength of the foams. Results showed that the density of the foams exhibited great dependence on t_f, whereas both compressive properties were more dependent on T_f and t_f. Additionally, the flammability of the foams was also characterized by the limiting oxygen index. The presence of 9,10-dihydro-9-oxa-10-(1-hydroxy-1-methylethyl)phosphaphenanthrene-10-oxide greatly improved the flame retardancy of the resulting foams.