ABSTRACT
In this study, a series of ethylene glycol modified urea-melamine-formaldehyde resins (EUMFs) were synthesized from urea, melamine, paraformaldehyde and ethylene glycol, and then incorporated into rigid polyurethane foams (RPUFs) as a reactive-type liquid flame retardant. The structure of EUMFs was characterized by Fourier transform infrared spectrometry; the morphology of the foams was characterized by scanning electron microscopy; and the thermal degradation and fire behavior of RPUFs were characterized by limiting oxygen index (LOI), cone calorimetry test and thermogravimetry analysis. The results show that the incorporation of EUMFs results in an increase in thermal stability, smoke suppression and LOI of RPUFs. As the melamine loading in EUMFs increases, the peak heat release rate and the total heat release of RPUFs decrease significantly, but the LOI increases slightly. Compared with the original foam, the cells of RPUFs become less regular with nonuniform diameters. In general, EUMFs show excellent flame retardancy and smoke suppression for RPUFs.
ABSTRACT
The bulk polymerization of diallyl phthalate (DAP) was carried out at high temperature (190 degrees C) without using any initiator, and the reaction was stopped before the gelation point in order to get the prepolymer of DAP. The mixture for the prepolymer and the monomer was successfully separated by a novel ultrasonic method for the first time, and the separation efficiency for the new method was obviously higher than that for the traditional reprecipitation. The product obtained by ultrasonic separation was characterized by infrared spectroscopy (IR), gel permeation chromatography (GPC) and iodine number measurement. It was shown that the average molecular weight of the prepolymer got by the ultrasonic method was lower than that of the prepolymer got by the multi-precipitation, moreover, the molecular weight distribution of the prepolymer got by the ultrasonic separation was broader. Besides, the residual unsaturation degree of the prepolymer separated by ultrasonic was slightly higher than that of prepolymer separated by reprecipitation.
Subject(s)
Phthalic Acids/chemistry , Phthalic Acids/radiation effects , Chromatography, Gel , Molecular Weight , Phthalic Acids/isolation & purification , Polymers/chemical synthesis , Polymers/radiation effects , Spectrophotometry, Infrared , Spectroscopy, Fourier Transform Infrared , UltrasonicsABSTRACT
Preparation and characterization of porous hollow silica nanoparticles (PHSNs), with various shell thicknesses in the range of 5-45 nm and a pore diameter of about 4-5 nm, were investigated. PHSNs were fabricated via a sol-gel route with two different structure-directing templates and their shell thickness could be controlled by adjusting the reactant ratio of Na2SiO3.9H2O/CaCO3. The produced PHSNs were applied as controlled pesticide release carriers to study the effects of the shell thickness on the loading efficiency for avermectin, the UV-shielding property for the loaded avermectin and the controlled release of the loaded avermectin from the carriers. It was found that the amount of loaded avermectin decreases with the increase of shell thickness, while the UV-shielding property of PHSNs for avermectin is improved as the shell gets thicker. In addition, the shell thickness has a significant impact on avermectin release. Increasing the shell thickness in the range of 5-45 nm leads to a more sustained release by decreasing the release rate of the pesticide from PHSNs, showing that the shell thickness is one of the main controlling factors for the active agent release from such systems.