Study Of Preparation And Performance Of Hydrophobic Flame Retardant Polyurethane Elastomer

Due to their excellent resistance to abrasion, oil, tear, chemical corrosion and other properties, polyurethane elastomers (PUEs) have been widely applied in industrial and agricultural production, national defense construction and people’s daily life. However, ordinary polyurethane material is combustible and its flame retarding performance is poor. In addition, polyester PUEs are easy to hydrolyze. Its water resistance property and surface property are poor, which has limited the practical application of PUEs. Therefore, it is of great significance to improve the performance of PUEs regarding to flame retarding and water resistance.On the basis of related literature, this work studied the modification of PUEs mainly in two aspects to improve its flame retarding performance and hydrophobic nature:(1) four new types of diamine chain extenders were synthesized by changing the hard segments of polyurethane through molecular design. Then a kind of polyurethane elastomer that is flame retarding and hydrophobic naturally was synthesized by introducing functional elements like F, P, S, and Br into the material with the help of the diamine chain extenders.(2) A kind of oligomer expansion retardant that contains fluorine, phosphorus and nitrogen was synthesized and applied to thermoplastic polyurethane elastomers. The group characterized the structure of the synthesized compounds using FT-IR (Fourier Transform infrared spectroscopy) and NMR (nuclear magnetic resonance spectrometer). Besides, a series of investigations were conducted on the performance, curing reaction and thermal degradation reaction kinetics of the PUEs with the help of a thermo-gravimetric analyzer, a contact angle meter, a micro combustion calorimeter and SEM (scanning electron microscopy). The research revealed the relationship between the structure and properties of PUEs, which has significance for innovation in both theory and practice. The main work and results of the study are as follows:1. The results of of the analysis of FT-IR,1H NMR,19F NMR and31P NMR, the structures of the four synthetic diamines, including2,2-bis [4-(4-amino-2-trifluoromethyl phenoxy) phenyl] hexafluoropropane (BAFPF6P),10-[2,5-bis (2-trifluoromethyl-4-aminophenoxy)phenyl]-9,10-dihydro-9-oxa-10-phosphaphenanthre ne-10-oxide (DOPQ-NH2),1,4-bis [(4-amino-2-trifluoromethyl-phenoxy)-3,5-dibromo-phenyl]propane(BAFBP), and4,4’-bis (4-amino-2-trifluoromethyl-phenoxy) diphenyl sulfone (BAFPPS), were consistent with the design.2. Using the four kinds of synthetic diamines as chain extender instead of MOCA, through changing the isocyanate index and molecular weight of polyester glycol, etc., four kinds of PUEs--respectively fluorinated, fluorinated and phosphorous, fluorinated and sulphureous, fluorinated and bromie were synthesized successfully.3. Contact angle test results showed that compared with conventional ones, surface tensions of the four new kinds of PUEs decreased due to the introduction of fluorine element, but the degrees were different. The contact angle between the fluorinated PUEs with BAFPF6P as chain extender and water was the biggest, up to105.5°. The effect was obvious with the surface tension decreasing by nearly50%. Meanwhile, the water absorption test further proved that the fluorinated PUEs were more hydrophobic and had lower water absorption.4. MCC test results indicated that the heat release rate and THR (total heat release) of the four new kinds of PUEs decreased compared with conventional PUEs. Since the elements introduced were different, the mechanism of flame retarding varied, and the effect was also different. The carbon residue of the fluorinated and phosphorous PUEs was the largest, with a maximum of27.7%. The PHRR (peak heat release rate) and THR of fluorinated and bromie PUEs were the minimum, and the values were respectively102W/g and5.9J/g, far below the ordinary PUEs.5. Through TGA test, it was found that the heat resistant performance of the four kinds of fluorinated PUEs was different. The heat resistance of PUEs synthesized with BAFPF6P was higher than ordinary PUEs, while that of PUEs synthesized with DOPQ-NH2was lower. The main reason may be the existence of the easy-to-break bond of P-O.6. A kind of oligomer expansion type flame retardant containing fluorine, phosphorus and nitrogen was successfully synthesized through Phenyl dichlorophosphate (PDCP) reacting with fluorinated diamine. And the research of the retardant in thermoplastic polyurethane elastomer(TPU) showed that the performance was better than commonly used flame retardant polyphosphate amine(APP). When adding30parts of the oligomer expansion type flame retardant into the TPU, the oxygen index was up to30%, reaching the V0level when tested in accordance with the ASTM UL94standard. What’s more, the retardant was easy to mold and had good processing performance.7. Research on the curing kinetics of the PUEs by using rubber vulcanization /resin curing apparatus showed that the apparent activation energy of fluorinated polyurethane reached71.6KJ/mol during the curing reaction, while the value was only41.6KJ/mol when MOCA was used as curing agent. The analysis indicated that the-CF3group in the BAFPF6P molecule might result in the decrease of nucleophilic addition reaction activity of-NH2and-NCO groups. Thermal degradation kinetics studies showed that the thermal degradation activation energy of the fluorinated and phosphorus PUEs was higher than that of ordinary PUEs, which on the other hand explains why the fluorinated and phosphorous PUEs performed better in flame retarding compared with ordinary PUEs.