Study On Flame Retardant Properties Of Polyurethanes Modified By ?-CD/Resorcinol Bis(diphenyl Phosphate) Inclusion Complex

As a kind of block copolymer, polyurethane consists of soft and hard segments. Soft segments are polyether or polyester glycols and hard segments are usually formed by diisocyanate and chain extender. With its excellent properties such as abrasive resistance, low temperature resistance, excellent elasticity and resilience, polyurethane has been widely used in many areas such as coatings, adhesives, foam and fiber etc. However, the limit oxygen index(LOI) value of polyurethane without flame retardant is about 18%, which is easy to burn. In addition, the burned polyurethane will release a lot of toxic fumes which will threaten the safety of human life. Now,flame retardants are usually added in polyurethane products to improve the flame retardant property for industrial applications. However, some disadvantages, such as the decrease of mechanical properties owing to the poor compatibility between flame retardant and polyurethane matrix and poor flame retardant persistence exist.?-Cyclodextrin has a particular cavity structure whose outside is hydrophilic and inside is hydrophobic. This unique hydrophilic cavity allows ?-Cyclodextrin to include guest small molecules whose sizes match ?-Cyclodextrin cavity. The host and guest molecule can form stable inclusion complexes by means of inter-molecular bond interaction. In this thesis, steable inclusion complex of ?-Cyclodextrin and resorcinol bis(diphenyl phosphate)(RDP, a commercial flame retardant) were prepared through the particular cavity of ?-Cyclodextrin. The prepared inclusion complex was added to polyurethane resin to obtain samples with flame retardancy. The main research contents and conclusions are listed as followed:?-Cyclodextrin/RDP inclusion complex was prepared in DMAC solution at 65?. The formation of inclusion complex was proved by 1H-Nuclear magnetic resonance(1H-NMR), X-ray diffraction(XRD), different scanning calorimetry(DSC) and scanning electron microscope(SEM).The inclusion ratio was determined by UV spectrometry. The result showed that the inclusion ratio of RDP reached highest value of 55.17%, when the mole ratios of ?-Cyclodextrin to RDP was 1:2.Flame retardant films were prepared by blending the ?-Cyclodextrin/RDP inclusion complex(having the highest inclusion ratio) with polyurethane resin in different ?-Cyclodextrin/RDP contents. The effect of the inclusion complex content on the mechanical and flame retardancy of the modified polyurethane films were investigated by tensile test, thermal gravimerty analysis(TGA), SEM, limit oxygen index(LOI) and vertical flame test. The results of tensile test indicated that the mechanical properties of polyurethane were improved significantly by addition of ?-Cyclodextrin/RDP. When the content of ?-Cyclodextrin/RDP was 20%, the LOI value of the modified polyurethane reached 26.2%,and UL-94 vertical burning test showed that the flame retardancy of the modified polyurethane film reached V-1.