| Polyurethane (PU) is the abbreviation of getting amino acid esters together. Because it has the advantages of good elasticity, abrasion resistance, molecular structure that can be tailored, and simple processing, it is widely used in most of industries. There is much organic solvent being used in the traditional synthesis of polyurethane. With the strengthening consciousness of environmental protection, the perfection of the laws and regulations of other countries and the restriction about volatile organic compounds and toxic, environmental protection polyurethane gets increasing favor from chemical industries. Waterborne PU (WPU), as a kind of environment-friendly polyurethanes, can be formulated into materials containing little or no organic solvent, and hence they are nontoxic and environment friendly. Such environmental advantages, coupled with solvent price and the quality of those materials increasing, have steadily expanded their usages in various application fields.Waterborne polyurethanes as a sort of green materials, have been widely used in the areas of textile, wood processing, the building decoration, the leather finishing, automobile, etc, which exist flammable risk. If waterborne polyurethane has certain flame retardant properties, it can protect the base material, reduce the material surface burning rate, and even help extinguish burning. All can discover in time and prevent the fire disaster to protect people’s personal and property security. Waterborne polyurethane with flame retarding treatment processing will make it better be used in many fields, which is the development direction of waterborne polyurethane functionalization, and also the trend that the materials with multiple functions in the future.The traditional polymer materials with fire-retardant treatment often use halogen flame retardants. But halogen flame retardant in burning will release suffocative or even fatal toxic gas, such as hydrogen chloride and hydrogen bromide, which may be replaced by environment-friendly flame retardants according to increasing emphasis on environmental protection. In the situation of emphasizing environmental protection and safety requirements, boron and silicon flame retardant, as the important species of environment-friendly flame retardant, have aroused widespread attention. This research chooses the reactive flame retardant (FB) containing the element of boron (B) in molecule, the organosilicon (KH550, SP) containing the silicon element (Si), to prepare the flame retardant waterborne polyurethane. A series of waterborne polyurethane emulsion modified by boron phenolic (FB) flame retardant, were synthesized with polyether diols (N-210), isophorone diisocyanate (IPDI), boron phenolic (FB),1.4-butanediol (BDO), trimethylolpropane (TMP), and dimethylol propionic acid (DMPA) as the basic monomers. The influence of the amount of FB on polyurethane (PU) emulsion stability, water resistance, mechanical property, thermal property, and flame-retardant property was tested by FT-IR, water absorption, tensile test, swinging rod hardness test, thermal analysis (TGA), limiting oxygen index (LOI), micro-combustion calorimetry (MCC), and so on. The experiment results indicated that, with the reasonable addition of FB, both the water absorption and heat release rate of polyurethane were reduced, tensile strength and hardness were improved, and thermal stability were also improved, while the carbon yield obviously increased. The oxygen index was29%and UL-94vertical burn test showed that the flame retardancy of polyurethane had reached UL-94V-1, when the mass fraction of FB was10%in the prepolymer. Therefore, the flammable polyurethane material became nonflammable, and its flame-retardant performance was greatly improved.On the one hand, boron phenolic contains boron ester bond which bond energy far outweighs the ether bond, so the heat resistance of resin will be greatly improved. And because of the existence of boron atom, resin in cracking process can form a dense structure of the glass carbon which can effectively isolate oxygen, restrain further burning and play the retardant role. On the other hand, the containing boron compounds could form a pyknotic glass state structure layer, thought as boron oxide in the surface of the resin in high temperature conditions, which can effectively prevent combustible gas just like oxygen into the material interior, preventing materials further burning. As a result, high temperature stability and oxidation resistance of the resin are greatly improved.A series of waterborne polyurethane emulsion modified by organosilicon (KH550, SP) flame retardant, were synthesized with polyether diols (N-210), isophorone diisocyanate (IPDI), organosilicon (KH550, SP),1.4-butanediol (BDO), and dimethylol propionic acid (DMPA) as the main materials. The influence of the amount of KH550and SP on polyurethane (PU) emulsion stability, water resistance, contact angle, mechanical property, thermal property, and flame-retardant property was tested by IR, water absorption, contact angle, tensile test, thermal analysis (TGA), limiting oxygen index (LOI), micro-combustion calorimetry (MCC), and so on. The experiment results indicated that, with the addition of organosilicon, both the water absorption and heat release rate of polyurethane were reduced, and thermal stability were also improved, while the carbon yield obviously increased. The oxygen index was28%and UL-94vertical burn test showed that the flame retardancy of polyurethane had reached UL-94V-1, when KH550content was6.5%and SP content was12.6%in the prepolymer. Therefore, the flammable polyurethane material became nonflammable, and its flame-retardant performance was greatly improved.Molecule structures of organic silicon contain silicon oxygen bond. Polyurethane modified by organosilicon whose main chain containing silicon oxygen bond is actually a kind of essence flame retardant polymer. Such groups can promote materials into carbonized layers under high temperature, and silicon oxygen structure in carbonized layers can contribute to forming a continuous and antioxidative silicate protective layer, which can significantly increase the oxygen index, high temperature oxidation resistance and protect the base material under carbon layer from destroying. Generally, antiflaming function of silicon oxygen plays an important part in the flame-retardant system mainly through condensed-phase flame-retardant mechanism, realized by generating decomposition carbon layers and improving oxidation resistance of carbon layers. Silicon in polymer can endue materials with the capacity to resist oxygen flow (oxygen free radicals) ability, improving materials’ oxidation resistance. Besides, polymer containing silicon in thermal decomposition generating carbon dioxide, water vapor and silicon dioxide, which help greatly reduce the amount of corrosive gas and smoke. |
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