Synthesis of flame retardant polyurethane film containing phosphine oxide and nitrogen

Polyurethanes have a wide range of application areas due to their various advantages such as their excellent abrasion resistance, high toughness, chemical resistance, flexibility and low film-forming temperatures. They have been widely used in coating, foam, adhesives and composites. Phosphorus and nitrogen elements give excellent flame retardant properties to polymers. Moreover, polymers containing phosphine oxide moieties have many other advantages such as high thermal and oxidative stability, solubility in organic solvents, good adhesion to other compounds and miscibility. In addition to phosphorus-based reactive-type flame retardants, phosphorus-nitrogen flame-retardant synergism system was reported in many literature and exhibited better flame-retardant efficiency than those only containing phosphorus, due to the synergistic effect between phosphorus and nitrogen. Over the past decades, additive-type flame-retardants have been used to improve the flame retardancy of polyurethanes (PU). However, the use of the additive-type flame-retardants in PUs has many disadvantages such as poor compatibility, easy leaching and decreasing mechanical properties. Therefore, studies on developing reactive-type flame retardants are emphasized on in order to incorporate the flame retardants into the PU structure. In general, the reactive-type flame-retardants containing phosphorus element were incorporated into the PU backbone to improve the flame retardancy by chemical reaction. A number of studies confirmed that phosphorus element incorporated into the PU backbone increases thermal stability of the material. This thesis is separated into three sections. In the first section, bis(3-hydroxy aminophenyl)phenylphosphine oxide (BHAPPO) was synthesized by the reaction between 3-aminophenol and P,P-dichlorophenylphosphine oxide producing BHAPPO compound and hydrochloric acid as byproduct. In the second section of the thesis, BHAPPO which contains both phosphine oxide and nitrogen groups for flame retardancy and two phenol groups, was used as a diol in the polyurethane prepolymer synthesis. In PU film synthesis, different concentrations of BHAPPO and poly(propylene glycol) (PPG) was reacted with isophorone diisocyanate (IPDI). Different diisocyanate/diol and BHAPPO/PPG ratios were used in order to determine the optimum ratios for film forming, flame retardancy and mechanical properties. In the third section, polyurethane prepolymer was applied on surfaces such as teflon, silicone, plexiglass and glass to observe its behavior on different surfaces. Different curing methods such as curing in oven, curing in vacuum oven and curing at room temperature were performed in order to determine the optimum curing conditions. After curing, the free films were separated from the surfaces and various properties such as limiting oxygen index, gloss, gel content, chemical resistance, water absorption, pendulum and pencil hardness, thermogravimetric analysis and mechanical measurements (tensile strength, elastic modulus, elongation at break and stress-strain) were investigated.