Phosphazene side groups flame retardancy

In recent years, many poly(phosphazenes), [RoPN]n, with a variety of substituents at phosphorus have been prepared and they often exhibit useful properties including low temperature flexibility, resistance to chemical attack, flame retardancy, stability to UV radiation, and reasonably high thermal stability. (1,2) Compounds containing biologically, catalytically, or electrically active side groups are also being investigated. (3,4)... 

A number of liquid crystalline polyphosphazenes with mesogenic side groups have been prepared (48—50). Polymers with nonlinear optical activity have also been reported (51). Polyphosphazene membranes have been examined for gas, liquid, and metal ion separation, and for filtration (52—54). There is interest in phosphazene—organic copolymers, blends, and interpenetrating polymer networks (IPNs) (55—61) to take advantage of some of the special characteristics of phosphazenes such as flame retardance and low temperature flexibility. A large number of organic polymers with cydophosphazene substituents have been made (62). 

Although the polyhalophosphazenes have potentially useful physical and mechanical properties, their chemical reactivity and hydrolytic instability rule out their practical use. Luckily, however, an important aspect of the phosphazene polymer system is the relative ease with which the properties can be modified by the introduction of different side groups. Useful properties of such organopoly-phosphazenes include resistance to water, solvents, oils, and so on non-inflanunability and flame retardancy stability to visible and ultraviolet radiation high thermal stability (>200 C) and low-temperature flexibility and elasticity. 

Since both miscible and immiscible phosphazene blends are of considerable interest as membrances, biomaterials, or flame retardant materials, it is worthwhile to study the compatibility of these kinds of blends in more detail in order to understand more about the interaction between the polymer pair and the stability of the blends. Our goal in this study is to prepare PCPP/PS blends and investigate the compatibility and tile properties of the blends by optical clarity, DSC, SEM, FTIR, TGA and LOI. PCPP/PS is chosen in this study because (a) PCPP is known to be flame retardant (5), (b) polystyrene is a well-known versatile organic polymer and has been selected to gi t or blend with phosphazene polymers in most of the polyphosphazene-organic polymer hybrids systems (14,15), and (c) the similarity of aromatic side groups in both of the polymers. In addition, since rcPP has a special thermotropic transition temperature, T(l), and in order to further understand tiie stability of the blends, the compatibility influenced by temperature is also studied before and after T(l) transition by DSC. 

Nnmerous other derivatives have been reported in the literature. A few examples are tabulated (Table 17.8). In addition to those with phosphazene in the backbone, some contain —P=N— in side groups. The reaction of styrene with a vinyl-substituted trimer gives a copolymer that is flame retardant in a standard test and that can be used as foam for fire-resistant insulation [19]. 

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