Phosphorus-containing polymers flame-retardant properties

When I started working at Victor Chemical Works in 1942, my boss. Dr. Howard Adler, wanted me to look into the possibility of making some phosphorus-containing polymers. It is known that organic phosphorus compounds have flame retarding properties. To put things in the proper historical perspective, at that time vinyl polymers and nylon were relatively new commercial products. (Polymers such as the ethylene terephthalate polyesters and polycarbonate were not introduced to the market place until many years later.)... 

In this paper, the surface grafting of rayon fabrics with nitrogen and phosphorus containing polymers in cold plasma is studied. The analytical data (IR spectroscopy, TGA, electron microscopy, elemental analysis, etc.) indicate the formation of grafted copolymers. The grafted rayon fabrics present improved flame-retardant properties, the best behavior was proved by those grafted with polyurea of phosphinic acid. 

Although no other phosphorus-containing polymers synthesized cationically have been commercialized, they exhibit interesting properties due to their composition, i.e., low flamability, flame retardancy and high efficiency to complex heavy metal ions. 

Phosphorus-containing polymers, especially those comprising vinylphosphonic acid (VPA) and vinylphosphonate moieties, have become attractive polymers on an industrial scale, due to their various applications based on the properties of the phosphonic group. In early applications, poly(VPA) and its derivatives were noted as efficient scale inhibitors in cooling and boiler water systems, by inhibiting the formation of calcium sulfate, carbonate, and phosphate and as flame retardants." ... 

Vinyl and allyl phosphonates can be used as comonomers in addition polymers. Also, modifications of polymers with phosphorus-containing groups, such as phosphorylation of polyvinyl alcohol, leads to improvements in flame retardancy compared to the polymers themselves. Phosphorus-containing acrylates have adhesive properties as well as FR ones. Acrylates containing phosphonic acid groups have some interesting and encouraging properties. 

For flame-retardant polyester fibres the copolymerisation of phosphorus retardants is the most common method. However, a serious difficulty is that the phosphorus-containing polymer is easily hydrolysed. Work by the Toyobo Company Limited in Japan has shown that two identical PET fibres can offer differing properties depending on where the phosphorus compound is situated within the pol5mier chains. One has the addition as a side chain and the other an identical phosphorus compound in the polymer backbone. Both fibres had almost the same physical and flame retardant properties, yet the main-chain type hydrolysed around twice as fast as the side-chain type, and led to an immediate drop in toughness. 

Carja lonela-Daniela, Serbezeanu Diana, Lisa Gabriela, Vlad-Bubulac Tachita, and Hamciuc Corneliu. Thermal degradation and kinetic studies of new flame-retardant phosphorus-containing polymers with liquid crystalline properties. Int. J. Polym. Anal. Charact. 19 no. 4 (2014a) 372-382. 

Another polyester type, i.e., polycarbonate, is rather seldom solvolytically depolymerized because of losing (at least partially) carbonate groups/bonds obtained via phosgene route synthesis. Troev et al. [29] recently described PC chemical degradation with dialkyl phosphonates (dimethyl or diethyl) or triethyl phosphate. The products, oligomeric carbonates containing phosphorus atoms, can be considered as precursors for the modification of various polymers by improving their flame-retardant properties, thermal stability, and adhesion. 

Ren, H., Sun, J., Wu, B., and Zhou, Q., Synthesis and properties of a phosphorus-containing flame retardant epoxy resin based on bisphenoxy(3-hydroxy) phenyl phosphine oxide, Polym. Degrad. Stab., 2007, 92, 956-961. 

Brominated styrene grafted onto PET is capable of acting as a nonvolatile FR for PET fabrics [328]. Polyphosphate esters can be used as flame retardant plasticizers [204], phosphorus containing moieties act as color improvers and thermostabilizers in polyesters [198, 205]. Antistatic properties of copolymers containing moieties with sulfonic acids have been reported [107]. Some polymers, like poly(JV-vinylimidazole) impart anticorrosive and antirusting properties to protective coatings of metals [329]. 

Phosphorus containing unsaturated polyesters Expandable graphite ammonium polyphosphate, triphenyl phosphate Flammability and thermal properties investigated, by UL 94 [13] and LOL Polymers containing ethylene glycol and ammonium polyphosphate showed the best flame retardance [44]... 

Flame retardants reacted with the polymer backbone usually provide protection at lower levels and thus have a smaller, usually malign, influence on the compound s mechanical and physical properties. In the case of phosphorus-containing chemicals utilised for FR purposes, there exists a... 

Phosphorus-containing oligomers (low polymers) have been included in this article because they have become more important commercially than high polymers, since they can be used as additives or coreactants to introduce sufficient phosphorus for flame retardancy or some other desired property provided by phosphorus, such as metal binding (5,6). 

Wang Zheng, Wu Wei, Zhong Yuhua, Ruan Mingzhu, and Hui Lin Lin. Flame-retardant materials based on phosphorus-containing polyhedral oligomeric silsesquioxane and bismaleimide/DBA with improved thermal resistance and dielectric properties. J. Appl. Polym. Sci. 132 no. 9 (2015) 41545-41555. 

Kilinc Mert, Cakal Gaye O., Bayram Goknur, Eroglu Inci, and Ozkar Saim. Flame retardancy and mechanical properties of pet-based composites containing phosphorus and boron-based additives. J. Appl. Polym. Sci. 132 no. 22 (2015) 42016-42021. 

Phosphorus-based flame retardants are usually more suitable for engineering plastics that undergo charring than for commodity polymers. In some plastics, such as PC-ABS or poly(phenylene oxide)-HIPS blends, phosphorus-based flame retardants are more effective then halogenated flame retardants. Antimony trioxide, which is a part of halogen-containing formulations, is a Lewis acid and may destabilize some condensation polymers. Furthermore, the impact properties of engineering polymers may suffer due to the presence of powdery antimony trioxide. 

---