Blends based in polyphenylene oxides

3 Blends Based in Polyphenylene Oxides (Modified PPOs) 

Although the first commercial modified PPOs may be considered as derived from such PPO-polystyrene blends, today three distinct classes of material can be recognised  

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Thanks to their unusual miscibility polymer blends of polyphenylene oxide and polystyrene were the first commercially successful amorphous engineering thermoplastics blends, introduced back, in 1968 Pete Juliauo of GE Corporate Research Laboratories presented a comprehensive review at the last lUPAC Meeting of The Rague(l) where he showed how the evolution of science and technology of blends (2,3) based on polyphenylene oxide, blsphenol A polycarbonate, polybutylene teraphthalate, polyamides and polyacetals, created many more opportunities for the development of engineering thermoplastics with attractive combination of attributes. 

In polymers such as polystyrene that do not readily undergo charring, phosphoms-based flame retardants tend to be less effective, and such polymers are often flame retarded by antimony—halogen combinations (see Styrene). However, even in such noncharring polymers, phosphoms additives exhibit some activity that suggests at least one other mode of action. Phosphoms compounds may produce a barrier layer of polyphosphoric acid on the burning polymer (4,5). Phosphoms-based flame retardants are more effective in styrenic polymers blended with a char-forming polymer such as polyphenylene oxide or polycarbonate. 

Fyrolflex BDP from Akzo Nobel Chemicals has been shown to exhibit higher thermal properties and hydrolytic stability than other aryl phosphates, and to provide similar or better fire retardant performance than RDP. It is a bisphenol A bis(diphenyl phosphate) compound that provides good physical properties in formulations based on PC/ABS, HIPS and polyphenylene oxide/HIPS blends. Upon thermal decomposition of the flame-retarded polymers, phosphorus tends to accumulate in the solid residue, a result which indicates that the primary FR action of BDP is most likely to be in the condensed phase. 

Polyphenylene oxide (PPO) ru A thermoplastic, linear, non-crystalline polyether obtained by the oxidative polycondensation on 2,6-dimethylphenol in the presence of a copper-amine complex catalyst. The resin has a wide useful temperature range, from below —170 to +190°C, with intermittent use to 205° C possible. It has excellent electrical properties, unusual resistance to acids and bases, and is pro-cessable on conventional extrusion and injection-molding equipment. Because of its high coat PPO is also marketed in the form of polystyrene blends (see Noryf ) that are lower-softening (Tg of PS is about 100°C vs 208°C for PPO), and have working properties intermediate between those of the two resins. 

Oligomeric aromatic phosphates have been patented and commercially used as flame-retardant additives mainly for impact-resistant polystyrene blends with polyphenylene oxide and polycarbonate blends with acrylonitrile-butadiene-styrene (ABS) copolymers (130,131). They have also been shown useful in thermoplastic polyesters (92). The principal commercial examples are based on phenol and resorcinol (Akzo-Nobel s Fyrolflex RDP) or phenol and bisphenol A (Akzo-Nobel s Fyrolflex BDP or Albemarle s Ncendx P-30). Although these have the diphosphate as their principal ingredient, they also contain higher oligomers. 

Some measurements of this property have been made in a range of electrically conducting polymers. These include epoxy resin/polyaniline-dodecylbenzene sulfonic acid blends [38], polystyrene-black polyphenylene oxide copolymers [38], semiconductor-based polypyrroles [33], titanocene polyesters [40], boron-containing polyvinyl alcohol [41], copper-filled epoxy resin [42], polyethylidene dioxy thiophene-polystyrene sulfonate, polyvinyl chloride, polyethylene oxide [43], polycarbonate/acrylonitrile-butadiene-styrene composites [44], polyethylene oxide complexes with sodium lanthanum tetra-fluoride [45], chlorine-substituted polyaniline [46], polyvinyl pyrolidine-polyvinyl alcohol coupled with potassium bromate tetrafluoromethane sulfonamide [47], doped polystyrene block polyethylene [38, 39], polypyrrole [48], polyaniline-polyamide composites [49], and polydimethyl siloxane-polypyrrole composites [50]. 

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