Polyphenylene thermal degradation

Since the thermal degradation in phenylated polyphenyls of the type XXa is caused by the loss of pendant phenyl groups, and since the reported (4, 7, 9, 10, 11, 14, 15) properties of p-polyphenylenes are quite different from those of XXa, the synthesis of an unphenylated polyphenylene by this pathway was of considerable significance. Only a few results employing this reaction have thus far been obtained. [The p-poly-phenylenes reported are black or brown, insoluble, crystalline materials of lower thermal stability than XXa.]... 

When polyphenylene sulfide Is heated In air at approximately 815°C, the major components of thermal degradation are hydrogen, methane, carbon monoxide, carbon dioxide and carbonyl sulfide. 

A comprehensive study of the thermal degradation of epoxy resins has been reported by Lee [239]. Their stability was found to be lower than that of polycarbonate, polyphenylene sulphide and teflon (Fig. 64). 

Polyphenylene ether resins were developed in the early 60 s but could not be processed because the thermal degradation temperature was a few degrees below the melt temperature required for processing. Later discovery that PS can act as a plasticizer lead to the introduction of PPE/PS, one of the most successful blend (Noryl , Prevex , Luranyl ). 

Besides the electroactive nature of polyphenylenes and polyphenylene-based polymers, excellent resistance to oxidation and thermal degradation is one of the most attractive characteristics of these systems. Many workers have reviewed such subjects as synthesis, properties, applications of polyphenylenes, due to their possible use as semiconductors, photoconductors, solid lubricants, etc., over the last few decades [178-180]. 

Billow and Miller [187] also reported fairly similar results for poly(phenylene)s prepared from mixtures of terphenyls. Poly(m-phenylene) [188], phenyl-substituted polyphenylene [189] and perfluoropolyphenylene [190] have thermal and oxidative stabilities similar to that of poly(p-phenylene). Polyphenylenes synthesized by Wurtz-Fittig and Ullmann reactions were reported to withstand heating up to 500°-550°C [187,191,192]. Electrically conductive azo derivatives of polyphenylene (cTo= l-40ohm cm ) were stable up to 300°C without any noticeable decomposition, whereas the conductive block co-polymer of poly-phenylene with p-diethynylbenezene could withstand heating for many hours at 400°-450°C [I], Poly(p-phenylene) as well as poly(tetrafluoroethylene) have been reported to withstand a similar temperature without any thermal degradation and may be used safely up to similar... 

S. Stack, 0. O Donoghue, and C. Birkinshaw. The thermal stability and thermal degradation of blends of syndiotactic polystyrene and polyphenylene ether. Polym. Degrad. Stabil, 79(l) 29-36, 2003. 

Other polymers which have been the subject of thermal degradation studies include ethylene-vinyl acetate [29, 66, 67], ethylene-vinyl alcohol [68], poly(aryl-ether ketone) [69], poly-2-vinyl-naphthalene-co-methyl maleate [34], polyphenylenes based on diethyl-benzophenone [70], polyglycollide [71-73], poly(a-methylstyrene tricarbonyl chromium [74], polytetrahydrofuran [75], polylactide [76-78], poly(vinyl) cyclohexane [79], styrene-vinyl cyclohexane [80], isopropenylacetate-maleic dianhydride [80], polyethylene glycol containing a 1,3-disubstituted phenolic group [81], poly-2-vinyl naphthalene-co-methacrylate [34], collagen biopolymers [82], chitin graft poly (2-methyl-oxazoline - polyvinyl chloride blends [83], cellulose [32, 83-88] and side-chain cholestric elastomers [89, 90]. 

Takayama, S., Mathubara, T., Aral, T., Takedo, K. Rearrangement of the main-chain and subsequent thermal degradation of polyphenylene-ether. Polym. Degrad. Stab. 50(3), 277-284 (1995)... 

Other polymers that have been examined by EGA include PVC [124-126], PS [127-130], styrene-acrylonitrile copolymers [131-133], PE and PP [134-139], polyacrylates and copolymers [140-143], and PET, polyphenylenes, and polyphenylene oxides and sulfides [143-148]. Studies involving the nse of chromatography include the thermal degradation of PVC [149], vinyl plastics [150], and polysnlfone [151]. 

Budgell and co-workers [53] studied the thermal degradation of polyphenylene sulfide (PPS) over a range of pyrolysis temperatures by flash Py-GC-MS. At the lower pyrolysis temperatures (up to about 550 °C) the major volatile products were... 

Polymer Degradation and Stability 68, No.3, 2000, p.437-43 SEMI-QUANTITATIVE ANALYSIS OF THERMAL DEGRADATION IN POLYPHENYLENE ETHER... 

Weight loss and sulfurous gas emission during thermal-oxidative degradation of 600 mg polyphenylene sulfide (1 wt.% U2CO3 as adsorbent for sulfurous compounds) [626]... 

High-temperature thermoplastics, such as polysulfone, polyether sulfone, polyphenylene sulfide, polyether imide, polyaryl ether ketone, and polyphenylene ether are processed at high temperatures (some above 300 °C). Here, the limit of pyrolysis is almost reached. Degradation and cross-linking as well as discoloration can occur thermal-oxidative and thermal-mechanical degradation under processing conditions have not been sufficiently investigated [38]. 

Polyphenylene sulfide (PPS) is extremely resistant to thermal-oxidative degradation. It is assumed that a radical-cationic mechanism is responsible for thermal-oxidative degradation of PPS in air. It explains some of the identified degradation products, such as hi-, ter-, and quaternary phenyls as well as oxygen integration in the phenoxy. However, there is still no explanation for the naphthalene products formed during degradation [573],... 

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