Containing phosphorus thermal stability

Phosphorus containing poly(maleimide-amines) were synthesized from N,N -bisdichloromaleimido-3,3 -diphenyl alkylphosphine oxides and aromatic diamines or piperazine [144]. The polymers prepared from piperazine are soluble in DMF, DM AC, DMSO, etc., but have poor thermal stability and flame retardancy. 

It has been observed that all the phenoxaphosphine ring-containing polymers have excellent thermal stability and show better heat resistance than open-chain phosphorus containing polymers. The phenoxaphosphine polymers containing aromatic rings in the backbone show little degradation below 400°C in air. 

A series of phosphorus- and bromine-containing FRs were synthesized and studied to understand their role, especially their combined effects. Thus, monocar-danyl phosphoric acid, its bromo derivatives and their formaldehyde condensates and crosslinked products [28,188] were prepared and their properties compared with analogous products made from phenol [28,189]. Table 14 gives the LOI values, char yields (Cy at 600°C), and thermal stability at 50% (T6o) decomposition. 

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)... 

Three flame retardants were compared in this study, namely, a brominated polycarbonate oligomer (58% bromine), a brominated polystyrene (68% bromine), and a brominated triaryl phosphate ester (60% bromine plus 4% phosphorus). These are described in Table I. Figures 1 and 2 compare the thermal stability of the brominated phosphate with commercial bromine-containing flame retardants by thermogravimetric analysis (TGA) and by differential scanning calorimetry (DSC). The brominated phosphate melts at 110°C and shows a 1% weight loss at 300°C. Brominated polycarbonate and brominated polystyrene are polymeric and are not as volatile at elevated temperatures as the monomeric flame retardants. 

M. Fournier, C. Fuemi-Jantou, C. Rabia, G. Herve, and S. Launay, Polyoxometalates Catalyst Materials X-Ray Thermal Stability Study of Phosphorus-containing Heteropolyacids Hj xPMi2. xVx04o13-14H20 (M = Mo, W x = 0-1), J. Mater. Chem., 2, 971-978 (1992). 

It is well known that wood samples containing phosphorus compounds can release phosphoric acid that accelerates the dehydration and carbonization of wood (i.e., with decreased threshold temperature and activation energy). As a result, phosphate renders the main decomposition of wood at lower temperatures (<300°C) and results in the formation of less flammable products and correspondingly more char. On the other hand, boric acid can increase the thermal stability of wood via a different pathway (i.e., increase in threshold temperature and activation energy), and thus suppresses the mass loss and stabilizes the char. 

The formation of borophosphate partially explains the good performance when APP and boric acid are mixed together in the epoxy resin. Indeed, in that case good mechanical resistance of the intumescent char is observed as borophosphate is a hard material, which also shows a good thermal stability. As a conclusion, the boron containing compounds provide the good structural properties of the char, whereas the phosphorus ensures the adhesion of the char to the steel. 

For polyester, the reported work82 done in Sichuan University of China, involves adding MMT clay in a copolymer of poly(ethyleneterephthalate), which with a phosphorus-containing monomer could produce PET with higher thermal stability and char-forming tendency. However, fibers were not produced from this PET-nanocomposite polymers. 

With regard to reactive flame-retardants, two routes can be followed to improve thermal stability and fire behavior of PU foams use of brominated or phosphorus-containing polyol or, for rigid foams, the introduction inside polymer backbone of more thermally stable structure than urethane, mainly isocyanurate, but also uretidione rings or carbodiimide.19... 

In this presentation, several synthesis parameters have been investigated in order to improve the thermal stability of the Ti-Zr containing phosphorus-free mesoporous oxides by using either single surfactant, i.e., cetyltrimethylammonlum bromide (CTAB) or mixed surfactants, i.e., CTAB and dodecylamine (DDA) as the templating agent under hydrothermal conditions. 

Electronic promoters, for example, the alkali oxides, enhance the specific activity ofiron-alnmina catalysts. However, they rednce the inner snrface or lower the thermal stability and the resistance to oxygen-containing catalyst poisons. Promoter oxides that are rednced to the metal during the activation process, and form an alloy with the iron, are a special group in which cobalt is an example that is in industrial use. Oxygen-containing compounds such as H2O, CO, CO2, and O2 only temporarily poison the iron catalysts in low concentrations. Sulfur, phosphorus, arsenic, and chlorine compounds poison the catalyst permanently. 

Various polyesters derived from phosphorous or phosphoric acids were prepared. Efiicient polyphosphites were synthesised in the early 196(. Polyphosphite prepared from 152 and 4,4 -isopropylidenebis(cyclohexanol) was tested as a thermal stabilizer for PC [199] or as secondary AO for radiation sterilized EPM [200]. Built-in phosphites obtained by transesterification of triallcylphosphite with 4,4 -isopro-pylidenebisphenol or 4,4 -thiobisphenol possess antioxidant properties in polyolefins. Stabilizer containing phosphite moiety 153 was prepared from tris(2-hydroxy-ethyl)isocyanate, decyl alcohol and triphenylphosphite [201]. Various phosphites were derived firom polynuclear phenols or dihydric phenols. For example, a polycondensate prepared by reaction of phosphorus trichloride with 2,5-di-rert-butylhydroquinone was tested as heat and light stabilizer for PP [202], A linear polyester with a built-in phenolic moiety was synthesised from (2,6-di-tm-butyl-4-methylphenyl)bis(6-hydroxyhexyl)phosphite and dimethyl terephthalate [203]. 

Oligomer 163 represents a stabilizer having PA chain with pendant phenolic moiety [31], Pendant hindered piperidine or piperazine moieties were attached to oligomeric stabilizers having polysulfonamide, polyurea (e.g. 164), or PA (e.g. 165) unis [213]. Polyhydrazide 166 was tested as HD AO and copper deactivator in PP [214]. Poly (nitrophenylene-carbazide disulfide) 167 was prepared for thermal stabilization of PVC. Phosphorus containing crosslinkable polymers having polyamide, polyimide and polyurea chains were prepared for flame and heat resistant applications [215]. 

Relies and Schluenz (8) have reported the preparation of poly(maleimide-ethers) by using bisphenols and bisdichloromaleimides. These polymers were soluble in dimethylformamide (DMF) and dimethylsulfoxide (DMSO) and gave tough flexible films. Phosphorus-containing poly(maleimide-amines) have been reported to have poor thermal stability and little flame retardation (9). 

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