Polymers heat resistant

Heat-resistant fib( Heat-resistant polymers Heat-set inks Heatshield Heat shields Heat stability Heat stabilizers... 

Polyquinoxalines (PQ) have proven to be one of the better heat-resistant polymers with regard to both stabiUty and potential appHcation. The aromatic backbones are derived from the condensation of a tetramine with a bis-glyoxal, reactions first done in 1964 (61,62). In 1967, a soluble, phenylated version of this polymer was produced (63). The chemistry and technology of polyquinoxalines has been reviewed (64). 

New heat-resistant polymers containing -iiitrophenyl-substituted quinoxaline units and imide rings as well as flexible amide groups have been synthesi2ed by polycondensation reaction of a dianainoquinoxaline derivative with diacid dichlorides (80). These polymers are easily soluble in polar aprotic solvents with inherent viscosities in the range of 0.3—0.9 dL/g in NMP at 20°C. AH polymers begin to decompose above 370°C. 

Heat-Resistant Polymers" in ECT 3rd ed., Vol. 12, pp. 203—225, byj. Preston, Monsanto Triangle Park Development Center, Inc. 

Low Temperature Properties. Medium hardness compounds of average methyl acrylate, ie, VAMAC G, without a plasticizer typically survive 180° flex tests at —40° C. Such performance is good for a heat-resistant polymer. Low temperature properties can be greatly enhanced by the use of ester plasticizers (10). Careful selection of the plasticizer is necessary to preserve the heat resistance performance of the polymer. Plasticized high methyl acrylate grades lose only a few °C in flexibiUty, compared to grades with average methyl acrylate levels. 

The thermoset polyimides are a family of heat-resistant polymers with acceptable properties up to 260°C (500°F). They are unaffected by dilute acids, aromatic and ahphatic hydrocarbons, esters, ethers, and alcohols but are attacked by dilute alkahes and concentrated inorganic acids. 

In some countries the extensive use of asbestos as a filler is somewhat discouraged because of the hazards associated with its use. In other parts of the world moulding compositions of enhanced heat resistance have been developed by the use of especially heat-resisting polymers used in conjunction with asbestos and other mineral fillers. 

Silicones and Other Heat-resisting Polymers 29.2.1 The Grignard Method... 

Over the years various lines of attack have been used in the search for heat-resistant polymers, which may be considered under the following headings ... 

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