High-temperature polymer requirements

These LCT materials have very high tensile and flexural strength, and excellent mechanical and chemical resistance properties. Some commercial LCT are Vectra (Hoechst-Celanese) and Xydar (Amoco). Du Pont, ICI, GE, and Dow Chemical are also suppHers. Their appHcation in electronic embedding is stiU. in its infancy because of the high temperature processing requirement. Nevertheless, this class of thermoplastic polymers will play an important role in electronic embedding. 

Tetraglycidyl ether of tetraphenolethane is an epoxy resin that is noted for high-temperature and high-humidity resistance. It has a functionality of 3.5 and thus exhibits a very dense crosslink structure. It is useful in the preparation of high-temperature adhesives. The resin is commercially available as a solid (e.g., EPON Resin 1031, Resolution Performance Polymers). It can be crosslinked with an aromatic amine or a catalytic curing agent to induce epoxy-to-epoxy homopolymerization. High temperatures are required for these reactions to occur. 

For the method development of the SEC separation, the main attention should be focused on the suppression of analyte interactions with the surface of packing material. This usually requires a careful selection of the SEC column. In GPC, commercially available synthetic organic polymer columns are usually packed with styrene-divinylbenzene copolymer particles, which are only capable of weak dispersive interactions. Any possible analyte interactions with the surface could be suppressed by using a strong solvent, which will be preferentially adsorbed on the packing material surface. Selection of such a solvent is limited since the polymer solubility in that particular solvent needs to be considered. Tetrahydrofuran is the most common solvent used for most GPC separations, although for polyimids and other high-temperature polymers the use of special solvents such as n-methylpyrrolidone may be necessary. 

The patent literature on the phosphonitrilic chlorides is extensive no attempt will be made to deal with it here. Most proposed applications have been to the high-polymer field, particularly where resistance to high temperatures is required. Phosphonitrilic compounds have proved valuable in flame-proofing treatments for fabrics and have been suggested as plasticizers, as oil additives, and as catalysts in silicone manufacture. 

Melt processable, crystalline, high temperature polymers such as polyetheretherketone (PEEK) have been developed for critical application areas where processability, chemical resistance and toughness are required. PEEK has been applied as thermo-... 

High temperatures are required to melt the crystalline domains in the high-EW samples and promote dissolution. Martin et have recently found that Nafions with EWs of 1100 and 1200 dissolve in both 50 50 propanol-water and 50 50 ethanol-water, at 250°C and elevated pressure, because the crystallites of the materials are eliminated. McCain and Covitch have also reported a similar dissolution technique. The ionic membrane was chemically converted into the nonionic precursor (sulfonyl fluoride) form prior to the dissolution process. Due to the nonionic nature of the precursor, it dissolves under relatively mild conditions. These dissolution techniques for Nafion polymers provide an important means for preparation of chemically modified electrodes and membranes of any desired geometry. ... 

In summary, a fracture test has been successfully applied to a high temperature polymer. Further developments of this test are required and are already underway. 

Polybenzimidazole (PBI) is the most well-known commercial example of aromatic heterocycles used as high-temperature polymers. The synthesis of PBI is carried out as follows (see also Figure 1.36). The tetraaminobiphenyl required for the synthesis of PBI is obtained from 3,3 -dichloro-4,4 -diaminodi-phenyl (a dye intermediate) and ammonia. Many other tetraamines and dicarboxylic acids have been... 

High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) operate in a temperature range of 160 to 180 °C. For the HT-PEMFC the hydraulic system of a house is at any time a heat sink. HT-PEMFC based fuel cells can be used in hydraulic systems of new and existing buildings. Furthermore, the HT-PEMFC requires less effort to cleanup the synthesis gas of the fuel processor. But the HT-PEMFC is only demonstrated in few applications so far and the development status is not so advanced as for the LT PEMFC. 

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