Extrusion, high-temperature

Hoffmann and Schiittler (75CB844) attempted to generate methanoylcarbene by high-temperature chelotropic extrusion from a bicycloheptadiene derivative, but the only identified product was a very low yield of benzene. 

Polyaryl ether ketones may be processed on conventional injection moulding and extrusion equipment, providing sufficiently high temperatures can be achieved. Melt temperatures required are typically 370°C for unreinforced PEEK, 390°C for reinforced PEEK and both unreinforced and reinforced PEK and unreinforced PEEKK, and 410°C for reinforced PEEKK. For the latter material a temperature profile from feed zone to nozzle would be... 

Additives such as antioxidants and photostabilizers of low-molecular weight face two major problems (1) they may evaporate during high temperature moulding and extrusion process or (2) they may migrate to the surface of the plastic and get extracted. There are, in general, three ways of overcoming these problems. 

Contamination problems act as a barrier to the recycling of PET bottle waste. The presence of impurities that generate acid compounds at the high temperatures reached during the extrusion process prior to blow molding is a major problem in the reprocessing of PET because chain cleavage reactions are acid catalyzed. EVA... 

Results of Method A The agitated ampoule method proved to have too many constraints to be useful as a method for obtaining kinetic samples for this reactive extrusion. The constraints were as follows o High initiator concentrations (>0.04 wt %) and high temperatures (e.g. 

In the presence of a suitably disposed /i-hydrogen—as in alkyl-substituted thiirane oxides such as 16c—an alternative, more facile pathway for thermal fragmentation is available . In such cases the thiirene oxides are thermally rearranged to the allylic sulfenic acid, 37, similarly to the thermolysis of larger cyclic and acyclic sulfoxides (see equation 9). In sharp contrast to this type of thiirane oxide, mono- and cis-disubstituted ones have no available hydrogen for abstraction and afford on thermolysis only olefins and sulfur monoxide . However, rapid thermolysis of thiirane oxides of type 16c at high temperatures (200-340 °C), rather than at room temperature or lower, afforded mixtures of cis- and trans-olefins with the concomitant extrusion of sulfur monoxide . The rationale proposed for all these observations is that thiirane oxides may thermally... 

Polyesters exhibit excellent high temperature strength and electrical properties making them a good choice for many demanding applications. They also are physiologically inert allowing them to be used in food contact applications. The two common polyesters, polyethylene terephthalate and polybutylene terephthalate, are both used in injection molded products. Polyethylene terephthalate is often used in both extrusion and blow molded processes also. 

One type of block polymer is known as thermoplastic elastomers. They consist of a number of rubber blocks tied together by hard crystalline or glassy blocks. These materials can be processed in injection molding and extrusion equipment since the crystalline blocks melt or the glassy ones soften at high temperatures. However, at lower temperatures, such as at room temperature, the hard blocks behave very much as cross-links to reduce creep and stress relaxation. Thermoplastic elastomers have creep behavior between that of very lightly cross-linked rubbers and highly cross-... 

ISO 4894-1 1997 Plastics - Styrene/acrylonitrile (SAN) moulding and extrusion materials -Part 1 Designation system and basis for specifications ISO 4894-2 1995 Plastics - Styrene/acrylonitrile (SAN) moulding and extrusion materials -Part 2 Preparation of test specimens and determination of properties ISO 19220 2004 Plastics piping systems for soil and waste discharge (low and high temperature) inside buildings - Styrene copolymer blends (SAN PVC)... 

Trichothecenes are stable at 120°C and relatively stable at 180°C, however they are destroyed at 210°C after 40 min (Kamimura, 1989). A reduction in deoxynivalenol levels of 44% in dough and baked products has been reported by Neira et al. (1997), with dough fermentation accounting for roughly 50% of this reduction. The combination of high-temperature and pressure, commonly utilized in extrusion or autoclaved food preparation, has proven far less effective, with the best results being a 12% reduction of deoxynivalenol in autoclaved cream corn (Wolf-Hall et al., 1999). 

Melt spinning is not used for polyacrylics because they are sensitive to high temperatures. They actually begin to decompose before they reach melting temperature. Solution spinning is used instead. The dried polymer is dissolved in a polar solvent like acetone or dimethyl formamide (DMF). The spinning mechanics are otherwise the same, except the solvent is recovered as it vaporizes, immediately after the extrusion through the spinneret. Most acrylics are sold and used in the form of staple fiber. 

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