Temperature polymer degradation

T. Yoshioka, K. Furukawa and A. Oknwaki Chemical recycling of rigid-PVC by oxygen oxidation in NaOH solntion at elevated temperature, Polym. Degrad. Stab., 67, 285-290 (1999). 

Increase the critical velocity Increase melt and/or mold temperature. Polymer degradation. Ejectabihty of the part. 

Carrasco, F., Pages, P. Thermal degradation and stability of epoxy nanocomposites influence of montmorillonite content and cure temperature. Polym. Degrad. Stab. 93, 1000 (2008)... 

Samperi F, Fhighsi C, Alicata R, Montaudo G. Thermal degradation of poly(butylene tere-phthalate) at the processing temperature. Polym Degrad Stab 2004 83 11-7. 

Acid Chloride Reaction. In situations where the reactants are sensitive to high temperature or the polymer degrades before the melt poiat is reached, the acid chloride route is often used to produce the polyamide (47). The basic reaction ia the presence of a base, B , is as follows ... 

The maximum rates of crystallisation of the more common crystalline copolymers occur at 80—120°C. In many cases, these copolymers have broad composition distributions containing both fractions of high VDC content that crystallise rapidly and other fractions that do not crystallise at all. Poly(vinyhdene chloride) probably crystallises at a maximum rate at 140—150°C, but the process is difficult to foUow because of severe polymer degradation. The copolymers may remain amorphous for a considerable period of time if quenched to room temperature. The induction time before the onset of crystallisation depends on both the type and amount of comonomer PVDC crystallises within minutes at 25°C. 

Because the polymer degrades before melting, polyacrylonitrile is commonly formed into fibers via a wet spinning process. The precursor is actually a copolymer of acrylonitrile and other monomer(s) which are added to control the oxidation rate and lower the glass transition temperature of the material. Common copolymers include vinyl acetate, methyl acrylate, methyl methacrylate, acrylic acid, itaconic acid, and methacrylic acid [1,2]. 

From the results obtained by thermal decomposition of both low-molecular weight vicinal dichlorides in the gas phase [74,75] and of the copolymers of vinyl chloride and /rthermal instability of PVC to the individual head-to-head structures. Crawley and McNeill [76] chlorinated m-1,4-polybutadiene in methylene chloride, leading to a head-to-head, and a tail-to-tail PVC. They found, for powder samples under programmed heating conditions, that head-to-head polymers had a lower threshold temperature of degradation than normal PVC, but reached its maximum rate of degradation at higher temperatures. 

The role of cavitation in ultrasound degradation has been confirmed repeatably in most experiments where cavitation was prevented, either by applying an external hydrostatic pressure, by degassing the solution, by reducing the sound intensity or the temperature, polymer chain scission was also largely suppressed [117]. 

Figure 9.2 500 MHz H NMR spectra of a commercial stabilised PE product solvent and temperature as in Figure 9.1. See Figure 9.1 for structural designations (S and P refer to residual solvent and polymer resonances, respectively). After Schilling et al. [48]. Reprinted from Polymer Degradation and Stability, 31, F.C. Schilling et al., 141-152, Copyright (1991), with permission from Elsevier...

Thermosets consist of a network of interconnected chains whose positions are fixed relative to their neighbors. Such polymers do not flow when heated. Instead, when exposed to high temperatures, thermosets degrade into char. Examples of thermosets include some polyurethanes and epoxy resins. 

Organic polymers have been used to increase the viscosity of acids. The primary application is in fracture acidizing. Binary and ternary acrylamide copolymers are the most commonly used chemicals for this application. Many of these polymers degrade rapidly in strong acids at temperatures >130 F development of more stable polymers suitable for high temperatures is desirable. Recently developed polymers for this application include acrylamide copolymers with ... 

Some polymers degrade readily when heated to the processing temperature by bond scission. In contrast, if the polymer has a completely aromatic structure (e.g., PES, PEEK) the thermal stability is high (greater than 400°C for short... 

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