Softening polymer

Place 25 g. of methyl methacrylate polymer (G.B. Diakon (powder). Perspex (sheet) U.S.A. Lucite, Plexiglass) in a 100 ml. Claisen flask, attach an efficient condenser e.g., of the double smface type) and distil with a small luminous flame move the flame to and fro around the sides of the flask. At about 300° the polymer softens and undergoes rapid depolymerisation to the monomer, methyl methacrylate, which distils over into the receiver. Continue the distillation until only a small black residue (3-4 g.) remains. Redistil the hquid it passes over at 100-110°, mainly at 100-102°. The yield of methyl methacrylate (monomer) is 20 g. If the monomer is to be kept for any period, add 0 -1 g. of hydro quinone to act as a stabiUser or inhibitor of polymerisation. 

With an amorphous thermoplast the polymer softens over a rather short temperature interval from the glassy to the rubbery state. With a semi-crystalline polymer a certain amount of softening takes place at Tg with further T- increase the stiffness drops very gradually up to the melting point... 

The so called plasticization effect, i.e., the depression of the glass transition temperature is also an important feature the sorbed gas acts as a kind of lubricant , making it easier for chain molecules to slip over one another, and thus causing polymer softening. 

At elevated temperatures al polymers soften, dependent on their glass-rubber transition points, Tg, and/of their melting points, Tm. These temperatures limit the practical use of plastics. To characterize the softening behaviour, in practice various types of standard tests are being carried out, resulting in values for the softening temperature , defined in different ways. The values mostly used are the ISO Heat Deflection Temperature (HDT) and the Vicat Softening Temperature (VST or... 

TG-DTA and DSC are suitable for product quality control as exemplified by OIT measurements for polyethylene (PE) and quantitative analysis of the rubber phase in ABS and of a polymer/ softener/soot/mineral filler mixture [77]. 

Table I. Coagulate Particle Size and Polymer Softening Point (1)...

Emulsion Polymer Softener Catalyst Foaming Agent Wet Pick-Up... 

Melt processing is a common alternative that is particularly useful for dealing with thermoplastic polymers and holds great interest because of the ease with which the process could be scaled up to industrial standards. Thermoplastic polyurethane nanocomposites can be fabricated by melt compounding of CNTs with polymer resin. Melt processing makes use of the fact that thermoplastic polymers soften when heated. Amorphous polymers like elastomer... 

Both polymers (of undetermined chain length) were found to be thermally stable. An analogous species, 14, was synthesized from 3,5,3, 5 -tetramethyl-l,4-xylene-4,4 -dipyrazole. This polymer softens above 360 °C. 

Figure Attenuation and frequency vs temperature fen- 97-MHz SAW devices with various Him thickness of polysobutylene (PIB). The maximum in attenuation and the sigmoidal frequency excursion are due to the onset of film resonance as the polymer softens with temperature. The temperature at which these AW trends occur depends on the thickness of the coating (thicker coatings yield lower temperatures). (Reprinted with pemiis-sion. See Ref. [61). 1994 American Chemical Society.)...

In principle, this approach is quite flexible and allows the tailoring of material properties for specific applications. Polymers with properties ranging from those of typical thermoplastics to those of elastoplastics can be prepared by varying the siloxane content and siloxane block sizes. Significant reductions in polymer softening temperatures, as well as solubility enhancement, have been achieved by this copolymerization approach (5). In addition. 

Thermoplastics and thermosets. All polymers can he divided into two major groups thermoplastics and thermosets) based on their thermal processing behavior. Thermoplastic polymers soften and flow under the action... 

In metal alloys the combination of stress and environment can also lead to premature failures, indicated as Stress Corrosion Cracking, SCC [1]. The influence of the environment on SCC is generally of a chemical nature a chemical reaction occurs between the metal and the environment. Most of the research published on the ESC of polymers focuses on ESC in which the environment influences the material only physically [2-8]. In such cases the mechanism of ESC is studied and models are established for ESC prediction [9]. These models for physical ESC are based predominantly on the solubility parameters of the considered polymer/environment combination. In other words, ESC is mainly a consequence of polymer softening, i.e. it is a reduction of the interaction between the polymer chains that lowers the yield stress. 

Aqueous disparsionA- Hydration of polymer— Softening of ------------------- polymer... 

The linear and branched polymers may be more or less crystalline, and include some of the materials also used as fibers nylon, for example. They include the various polyalkenes we have mentioned polyethylene, poly(vinyl chloride), polystyrene, etc. On heating, these polymers soften, and for this reason are called thermoplastic. It is in this softened state that they can be molded or extruded. 

Polymers soften and flow at temperatures near and above Tg. Flow, a form of molecular motion, requires a critical amount of free volume. The free... 

Evafanol . [NiccaUSA] Nonionic ether Qqie urethane polymer softening/and-static agent for nylon hosiery. 

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