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Polymers are composed of long molecular chains which form irregular, entangled coils in the melt. Some polymers retain such a disordered structure upon freezing and readily convert into amorphous solids. In other polymers, the chains rearrange upon freezing and form partly ordered regions with a typical size of the order 1 micrometer. [3]
For example, the system triethylamine-water has an LCST of 19 °C, so that these two substances are miscible in all proportions below 19 °C but not at higher temperatures. [1] [2] The nicotine-water system has an LCST of 61 °C, and also a UCST of 210 °C at pressures high enough for liquid water to exist at that temperature. The components ...
The onset of thermal degradation dictates the maximum temperature at which a polymer can be used. It is an important limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures which makes injection moulding easier and faster, but thermal degradation places a ceiling temperature ...
A Assuming an altitude of 194 metres above mean sea level (the worldwide median altitude of human habitation), an indoor temperature of 23 °C, a dewpoint of 9 °C (40.85% relative humidity), and 760 mmHg sea level–corrected barometric pressure (molar water vapor content = 1.16%). B Calculated values *Derived data by calculation.
Polymer solutions are solutions containing dissolved polymers. [1] These may be liquid solutions (e.g. in aqueous solution ), or solid solutions (e.g. a substance which has been plasticized). [ 2 ]
Perfectly isotactic PP has a melting point of 171 °C (340 °F). Commercial isotactic PP has a melting point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of 130 °C (266 °F). [8] Below 0 °C, PP becomes brittle. [9]
PET is hygroscopic and absorbs water. [33] About 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers. [clarification needed] Transparent products can be produced by rapidly cooling molten polymer below the glass transition temperature (T g) to form a non-crystalline amorphous solid. [34]
Polyglycolide has a glass transition temperature between 35 and 40 °C and its melting point is reported to be in the range of 225 to 230 °C. PGA also exhibits an elevated degree of crystallinity, around 45–55%, thus resulting in insolubility in water. [2]