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The microstructure determines the possibility for the polymer to form phases with different arrangements, for example through crystallization, the glass transition or microphase separation. [21] These features play a major role in determining the physical and chemical properties of a polymer.
The degree of crystallinity is estimated by different analytical methods and it typically ranges between 10 and 80%, with crystallized polymers often called "semi-crystalline". The properties of semi-crystalline polymers are determined not only by the degree of crystallinity, but also by the size and orientation of the molecular chains.
Plastic crystals were discovered in 1938 by Belgian chemist Jean Timmermans [4] by their anomalously low entropy of fusion.He found that organic substances having an entropy of fusion lower than approximately 17 J·K −1 ·mol −1 (~2R, where R is the molar gas constant) had peculiar properties.
SMPs are known to be able to store up to three different shapes in memory. [6] SMPs have demonstrated recoverable strains of above 800%. [7] Two important quantities that are used to describe shape-memory effects are the strain recovery rate (R r) and strain fixity rate (R f). The strain recovery rate describes the ability of the material to ...
In form II, each aspirin molecule forms the same hydrogen bonds, but with two neighbouring molecules instead of one. With respect to the hydrogen bonds formed by the carboxylic acid groups, both polymorphs form identical dimer structures. The aspirin polymorphs contain identical 2-dimensional sections and are therefore more precisely described ...
Its glass transition temperature is approximately 105 °C (221 °F). [4] ABS is amorphous and therefore has no true melting point. ABS is a terpolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. The proportions can vary from 15% to 35% acrylonitrile, 5% to 30% butadiene and 40% to 60% styrene. The result is ...
The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition. [1] Examples of amorphous solids include glasses, metallic glasses, and certain types of plastics and polymers. [2] [3]
Many other products (for example, guitars) are sometimes made with acrylic glass to make the commonly opaque objects translucent. Perspex has been used as a surface to paint on, for example by Salvador Dalí. Diasec is a process which uses acrylic glass as a substitute for normal glass in picture frames.