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Semi-crystalline polymers with strong crystalline regions resist deformation and cavitation, the formation of voids in the amorphous phase, drives yielding. [ 25 ] As done in crystalline materials, particles can be added to semi-crystalline polymers to change the mechanical properties.
In this temperature range, amorphous regions can no longer transition into crystalline regions, and the polymer as a whole has reached its maximum crystallinity. Hoffman nucleation theory addresses the amorphous to crystalline polymer transition, and this transition can only occur in the temperature range between the T m and T g.
Amorphous materials, such as liquids and glasses, represent an intermediate case, having order over short distances (a few atomic or molecular spacings) but not over longer distances. Many materials, such as glass-ceramics and some polymers, can be prepared in such a way as to produce a mixture of crystalline and amorphous regions. In such ...
Polymer materials generally will form crystalline regions, but the lengths of the molecules usually prevent complete crystallization—and sometimes polymers are completely amorphous. Quasicrystals The material holmium–magnesium–zinc (Ho–Mg–Zn) forms quasicrystals , which can take on the macroscopic shape of a pentagonal dodecahedron .
The orientation of crystallites can be random with no preferred direction, called random texture, or directed, possibly due to growth and processing conditions.While the structure of a single crystal is highly ordered and its lattice is continuous and unbroken, amorphous materials, such as glass and many polymers, are non-crystalline and do not display any structures, as their constituents are ...
An amorphism, in chemistry, crystallography and, by extension, to other areas of the natural sciences is a substance or feature that lacks an ordered form. In the specific case of crystallography, an amorphic material is one that lacks long range (significant) crystalline order at the molecular level.
In polymer physics, spherulites (from Greek sphaira = ball and lithos = stone) are spherical semicrystalline regions inside non-branched linear polymers. Their formation is associated with crystallization of polymers from the melt and is controlled by several parameters such as the number of nucleation sites, structure of the polymer molecules, cooling rate, etc. Depending on those parameters ...
All crystalline materials recognized today, not including quasicrystals, fit in one of these arrangements. The fourteen three-dimensional lattices, classified by lattice system, are shown above. The crystal structure consists of the same group of atoms, the basis, positioned around each and every lattice point. This group of atoms therefore ...