Amorphous state of polymers

Glassy state of amorphous polymer usually compare with the state of the supercooled liquid, high viscosity which excludes its free flow, and provides stability of form that characterized the solid. Glassy state at low molecular weight substances means a loss of mobility of all molecules. Glassy state of the polymers is observed when the macromolecules are immobilized. This can be achieved by lowering the temperature. Because of the macromolecule make the movement not as a single entity and segments (i.e. parts, and it resembles the movement of a caterpillar), for fixing all prices are enough to fix only part of the segments, while the other part is they can save a certain freedom of movement. This circumstance is one reason for the large deformation of polymer glasses, which made significant efforts. At the transition between the macromolecules do not raise new types of links, In the solidified polymer is observed short-range order, and the arrangement of the individual parts and the atomic groups of macromolecules.
Glassy polymer (plastic glass) is a hard brittle material, in which the macromolecules atoms or groups of atoms oscillate about the equilibrium position. The lack of mobility of a significant portion of the segments of the chain due to the high viscosity of the medium leads to the impossibility of conformational transitions of macromolecules. With increasing temperature the thermal energy may be enough to start moving parts of the segment and from one position to another, it is manifested that there is a gradual transition from the properties of hard, brittle material to the properties of a softer plastic bodies D. the Average value of the certain temperature range, in which occurs the segmental mobility of macromolecules, called the glass transition temperature TC.
In linear polymers the glass transition temperature depends on molecular weight, increasing with its growth, and When the molecular weight of the polymer reaches the value at which it begins to show the flexibility of macromolecules, TC takes a constant value At spatial polymers cross-linking of the macromolecules and the formation of net-like structures leads to an increase of the Cu the more, the denser spatial grid.
The process of glass transition is accompanied by a change many properties of the polymer – thermal conductivity, electrical conductivity, dielectric constant, refractive index.
With decreasing temperature below TC in the polymer is observed a further decrease of the thermal motion of the segments of macromolecules, who had some mobility. To cause now even a small deformation of glassy polymer, it is necessary to attach to it a greater mechanical load. While acting on the polymer stress (load) may be higher than its breaking strain, and the polymer is destroyed as a fragile body with very small deformation. The temperature at which brittle fracture of polymer, referred to as the brittleness temperature thr.
Highly elastic state of the polymer is characterized by relatively high mobility of segments of macromolecules. This leads to the fact that macromolecules tend to adopt conformations corresponding to different positions in space. Along with the two extreme conformations — fully extended and fully collapsed — there are many conformations due to different degree of collapse of macromolecules.
Highly elastic condition manifests itself only when macromolecules are of considerable length (large molecular weight). It is especially peculiar gebotenem polymers, and may occur already at room temperature. In case of significant intermolecular interactions highly elastic state is observed at elevated temperatures, i.e. when the action of intermolecular forces weakens. The relative ease of adoption of the macromolecule a variety of conformations under the influence of external mechanical stresses explains the large deformation of highly elastic (hundreds of percent). After removing the load due to the thermal movement of segments of the macromolecule to return to their original Kip formations and the deformation disappears.
Highly elastic deformation is reversible because the action of external mechanical load is small compared to the time you want the macromolecule can adopt a conformation in equilibrium for the given conditions. If the deformation of the linear polymer to be done slowly, so that the macromolecule has managed to move from one equilibrium conformation to another, is highly elastic state of the polymer will be in the viscous flow state.
Highly elastic state is observed in the temperature region TC — TT, where TT is the temperature fluidity of the polymer.
Such as the polymer is a liquid and is able to flow irreversibly under the influence of a relatively small external stress, i.e. to show plastic deformation. In the course of moving the whole of macromolecules relative to each other. Deformation in viscous flow condition can develop indefinitely and is irreversible.

Crystalline polymers

Many polymers can exist in a crystalline phase state. Thus, polyethylene, polypropylene, natural rubber, certain cellulose ethers, polyamides can form microscopic crystals.
In the crystalline state of the polymer changes from a liquid (melt, solution) at low temperatures. Crystallization occurs n the result of fixing the position of the individual segments and the occurrence of elements of the far three-dimensional order in their arrangement