What causes polymer entanglement?

What causes polymer entanglement?

Entanglement refers to the reticular or spherical structure formed by the cross-linking points produced in the polymer chain, or in between polymer chains, making the polymer chains unable to move normally and thus affecting the nature of the polymer.

What is the concept of the reptation model in the Doi Edwards theory?

The theory of reptation was first proposed by Piere Gill deGennes in 1971 and later extended to the tube model by Maasai Doi and Sam Edwards. This model describes the thermal motion of long polymer chains in concentrated solutions and melts. The virtual tube is formed by the surrounding and entwining polymer molecules.

What is polymer dynamics?

Polymer dynamics encompass a range of length scales, with motions at the various length scales responding differently to changes in thermodynamic variables (T, P, and V).

What is entanglement molecular weight?

Under the heading of polymers we can define a subclass of materials, plastics, which generally have molecular weights above 10 kDa and which are generally based on covalently bonded linear chains with simple chemical structures. The transition molecular weight is termed the entanglement molecular weight.

How does entanglement affect viscosity?

A steady increase of MWt gives a linear increase in viscosity (this is the Rouse mode). Then suddenly at Mc, the Critical Entanglement Weight, viscosity increases by MWt3.4 when we are in the Entangled mode. A similar curve can be found for dependence of solution viscosity on concentration.

What is Rouse time?

The Rouse model describes the short time (or high frequency) relax- ation of high molecular weight polymers. • The molecular theory for terminal relaxation of high molecular weight polymers, REPTATION, is simply Rouse motion of a chain confined in a tube.

What theory describes how polymer chains slip past each other?

In deGennes reptation theory, polymer chains diffuse along paths which are confined to a “tube” formed by neighboring chains (entanglements) or fixed obstacles (in the case of networks).

What is polymer melt?

Polymer melts and solutions are highly viscous liquids, possessing non-Newtonian and viscoelastic natures. The flow behaviors of molten polymers or solutions are becoming increasingly relevant to their engineering processing techniques.

What is the glass transition temperature?

Glass transition temperatures are very variable ranging from 140 °C to 370 °C according to the grades, curing process and the moisture content: For a defined grade, the glass transition temperature increases from 50 °C during post cure.

What is physical entanglement?

Quantum entanglement is a physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large …

What is plateau modulus?

The plateau modulus reflects the molecular architecture of the polymers and is dependent on the entanglement molecular weight Me, which is defined as the molecular weight between adjacent temporary entanglement points.

What is MC in polymers?

One of the basic parameters that describes the structure of an electrolyte and non-electrolyte-type hydrogels is the molecular weight between cross-links (Mc). This describes the average molecular weight of polymer chains between two consecutive junctions.

What is the meaning of polymer?

English Language Learners Definition of polymer : a chemical compound that is made of small molecules that are arranged in a simple repeating structure to form a larger molecule See the full definition for polymer in the English Language Learners Dictionary

Is the reptation model valid for polymers with long chains?

This finding is in good agreement with the experimental result, τ ∼ η ∼ M3.4. Since the reptation model describes the motion of chains through entanglements, it is only valid for long chains. In practice, this model is only applicable to polymers with M >> Me.

How can you tell if a polymer is strong or weak?

If you could look at a polymer chain close up, you would see that the visual structure and physical properties of the molecule chain mimic the physical properties of the polymer. For example, if a polymer chain comprises tightly twisted bonds between monomers that are difficult to break, the polymer likely will be strong and tough.

What is the difference between homopolymers and copolymers?

Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer. Polymers which contain only a single type of repeat unit are known as homopolymers, while polymers containing two or more types of repeat units are known as copolymers. Terpolymers contain three types of repeat units.