In solid-state physics, the band structure of a solid describes those ranges of energy, called energy bands, that an electron within the solid may have (“allowed bands”) and ranges of energy called band gaps (“forbidden bands”), which it may not have. According to band theory, a conductor is simply a material that has its valence band and conduction band overlapping, allowing electrons to flow through the material with minimal applied voltage. In describing conductors using the concept of band theory, it is best to focus on conductors that conduct electricity using mobile electrons. Insulators are non-conducting materials with few mobile charges they carry only insignificant electric currents. Positive charges may also be mobile, such as the cationic electrolyte(s) of a battery or the mobile protons of the proton conductor of a fuel cell. In metallic conductors such as copper or aluminum, the movable charged particles are electrons. metal: Any of a number of chemical elements in the periodic table that form a metallic bond with other metal atoms generally shiny, somewhat malleable and hard, often a conductor of heat and electricity.Ī conductor is a material which contains movable electric charges.molecular orbital: The quantum mechanical behavior of an electron in a molecule describing the probability of the electron’s particular position and energy approximated by a linear combination of atomic orbitals.voltage: The amount of electrostatic potential between two points in space.
#Intrinsic viscosity series#
Band theory, where the molecular orbitals of a solid become a series of continuous energy levels, can be used to explain the behavior of conductors, semiconductors and insulators.In metallic conductors, such as copper or aluminum, the movable charged particles are electrons, though in other cases they can be ions or other positively charged species.A conductor is a material which contains movable electric charges.The intersection with the y-axis gives the zero-shear intrinsic viscosity (Figure 6). The viscosity values obtained are then extrapolated. To determine the intrinsic viscosity at a shear rate approaching zero, polymer solutions can be measured at various shear rates. At high shear rates the viscosity becomes shear-dependent as the polymer solutions start to show non-Newtonian behavior which is not the case at low shear rates (zero-shear viscosity). Viscosity measurements for calculating the intrinsic viscosity should always be done at a shear rate approaching 0. As such it is listed in several monographs of the EU Pharmacopoeia and US Pharmacopeia.
![intrinsic viscosity intrinsic viscosity](https://patentimages.storage.googleapis.com/df/f5/4c/653ed757b43840/imgf000009_0001.png)
However, intrinsic viscosity is also a relevant testing parameter in the pharmaceutical industry. One example in which the intrinsic viscosity is used is the plastics industry. It is used in various industries to describe the storage stability and quality of a product. This is due to the fact that intrinsic viscosity gives the true viscosity-enhancing properties of a polymer independent of its concentration in solution. The intrinsic viscosity represents the most relevant variable for describing the viscous behavior of a polymer solution. Independent of the instrument used, the determination of the intrinsic viscosity can be done in two ways as described in the following paragraphs. Furthermore, the system is closed and can be automated which makes handling much safer, efficient, and convenient for the users. It has a smaller footprint and energy consumption as well as lower solvent and sample consumption. The rolling-ball viscometer in particular offers several advantages in comparison to Ubbelohde viscometers. Falling-ball- and rolling-ball viscometers are suitable alternatives. Various types of glass capillary viscometers, especially Ubbelohde-type glass capillary viscometers, are used for the determination of the intrinsic viscosity and other polymer parameters. Both the calculation of the reduced and the inherent viscosity require the concentration value and therefore the intrinsic viscosity is an important parameter as it is an extrapolation to a theoretical zero concentration. However, this state can never be reached in reality and therefore small polymer interactions have to be considered. In this “ideal dilute solution” the concentration approaches zero meaning that the polymer molecules are isolated from each other and only interact with the solvent molecules.
#Intrinsic viscosity free#
A solution free of any interactions between the polymer molecules could only be reached in the state of the “ideal dilute solution”.
![intrinsic viscosity intrinsic viscosity](https://wiki.anton-paar.com/fileadmin/wiki/images/intrinsic-viscosity-determination/AP_WIKI_Visco_Figure_01.jpg)
As the molecular interactions decrease with decreasing concentrations, viscosity measurements are carried out with very dilute solutions. The flow behavior of the polymer solution is highly dependent on the molecular structure of the polymer as well as on interactions of the molecules with each other in solution.