Brunauer-Emmett-Teller polymers

The transport properties of electrospun nylon 6 mats have also been investigated by scientists. It has been found that the concentration of the polymer solution affected the fibre diameter, pore size, Brunauer-Emmett-Teller surface area and gas transport properties of the mats. It was shown that the filtration efficiency of nylon 6 nanofilters is superior to that of a commericial high efficiency particulate air filter for 0.3 micrometre test particles. Researchers found that the pore size and pore size distribution of electrospun polylacticacid (PLA) membranes are strongly associated with fibre mass, fibre diameter and fibre length. 

An adsorption process can be described by isotherms, i.e. by the functional relationship between the adsorbed quantities of a species vs. its activity. A direct consequence of the two possible interactions of a protic electrolyte (e.g. phosphoric, sulfuric or perchloric acid) to a polymer chain with basic groups is a multilayer-like adsorption process. Therefore, the use of an adsorption isotherm as described by the BET model (Brunauer-Emmett-Teller) is convenient. The BET model is originally derived for gas adsorption on surfaces [62, 63]. To derive a multilayer-like adsorption model for a basic ionogen polymer in analogy to the original BET model, we attribute the basic groups of the polymer chains, which can be protonated by the protic electrolyte, as adsorption sites. In case of PBI-type polymers the basic groups are the imidazole centres. 

In physical gas adsorption, when an inert gas (such as nitiogen or argon) is used as an absorbent gas, the adsorption isotherm indicates the surface area and/or the pore size distribution of the objective material by applying experimental data to the theoretical adsorption isotherm for gas adsorption on the polymer surface (eg, Brunauer— Emmett—Teller (BET)" method). 

In this section we put forward a number of quantitative confirmations that have been obtained with the aid of various experiments conducted on ICPs and ICP-polymer blends and in comparison with carbon-blackfilled compounds. These experiments included quantitative investigations of the critical volume concentration, measurements of density, the dependence of conductivity on temperature history, scanning electron microscopic studies, pyrolysis, and Brunauer-Emmett-Teller measurements, in each case in a variety of polymer matrices. These experiments have provided support for the theory that above the critical volume the disperse phase forms new dissipative structures that are responsible for the occurrence of conductivity in blends and compounds. 

We carried out Brunauer-Emmett-Teller (BET) measurements to determine whether with the adsorption of a layer of the matrix polymer different quantities of inner surface became accessible to the nitrogen. Figure 19.35 shows the figures obtained in this way for the BET surface of the carbon black after pyrolysis The more carbon black or PAni present in the compound to be pyrolyzed, the greater was the specific surface area measured after pyrolysis. This too suggests a different distribution or dispersion state or different adsorption of matrix polymer layers as a function of the quantity of carbon black incorporated. 

To obtain high BET specific surface areas (5bet> i e., surface area divided by mass, as measured using the Brunauer-Emmett Teller method) for activated carbons from plastic polymers, chemicals such KOH and NaOH have been used either almigside [32] or after the carbonization step. 

Coefficient 5(C) depends on gas condensability as well as polymer-penetrant interactions. Equation (24.2) can be expressed differently using various sorption modes in polymers. These modes, shown in Figure 24.1, are Henry s law sorption, Langmuir-mode sorption, Flory-Huggins mode sorption, dual-mode sorption, and Brunauer-Emmett-Teller (BET) mode sorption. 

Analysis of polymers by scanning electron microscopy indicates that their surface is porous, resembling a sponge. It should be noted that the surface of polymers is an important factor for their adsorption properties the adsorption efficiency is higher in the case of soft and porous surface. The BET (Brunauer-Emmett-Teller) analyses have shown that the surface... 

There are various kinds of polytetrafluoroethylene. One is granular polymer consisting of spongy, white particles having a median size of about 600/l The specific surface of this polymer is on the order of 2 m2/g (determined by nitrogen adsorption and calculations by the method of Brunauer, Emmett, and Teller). Since this specific surface area is about 1700 times the observed outer surface of the particles, these measurements confirm the porous, spongelike structure that can be seen in the photomicrograph of a cross section of several particles in Fig. la. 

Type IV is the typical 2-stage isotherm according to Brunauer, Emmett and Teller (BET-isotherm), which may be considered as a combination of the other types (e.g. II at low with III at high pressure). This type is especially found if water is sorbed in hydrophilic polymers. 

The surface area of porous nanofiber mats determined using the Brunauer, Emmett, and Teller (BET) gas adsorption model has been reported for a limited number of electrospun polymers (Ding et al. 2003 Gong et al. 2004 Ryu et al. 2003 Zhang, Y. Z., et al. 2006c). Determinations that rely on gas adsorption involve several key assumptions ... 

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