Blends acid-base concept

Another strategy for the improvement of the thermal, dimensional, mechanical, and electrochemical stability is the application of acid-base concepts to H3P04-doped high-T basic polymers. The acid-base blend concept comprises blending of a basic polymer with an acidic polymer, where ionical acid-base cross-links are formed by proton transfer from the acidic group to the basic group (see Fig. 4.1). 

The scope of the reviewed R D work is limited to intermediate-T acid-base blend membranes prepared by mixing polybenzimidazoles and sulfonated or phosphonated acidic polymers. Other membrane types, where the acid-base concept was used to improve their relevant... 

Applications of Acid-Base Blend Concepts to Intermediate Temperature Membranes... 

Fig. 4.2 The application of acid-base blend concept to intermediate-T (a) and low-T (b) FT -conducting membranes...

As already mentioned, the acid-base blend concept was applied to intermediate-T fuel cell membranes by Hasiotis et al. [31, 42]. The blend membranes were composed of PBI Celazol (poly(2,2 -/M-phenylene-5,5 -bibenzimidazole, m-PBl, named as Bl) and polysulfone Udel sulfonated in the bisphenol A section (named... 

In this chapter, research work done with intermediate-T fuel cell membranes, in which the acid-base blend concept was applied for membrane preparation, was reviewed. The reviewed studies included membranes, where the different parameters have been varied ... 

An important question for the design of continuous flow systems is When can the classic perfectly mixed assumption (ideal CSTR) be used in a continnons flow stirred tank reactor The blend time concept can be used here. If the blend time is small compared to the residence time in the reactor, the reactor can be considered to be well mixed. That is because the residence time is proportional to the characteristic chemical reaction time. A 1 10 ratio of blend time to reaction time is often used, but often, larger values result because the mixer must do other jobs, which lead to even smaller blend times. Frequently, residence time distributions are used to determine whether a reactor is well-mixed. It is usually easy to achieve well-mixed conditions in continuous flow, turbulent stirred vessels unless the reactions are very fast, such as acid-base neutralizations. Even in laminar systems the blend time can be made much less than the required residence time for the chemical reaction mainly because required residence times are so long for high viscosity reactants. For discussions of residence time distribution analysis, see Chapter 1, Levenspiel (1972), and Nauman (1982). 

Poiyaryiene Acid-Base Biends Kerres (2001) utilized the concept of acid-base cross-Unking to improve the osmotic (sweUing) and mechanical properties of proton-conducting membranes. He showed that blending a sulfonated polymer, for example, SPEEK,... 

Here the implicit view is that the properties of the ingredients are also those of the combination, a concept of blending of properties rather than a discontinuous chemical transformation. The sal ammoniac can be decomposed by treating it with quicklime. His explanation is based on the familiar idea that acids and alkalies attract and destroy each others properties ... 

Base (1) In simple chemical terms, a substance that in aqueous solution reacts with an acid to form a salt and water considered to be hydrogen ion acceptors. (2) In perfumery, it refers to an ingredient specially formulated to represent a natural source or a blend of natural sources of fragrance, or an abstract fragrance concept. 

The concept of polymeric soil release agents has been around for well over 25 years. The initial polymer chemistries (polyethylene terephthalate-polyoxyethylene terephthalate, PET-POET) were designed to deposit on fabrics and facilitate oily soil removal upon subsequent washing [98,133,134], The limitation of this chemistry was its effectiveness on synthetics (polyester) alone, with limited benefits being observed on cotton and synthetic blends. In recent years the focus has shifted to delivering soil release on cotton. Two classes of polymer chemistries have been disclosed in the recent patent literature for cotton soil release one based on hydrophobically modified polycarboxylates derived from acrylic acid and hydrophobic comonomers at defined molar ratios [188] and the other based on modified polyamines [189-193],... 

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