Amide concentration

American Society for Testing and Materials (ASTM), 242 Amic acid ammonium salt, polyimide cyclization via, 305 Amic acid formation, 301 Amidation reaction scheme, 151 Amide-amide interchange reaction, 158 Amide concentration, in polyamides, 139-141... 

Nylons are semicrystalline polymers whose properties are controlled primarily by their amide concentration, molecular orientation, crystallization conditions, and the level of absorbed water. As discussed earlier, the level of crystallinity and hence product stiffness, is maximized by high concentrations of amide groups, high orientation, slow cooling, and the absence of absorbed water. 

Cal suds, Cal soft and Cal amide concentrates can be formulated to create powerful, non-corrosive, non-filming cleaners for floors, woodwork, walls, windows, counter tops, tubs, tile and similar hard surfaces. Use levels 1-4 oz./9al of water. 

For the cine amination one would normally consider a mechanism involving the formation of thiophyne. However, several pieces of evidence lead to the rejection of the thiophyne mechanism among them, the marked dependence of product distribution on amide concentration, and the non-formation of aminated product in the reaction of 2-bromo-5-methylthiophene under the same conditions. A normal addition-elimination mechanism (2-bromo -> 3-bromo -> 3-amino) is also invalid since the conversion of 3-bromothiophene to 3-aminothiophene under the same conditions is 200 times slower than the conversion 6f 2-bromothiophene to the 3-amino compound. There is also no evidence from NMR of any initial adduct formation. Considering all these facts, the proposed mechanism (Scheme 164) for cine amination involves attack by amide ion at the /8-position of a di- or tri-bromothiophene to form an aminobromothiophene and subsequent debromination of this species. In support of this is cited the fact that the individual polybromothiophenes are converted to 3-aminothiophene by KNH2 in ammonia. Also, 4-amino-2-bromothiophene (485) has been isolated in the reaction of 2-bromothiophene with sodamide. 

The relative rate of amide and ester formation depends on the nature of the zeolite but we observe generally a rapid stabilization of the amide concentration while the ester concentration shows a linear dependence against tii.ie. A typical example is described for a HM (Si/A1 =8) (Fig. 3). The signi-... 

In our liquid ammonia experiments the amide concentration (1.5 — 8 X 10 6 M) is in a range in which appreciable ionic dissociation occurs. Negative ions in aqueous solution are well known to yield solvated electrons upon excitation in their charge-transfer bands (7, 15, 19, 22), and one may expect the same process to operate also for NH2 - in ammonia. The large blue shift of the amide peak with decreasing temperature (3) supports the view that the absorption is a charge-transfer band (27). We therefore write for potassium amide in liquid ammonia (e signifies the solvated electron) ... 

Figure 4. Concentration of the amide ion as a function of the overall alkali amide concentration...

The final product in the liquid form is transferred into the storage tank. Postreaction can be done by keeping the product in another vessel, preferrably at slightly elevated temperature for a few days. This allows further conversion of the ester byproduct to amide, thus further increasing the amide concentration. 

MAJOR APPLICATION Thermal stabilizer for polyoxymethylene, and stabilizer for polyacetal resin. Because of high amide concentration, nylon 3 shows properties of an excellent formaldehyde scavenger. 

Amides dispersed in melted PE at RT, at levels exceeding their solubility, migrate to the PE surface during and after the blowing of films. Exuded amides form random aggregates on the film s surface that reduce the close contact and cohesion between adjacent sheets. Slip or antiblock activity increases upon increasing the amount of amide on the PE surface until a critical level is reached thereafter, further increase of the surface amide concentration does not improve the slip or antiblock properties and may produce an undesirable oily layer on the film. 

It is necessary to consider enzymatic erosion in any detailed discussion of this topic. This process takes place in two steps firstly, amide penetration through the membrane (transported by water) and pore walls secondly, the enzymatic reaction occurs and the amide reacts with the enzyme trapped within the matrix, producing maltose. The characteristic duration of this process is generally the sum of the penetration time (Tp) and the reaction time (Tj.). Therefore, because the reaction velocity (Pg) is proportional to the amide concentration Cg, the following is obtained ... 

This amide oxidation is an autocatalytic phenomenon. This autocatalysis is illustrated in Fig. 4, where peak oxidation currents are plotted as a function of cosurfactant (amide) concentration, 4 for this series of homologous amides. Increasing the valeramide concentration further than illustrated in Fig. 4 leads to a two-phase system. Increasing causes a dramatic increase from a low to a high-eurrent (flux) state at a threshold eoncentration o-... 

The hydrogen exchange between NH2 and liquid NH3 has a rate constant of k= 1.5 x 10 L-mol s at 298 K which was determined from the change of the relaxation time in the NMR spectra with temperature and amide concentration. The activation parameters are AH =16.7 + 2.1 kJ/mol and AS= —51.5 + 8.4 J-K moPV The large entropy indicates a considerable rearrangement in the solvation sphere when the reactants form the activated complex [2]. 

Figure 7.3. Amide concentration on the surface of ethylene vinyl acetate copolymer vs. time. [Data from Botros, M. G, J. Plast. Film Sheeting, 11,4,...

The surface amide concentration depends on the amount of amide added to the material, as seen from the data on polypropylene (Figure 7.5). Figure 7.6 shows that only for the smaller additions of erucamide (0.04 to 0.18%) is its percentage on the surface very high (19.7 to 27.9%), then it drops down to about 10%... 

In addition to the synergy (or antagonism) of additives, the pol mer type also plays very essential role. For example, several himdred ppm of erucamide or oleamide makes low density polyethylene slippy, but 3-4 times more additive is needed to obtain the same result with linear low density polyethylene. With a metallocene polymer a combination of amide with silica is used, and this gives the non-linear effect of amide concentration. ... 

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