Medium-molecular-weight

The PVA price has historically reflected the cost of ethylene, acetic acid, and energy. The price history for a medium molecular weight, fully hydrolyzed grade is 0.77/kgin 1970, 2.20/kgin 1980, 2.75/kgin 1988, and 2.65/kgin 1995. 

In practice, the taffy process is generally employed for only medium molecular-weight resins (1) (n = 1-4). The polymerization reaction results in a highly viscous product (emulsion of water and resin) and the condensation reaction becomes dependent on agitation. At the completion of the reaction, the heterogeneous mixture consists of an alkaline brine solution and a water—resin emulsion and recovery of the product is accompHshed by separation of phases, washing of the taffy resin with water, and removal of water under vacuum. 

Separation of Medium Molecular Weight Samples Using Toyopearl HW-50 and Toyopearl HW-55 Columns... 

Not only the linear Cl0-Cl8 a-olefins but also the linear C10-Cl8 olefins with internal double bonds, the so-called -v /-olefins, are of great importance in surfactant chemistry, n-a-Olefins and n-y-olefins have the same suitability for the manufacture of linear alkylbenzenes, the most important synthetic anionic surfactants, by alkylation of benzene. Nowadays medium molecular weight n- /-olefins are industrially produced by two processes the catalytic dehydrogenation of the corresponding n-alkanes [4,28] and the cometathesis of low and high molecular weight n-v /-olefins, obtained by double-bond isomerization of the isomeric n-a-olefins [29]. 

Fig. 47.—Hc/r vs. c for polystyrene of medium molecular weight (2.9X10 ) in benzene. (Fox, Flory, and Bueche. )...

It may be seen that APPI is most suited for very low-polarity components with medium molecular weight (<2000 Da), see also Figure 6.4. APPI enables to distinguish ortho and para isomers of phenols ... 

Eganhouse, R.P., Calder, I. A. (1976) The solubility of medium molecular weight aromatic hydrocarbons and the effects of hydrocarbon co-solutes and salinity. Geochim. Cosmochim. Acta 40, 555-561. 

With respect to different depressant studies, only a limited amount of work has been performed with Quebracho, tanic acid and different lignin sulphonates. Lignon sulphonates with a medium molecular weight were superior. 

Example ESI on a magnetic sector instrument set to R = 20,000 allows for the flail resolution of isotopic peaks in case of medium-molecular weight proteins (Fig. 11.21). This enables the direct determination of the charge state of the ions from the spacing of the isotopic peaks, i.e., 1 1h- for the lysozyme ion due to the average spaces of Am = 0.091 u and 13h- for the myoglobin ion due to Am = 0.077 u. In this particular case, the lysozyme [M+llH]" ion serves as a mass reference for the accurate mass measurement of the unknown" [M+13H] ion. [103]... 

Hybrid scorpionate/cyclopentadienyl-Mg (63) and -Zn (64,65) complexes were structurally characterized and reported to catalyze the formation of PLAs with medium molecular weights and narrow polydispersities [85]. Among them, the magnesium complex 63 is much more active than the others, giving a polymerization of L-lactide in toluene at 90 °C with 97% conversion in 2.5 h. However, it takes 30 h for zinc complexes 64 and 65 to reach similar results under the same conditions. Some representative structures of magnesium and zinc complexes are summarized in Table 2 as they display closely related ROP activity of lactide, and often stmcrnrally similar ligand systems are employed to construct these initiators. 

A Small to medium molecular weight ketones Coumarin Metyrapone Poorly induced Aflatoxin B1 NNK, Coumarin... 

Fig.2.13. Graphical evaluation of the limiting viscosity number (intrinsic viscosity) from viscosity measurements at different concentrations for a a high-molecular-weight, b a medium-molecular-weight, and c a low-molecular-weight polymer sample...

Volatile compounds are often involved in long distance attraction and are especially important as attractants and repellents (as defined by Kogan, ). One major class of volatile materials, essential oils, is comprised of complex mixtures of terpenes, phenylpropanoid derived compounds and a number of esters, alcohols, aldehydes, ketones, acids, and hydrocarbons. The constituent compounds are mostly of low to medium molecular weight and generally not highly oxygenated. Some of the biological properties of these compounds have been reviewed (17,41,46,55,56). 

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