Characteristic Molecular Weights

Fig. 14. Molecular weight characteristics of novolac resins. Shown is the size-exclusion chromatogram for a typical commercial novolac polymer. The unsymmetrical peak shape reflects the multimodal molecular weight distribution of the polymer.

Hassan, E. A. A1 Assaf, S. Phillips, G.O.. Williams, P.A. (2005). Studies on Acacia gums Part III molecular weight characteristics of Acacia seyal var. seyal and Acacia seyal var fistula. Food Hydrocolloids, Vol. 19, No. 4, (July 2005), pp. 669-677, ISSN 0268-005X. 

Molecular Weight Characteristics and Quiescent Adsorption at the 0-Condition of the Polystyrene Samples... 

In the work of Belov et al. the kinetic model that has been developed quantitatively describes the initial rate of copolymerisation, the kinetic curves of the consumption of the two monomers and the molecular weight characteristics of the resulting copolymers and their composition as mixture of ketoesters, diesters, diketones as function of the total pressure up to 40 bar,... 

Average copolymer composition and molecular weight characteristics of poly(NAM-co-NAS)... 

Their poor viscosities and, consequently, low molecular weight characteristics make the synthesis of products with favourable strength and deformation properties problematic. 

Perminova, I. V., Frimmel, F. H., Kudryavtsev, A. V., Kulikova, N. A., Abbt-Braun, G., Hesse, S., and Petrosyan, V. S. (2003). Molecular weight characteristics of humic substances from different environments as determined by size exclusion chromatography and their statistical evaluation. Environ. Sci. Technol. 37, 2477-2485. 

TABLE 13.1. SEC-Determined Molecular Weight Characteristics of Humic Substances from Different Sources as Reported in the Literature... 

Ultrafiltration (UF) is a technique that has been widely used for fractionation of HS on the basis of molecular size differences (Janos, 2003). Its application to quantify size and molecular weight characteristics of aquatic humic materials is reviewed in detail by Burba et al. (1998) and Guo and Santchi (2007). 

TABLE 2 Molecular weight characteristics of the series of nascent and etched UHMW-PE reactor powders... 

Table 5 Molecular weight characteristics and thermal transitions of poly-VII and poly-VIII ...

In a recent investigation the tensile drawing behaviour of a range of polyethylene copolymers has been studied. Full details of the copolymer composition, including the molecular weight characteristics are given in Table 2, which gives details for all polyethylene copolymers discussed in this paper. Dumbbell samples cut from quenched sheets were drawn at 75 or 115 °C at a standard crosshead speed. It was found that even at the very low concentration of one side branch per 1,000 carbon atoms there was a... 

The most useful on-line instruments would be those capable of measuring the latex properties given in Eqs, (56-60), the free soap concentration and some molecular weight characteristics. In this section we will not attempt on exhanstive survey, but will only concentrate on a few of the more rugged and more promising on-line measurements that have been used. 

PFG-NMR self-diffusion measurements on Ppep-4 indicate formation of stable tetramers over a range of temperatures from 5 C to 50 C. In fact, even at 40°C and a peptide concentration of 40 pM, ppep-4 maintains an average molecular weight characteristic of a dimer (data not shown). Downfield shifted aH resonances remain, although dimished in relative intensity. In this respect, ppep-4 is not fully dissociated and exhibits an apparent dissociatoin constant in the pM range. Only when 3.5 M urea is added to solution, is Ppep-4 fully dissociated. 

In conclusion, modern SEC is a versatile technique for the investigation of nonionic surfactants in aqueous and organic media. In combination with different spectroscopic and viscometric detectors it will provide useful information for the molecular weight characteristics, chemical composition and solution behavior of this important class of materials. 

Elastomer compounds can be plasticized by addition of organic compounds. Elastomer compounds are inherently flexible and selection of a base polymer on the basis of molecular weight characteristics, chemical composition, and degree of crystallinity serves as the basis for the properties of the compound from which an elastomer is made. Oils are the most common plasticizer for elastomers. Oils of paraffinic structure or aromatic structure can be used with elastomers in which they are compatible. Paraffin wax would also be included in this category. Other plasticizers include phthalic acid esters and adipic acid esters. Fatty acids can be used as plasticizers but these contribute to an increase in surface tack of elastomer compounds. Examples include stearic and palmitic acid. Plasticizer addition has the added benefit of aiding with incorporation of inorganic materials. 

Table 2. Molecular Weight Characteristics of Selected Polymers2...

Chemically, sennosides, having sugar moieties attached, are extremely hydrophilic and have a relatively high molecular weight, resulting in poor oral absorption. At low pH values, such as are found in the stomach, sennosides precipitate, further inhibiting absorption. However, rhein, a sennoside component released in the intestine, is lipophilic and has a low molecular weight, characteristics that favor absorption (De Witte, 1993). 

Immunoglobulin class Subclass Heavy chain Light chain Molecular weight Characteristics... 

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