Interactions Polymer-additives

Porous silica packings do, however, sometimes suffer from adsorption between the sample and silanol groups on the silica surface. This interaction can interfere with the size exclusion experiment and yield erroneous information. In many cases, this problem is easily overcome by selecting mobile phases that eliminate these interactions. In addition, the surface of porous silica packings is routinely modified in order to reduce these undesirable interactions. Trimeth-ylsilane modified packing is typically used with synthetic polymers. Diol modified packing is typically used with proteins and peptides. 

Obviously, use of such databases often fails in case of interaction between additives. As an example we mention additive/antistat interaction in PP, as observed by Dieckmann et al. [166], In this case analysis and performance data demonstrate chemical interaction between glycerol esters and acid neutralisers. This phenomenon is pronounced when the additive is a strong base, like synthetic hydrotalcite, or a metal carboxylate. Similar problems may arise after ageing of a polymer. A common request in a technical support analytical laboratory is to analyse the additives in a sample that has prematurely failed in an exposure test, when at best an unexposed control sample is available. Under some circumstances, heat or light exposure may have transformed the additive into other products. Reaction product identification then usually requires a general library of their spectroscopic or mass spectrometric profiles. For example, Bell et al. [167] have focused attention on the degradation of light stabilisers and antioxidants... 

In extraction from a polymer/additive solid matrix the rate-determining step in the extraction process is governed by the interaction of the solvent of sufficient dissolution power with the matrix and the removal of the analyte (cf. Section 3.4.1.3). There appears to exist a direct relationship between degree of swelling and efficiency of extraction. The amount of C02 absorbed depends on temperature, pressure and the polymer concerned. Crystalline polymers are-not surprisingly-plasticised less... 

The main characteristics of the application of NMR to polymer/additive dissolutions are given in Table 9.6. NMR solvent-additive interactions should be avoided. This may be problematic for some systems, such as polyamides, where the polymer solvent (e.g. formic... 

In spite of the high polarity of PA6, identification of additives was also feasible in formulations of PA6/additive dissolutions, although with decreased sensitivity. Hostavin N 20, Irganox B 1171, Tinuvin 320 and Tinuvin 350 can be determined in PA6 in technical concentrations, although the sensitivity is less than for nonpolar polymers, such as polyolefins. This was tentatively explained as follows. In a nonpolar polymer matrix, the electronically excited polar additive molecule can easily be desorbed. In the polar polyamide matrix, desorption of the additives is hindered by strong polar interactions (e.g. hydrogen bridges) between the excited analytes and the polymer matrix. This hinders selective desorption of the additives by laser irradiation. However, in a polymer/additive matrix-modified solution, evaporated to dryness, the interactions between the polar... 

In preceding chapters we have indicated which tools are nowadays being used routinely or currently are under development. General trends are higher sensitivity, more information, and faster and further automation. Automatic analyses are nice (sample in, report out), but interactive analysis tools are better. It is not realistic to expect the need for more analyses. Some future needs are more reliable quantitation, reference materials and simplification of data management. A particular problem in additive analysis concerns accuracy and traceability. In many cases, extractable rather than total concentration is determined. There are still many quantitative analytical methods waiting to be developed. It is here that the field will advance. Table 10.31 lists some proposed (r)evolutionary developments in polymer/additive analysis. 

The measurement of the surface tension of SDS solutions at constant polymer additions was performed to investigate any possible interactions between SDS and the polymers used in these experiments. The results, shown in Figure 2, indicate no interaction between SDS and either PAA or PAM. Interactions between similarly charged surfactant and polyelectrolyte are not common as electrical effects frequently dominate to prevent any hydro-phobic or hydrogen bonding interaction. The hydrophilic nature of the amide dipole of polyacrylamides has been suggested (11) as a possible factor in preventing interaction with sodium dodecylsulfate,... 

The superscripts H-Cl refers to solvent proton-chlorine interaction, H-HS to solvent proton-proton interaction, and H-P to interaction of the solvent proton with the polymer. The latter should be dominated by solvent proton-polymer proton interaction. Upon addition of CDCI3, followed by extrapolation to pure CDCI3, the extrapolated rate [(1/Ti)q] is given by... 

With the exception of PC, amorphous, non-oriented polymers did not produce measurable amounts of broken segments when subjected to tension. As has been shown in previous paragraphs, large axial stresses capable of chain scission in amorphous polymers can only be transmitted into the chain by friction of slipping chains requiring strong intermolecular interactions. In addition, macroscopic fracture occurs before a widespread chain overloading and scission occurs, which is opposite to the behavior of semicrystalline polymers. 

In addition, we introduce one other major source of deviation discussed in more detail in Section 4.8, namely, effects of interparticle interactions due to charges on the particles and polymer additives. 

Theoretical studies of the role of polymer additives lag behind their analogs in electrostatic stability since polymer molecules have considerably more configurational freedom and since the interaction of the polymer molecules with the solvent is an inseparable part of phenomena in polymer-colloid mixtures. We begin with some of the general issues and a thermodynamic analysis of the role of polymer on stability in Section 13.5. 

While for m-l.c. s the state of order is only determined by the anisotropic interactions of neighbouring molecules, for the polymers additionally a disturbing effect of the backbone via the flexible spacer on the anisotropic order of the mesogenic side chains is to be expected and vice versa. Therefore it is of interest to investigate whether... 

During the polymerization, DADMAC acts not only as a monomer, but also as a low molecular weight electrolyte which suppresses the Coulombic interactions. The addition of neutral low molecular salts (NaCl [10], NaBr [52], tetra-methylammonium chloride [13]) leads in the same manner to a polymerization rate increase. Even though the viscosity of the monomer solution increases with the concentration (Fig. 5), it should be taken into account that the viscosity in the polymerizing system is more strongly influenced by the polymer than by the monomer, even at low conversions [51]. 

Concluding, the destabilization of the above polymers by chloroparaffin should be beneficial in terms of fire retardance because it induces the formation of fuel at the temperature at which HC1 is evolved. Thus, the occurrence of a polymer additive interaction in the condensed phase... 

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