Carbon polymer interactions

It is worth noting that the model for the carbon black surface deduced from these observations possesses a limited predictive capability for other materials systems than those studied herein. The current viewpoint that polymer interactions may be discussed in terms of Lewis acidity and basicity associated with particular molecular groups comprising the polymer(44-46) coincides with the present description of the origin of carbon black activity. Specifically BPL, which contains localized Lewis acid sites, can be expected to interact readily with polymer sites that are capable of acting as a Lewis base towards the carbon sites. On the other hand Graphon, which lacks these localized Lewis acid sites, is predicted to interact weakly with the same polymer sites. Contact charge injection experiments (3 3) provide a particularly sensitive probe of the carbon-polymer interaction and may supply the best means to test such model predictions. 

Rotational-echo double-resonance (REDOR)(75,79) is a new solid-state NMR technique which is sensitive to through-space carbon-nitrogen interactions between selectively 13C and 15N-enriched sites separated by up to 5A (20-22). The parameter directly measured in a REDOR experiment is the heteronuclear dipolar coupling constant DCN, which is in itself proportional to the inverse third power of the intemuclear distance, rCN. It is this dependence on (icn)3 which accounts both for REDOR s ability to accurately measure short distances and its insensitivity to longer-range interactions. As a technique which can probe, in detail, intermolecular interactions over a distance range of 5A, REDOR is well suited to studying the distribution of small selectively-labeled molecules in polymer delivery systems. 

Even within the limitations of fixed conformation, early force fields were deficient. The predicted unit cell dimensions were too small by more than 20 percent This situation was remedied by adjusting nonbonded potentials describing the fluorine-fluorine and carbon-fluorine interactions until predicted unit cell dimensions adequately reproduced experimentally measured values. This fitting was actually carried out using structural information from several polymers and was not an ad hoc parameterization for PTFE. It should also be pointed out that reproducing PTFE cell dimensions was a process of achieving an approximately correct interchain spacing for an approximate helix since the actual crystalline structure was not known at that time. Subsequently, it has become... 

Integral adsorption enthalpies AH for the adsorption of poly(vinyl acetate), poly(n-butyl methacrylate), and polycaprolactone from carbon tetrachloride solutions on Aerosil 200 silica were measured by Korn and Killmann98), who used IR spectroscopy for the determination of p. The values obtained for the three polymers exhibited the same characteristic dependence on adsorbance as that observed for poly(ethylene glycol). If the enthalpy of polymer-solvent and polymer-polymer interactions is neglected, the net binding adsorption enthalpy AHp A can be calculated from... 

The gas-polymer-matrix model for sorption and transport of gases in polymers is consistent with the physical evidence that 1) there is only one population of sorbed gas molecules in polymers at any pressure, 2) the physical properties of polymers are perturbed by the presence of sorbed gas, and 3) the perturbation of the polymer matrix arises from gas-polymer interactions. Rather than treating the gas and polymer separately, as in previous theories, the present model treats sorption and transport as occurring through a gas-polymer matrix whose properties change with composition. Simple expressions for sorption, diffusion, permeation and time lag are developed and used to analyze carbon dioxide sorption and transport in polycarbonate. 

Such a mechanism of carbon monoxide interaction with active centers is compatible with the data on the slow copolymerization of CO with ethylene found for the ethylene polymerization by some one-component catalysts This copolymerization may proceed also in the case of two-component catalysts resulting in an increase of the number of radioactive tags in the polymer with time (see Fig. 1). Arguments have been given that the rapid increase of polymer radioactivity in the initial period (5-10 min) is due to the insertion of the first CO molecule into the active metal-carbon bond. 

The measurement of -potential was used to control the flotation recoveiy of kaolin and calcium carbonate from waste paper. The addition of a cationic polymer changes its usually negative values of -potential of kaolin and calcium carbonate (-60 and -40 mV, respectively). The -potential becomes positive when the concentration of polyelectrolyte reaches 5x10 " g/1 then gradually increases until a plateau is reached at about 1x10" g/1. The final -potential is higher for kaolin than calcium carbonate. This interaction with the polyelectrolyte results in large particles which are more readily separated and recovered. ... 

Figure 7.29 shows that coefficient of interaction increases as adhesion increases. Calcium carbonate is treated to increase filler-polymer interaction. Fig-... 

Carbon black interacts strongly with polymer (HDPE) to produce a large increase in storage modulus in a manner similar to the surface treated glass beads. The storage modulus is less sensitive to frequency. The storage modulus increase is explained by the effect of modifier on crosslinking. 

Figure 9.9 shows that yield stress increases with a filler volume fraction. Polymer type does not play a significant role here since neither polymer interacts with filler. Small additions of carbon black increase yield stress rapidly. Several equations are used to describe yield stress. The Casson equation is the most frequently used. In this equation the yield stress of a filled system depends on the yield stress and the viscosity of the matrix and on the applied shear rate. ... 

For small strains the stress-relaxation rate of vulcanized rubbers at long times is proportional to tan 8 (178). This will also be true at large strains if strain-time factorization applies. The implication of this for the results of Cotten and Boonstra (150) is that tan 8 in unswollen vulcanizates is only little affected by carbon black-polymer interactions at strain levels between 75 and 250% elongation (and at very low frequencies) and suggests that the substantial increases in tan 8 observed in filled rubbers at small strains are due primarily to the effects of secondary filler aggregation. 

Figure 3.88 (a) Possible modes of a polymer interacting noncovalently with carbon... 

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