Monomer concentration effect

Monomer Concentration Effect. In bulk polymerizations such as those conducted in the present study, the dependence of polymerization rate on monomer concentration can be determined only on the basis of the dependence of rate on the extent of reaction. Reduction of the rate vs. time DSC traces to digital data files permits computer calculation of reaction rate as a function of monomer conversion. A computer program which yields print-out of the rate and time at given fractions of the total heat release allows computation of the order of reaction with respect to carbon-carbon double bond concentration. Assuming -80.0 cal gm l represents the... 

Grafting Degree. The variation in degree of grafting was correlated with the 1,2-vinyl content of PB, the monomer concentration (effect of preferential solvation by the monomer), the type and the concentration of initiator (preferential solvation by initiators), and the degree of conversion. The effect of the structure of PB on the grafting degree is tabulated in Table V. 

BY2 Byun, H.-S. and Park, C., Monomer concentration effect on the phase behavior of poly(propyl acrylate) and poly(propyl methacrylate) with supercritical CO2 and... 

The molecular weight of a polymer can be controlled through the use of a chain-transfer agent, as well as by initiator concentration and type, monomer concentration, and solvent type and temperature. Chlorinated aUphatic compounds and thiols are particularly effective chain-transfer agents used for regulating the molecular weight of acryUc polymers (94). Chain-transfer constants (C at 60°C) for some typical agents for poly(methyl acrylate) are as follows (87) ... 

Within a series with a fixed hydrophilic head group, detergency increases with increasing carbon chain length, reaches a maximum, and then decreases. This behavior frequentiy reflects a balance between increased surface activity of the monomer and decreased monomer concentration with increased surface activity. Similar effects are seen in surfactants in biological systems. 

This equation indicates that the reaction rate is proportional to the square root of the initiator concentration and to the monomer concentration. It is found that the relationship with initiator concentration is commonly borne out in practice (see Figure 2.18) but that deviations may occur with respect to monomer concentration. This may in some cases be attributed to the dependency of / on monomer concentration, particularly at low efficiencies, and to the effects of certain solvents in solution polymerisations. 

We have studied the effect of monomer concentration in the dispersion polymerization of styrene carried out in alcohol-water mixtures as the dispersion media. We used AIBN and poly(acrylic acid) as the initiator and the stabilizer, respectively, and we tried isopropanol, 1-butanol, and 2-butanol as the alcohols [89]. The largest average particle size values were obtained with the highest monomer-dispersion medium volumetric ratios in 1-butanol-water medium having the alcohol-water volumetric ratio of 90 10. The SEM micrographs of these particles are given in Fig. 15. As seen here, a certain size distribution by the formation of small particles, possibly with a secondary nucleation, was observed in the poly-... 

There are a number of important factors that must be considered before applying gamma radiation-induced grafting. These factors include the radiation sensitivity of the polymer/monomer system, radiation dose and dose rate, type and concentration of inhibitor, type of solvent or diluent, and monomer concentration. The effect of such parameters on the grafting efficiency during mutual grafting is given below. 

Figure 1 Effect of monomer concentration on the total conversion percent and grafting efficiency. LR 30 I, acid concentration l%, initiator concentration 0. l%, grafting time 1 h, and reaction temperature 27°C — = total conversion (%) O—O = grafting efficiency (%).

Figure 3 Effect of residual lignin percent in the pulp on total conversion percent and graft yield percent. LR 40 1, reaction time 1 h, reaction temperature 27°C, monomer concentration 1 mL/g pulp, initiator concentration 1%, and acid conversion 1% — = total conversion (%), O—O = graft yield (%).

Cotton linters and viscose grade wood pulp were grafted with acrylamide using the xanthate method. The effects of monomer concentration, reaction time, hydrogen peroxide concentration, reaction temperature, and liquor ratio on the grafting process were studied. Optimum conditions for the grafting reaction were established [26]. 

Summing up these results, it is clear that beating and swelling of cotton stalk pulp have important effects on graftability. At high-monomer concentrations, the graftability is higher in the swollen samples than in the beaten samples. 

Here KP is the propagation rate constant, catalyst effective surface, C the monomer concentration near the catalyst surface, and Na the surface concentration of propagation centers. 

The steady-state polymerization in the presence of Cr (it-CsHb) was first order with respect to the monomer concentration (125) the effective activation energy was 4.7 0.5 kcal/mole. When the concentration of Crfir-CaHs was varied, first a linear rise of the polymerization rate occurred with an increase of tris-ir-allylchromium concentration to the upper limit then the rate does not depend on Crfx-CaHs concentration (126). The value of the upper limit of the polymerization rate increased with an increase in the water content of the solvent used. 

Note that the value of Te is dependent on the monomer concentration. In the literature, values of Tc may be quoted for [M] = 1.0 M, for [M] = [ M et or for bulk monomer. Tints care must be taken to note the monomer concentration when comparing values of TK. One problem with using the above method to calculate fc. c or l c, is the paucity of data on ASp. A further complication is that literature values of AHP show variation of +2 kJ mol1 which may in part reflect medium effects. 77 This "error" in A//p corresponds to a significant uncertainty in Tc. 

---