Changes in degree of polymerization

In respect to its ability for degrading H3P04-swollen cellulose, Ci is similar to Cx, but the mode of attack clearly is different (Figure 2). Whereas Ci attacks from the end of the chain and produces little change in degree of polymerization, Cx attacks at random. Glucose, cellobiose, and cellotriose are found in the products of the action of Cx C i produces principally cellobiose, as would be expected from a cellobiohydrolase. 

Figure 5 Changes in degrees of polymerization and yields of higher plant cellulose during acid hydrolysis at 80-95°C.

Changes in degree of polymerization and copper number of cotton cellulose during cutting with a Wiley mill. 

Figure 2. Changes in degree of polymerization and copper number of cotton cellulose during milling with a Norton ball mill. Key Y, milled fiber V, O,...

The number of chain-scission events during thermal degradation is most readily determined by the change in degree of polymerization as a function of time. The number of chain scissions S t) at any time t per number-average molecule (M ) is given by the relation... 

One of the major consideration in polymerization reactors is that the viscosity of the solution changes with degree of polymerization, going from very low viscosity initially to a solid at complete polymerization. This means that tubular reactor must be used very cautiously for polymerization because the viscosity will increase, especially near the wall where the residence time is longest. Many of these fluids also have viscosities that are dependent on the shear rate. 

Comparison of Randomness of Ex-1 and Endocellulases on the Hydrolysis of CMC and Cotton. That Ex-1 is least random (as compared with S-l and F-l) on the hydrolysis of CMC and cotton was verified by the observations of the relationships between fluidity of CMC or the decrease in degree of polymerization (DP) of cotton and the simultaneous production of reducing power. These results are shown in Figures 16 and 17. Further, as shown in Figures 18 and 19, the difference in the hydrolysis patterns of both types of cellulase becomes more clear with the comparison between time-course patterns of changes in the viscosity of CMC by both Ex-1 and En-1. The latter is a typical endo-cellulase component as described relative to Figure 12. 

Some oxidation of the cellulose chains also seems to take place, suggested by the rise in HAS matter during exposure and by the initially rapid rate of change that occurred upon subsequent thermal degradation of the exposed papers. This represents the "potentially harmful" effect of exposure, leading to loss in degree of polymerization through thermally-induced reactions. These concepts are not new but the authors trust that a clear demonstration of the effects has been useful. 

Degradation—1. The decrease in degree of polymerization of polymer chains. 2. The negative change in physical properties or appearance of a polymer. 

Although the process of transfer usually leads to lower degree of polymerization with no change in rate of polymerization, that depends entirely on the reactivity of the new radical produced by transfer. If the latter is... 

The absence of a significant effect of the chain structure of the macromolecules on the twist elasticity constant K i was also found in [13] in studying the thresholds of untwisting of the cholestoic helix of comb-shaped copolymers of the acrylic series (Vm, IX). Changing the degree of polymerization within the limits of SO to ISO has almost no effect on the value of Kj2, [ (4-7) 10 dyne], which coincides in order of magnitude with the twist elasticity constants of low-molecular-weight nematic-cholesteric mixtures. 

Calculate the change in rate of polymerization and degree of polymerization by increasing the temperature of the polymerization of styrene in benzene initiated by AZBN from 60°C to 70°C given the following information. 

The family of curves consist of two straight-line portions, with a change of slope occurring at a degree of polymerization in the range 10 -10. ... 

Figures 4 and 5 show that the degree of polymerization and the intrinsic viscosity increase with increasing the comonomer concentration. Thus, the increase in the comonomer concentration would increase DP and, consequently [rj] Eq. (2). However, the exponent of the monomer concentration for the degree of polymerization decreases at a high comonomer concentration. The abrupt change in the exponent at comonomer concentration >2.1 M/L (Eq. 9) may be ascribed to polydispersity. This was found by others [34] to be at 2.1 and 2.2 M/L, although it starts theoretically at 2.0 M/L.

The molar rate of change of polymeric species of degree of polymerization n in a well-mixed, continuous flow tank reactor is related to the kinetic rate of propagation of unassociated polystyryl anions plus their withdrawal rate in the reactor s effluent. Feed streams are void of polymeric substances, but contain monomer initiator and solvent. 

As suggested by Barrett (2), it is assumed that following the particle nucleation stage, the polymerization proceeds in the particle (monomer/polymer) phase with no mass transfer limitation. Therefore, the dispersion polymerization is similar to a mass or suspension polymerization, and kj can not be assumed to be constant even at isothermal conditions, since kp and even kp are dependent on the degree of polymerization because of a gel effect. (2., ,D However, since the application of the model is for a finishing step, with polymer molecular weight and viscosity fairly well established, further changes in kp and kp should be minimal. 

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