Grafting parameters

The graft products are usually characterized by different methods. The first method is the calculation of graft parameters known as the grafting percentage (GP), grafting efficiency (GE), and weight conversion percentage (WC). These parameters can be calculated as follows ... 

P. Marmey, M.C. Porte-Durrieu, C. Baquey, PVDF multifilament yarns grafted with polystyrene induced by gamma-irradiation Influence of the grafting parameters on the mechanical properties, Nucl. Instrum. Methods Phys. Res. B 208 (2003) 429-435. 

The objective of this work was to optimize grafting parameters for hardwood pulp in general and aspen in particular. The monomer used was acrylonitrile. 

Extractions The apparent level of grafting, polymer loading and conversion was determined by Soxhlet extraction using dimethyl formamide. The oven dry weight was corrected for pulp lost in the mercerization step. Grafting parameters were defined as follows ... 

A quantitative method has been developed to separate free and graft copolymers in an ABS sample. The ABS powder is dispersed in MEK and then introduced into the cells of a preparative ultracentrifuge. After the reproducibility of the procedure was ascertained, the method was used to determine the grafting parameters of samples polymerized under specific conditions. This analytical technique is well suited to demonstrate how the grafting efficiency or grafting density is influenced by various polymerization conditions such as mercaptan content, monomer flow rate, emulsifier content, or polybutadiene content. The effects of other variables such as temperature, the initiator system, and characteristics of the polybutadiene latex can also be demonstrated. 

Our separation technique was used to determine the grafting parameters of an ABS sample prepared in our laboratory to check the reproducibility of the method. 

Application—Influence of Polymerization Conditions on Grafting Parameters... 

Effect of Mercaptan Content. In the polymerization recipe, TDM is used as a transfer agent. It is interesting to know how each grafting parameter depends on this agent. The experimental results are presented in Table III and Figure 1. As the TDM content increased from 0.0 to 0.6, G decreased from 47 to 23%, Gd decreased from 160 to nearly 0%, Ge decreased from... 

Effect of the Monomer Flow Rate. The rate at which the monomer mixture is introduced into the reactor greatly affects the grafting parameters. As the time for introduction was increased from 0 to 20 hrs, we observed (see Table IV and Figure 2) that G increased from 21 to 43%, Gd increased from 5 to 100%, Gc increased from 1 to 25%, and rjr decreased from 0.75 to 0.43. When the monomer flow rate decreases, the monomer concentration in the polymer phase increases as does the probability for grafting. Thus, the variations in G, G(h and Ge can be explained easily. 

EVAc grafted with MA styrene CRNl + SSE Study of the grafting parameters Sakai et al., 1988... 

Grafting parameters (irradiation dose, monomer concentration, grafting medium, temperature, etc.) have significant influence not only on grafting yield and grafting kinetics but also on resultant film and membrane properties. Crosslinkers are used in conjunction with the monomer to achieve certain desirable properties. For instance, the use of crosslinker is an effective means of enhancing the stability of styrene-grafted membranes in fuel cells. 

Fig. 5.2 are used to further improve the chemical stability of PCMs. The degree of grafting calculated from the weight increase after grafting is a function of grafting parameters (e.g., monomer concentration, dose, dose rate, solvent, and temperature) and grafting follows the front mechanism, where it starts at the film s surfaces and moves progressively inward with successive monomer diffusion [24,25,27]. 

G.S. Chauhan, S.K. Dhiman, LK. Guleria, and I. Kaur, Polymers from renewable resources Kinetics studies of the radiochemical graft copolymerization of styrene onto cellulose extracted from pine needles and the effect of some additives on the grafting parameters in an aqueous medium, 7. Appl. Polym. Sci. 83 1490-1500,2002. 

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