Grafting temperature

Graft copolymerization of methylmethacrylate onto paper wood pulp using ceric ammonium nitrate as the initiator has been studied. Different experimental conditions have been used, including both water and water-organic solvent systems. The effects of composition of the grafting medium and grafting temperature on the grafting process are examined. 

Gamma-radiation 3 megarads in air. Redox catalyst 0.01% Fe2+. Grafting temperature 25 °C. 

Influence of Temperature. At a constant polymerization temperature of 60 °C the grafting temperature greatly affects the shape of the... 

Grafting Temperature Effect. Temperature can influence the reaction rates in different ways initiation, propagation, transfer, termination. For grafting reaction, the length and number of grafted chains depend on rate constant of these reactions. However for radiochemical grafting, the initiation rate is not temperature dependent (2, 3, 4). 

Experimental results show that at low grafting temperature (30°C) the solubility of grafted polymers is highly modified by butadiene-acrylonitrile chains. Precipitation curves look like those of polymers prepared using dichloroethane and therefore seem compatible with a less cross-linked BD-AN chain structure. At high grafting temperature (70°C), the precipitation curve resembles that obtained with DVB crosslinked copolymers. 

Grafting Conditions Cellulose nitrate - 6 g Time - 75 min. [MMA] - 0.25 mol/1 Total volume - 300 ml Grafting temperature -30°C. (Reprinted with permission from reference 19.)... 

The extent of inhibition and retardation depends on the amount of added lignin, the initiator used and the grafting temperature. Lignin in-situ of the lig-nocellulosic substrate effects inhibition or retardation only on using ceric ammonium sulfate as initiator. 

The study of the influence of the grafting temperature and of reagent concentrations indicates that the amount of SAN grafted onto EPTM increases when mild conditions of reaction are adopted, i. e. low temperature, low concentration of initiator and monomers, but high concentration of EPTM and use of aromatic solvents. 

Figure 3.7 Change in specific resistance (Qcm) of a cation exchange membrane with degree of radiation-induced grafting of acrylic acid on a poly(tetrafiuoroethy-lene-perfiuoroalkylvinyl ether) film (prepared at various temperatures). Grafting temperature (A) 25 (X) 35 ( ) 45 (O) 60 °C.

Wirsen, A. and Albertsson, A.C. 1995. Graft polymerization of arcylamide onto LLDPE film by electron beam pre-irradiation in air or argon. I. Influence of dose, grafting temperature, and monomer concentration J Polym Sci Polym Chem. 33 2039-2048. 

Grafting Temperature = eO C Grafting Time = 5 hours Nitrogen Purged 50% Styrene / 50% Toluene... 

These observations are well in line with those of Rager [77]. The grafting studies were carried out at 50-85 °C and showed that the initial rate of grafting increases with the grafting temperature. 

It may be mentioned that the Tg plays an important role in the grafting process. If Tg is lower than the grafting temperature, the mobility of chains is very high. Under such circumstances, the probability of primary radical termination becomes dominant. The final DG as a result may decrease. However, it may be overshadowed by the faster rate of chain initiation and higher monomer diffusivity at higher temperatures [72], as shown in Fig. 6. As a matter of fact, a sharp increase in the rate of grafting may be envisioned at the Tg of the specific polymer. 

TABLES The effect of grafting temperature on the percentage of grafting, grafting efficiency, and weight conversion at constant conditions (6% Gelatin, 5% AM, 0.05% MBA, and 0.05%... 

Figure 3. Thickness (a, c) and water-contact angle (b, d) for the grafted (to PET/PGMA substrate) PEI (a, b) and PAA (c, d) layer as a function of grafting temperature. The samples were washed with methanol before the measurements. Time of the grafting 10 min and 1 hour.

Plotting Ln[M](/[M] = f(t) for low conversion rates, for each grafting temperature, a curve is obtained from which the slope of the origin tangent allows the calculation of fKd- The authors show that the influence of the monomer concentration at the beginning is not negligible, and it determines the reaction medium viscosity. Moreover, the grafting reactions are accompanied by the thermal homopolymerization reactions which have been taken into account by the authors in evaluation of their experiment and contribution to the monomer disappearance rate. 

Alginate Marine brown seaweeds and microorganisms Ions, pH, electrical field, surfactants, light (anthracene grafted) temperature (grafted with PNIPAAm), redox (if thiolated), and magnetic (with Fe304)... 

Hong, C.Y. You, Y.Z. Pan, C.Y. (2005). Synthesis of Water-Soluble Multiwalled Carbon Nanotubes with Grafted Temperature-Responsive Shells by Surface RAFT Polymerization. Chemistry of Materials, 17, 2247- 2254. 

C. Geismann, A. Yaroshchuk, and M. Ulbricht. Permeability and electro-kinetic characterization of poly(ethylene terephthalate) capillary pore membranes with grafted temperature-responsive polymers, tgmujr, 23(l) 76-83, 2007. 

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