Weight fraction, styrene polymers

A mathematical model for styrene polymerization, based on free-radical kinetics, accounts for changes in termination coefficient with increasing conversion by an empirical function of viscosity at the polymerization temperature. Solution of the differential equations results in an expression that calculates the weight fraction of polymer of selected chain lengths. Conversions, and number, weight, and Z molecular-weight averages are also predicted as a function of time. The model was tested on peroxide-initiated suspension polymerizations and also on batch and continuous thermally initiated bulk polymerizations. 

Off-Line Mw Measurements in Several Solvents. Table 1 shows results oT din/dc (column 3T and off-line Mw measurements (column 6) which were carried out in THF, toluene, and chloroform. The dn/dc also was calculated via Equation lb using the weight fraction of each monomer (from proton NMR, "Experimental") and the dn/dc for the corresponding homo polymers. Values of the homopolymers in THF styrene (0.190), isoprene (0.127), butadiene (0.132) toluene styrene (0.108), isoprene (O.O3I), butadiene (0.032) chloroform styrene (0.155), isoprene (0.093), butadiene (0.094). Values of dn/dc derived in this manner are presented in column 4. 

PS/S-MMA-25. Putting 25-wt% styrene into the host polymer makes it compatible in all proportions with PS-600 and compatible to substantial weight fractions with the PS-2100 and PS-4000 (Figure 1). 

Fig. 20. Plot of conversion and weight fraction of the polymer formed in the interior of the gel as a function of the SDS concentration (water 2 ml, styrene 30 ml, 45 °C, 18 h)...

F7-21g Sketch the polypiet concentration, Pj, mole fraction of polymer with j monomer units, yj, and the corresponding weight fraction, Wj, for j = 2, 10, 30 as a function of monomer conversion in Styrene polymerization for (a) Termination by means other than combination. 

The compositions of most acrylic and styrene-acrylic emulsion polymers contain from one to three principal building-block monomers (which generally make up over 90% by weight of the backbone) and one or more of the auxiliary or specialty monomers. The building-block monomers mainly determine the hardness (Tg) and hydrophobicity of the polymer. Styrene and the acrylic monomers form amorphous, random copolymers with a Tg that is roughly proportional to the weight fractions and Tg s of the component monomers. Several mathematical equations have been proposed to describe correlations between Tg s and copolymer composition. Perhaps the most well known is the Fox equation [28] ... 

A remarkable special property of nitrate esters is the ability to catalyze some additional polymerization reactions [42]. In nitroglycerine, both styrene and methyl methacrylate can be self-polymerized. If the amount of nitroglycerine is up to 5-20 portion (weight fraction), equals to 10 % of polymers, the polymerization rate will be fastened. The molecular weight of polymers is less than that obtained through slowly polymerization or in situ anionic polymerization. 

Concentration and molecular weight dependences of and Pp for molecular weight P probes in solutions of molecular weight M matrix polymers (for Ps, one has P = M) at concentration c. The fits are to stretched exponentials ><,P exp(—ac P M ), with the percent root-mean-squEire fractional fit error %R, the material, and the reference. Molecular weights are in kDa concentrations except as noted are in g/L. Square brackets ] denote parameters that were fixed rather than floated. Notes (a) Various, with M/P > 10 (b) Various, see text (c) All four probes, see text (d) Excluding styrene monomer, see text (e) Not all data points, see text (f) P = M, self diffusion. 

In blends of random copolymers, or in blends of a polymer with random copolymer, the presence of repulsive forces among segments (other than specific interactions discussed before) may lead to miscibility (Wang et al. 2006). The effect of ethylene-styrene cmitent on the miscibility and cocrystallization was studied extensively by Chen (2001). They showed that the miscibility of the system depends only oti the comonomer content with composition expressed as weight fraction. Based on the experimental observations, they constructed a miscibility map for binary blends (Fig. 10.34). 

Figure 3.63. Dependence of Y on Uie polymer critical concentration (in mole fractions 2 = 1/(1 + luoA/m/iap), where luo and lUp are the masses of the solvent and polymer, respectively, Mm is the moleculeir weight of styrene) (a). Temperature dependence of % (b). Polystyrene+cyclohexane system (Koningsveld, 1970b Koningsveld et al., 1970b) [Reprinted with permission from K.Koningsvcld. Oise. Faraday Soc. 49 (1970) 144-161. Copyrighted 1970 by the Royal Society of Chemistry]...

TEC is a useful technique for separating polymers into molecular weight fractions on a fairly small scale. It has been used to fractionate PET [135, 136], styrene-butadiene copolymers [137], styrene acrylonitrile copolymers [138], polyoxypropylene glycols [136], Nylon-styrene graft copolymers and PMMA [139-141], styrene-methacrylate copolymers [142], poly-a-methylstyrene [143], polyvinyl acetate-styrene copolymers, and polyvinyl alcohol-styrene copolymers [144]. 

A range of polymer blends were investigated by Kirste et al. who found that most of the systems under investigation had positive Ai values. Only blends of polystyrene-acrylonitrile copolymer with differing styrene weight fractions were found to have. >4 2 less than zero. This would lead to phase separation at a sufficiently high molecular weight in these blends. 

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