Emulsion polymerization 958 INDEX

Symposium on Emulsion Polymerization —Pref. Includes bibliographies and index. 

Figure 1. Polydispersity index of the polymer produced in Interval II of an emulsion polymerization terminated solely by combination as a function of the average number of free radicals per particle...

Displayed in Figure 3 are the results for the polydispersity index for an emulsion polymerization system in which chain stoppage occurs by a combination of chain transfer ( tr= 1 reciprocal time unit) and disproportionation (c = 100 reciprocal time units). These results were obtained by varying p and thus n. The results suggest how it might be possible to tailor a distribution to some desired polydispersity index. 

The experimental results on the polymer produced in emulsion polymerizations published thus far are both confusing and contradictory. Several factors may be responsible for this first, many surfactants behave as chain transfer agents, which has often not been recognized second, measurements have often been made on samples that contain polymer from Intervals I, II and III, which leads to a significant increase in the polydispersity index becauseis sensitive to the presence of lower molecular weight species tRird, direct measurements of the MWD have only recently become possible with the advent of gel permeation chromatography. 

Theoretical considerations indicate that compartmentaUzation of radicals in polymer particles does not change the polydispersity index PDI(— in emulsion polymerization... 

Styrene in water without surfactant. Although the polydispersity indexes for the synthesis of the polyNaSS macroalkoxyamine were rather low (1.2 < PDI < 1.3), no data were provided concerning the polymerization. The same observation can be made for the kinetic and macromolecular characteristics of the emulsion polymerization. Stable dispersions were obtained, but the solid content did not exceed 5wt%. The particle size distributions were quite broad and within the 50-200nm range. 

Chem. Descrip. Lauryl-myristyl methacrylate, MEHQ stabilizer Uses Emulsifier, dis rsant for emulsion polymerization monomer for mfg. of methacrylate polymers/copolymers, lymers us as oil additives, vise, index improvers, pour pt. depressants internal plasticizer for adhesives, UV-curable resins, ar waterproofing coatings Properties Pale yel. liq. sp.gr. 0.9 flash pf. 80 C add no. 0.15 max. hyd. no. 12 max. 

Chem. Descrip. Polyalkyl methacrylate polymer in hydrocarbon oil Uses Vise, index improver for formulation of high vise, index hydraulie fluids emulsifier, dispersant for emulsion polymerization reaetive diluent for adhesives and eoatings... 

Uses Emulsifier, thickener, wetting agent, dispersant, solubilizer, stabilizer for cosmetics and pharmaceuticals demulsifier in petrol, industry detergent ingred. antistat for polyethylene and resin molding powds. metal treatment emulsion polymerization surfactant in latex-based paints, aq.-based syn. cutting fluids and vulcanization of rubber Properties Colorless liq. m.w. 5500 ref. index 1.4613 water-sol. sp.gr. 1.04 vise. 850 cps HLB 15 cloud pt. 65 C (1%) pour pt. 18 C surf, tens. 40.3 dynes/cm (0.1%) nonionic 100% act. 

Properties Wh. waxy solid partially sol. in alcohol, chloroform, ether pract. insol. in water m.w. 242.27 dens. 0.8176 (49.5 C) m.p. 49.3 C b.p. 344 C acid no. < 2 iodine no. < 5 hyd. no. 218-238 flash pt. > HOC ref. index 1.4283 surface-active dispersant, wetting agent, and compatibility aid for enhancing color acceptance in high solids coatings (alkyds, epoxies, UV and EB-cured coatings) emulsifierfor emulsion polymerization... 

Properties M.w. 210.32 dens. 0.930 m.p. -15 C b.p. 79 C (1 mm) flash pt. (CC)208 E ref. index 1.4560 Toxicology Irritant possible sensitizer TSCA listed Uses Monomer for prod, of paints/coatings, adhesives, sealants, lubricant additives, photographic reproductive toners, water treatment and textile chems. solution/emulsion polymerization and copolymerization Manuf./Distrib. Aldrich... 

Properties M.w. 170.21 dens. 1.044 b.p. 52 C (0.4 mm) flash pt. 90 C ref. index 1.4580 Uses Acrylic resin comonomer anaerobic adhesives and sealants printed circuit boards cosmetics artificial finger nails modifier for hard rubber rolls wire and cable coatings screen printing inks emulsion polymerization plastic modifier EB-curable coatings reactive diluent for hot-melt prepregs and adhesives Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, CPS Monomer-Polymer 8i Dajac Labs Polysciences... 

Rieger and coworkers [332] reported a surfactant free RAFT emulsion polymerization of butyl acrylate and styrene using poly(A,iV-dimethylacrylamide) trithiocarbonate macromolecular transfer agent. They observed that the polymerizations were fast and controlled with molar masses that matched well the theoretical values and low polydispersity indexes. Monomer conversions close to 100% were reached and the polymerizations behaved as controlled systems, even at 40% solids contents. The products were poly(lV,lV-dimethyl acrylamide)-b-poly(/i-butyl acrylate) and poly(Al,Al-dimethylacrylamide)-b-polystyrene amphiphilic diblock copolymers formed in situ. 

Monomer conversion can be adjusted by manipulating the feed rate of initiator or catalyst. If on-line M WD is available, initiator flow rate or reactor temperature can be used to adjust MW [38]. In emulsion polymerization, initiator feed rate can be used to control monomer conversion, while bypassing part of the water and monomer around the first reactor in a train can be used to control PSD [39,40]. Direct control of surfactant feed rate, based on surface tension measurements also can be used. Polymer quality and end-use property control are hampered, as in batch polymerization, by infrequent, off-line measurements. In addition, on-line measurements may be severely delayed due to the constraints of the process flowsheet. For example, even if on-line viscometry (via melt index) is available every 1 to 5 minutes, the viscometer may be situated at the outlet of an extruder downstream of the polymerization reactor. The transportation delay between the reactor where the MW develops, and the viscometer where the MW is measured (or inferred) may be several hours. Thus, even with frequent sampling, the data is old. There are two approaches possible in this case. One is to do open-loop, steady-state control. In this approach, the measurement is compared to the desired output when the system is believed to be at steady state. A manual correction to the process is then made, based on the error. The corrected inputs are maintained until the process reaches a new steady state, at which time the process is repeated. This approach is especially valid if the dominant dynamics of the process are substantially faster than the sampling interval. Another approach is to connect the output to the appropriate process input(s) in a closed-loop scheme. In this case, the loop must be substantially detuned to compensate for the large measurement delay. The addition of a dead time compensator can... 

Molecular weight distributions of the seed poly(BuA) latex (Mn,sEc = 5 900g- moP ) prepared by RITPand of the block copolymer latex poly(butyl acrylate)-bock-poly(styrene-co-butyl acrylate) (M sec = 53 400 g-moP ) prepared by seeded emulsion polymerization at 85 °C ( ) refractive index detector (seed latex), (O) UV detector at 254 nm (copolymer latex), (A) refractive index detector (copolymer latex). Seed [ACPA]/[IJ = i.6, [SDS] = 0.15 X CMC, targeted Mn = 2500 g mol, conversion =40%, particle diameter = i27 nm Block copolymer second monomer = styrene Monomerpee[Pg.165]

The kinetic behavior in each segregated entity can be different in view of die random nature of exit and entry phenomena and the nanometer scale of these identities, that is, a deviation from bulk kinetics ( one big droplet ) is to be expected. Hence, for emulsion polymerization, it is crucial to track the number of low-abundant (radical) species per segregated entity, as compartmentalization of radical species may influence the overall kinetics and thus the development of the polymer microstructure. If u radical types are present, this implies the calculation of the number of segregated entities characterized by u indices, with each index reflecting the discrete presence of one radical type. 

Fluorinated poly(methacrylates) or poly(acrylates), rich in trifluoromethyl groups, exhibit superior performance of chemical inertness, excellent weatherability, low refractive index, lower dielectric constant, and special surface properties [14,61]. Poly(2,2,2-trifluoroethyl methacrylate), poly(MATRIF), is an important class of such materials. It has been extensively used in high performance coatings [17], photoelectric communications, and microelectronics [62]. Poly(MATRIF) is easily produced by free radical polymerization using bulk, solution, and emulsion polymerization methods [63]. Structural characterization of NMR of poly(MATRIF) prepared by radical and anionic polymerization has been studied. Syndiotactic structure was obtained by radical initiator in contrast to an isotactic structure achieved by anionic polymerization [64]. 

Emulsion polymerization has been extensively studied in order to prepare quasi monodisperse polymer latex particles. Ding and coworkers employed Cj MelmCl as a surfactant in the emulsion polymerization of PS [24]. Monodisperse PS latex particles with average diameter of 126nm and extremely low polydispersity (index of 0.002) were obtained by using this process. When the concentration of Cj MelmCl... 

One of the issues when monitoring an emulsion polymerization reactor is selection of the most appropriate technique [124, 126]. For instance, monomer conversion and copolymer composition can be monitored on-line by means of densim-etry, refractive index, gas chromatography, calorimetry, ultrasound, fluorescence, ultraviolet reflection, and other spectroscopic methods such as Raman, mid-range infrared, and near-infrared. 

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