Methyl methacrylate latex particles

Fig. 13.5. The osmotic pressure of poly(methyl methacrylate) latex particles sterically stabilized by poly(12-hydroxystearic acid) in n-dodecane as a function of the volume fraction of latex (after Cairns el al., 1976).

Figgre 7 Structure of dispersion of poly (methyl methacrylate) latex particles (diameter 0.53 p,m) in benzene, (a) The measured structure factor is plotted against the wave-number K. (b) The total correlation function h(r) obtained by Fourier transformation is plotted against separation r. The dashed line represents the expected behaviour of h(r) at low r (Redrawn from ref. 68). 

Paxton, T. R., Adsorption of emulsifier on polystyrene and poly(methyl methacrylate) latex particles, J. Colloid Interface ScL, 31, 19-30 (1969). 

Figure 3.5 Experimentally determined fractions of methyl methacrylate in the droplet phase as a function of the fraction of methyl methacrylate in different latex particles. Methyl methacrylate and styrene in polybutadiene (open circles), SMMA-free (open squares), SMMA-graft (open triangles) from polybutadiene-graft-poly(styrene-co-methyl methacrylate) latex particles, while the closed squares represent a poly(styrene-co-methyl methacrylate) latex swollen with styrene and methyl methacrylate. The solid line gives the theoretical prediction according to Equation 3.13.

In an effort to estimate the magnitude of the decrease in sedimentation rate due to interparticle interactions, several poly (methyl methacrylate) latexes (PMMA) were prepared since PMMA particles are too hard for expansion to occur at low acid levels. Thus surface charge can be adjusted in the absence of expansion. 

Swelling of polymethyl methacrylate latex particles with methyl methacrylate. Table IV lists the swelling ratios and interfacial tensions for the different-size polymethyl methacrylate latexes with added Aerosol MA and sodium dodecyl sulfate emulsifiers. Comparison of the data with the theoretical curves from Model I (Figure 2) defines an apparent interaction parameter of 0.45 and the semi-empirical equation ... 

Figure 5.2 presents a similar plot for a poly(methyl methacrylate) latex sterically stabilized in n-heptane by poly(12-hydroxystearic acid). In this instance, however, the reduction in the solvency of the dispersion medium for the stabilizing moieties was achieved by adding a miscible nonsolvent (specifically ethanol) to the dispersion medium (Napper, 1968a). Flocculation was again accompanied by an abrupt increase in turbidity when a certain volume fraction of ethanol was added to the ra-heptane. In this instance, it was possible to observe the slow flocculation of the latex particles (i.e. flocculation apparently in the presence of a small repulsive potential energy barrier at a rate slower than that predicted by Smoluchowski, 1917). It is, however, usually diflicult to detect such slow flocculation because of the sharpness of the transition from stability to flocculation for stericaUy stabilized dispersions. 

Conductometric analysis of some latexes leads to the conclusion that most of the polymerized acid ends up on the surface of the particles while in other systems a majority of the acid is not titratable and is assumed to be buried within the particles. For instance, conductometric titrations of the three latexes described in Figure 12 showed that greater than 90% of the acrylic acid added in the polymerization was associated with the particles and titratable. On the other hand, polystyrene and poly(methyl methacrylate) latexes generally yielded conductometric results showing a considerable fraction of the acid buried (31). Since, at the levels of incorporated acid studied, the PST and PMMA latexes did not expand upon raising the pH, it could be argued that in the acrylic case (Fig. 12) all the acid was detected because the particles expanded to bare previously buried groups. But poly(butyl acrylate) latexes were found to exhibit no expansion when neutralized with base, and conductometric titrations showed that most of the acid added in the polymerization was detected on the particles (39). 

Pressure versus volume fraction for compression of sterically stabilized poly(methyl methacrylate) latex core diameter of particles = 155 nm. From Cairns et at. [47]... 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

Methyl methacrylate-grafted latex rubber particles has been studied for the impact toughening of PS styrenic matrix polymers. The... 

Most ABS is made by emulsion polymerization. A polybutadiene or nitrile rubber latex is prepared, and styrene plus acrylonitrile are grafted upon the elastomer in emulsion. The effect of rubber particle size in ABS graft copolymer on physical properties is the subject Chapter 22 by C. F. Parsons and E. L. Suck. Methyl methacrylate was substituted for acrylonitrile in ABS by R. D. Deanin and co-workers. They found a better thermoprocessability, lighter color, and better ultraviolet light stability. 

Figures 4A and 4B are the ultra-thin cross-sections of OsOi+-stained two-stage (styrene//styrene-butadiene) and (styrene-butadiene/ /styrene) latex particles at the stage ratio of 50/50 (LS-10 and LS-11), respectively. Latex samples were mixed with a polymerizable monomer mix of butyl and methyl methacrylates, cured, and microtomed for examination. Figure 4A shows particle cross-sections much smaller than the actual particle size of LS-10. It appears that since the embedding monomer solution was a solvent for polystyrene, the continuous polystyrene phase was dissolved and small S/B copolymer microdomains were left behind. This is further evidence that the second-stage S-B copolymers phase-separated as microdomains within the first-stage polystyrene phase, as shown in Figures 1A and 1A. Figure 4B shows somewhat swollen and deformed particle cross-sections, suggesting that the first-stage cross-linked S-B copolymers were a continuous phase. Indeed, the former (LS-10) behaved like a hard latex, but the latter (LS-11) behaved like a soft latex.

Figure 4. Ultrathin cross sections of OsO,-stained two-stage (S//S-B) and (S-B// S) latex particles at the stage ratio of 50/50, respectively, embedded in a polymerizable mix of butyl and methyl methacrylates ((A) LS-10, (B) LS-11 (reverse of...

Synthesis. A series of latexes was prepared by semicontinuous emulsion polymerization of methyl methacrylate. A dialkyl ester of sodium sulfosuccinic acid surfactant yielded the narrow particle size distribution required. An ammonium persulfate/sodium metabisulfate/ferrous sulfate initiator system was used. The initiator was fed over the polymerization time, allowing better control of the polymerization rate. For the smaller size latexes (200 to 450 nm), a seed latex was prepared in situ by polymerizing 10% of the monomer in the presence of the ammonium persulfate. Particle size was adjusted by varying the level of surfactant during the heel reaction. As the exotherm of this reaction subsided, the monomer and the sodium metabisulfate/ferrous sulfate feeds were started and continued over approximately one hour. The... 

Turbidity measurements are simple, fast and reproducible. Specific turbidity can successfully follow the particle size evolution during the course of emulsion polymerization and can be translated into weight average diameters. A combination of an on-line spectrophotometer with an on-line densitometer (to obtain concentration) would provide the potential to estimate Dw on-line, as well. An on-line determination of PSD s, for small particles however, would seem quite difficult due to the high correlation of their parameters. One should bear in mind that the above conclusions have been validated only for poly(vinyl acetate) latexes the analysis is currently being extened to other systems, such as polystyrene and poly(methyl-methacrylate). 

Polymerizable surfactants capable of working as transfer agents include thiosulfonates, thioalkoxylates and methyl methacrylate dimer/trimer surfactants. Thioalkoxylates with 17-90 ethylene oxide units were produced from ethoxylated 11 bromo-undecanol by replacing the bromine with a thiol group via the thiazonium salt route [8]. In the presence of water-soluble azo initiator the thio ended Transurfs (used at a concentration above the CMC) gave monodispersed latex particles in emulsion polymerization of styrene. However, the incorporation of the Transurf remained low, irrespective of the process used for the polymerization (batch, semibatch, seeded). The stability of the lattices when the surfactant and the transfer function were incorporated in the same molecule was better than when they were decoupled. 

Since these rubber particles are highly filled with a homopolymer or a copolymer, the rubber is already reinforced with a resin to give a higher modulus particle than the grafted rubber latex. On the basis of the uniqueness of these rubber particles, this process is also more appropriate in manufacturing high-strength medium-impact ABS polymer (31), or rubber-reinforced styrene-methyl methacrylate copolymer (32). The... 

In a related patent (46) Amagi et al. synthesized a triple latex IPN. In brief, polymer 1 was a crosslinked SBR, polymer 2 was a crosslinked styrene-methyl methacrylate copolymer, and polymer 3 was a crosslinked poly (methyl methacrylate). All three were sequentially synthesized on the same latex particle. The latex material was then mechanically blended with linear poly (vinyl chloride). Also, Torvik (47) blended together four polymers that had different glass transition temperatures. 

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