Latex particle size

PVA and TaM -for the 88%-hydrolyzed PVA. The same dependence was found for the adsorbed layer thickness measured by viscosity and photon correlation spectroscopy. Extension of the adsorption isotherms to higher concentrations gave a second rise in surface concentration, which was attributed to multilayer adsorption and incipient phase separation at the interface. The latex particle size had no effect on the adsorption density however, the thickness of the adsorbed layer increased with increasing particle size, which was attributed to changes in the configuration of the adsorbed polymer molecules. The electrolyte stability of the bare and PVA-covered particles showed that the bare particles coagulated in the primary minimum and the PVA-covered particles flocculated in the secondary minimum and the larger particles were less stable than the smaller particles. 

The investigations include the effect of (i) PVA molecular weight, particularly at higher concentrations which give different adsorption isotherms (ii) latex particle size over the range 190-llOOnm using a low-molecular-weight fully-hydrolyzed PVA (iii) electrolyte on bare and PVA-covered particles of different sizes. 

Effect of PS Latex Particle Size on PVA Adsorption. Figure 5... 

Effect of PS Latex Particle Size on Adsorbed Layer Thickness. Figure 6 shows the variation of reduced viscosity with volume fraction for 190, 400, and HOOnm-size bare and PVA-covered PS latex particles. The viscosity variation of the different-size bare particles was the same, with an Einstein coefficient of ca. 3.0. The... 

The adsorbed layer thickness for the llOOnm-size particles could not be measured by photon correlation spectroscopy because of the lOOOnm upper limit of this instrument. Again, the agreement between the two methods is excellent. It is interesting that the adsorbed layer thickness increases with increasing latex particle size and that these values vary with the 0.5 power of the particle radius, i.e., where R is the particle radius. This re-... 

The results showed that all batch polymerizations gave a two-peaked copolymer compositional distribution, a butyl acrylate-rich fraction, which varied according to the monomer ratio, and polyvinyl acetate. All starved semi-continuous polymerizations gave a single-peaked copolymer compositional distribution which corresponded to the monomer ratio. The latex particle sizes and type and concentration of surface groups were correlated with the conditions of polymerization. The stability of the latex to added electrolyte showed that particles were stabilized by both electrostatic and steric stabilization with the steric stabilization groups provided by surface hydrolysis of vinyl acetate units in the polymer chain. The extent of this surface hydrolysis was greater for the starved semi-continuous sample than for the batch sample. 

An ICI-Joyce Loebl Disc Centrifuge MK III, a photosedimento-meter, was used to measure the latex particle size distribution. The latex had a unimodal particle size distribution with a diameter of 1.05 micrometers (surface area average). The methods of separating latex particles by a centrifugal field and detecting the size distribution by a photocell may be found in the literature. 

Latex Particle Size, nm Surface Charge Density (sulfate group), yc/cm2 Electrophoretic Mobility in Deionized Water ym cm/sec volt... 

The polystyrene seed latex was monodispersed. Even after several grow-ups (polymerizations) the final 1650 A latex was monodispersed. Hydrodynamic chromatography on the 1650 A latex gave a mean diameter of 1660 a with a size variance as small as for normal polystyrene latex standards (typical standard of 1760 8 with a standard deviation of 23 a). The final latex particle size could be accurately predicted from the initial particle size and the total amounts of monomer and polymer used. 

Chang, K., Litt, M., and Jamieson, A. M., "The Measurement of Latex Particle Size by Quasielastic Laser Light Scatter-ing", J. Poly. Sci.-Phys., to be published. 

Latex particle sizes and polydispersity were measured by use of an ICI Joyce Loebl disc centrifuge (JLDC) photosedimentometer (11,12). 

Hopefully, it has become evident that specific turbidity gives consistent and reproducible qualitative results. Two approaches have been used to translate the specific turbidity measurements from the previously mentioned experiments into latex particle size ... 

Particle size distribution of a latex has a pronounced influence on its rheological properties, storage stability, and film forming capabilities Q ). In addition, latex particle size distributions provide information on polymerization mechanisms and kinetics (2), and provide a means of polymerization control (3,4). 

Final sample concentrations ranged from 0.05% to 1.0% (by weight), depending on latex particle size, In order to generate chromatographic signals in the linear range of the detector. Diluted samples were placed in a low power ultrasonic bath (Ultrasonics, Plainview, New York) for 60 seconds just prior to injection. Peak areas were determined for each injection. Each sample was injected until three consecutive areas differed by less than two percent from one value to the next. 

The results reported herein indicate that hydrodynamic chromatography is an accurate, reproducible technique for latex particle size distribution analysis. Typical analysis requires 15-20 minutes to complete and reproducibility is generally better than 5% for both reported particle size and mass percent. Latex particle size distributions found using HDC provide useful information about end use performance of many types of material (see Table V). 

Figure 1. S/B latex particle-size distribution via HDC. with permission from Ref. 11. Copyright 1983 Tappi J.

Figure 8. Multi-component latex particle-size distribution.

We used a matrix copolymer system consisting of methyl methacrylate (MMA) and styrene (St) grafted on polybutadiene rubber. The variables investigated were latex particle size (360, 2000, and 5000 A), degree of grafting, rubber content, and the degree of particle dispersion. The following variables must be considered when a transparent impact polymer is prepared. 

Latex Particle Size and Grafting. The bulk of the program involved the preparation of monodisperse, polybutadiene latexes of 360, 2000, and 5000 A particle sizes and the grafting of these latexes with methyl methacrylate/styrene. 

Table VIII lists the parts of graft per 100 parts of rubber for some laboratory runs as well as the latex particle size and tensile impact. The correlation of the degree of grafting to tensile impact still holds—i.e., within each latex system the higher the degree of grafting, the greater the impact. This condition however does not hold from latex to latex. A higher level of graft in one latex does not necessarily produce a higher...

Run No. Latex Particle Size, A Tensile Impact, ft-lb/in Parts Graft per 100 Parts Rubber... 

The physical significance attached to the a1 and a2 dimensions in this study is identical to that which we obtained for a series of MBAS impact plastics (2) containing butadiene rubber where rubber latex particle size was determined independently. We found that both laser light scattering and electron microscopy results agreed. 

Determination of Latex Particle Size from Polymerization Rates... 

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