Latex mixtures

P perApplications. In beater additions, the latex is mixed with the beaten paper pulp either by addition at the beater or to the stock chest at the wet end of the paper machine. In either case, the pH of the pulp is reduced to 4.0—4.5, usually by the addition of a solution of alum to the pulp—latex mixture which has been thoroughly agitated. The latex, which for this appHcation must be based on an anionic emulsifier, coagulates as the pH drops. The latex soHds separate ia intimate associatioa with the pulp fibers. The pulp is thea screeaed and the paper web formed ia the coaveatioaal way. A latex for this purpose must possess the proper balance between mechanical and chemical stabiHty. 

The upper part of Figure 4 shows the results of the rapid density gradient centrifugation of a latex mixture of poly(styrene) and two chemically uniform co-... 

A surfactant solution (titrant) is used to titrate L grams of a diluted latex (mixture) to produce the typical plot shown in Figure 2, in which v ml of titrant are required to reach the cmc. The mass of surfactant per gram of mixture at the cmc is... 

Figure 6 shows the separation of the latex mixture shown in Figure 5 including an additional 0.176pm polystyrene standard. In this case, the externally prepared spin fluid/density gradient consisted of 15 ml of water and 1 ml of methanol and the disc speed was 10,450 rpm. Baseline separation and peak resolution are obtained over a decade of size range in less than 25 minutes. 

The gradient-variation experiments described in the previous section were repeated with dodecane-protected gradients. Much shallower gradients gave stable sedimentation under these conditions. The latex mixture could be separated in a 0/1% gradient as well as in a 4/4.5% gradient. This confirmed that evaporative cooling of the spin fluid was the primary cause of convection and hence of unstable sedimentation. 

I 79 Methods of Evaluating Formulations after Dilution Latex mixture - volume / ... 

The influence of vibrowave treatment on the film properties obtained from latex mixtures has been studied as described elsewhere [2]. IR examination of latex films has been carried out by using PE 1600 FTIR instrument in the field of 400-4000 cm"1. 

Changes of time of the treatment and frequency in the considered limits (5-10 min. and 50-150 Hz, respectively) lead to less prononced effects (the confidential interval is 10 %). On the basis of the results gained, optimal compositions of latex mixtures and conditions of vibrowave stirring (ratio of latexes poly(butadiene-styrene) poly(butadieneacrylate) = 75 25 vol., duration of vibrowave stirring - 7,5 min., frequency-150 Hz) have been chosen. 

Figure 8.1. TEM micrographs of (a) ABS resin and (b) as-polymerized ABS latex by the OsO staining and fixation method [Kato, 1967]. In micrograph (a), polybutadiene phase is stained. SAN particles are occluded in the rubber particles. In micrograph (b), a latex particle is embedded in agar-agar/polybutadiene latex mixture and stained by OsO. The occluded SAN particles are clearly seen. Surface grafted SAN partly covers the salami particle.

Poly(styrene-co-butadiene) rubber and poly(acrylonitrile-co-butadiene) rubber latex mixture films were evaluated as precursors of polymer electrolytes. A 50 50 blend was the optimum for mechanical strength and ionic conductivity. A simple equivalent mechanical model for the relationship between the mechanical strength and the structure was developed, which gave good agreement with experimental results, including materials with co-continuous phase morphologies. 26 refs. 

Initially compounding was mainly performed between amorphous polymers and elastomers, resulting in a polymer matrix with small domains of elastomers. This morphology can increase the mechanical properties considerably. In later developments special attention was paid to better and controlled phase separation, to control the domain size, and to increase the impact strength, as for instance in high-impact polystyrene (HIPS) and in ABS-latex mixtures. The search for better compatibility between the phases leads also to fully compatible combinations of polymers. Although over 300 pairs of miscible polymers are known (2), only a few systems have actually been commercialized, like PS/PPE... 

The surface charge densities were determined by conductometric titration of the ion-exchanged latexes with sodium hydroxide (1,2). The solids contents of the latexes were measured by drying 1.5-g samples to dryness on a hot plate. The latex mixtures are listed in Table II. The number ratios of small/large particles were calculated from the weight of polymer and the number average volumes determined by electron microscopy. 

These emulsifiers, which are typical of those used in emulsion polymerization, were added to the latexes or latex mixtures in various concentrations. All emulsifiers were used as received. 

Latex mixtures I and II were ion-exchanged with AMBERLITE Monobed MB-1 resin 200 g of 0.2% solids latex was shaken with 20 g resin in the separatory funnel and sampled at 16, 24, and 40 hours. Figure 1 shows the electron micrographs for mixture I. The proportion of the smaller particles decreased steadily with shaking time so that only a few were seen at 24 hours. The larger particles were visible at all times, but were aggregated to a greater extent at 40... 

The foregoing latex mixtures were subjected to ultrasonic irradiation after ion exchange to determine if this treatment affected the degree of dispersion no significant differences were found, and the appearance of the electron micrographs and the number ratios of small/large particles were similar to those reported above for the nonirradiated samples. 

Effect of Ion Exchange with AMBERLITE Monobed MB-1 on the Particle Size Distribution of Latex Mixtures... 

Figure 1. Electron Micrographs Showing the Effect of Ion-Exchange Contact Time on the Particle Size Distribution of Latex Mixture I A. none (original) B. 16 hrs C. 24 hrs D. 40 hrs,...

Figure 4. COULTER COUNTER analysis of a 8,3/18,6/45,2 /im latex mixture using a 100 (a) and 200 urn (b) orifice.

Separated peaks for each latex standard were obtained. Measurements of the individual latex samples resulted in identical fractograms for the corresponding latex sample. For the measured analyte loads between 0.5 and 2.5 mg, no sample overloading effect and no significant adsorption of the sample on the membrane was observed, which would be deterted by, for example, a distorted analyte peak or a shift in the position of the peak maximum. " " Employing an analyte load of 10 mg of the latex mixture results in a comparable fractogram. 

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