Carboxylic measuring particle

FIG. 4 tt-A isotherm of carboxylated latex particles on aqueous subphase, it measured using a WU-helmy balance. (Data taken from Ref. 155.)... 

Techniques for Measuring Particle Swelling of Carboxylic Emulsion Polymers... 

The expansion characteristics of carboxylic latex particles have been measured using three independent techniques sedimentation, which uses the change in particle density due to swelling to determine the change in particle size viscometry, which measures volume changes and photon correlation spectroscopy, which measures the diffusion coefficient of the particles. The sedimentation technique offers precise measurements at low shear but requires relatively... 

The results are generally consistent with a broader treatment of the techniques for measuring particle swelling of carboxylic emulsion polymer latexes reported elsewhere in this Monograph (9). The broader study, which was carried out independently but concurrently, has shown that the magnitude and pH of maximum expansion depends on dilution and ionic strength. Studies of the concentration dependence in the dilute regime and more concentrated systems are underway. 

The expansion behavior of carboxylic latex particles can be studied by several methods (10). The present comparison was made using a sedimentation method which involved the measurement of particle sedimentation rates in an ultracentrifuge at various degrees of neutralization. Assuming the change in particle volume is equal to the volume of water absorbed, an expanded particle settles slower, as its density decreases, according to the equation ... 

Pyrene carboxaldehyde and a series of pyrene carboxylic acids were found useful as fluorescence probes in describing the constitution of inverted micelles of certain calcium alkarylsulfonates in hydrocarbon media. 1-Pyrene carboxaldehyde is a convenient probe for studying the particle sizes of micelles in the region of lOOA. A series of graded probes, pyrene carboxylic acids with varying alkyl chain length, have been used to determine internal fluidity and micro-polarity as a function of distance from the polar core of these Inverted micelles. Pyrene exclmer to monomer fluorescence intensity ratio and fluorescene lifetime provided the means of measurement of internal fluidity and micropolarity, respectively. 

A variety of dicarboxylic acids have been measured in air, including, for example, oxalic acid [(COOH)2], succinic acid [HOOCCH2CH2COOH], and malonic acid [HOOCCH2COOH], as well as larger straight-and branched-chain carboxylic acids unsaturated and aromatic acids such as phthalic acid are also observed in smaller concentrations (e.g., see Kawamura et al., 1996a, 1996b). Because of their lower vapor pressures, they are found predominantly in particles (see Chapter 9). 

Central to any investigation of particle swelling is the use of a reliable method of measuring the size of the particles undergoing expansion. A sedimentation method was described previously (5) which can be used to explore the expansion characteristics of carboxylic emulsion polymers. In the present report, we present a comparison of sedimentation results with those obtained with two... 

Photon correlation spectroscopy, carried out under very dilute conditions, has unambiguously demonstrated the expansion of carboxylic emulsion polymers at high pH, but it may not always be useful in predicting properties of practical interest. Of special concern is the apparent decrease in the intrinsic ionization constant of surface carboxyls at very low concentration. Since most uses of emulsion polymer occur at high concentrations, the measurement of particle-particle interactions is of great practical importance (21J. It has been found that the sedimentation and viscometric techniques closely reflect viscosity changes in latexes at much higher solids. Extension of the PCS approach to more concentrated systems is underway but not without problems (22). 

Characterization of Latex Particles with Respect to Carboxyl Distribution. All latex samples were cleaned by the serum replacement technique (10). Diluted latex sample (3% by weight) was placed in the cell confined with a Nuclepore membrane and distilled deionized water was fed into the cell from a reservoir placed at 1.5 meters above the cell. The serum from the cell exit was collected and monitored with conductance measurement. 

The difference in the carboxyl distribution between the two types of latexes is more clearly shown in the time dependence measured by the change in conductance after injection of NaOH according to the method outlined in the experimental section. A typical result of the time effect on the conductance of the latex -NaOH mixture is shown in Figure 4. The conductance at level "A" in Figure 4 is the conductance obtained when the same amount of NaOH solution is added to water only, i.e., in absence of latex particles. The conductance at level "B" represents the conductance of the latex measured immediately after injection of NaOH solution, i.e. at time zero. The conductances at levels "C" and "DM represent the conductances measured at 10 minutes and 24 hours, respectively, after injection of NaOH. 

Prior to the measurements of the different reactor latex samples the computerized HDC was calibrated for particle-size using the standard procedure (3) and also for particle-size distribution quantification. For the particle-size distribution calibration two different particle-size monodisperse carboxylated S/B latexes were polymerized. Various mixtures of these latexes were prepared by blending the large 2100A and the small 700A latexes in different ratios by weight 60/40, 70/30, 80/20 and 90/100 respectively. 

Also it should be noted that this computerized HDC analysis for particle-size measurements oi these latexes was within 2% oi that measured by TEM. Since the particle-size determinations by the two different methods were in close agreement it was accepted that the HDC eluant composition was minimizing the particle-swelling phenomenon of the carboxylated S/B particles. 

From the particle size measurements it was found that, in the case of carboxyl-functionalized samples stabilized with SDS, the particle size is relatively constant (around 100 nm) until 10 wt% of added acrylic acid. At higher amounts of acrylic acid, the diameter sharply increased, reaching an average value of 140 nm. The increase in particle size with increased amount of acrylic acid was explained by the formation of a hairy layer around the particle, which is mainly composed of the hydrophilic poly(acrylic acid) units. In contrast, the size of the amino-functionalized particles is not strongly dependent on the initial amount of functional monomer and was in the range 110-130 nm. This was expected because, in contrast to acrylic acid, the AEMH (p/ftt = 8.5) is completely water-soluble at the experimental pH below 3.5. Moreover, AEMH is very reactive and shows strong chain-transfer behavior [72, 73], and therefore the surface layer mainly consists of short chains. 

X-ray diffraction measurements were used to determine the orientation of talc and lead carboxylate fillers in plasticised PVC extrudates. Correlations between the extrusion conditions (draw ratio and temperature), the development of filler particle orientation and the tensile properties of the plasticised PVC were studied. The presence of fillers enhanced Young s modulus and this was predicted well by the model developed by Halpin and Tsai. The extrudates were stretched above and below the gel-liquid transition temperature of PVC (about 205C). Above this temperature, the PVC could be stretched more and the tensile results indicated that the crystallites which were surrounded by more flexible chains were more oriented. 24 refs. 

In no-matrix resins, triallylamine is used as the self-crosslinking monomer with methacrylic or acrylic acid as the acidic monomer. The crosslinked resin obtained by polymerizing a mixture of triallylamine and an acidic monomer would be expected to have the sites arranged so that maximum interaction occurs between amine and carboxylic acid groups as shown in Fig. 9 Indeed, such particles have no thermally regenerable capacity and electron micrographs of these products show a uniform gel phase with no segragation of sites into domains. Obviously, measures are necessary to prevent such interactions. Several approaches have been made to minimize the internal salt formation in no-matrix resins these are discussed below. 

By combining thermodynamically-based monomer partitioning relationships for saturation [170] and partial swelling [172] with mass balance equations, Noel et al. [174] proposed a model for saturation and a model for partial swelling that could predict the mole fraction of a specific monomer i in the polymer particles. They showed that the batch emulsion copolymerization behavior predicted by the models presented in this article agreed adequately with experimental results for MA-VAc and MA-Inden (Ind) systems. Karlsson et al. [176] studied the monomer swelling kinetics at 80 °C in Interval III of the seeded emulsion polymerization of isoprene with carboxylated PSt latex particles as the seeds. The authors measured the variation of the isoprene sorption rate into the seed polymer particles with the volume fraction of polymer in the latex particles, and discussed the sorption process of isoprene into the seed polymer particles in Interval III in detail from a thermodynamic point of view. 

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