Latex-cleaning

III Latex Clean-Up, Typically 20-50g of latex was subjected to a series of centrifugation/redispersion cycles in 900 cnr of 1 1 volume ratio alcohol water mixtures (3 times) followed... 

Connected to the cleaning techniques is the characterization of aqueous-phase oligomers and polymers and surface group analysis. Oligomer analysis is discussed in Section 11.2.5. Here, a brief mention of particle surface characterization techniques will be given because these are generally used in combination with the above-mentioned latex cleaning techniques. 

Several surface characterization techniques are used to monitor the latex cleaning process, among these are conductometric and potentiometric titrations, IR spectroscopy, electrophoresis and titration with a surface-active substance (see ref. 18 and references therein). Both in potentiometric and conductometric titrations even small traces of CO2 can lead to eironeous results [18]. In general the surface charge density is followed as a function of the cleaning process [23]. 

If the composition of each of the three types of polymer pesent at these locations has to be known, latex isolation and cleaning is of crucial importance. El-Aasser [18] has summarized the methods of latex cleaning. 

Then, 300-500 ml latex was agitated slowly with an estimated 5-fold excess of resin (based on electrolyte and emulsifier concentrations), filtered, and titrated. This procedure was repeated until a constant charge was obtained. Ion exchange in batch was more efficient than ion exchange in columns. The effectiveness of the ion-exchange latex clean-up has been described in detail elsewhere (7-9). 

Asymmetrical flow field-flow fractionation (flow FFF) and specifically hoUow-fibre flow FFF (HFs) have the potential of combining latex clean-up and characterization. Capillary electrophoresis has seen significant advances in the last decade. It may potentiaUy be used to separate and characterize charged latex beads and low-Mr charged components (stabilizers, surfactants and charged oligomers) without prior sample clean-up. 

El-Aasser, M.S. (1983) Methods of latex cleaning. In G.W. Poehlein, R.H. Ottewill and J.W. Goodwin (eds). Science Technology of Polymer Colloids. Surface Characterization of Latexes. Characterization, Stabilization and Application Properties, Vol. 11, No. 68. Martinus Nijhoff Publishers, The Hauge, p. 422. 

Latex (cleaning) Often used synonymously with rubber. Example Latex (rubber) gloves. 

Vanderhoff J W, van den Flul FI J, Tausk R J and Overbeek J Th G 1970 The preparation of mododisperse latexes with well-oharaoterized surfaoes Clean Surfaces ed G Goldfinger (New York Dekker) pp 15-44... 

In dipping generally, but particularly with the anode process, it is desirable to use tanks that circulate the coagulant and latex compound, particularly the latter. Use of circulation keeps the Hquid surface clean and free from lumps, scum, or bubbles. Mechanical circulation can cause mbber particle instabihty, however, and eventually coagulate the compound. Therefore, tanks should be designed to minimize friction or shear action, and the compound stabilized to maintain mechanical stabiUty. 

The AeroSizer, manufactured by Amherst Process Instmments Inc. (Hadley, Massachusetts), is equipped with a special device called the AeroDisperser for ensuring efficient dispersal of the powders to be inspected. The disperser and the measurement instmment are shown schematically in Figure 13. The aerosol particles to be characterized are sucked into the inspection zone which operates at a partial vacuum. As the air leaves the nozzle at near sonic velocities, the particles in the stream are accelerated across an inspection zone where they cross two laser beams. The time of flight between the two laser beams is used to deduce the size of the particles. The instmment is caUbrated with latex particles of known size. A stream of clean air confines the aerosol stream to the measurement zone. This technique is known as hydrodynamic focusing. A computer correlation estabUshes which peak in the second laser inspection matches the initiation of action from the first laser beam. The equipment can measure particles at a rate of 10,000/s. The output from the AeroSizer can either be displayed as a number count or a volume percentage count. 

Poly(vinyl acetate) latex paints are the first choice for interior use (149). Their abihty to protect and decorate is reinforced by several advantages belonging exclusively to latex paints they do not contain solvents so that physiological harm and fire ha2ards are eliminated they are odorless they are easy to apply with spray gun, roUer-coater, or bmsh and they dry rapidly. The paint can be thinned with water, and bmshes or coaters can be cleaned with soap and tepid water. The paint is usually dry in 20 minutes to two hours, and two coats may be applied the same day. 

Irritant contact dermatitis results from first-time exposures to irritating substances such as soaps, plants, cleaning solutions, or solvents. Allergic contact dermatitis occurs after an initial sensitivity and further exposure to allergenic substances, including poison ivy, latex, and certain types of metals. 

Polystyrene Latexes. The polystyrene latexes used were the mono-disperse LS-1102-A, LS-1103-A, and LS-1166-B (Dow Chemical Co.) with average particle diameters of 190, 400, and llOOnm, respectively. The latexes were cleaned by ion exchange with mixed Dcwex 50W-Dowex 1 resin (9). The double-distilled and deionized (DDI) water used had a conductivity of 4x10 ohm- cm-. The surface groups of the ion-exchanged latexes determined by conductometric titration (10) were strong-acid sulfates the surface charge densities were 1.35, 3.00 and 5.95 jiC/cm, respectively. 

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