Detection synthetic latex various indicators

(1) General electrolyte emulsion stability will always be sensitive to the electrolyte, but the sensitivity is bound to be a difference. Processing low sensitivity emulsion is always beneficial, for example, will encounter salt processing. Therefore, this test its necessity. But we never had the standard approach. Slight agitation under a certain amount of thin trickle NaCI or CaCL2 (l to 5%) was added to the test emulsion breaking observe whether the case. In more tolerance without breaking as well. Test Method for calcium stability a.100g distilled water was added 0.5g calcium chloride solution dubbed, then add 25g styrene-acrylic emulsion tested, stir still 24h, if not breaking, non-hierarchical, non-gel, benzene acrylic emulsion stability by calcium ions. b. In the 10ml scale test tube, add 5ml lotion use dropper benzenepropanoic then added lml5% CaCL2. solution, after shaking placed in a test tube rack. 48h after birth, if not hierarchical, precipitation, flocculation and other phenomena, the styrene-acrylic emulsion stability by calcium ions. (2) Determination of the minimum film forming temperature: a stainless steel strip, one end of the cold, one end of the heating, the whole showed a uniform temperature gradient from one end to the other end of a few degrees below zero than 100 ℃. Stainless steel bar along with a temperature display steplessly. The emulsion was coated on the strip. Over time, the article emulsion, to form a transparent uniform film on one side, the side of the broken-like polymer becomes cloudy, intermediate demarcated. This line is referred to a temperature of minimum film forming temperature. Accordance with the instructions and requirements of the temperature range, the instrument to the desired value. Particular attention in the boot, first open cooling water to prevent burn refrigeration components. To be determined after measuring the board temperature has reached equilibrium, which began swabs. A stainless steel strip, one end of the cold, one end of the heating, the whole showed a uniform temperature gradient, from a minus several degrees to the other side than 100 ℃. Stainless steel bar along with a temperature display steplessly. The emulsion was coated on the strip. Over time, the article emulsion, to form a transparent uniform film on one side, the side of the broken-like polymer becomes cloudy, intermediate demarcated. This line is referred to a temperature of minimum film forming temperature. Coated sample, particularly a sample uniformity affect the test results, it should be noted operation. In order to ensure a uniform coating thickness, good attachment to the test plate of 0.1 mm thick masking tape, then the emulsion with a rubber blade grooves uniformly coated on the masking tape, cover the upper part of the closure, open air pump, so that the dried air through the upper part of the emulsion, and to observe the filming conditions pity. As mentioned earlier, you can see the status of film emulsion to be significantly different from the film-forming section is continuous, transparent film-like, while the other part is intermittent, even startling shaped white sheet (powder) was measured at a temperature boundary of the two parts is the minimum film forming temperature (MFT). (3) Measurement of particle size distribution: latex particle size and particle size distribution is a very important indicator. Because many properties directly related, for example, the film gloss. To a certain extent, the finer the particles, the better the luster. Product polymer emulsion particles are made of different size configuration, so called the polydispersity of the emulsion. The liquid is generally composed of large particles, called monodisperse emulsion. This only laboratory values. Polydispersity of favorable density film. As a coating, film density is naturally extremely important properties. Of course, more is to have a degree of dispersion. Not the more decentralized as possible. There are many ways to detect emulsion particle size:. A SEM; electron microscopy to see, or camera watching films, it is intuitive, there are definite way, but the sample prepared technically demanding, expensive equipment, emulsion particles interfere. . b ultracentrifugation method: diluted to accurate and precise concentrations of emulsion placed in a centrifuge tube, to gradually increase the speed of the rejection, at various speeds at a predetermined position (a known particle size) to take certain fractions, and then measuring the concentration , that each wt% polar points. This not only measure the particle size distribution is also clarified. . c soap titration method: A method of preparing an emulsion with the same (not necessarily, but so can simplify the calculation) surfactant solution titration thin emulsion, the measured surface tension; usually recorded when the surface tension tends surfactant concentration; painted concentration tension curve; slope of the active agent of the moles of polymer adsorption surface per gram; thus calculate the surface area per gram of polymer particle size can be obtained therefrom. This method is simple rapid cheaper, is also accurate. . d light scattering method: different particle size, scattering light different perspectives, different intensity, whereby the viscosity and viscosity profile can be calculated. Many fine particle size and particle size distribution analyzer is based on this law. Plus data processing, can list, draw graphs, histograms output test results. This is a worthy method of detecting coating polymer emulsion. e cream skimming points system: able to save a given concentration of the sodium alginate solution, only those particles above a corresponding critical size was only skimming. Changing the concentration of sodium alginate, it will be able to write out the different size particles. Test weight can be obtained weight ratio levels. Referring electron microscopy measured particle size distribution can be obtained. f..Joyce a disc from your favorite LOebl That measure the particle size using a centrifugal sedimentation method. The principle is that when any particle agglomeration system is dispersed in a liquid medium, the particles can settle by force of gravity occurs when irregularly shaped particles of different sizes settlement in a liquid dispersion medium, each having a certain degree of sedimentation rate . Spheroids of different diameters assumed sedimentation settling these irregularly shaped particles is equivalent to having the same density, i.e., measured under the same conditions of the spherical body having an irregular particle settling velocity the same settling velocity, the irregular particle diameter can be used to indicate the diameter of the sphere, called a free fall particle size (Free-fallingDiameter). Exhausted floating in the liquid dispersion medium with different size particles when they are settling, sedimentation rate and particle size, particle density and liquid density and viscosity of the dispersion medium is related to the process can be used Stoke's equation: Wo = (D2 ( a Ps Po) g / 18η) × (w2 / gR) where: w0 a centrifugal sedimentation velocity (m / s), the density of a solid particle diameter D (m) P0 of a liquid dispersion medium (kg / m3) Ps one the density of solids (kg / m3) g a gravitational acceleration (m / s) w all linear velocity (m / s) R a radius of gyration (m) η- viscosity of the liquid medium (Pa? s) is derived by the conversion formula The formula to give a solid particle size: T = [(6.229 × 109η) / (D2 × N2 △ ρ?)] logR2 / R1 where:? T a settling time (min) D Four-stars pull a particle size ( μ) N a centrifuge speed (r / min) △ ρ- density difference between the particles and the dispersion medium (g / cm3) R1 radius settlement beginning when (cm. location solids, depending on the used rotating pan the volume of the liquid dispersion medium) R2- beam to disc center distance (cm, depending on the instrument itself) wherein ,, R ,, where, N, P are known values, T is variable. T can be calculated from the paper speed and time of the test specimen during testing. Therefore, the known values ??at different times and each T can be calculated into the equation in the particle size of the test sample. At the same time, the percentage of various particle sizes along grain (granules of the number) and absorbance related, so with absorbance method to calculate the cumulative percentage of various particle size and particle size distribution. By centrifugal sedimentation design principles JOyc co Loebl from favorite disc, is determined by Stoke, the formula is equivalent to the spherical granules of particle size and emulsion ,, regardless of micellar nucleation process or homogeneous nucleation process, which ultimately form latex particles are considered to approximate a spherical shape. Therefore, the determination by the centrifugal sedimentation particle size emulsion, and calculate the results with Stoke, equation, emulsion particle size and distribution of the data obtained, it should be more accurate. (4) emulsion Appearance test: The emulsion was placed in a glass tube, colorimetric tubes, visual emulsion color (color contamination consisting of: iron ions; particle size of the resulting colors: blue, red, yellow, gray, silly white, etc.), homogeneous situation (with or without flocculation, delamination, etc.), transparency (opaque, translucent, etc.). (5) determination of solids: Take diameter of about 100mm clean glass or tin small dish placed with forced air oven at 15. ℃ drying to constant weight. After removing the oven should be cooled in the dryer. Fine, said about 5 g sample (sample in an amount sufficient to cover the entire disk diffusion and liquid layer has a thickness, but in degrees) in the dish. The small dish containing the sample is placed around 250W infrared lamp drying. Then, the small dish cool for 30 minutes the dryer. And then weighed. After drying the sample weight / sample weight before drying × 100% = solid% (6) Measurement of PH value: general measurement precision test strips can be. Precision measurement, calibration can be used to buffer the glass calomel electrode pH meter. Emulsion of surfactant may be interference measurement results. Determination (7) emulsion viscosity: Non-Newtonian polymer emulsion, with the polymer solution, such as alkyd resins and other Newtonian fluid is different, the relationship is not linear stress-strain relationship is not proportional. Therefore, the method is suitable for the determination of the viscosity of the polymer solution, such as viscosity Cup, the bubble viscometer and other coatings industry conventional method is not suitable for the determination of the viscosity of the polymer emulsion. Barely brought test, is not allowed, is simply undetectable. Suitable polymer emulsion viscosity measurement method does not rely on gravity flow strain, but directly measure the fluid to shear stress (rotation of the rotor by means of a specific type) of strain. Therefore, such viscometer is called rotational viscometer. Currently, the rotational viscometer internationally uniform standards, that is 1502555 and 3219. The former involved are Brookfield viscometer. But now, countries or even the companies have their own models. Currently, we use the so-called B-type viscometer. In contrast, there are more general standard is based Brook-field viscometer. Today, frequent international exchanges, for comparability, the emulsion product knowledge in order to have a common benchmark, to discuss a common language, and gradually promote such viscometers seems necessary. Brookfield viscometer detection principle is simple: a particular type of rotor in the measured fluid to set the speed of rotation, rotation of the rotor so that the degree of stress coupled torsion spring, is the viscosity of the fluid. Viscosity cps. ps (mPa? S) represented. The larger the rotor, the faster the speed, the viscosity is smaller; the smaller rotor speed, the slower the greater the viscosity. From CHART accompanying viscometer can find cps values. Brookfield viscometer Many models: LVF, LVT, RVF, RVT and so on. Each with a different number of rotors, each with a series of speed, can be measured for each certain viscosity range. Polymer emulsions in general, the highest 10000cPs to meet the requirements. Daily temperature data to indicate the number of the rotor, the speed and the time of measurement. (8) Determination of residual monomer in the emulsion an emulsion in an excess of residual monomer emulsion will bring stability and odor problems. Determination of the residual monomer content saponification titration can be by chromatography. Fried who only gives the total residual amount, the latter is known residual monomer species specific. . a saponification process: steaming water to dilute samples leavened; collect a certain amount of distillate; adding KOH alcohol solution in distillate making under (too alkaline vinegar) state saponification at room temperature or reflux; titration excess base. b Chromatography: Use proper type of gas-liquid chromatography; chromatography equipment thermal conductivity or flame ionization detector; monomer emulsion calibration standard; when, by using a flame ionization detector, the interference of water to methyl ethyl ketone or benzene or acetate, isopropyl Ding vinegar as an internal standard to overcome. (9) the mechanical stability of the emulsion in the mixing, pumping, grinding, painting, shipment problems will occur by the shear stress. Detection may be provided mainly by a strong shear homomixer. First filtering the sample first; then in a mixer with 1500-3000 rpm, 5 a stirred vigorously for 10 minutes and then filtered, the residue was dried filter weighing. No residue is naturally best. (10) the storage stability and thermal stability of the emulsion stability as well, in the store will be layered, will precipitate, transport will play too much foam. Room temperature storage stability assessment: overfilled (for skinning test NOTE 2/3 or half) dark bottle; close stamped; viscosity measured periodically; little change in viscosity (or slightly increase) as well. The same way the thermal stability assessment. The bottle was placed in a constant temperature just (50 ℃ or specific) oven. (11) freeze-thaw stability of the emulsion in transit inevitably cold (cold specifications are not allowed). Occasional cold emulsion does not result in scrap, natural is better. Samples placed 16 hours at low temperature (a 20 ℃ or a 40 ℃) box, place eight hours at room temperature. To not breaking, but the degree to thicken as well, the ideal situation through five cycles. (12) the compatibility of the various additives in latex paint formulations pigment / filler, a variety of additives exist, whether they are compatible with the emulsion, it is very important. Testing focused on some of the solvent, a surface active agent. Test methods and test the same way as the electrolyte. Observation methods include observation of both emulsion stability, but also made a film with and without emulsion side comparison of the test object was observed (whether to maintain transparency, whether loss of light, would not affect the film formation, would not affect the formation of the film, and so on). Emulsion