Viscosity of resin solutions

Viscosity of Resin Solutions. The viscosity of coatings must be adjusted to the appHcation method to be used. It is usually between 50 and 1000 mPa-s(=cP), at the shear rate involved in the appHcation method used. The viscosity of the coating is controUed by the viscosity of the resin solution, which is in turn controUed mainly by the free volume (4). The factors controlling free volume are temperature, resin stmcture, solvent stmcture, concentration, and solvent-resin interactions. 

The temperature dependence of viscosity of resin solutions can be expressed by the WLE equation (eq. 3) where the reference temperature T is taken as the lowest temperature for which data ate avaUable (92,93). 

Over the past several decades, knowledge of the properties of solvents and resin solutions has been acquired by laborious experimental work. Especially important properties are the evaporation characteristics and solvent power of neat solvents and the viscosity of resin solutions. 

Surface Tension and Coating Properties Viscosity of Resin Solutions as Related to Solvent Properties... 

Viscosity of Resin Solutions as Related to Solvent Properties. A principal function of solvents in coatings is to reduce the viscosity of the resinous binder so that the coating may be applied to the substrate. The proper application viscosity must be attained... 

Because neat solvent viscosity is so important in regulating viscosity of resin solutions, the calculation of viscosity of blends of solvents is a useful tool in formulating solvent systems for coatings. As part of a computer program to formulate solvent blends. Nelson et al. (41) calculated viscosity of blends by use of the following equation ... 

Equations have been proposed to express the relationships between concentration and viscosity of resin solutions. Equation (2), in which Wr is weight fraction resin and the s are constants, has been shown to fit over a wide range of concentrations (12). Over narrower ranges of concentration, a simpler equation, equation (3), gives reasonable fits with the experimental data. 

Solvents are selected using the general rule that like dissolves like. Three-dimensional solubility parameters are used when a change of solvent combination is required by cost changes, new toxicity information, etc. Solvents have a marked effect on the viscosity of resin solutions (see the section on Flow for discussion). 

Viscosity. Solvent viscosity of resins is influenced by the concentration of resin, the softening point, the molecular weight distribution, the chemical composition of the resin, and the type of solvent. The higher the resin concentration, the higher the viscosity. For a given concentration, solution viscosity depends on the softening point of the resin (Fig. 22). 

We will now turn our attention from the viscosity of dilute solutions and look at the viscosity of melted polymers. The viscosity of melted polymers is important in transferring resins and in polymer processing such as determining the correct conditions to have a specific flow rate for injection processing and in determining the optimum conditions to get the necessary dimensions of extruded shapes. Fillers, plasticizers, temperature, solvents, and molecular weight are just some of the variables that influence the viscosity of polymer melts. Here we will look at the dependence of melt viscosity on polymer molecular weight. Polymer melts have viscosities on the order of 10,000 MPa (1 centipoise =0.001 Pa/sec). 

O, adsorption of Cu(II) on partially quaternized poly(4-vinylpyridine), Cu-tempelate DBQP resin (erosslinking 42%), viscosity of polymer solution... 

In the use of spraying blenders, the following technique can be successfully applied. All the paraformaldehyde powder hardener and 30% of the tannin adhesive spray-dried powder is removed from the liquid glue mix. The paraformaldehyde and wattle adhesive powder are then added to the wood chips just before the adhesive blender where the liquid glue mix is sprayed onto the wood particles. Core material MCs of 10 to 12% and face material MCs of 20 to 22% can then easily be achieved in spite of the high viscosity of tannin solutions. The percentage of paraformaldehyde used should be 14% based on wattle extract solids. The adhesive pH should be, in optimal cases, 6.5 to 6.7 for face material and 6.9 to 7.3 for core material. The percentage of resin solids on dry wood should be 11% for core material and 14 to 18% for face material. 

As used here [rj] c denotes the increment in relative viscosity which results when a resin molecule is added to the solution at concentration c. Consequently, its value for a given resin can strongly depend on the concentration, and on the nature of the diluent. At infinite dilution Equation 1 gives Meff = M, and the intrinsic viscosity has its conventional meaning, i.e., the limiting value of (rj8 — r)o)/voc at infinite dilution. Here rj8 is the viscosity of a solution of concentration c (grams/dl) and 770 is the solvent viscosity. 

The high viscosity of tragacanth solutions makes it useful in pharmaceutical practice as a suspending agent in aqueous mixtures containing resinous tinctures (such as jalap and myrrh) and heavy insoluble powders. Glycerite of tragacanth is a useful excipient to bind pill masses. 

All vinyl resins have a linear carbon chain with lateral substituents and exhibit a range of molecular masses. Increasing molecular mass is accompanied by improved mechanical properties, a decrease in solubility, and an increase in the viscosity of their solutions. Vinyl resins of high molecular mass can therefore only be used in the form of dispersions or powders for paint applications. Solvent-containing paints require vinyl resins of considerably lower molecular mass than plastics, since only then a sufficient binder content can be achieved in the viscosity range required for paint application. 

The viscosity of bark extracts is strongly dependent on concentration. The viscosity increases very rapidly above a concentration of 50%. Compared to synthetic resins, tannin extracts are more viscous at the concentrations normally required in adhesives. The high viscosity of aqueous solutions of condensed tannins is due to the following causes, in order of importance ... 

Another example of this type can be given in the case of nitrocellulose solutions (8g RS /2sec. NC/ 100 ml). The viscosity of these solutions in pure chemical solvents increases as in the case of the epoxy resin solutions with increasing resin concentration. Ketones, with lower neat viscosities than comparable esters result in lower solution viscosities (neat viscosity at 25°C in cS of MEK = 0.46, EtAc = 0.51, MiBK = 0.74, -Bu Ac = 0.84). When ketone is used in combination with a non-solvent (e.g. an SPB) or diluent such as toluene, an increase in viscosity can be observed. This increase is rather sharp when coming close to the point where the resin becomes insoluble (Figure 2.23). When a fixed amount of an SBP/toluene blend is used as the diluent, the viscosity of similar solutions decreases with increasing toluene content of the diluent blend (Figure 2.24). 

While bulk or emulsion polymerization can also be used for the purpose, the commercial manufacture of polystyrene is mostly carried out in a solution process using a free-radical initiator. The solvent, typically ethylbenzene, used at a level of 2-30%, controls the viscosity of the solution. High-impact-grade polymer used in injection-molding and extrusion is modified with butadiene rubber incorporated during polymerization. The solvent and residual monomer in the crude resin is removed by flash evaporation or in a devolatilizing extruder (at about 225°C). Figure 2.9 is a schematic of the polymerization process. 

The course of the reaction can be followed by (1) the drop in acid content, since the -COOH group disappears for every ester link formed, (2) the rise in viscosity and also less reliably by (3) the volume of water produced. The acid content is measured by titration of resin solution with alcoholic alkali solution and the acid value (AV) or acid number (AN) of the resin is the number of milligrams of potassium hydroxide required to neutralize 1 g of solid resin. AV values of commercial alkyds are usually between 5 and 30. Water evolution is never sensitive enough to monitor the reaction properly, and the first two tests are those normally carried out together. 

According to the mass process, polybutadiene rubber is dissolved in the mixed solution of styrene and acrylonitrile monomers, and then the reaction proceeds to prepare the ABS resin. For polybutadiene rubber, the method for grinding and then adding the rubber is utihzed. Contrary to the emulsion process, the particles of polybutadiene rubber are not present before the reaction, and therefore, the shape and distribution of particles appear to be different from those of the emulsion process. The molecular weight of polybutadiene rubber to be used is about 200,000, with the cis-1,4 ratio being about 40%. The amoimt of polybutadiene rubber used should be kept to 20% due to the problem related to a viscosity of polymerization solution. 

In viscosimetry, the (d5mamic) viscosity of a diluted solution of a special solvent and HDPE resin is determined, e.g. by capillary viscosimetry as per EN ISO 1628-3 2003 Plastics - Determination of Viscosity of Polymers in Dilute Solution Using Capillary Viscometers - Part 3 Polyetl l-enes and Polypropylenes. The flow time of the solution t and of the pure solvent to is measured in a capillary immersed in a hot bath at an elevated temperature. The coefficient of viscosity J is determined from this flow times. It is defined as the relative change of the viscosity of the solution p (proportional to t) with the concentration c related to the viscosity of the solvent rjQ (proportional to to) ... 

Viscosity of polyester solutions depends on several variables molecular weight, molecular weight distribution, Tg of the resin, and the number of functional groups per molecule. Intermolecular hydrogen bonding can be minimized by using hydrogen-bond acceptor solvents such as ketones. Synthesis of low... 

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