Borax viscosity

In Figure 9, the gel curves of purified hemicellulose treated with borax and acid to obtain different pH s before drying are illustrated. These curves are almost identical over a wide pH range. The main difference is the temperature where the viscosity of the suspension starts to increase. This temperature increases with a decrease in pH. The temperature of complete gelling, as indicated by the maximum temperature during the heating stage, increases from 72 °C at pH 9 to 78 °C at pH 5. 

The amount of borax added has only a limited influence on the viscosity behavior of the low ash hemicellulose solutions (Figure 10). An increase in the amount of borax seems to increase the gel temperature somewhat. 

If the borax is added to the hemicellulose suspension, the viscosity behavior differs substantially when compared with a hemicellulose suspension with the borax inside the hemicellulose particles. In Figure 11, the viscosity behaviors of two such suspensions are presented. The hemicellulose with the borax added to the suspension of hemicellulose powder clearly gels at a lower temperature. The viscosity upon cooling of this mixture is also much lower when compared with the hemicellulose with borax inside the powder particles. The sodium hydroxide added with the borax to the hemicellulose suspension again may have caused this phenomenon. 

Figure 11. Viscosity of hemicellulose suspensions (12.5% solids) (7) A, suspension of hemicellulose powder obtained from a solution of hemicellulose (14.8% ash) neutralized (pH 7), and mixed with borax (2.0%) before drying and grinding B, suspension of hemicellulose powder (4.8% ash) mixed with borax (2.0%) and sodium hydroxide (2.0%).

Treating starch phosphates with chlorine in methanol increased their viscosity.1606,1607 A viscous, semitransparent paste was obtained using com starch for simultaneous esterification of phosphoric acid and succinic acid in the presence of urea.1608 Polyphosphoric acid was also used, together with calcium carbonate and hydroxide as well as borax.1609... 

Borax containing minerals have been used to lower slag viscosity in wet bottom and cyclone combustors to aid removal. Compounds of borax have also been used to facilitate ash disposal from boiler equipment. 

Highly polymerized polysaccharides with adjacent OH-groups in cis position, or even 1,3-diols, such as in polyvinyl alcohol react with borax (77, 78, 55, 77). The reaction was studied by measuring the increase in viscosity of the respective polymer. For the molecular structure a cross linkage of the borate tetrahedron to the polysaccharides has been suggested (77) (Fig. 12). 

Each borate molecule should form the 1 2 complex. However, the viscosity of the pol5miers decreases at high borax concentrations. The authors attributed this fact to the increasing pH, while ZitUe (77) stated that the decrease must be due to the formation of 1 1-complexes. On the other hand it has to be realized that at high borax concentrations tetraborate anions are present to a large extent which might react in a completely different manner with the polysaccharides. 

In a totally different area of application, casein adhesives for paper sizing, chipboard laminating, and label gluing are more nearly casein solutions [59,60]. They are simple dispersions with ammonia or borax at moderate pH and low viscosity. They are frequently combined with latexes or soluble rosin derivatives for special performance improvements [59]. 

Borax (sodium tetraborate) in the presence of small amounts of sodium hydroxide is the most widely used additive to starch-based adhesives. It is commonly used in dextrin adhesives, where it increases the viscosity and acts as a tackifier and viscosity stabilizer. These effects are particularly important in machine application of adhesive to substrate. When used in adhesives, borax is often added in amounts up to 10% based on dry starch before the starch is cooked. Enough sodium hydroxide is added to convert the borax to sodium metaborate, which is the active boron species in thickening. The metaborate is able to hook two starch molecules together, forming a complex (Fig. 5) [10]. If additional sodium hydroxide is added, the complex will dissociate the viscosity of the suspension will begin to decrease with increasing sodium hydroxide [11]. 

Dextrins have many applications, with adhesives being their primary market (11,96). Dextrins are used as adhesives for case and carton sealing. For this application, borax is often added to the dextrin to add stability and increase viscosity. Dextrins are added to adhesives used in the laminating of products such as paperboard and shipping containers. The paper industry adds dextrins in adhesives for tube winding and bag adhesives. Library pastes, bottle label adhesives, envelop adhesives, gummed tape, and wall covering adhesives all benefit fiom dextrin addition. 

For the physicochemical properties determinations, a PHS-3C precision pH meter supplied by the Shanghai Precision Scientific Instrument Co. Ltd was used to measure the pH of the equilibrium aqueous solutions (uncertainty of + 0.01). The pH meter was calibrated with standard buffer solutions of a mixed phosphate of potassium dihydrogen phosphate and sodium dihydrogen phosphate (pH 6.84) as well as borax (pH 9.18) the densities (p) were measured with a density bottle method with an uncertainty of 0.2 mg.cm-3. The viscosities (tj) were determined using an Ubbelohde capillary viscometer, which was placed in a thermostat at (308.15 + 0.1) K No fewer than five flow times for each equilibrium liquid phase were measured with a stopwatch with an uncertainty of 0.1 s to record the flowing time, and the results calculated were the average. An Abbe refractometer (model WZS-1) was used for measuring the refractive index (no) with an uncertainty of 0.0001. The physicochemical parameters of density, refractive index and pH were also all placed in a thermostat that electronically controlled the set temperature at (308.15 + 0.1) K. 

Similar to borax, boronic acid-containing polymers can also be used to crosslink polyhydroxy polymers, such as PVA. Kitano et al. reported the first example of an interpolymer complex based on boronate-diol interactions. The complex was formed by mixing a PVA solution and an alkali solution of poly(AI-vinyl-pyrrolidone-co-3-acrylamidophenylboronic acid). Complex formation leads to an increase in solution viscosity. Above a critical polymer concentration, the complex solution loses its fluidity to become a transparent gel. The authors later increased the solubility of the polymer under physiological and acidic aqueous conditions by incorporation a third comonomer, Af,Af-dimethylaminopropylacrylamide (DMAPAA). Therefore, an interpolymer complex can form at physiological pH. 

Miller, D.P., dePablo, J.J., and Corti, H.R., Viscosity and glass transition temperature of aqueous mixtures of trehalose with borax and sodium chloride, /. Phys. Chem. B,103,10243-10249,1999. 

Casein has been used as a central binder type in the past, but nowadays is of only marginal importance in cast coatings. For its appHcation it must be present in the dissolved state. It is dissolved by the addition of alkaH (e. g., ammonia, sodium hydroxide, borax, or sodium carbonate) either separately in a cooker (up to 70 °C) or with the pigment in a kneader. The casein concentration is limited to ca. 20% due to its high viscosity. The Hmit of processabiHty is shifted to ca. 33% by the addition of urea or dicyanodiamide, which reduces the viscosity and increases the storage stabihty of casein solutions. The mixing of casein solutions with pigments. 

A second modification to reduce viscosity is to treat the starch with chlorine under alkaline conditions. Lightly chlorinated starches use the water fluidity method of viscosity designation, but more heavily chlorinated products use a borax fluidity procedure. Chlorinated starches are generally called oxidized starches. They are anionic, in that they contain negative charges. This can be verified by staining with cationic dyes. Methylene Blue is a typical cationic dye. 

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