Brabender units

DSC revealed that the XG and starch did not interact synergistically and hence did not promote the formation of three-dimensional network structures. However, the hydrocolloid significantly decreased the retrogradation and syneresis of the starch paste, particularly in blends with a starch/XG ratio of 8.5/1.5. Mixing 1% or 2% tamarind XG with 9% cornstarch resulted in an increase in the paste viscosity from 385 to 460 and 560 BU (Brabender units), respectively [298]. The XG is associated with starch, as was evident from the lowering of the pasting temperature and the synergistic increase in pseudoplasticity and yield value of the blend pastes. However, carboxymethylated and hydroxypropylated XGs showed a diminished interaction. 

Viscometer test. Typical crosslinked starches are obtained when the initial rise of the viscosity of the product is between 104° and 144° C, and the viscosity of the product does not rise above 200 Brabender units at temperatures less dian 130° C. The crosslinked starch slurry is then drum-dried and milled to obtain a dry product. The effectiveness of the product is checked by the API Fluid Loss Test after static aging of sample drilling fluids containing the starch at elevated temperatures. The milled dry product can then be incorporated into the oil well drilling fluid of the drill site. 

A, Time at the first increase of the viscosity B, viscosity (in Brabender units) at 96°C C, time at the beginning of cooling D, time at which the increase of viscosity is observed E, viscosity after cooling to 50°C. h The characteristics of gelation of the native starch. 

Several types of viscometer are available that follow viscosity during paste preparation. Industry has widely adopted the Brabender viscometer. This has a rotational bowl and the sample exerts a force on fixed sensing elements that are dynamically balanced by a calibrated torsion spring, this causes an angular deflection of the sensing element shaft, which is continuously recorded. After the cooking, the temperature can be held at 95°C, cooled at a predetermined rate, then held at, say, 50°C to evaluate stability of the paste. The instrument is calibrated in arbitrary Brabender Units of viscosity. Typical viscosity curves of some native starches are shown in Figure 4. 

Potato starch shows a very high maximum ( 4000 Brabender units), followed by a steep drop. Waxy com starch exhibits similar behavior, except that the maximum is not as high. In normal com starch, the maximum is still lower, but the following drop is slight, i. e., the granules are more stable. Under these conditions, amylomaize starch does not swell, even though ca. 35% of... 

The other component in this model is useful for determining the variation between two different test methods. If you have a Brabender and a two-roll mill or two different injection molders, then method A can be one unit and method B the other. 

The plastograph of the Brabender Co. enables similar experiments to be carried out at higher speeds the r.p.m. of the working units varies from 20 to 200 min The working assembly of the instrument is a heated chamber with two shaped rotor-rollers. A theoretical analysis of the flow is in this case rather difficult... 

In the present study we utilized Plasticorder torque values (polymer viscosity) on a relative basis, principally to follow the course of thermoplastic polyurethane elastomer polymerization, and the effect of several relevant variables on this polymerization. These torque data, expressed in meter-grams, served our purposes well, and we have not attempted to translate them to absolute rheological units. Such translation, which is a rather complex problem, has been addressed by others using a different rotor type and other polymers in the Plasticorder.14 That study concluded that the shear rate, y, of the Brabender Plasticorder with a somewhat different rotor configuration (roller blade) is in the range of 23 - 228 sec 1 over the rotor speed range of 30 - 200 rpm. 

Brabender-type units are preferred for product and process development work because they are easy to use, require only a small quantity of compounds, and provide very valuable information, which includes fusion rate and blend stability at mix temperature as well as reaction kinetics as a function of mixing speed, temperature, and rotor type. This information is very important in the production scale-up of... 

It is apparent that a jxrssible preparation of the block copolymers of lactams and a lactone (i.e. CL, LL and CLO) must be kineticaUy controlled in order to suppress the transamidation and transacylation reactions a short polymerization time and an intensive stirring must be guaranteed. When a,(D-dihydroxy poly (e-caprolactone), functionaUzed ex situ by diisocyanates (MDI), was used as a starting substance, the gradual charging of this material into the Brabender internal mixer, together with a partially polymerized feed (LL, NaH, AcCL 13) yielded a copolymer in which longer sequences of e-caprolactone units were present [74]. 

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