Resin flow phenomenon

It is obvious that the pump handles only clear liquid which is forced into the top of a pressurized tank to move the settled resin bed as a dense slurry out of a pipe near the base of the tank. Systematic studies done on this phenomenon showed that the slurry moved along the pipe as closely packed as in the settled bed itself. The voidage of the delivered sluny was proved to be constant. This technique can be used for accurate control of resin flow rates since the flow rate of slurry is a constant fraction of the flow rate of displacing liquid. ... 

Because the volume of the resin required has been established (to handle 103 bed volumes/h), the inside diameter (D) and the length (L) of the bed can be determined in order to be comparable to the residence time of the quinaldic breakthrough study. Two approaches can be followed in length and diameter determinations. One involves duplicating the breakthrough or the bench-scale studies. The second approach involves the practical aspects such as L/D and the pressure drop phenomenon. As a general rule, L/D should be more than or equal to 10. Therefore, a 16-in. X 1.0-in. i.d. column was constructed with the following characteristics surface area = 4.9 cm2 residence time = 0.57 min bed volume/h = 103 flow rate = 347 mL/min linear velocity = 70.8 cm/min L/D = 16. 

The validity of Frenkel s model is limited to Newtonian flow and can only be used to predict the early stage of the coalescence process, when the diameter of the two spherical particles remains nearly unchanged. The inadequacy of a Newtonian model in describing the coalescence of polymers was also demonstrated in other studies, as reviewed by Mazur, and has led to the development of models as well as alternative methods for the characterization of the coalescence behavior of polymers for rotational molding applications.Based on theoretical and experimental analyses of the coalescence phenomenon, the material properties of primary interest in the evaluation of resin coalescence behavior in rotational molding have been identifled as the resin viscosity, surface tension, and elasticity. 

Figure 1, shows a rapid increase in apparent viscosity for resin V as the shear rate reaches 17.3 sec1. The sharp increase in apparent viscosity is not any chemical change, such as crosslinking of polymeric chains. The apparent viscosity curve can be retraced by lowering the shear rate. This increase in apparent viscosity can be eliminated by increasing the measurement temperature, as shown in Figure 2. This same phenomenon has been reported for polystyrene by Penwell and Porter (12). The explanation of the apparent viscosity increase in capillary flow of polystyrene was quantitatively explained through the...

Pressure-sensitive adhesives seem to possess a critical balance between adhesion and cohesion. The phenomenon of pressure-sensitive tack has been described as a complex function of flow and diffusion. The role of resins in pressure-sensitive adhesives has been interpreted recently as improving tack by a two-step process (1) reducing the modulus and viscosity of the adhesive to give faster, more complete wetting of the substrate and (2) raising the Tg of the adhesive. Plasticizers and solvents accomplish the first objective but not the second This interpretation is consistent with the... 

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