Solution blending Viscosity

HPC is compatible with many natural and synthetic water-soluble polymers and gums (50). Generally, blends of HPC with another nonionic polymer such as HEC yield water solutions having viscosities in agreement with the calculated value. Blends of HPC and anionic CMC, however, produce solution viscosities greater than calculated. This synergistic effect may be reduced in the presence of dissolved salts or if the pH is below 3 or above 10. 

Figure 8 illustrates the relationship between inherent viscosity (IV) and concentration for PBI/PAr/NMP solutions. It is interesting to note that the IV of all solution blends exhibited normal polymer solution characteristics. At a fixed concentration (0.5%), it was noted that the IV of the solution blends exceeded the rule of mixtures (see Fig. 9) suggesting that PBI and PAr exhibit specific interactions in a dilute solution, such that the resulting hydrodynamic sizes of the blends were greater than that of the calculated averages based on each component. 

We attempted to prevent excessive dispersal of rubber particles by blending at a higher temperature which decreases the viscosity of the mix and reduces the shear experienced by the rubber. This technique slightly improved the impact strength, but the product still failed to match the solution blended polymers. 

Zhang and He (2002) have compatibilized LCP polyester (Hoechst Vectra B950) with polysulfone-g-MA, the functionalized polysulfone having been prepared in solution. Blend characterization techniques included XPS, DMA, morphology and melt viscosity. 

Low molecular weight PS was mixed vdth poly(methyl phenyl siloxane), PMPS, to form an immiscible blend with an upper critical solution temperature (UCST) [199]. The viscoelastic properties were studied by dynamic and steady-state shearing the neat polymers showed Newtonian behavior. Within the miscible region the blend viscosity followed the Mertsch and Wolf equation, Eq. (2.35), but with the parameter /fit = calculated from Bondi s tables. The phase separation created a rheolog-ically complex behavior. 

The lower, low-shear-rate viscosities and the absence of a high extensional viscosity in POE/SGPS aqueous solution blends suggest complexation. Such complexation appears to effectively disrupt the three... 

Methods of Blend Preparation. Most polymer pairs are immiscible, and therefore, their blends are not formed spontaneously. Moreover, the phase structure of polymer blends is not equilibrium and depends on the process of their preparation. Five different methods are used for the preparation of polymer blends (60,61) melt mixing, solution blending, latex mixing, partial block or graft copolymerization, and preparation of interpenetrating polymer networks. It should be mentioned that due to high viscosity of polymer melts, one of these methods is required for size reduction of the components (to the order of /ttm), even for miscible blends. 

With respect to the blend composition dependence, the viscosity behavior greatly depended on the polymer concentration no additive property was demonstrated. For the 20wt% solution, the trend of dependence changed at the blend composition of 50/50. For the 20, 25, and 35 wt% solutions, the viscosity for EC was greater than that for HPC on the other hand, the viscosity for the EC was smaller than that for HPC for the 40 wt% solution. 

The dependence of steady-state viscometric behavior on blend composition greatly depended on the solution phase For the isotropic solution, the trends of behavior changed at the composition of 50/50 for the biphasic solution, the viscosity exhibited a maximum around 15/85 for the single-phase anisotropic solution, the behavior of the H PC-rich compositions was different from that of the EC-rich compositions. With respect to the stress growth behavior, there were two retardation times for the isotropic solution, and three or four retardation times for the anisotropic solutions. Those data showed that HPC and EC are immiscible. 

The resins used to study the influence of EP/PP viscosity ratio were provided by SOLVAY. Samples, PPEP3 and PPEP4, are reactor blends produced in gas-phase by a two-stage polymerization process. They differ by the viscosity ratio between the EP and the PP phases which corresponds to the ratio of the solution intrinsic viscosities of the xylene-soluble fraction (mainly EP) and the xylene-insoluble fraction (mainly crystalline PP). Disks of these resins were injection molded and analyzed by TEM and by AFM and FMM. 

The Fox equation relationship (Rg. 7.10) defines or describes the composition dependence of the Tg of ideal co-polymer or ideal polymer blends (or miscible blends of two polymers) in which no strong interactions are involved. The Fox equation typically is expected to lead to a lower value of Tg than would be given by a simple linear Rule of Mixtures (Blend Inherent Viscosity vs. % Component in the Solution Blends) and reflects the effective higher free volume or randomness due to the presence of two components in the mixture ... 

Product Concentrate. An aerosol s product concentrate contains the active ingredient and any solvent or filler necessary. Various propellent and valve systems, which must consider the solvency and viscosity of the concentrate—propellent blend, may be used to deUver the product from the aerosol container. Systems can be formulated as solutions, emulsions, dispersions, or pastes. 

Spray Drying. Spray-dry encapsulation processes (Fig. 7) consist of spraying an intimate mixture of core and shell material into a heated chamber where rapid desolvation occurs to thereby produce microcapsules (24,25). The first step in such processes is to form a concentrated solution of the carrier or shell material in the solvent from which spray drying is to be done. Any water- or solvent-soluble film-forming shell material can, in principle, be used. Water-soluble polymers such as gum arable, modified starch, and hydrolyzed gelatin are used most often. Solutions of these shell materials at 50 wt % soHds have sufficiently low viscosities that they stiU can be atomized without difficulty. It is not unusual to blend gum arable and modified starch with maltodextrins, sucrose, or sorbitol. 

Phthahc resins are usually processed to an acid number of 25—35, yielding a polymer with an average of 1800—2000. The solution viscosity of the polymer is usually followed to ascertain the polymer end point. The resin is cooled to 150°C and hydroquinone stabilizer (150 ppm) is added to prevent premature gelation during the subsequent blending process with styrene at 80°C. The final polymer solution is cooled to 25°C before a final quaUty check and dmmming out for shipment. 

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