HPMC solution

Another unique physicochemical property of PVP solutions is their high-surface tension, which is close to purified water. Ritala et al. (86) reported that the use of PVP solutions to granulate dicalcium phosphate in a high shear mixer resulted in more dense granules with larger average panicle sizes than compared with the use of HPMC solutions. Furthermore, low levels of PVP CI5 ranging from 0.2% to 0.8% w/w were found... 

Figure 41. Shear moduli dependence on frequency for silica suspensions in 2.0% aqueous HPMC solutions (218).

A higher separation of DNA fragments from 10 bp to 2 kbp was achieved using the fixed concentrations of 2.25 wt% of 80-nm-PEGylated-latex and 0.49 wt% of hydroxypropyl methycellulose (HPMC) solution under low viscosity of (<5.5 cp). 

HPMC chains adsorb onto the silica surface (9) and their adsorbed amounts are determined to be ca. 0.12g/g, irrespective of the silica concentration and HPMC. Figure 1 displays steady-state shear viscosities of the 5.0, 7.5, and 10.0 wt % silica suspensions dispersed in a 1.5g/100 mL HPMC solution, where the HPMC concentrations in the supernatants are 0.90, 0.60, and 0.30 g/100 mL in... 

Moreover, the HPMC-silica suspensions show solid-like viscoelastic responses their dynamic storage moduli G are larger than the dynamic loss moduli G at small and linear strain ranges. On the other hand, the HPMC solution has much larger values of G than G in the frequency ranges from 0.1 to 100 rad/s due to liquid-like viscoelastic matter. 

Figure 1. Double-logarithmic plots of steady-state shear viscosities as a function of shear rate for 1,5 g/100 mL HPMC solution (open circle), 5.0 (filled triangle), 7.5 (filled circle), and 10.0 wt% (filled square) silica suspensions dispersed in a 1.5 g/100 mL HPMC solution.

Of all viscoelastic substances, sodium hyaluronate solution possesses the highest degree of pseudoplasticity. Pure chondroitin sulfate and HPMC solutions are regarded more as Newtonian fluids. 

As was seen in in-vitro and animal studies, 1% sodium hyaluronic acid, 10 8c 20% chondroitin sulfate and 1% HPMC solutions protected the corneal endothelial cells from potential injury from direct contact of the lOL or instruments with corneal endothelium (Hammer 8c Burch, 1984 Miyauchi 8c Iwata, 1984). There is, however, no viscoelastic capable of shielding the corneal endothelium from sharp instruments, accentuating the importance of creating and maintaining a deep an-... 

Effect of a 5% addition of various salts on the gelation temperature (°C) of a 2% MC or HPMC solution (adapted from [3]). Numbers in parenthesis Indicate the viscosity grades of the derivatives. 

Viscosity measurements of diluted HPMC solutions were performed by Ubbelhode capillary viscometer (flow time for bidistilled water was 195.6 s at 30 °C), immersed in a water thermostat at 30 °C. Proper volumes of 3.0 g/lOOcm SDS solution were added to 15 cm of HPMC solution in order to obtain desired SDS concentration. For each solution, 3-5 viscosity measurements were taken and average values were calculated. The results were expressed as specific, reduced and intrinsic viscosity. 

Figure 1. Influence of SDS concentration on conductivity of SDS solution and various HPMC solutions.

Rheological investigation on HPMC/SDS binary mixtures was performed in order to test influence of SDS concentration on viscoelastic properties of HPMC solution, as well as to test influence of shear rate on HPMC-SDS complex properties. Concentration of HPMC in the binary mixtures was 0.7% (>c ), while concentration of SDS was varied (0.00-2.C... 

Figure 5. Elastic modulus (G ) of 0.7% HPMC solution as a function of SDS concentration.

Figure 6. Dependence of the apparent viscosity (r a) of 0,7% HPMC solution on SDS concentration at different shear rates. CAC, CM, and PSP are denoted as suitably colored stars and filled circles and rectangles, respectively.

Surface tension of 0.7% HPMC solution decreases on addition of SDS until CAC is reached [Taylor, Thomas, Penfold 2007]. Below CAC there is no interaction between HPMC and SDS, and both HPMC and SDS molecules adsorbs separately at the surface which makes surface tension of HPMC/SDS solution lower than surface tension of corresponding SDS solution. Above CAC, SDS binds to adsorbed HPMC molecules via hydrophobic interaction rather than to adsorb to the surface. Consequently, there is no more decrease in surface tension of HPMC/SDS solution on increasing SDS concentration, and surface tension of HPMC/SDS solution becomes higher than surface tension of corresponding SDS solution. Binding of SDS to HPMC molecules continues until PSP is reached. Above PSP surface tensions of corresponding HPMC/SDS and SDS solutions are equal, since all HPMC molecules are solubilized with SDS, and only SDS molecules are adsorbed at the surface. 

The cellulose capsules can be manufactured by the dipping and forming method, employed for the manufacture of hard gelatin capsules. Shaped pins are dipped into HPMC solution of which temperature is maintained over room temperature. The pins are picked up from HPMC solution, cooled at room temperature, and dried by a warm air blow. HPMC base adhered to the pins gelled immediately to form the shape of capsule because carrageenan, a gelling agent, was added. 

The typical pattern of the viscosity of HPMC solution against temperature is shown in Figure 2. HPMC is soluble in water below about 30°C but is not dissolved at higher temperature. The viscosity of HPMC has the shape of convexity when temperature falls from about 60°C. When the temperature of HPMC solution increased from about 30 to 40°C, the viscosity scarcely changed. Since the desirable viscosity of the base to manufacture capsules by the dipping method is about 4000 to 8000 mPas, cellulose capsules are manufactured using HPMC solution at 40 to 50°C. 

Figure 2. Viscosity of HPMC solution. 20% of HPMC solution was slowly refrigerated from 60°C to 27°C and slowly heated to 41 C. The viscosity was measured by Brookfield type viscometer.

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