Study on Properties of Polyanionic Cellulose and Hydroxypropyl Methyl Cellulose Composite Aqueous Solution

Abstract: The properties of aqueous solutions of two types of polyanionic cellulose (PAC) and two types of hydroxypropyl methylcellulose (HPMC) in different proportions were studied. The results showed that the solution viscosity showed a synergistic effect after compounding. After infrared and ultraviolet analysis, as well as the comparative analysis of the opposite phenomenon produced by the compounding of PAC and xanthan gum, it is proved that this synergistic effect is due to the hydrogen bond association between PAC and HPMC molecules in the solution.

Key words:polyanionic cellulose; hydroxypropyl methylcellulose; viscosity; synergy

Cellulose ether is an important cellulose derivative. It is a general term for a class of derivatives obtained from natural cellulose through alkalization, etherification, purification and drying. It is widely used in industries such as medicine, building materials and synthetic resin, and occupies an increasingly important position in the national economy. Cellulose ether solution has a good thickening effect. In practice, a mixture of one or more ionic and non-ionic cellulose ethers is often used as a thickener. The difference in performance of different varieties of cellulose ethers and their good miscibility provide a huge design space for their compounding. Compounding different varieties of cellulose ethers in different proportions is expected to achieve superior comprehensive performance and designability. strong combination. Therefore, in recent years, the compounding of cellulose ethers, especially the research on the rheological properties of the aqueous solution after compounding has become a hot spot in this field.

1. Experimental part

1.1 Reagents and instruments

Polyanionic cellulose (PAC I, PAC II) and hydroxypropyl methylcellulose (HPMC I, HPMC II) were provided by KIMA CHEMICAL CO., LTD.

DV-I+Lv Brookfield rotational viscometer; German Bruker EQUINOX55 infrared spectrometer (measurement range 4 000—350 cm-1, KBr tablet method); Prism UV757CRT ultraviolet-visible spectrophotometer.

1.2 Anionic cellulose pretreatment

Before use, it was washed and purified three times with 70%-75% ethanol aqueous solution, and dried at 105°C to constant weight.

1.3 Testing

1.3.1 Viscosity test

Before the test, the prepared solution must be allowed to stand for more than 20 minutes and kept at a constant temperature of 25°C.

1.3.2 Infrared analysis

Measured with a UV-Vis spectrophotometer.

2. Results and Discussion

2.1 Relationship between viscosity and composition

Accurately weigh the PAC and HPMC samples (accurate to 0.000 1 g) respectively according to the design requirements, pour the two samples into a beaker, stir slightly, and add water to make a solution with a mass fraction of 1%.

For a homogeneous polymer mixed system, its viscosity can be calculated by the principle of logarithmic summation. It is generally believed that if the experimental viscosity value of the two-component solution is consistent with the calculated value obtained according to the above formula, that is, the ratio of the two components to the viscosity of the mixed solution If the contribution is additive, it means that there is no strong interaction between the two macromolecules; otherwise, it is. According to this analysis, in the mixed solution of PAC and HPMC, there exists some kind of interaction stronger than van der Waals force between the two polymer molecules.

Within the range of the compounding ratio studied, the four different combinations of PAC/HPMC mixed solutions showed similar laws: ①The viscosity of the compounded solutions was higher than the viscosity calculated by formula (1) H1, that is, Viscosity synergy; ②With the increase of the mass fraction of PAC, the viscosity of the mixed solution increases gradually at first, and then decreases gradually after reaching a maximum value at a certain position.

PAC is a polyelectrolyte, in the solution, the counter ion Na+ is distributed around the macromolecular chain with a COOH anion. When the proportion of PAC in the system increases, the distance between the macromolecules is far away, and the molecular chain is stretched due to the electrostatic repulsion of anion charges, and is evenly dispersed in the system, making the viscosity increase. With the increase of the proportion of PAC in the system To a certain extent, the number of counter ions bonded by polyions in the system also increases, that is, the effective charge density in the molecular chain decreases, and the electrostatic repulsion is relatively weakened, so the positive deviation gradually decreases. HPMC is a non-ionic polymer, there is no ionic charge in solution, and there is no interaction between ions with PAC in solution. Therefore, the synergistic effect of viscosity may be due to the formation of hydrogen bonds between the two macromolecules.

From the UV spectrum of the single-component solution and the compound solution of PAC and HPMC with a mass fraction of 1%, it can be seen that compared with the single-component solution, the maximum absorption wavelength of the compound solution has a significant red shift, indicating that there is indeed Hydrogen bonds were formed between PAC and HPMC molecules.

2.2 Infrared Spectrum

3. Conclusion

When PAC and HPMC are compounded, due to the formation of hydrogen bonds between the molecules, the measured viscosity of the solution is greater than the viscosity calculated according to the mixing rules, that is, the compound solution of the two shows a synergistic effect of viscosity. In this way, when cellulose ether is used as a thickener, the compound product of the two not only has performance advantages, but also has a price advantage. This is also one of the starting points for people to study the compounding of cellulose ethers.