Rheological Properties of Compositions Based on Modified Polyvinyl Alcohol

developed of a method for producing structured waterproof films based on polyvinyl alcohol (PVA) and montmorillonite-polyvinylpyrrolidone mixture (MPM) to research the impact of borax, pH-environment and MPM content on the rheological properties PVA solutions and water absorption capacity of films based on them. The MPM mixture significantly affects on viscosity the characteristics of the solution polyvinyl alcohol provided their mixing in the ultrasonic field have been established. Composition of traces of sodium tetraborate in the aqueous solution eminent by the highest rates of viscosity. Also, designed compositions considerable influence pH at the viscosity, particularly compositions obtained in weakly alkaline environment with higher values of relative viscosity than compositions obtained in neutral and acidic environments. Кеуwords – polyvinyl alcohol, montmorillonitepolyvinylpyrrolidone mixture, modifier, viscosity, exploitation characteristics, borax, heat treatment, film.


I. Introduction
Polyvinyl alcohol (PVA) used in industrial, commercial, healthcare and food sectors and used for the production of many end products such as varnishes, resins, surgical thread and food packaging materials, which are often in contact with food.This polymer is widely used for blending with other polymers to improve the mechanical properties of films obtained through joint structure and hydrophilic properties [1].PVA is also widely used to produce nanocomposite materials, in particular based on aluminosilicate.
Currently, the focus in the field of layered-silicate nanocomposites of polymer are paying a high level of exfoliation nanoscale particles in a polymer matrix that determines achieve high performance properties.Therefore, the actual problem is the selection of effective organic modifiers layered silicate that provide high adhesion filler with a polymer matrix.In this aspect, considerable interest is the study of the effect of various organic clay of the structure and properties of nanocomposites obtained, the nature of which is not yet fully understood [2].Identifying these patterns allow to expend control over the structure and predict the properties of composite materials based organic clay.

II. Analysis of recent research
One of the promising directions of polymer science and materials science in recent years is getting organic-inorganic polymer nanocomposites that have a predetermined set of properties [3].Nanocomposites combine such chemical, physical and mechanical properties that can not be achieved with the introduction of inorganic fillers of macro or microscopic structure.
Intercalation inorganic polymers in laminated materials such as clay minerals -a promising new method of obtaining organic-inorganic nanostructures -supramolecular structures with specific molecular structure [4,5].Such an approach causing multifaceted interest.Firstly, there is the practical ability to create layered nanocomposites.Secondly, it is important specificity intercalation and its manifestation in acquiring systems improved physical and chemical properties.Furthermore, the study of these products can provide important information about the nature of chemical interactions in them, specific adsorption of polymers on nanoscale particles and so on.Unfilled polyvinyl alcohol has a glass transition temperature of 70 °C and a melting point of 225 °C.To fully intercalated materials (in which all polymer intercalated in the interlayer space of montmorillonite) based on PVA DSC results do not show any signs of Interphase temperature transitions between 35 °C and 259 °C.
Nanocomposites PVA/MMT has a high light transmission even in the filler content, sufficient for the formation of layered nanocomposites.This is due to the dispersion of particles in a matrix layered silicate cover the nanoscale.Good light transmission allows using nanocomposite materials PVA/MMT for manufacturing paper coating simultaneously with unfilled PVA (which is used now).The presence of MMT particles does not affect the permeability of the composite for the visible spectrum (wavelength 400-700 nm), so there is a high light transmission characteristic of unfilled PVA [6], but significantly increases atmospheric stability.
Previous research has developed a method to obtain watersoluble films based on PVA and and montmorillonitepolyvinylpyrrolidone mixture (MPM), studied their performance properties [6][7].The aim of this study was to develop a method of producing structured water resistant films based on polyvinyl alcohol (PVA) and montmorillonite-polyvinylpyrrolidone mixture, investigate the impact of borax, MPM content and pH on the rheological properties of PVA solutions.

III. Research Methods
PVA SUNDY 088-20 by Chinese company "Sinopec Sichuan Vinylon Works" (PVA 088-20 -23 mPa•s) used for obtaining films.Prepared 8% solution of PVA in water and buffer solution with pH 4.4 and 7.9.Dissolution was performed at 60 °C using a magnetic stirrer.To the PVA resulting solution was added MPM in an amount that the ratio of elementary units of PVA to elementary parts PVP system was 16:1, 12:1, 8:1.The resulting mixture was treated with ultrasonic waves of a frequency of 22 kHz on the machine "Volna UZTA 0.4/22 OM" for 3 minutes.Then the mixture was poured into special molds to produce films with plastic lining (to facilitate removal of the finished films form) and air-dried at room temperature.Finished films separated from the form and subjected to heat treatment strove at a temperature of 150 °C for 30 minutes (fig.1).

IV. Results and discussion
For research were used compositions based on PVA and MPM (PVP:MMT = 5:1) ratio of the number of elementary units of PVA to the number of PVP elementary units in and montmorillonite-polyvinylpyrrolidone mixture as 12:1.
The introduction of modifiers delivered in the processing solutions ultrasonic waves for 3 minutes because this method of mixing ensures satisfactory distribution of particles in the composition.
The lowest values of intrinsic viscosity regardless of environment marked by pure PVA solutions.The introduction of MPM to PVA solution leads to higher viscosity of compositions which can be explained by physical interaction of montmorillonite-polyvinylpyrrolidone mixture of polymer macromolecules in solution under the influence of ultrasound (evidenced by a slight change of color compositions).
It is logical that the highest viscosity solutions are characterized by compositions with traces of sodium tetraborate resulting from the formation of intermolecular chelate compounds by interaction of the -hydroxyl of PVA groups with borate-ions.
Significant effect of pH on the viscosity of the solution of compositions.The lowest values observed intrinsic viscosity of the composition obtained in a neutral environment.Viscosity similar solution compositions in alkaline and acidic environments, virtually the same and is significantly higher.
With aim to determine the permeability and degree of structuring films based on modified PVA investigated their water absorption in cold water.Without treating all the films based on modified PVA dissolved in water independently of pH in which they are received.After heat treatment at 150 0 C for 30 minutes film based on modified PVA only swell in water but not dissolved.From Table 4 we see that the lowest water absorption of film observed PVA:MPM = 12:1, produced in an acidic environment, which correlates well with the results of the mechanical strength of the films [7].Thus, water absorption of films obtained in acidic medium, 2.5 times lower than the films obtained in a neutral environment.The films based compositions obtained in an alkaline environment also characterized by reduced water absorption, but after treating they slightly yellow, which may indicate partial destruction of PVA.It is also worth noting that films based on PVA modified MPM characterized by lower water absorption than films based on PVA modified pure MMT.So the best environment to produce structured films based on modified PVA is acidic buffer solution, a modifier -MPM ratio PVA:MPM = 12:1 (the number of elementary units of PVA to PVP).

Conclusion
Thus, experimental studies found that montmorillonitepolyvinylpyrrolidone mixture significantly affects the characteristics of the solution viscosity polyvinyl alcohol provided their mixing in the ultrasonic field.Composition of traces of sodium tetraborate in the aqueous solution of the highest rates of viscosity.Also on the viscosity of designed compositions, pH environment commits considerable influence, especially composition obtained in weakly alkaline environment with higher values of relative viscosity than compositions obtained in neutral and acidic environments.Simultaneously, water resistance and mechanical properties of films obtained in an acidic environment is best.The optimal from the standpoint of durability and water resistance is a composition of PVA:MPM=12:1 and depending on the content as MPM and pH characteristics of films based on PVA can be adjusted over a wide range, which would expand the scope..

1 .
Samples of films PVA: MPM =12:1 a -after heat treatment at 150 0 C; b -after the extracts in water for 24 hours