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6УДК 544-971:66.014 N.V. Sirotinkin1 ,V.A. Alekseeva2
PROLONGATION EFFECT OF CHEMICAL COLD PACK BY WATER-SOLUBLE POLYMERS
St. Petersburg State Institute of Technology (Technical University), Moskovsky Pr. 26, St Petersburg, 190013, Russia e-mail: vilenaalekseeva@gmail.com
We have investigated the influence of water-soluble polymers such us starch, upon the endothermic effects of ammonium nitrate (NH4NO3) water solution. The results show that the dissociation of NH4NO3 in starch water solution improved the prolongation effect and intensity of the cooling effect.
Key words: instant cooling effect, chemical cold pack; dissociation ammonium nitrate; water-soluble polymers, prolongation effect.
Introduction
Main purpose of the investigation is to extend the lifetime of cold pack. Instant cooling effect that is provided by an endothermic reaction of dissociation ammonium nitrate (NH4NO3) of water solution is widely used now. This method is often used for local cryotherapy. Local cryotherapy (LC) - is the effectiveness of curing the area of injure by cooling. Method LC —is the compact chemical cold pack with prolongation effect. This pack starts to work when it's surface begins to cool by interaction of reactions in the water. Today the LC system is an integral part to prevent the inflammation in wounds before surgical treatment in case of emergency for the army, MES, athletes' extremists. Thus, the solution of such problem as an attempt to transform system of cold pack is very relevant nowadays. The history and perspective usage of hypo-thermal system of prolongation effect in medicine was published earlier [1]. Cold pack provides an endothermic reaction by mixing the components. The cold pack comprise a container a container having first and second compartments separated by a barrier, which can be opened to mix the contents of the compartments.
The first compartment contains a granular solid of an ammonium nitrate salt and the second compartment contains an aqueous solution. When the contents of the compartments are mixed, the granular components dissolve in the aqueous solution producing an endothermic reaction [2].
The mechanism of dissociation ammonium nitrate in water mentioned before is used in commercial prototypes such us «Snegok», «Appolo» etc. However, the main disadvantage of such devices is the absence of prolonged effect.
Second, to solve the problem of prolongation which was identified on earlier work done by Ryatkyanen [3-4]. She suggested the micro-capsulation of granular component and portion the dissolve of NH4NO3 in an aqueous solution. Micro-capsulation— is a process of coating of granular particles by water-soluble polymers.
Н.В. Сиротинкин, В.А. Алексеева
ПРОЛОНГИРОВАНИЕ ДЕЙСТВИЯ КРИОПАКЕТОВ ВОДНЫМИ РАСТВОРАМИ ПОЛИМЕРОВ
Санкт-Петербургский государственный технологический институт (технический университет). Московский пр., 26, Санкт-Петербург, 190013, Россия e-mail: vilenaalekseeva@gmail.com
Было исследовано влияние водорастворимых полимеров на эндотермический эффект в водном растворе нитрата аммония. Результаты показали, что наблюдается значительное улучшение пролонгирования реакции и интенсивности охлаждения, диссоциации нитрата аммония в водном растворе крахмала, по сравнению с водным раствором.
Ключевые слова: криопакет; диссоциация нитрата аммония; водорастворимые полимеры; пролонгирование реакции.
However, micro-capsulation is a very difficult technology and what is more it increases the price of the product.
This work is dedicated to investigate the effects of prolongation by rheology of polymers. It is also the first work where water-soluble polymers were used as additives in the system ammonium nitrate and water.
There are well known factors that influence on rhe-ology of polymers in water- soluble of NH4NO3, such us viscosity of water-soluble polymer solution; viscosity of water-soluble polymer solution with NH4NO3; pH solution; chemical composition. There earlier mentioned data have been investigated in this work.
Purposes of the study
To determine if the viscosity is a real measurement that increases the period of the study that is being researched.
To determine which of the data provides the prolonged effect of the system.
To compare the polymer solution with the original solution: to find out if the minimum temperature value changes? How do the polymer molecules influence on the dissociation of salt?
Does the time when the temperature is on it's minimum increase with the growth of concentration?
How does the time interval of the temperature rise to it's maximum change with the growth of concentration?
What effects can be observed during this time interval? And how they depend on the concentration?
Experiments
Water-soluble polymer such as the starch was used for preparation of the system. 90 g. NH4NO3 to dissolve in 50 ml. of water. The diapason of polymer concentration is mol/l: 0.05^0.12. The point of the experiments was to determine the temperature and to fix the time of minimum and maximum of
1 Sirotinkin Nikolay V., Dr Sci. (Chem.), dean of faculty chemical and biochemical technology, Professor of department of chemistry and technology of rubber e-mail: biotechnology_faculty@technolog.edu.ru
Сиротинкин НиколайВасильевич, декан факультета химической и биотехнологии, д-р хим. наук, профессор каф. химии и технологии каучука и резины e-mail: biotechnology_faculty@technolog.edu.ru
2 Alekseeva Vilena A., postgraduate student of department of chemistry and technology of rubber, e-mail: vilenaalekseeva@gmail.com Алексеева Вилена Андреевна, аспирант каф. химии и технологии каучука и резины, e-mail: vilenaalekseeva@gmail.com
Received December 12, 2014
Дата поступления 12 декабря 2014 года
the temperature during the whole endothermic reaction in the condition of different concentration of the polymer. The experiments was carried out in the laboratory in normal condition. Characteristic viscosity was determine with the capillary viscometer VPG-2, diameter of the capillary 1,31 mm. It's principle is described by Poiseuille's law [5]. The pH value was measured by pH-meter «ANION 4100».
Results and discussion
At first we proceeded from the conception of diffusion inhibition of the process of dissociation in condition of increased viscosity. As evidence, we attempted to search the cooling time depending on the viscosity and concentration of solution.
Table 1. Experimental data of NH4 NO3 with polymer and solution without polymer.
The concentration of solution polymer C, mol/l 0.05 0.09 0.1 0.12 Solution without polymer
Minimum temperature Tmin, °C 5 2 -3 -1 5
The time when the temperature is on it's minimum Tmin, min 2 2 3 3 6
The time when the temperature is on it's maximum Tmax, min 80 100 115 145 90
pH 5,66 5,6 5,65 5,65 5,63
The kinetic viscosity of system starch-water, cSt 4 32 87 93 1,011
The kinetic viscosity of system solution-ammonium nitrate, cSt 1,3 3 6 4 1,011
It was determine, that the Tmin of solution in normal condition has been decreased to 8 in comparison with system NH4NO3 in water (table 1). It is noticed, that the cooling time is increased with the growth of soluble polymer, except from the weak concentration 0.05-0.07 mol/l. In low concentrated solution the cooling time decreases, and the viscosity has no differ with the viscosity of the water. The practical significance of this experiment is that the increase in cooling time is achieved if the viscosity of the solution increases to one times.
The observation showed that with the change of the concentration of polymer solution the cooling time and the Tmin at the system salt soluble change. The Tmin of the system is achieved only in case of the polymer concentration (0.05-0.07 mol/l) at 5 °C and has no differ from the original value. In the condition of low concentration, we can observe monotonic decrease of temperature. This effect has no explanation from the point of rheology polymer view.
For analysis of observed fact we have proposed to separate cooling time into 2 constituent: the time when the temperature is on it's minimum - Tmin, and the time when the temperature is on it's maximum - Tmax:
Tmax _ Tmin + (Tmax — Tmin)
(1)
The data of table 1 show that in condition of small concentration the Tmin of solution has no differ from the value, received in aqueous solution. With the growth of concentration of polymer, the Tmin decreases. The time when the temperature is on it's minimum in the solution is lower than in aqueous solution, that signifies about the acceleration of dissociation influenced by polymer. Increase of the cooling rate (Tmin) decreases the temp of heat loss, but the time when the temperature is on it's original increases.
The data obtained allows to suppose that the reason of additional absorption of heat is the acid hydrolysis of starch to D-glucose in the system [6]:
The indecent evidence of suggested mechanism can be as comparison of viscosity water solution of polymers and polymer solution with ammonium nitrate (Table 1). With the decrease of pH in solution with the polymer (Tablel) it's likely to have 2 different reaction: depolymerization of starch and dissociation of NH4NO3 in the solution. The rate of depolymerization of starch in solution with NH4NO3, is likely to influence on the whole rate of reaction. This can be proved by the behavior of system, significant reduction of the time when the temperature is on it's minimum can be in diapason of higher concentrations, see table 1.
The data of Table 1 is obtained in condition of normal temperature. To evaluate the efficiency of cold pack in real condition you can find the results in Table 2,3 with the experiment of beginning temperature 30 and 40, which is close to human body temperature.
Table 2. Experimental data of system: solution- NH4NO3, water solution- NH4NO3 at Tconst = 30 °C
The concentration of solution polymer C, mol/l 0.05 0.09 0.1 0.12 Solution without polymer
Minimum temperature Tmin , °C 8 10 9 10 11
The time when the temperature is on it's minimum Tmin , min 0.5 0.5 0.5 0.08 0.08
The time when the temperature is on it's maximum Tmax , min 40 35 45 40 15
The kinetic viscosity of system starch-water, cSt 3,6 32 72 44 0,801
Table 3. Experimental data of system: solution- NH4NO3, water solution- NH4NO3 at Tconst = 40 °C
The concentration of solution polymer C, mol/l 0.05 0.09 0.1 0.12 Solution without polymer
Minimum temperature Tmin, °C 5 13 8 20 15
The time when the temperature is on it's minimum Tmin, min 0.3 0.3 0.5 0.08 0.5
The time when the temperature is on it's maximum Tmax , min 30 65 60 50 35
The kinetic viscosity of system starch-water, cSt 3 32 52 30 0,658
NH4NO3 S NH4- + NO3+ (C6HioO5)n + n H2O ^ nC6Hi2O6 - Q
(2) (3)
The data of Table 2,3 shows that with increase of temperature, the rate of dissociation ammonium nitrate in the solution increases. This can be proved by reduction of value pH. This observation influences on the time when the temperature is on it's minimum and maximum in comparison with the condition of normal temperature.
The dependence of the time when the temperature is on it's minimum from the viscosity - is the result of diffusion inhibition on the degree of dissociation in researched system. It can be observed in Table 2, 3. It is evidently, that the viscosity of system starch-water with increase of temperature decreases and the time when the temperature is on it's maximum decreases, in comparison with system in normal condition. On interval of the time when the temperature is on it's maximum occurs process of «heating system», can be observed in tough water prolongation effect of system [7-8]. Also you can observe increase of the time when the system begins to heat.
Conclusions
The new mechanism of prolongation effect of cold pack was proposed.
It involves:
1. The diffusion inhibition of dissociation of ammonium nitrate in the solution of starch;
2. The separation of duration in to the time when the
temperature is on it's minimum and the «heating time»;
3. Starch depolymerization when the level of pH is lower than 7.
As the result, the duration of chemical cold pack in normal conditions has increased from 90 min. to 140 min. and at 40 °С from 35 min. to 70 min.
References
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