Polyvinyl Alcohol with High Thermal Stability
Power-Saving with Increased Ecological Safety Technology of Synthesis of High Molecular Weight Thermostable Polyvinyl Alcohol for Obtainment of Membranes for Fuel Cells, Fiber, Cryogels
Tech Area / Field
- CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
- CHE-POL/Polymer Chemistry/Chemistry
- MAT-ELE/Organic and Electronics Materials/Materials
3 Approved without Funding
Yerevan Institute "Plastpolymer", Armenia, Yerevan
- National Polytechnical University of Armenia, Armenia, Yerevan
- Benjamin Moore & Co., USA, NJ, Flanders\nCNRS / Université de Rouen, France, Mont Saint Aignan\nNational Research Council, Italy, Rome\nThe Dow Chemical Company, USA, TX, Freeport\nHeriot-Watt University, UK, Edinburgh\nUniversity of Turin / Department of Chemistry IFM, Italy, Torino
Project summaryPolyvinyl alcohol (PVA) has found a wide application in various fields – from medicine to robotics owing to its chemical stability and easy modification of the polymeric matrix. High molecular weight (HMW) PVA has been used in recent years to obtain membranes for various technological purpose, including also special membranes for fuel cells, to obtain high modulus fiber for composition materials and means for antiballistic defense, as well as to obtain cryogels, used, particularly, in medicine and biotechnology as carriers of biologically active systems.
Fuel cells (FC) are considered to be energy sources of future and they rouse great interest all over the world.
Service conditions and efficiency of FC on the basis of hard polymeric electrolytes of PEMFC typeare predetermined a lot by nature of the used polymer. FC, based on the use of carbon-chain polymers to which belongs PVA as well, have not high operating temperature and increase of thermal stability of the polymeric matrix is extremely actual.
Thus, for application in all the above fields, high demands are claimed for PVA and optimum relation of such characteristics of the polymer as thermal stability, strength and solubility in water is of importance and the use of HMW modified PVA proposed by us could favor obtainment of products with increased strength and thermal characteristics.
The objective of the presented project is the synthesis of HMW PVA with high thermal stability for application in the production of membranes for FC, high-strong fiber and cryogels and also obtainment of new surface active agents (SAA) on the basis of HMW modified PVA for application as high-effective emulsifiers, stabilizers and thickeners.
This aim is achieved by obtaining HMW copolymers of vinyl alcohol with comonomers, which favor improvement of thermal characteristics of the polymer at the same time retaining positive properties typical for PVA. Preliminarily copolymerization of vinyl acetate (Vac) is realized with the selected comonomers in aqueous medium in the presence of redox initiating system based on ammonium persulphate (AmP). In recent years we succeeded in revealing some possibilities of this initiating system, which were not established before, and enlarge temperature ranges of its use. Its application under new conditions allowed us to obtain PVAc with considerably higher molecular weigh than for PVAc obtained by us earlier in the presence of the initiating system based on manganic tris-acetylacetonate (MTA) under ISTC project A-359. Use of the redox system based on AmP under new, more optimum conditions and application of (co)monomers allowing to increase the thermal stability of the synthesized copolymers of VAc favor obtainment of HMW modified PVA with a set of properties necessary for its successful use in new directions.
Conduction of synthesis of PVAc and PVA in aqueous medium at moderate temperatures excludes environment pollution with toxic and fire hazardous solvents widely used in usual technological schemes of PVA production, and the presented project, thus, allows to solve this task based on power saving technology with increased ecological safety.
Testing of the worked out processes is foreseen on a pilot plant with maximum approach to industrial conditions in view of making more exact the technological parameters of polymerization and hydrolysis, as well as compulsory turning out samples of HMW modified PVA for conducting tests at the producers’of membranes, fiber, gels etc.
Yerevan Institute “Plastpolymer” was a head organization in the USSR, responsible for working out and introducing technologies connected with the production and application of VAc and polymers on its basis. All the employees of the institute, whose participation is proposed in this project, worked earlier under Project A-359. The results of investigations connected with carrying out Project A-359 were presented at various conferences and published in specialized editions.
In the Department of Chemical Technologies and Environmental Engineering of the SEUA researchers are being conducted regarding ecological assess of the existing productions, as well as investigations regarding working out of new technologies with increased ecological safety. Part of the employees of this institute also took active participation in conducting works under ISTC Project A-359. In this project certain information will be used received in the result of realizing ISTC Project A-359. On the whole these projects essentially differ from each other both in the main objective and in method of achieving it.
Expected Results and Their Application
The presented project refers to the category of technology development “Applied research”. As a result of realization of the project, a technology used in industry will be set up. The most important anticipated results which will be received at conducting the project:
- Results of kinetic investigations of the process of (co)polymerization of VAc in the presence of redox system based on AmP in a wide range of initial temperatures and without using inert gas;
- Mathematical models describing effect of the main components of the reaction system and parameters of the technological process on emulsion (co)polymerization of VAc and saponification of VAc (co)polymers, as well as on the main quality characteristics of the final HMW modified PVA
- Results of study of dependence of molecular-structural characteristics of modified PVA on saponification method;
- Data on effect of the chemical composition and molecular-structural characteristics of HMW PVA on physical-chemical, physical-mechanical,thermophysical properties of the polymer and on rheological characteristics of its aqueous solutions;
- Data on phase equilibrium of the system PVA-water for modified PVA in a wide range of change of its molecular-structural characteristics (molecular weight -100-700 thousand; content of residual acetate groups -1,0-20,0 mass.%).
- Obtainment of new marks of thermal stable HMW PVA to use in the production of membranes for FC, high strong fiber and cryogels with high operating characteristics;
- Obtainment of new SAA on the basis of HMW PVA which can be used as emulsifiers, stabilizers and thickeners.
Industrial, ecological and economical:
- Cutting of PVA expenses at using SAA on the basis of HMW PVA as emulsifiers and protective colloids at polymerization of vinyl chloride, styrene, VAc etc, also as thickeners of aqueous solutions and water-emulsion paints;
- Decrease of fire and explosion risk of the production and reduce of exhausts of organic compounds into the environment due to conduction of the processes at reduced and moderate temperatures in aqueous medium.
Meeting ISTC Goals and Objectives
The project favors realization of the objectives and tasks of ISTC, since:
- Gives scientists and specialists from CIS who dealt with weapons before possibilities to reorient their abilities for peaceful activity;
- Encourages integration of scientists from countries of CIS into international scientific cooperation;
- Supports applied researches for peaceful purposes, especially in the field of protection of the environment and power saving technologies;
- Supports transfer to market economy, that meets civil needs.
Scope of Activities
Investigation Tasks and their main stages:
1. Investigation of the process of synthesis of HMW VAc (co)polymers by emulsion polymerization method:
- Effect of synthesis conditions on the (co)polymerization process and quality characteristics of VAc (co)polymers;
- Working out of the mathematical model of the synthesis of HMW VAc (co)polymers;
- Study of molecular-structural and thermal characteristics of the selected samples of VAc (co)polymers.
- Study of methods and parameters of the hydrolysis process and working out of the mathematical model of the process;
- Study of interrelation between the method of synthesis of VAc (co)polymers and quality characteristics of PVA;
- Study of the synthesis of modified PVA with various content of residual acetate groups.
- Study of molecular structural and thermal characteristics of HMW modified PVA, as well as its aqueous solutions;
- Investigation of conditions of application of synthesized samples of HMW PVA as SAA and protective colloids and also when obtaining cryogels and membranes.
- Reconstruction of the pilot plant and synthesis of enlarged batches of modified PVA which differ in molecular mass and chemical composition for studying fields of application;
- Turning out of the selected samples of HMW modified PVA for conducting the required tests at the collaborators’.
Role of Foreign Collaborators
The scope of cooperation with foreign institute(s) within the limits of the proposed project:
- Exchange of information and giving comments on technical reports.
- Holding joint working seminars.
- Rendering assistance to the participants of the project to attend international conferences.
- Additional testing of modified PVA on the equipments of the collaborators (in case they take interest in it).
Technical Approach and Methodology
At synthesis of VAc (co)polymers, which are bases for modified PVA, emulsion polymerization method of vinyl monomers in aqueous medium, using high effective redox initiating systems will be used, and at synthesis of PVA – methods of acidic and alkaline hydrolysis, as well as catalytic alkaline alcoholysis. It is planned to widely use the method of mathematical modeling with aim to receive mathematical models of the studied processes.The synthesized (co)polymers, their aqueous dispersions and solutions will be characterized on the basis of standard methods accepted in CIS for corresponding polymers. The final samples of polymers will be studied by methods of gel permeation chromatography, light scattering, differential thermal analysis and thermogravimetry, roentgenography, viscosimetry etc. It is supposed to test the selected batches of HMW PVA in the laboratories of collaborators who take interest in it by using special methodology used in concrete fields of application (membranes, fiber, cryogels).