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Natural-Based Polymers for Biomedical Applications
Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov, Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov
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eBook - ePub
Natural-Based Polymers for Biomedical Applications
Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov, Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov
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This new book presents the authors' biomedical studies of natural degradable biopolymers (polyhydroxyalkanoates [PHAs]) and discusses the demand for medical-grade materials and modern trends, focusing on the present status and future potential of PHAs. The authors present and summarize their most important results and findings obtained during the last few years in experimental studies and clinical trials of PHAs at the Institute of Biophysics Siberian Branch of Russian Academy of Science.
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Informations
Part I
Requirements for Biomaterials: The Position and Potential of Degradable Polyhydroxyalkanoates
Chapter 1
Creation and Use of Environmentally Friendly Materials as an Important Part of Critical Technologies of the 21st Century
Contents
Contents
1.1 Introduction
1.2 Bioplastics: A New Direction in Materials Science
1.3 The Need for Novel Functional Materials in Medicine
1.4 Requirements for Medical Grade Materials
1.5 Permission to Use Novel Biomaterials and Devices in Clinical Practice
1.6 Modern Medical Grade Materials
1.7 Applications of Medical Grade Materials
Keywords
References
1.1 Introduction
Development and use of new, environmentally friendly materials, which can be involved in biosphere cycles, corresponds to the idea of environmentally safe, sustainable industrial development. In Agenda 21, adopted at the special UN session on the environment and development in 1991, the stress is laid on the need for the development and application of new, ecofriendly technologies and materials (Agenda 21). Environmental protection is an integral component of sustainable development. Human economic activities threaten all biotic and abiotic components of the environment. Moreover, as noted in Agenda 21, the increasing human population produces and consumes greater amounts of chemical substances, thus, exacerbating environmental problems. In spite of the increasing efforts to bring down accumulation of wastes and recycle them, more and more damage is done to the environment by enormous amounts of wastes and unsustainable land management.
One of the priorities stated in Agenda 21 is âto prevent, halt and reverse environmental degradation through the appropriate use of biotechnology in conjunction with other technologies, while supporting safety procedures as an integral component of the program.â Specific objectives include the inauguration of specific programs with specific targets:
- 1) To adopt production processes making optimal use of natural resources, by recycling biomass, recovering energy and minimizing waste generation;
- 2) To promote the use of biotechnologies, with emphasis on bioremediation of land and water, waste treatment, soil conservation, reforestation, afforestation, and land rehabilitation;
- 3) To apply biotechnologies and their products to protect environmental integrity with a view to long-term ecological security.
Governments at the appropriate level, with the support of relevant international and regional organizations, the private sector, non-governmental organizations and academic and scientific institutions, should:
- Develop environmentally sound alternatives and improvements for environmentally damaging production processes;
- Develop applications to minimize the requirement for unsustainable synthetic chemical input and to maximize the use of environmentally appropriate products, including natural products;
- Develop processes to reduce waste generation, treat waste before disposal and make use of biodegradable materials;
- Develop processes to remove pollutants from the environment;
- Promote new biotechnologies for tapping mineral resources in an environmentally sustainable manner.
The increasing use of synthetic plastics has become a global environmental problem. Polymer materials have become an essential element of modern life, having replaced steel, wood, and glass in many applications. The term âpolymeric materialsâ encompasses three large groups: polymers, plastics, and their morphological variety â polymer composite materials (PCM), or reinforced plastics. All these materials contain a polymeric constituent, which determines their basic thermal deformation and processing properties. The polymeric constituent is a high-molecular-weight organic substance produced by the chemical reaction between molecules of the starting low-molecular-weight substances â monomers. The term polymer usually defines high-molecular-weight substances (homopolymers) supplemented with stabilizers, plasticizers, lubricants, antirads, etc. Physically speaking, polymers are homophase materials, which retain all physicochemical properties of the homopolymers. Plastics are polymer-based composite materials, containing disperse or short-fiber fillers, pigments, and other free-flowing ingredients. Fillers are not present in the continuous phase. They are dispersed in the polymeric matrix. Plastics are heterophase isotropic (having the same properties in all directions) materials.
Plasticts are used in almost all areas of human activity (Table 1.1). About 60% of all synthetic plastics used for packaging are polyethylenes. They are low-cost materials and show excellent performance in various applications. High-density polyethylene (HDPE) has the simplest structure of all plastics, consisting of repeating units of ethylene, (âCH2âCH2â) n. Low-density polyethylene (LDPE) has the same chemical formula, but it has a high degree of chain branching: (CH2CHR)n, in which R may be âH, â(CH2)nCH3, or a more complex structure with secondary branching.
Synthetic polymers (nylon, polyethylene, polyurethane) have revolutionized our way of life, but they have also created a number of problems. First, resources used to produce synthetic polymers are nonrenewable and, second, the application of polymers that cannot decompose in the natural environment and their accumulation lead to environmental pollution, presenting a global ecological problem. Outputs of synthetic plastics that do not decompose in the natural environment, mostly polyolefins (polyethylenes and polypropylenes), and are manufactured in processes of petroleum synthesis are huge: their annual production has reached 330 million tons,
Market sector | Product | Application area/consequences |
| ||
Packaging | Packs, films | Food package. |
Bottles, trays, plasters | Difficult recycling | |
Hollow containers | Short lifetime of packaged food | |
Nets, bags | ||
Fast Food | Dishes | Recycling may be impossible or expensive. |
Cutlery | ||
Plugs, lids | Products are often biologically contaminated through contact with food | |
Drinking straws | ||
Cups | ||
Fibers/textiles | Clothes | "Breathing" cloth |
Technical textiles | Tactile properties | |
Fabrics | Luster | |
Toys | Artificial materials | Educational advantages |
Bricks and blocks | Environment | |
Golf tees | ||
Motor car construction | Car floor mats, car parts | |
Everyday use | Trash bags | Short lifetime of the product |
Fibers and nonwovens | ||
Personal hygiene products | Difficult recycling | |
Cosmetic containers, containers for powders, lubricants, etc. | ||
Golf tees | ||
Adhesives, paints, coatings | ||
Gardening | Plant pots | Better compostable |
Supports | Very difficult recycling due to contamination | |
Peat bags | ||
Fertilizer strips | Cheaper manpower | |
Bonding materials | ||
Agriculture | Film covers | Vegetable-growing, horticulture |
Mulching films | ||
Protective films | ||
Medicine | Implants | Safe residence and degradation in the body |
Medical packaging | ||
Surgery materials | Short lifetime of the product | |
Personal hygiene products | Disposable product | |
Gloves | ||
Other | Filters | Specific advantages |
Assembly technologies | Cost reduction | |
Burial | Compostablity requirements | |
Desk sets | ||
Electronics | DVD, computer cases | |
Coatings for office equipment, video and audio equipment | ||
Cases for mobile phones |
* Adapted from Fomin, Guzeev, 2001; the Data of Biodegradable Materials Interest Community Association; COPA Forecast.
increasing by about 25 million tons every year. In developed countries, no more than 16â20% of them are recycled, and they largely accumulate in landfills.
The main approaches of the plastic refuse policy are now landfilling and reclamation. Polymer landfilling is a time bomb, and this problem will have to be solved by the future generations. Moreover, up to 10,000 ha of the land, including agricultural fields, is annually occupied by new landfills. A possible way to reduce enormous amounts of plastic refuse is reclamation, which can involve several solutions: incineration, pyrolysis, recycling, and reprocessing. However, neither incineration nor pyrolysis of plastic containers and other plastic items can essentially improve the state of the environment. Moreover, incineration is a very costly process, releasing highly toxic and super-toxic compounds (such as furans and dioxins). Recycling is some solution, but it involves considerable labor and energy expenditures: plastic packaging items and containers have to be picked out of the household garbage; different plastics should be separated, washed, dried and disintegrated; only then, they can be processed to fabricate a new end item.
Some countries have passed legislation that plastic waste, plastic packaging items and containers in particular, must be obligatorily collected and recycled. For instance, the European Union Directives stipulate that manufacture of plastic packaging must involve 15% recycled plastics; in Germany, this quota is 50% and must increase to 60%. Landfilling and incineration cannot solve the problem of reusing millions of tons of synthetic plastic refuse, and their accumulation in the biosphere can lead to a global environmental disaster. A solution to this problem is to create and use new types of materials that are naturally degraded in the environment into harmless components. This solution grows in popularity as oil and gas prices increase. In contrast to oil, polymers prepared from natural raw materials or synthesized by microorganisms (the so-called biopolymers, or bioplastics) do not contribute to greenhouse gas increase and global warming. Moreover, they can facilitate regeneration of the carbon cycle, or âcarbon reincarnation.â Petroleum-based polymers may also be regarded as renewable materials, but it will take more than one million years for the biomass to be converted into fossil fuels, which may be used to produce plastics. As the level of consumption of plastics is much higher than the level of renewal of fossil carbon resources, the carbon cycle is not in balance. By contrast, bio-based biodegradable polymers, which are produced from renewable plant material and microbial biomass, can be produced and recycled over comparable time periods. Therefore, countries developing this approach are exempt from emission quotas under the Kyoto Protocol. The European Union undertook to reduce CO2 emissions by 8% relative to the level of 1990, by 2012. Japan undertook to reduce CO2 emissions by 6%.
In 2000, t...