Modern research and technology approaches to the production of biodegradable polymeric materials based on renewable resources have been reviewed. It has been found that films prepared of cellulose, chitosan, gelatin, polypeptides, casein, soy, wheat, corn, rice, and maize are being commonly used at present. The structural and mechanical properties and micromorphological features of hydrocolloids of vegetable origin promising for the production of biodegradable polymers—starches, pectins, carrageenans, and agar—have been studied. It has been determined that, with respect to strength and suitability for use in films of individual components, all the studied hydrocolloids can be arranged in ascending order as follows: starches, carrageenans, pectins, agar. According to analysis of the structural and mechanical properties of the films, it has been shown that the best parameters are found for the samples based on pectin P1 and agar A2. The breaking stress for these materials is 52 and 77 MPa, respectively. The breaking strain is 11.5 and 8.0%, respectively. Analysis of the micromorphology has revealed the formation of surface microdiscontinuities in the films based on high methoxyl pectins P1 and P4 and unmodified corn starch S3 and the formation of wavy folds in the case of the films of kappa-carrageenan C1; these folds are formed during drying and decrease the tensile strength of the respective films. The found features will be used in the development of technologies for the production of biodegradable polymeric materials based on hydrocolloids of vegetable origin with enhanced performance and processing characteristics.
biodegradable materials, hydrocolloids, starch, pectin, agar, carrageenan, micromorphological properties, mechanical properties
INTRODUCTION
The important environmental issues that are extensively discussed at the present day include the salvation of nature from debris, the direction of development of the industry of biodegradable polymeric materials, and the rates of annual output [1-4].
It is known that most of the plastics used in the global production are based on products of processing of hydrocarbon-containing raw materials (propylene, ethylene, and other organic compounds). However, the further focusing on these technologies is attributed to the rise in prices for hydrocarbon-containing raw materials and negative impacts on the environment. In addition, the amount of plastic waste also increases; the waste disposal requires studies on the development of technologies for the production of stable biodegradable plastics for various purposes. This direction is consistent with the modern concept of improvement and development of the production of useful goods from waste. These raw materials include biological waste; prior to use, it must be processed and modified by physicochemical methods [5].
The previous studies were primarily focused on the design of polymeric materials that are resistant to environmental factors. At present, there is a new approach to the development of polymeric materials; it is based on maintaining their performance characteristics only in the period of their use. Despite all the difficulties faced by scientists, this direction of polymer materials science is part of their research interests, as evidenced by recent publications [6].
Modern biopolymers can be produced from both renewable natural resources and conventional raw materials, i.e., petrochemicals [7]. At present, films based on natural biodegradable polymers, such as cellulose, chitosan, gelatin, polypeptides, casein, and soybean, are commonly used in the food industry [8-11]. Of particular interest is starch because it is the cheapest raw material and the main sources of its industrial production are potatoes, wheat, corn, rice, maize, and some other plants [12-14].
Russian scientists have developed approaches to the preparation of biodegradable polymers based on enzymatic hydrolysate of keratin waste [15].
A research trend of high priority is the development of new approaches to the production of biodegradable polymers exhibiting a high rate of biodegradation, enhanced performance characteristics, and a low cost.
The aim of this study is to analyze the structural and mechanical properties and micromorphological features of polymer films based on hydrocolloids of vegetable origin that are used for the production of biodegradable polymers.
1. Fomin, V.A. and Guzeev, V.V., Biorazlagaemye polimery, sostoyanie i perspektivy ispol´zovaniya (Biodegradable polymers: State-of-the-art and prospects), Plast. Massy (Plastics), 2001. № 2. P. 42.
2. Buryak, V.P., Biopolimery. Est´ li al´ternativa? (Biopolymers: Is there an alternative?), Polim. Mater. (Polym. Mater.), 2006. № 1. P. 32.
3. Vlasov, S.V. and Ol´khov, V.V., Biorazlagaemye polimernye materialy (Biodegradable polymer materials), Polim. Mater. (Polym. Mater.), 2006. № 7. P. 23.
4. Shah, A.A., Hasan, F., Hameed, A., and Ahmed, S., Biological degradation of plastics: A comprehensive review, Biotechnol. Adv., 2008. V. 26. P. 246.
5. Arshakyan, A.D., Rozanova, E.N., Kometiani, I.B., and Grekhneva, E.V., Per´evoy keratin v sinteze biorazlagaemykh polimernykh materialov na osnove akrilamida i metilmetakrilata (Feather keratin in synthesis of biodegradable polymer materials based on acrylamide and methyl methacrylate), Uchenye Zapiski: Elektron. Nauchn. Zhurn. Kursk. Gos. Univ. (Sci. Notes: Electron. Sci. Journ. Kursk. State Univ.), 2013. V. 2. № 3 (27) (scientific-notes.ru/pdf/032-020.pdf).
6. Pavelzhak, R., Upakovka iz kukuruzy - fantastika ili real´nost´ (A pack of corn: Fiction or reality), Paket (Packaging), 2006. № 5. P. 40.
7. Buryak, V.P., Biopolimery nastoyashchee i budushchee (Biopolymers: Present and future), Polim. Mater. (Polym. Mater.), 2005. № 11 (78). P. 8.
8. Rinaudo, M., Chitin and chitosan: Properties and applications, Prog. Polym. Sci., 2006. № 1. P. 603.
9. Zhang, J.W. and Chen, F., Development of novel soy protein-based polymer blends, Green Polym. Chem.: Biocatal. Biomater., 2010. № 1043. P. 45.
10. Ofokansi, K., Winter, G., Fricker, G., and Coester, C., Matrix-loaded biodegradable gelatin nanoparticles as new approach to improve drug loading and delivery, Eur. Journ. Pharm. Biopharm., 2010. № 76 (1). P. 1.
11. Averous, L., Polylactic acid: Synthesis, properties and applications, in Monomers, Oligomers, Polymers and Composites from Renewable Resources, ed. by Belgacem, N. and Gandini, A. (Elsevier, Amsterdam, 2008). P. 433.
12. Suvorova, A.I., Tyukova, I.S., and Trufanova, E.I., Biorazlagaemye polimernye materialy na osnove krakhmala (Biodegradable polymeric materials based on starch), Usp. Khim. (Russ. Chem. Rev.), 2000. V. 69. № 5. P. 498.
13. Averous, L., Biodegradable multiphase systems based on plasticized starch: A review, Journ. Macromol. Sci., Part C: Polym. Rev., 2004. № 44 (3). P. 231.
14. Martin, O., Averous, L., and Della Valle, G., In-line determination of plasticized wheat starch viscoelastic behavior: Impact of processing, Carbohydr. Polym., 2003. № 53 (2). P. 169.
15. Filimonov, I.S., Loginov, D.S., Trushkin, N.A., Ponomareva, O.A., and Koroleva, O.V., Sozdanie biorazlagaemykh polimerov na osnove fermentativnogo gidrolizata keratinsoderzhashchego syr´ya (Design of biodegradable polymers based on enzymatic hydrolysate of keratin-containing raw materials), Sovr. Probl. Nauki Obraz. (Mod. Probl. Sci. Educ.), 2012. № 6. P. 8.
16. Pose, S., Kirby, A.R., Mercado, J.A., Morris, V.J., and Quesada, M.A., Structural characterization of cell wall pectin fractions in ripe strawberry fruits using AFM, Carbohydr. Polym., 2012. № 88 (3). P. 882. doihttps://doi.org/10.1016/j.carbpol.2012.01.029.
17. Austarheim, I., Christensen, B.E., Hegna, I.K., Petersen, B.O., Duus, J.Ø., Bye, R., Michaelsen, T.E., Diallo, D., Inngjerdingen, M., and Paulsen, B.S., Chemical and biological characterization of pectin-like polysaccharides from the bark of the Malian medicinal tree Cola cordifolia, Carbohydr. Polym., 2012. V. 89. № 1. P. 259.
