Thermogravimetric and FTIR studies of chitosan blends
Introduction
In view of a growing amount of wastes from man-made fibers, research projects are concentrated now on searching for polymer materials which would be man- and environment-friendly and characterized by a definite lifetime. Their degradation in various environmental conditions leads to a destruction of chains by breaking, splitting of fragments of the main chain or side constituents and release of volatile products.
For many years, chitosan (CH) being a deacetylated form of chitin which occurs in various ecosystems has aroused great interest of researchers. Because of its unique properties [1], [2], [3], [4], [5] such as bioactivity or biodegradability [6], [7], [8], it finds application in many areas of man’s life and health [9], [10], [11], [12]. The search for new applications calls for developments in the production methods, investigations of the structure [5], [13] and degradability of CH and blends that contain CH [14], [15], [16], [17], [18], [19].
The study aims at the estimation of thermal stability of biodegradable blends of CH with polyvinyl alcohol (PVAL), starch (S) and hydroxypropylcellulose (HPC) obtained from a solution in the form of transparent, homogeneous films. To record the process of thermal degradation of CH and its blends, the methods of thermogravimetry (TG) and infrared spectroscopy (FTIR) were used. The analysis of results was used to describe the degradation kinetics of CH and its blends. Important elements of the kinetic model of degradation are the values of activation energy and reaction order.
Section snippets
Materials used
CH (poly-2-aminoglucose) of deacetylation degree DD=78% and molecular weight M=2.1×105, was produced by the Sea Fishery Institute in Gdynia. It is a biodegradable natural copolymer obtained by chitin modificationwhere x is the number of deacetylated monomeric units, and y is the number of chitin monomeric units.
S, potato starch was a commercial product. It is a recoverable biopolymer composed of amylopectin and amylose
PVAL of molecular weight M=7.2×104 (Polskie Odczynniki Chemiczne,
Interactions between components
Formation of homogeneous CH blends with PVAL, S and HPC is a result of strong interactions by hydrogen bonds between the functional groups of the blend components in which amino and amide groups present in CH take part. The analysis of FTIR spectra of the blends enables these interactions to be identified [22], [23].
On the basis of the harmonic oscillator model the reduction in force constant Δf can be represented by Eq. (1) [24]where μ=m1m2/(m1+m2) corresponds to the
Conclusions
- 1.
Both dynamic and isothermal thermogravimetric analysis of CH and its blends with HPC, PVAL and S revealed improving stability of CH in the blends.
- 2.
With an increase of the amount of S, PVAL and HPC in the blends an increase of Tp and Tmax is observed. It is most distinct for CH/HPC and CH/PVAL blends. These blends reveal two stages of fast decomposition characteristic of both components. A certain increase of the activation energy of CH degradation calculated on the basis of TG analysis is
Acknowledgements
The authors gratefully thank the Scientific Research Committee (KBN) in Poland for support under grant no. 3 T09C 028 19.
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