**1. Introduction**

430 Polyurethane

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Considering environmental protection and resolution a number of ecological problems (including problem of recourses for chemical synthesis depletion) synthesis of the biodegradable polymer materials becomes one of the most actual tasks of modern polymer chemistry. Among ways of environmental protection from polymer waste (keeping on waste deposits, burials, incineration, pyrolysis, recycling) there can be distinguished the method of minimization of ecological pollution due to creation of polymers able to be destructed under influence of natural factors such – chemical (oxygen, air, water), physical (sun light, heat), biological (bacteria, fungi) etc. These factors are very effective and lead to fragmentation of polymer as a result of macromolecule degradation and turning it into low-molecular compounds which become part of natural circuit of substance. In other words biodestruction is reliable and comparatively fast method of utilization. Usually it can be achieved by implication of natural compounds fragments into polymer structure. Other promising method is biopolymers modification with further creation of new synthetic polymers able for degradation under biological factors. Development of this method in future allows to resolve one of the most actual modern problems and to substitute petroleum refining products as the base of chemical synthesis with renewable source. It is also relevant using as reagents economically effective products which are cheaper than oil refining raw materials.

Purpose of our study was to create new polymerizing systems possessing above metioned attractive features. Therefore new polyglucanurethane (PGU) networks were obtained on the base of microbial polysaccharide xanthan and blocked polyisocyanate (PIC) using environment friendly method. Biopolymer application as reagent provides both preserving advantages of initial materials and developing new advanced properties of obtained biodegradable materials due to chemical modification. Replacement of toxic compounds

© 2012 Kozak and Hubina, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Kozak and Hubina, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

with latent isocyanate-containing reagent blocked polyisocyanate is also a prominent advantage of developed technique. PGU were obtained via interaction of xanthan hydroxyl groups and isocyanate groups of deblocked above 125oC PIC (Kozak & Nizelskii, 2002).

Polyglucanurethanes: Cross-Linked Polyurethanes Based on Microbial Exopolysaccharide Xanthan 433

respectively) and by intensity reduction of the band at 3215 cm-1 (valence vibrations of

Increasing intensity of the band at 3364 cm-1 (in characteristic doublet of N-H valence vibrations), appearance of the 1635 cm-1 band in the region of NH deformation vibrations (amide II) and changes of intensity of 1650 and 1590 cm-1 bands respond to formation of

In the wave numbers range from 3000 to 3500 cm-1redistribution is observed of the intensities of absorption bands corresponding to hydrogen linked OH-groups. That points on redistribution of intermolecular bonds in the system during polysaccharide cross-linkage

primary OH-groups in mannopyranose cycles) (Fig 2 c).

**Figure 1.** Scheme of PGU synthesis

and PGU formation.

urethane bonds and releasing of blocking agent (Fig 2b).

Microbial polysaccharide xanthan is produced by xanthomonas campestris pv. Campestris bacteria (Gzozdyak et al., 1989). Xantan is well known and most widely used microbial exopolysaccharide. It is used in light industry (textile), heavy industry (drilling and oil production) and food industry as well as in agriculture, forestry, pharmaceutics, medicine and cosmetics. The water solutions of xantane have unique rheological properties due to metal cation complexing ability and formation of primary, secondary and higher levels of structure. The main chain of the polysaccharide is alike to cellulose and its side-chains (pendants) consist of glucose, mannose and glucuronic acid residues.

Blocked polyisocyanate is latent reagent which is able to produce reactive isocyanate groups under elevated temperature. It is multifunctional latent reagent that can consist of 40 to 70 % of dimeric compound , 20 to 60 % of tetramer and 1 to 5 % of trimer and hexamer. Melting temperature interval of blocked PIC is from 80 to-95 oС, NCO-group unblocking temperature ranges from 125 to 130 oС. PIC is soluble in most of organic solvents and can be used both in powder and liquid form.
