Material properties of biodegradable polymers

M BHATTACHARYA, University of Minnesota, USA, R L REIS, V CORRELO and L BOESEL, 

A second area of appUcation for biodegradable polymers is in the field of medicine. It is desirable that an implant not require a second surgical procedure for removal. A bone fracture is often treated by fixating the bone with a rigid 

Carbon-dioxide Carbon-dioxide/methane Molecular weight Oxygen/carbon -dioxide Carbon-dioxide Physical properties Carbon -dioxide/ Methane Physical properties 

Physical properties Carbon -dioxide/ Methane Oxygen 

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M. Bahattacharya, R. L. Reis, L. Correlo and L. Boesel, Material Properties of Biodegradable Polymers, in Biodegradable Polymers for Industrial Applications, ed. R. Smith, Woodhead Publishing Limited, Cambrige, England, 2005, p. 336. 

The solution is a combination of aliphatic polyesters and aromatic polyesters. This involves modifying the crystalline structure of PBT by incorporating aliphatic monomer (adipic acid) in the polymer chain in such a way that the material properties of the polymer would remain acceptable (e.g., melting point of the crystalline range still around 100 °C), but the polymer would also be readily compostable/biodegradable. In this way it was possible to combine the degradability of aliphatic polyesters with the outstanding properties of aromatic polyesters. 

The above mentioned scaffolds were made completely of the ceramic materials. Other potential materials which could be used to fabricate a novel construct for the repair of ciitical-sized bone defects is a novel material made of biodegradable polymer reinforced with ceramics particles. The properties of such a composite depend on 1) properties of the polymer used for the matrix and properties of the ceramics used for the reinforcement, 2) composition of the composite (i.e. content of ceramic particles) and 3) size, shape and arrangement of the particles in the matrix. Several polymer-composite composites have been used for scaffolds fabrication including polylactide (PLA) and polycaprolacton (PCL) reinforced with calcium phosphate (CaP) micro and nanoparticles. Authors proposed a novel composite material by blending copolymer -Poly(L-lactide-co-D,E-lactide) (PLDLLA) a copolymer with a ceramic - Tri-Calcium Phosphate... 

An innovative strategy to enhanee the mechanieal properties of biodegradable polymers is the ineorporation of nanomaterials as fillers within polymer matrices. With the appropriate modifications to facilitate dispersion into polymers and to enhance interactions with the snrronnding matrix, nanocomposites have demonstrated improved mechanical properties compared with unfilled polymers or polymers loaded with larger, micrometersized particles. A few studies have also shown enhanced cell function when bone cells are cultured on nanophase ceramic materials. 

Lukanina, J. K. Khvatov, A. V. Kolesnikova, N. N. Popov, A. A. Structure and properties of biodegradable polymer composite materials. Progress in chemical and biochemical physics, kinetics and thermodynamics, 2008,209-218. 

Nonetheless it will be useful for readers to understand the fundamental concepts responsible for the varied properties of biodegradable polymers introduced in Sections 1.1.1 —1.1.7, regardless of whether they are working in designing new biodegradable polymeric materials or working to develop medical devices. 

A CASE STUDY ON SORPTION PROPERTIES OF BIODEGRADABLE POLYMER MATERIALS... 

The biodegradable packaging industry demands a matching or superiority in physical and chemical properties of biodegradable polymers with their synthetic counterparts. Starch mixed with polyethene is also known as biobased [hydrodegradahle) material. Microbial breakdown is controlled by the polymers that use starch, for example, PLA, PCL, and PVA. They allow breakdown in the presence of microbes, heat, moisture, and proper aeration, as found in traditional compost piles. Additive-based plastic bags are the traditional plastic bag films, whereas special chemical modification is used to make them break down under certain conditions. 

The blending of different polymers is a frequently used technique in industrial polymer production to optimize the material properties. The biodegradable polymer poly(3-hydroxybutyrate) (PHB) [50, 51], for example, which can be produced by bacteria from renewable resources, has the disadvantage of being stiff and brittle. The mechanical properties of PHB, however, can be readily enhanced by blending with another biopolymer, poly(lactic acid) (PLA) [52]. For the preparation of... 

Table 10 Material properties of different biodegradable polymers with respect to applications...

Growing discussion about the limited availability of cheap fossil basic materials, and customers paying more and more attention to product life cycles, brings aspects of the biodegradability of polymer products again to the focus of attention. The replacement of synthetic polymer products with biopolymers is attractive but limited because the properties of natural polymers do not always fit the demands of processability and final product performance. PVA with its beneficial rheological... 

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