Polyhydroxyalkanoate physical properties

Polyhydric alcohols, 2 46-55 analysis, 2 52-53 chemical reactions, 2 46-50 economic aspects, 2 52 health and safety factors, 2 53 manufacture, 2 50-52 physical properties of, 2 48t uses of, 2 53-54 Polyhydroxyalkanoates (PHA),... 

TABLE 1. Physical Properties of Selected Polyhydroxyalkanoate Derivatives Containing Amide or Sulfonic Acid Components Prepared According to the Current Invention... 

Polyhydroxyalkanoate synthases can use many different substrates and the number of viable pathways for the biosynthesis of PHAs is huge. When new substrates are used, novel PHAs can be produced. In aiming to reduce production costs, it will be useful to search for bacteria that can synthesize precursor substrates from simple and cheap carbon sources [36,92]. It has also been revealed that, when a PHA synthase enzyme is expressed in a different host microbe, it may result in different substrate speciflcity and therefore new PHAs with new chemical and physical properties are accessible [11]. 

In particular, this chapter will concentrate on the physical properties of the first polyhydroxyalkanoates to be commercially exploited, the Biopol resins, launched by ZENECA Bio Products, Billingham, UK. These materials are copolymers of 3-hydroxybutyric acid (3HB) and 3-hydroxy valeric acid (3H V) ... 

Table 5.3 Physical properties of long sidechain polyhydroxyalkanoates...

Table 111. Comparison of physical properties of selected polyhydroxyalkanoate polymers and petroleum-based plastics.

Polyhydroxyalkanoates and polyhydroxybutyrate in particular may be considered as rather controversial polymers. PHB is sometimes referred to as a material that appeared too early, before its time has came. To summarize, PHAs are prepared from renewable resources and are fully biodegradable. They outperform most of the other biodegradable polymers and many synthetic plastics in properties, notably mechanical strength and modulus, resistance to water and moisture due to high hydrophobicity, high crystallinity and several other physical properties such as barrier behavior or piezoelectricity. 

Satkowski, M. M., Melik, D. H., Autran, J.-R, Green, P. R., Noda, I. Schechtman, L. A. 2005. Physical and processing properties of polyhydroxyalkanoate (PHA) copolymers. Biopolymers Online, Part 3b. Polyesters. 

A wide range of microorganisms have been shown to be able to accumulate polyhydroxyalkanoates. The structure of the sidechain can be modified by careful choice of the microorganism and carbon substrate. Many excellent reviews have already been published on the biosynthesis of these materials [6, 7,8] and Table 5.1 represents a summary of the range of copolymers that have been reported. It is therefore the intention of the current authors not to concentrate on the biochemical aspects of these polymers but instead to deal with the physical and material properties. 

Polyhydroxyalkanoates (PHAs) are homo- or heteropolyesters synthesized and intracellularly stored by numerous prokaryotes. They can be produced in large quantities from renewable resources by means of well known fermentation processes and the imposition of particular culture conditions, and a number of physical or chemical methods are known to extract them from the producing biomass. Production processes such as batch, semi-batch and continuous fermentation are all known to work. PHAs have properties similar to those of some polyolefins. This, combined with the fact that they are fully and rapidly biodegraded under the appropriate conditions, has generated a high interest in them as substitutes to petroleum-based polymers in many applications [1]. 

Satkowski, M.M. et al. Physical and Processing Properties of Polyhydroxyalkanoate Copolymers, in Doi Y. and Steinbuchel A. (Eds), Biopolymers Volume 3b Polyesters II Properties and Chemical Synthesis, New York Wiley-VCH 2001. 

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