Properties of PHAs

These monomers are biodegradeable and used for the production of bioplastics. PHAs produced from the process are usually composed of 100-30,000 monomers and exist in a short chain. Naturally, the properties of PHAs are similar to thermoplastics that are obtained from petrochemical industry such as polypropylene (PP) and polyethylene (PE) as shown in Table 1 (Evan and Sikdar, 1990). 

Poly(hydroxyalkanoates) (PHAs), of which poly(hydroxybutyrate) (PHB) is the most common, can be accumulated by a large number of bacteria as energy and carbon reserve. Due to their bio degradability and bio compatibility these optically active biopolyesters may find industrial applications. A general overview of the physical and material properties of PHAs, alongside with accomplished applications and new developments in this field is presented in this chapter. 

The properties of PHAs are dependent on their monomer composition and therefore it is of great interest that recent research has revealed that, in addition to PHB, a large variety of PHAs can be synthesized microbially. The monomer composition of PHAs depends on the nature of the carbon source and microorganism used. PHB is a typical highly crystalline thermoplastic whereas medium chain length PHAs are elastomers with low melting points and a relatively lower degree of crystallinity. By (chemical) modification of the PHAs, the ultimate properties of the materials can be adjusted even further, when necessary. 

The mechanical properties of PHB and its copolymers have been studied extensively [82, 83]. As shown in Table 3, the material properties of PHAs can be readily controlled by adjusting the polymer composition during the fermentation [84]. 

Physical properties of PHAs are determined by monomer units, which are predominantly responsible for the molecular interactions, the molecular weight, and the molecular weight distribution. In addition, different crystalline modifications and processing conditions have a considerable effect on the achievable property level of the samples. For this reason, only the basic material data are listed and compared the glass transition temperature (7 ), the equilibrium melting temperature of an infinite crystal (T ), the equilibrium heat of fusion (AH ), and the densities of the amorphous (yj and crystalline (yc) parts (Table 1). 

Besides the fabrication of PHA films for oil blotting application, the hydrophobic property of PHA has also led to the use of this material for dye removal via adsorption in textile wastewater treatment. The potential application of PHA films as facial oil adsorbing material suggested that PHA films can also be used to adsorb other hydrophobic compounds. Many textile dyes are hydrophobic and may readily adsorb onto PHA films. Therefore, PHA films maybe used to remove textile dyes from wastewater. Solvent-cast P(3HB) films were found to remove approximately 38 % of color from textile dye wastewater. Electrospun PHA films may show better ability in adsorbing hydrophobic textile dyes. 

Properties of PHAs and their Correlation to Fermentation Conditions... 

Many properties of PHAs can be influenced by the fermentation conditions during the production process. Influences of carbon source and pH on the molecular weight distribution are already known. Not much attention was paid to the homogeneous distribution of the comonomeric units in the polymer so far. 

Aliphatic polyesters are the most representative examples of biodegradable polymeric materials. Poly(3-hydroxyalkanoate)s, PHA, are well known biocompatible and biodegradable polyesters that are produced by various microorganisms as carbon and energy reserves. The physical properties of PHAs vary from crystalline-brittle to soft-sticky materials depending on the length of the side aliphatic chain on p carbon ... 

Improvement of Mechanical Properties of PHA Films by Cold-Drawing... 

The properties of PHAs depend on the stmctme and composition of monomeric constituents. It is known that... 

Advances in PHA technology will enable Meredian to be well positioned to serve the growing demand for materials produced from renewable resources. Leading companies around the world are focused on sustainable initiatives and the utilization of products produced exclusively from renewable starting materials that do not compete with the food supply and that also support multiple end-of-Ufe options. Commercial success will be dependent upon the effectiveness of the current supply chain to efficiently transition to these new materials which will be required to meet ever-increasing demands for increased functionality. The properties of PHA within the portfolio of those described in this chapter have the unique capability to meet this challenge and exceed expectations. 

Biodegradability is one of the most attractive properties of PHAs. Degradation of PHAs occurs extraceUularly as well as intracellularly. 

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