PHA is a family of biodegradables thermoplastics polyesters that can be produced by bacterial fermentation.
Main members of this family are the polyhydroxybutyrate (PHB),  and its sub-group in different copolyesters, polyhydroxybutyrate co-hydroxyalkanoates such as polyhydroxybutyrate co-hydroxyvalerates (PHBV).

Their physical properties and biodegradability can be realised by mixing synthetic or natural polymers. PHAs with short lateral chain act as polypropylene. Those with lateral chains have advantageous properties similar to those of elastomers.

Physical properties (exemple PHBV):

• Density : 1,25
• Glass transition temperature : 50°C
• Fusion temperature : 153°C
• Fusion index : 12 g/10 min (190°C / 2,16K) 
• Tensile modulus : 900 MPa
• Tensile elongation : 15 %
• Tensile yield strength : 20 MPa
• Crystallisation rate : 51 %