Material PHAs - Polyhydroxyalkanoates
PHAs are linear polyesters produced in nature by bacterial fermentation of sugar or lipids.
More than 100 different monomers can be combined within this family to give materials with extremely different properties.

They can be either thermoplastic or elastomeric materials, with melting-points ranging from 40 to 180C.
The most common type of PHAs is PHB (poly-beta-hydroxybutyrate). PHB has properties similar to those of PP, however it is stiffer and more brittle.

A PHB copolymer called PHBV (polyhydroxybutyrate-valerate) is less stiff and tougher, and it is used as packaging material.
Category Biopolymers
Products Bone plate
Razor, biodegradable (PHA)
Shampoo bottle, biodegradable (PHBV)
Surgical sutures
Processes Blow moulding
Injection moulding
Extrusion
Keywords PHB
PHBV
References Metabolix
Monsanto Company (BiopolTM)
PHB production
Price The price (1997: 15-60 DKK/kg) is very high compared to other oil-derived polymers.
Prices are thus falling down (1993: 100-140 DKK/kg) and, in a couple of years they could reach a level which would enable mass-production (2-6 DKK/kg).
Environmen- tal notes Creation: Made from renewable natural sources like sugar.

Use: It is biocompatible and therefore can be implanted in the body without causing inflammations.
The producer claims that is not toxic.

Disposal: It biodegrades in microbially active environments in 5-6 weeks.
The action of some enzymes produced by microbs solubilises PHB which is then absorbed through the cell wall and metabolised.

PHB is normally broken down to carbon dioxide and water when degraded in aerobic conditions. In absence of oxygen the degradation is faster, and methane is also produced.
PHB is not degraded in biologically inactive systems such as sanitary landfills.
Photo Thomas Nissen (Computer graphics)
Copyright © 1996-2008 Torben Lenau
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