Biopolymer Technologies (Biop, Dresden / Germany; www.biop.eu) claims that using its “Biopar” VT 40 compatibilizer in the production of biopolymers with PHA/PHB (polyhydroxyalkanoate / polyhydroxybutyrate) copolymers can reduce costs by 25%. By using the additive in the production of Biop’s Biopar biopolymer, the starch becomes an important polymer phase rather than simply a filler material. Biop says that this “bi-continuous” phase is typical in all of its Biopar polymers based on potato starch or cassava starch and aliphatic co-polyesters.

When added to a blend of immiscible polymers, the additive modifies their interfaces and stabilises the blend, Biop claims. VT 40 is a block copolymer based on partially hydrolysed PVA. However, it has a different chemical structure than commercially available PVA. Between 2003 and 2009 Biop carried out laboratory and pilot scale production tests with PHA/PHB. The tests showed that VT 40 was able to compatibilize the copolymer with a starch polymer phase and create a bi-continuous phase between both polymers. The use of the technology is also claimed to increase melt strength, provide barrier properties, enhance viscosity and provide better melt flow.