PHA Blends

PHA blends are usually prepared via the solvent-casting and meltcompounding methods. Blends of PHA have attracted considerable attention as the resulting blends potentially have extraordinary properties. Various compounds could be blended with PHA to obtain the desired characteristics for instance, poly(3-hydroxybutyrate)... 

Blending PHA with high or low molecular weight molecules helps improve their material properties. It also helps to reduce production costs (Savenkova et al. 2000). PHA blended with natural fibers were found to have some improvements in their mechanical properties (Avella et al. 2000 Urakami et al. 2000). PHA composites... 

PHA blending with low-cost materials High-value-added applications PHA as bioimplant materials... 

PHA blends with poly(vinyl alcohol) (PVA) are interesting materials whose miscibility depends on the composition and the PVA tacticity [178]. PHB is claimed to be miscible with polyethylene glycol [179] and with poly D-lactide [180] its miscibility with polyethylene oxide depends on the blend composition [181]. Immiscible, but well-compatible blends of PHB, were prepared with poly(butylene succinate-co-butylene adipate) and poly(butylene succinate-co-caprolactone) [182]. 

Bazile, D. (1992) PHA blends with poly(ethylene oxide). EP s 520888, 520889 (to Rhone Poulenc). 

Shikinami, Y, et al. (1993) PHA blend with inorganics./P 052577S0-A (to Takiron). 

The section on the chemical modification of PHAs is divided into different topics such as carhoxylation, hydroxylation, epoxidation, halogenations and graft copolymerization. The section on the physical modification of PHAs is divided into different topics such as PHA blending and coating, PHA irradiation, ion implantation, plasma treatment, electrospinning. To conclude, the authors discuss the modification of PHAs with enzymes. 

Various PHA blends have been developed to improve the performance and to offset the high price of PHAs. The blending of PHAs will offer more scope to expand their range of applications. In this chapter, some features of blends of SCL-PHAs with PLA, stareh, PCL, cellulose and chitosan will be discussed. 

Table 4.1 Thermal and mechanical properties of various PHA blends prepared using the melt compounding method.

One of the remarkable properties of PHAs is the ability to mix well with many other polymeris materials to produce highly compatible composites or so-called polymer alloys. Such blends often possess synergistic properties not obtainable by individual components. Of great interest is the compatible blend of Nodax with certain other classes of degradable polymers, especially those made from renewable resources, such as starch and poly(lactic acid) (PLA). For example, hard and somewhat brittle PLA and much more ductile PHA are excellent complementary materials, which can balance the shortcomings of each other when used together. We report here some newly discovered interesting properties of PLA/PHA blends. 

Figure 9. Toughness ofPlA/PHA blends as a function of blend composition.

PHAs have been blended with many biodegradable and nonbiodegradable polymers to improve their properties and lower material costs. Miscibility, crysMlization behavior, and biodegradability of the blends are the main topics of the published articles on PHA blending. PHB was found to be miscible with poly(ethylene oxide) (PEO), poly(vinyl acetate) (PVAc), poly(p-vinylphenol), poly(vinylidene... 

When PLA-PHA blends (90 wt % PLA) were solvent cast from a chloroform solution, the blends did not show any remarkable toughness improvement. This problem was overcome by melt processing PLA-PHA blends. Melt processed blend films showed remarkable toughness improvement without a reduction in optical clarity. 

PLA/PHA blend after 3 h UV-exposure time in reaction step 2. 

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