Polyhydroxybutyrate mechanical properties

Specifically, 70-30 parts poly(hydroxy-butyrate-co-hydroxyvalerate) (4 mol% valerate) or polyhydroxybutyrate was mixed with 30-70 parts PCL in an internal mixer at 100° or 160°C in the presence of 0-0.5 parts DCP or DBP radical initiator. Blends were characterized by SEM, mechanical properties, selective solvent extraction, and FTIR. 

Gordeyev SA, Nekrasov YPJ (1999) Processing and mechanical properties of oriented poly(beta-hyioxybutyrate) fibers. Mater Sd Lett 18 1691-1692 Hisano T, Kasuya K, Tezuka Y, Ishii N, Kobayashi T, Shiraki M, Oroudjev M, Hansma H, Iwata T, Doi Y, Saito T, Mild K (2006) The crystal structure of polyhydroxybutyrate depolymerase from Penicilliumjuniculosum provides insights into the recognition and degradation of biopolyesters. J Mol Biol 356 993-1004... 

Polyhydroxyalkanoates, Polyhydroxybutyrate, History, Bacterial synthesis. Chemical synthesis. Genetic engineering. Mechanical properties. Thermal transitions. Crystallization, Plasticizers, Thermal degradation. Processing, Applications... 

Polyhydroxybutyrate. Copolymers of hydroxybutyrate and hydroxyvaler-ate possess many mechanical properties in common with synthetic polyolefins, and so have attracted much attention as replacements for these materials in environments where biodegradability is an important parameter (see Poly(3-HYDROXYALKANOATES)). Carswell-Pomerantz and co-workers (217,218) have reported a detailed study of the radicals formed on irradiation of such materials. They found that the yield of radicals at 77 K was G(R) = 1.7 0.2, independent of copolymer composition, but that on irradiation at 300 K, the yield of radicals was reduced for the copol5mers because of their lower glass-transition temperatures compared with the homopolymer. At low temperatures a significant contribution to the ESR spectra from radical anions was noted. These radicals were observed to decay on warming to produce scission radicals. At still higher temperatures, radicals produced by abstraction of a methylene proton adjacent to the carbonyl group were detected. 

Procter Gamble and Kaneka have introduced a range of polyhydroxybutyrate-co-hexa-noate (PHBH),imder the trade mark of Nodax (Figure 10.12) [48]. The properties of Nodax are a function of the concentration of the hexanoate, which vary from hard with some flexibility (4%), hard elastic (6%), soft elastic (8%) to soft rubbery (18%), allowing to manufacture materials (injected moulded, films, or fibres), with similar mechanical properties to polyethylene/polypropylene using standard polymer technology. 

The PHA is produced by bacterial fermentation of sugar or lipids. Polymers in PHA family can be produced by 150 different monomers, due which a large variety of PH As can be synthesized with a wide range of properties. Polyhydroxybutyrate (PHB) is the most common biopolymer in PHA family. PHB is water insolirble and has good resistance to hydrolytic degradation. The and of PHB are approximately 175°C and 15°C respectively (Kumar et al., 2011). PHB exhibits low water permeabihty which is comparable to that of LDPE, and has similar thermal and mechanical properties as isotactic PP (Savenkova et al., 2000). 

Petersen, K., Nielsen, P.V., and Olsen, M.B., 2001, Physical and Mechanical Properties of Biobased Materials Starch, Polylactate and Polyhydroxybutyrate. Starch/Starke 53 356-361. 

Petersen K, Nielsen P V, Olsen M B (2001), Physical and mechanical properties of biobased materials - starch, polylactate and polyhydroxybutyrate . Starch, 53, 356-361. 

Polyhydroxyalkanoates and polyhydroxybutyrate in particular may be considered as rather controversial polymers. PHB is sometimes referred to as a material that appeared too early, before its time has came. To summarize, PHAs are prepared from renewable resources and are fully biodegradable. They outperform most of the other biodegradable polymers and many synthetic plastics in properties, notably mechanical strength and modulus, resistance to water and moisture due to high hydrophobicity, high crystallinity and several other physical properties such as barrier behavior or piezoelectricity. 

Patricio PSO, Pereira FV, Santos MC, Souza PP, Roa JPB, Orefice RL. Increasing the elongation at break of polyhydroxybutyrate biopolymer effect of cellulose nanowhiskers on mechanical and thermal properties. J Appl Polym Sci 2012 127 3613-21. http //dx.doi.org/10.1002/app.37811. 

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