Polyhydroxybutyrate blends

Fryczkowskia R. and Kowalczyk T, Nanofibres from polyaniline/ polyhydroxybutyrate blends, Synth. Met, 2009,159,2266-2268. 

Aliphatic polyesters based on monomers other than a-hydroxyalkanoic acids have also been developed and evaluated as drug delivery matrices. These include the polyhydroxybutyrate and polyhydroxy valerate homo- and copolymers developed by Imperial Chemical Industries (ICI) from a fermentation process and the polycaprolactones extensively studied by Pitt and Schindler (14,15). The homopolymers in these series of aliphatic polyesters are hydrophobic and crystalline in structure. Because of these properties, these polyesters normally have long degradation times in vivo of 1-2 years. However, the use of copolymers and in the case of polycaprolactone even polymer blends have led to materials with useful degradation times as a result of changes in the crystallinity and hydrophobicity of these polymers. An even larger family of polymers based upon hydroxyaliphatic acids has recently been prepared by bacteria fermentation processes, and it is anticipated that some of these materials may be evaluated for drug delivery as soon as they become commercially available. 

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. 

In synthetically produced polymers, biodegradability is achieved by reducing the stabilizer content and/or addition of initiators that accelerate biodegradation. Materials in this group include, for example, PHB (polyhydroxybutyrate) and PLA (polylactic acid) [9]. Other polymers use a blend of both types, for example a combination of polyethylene and starch. 

It is known that PLA forms miscible blends with polymers such as PEG [53]. PLA and PEG are miscible with each other when the PLA fraction is below 50 per cent [53]. The PLA/PEG blend consists of two semi-miscible crystalline phases dispersed in an amorphous PLA matrix. PHB/PLA blends are miscible over the whole range of composition. The elastic modulus, stress at yield, and stress at break decrease, whereas the elongation at break increases, with increasing polyhydroxybutyrate (PHB) content [54]. Both PLA/PGA and PLA/PCL blends give immiscible components [55], the latter being susceptible to compatibilization with P(LA-co-CL) copolymers or other coupling agents. 

Polyhydroxy- butyrate Polyhydroxybutyrate and its copolymer with polyhydroxyvalerate were blended with dextran or ainylose and compressed into disc shape. Dextran and ainylose were to enhance the enzyme degradability. Hydrolysis of polyhydroxybutyrate and its copol iTier. Also degradation by amylas< when blended sith amylose. Yasin and Tighe, 1993... 

PCL), polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV), and polyesteramide. Some starch-based blends have been commercialized such as Mater-Bi (Novamont) or Bioplast (Biotec). 

Tg measurements have been performed on many other polymers and copolymers including phenol bark resins [71], PS [72-74], p-nitrobenzene substituted polymethacrylates [75], PC [76], polyimines [77], polyurethanes (PU) [78], Novolac resins [71], polyisoprene, polybutadiene, polychloroprene, nitrile rubber, ethylene-propylene-diene terpolymer and butyl rubber [79], bisphenol-A epoxy diacrylate-trimethylolpropane triacrylate [80], mono and dipolyphosphazenes [81], polyethylene glycol-polylactic acid entrapment polymers [82], polyether nitrile copolymers [83], polyacrylate-polyoxyethylene grafts [84], Novolak type thermosets [71], polyester carbonates [85], polyethylene naphthalene, 2,6, dicarboxylate [86], PET-polyethylene 2,6-naphthalone carboxylate blends [87], a-phenyl substituted aromatic-aliphatic polyamides [88], sodium acrylate-methyl methacrylate multiblock copolymers [89], telechelic sulfonate polyester ionomers [90], aromatic polyamides [91], polyimides [91], 4,4"-bis(4-oxyphenoxy)benzophenone diglycidyl ether - 3,4 epoxycyclohexyl methyl 3,4 epoxy cyclohexane carboxylate blends [92], PET [93], polyhydroxybutyrate [94], polyetherimides [95], macrocyclic aromatic disulfide oligomers [96], acrylics [97], PU urea elastomers [97], glass reinforced epoxy resin composites [98], PVOH [99], polymethyl methacrylate-N-phenyl maleimide, styrene copolymers [100], chiral... 

Parulekar Y, Mohanty AK. Biodegradable toughened polymers from renewable resources blends of polyhydroxybutyrate with epoxidized natural rubber and maleated polybutadiene. Green Chem 2006 8 206. 

Polyhydroxybutyrate, polyhydroxyvalerate, and blends have melting temperatures of 145-175°C [19]. Early results indicate that these microorganism-based plastics are processible in traditional thermoforming equipment. Other biobased plastics include modified polyesters and older plastics, such as polystarches, plastics from gluten- and gliadin-based amino acids, casein, and, of course, cellulosics. Acceptance of biobased plastics depends on their long-term... 

Polyhydroxybutyrate-co-polyhydroxyhexanoates (PHBHs) resins are one of the newest types of naturally produced biodegradable polymers. The PHBH resin is derived from carbon sources such as sucrose, fatty acids or molasses via a fermentation process. These are aliphatic-aliphatic copolyesters, as distinct from aliphatic-aromatic copolyesters. Besides being completely biodegradable, they also exhibit barrier properties similar to those exhibited by ethylene vinyl alcohol. Procter Gamble Co. researched the blending of these polymers to obtain the appropriate stiffness or flexibility. 

Biodegradation experiments of polymer-films in marine and soil environments indicated that, in general and depending on the environment, biodegradation rates for unblended polymers were polyhydroxybutyrate-C(9-valerate > cellophane > chitosan > polycaprolactone. Results from blends are more difficult to interpret since different biodegradation rates of the component polymers and leaching of plasticizers and additives can impact the data [216]. 

Two types of polyhydroxyalkanoate (PHA) biosynthesis gene loci (phb and pha) of Pseudomonas sp. strain 61-3, which produces a blend of poly-3-hydroxybutyrate [PHB] homopolymer and a random copolymer poly(3-hydroxybutyrate-co-3-hydroxyalkanoate) [P(3HB-co-3HA] consisting of 3HA units of 4 to 12 carbon atoms, were cloned and analyzed at the molecular level [274]. In the phb locus, three open reading frames encoding polyhydroxybutyrate (PHB) synthase (PhbCPs), 6-ketothiolase (PhbAPs), and NADPH-dependent acetoacetyl coenzyme A reductase (PhbBPs) were... 

Macromolecular Chemistry Physics 200, No.2, Feb.l999,p.413-21 THERMAL PROPERTIES AND CRYSTALLISATION BEHAVIOUR OF POLYHYDROXYBUTYRIC ACID IN BLENDS WITH CHITIN AND CHITOSAN Ikejima T Yagi K Inoue Y Tokyo,Institute of Technology... 

Films of blends of polyhydroxybutyric acid with chitin and chitosan were prepared as completely biodegradable... 

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