Phase Structure and Biodegradation of the Bacterial Poly(3-hydroxybutyric acid)/Chemosynthetic Poly(3-hydroxypropionic acid) Blend

Abstract

ABSTRACT:Two different aliphatic polyesters, bacterially synthesized polyester poly(3-hydroxybutyric acid) [P(3HB)] and chemically synthesized poly(3-hydoxypropionc acid) [P(3HP)], were blended via solvent casting. By differential scanning calorimetry. polarized optical microscopy. wide-angle X-ray diffractometer and dynamic mechanical thermal analytical instrument, thermal and crystallization behavior and dynamic mechanical relaxation of the as-prepared binary blends were systematically studied. Immiscible properties were ambiguously demonstrated for these blends over the whole range of constituent composition. Glass transition temperature and proton spin diffusion times (Tr and nip) obtained by the high-resolution solid state 13C NMR measurements indicated that the blend system was immiscible not only on an observation scale of DSC (about 10 nm). but on a Tr scale (several tens of nm). Enzymatic biodegradation of the blend samples by extracellular P(3HB)-depolymerase from the bacterium strain A.faecalis TI showed an approximately linear relation between the degradation rate and the component composition. In addition, on the basis of biochemical oxygen demand (BOD). pure P(3HP) could not be biodegraded in the river water, while environmental biodegradability was confirmed when it presents as one constitutive component of the binary P(3HB) /P(3HP) blend.KEY WORDS P(3HB)/P(3HP) Blend / Thermal and Crystallization Behavior/ Morphology ofSpherulite/ Dynamic Mechanical Thermal Analysis/ Proton Spin Diffusion/ Miscible Property/ Enzymatical and Environmental Biodegradation Behavior / Poly(hydroxyalkanoic acid)s (PH As) which accumulate as the intracellular storage compounds by the widely distributed microorganisms in the environments, are now of increasing importance due to more serious problem in plastical waste disposaL 1-4 Because of their bacterial origins, this class of aliphatic polyesters can be environmentally degraded into water and carbon dioxide, exhibiting unique features distinguishable from those of the conventional plastics. A wide range of bacterial biodegradable polyesters and copolyesters have been developed for various technical applications by constructing the desired repeating unit structures. 5 Poly(3-hydroxybutyric acid) [P(3HB)], a representative of PHAs, is a thermoplastics known to be suffered from its high melting point, excessive brittleness and poor impact resistance in applications. 2 -4 Although efforts have been made to bacterially co-polymerize 3HB repeating units with other monomers such as 3-hydroxypropionic acid (3HP),6-8 3-hydroxyvaleric acid (3HV),9 4-hydroxybutyric acid (4HB),2,10-12 and so forth, can improve its deficiencies. However, the considerably high cost of the cultivable substrates and/or precursor-substrates in fermentation impede broader applications of the bacterial polyesters. As an alternative route to provide materials with desirable properties, blending the natural P(3HB) with a secondary constituent is effective without loss of favorable features of biodegradabi...

Study of Miscibility, Crystallization, and Biodegradation of Casting Films of Poly(butylene succinate‐co‐adipate) and Poly(ϵ‐Caprolactone) Blends

“…Once the immiscibility between PBSA and PCL promotes the formation of interphases and, as the biodegradation is a surface erosion process, there is larger area for enzymes diffusion, expanding the area of action of microorganisms. Similar behavior was reported by Cao et al in their study on environmental biodegradation of poly(3‐hydroxybutyric acid) and poly(3‐hydroxypropionic acid) blends.…”

Reversible Thickening/Thinning Phenomena Observed for Polymer Blend Films in Water Media

“…On the other hand, the characteristics of the 60/40 a-PHB/PVPh and 60/40 s-PHB/PVPh blends should be considered as the internal factor of the phenomenon of thickening and thinning. In the past few years, we have studied the nonenzymatic and enzymatic hydrolytic degradation of a variety of polymer and polymer blend films in water media. ,− However, the phenomenon of thickening and the thinning has only been observed for the film of a-PHB/PVPh and s-PHB/PVPh blends. The films of 60/40 a-PHB/PVPh and 60/40 s-PHB/PVPh blends differ from other polymer films in that these blends are free from crystalline phase, with a hydrogen-bonding network and with a T g of (40 °C) close to the experimental temperature (37 °C).…”

MISCIBILITY AND THERMAL DEGRADATION KINETICS OF POLY-β-ALANINE/POLY(3-HYDROXYPROPIONATE) BLENDS

“…Although PHP has attracted much attention as an environmentally degradable polymer to be used for medical applications, it has limitations due to its brittleness (high crystallinity), narrow processability, and high hydrophobicity. Some studies were reported on blends [4][5][6][7] of PHP to eliminate these limitations. Similarly, various [8][9][10][11] copolymers of PHP have been prepared in order to combine its favorable properties with those of other components.…”