Stress–strain behavior of blends of bacterial polyhydroxybutyrate

Abstract

A series of blends of bacterial poly(R-hydroxybutyrate) (PHB), with different miscible amorphous components, were prepared. The molecular mass of the amorphous components was varied from M n Ϸ 600 to 200,000 g/mol. Several factors were found to influence the stress-strain behavior of PHB blends: the glass-transition temperature, the average molecular mass of amorphous phase, the content of PHB in the blend, the crystallinity, and the drawing temperature. It was found that a high extension ratio at rupture R Ͼ 3 is obtained only if the PHB content is less than 60% (crystallinity X c Ͻ 0.4), although this holds only for blends of bacterial PHB with a high molecular mass (M n Ͼ 30,000) amorphous component. The lowering of glass-transition temperature by the addition of low molecular mass additives (plasticizers) deteriorates the tensile properties. Measurements at elevated temperatures of ductile blends yielded a marked decrease of both stress at rupture R and extension ratio at rupture R .

Studies on recyclability of polyhydroxybutyrate‐co‐valerate bioplastic: Multiple melt processing and performance evaluations

“…The tensile test results showed that PHBV exhibited a typical brittle fracture with less than 10% strain values (around 5%). This happens for polymers that are tested above their glass transition temperature with quasi‐viscous flow behavior 13. The brittleness of these bacterial based polyesters arises from secondary crystallization.…”

“…The brittleness of these bacterial based polyesters arises from secondary crystallization. This secondary crystallization affects the mobility of the amorphous phase creating brittle polymers 13. El‐Taweel et al13 further relates the brittleness of the polyhydroxybutyrate (PHB) with the % crystallinity.…”

PHB-PEO electrospun fiber membranes containing chlorhexidine for drug delivery applications

“…PHB films are known to have fragile behavior with a deformation at break below 5 % and an elastic modulus around 1.5 GPa [29,30]. The brittleness of PHB was attributed to polymer glass transition that occurs ~ 0 ºC, leading to cold recrystallization at room temperature, which restricts the mobility of the amorphous phase in interfibrillar and/or interlamellar regions, and results in a failure at relatively low strains [31].…”

The domain structure and mobility of semi-crystalline poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate): A solid-state NMR study

“…The elucidation of such properties is, therefore, fundamentally important to understand the mode of actions of these polyesters in the living organisms and the functionality in their applications. Extensive researches have been carried out on PHB and some of its copolymers using a variety of techniques including DSC [12,13], X-ray diffraction (XRD) [14,15] and NMR [16e19]. Among many physical techniques, highresolution solid-state NMR is not only non-invasive and nondestructive method to facilitate in situ investigations but also able to provide information on molecular structure, dynamics and interactions of polymers, especially natural polymers [20e22].…”