PHB Blends Research Articles

Poly(3-hydroxybutyrate) nanocomposites modified with even and odd chain length polyhydroxyalkanoates

Poly(3-hydroxybutyrate) (PHB) was blended with medium-chain-length PHAs (mcl-PHAs) for improving its flexibility while nanocellulose (NC) was added as a reinforcing agent. Even and odd-chain-length PHAs, having as main component poly(3-hydroxyoctanoate) (PHO) or poly(3-hydroxynonanoate) (PHN) were synthesized and served as PHB modifiers. The effects of PHO and PHN on the morphology, thermal, mechanical and biodegradation behaviors of PHB were different, especially in the presence of NC. The addition of mcl-PHAs decreased the storage modulus (E') of PHB blends by about 40 %. The further addition of NC mitigated this decrease bringing the E' of PHB/PHO/NC close to that of PHB and having a minor effect on the E' of PHB/PHN/NC. The biodegradability of PHB/PHN/NC was higher than that of PHB/PHO/NC, the latter's being close to that of neat PHB after soil burial for four months. The results showed a complex effect of NC, which enhanced the interaction between PHB and mcl-PHAs and decreased the size of PHO/PHN inclusions (1.9 ± 0.8/2.6 ± 0.9 μm) while increasing the accessibility of water and microorganisms during soil burial. The blown film extrusion test showed the ability of mcl-PHA and NC modified PHB to stretch forming uniform tube and supports the application of these biomaterials in the packaging sector.

Biopolymer Blends of Poly(lactic acid) and Poly(hydroxybutyrate) and Their Functionalization with Glycerol Triacetate and Chitin Nanocrystals for Food Packaging Applications.

Polylactic acid (PLA) is a biopolymer that has potential for use in food packaging applications; however, its low crystallinity and poor gas barrier properties limit its use. This study aimed to increase the understanding of the structure property relation of biopolymer blends and their nanocomposites. The crystallinity of the final materials and their effect on barrier properties was studied. Two strategies were performed: first, different concentrations of poly(hydroxybutyrate) (PHB; 10, 25, and 50 wt %) were compounded with PLA to facilitate the PHB spherulite development, and then, for further increase of the overall crystallinity, glycerol triacetate (GTA) functionalized chitin nanocrystals (ChNCs) were added. The PLA:PHB blend with 25 wt % PHB showed the formation of many very small PHB spherulites with the highest PHB crystallinity among the examined compositions and was selected as the matrix for the ChNC nanocomposites. Then, ChNCs with different concentrations (0.5, 1, and 2 wt %) were added to the 75:25 PLA:PHB blend using the liquid-assisted extrusion process in the presence of GTA. The addition of the ChNCs resulted in an improvement in the crystallization rate and degree of PHB crystallinity as well as mechanical properties. The nanocomposite with the highest crystallinity resulted in greatly decreased oxygen (O) and carbon dioxide (CO2) permeability and increased the overall mechanical properties compared to the blend with GTA. This study shows that the addition ChNCs in PLA:PHB can be a possible way to reach suitable gas barrier properties for food packaging films.

A green and biodegradable plasticizer from copolymers of poly(β‐hydroxybutyrate‐co‐ε‐caprolactone)

AbstractBiodegradable polymers such as poly(3‐hydroxybutyrate) (PHB) and polycaprolactone (PCL) blends are considered as potential replacements for non‐degradable polymers, however, their brittleness is an obstacle for their full realization in biomedicine and food packaging. Here, new biodegradable plasticizers are developed to improve the physicochemical properties of PHB and PCL blends. These plasticizers are synthesized through a one‐step random copolymerization process using different mass ratios (1:1, 2:1, 1:2) of β‐butyrolactone (HB) and ε‐caprolactone (CL) monomers. Plasticizer with larger content of CL segments (1:2) shows a thermal stability higher than other ratios. The addition of plasticizers to PHB/PCL blends enhances the elongation at the break of PHB50/PCL50 blend at least 4 to 6‐fold compared to pure PHB. This process also decreases the melting point and crystallization of PHB/PCL blends which are pivotal for thermal processing, such as extrusion, while no adverse impact on the tensile strength and elastic modulus of blends was observed.

Role of Plasticizers on PHB/bio-TPE Blends Compatibilized by Reactive Extrusion.

Poly(hydroxybutyrate) (PHB) is a biopolymer biologically synthesized by controlled bacterial fermentation from a wide variety of microorganisms. PHB is proposed as a potential green alternative to commonly used plastics in packaging, due to its biodegradability and biocompatibility. However, if PHB is to replace commodities, it has some limitations regarding its thermo-mechanical performance to overcome. Among them are its critically the low toughness values at room temperature and poor thermoforming ability. With the aim of overcoming these weaknesses, in this work, blends of PHB with the addition of a biodegradable thermoplastic elastomer (bio-TPE) were prepared and evaluated. Films of such compounds were made by cast extrusion. In order to enhance the compatibility of both polymers during the extrusion process, three different reactive agents (poly-hexametylene diisocianate, triglycidyl isocyanurate, and Joncryl® ADR-4368) were assessed. The morphology and mechanical- and thermal properties of the films obtained were analyzed. In addition, the thermoforming ability of the produced films was evaluated. The results show that the plasticizers present in the bio-TPE interacted with the reactive agents, making them chemical competitors and altering the outcome of the blends.

Assessment of implantable drug delivery technology: poly (3-hydroxybutyrate) / polypropylene glycol films containing simvastatin

Natural polymers have attracted much attention in recent years for the study of new drug delivery systems. These materials are used as polymer matrices to protect the active drug from degradation in the biological environment and to improve the release kinetics of the drug. The poly(3-hydroxybutyrate) (PHB) is a natural biocompatible polymer, widely used in combination with other polymers to improve their physicochemical properties. Thus, this work aimed to develop and characterize films of PHB and blends containing polypropylene glycol (PPG) with different concentrations of simvastatin (Simv.). The films were prepared by casting, dissolving PHB or a blend of PHB / PPG (90:10) and (5% or 25 %) Simv. in chloroform (2% w/v). The solutions were stirred for 3 h and then transferred to an appropriate glass mold for solvent evaporation for 48 h at room temperature. The obtained films were characterized by Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetric analysis, scanning electron microscopy (SEM), optical microscopy, in vitro degradation study, and in vivo biocompatibility test. The results showed that PHB and blends of PHB / PPG are able to form a homogeneous film with the drug inside. A great amount of drug lead to the instability of polymeric matrixes and resulted in a facilitated film degradation. On the other hand, devices with 5% of Simv. were more stable, which suggests the application of these films for biomedical devices. In vivo studies revealed that the films can interact with the animals' organism, and do not undergo rejection. Hence, these films hold an innovative alternative in tissue engineering to promotes drug release by diffusion and erosion of the polymeric material.

Study on the higher-order structure and hydrogen bonding of biodegradable polymer by low-frequency vibrational spectroscopy

Biodegradable polymer is preferred material to replace the conventional petroleum based polymer materials to protect the nature and conserve oil supplies. Information related to higher-order structure and hydrogen bonding among polymers can be observed in the low-frequency region (3.3-333 cm−1) using terahertz (THz) spectroscopy. THz spectra measurement of temperature-dependent investigation of poly(3-hydroxybutyrate) (PHB) homopolymer and polymer blend of PHB/glycol chitosan with the blend ratios of (80/20) and (60/40) have been performed to investigate the change in higher-order structure and intermolecular hydrogen bonding formed by polymer blends of PHB and glycol chitosan. The THz spectra revealed that the peak at 82 cm−1 does not collapse even in the high temperature indicating the important role of hydrogen bonding interaction between poly(3-hydroxybutyrate) (PHB) and glycol chitosan in maintaining the higher-order structure of the PHB in its blending system.

Blending Poly (3-Hydroxybutyrate) with Polyethylene Glycol (PEG): Thermal behaviour and rheological study

Poly (3-hydroxybutyrate) (PHB) is a biodégradable polymer which its application in industrial was limited due to sensitive to high processing temperature and poor mechanical properties. The thermal and rheological behavior for blends of PHB extracted from dry weight of Jatropha and Poly (ethylene glycol) (PEG) were investigated. Blends of PHB/PEG (PHB 100, PHB 80, PHB 60 and PHB 50) have been prepared through solution blending method. The thermal using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) and rheological behavior using Oscillating Disk Rheometer have been investigated. The results indicate all PHb/PEG blends showed decreased at lowest melting temperature crystallinity (Xc). The TGA result showed that PHB 80 less degraded and suggest better thermal stability compared to PHB 60 and PHB 50. Adding PEG to PHB also improved the rheological behavior of PHB. At higher frequency range, PHB 100 showed less dependency on frequency indicating the elastic structure it has compared to PHB 80, PHB 60 and PHB 50.

Formation of an Organic-Inorganic Biopolymer: Polyhydroxybutyrate-Polyphosphate.

A considerable variety of different biopolymers is formed by the entirety of organisms present on earth. Most of these compounds are organic polymers such as polysaccharides, polyamino acids, polynucleotides, polyisoprenes or polyhydroxyalkanoates (PHAs), but some biopolymers can consist of solely inorganic monomers such as phosphate in polyphosphates (polyPs). In this contribution, we describe the formation of an organic-inorganic block copolymer consisting of poly(3-hydroxybutyrate) (PHB) and polyP. This was achieved by the expression of a fusion of the polyP kinase gene (ppk2c) with the PHB synthase gene (phaC) of Ralstonia eutropha in a polyP-free and PHB-free mutant background of R. eutropha. The fusion protein catalyzed both the formation of polyP by its polyP kinase domain and the formation of PHB by its PHB synthase domain. It was also possible to synthesize the polyP-PHB polymer in vitro with purified Ppk2c-PhaC, if the monomers, adenosine triphosphate (ATP) and 3-hydroxybutyryl-CoA (3HB-CoA), were provided. Most likely, the formed block copolymer (polyP-protein-PHB) turns into a blend of polyP and PHB after release from the enzyme.

Isothermal Crystallization Kinetics of Poly (3-hydroxybutyrate/ Poly(ethylene-co-vinyl acetate) Blends Enhanced by NH4Cl as a Nucleating Agent

The isothermal crystallization kinetics of poly (3-hydroxybutyrate) (PHB)/NH4Cl composites, PHB/poly(ethylene-co-vinyl acetate), with vinyl acetate contents of 80% (EVA80) blends and PHB/EVA80/1 wt% NH4Cl composites were investigated by using differential scanning calorimetry (DSC). The Avrami approach was applied to estimate the kinetic parameters of the PHB samples under isothermal crystallization conditions. It was found that the values of The Avrami rate constant, of PHB were increased with the incorporation of NH4Cl, declining EVA80 content in the PHB blends, and decreasing crystallization temperature. Moreover, the Avrami exponent, n, remained unchanged in spite of the change in the crystallization temperature, EVA80 content, and presence of NH4Cl. The activation energy, calculated using the Arrhenius equation, for PHB/NH4Cl was much lower than that of pure PHB and PHB/EVA80, suggesting that the NH4Cl induced heterogeneous nucleation. The values for PHB/EVA80/1 wt% NH4Cl increased as the EVA80 content was increased, indicating a retardation effect of EVA80. Furthermore, a modified Lauritzen–Hoffmann treatment (LH) was used to evaluate the nucleation constant, of the PHB samples based on the assumption that U* was 13.8 kJ/mol and the equilibrium melting temperatures were 470 K, intercepts of HL equation, were 25.9 for all PHB samples. The values indicated that the crystallization of PHB in its composites and blends, described here, occurred in regime III. The maximum degradation rate temperatures of the PHB/NH4Cl composites were higher than that of PHB, by 9 oC. No significant change in thermal stability was detected by the addition of EVA80.

Accelerated biodegradation of PLA/PHB-blended nonwovens by a microbial community.

In this study, the accelerated biodegradation of PLA/PHB (polylactic acid/polyhydroxybutyrate)-blended nonwovens was investigated in the presence of a microbial community. The PLA/PHB-blended nonwovens were buried in natural soil for 56 days, with soil samples collected for subsequent bacterial community domestication. The tensile strength and elongation at break of the PLA/PHB-blended nonwovens as well as the CO2 generated by the Gen III and natural soil communities were determined to assess the degradation rates of the polymer samples. After incubation for 15 days with the Gen III soil bacterial suspension, the surfaces and fibrous structure of nonwovens and the fibers within the nonwovens exhibited distinct changes. In addition, the amount of EvCO2 reached 566.79 mg, the tensile strength decreased from 10.95 ± 0.7 to 2.57 ± 0.31 MPa, a loss of 77%, and the elongation at break changed from 5.32 ± 0.45 to 7.07 ± 1.04%. The 16S rRNA pyrosequencing results showed that Proteobacteria and Firmicutes were the 2 most important bacterial phyla in the Gen III community, accounting for 80.4 and 19.4% of the total classified sequences, respectively. The results of this study demonstrate that compared to a natural soil microbial community, the domesticated strains in the Gen III community, especially members of the phyla Proteobacteria and Firmicutes, are useful in accelerating the degradation of PLA/PHB-blended nonwovens.

Cold crystallization kinetics of biodegradable polymer blend; controlled by reactive interactable and nano nucleating agent

Poly(lactic acid) (PLA) is famous for its crystalline nature and ability to show exothermic crystallization (cold crystallization) peak during heating cycle of differential scanning calorimetric study. To get an insight into the mechanism of cold crystallization of PLA in its promising forms like biodegradable blend and biodegradable blend nanocomposite, a kinetic study has conducted and reported in the present study. Biodegradable blend of PLA has prepared with poly(hydroxybutyrate) (PHB). Subsequently, blend nanocomposite has prepared using organically modified layered nano silicate. Maleic anhydride has used as a reactive compatibilization agent to modify the interface of the partially miscible blend of PLA and PHB. Kinetics and mechanism of crystallization have monitored through isothermal cold crystallization method on the basis of Avrami relationship. Avrami exponent ‘n’ and equilibrium rate constant ‘K’ value has taken into consideration to quantify the crystallization rate. The half-life of crystallization and equilibrium melting point also has estimated as additional findings to confirm the estimated rate of crystallization. Variation in the energy of activation (Ea) using Arrhenius relation and regime transitions during crystallization process through Lauritzen–Hoffman (L-H) equation also have been reported.

Design of the electrically conductive PHB blends for biomedical applications

Biopolymer blends consisting of insulating crystalline poly(3-hydroxybutyrate) (PHB)/Poly(propylene carbonate) (PPC)/multi-walled carbon nanotubes/plasticizer were prepared by solvent casting, then melted to form films with the hydraulic hot press. The miscibility, crystallization, morphology, thermal properties, and electrical properties were investigated by DSC, TGA, TEM, DC—and AC conductivity. The presence of MWCNT shows the important effect on dielectric and conductivity properties of PHB/PPC blends. The blend films show improved the electrical conductivity from 10−17 Scm−1 of the pure PHB film to 3 × 10−1 Scm−1 by increasing the concentration of MWCNTs for blend 4. The dielectric constant of (e′) of PHB blend has a maximum of between 40 and 200. It has increased ~ 50 orders than pure PHB and pure PPC. The activation energy for DC conduction is about 0.119–0.442 eV, which is typical of electronic conduction in blends 1, 2, and 3, it decreased with increasing the MWCNTs concentration in blend 4 and the conductivity believes like semiconductive behavior. TEM was found that the nanotubes are dispersed uniformly in the PHB matrix and the PHB chains wrap around the nanotube walls.

Recent Advances in 3D Printing of Aliphatic Polyesters.

3D printing represents a valuable alternative to traditional processing methods, clearly demonstrated by the promising results obtained in the manufacture of various products, such as scaffolds for regenerative medicine, artificial tissues and organs, electronics, components for the automotive industry, art objects and so on. This revolutionary technique showed unique capabilities for fabricating complex structures, with precisely controlled physical characteristics, facile tunable mechanical properties, biological functionality and easily customizable architecture. In this paper, we provide an overview of the main 3D-printing technologies currently employed in the case of poly (lactic acid) (PLA) and polyhydroxyalkanoates (PHA), two of the most important classes of thermoplastic aliphatic polyesters. Moreover, a short presentation of the main 3D-printing methods is briefly discussed. Both PLA and PHA, in the form of filaments or powder, proved to be suitable for the fabrication of artificial tissue or scaffolds for bone regeneration. The processability of PLA and PHB blends and composites fabricated through different 3D-printing techniques, their final characteristics and targeted applications in bioengineering are thoroughly reviewed.

The influence of additives on crystallization of blends based on polylactid acid

The sustainable development consists of the effort of replacing commonly used polymer materials for the biodegradable ones. They do not have sufficient physical and mechanical properties, therefore they have to be modified by producing various ratio mixtures or with the additives. Improving their processability and properties is an important challenge to be afforded before using these materials on the market. One way to improve the properties of these materials is to prepare their blends [1]. The most common way of the preparation of packaging materials is the injection moulding, where the crystallization of material is very important. That is the reason the crystallization has become one of the most studied characteristics of biodegradable blends based on PLA / PHB. The work is a contribution to works that deal with the description of the structure of PLA / PHB blends, which have been modified by the addition of various types of additives, mainly nucleating agents and plasticizers [2]. The films of these blends keep approximately unchanged mechanical properties after two weeks of storage. The presence of plasticizer (ATBC) and nucleating agent (BN) has no significant impact on the processing stability of PLA/PHB blends. The results show that the combination of the plasticizer and nucleating agent greatly affects the process of crystallization of PLA/PHB blends as well as the ratio of polymers and the heat treatment process.

Preparation and characterization of PHB/PBAT–based biodegradable antibacterial hydrophobic nanofibrous membranes

In this study, polyhydroxybutyrate/poly(butyleneadipate‐co‐terephthalate) (PHB/PBAT) nanofibrous membranes were produced by electrospinning the blends of biodegradable PHB and PBAT. The antibacterial hydrophobic nanofiber membranes were obtained by grafting 1‐allylhydantoin and perfluorooctyl acrylate onto the PHB/PBAT membranes. The prepared nanofibrous membranes were chlorinated with chlorine bleach and characterized by scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis. The chlorinated nanofibrous membranes exhibited efficient antimicrobial activity againstEscherichia coliO157:H7 (ATCC 43895) andStaphylococcus aureus(ATCC 6538) with 6.08 and 5.78 log reduction, respectively. The contact angle of this antibacterial membrane was 123.1° ± 1.9°. The treated membranes showed good stability and durability towards UV‐A light exposure and storage. Therefore, our designed antibacterial hydrophobic nanofibrous membranes may have great potential for use in food packaging.

Interior Dissection on Domain-Dependent Birefringence Types of Poly(3-hydroxybutyrate) Spherulites in Blends

The mechanisms and correlations between the rotation of Maltese cross axis, optical birefringence types, and lamellar reassembly induced by phase-separation domains, in poly(3-hydroxybutyrate) (PHB)/poly(1,4-butylene adipate) (PBA). In this work, a novel approach via interior dissection into spherulites in correlations with the top-surface morphology of the PHB/PBA (50/50) blend crystallized at a series of Tc’s with various domain sizes. The PHB/PBA blend is used as the model system in comparison to alternative blends of PHB with other polyesters of various extents of phase-separated domains. Domains of optimal sizes were found to be essential in lamellar reassembly, which strongly affects the birefringence types of spherulites. Via the proven approaches, this work expounds how domain sizes and lamellar reorientation in partially miscible blends cause changes in the birefringence types of PHB spherulites, while, in contrast, complete miscibility or extreme phase separation with large domains does not.

Investigations on Green Blends Comprising Biodegradable Polymer and Ionic Liquid.

The green blends of an ionic liquid, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide {[EPrI][TFSI]}, and a biodegradable polymer, poly(3-hydroxybutyrate) (PHB), were investigated in this study. The influence of an ionic liquid on the crystallization behaviors of a biodegradable polymer was explored. In the blends, the presence of [EPrI][TFSI] decreased the Tg and Tm of PHB. Incorporating [EPrI][TFSI] in the blends reduced the degree of crystallinity of PHB, inferring that the [EPrI][TFSI] weakened the crystallization of PHB. It further showed retarded isothermal and non-isothermal crystallization for PHB with the presence of [EPrI][TFSI]. The smaller K and 1/t0.5 estimated by the Avrami equation for the blends indicated that [EPrI][TFSI] weakened the isothermal crystallization of PHB with exhibiting the slower crystallization rate. The present study also discussed non-isothermal crystallization of the blends. We found that the Mo model, which is generally used to discuss the non-isothermal crystallization, adequately described the non-isothermal behaviors of the [EPrI][TFSI]/PHB blends. By increasing the [EPrI][TFSI] content, the rate-related parameter F(T) systematically increased, inferring a decreased crystallization rate of PHB with the addition of [EPrI][TFSI] in the blends. The FTIR results suggested an ion–dipole interaction between [EPrI][TFSI] and PHB. This proposes the occurrence of possible complexation between [EPrI][TFSI] and PHB.

Avaliação das propriedades da blenda de poli(3-hidroxibutirato)/quitosana após esterilização térmica ou radiolítica

Resumo Nesse trabalho foi desenvolvido filme de PHB/quitosana com aplicação promissora em embalagens de alimentos e medicamentos. Esses filmes foram preparados via casting solution e após esterilização térmica ou radiolítica suas propriedades foram avaliadas a partir da microscopia eletrônica de varredura, ensaio de tração, calorimetria exploratória diferencial e análise termogravimétrica. Foram constatadas alterações na morfologia dos filmes de PHB/quitosana após os processos de esterilização. As propriedades mecânicas da blenda se mantiveram aproximadamente constantes após esterilização térmica. Porém, após irradiação as blendas apresentaram-se quebradiças. As propriedades térmicas da blenda foram alteradas apenas para as doses de 50 e 75 kGy, em que foi observado uma redução no valor da entalpia de cristalização, grau de cristalinidade, cristalinidade relativa e taxa de cristalização da blenda. Foi observado que a degradação térmica dos filmes de PHB e das blendas, antes e após os processos de esterilização apresentaram um único estágio (250-300 °C).

Improvement of the Miscibility by Combination of Poly(3-hydroxy butyrate) PHB and Poly(propylene carbonate) PPC with Additives

A series of blends of biodegradable PHB and PPC with and without additives were prepared in different ratios by the casting method. The effect of additives on miscibility, morphology and melting of PHB and PPC blends was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), Fourier transform infrared and wide angle X-ray diffraction (WAXD). The immiscibility between the PHB and PPC blends has been shown using DSC and POM. Acetyl triethyl citrate/polyvinyl acetate (PVAc) as plasticizer and compatibilizer was used to improve the miscibility between the PHB and PPC blends. FT-IR confirmed that the miscibility can be improved by additives, therefore the crystallinity and melting temperature of PHB is depression with increasing PVAc content, the OH group broadened and the ester band C=O shifted in blends 7, 8 and 9, due to hydrogen-bonding interaction. The peak position of C=O of blend 1, 2 and 3 remains constant without any change, i.e. PHB and PPC do not form any intact due to their incompatibility. WAXD showed reduced crystallinity and peak broadening in the patterns of the blends. Electrospun fiber of blend 9 has been manufactured and the morphology was investigated by scanning electron microscopy. Electrospun fibers are homogenous and their diameters were affected by solution concentration. It was found that the elongation at the break of electrospun fibers of PHB/PPC blends increased by adding additives.

Thermal processing influence on mechanical, thermal, and biodegradation behavior in poly(β‐hydroxybutyrate)/poly(ε‐caprolactone) blends: A descriptive model

ABSTRACTPoly(β‐hydroxybutyrate) [PHB] is a biodegradable and biocompatible polymer produced by some bacteria genders. To improve mechanical properties, PHB has been blended with other polymers. Compression‐molded blends of PHB and poly(ε‐caprolactone) [PCL] (70/30 mass ratio) were cooled to room temperature following five different thermal treatments after molding at 180 °C. Blends processed with higher cooling rates were easier to biodegrade, nevertheless elongation at break and tensile strength decreased. Slower cooling kinetics and isothermal treatments increased perfection of crystals, as seen in differential scanning calorimetry and X‐ray diffraction and spherulites size. A descriptive model is proposed herein where thermal, biodegradation, tensile properties, and crystal features were related to cooling kinetics applied. It is proposed that properties of 70/30 (PHB/PCL) blends can be predetermined by an adequate control of thermal conditions during processing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43569.