Polyhydroxybutyrate-co-valerate Research Articles

Non-isothermal crystallization kinetics of biocomposites based on PLA/PHBV and spent coffee grounds

AbstractThis study deals with the modification of a predominantly amorphous poly(lactic acid) (PLA) by blending it with a semi-crystalline biopolymer, polyhydroxybutyrate-co-valerate (PHBV), which has a high crystallinity. The blends with different concentrations of PLA and PHBV were compounded with spent coffee grounds (SCGs) and processed by injection moulding. The structural, thermal and mechanical properties of the produced samples were investigated. Particular attention was paid to the effect of the presence of SCG and the concentration of PHBV in the blend on the crystallization kinetics and the heat deflection temperature (HDT). For equimolar blends, only a slight increase in HDT (about 5 °C) was observed, but the addition of PHBV suppressed the cold crystallization of PLA, which otherwise negatively affects the dimensional stability of injection moulded parts. A similar effect, but to a lesser extent, was achieved by adding SCG to the PLA matrix. Thus, it is clear that the material structures of PLA/PHBV blends and composites help to minimize additional shrinkage of the parts and increase their dimensional stability. Due to the co-continuous structure of the symmetric PLA/PHBV blends and the increase in the degree of crystallinity from 36 to 47% by annealing the produced samples, the heat deflection temperature increased from 65 up to 90 °C.

Crystallization and performance evolution of PHBV nanocomposites through annealing: The role of surface modification of CNCs

To address the brittleness challenge of polyhydroxybutyrate-co-valerate (PHBV) rooting from its slow nucleation rate, cellulose nanocrystals (CNCs) were employed as bio-based nano nucleation and reinforcement agents. CNCs were further functionalized through succinylation using aliphatic dodecyl succinic anhydride (DDSA), for improved compatibility and dispersion within PHBV. Nanocomposites of PHBV incorporating pristine or DDSA-modified CNC (mCNC) were prepared through solution mixing followed by melt injection molding. The study focused on investigating how CNCs and mCNCs affect the crystallization behavior, thermal, rheological, and mechanical properties of PHBV nanocomposites over time, in the course of annealing or conditioning. Thermal results revealed that the incorporation of neat CNCs generally improving stability due to restricted polymer chain mobility and hydrogen bonding, while DDSA-modified CNCs show varied effects depending on the concentration, sometimes diminishing stability due to increased chain mobility. Polarized optical microscopy revealed the superior nucleation efficiency of mCNC, especially at low contents, leading to smaller and numerous spherulites over conditioning. Rheological analysis indicated a dilution effect of the hairy mCNCs, decreasing both dynamic modulus and complex viscosity. Mechanical properties, assessed through tensile testing and dynamic mechanical analysis after 15 days of conditioning, demonstrated the evolving effect of CNCs on aging-induced embrittlement and thermo-mechanical performance of PHBV during storage. The results revealed that incorporating 1 wt% mCNCs effectively toughened PHBV, increasing Young's modulus, and decreasing Tg without scarifying elongation at break compared to neat PHBV. The findings position mCNCs as a promising nucleation agent which retains PHBV nanocomposites toughness after aging.

Phosphorus removal from fermented dairy manure concurrent with polyhydroxybutyrate-co-valerate synthesis under aerobic conditions

Wastewater phosphorus removal achieved biologically is associated with the process known as enhanced biological phosphorus removal (EBPR). In contrast with canonical EBPR operations that employ alternating anaerobic–aerobic conditions and achieve asynchronous carbon and phosphorus storage, research herein focused on phosphorus removal achieved under aerobic conditions synchronously with volatile fatty acid (VFA) storage as polyhydroxybutyrate-co-valerate (PHBV). 90.3 ± 3.4 % soluble phosphorus removal was achieved from dairy manure fermenter liquor; influent and effluent concentrations were 38.6 ± 9.5 and 3.7 ± 0.8 mgP/L, respectively. Concurrently, PHBV yield ranged from 0.17 to 0.64 mgCOD/mgCOD, yielding 147–535 mgCODPHBV/L. No evidence of EBPR mechanisms was observed, nor were canonical phosphorus accumulating organisms present; additionally, the polyphosphate kinase gene was not present in the microbial biomass. Phosphorus removal was primarily associated with biomass growth and secondarily with biomass complexation. Results demonstrate that concurrent PHBV synthesis and phosphorus recovery can be achieved microbially under aerobic dynamic feeding conditions when fed nutrient rich wastewater.

Biodegradable microplastics: Uptake by and effects on the rockpool shrimp Palaemon elegans (Crustacea: Decapoda)

Ingestion of microplastics can lead to deleterious consequences for organisms, as documented by numerous laboratory studies. The current knowledge is based on a multitude of effect studies, conducted with conventional fossil-based and non-degradable plastics. However, there is a lack of information about the acceptance and the effects of novel bio-based and biodegradable plastics. Biodegradable plastics are considered an alternative to conventional plastics and are showing rapidly growing production rates. Biodegradable plastics can disperse into the environment in the same way as conventional plastics do, becoming available to marine organisms. This study aims to provide new insights into the uptake and effects of biodegradable microplastics on marine invertebrates. Rockpool shrimp, Palaemon elegans, were fed with algal flakes coated with polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and conventional low-density polyethylene (LDPE) microparticles. Live observations showed that all of the different types of microplastics were ingested. After dissection of the shrimp, less LDPE particles were found in the stomachs than PLA and PHBV particles. This indicates a longer retention time of biodegradable microplastics compared to conventional microplastics. Presumably, less LDPE particles were ingested or evacuated from the stomach, probably by regurgitation. The ingestion of microparticles of all types of plastics induced enzymatic activity of short-chain carboxylesterases in the midgut glands of the shrimp. However, only PLA induced enzymatic activity of medium-chain carboxylesterases. Palaemon elegans showed no oxidative stress response after ingestion of microparticles, irrespective of polymer type. From our results we conclude that biodegradable plastics might have different effects than conventional plastics. The longer retention times of biodegradable plastics might enhance exposure to leaching additives and other harmful substances. Our study provides new insights into how biodegradable plastics might affect aquatic fauna and indicate that the use of biodegradable plastics needs to be reconsidered to some extent.

Valorization of Agricultural Waste Lignocellulosic Fibers for Poly(3-Hydroxybutyrate-Co-Valerate)-Based Composites in Short Shelf-Life Applications.

Biocircularity could play a key role in the circular economy, particularly in applications where organic recycling (composting) has the potential to become a preferred waste management option, such as food packaging. The development of fully biobased and biodegradable composites could help reduce plastic waste and valorize agro-based residues. In this study, extruded films made of composites of polyhydroxybutyrate-co-valerate (PHBV) and lignocellulosic fibers, namely almond shell (AS) and Oryzite® (OR), a polymer hybrid composite precursor, have been investigated. Scanning electron microscopy (SEM) analysis revealed a weak fiber-matrix interfacial interaction, although OR composites present a better distribution of the fiber and a virtually lower presence of "pull-out". Thermogravimetric analysis showed that the presence of fibers reduced the onset and maximum degradation temperatures of PHBV, with a greater reduction observed with higher fiber content. The addition of fibers also affected the melting behavior and crystallinity of PHBV, particularly with OR addition, showing a decrease in crystallinity, melting, and crystallization temperatures as fiber content increased. The mechanical behavior of composites varied with fiber type and concentration. While the incorporation of AS results in a reduction in all mechanical parameters, the addition of OR leads to a slight improvement in elongation at break. The addition of fibers improved the thermoformability of PHBV. In the case of AS, the improvement in the processing window was achieved at lower fiber contents, while in the case of OR, the improvement was observed at a fiber content of 20%. Biodisintegration tests showed that the presence of fibers promoted the degradation of the composites, with higher fiber concentrations leading to faster degradation. Indeed, the time of complete biodisintegration was reduced by approximately 30% in the composites with 20% and 30% AS.

Gastric carboxylesterases of the edible crab Cancer pagurus (Crustacea, Decapoda) can hydrolyze biodegradable plastics

A promising strategy to counteract the progressing plastic pollution of the environment can involve the replacement of persistent plastics with biodegradable materials. Biodegradable polymers are enzymatically degradable by various hydrolytic enzymes. However, these materials can reach the environment in the same way as conventional plastics. Therefore, they are accessible to terrestrial, freshwater, and marine biota. Once ingested by marine organisms, highly active enzymes in their digestive tracts may break down biodegradable compounds. We incubated microparticles of five different biodegradable plastics, based on polylactictic acid (PLA), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT) and polyhydroxybutyrate-co-valerate (PHBV), in-vitro with the gastric fluid of the edible crab Cancer pagurus and evaluated the hydrolysis rates by pH Stat titration. A plastic blend of PLA with PBAT showed the highest hydrolysis rate. The enzymes in the gastric fluid of crabs were separated by anion exchange chromatography. Fractions with carboxylesterase activity were identified using fluorescent methylumbelliferyl (MUF)-derivatives. Pooled fractions with high carboxylesterase activity also hydrolyzed a PLA/PBAT plastic blend. Carboxylesterases showed molecular masses of 40–45 kDa as determined by native gel electrophoresis (SDS-PAGE). Our study demonstrated that digestive carboxylesterases in the gastric fluid of C. pagurus exhibit a high potential for hydrolyzing certain biodegradable plastics. Since esterases are common in the digestive tract of organisms, it seems likely that other invertebrates possess the ability to hydrolyze biodegradable plastics.

Dielectric and rheological performances of cellulose acetate, polylactic acid and polyhydroxybutyrate-co-valerate biobased blends

This study presents a new approach to formulating cellulose acetate (CA), polylactic acid (PLA), and polyhydroxybutyrate-co-valerate (PHBV) biobased blends, with a focus on their dielectric and rheological performances for an electrical insulation application. FTIR and rheological analysis showed a molecular interaction in PHBV:CA and PLA:CA blends between the carbonyl groups of PLA and PHBV, and the hydroxyl groups of CA. Dielectric study showed that temperature, frequency, and polymer nature are key parameters influencing the blends' dielectric constant (ε′) and loss factor (ε'') for room and high temperatures. Even though CA-based blends possessed the highest dielectric constants at room temperature, they showed the lowest thermal-sensitive behavior. The measured dielectric properties showed potential applications of PLA-based blends for low-temperature electrical insulation and CA-based blends for high-temperature electrical insulation.

Aerobic aquatic biodegradation of bio-based and biodegradable polymers: Kinetic modeling and key factors for biodegradability

With the increasing concern about plastic waste, numerous efforts have been made to find substitutes for existing non-biodegradable synthetic polymers. Bio-based and/or purported petroleum-based biodegradable polymers are considered probable plastic replacement candidates. However, the durability of non-biodegradable plastic is a key feature of plastics. Thus, a balance must be achieved between biodegradation and environmental material stability. The objective of this study is to determine the impact of crystallinity, molecular chemistry, and hydrophilicity on the rate of aquatic biodegradation of biobased plastic materials. In the present study, twelve bio-based/purported biodegradable materials were investigated under aerobic aquatic biodegradation conditions for 56 days by tracking oxygen consumption. Crystallinity, hydrophobicity, chemistry, and chemical structure were varied to understand potential means for controlling the rate of biodegradation. The biodegradation kinetics were analyzed and discussed, relating to the characteristics of polymers. Polyvinyl alcohol (PVA), Chitosan, Rayon, Polyhydroxy-butyrate-co-valerate (PHBV), PHBH, and Polybutylene succinate (PBS) showed the biodegradation extents over 70% at 56 days. Cellulose acetates (CAs) and Polylactic acid (PLA) showed biodegradation extent lower than 20%. The chemistry of the polymer backbone chain, substituent structure, and degree of substitution were the dominant factors affecting biodegradation. The crystallinity of the polyesters had a negative correlation with the initial biodegradation rate and the ultimate biodegradation of polyesters, and the hydrophobicity of the polymers delayed the initiation of biodegradation. The aerobic aquatic biodegradation results related to the polymer characteristics are useful for product designers and environmental scientists to understand the fate of these polymeric materials in the environment.

Mechanical recyclability of biodegradable polymers used for food packaging: case study of polyhydroxybutyrate-co-valerate (PHBV) plastic

For the purpose of mechanical recycling for food contact applications, decontamination of polyhydroxybutyrate-co-valerate (PHBV) plastic was performed under different temperatures and time conditions. As expected, increasing the decontamination temperature and duration increased the decontamination efficiency, but also the degradation of the polymer. The combination 160 °C/6 h was selected as the optimal conditions that maximize contaminants removal while minimizing polymer degradation. Then the safety of the recycled PHBV under these conditions was assessed, in accordance with EFSA regulation based on bottle-to-bottle PET recycling. Decontamination of low molecular weight molecules such as toluene, chlorobenzene, and methyl salicylate was nearly complete with residual concentrations below the modeled concentrations allowed in the polymer when the adult scenario is considered. However, the higher molecular weight and lower volatility molecules exhibited acceptable decontamination efficiencies, but their residual concentrations in the polymer exceeded the maximum concentrations of no concern. The presence of these molecules allows the use of nearly 21% recycled PHBV in the new materials to meet safety criteria. It is important to keep in mind that this work, never done before, is a preliminary work on mechanical recycling of PHBV, mainly based on extrapolation of PET conditions and regulations. Much more research needs to be done to improve the decontamination process, the barrier properties of PHBV or to think about a short recycling line for PHBV.

In Service Performance of Toughened PHBV/TPU Blends Obtained by Reactive Extrusion for Injected Parts.

Moving toward a more sustainable production model based on a circular economy, biopolymers are considered as one of the most promising alternatives to reduce the dependence on oil-based plastics. Polyhydroxybutyrate-co-valerate (PHBV), a bacterial biopolyester from the polyhydroxialkanoates (PHAs) family, seems to be an attractive candidate to replace commodities in many applications such as rigid packaging, among others, due to its excellent overall physicochemical and mechanical properties. However, it presents a relatively poor thermal stability, low toughness and ductility, thus limiting its applicability with respect to other polymers such as polypropylene (PP). To improve the performance of PHBV, reactive blending with an elastomer seems to be a proper cost-effective strategy that would lead to increased ductility and toughness by rubber toughening mechanisms. Hence, the objective of this work was the development and characterization of toughness-improved blends of PHBV with thermoplastic polyurethane (TPU) using hexamethylene diisocyanate (HMDI) as a reactive extrusion agent. To better understand the role of the elastomer and the compatibilizer, the morphological, rheological, thermal, and mechanical behavior of the blends were investigated. To explore the in-service performance of the blends, mechanical and long-term creep characterization were conducted at three different temperatures (−20, 23, 50 °C). Furthermore, the biodegradability in composting conditions has also been tested. The results showed that HMDI proved its efficiency as a compatibilizer in this system, reducing the average particle size of the TPU disperse phase and enhancing the adhesion between the PHBV matrix and TPU elastomer. Although the sole incorporation of the TPU leads to slight improvements in toughness, the compatibilizer plays a key role in improving the overall performance of the blends, leading to a clear improvement in toughness and long-term behavior.

Review on the Biological Degradation of Polymers in Various Environments.

Biodegradable plastics can make an important contribution to the struggle against increasing environmental pollution through plastics. However, biodegradability is a material property that is influenced by many factors. This review provides an overview of the main environmental conditions in which biodegradation takes place and then presents the degradability of numerous polymers. Polylactide (PLA), which is already available on an industrial scale, and the polyhydroxyalkanoates polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV), which are among the few plastics that have been proven to degrade in seawater, will be discussed in detail, followed by a summary of the degradability of further petroleum-, cellulose-, starch-, protein- and CO2-based biopolymers and some naturally occurring polymers.

Mechanical Testing of Poly Hydroxy Butyrate Co Valerate and Natural Fiber by Varying Fiber Length

The knowledge of 3D printing material used in 3D printing technique is so abundant. Even though there are many critical issues in practical applications. This paper reports the mechanical properties of Environmental friendly Bio composites. This composite material is intended to be used as a replacement for the current 3D printing material. The composite was prepared in compression molding technique under 150 kg/cm2 pressure. The composite consists of Poly Hydroxy Butyrate co Valerate (PHBV) and Sansevieria Roxburghiana. The tensile strength of the given specimen is found to be increased by the change in the volume fraction of fibers. Initially composite plates composed of both PHBV and Sansevieria Roxburghiana are prepared with different weight percentage of PHBV and different lengths of fiber such as 20mm, 30mm, 40mm and 50mm.

Mechanical Behaviour of PLA and PHBV Based Lignocellulosic Composite Plates

The knowledge of 3D printing material used in 3D printing technique is so abundant. Even though there are many critical issues in practical applications. This paper reports the comparison study of the Tensile, Flexural and Impact properties of Environmental friendly composites. This composite material is intended to be used as a replacement for the current 3D printing material. The composite was prepared in compression molding/Injection molding technique under 150 kg/cm2 pressure. This work consists of three specimens. One specimen is Poly Hydroxy Butyrate co Valerate (PHBV) and Sansevieria Roxburghiana. Second specimen is Poly Lactic Acid (PLA) and Sansevieria Roxburghiana and the last specimen is Pure PLA plate. The tensile, impact, flexural strength of pure PLA is comparatively better than the other two composite mixture plates. When comparing the fiber mixture of PLA and PHBV plates the PLA mixture possess greater mechanical properties. The research is further extended by changing the proportion of fiber and also improving the fiber lengths.

Soil Biodegradation of Unidirectional Polyhydroxybutyrate-Co-Valerate (PHBV) Biocomposites Toughened With Polybutylene-Adipate-Co-Terephthalate (PBAT) and Epoxidized Natural Rubber (ENR)

The detrimental impact of discarded plastics on the environment has become of increasing concern and this has led to the development of environmentally friendly ‘green’ polymers. PHBV is one such green polymer that offers biodegradability and renewability, however its mechanical performance is quite limited. This can be improved by reinforcement with natural fibres to form green composites, which offer better mechanical properties while retaining biodegradability. There are, however, few studies examining the biodegradation of toughened PHBV composites. In this work, the biodegradation properties of PHBV/30 vol.% unidirectional flax composites both untoughened and toughened with PBAT and ENR, were studied. Composites were prepared by compression moulding PHBV powder interleaved with unidirectional flax fabric. The toughening agents were cryoground and mixed with the PHBV powder prior to moulding. Biodegradation was conducted in a natural outdoor soil environment and biodegradability was evaluated through weight loss analysis, optical microscopy and electron microscopy. The biodegradability of neat PHBV was minimal but was increased markedly by addition of flax fibres. The toughened composites showed a faster degradation rate than untoughened PHBV/flax, with PHBV/ENR/flax composites having the highest rate likely due to a specific strain of bacteria found worldwide in soil that attacks natural rubber. The biodegradation properties of the composites were superior to those of conventional plastics used in applications such as computer and mobile phone casings, which indicates potential suitability of this class of materials for these applications.

Thermal-chemical and biodegradation behaviour of alginic acid treated flax fibres/ poly(hydroxybutyrate-co-valerate) PHBV green composites in compost medium

Abstract In this study, thermal-chemical and biodegradation behaviour of green composites based on flax fibres untreated and treated with alginic acid treated, and poly hydroxybutyrate-co-valerate (PHBV) were studied under composting conditions. The biodegradability of PHBV composites and neat PHBV were assayed by monitoring CO2 production from polymeric carbon under controlled aerobic composting conditions as per ASTM D5338 standard. During the biodegradation process, PHBV composites thermal-chemical and morphology properties were characterized by thermogravimetric analysis (TGA), fourier transform infra-red (FT-IR) and scanning electron microscopy (SEM) techniques. The ultimate biodegradation (mineralization) study results showed alginic acid treated flax/PHBV composites has higher rate of degradation than untreated flax/PHBV composite and neat PHBV. TGA analysis indicated that an increased t-onset temperature for alginic acid treated flax fibres/PHBV composites which was mainly due to the influence of 2% sodium alginate treated with flax fibres. FTIR results showed the increased degradation of PHBV composites was due to the hydrolytic chain scission mechanisms influenced by presence of alginic acid and flax fibres as compared to neat PHBV matrix. Morphological SEM analysis showed PHBV composites biodegradation were readily attacked by fungus but rather PHBV degradation by bacteria. This study found that the incorporation of flax fibres into PHBV matrix provides a benefit to the green composites with enhanced biodegradability.

Mechanical and Hydrothermal Aging Behaviour of Polyhydroxybutyrate-Co-Valerate (PHBV) Composites Reinforced by Natural Fibres.

Biodegradable composites based on poly (3-hydroxybutyrate-co-3-hydroxyvalerate), reinforced with 7.5% or 15% by weight of wood fibers (WF) or basalt fibers (BF) were fabricated by injection molding. BF reinforced composites showed improvement in all properties, whereas WF composites showed an increase in Young’s modulus values, but a drop in strength and impact properties. When compared with the unmodified polymer, composites with 15% by weight of BF showed an increase of 74% in Young’s modulus and 41% in impact strength. Furthermore, the experimentally measured values of Young’s modulus were compared with values obtained in various theoretical micromechanical models. The Haplin-Kardas model was found to be in near approximation to the experimental data. The morphological aspect of the biocomposites was studied using scanning electron microscopy to obtain the distribution and interfacial adhesion of the fibers. Additionally, biodegradation tests of the biocomposites were performed in saline solution at 40 °C by studying the weight loss and mechanical properties. It was observed that the presence of fibers affects the rate of water absorption and the highest rate was seen for composites with 15% by weight of WF. This is dependent on the nature of the fiber. After both the first and second weeks mechanical properties decreased slightly about 10%.

Preparation and characterization of polyhydroxybutyrate-co-valerate (PHBV) as green composites using nano reinforcements

This article presents the preparation and characterization of polyhydroxybutyrate-co-valerate (PHBV) nanocomposite films containing cellulose nanocrystals (CNC) and aluminum oxide nanoparticles (Al2O3) as reinforcements. The effects of adding nanoparticles on the mechanical properties, such as tensile strength and elongation, were studied using dynamic-mechanical analysis (DMA) such as modulus and tan δ. Also, morphology and thermal features were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. For this purpose, first, CNC and Al2O3 with a ratio of 0, 1, 3 and 5 wt% was added to a biopolymer, then a combination of these two with the ratio of 3:3 and 5:5 was added to the PHBV matrix, separately; and finally, the various nanocomposite films were prepared by the solvent casting method. After adding nanoparticles, the tensile strength and thermal stability of the PHBV/CNC films increased and the elongation decreased. SEM observations showed that large amounts of nanoparticles (3 wt%) are strongly agglomerated in the biopolymer matrix. This led to a decrease of mechanical properties in the composites with nanoparticles of more than 3% by weight. DSC results showed that the glass transition temperature (Tg) increased slightly with the incorporation of nano participles to PHBV. The enthalpy of fusion (ΔHfus) increased from 33.8 J/g for neat PHBV film to 48.1, 50 and 45.8 J/g for PHBV films containing 1, 3, and 5 wt% CNC, respectively. These results are consistent with the conclusions of DMA. The improvement of physical and mechanical properties of the composites confirmed that CNC has a better effect than aluminum oxide nanoparticles as a nano reinforcement.

How olive pomace can be valorized as fillers to tune the biodegradation of PHBV based composites

Polyhydroxybutyrate-co-valerate (PHBV) is a very promising bio-sourced and biodegradable bacterial polyester, the commercial development of which being limited by its high cost. On the other hand, olive oil extraction generates a large amount of lignocellulosic solid residue, called olive pomace (OP), whose disposal raises environmental concerns, including the inhibition of soil microbial populations and the reduction of seed germination. To address these issues, PHBV/OP based biocomposites were produced (at a filler content of 15 wt%) using three different fillers obtained by dry fractionation of OP, i.e. a stone-rich fraction (SF), a pulp-rich fraction (PF) and a crude pomace (F0). The objective of the present work was to investigate how the composition of OP-based fillers influenced the biodegradability of resulting biocomposites. The biodegradation of PHBV, OP-based fillers and OP/PHBV-based biocomposites was assessed by respirometric tests conducted in a standardized soil environment over 4 months. Results showed that the incorporation of OP-based fillers in PHBV favored the overall biodegradability of the materials. Indeed, 100% of biodegradation was achieved after 75, 79 and 87 days for PHBV-F0, PHBV-SF and PHBV-PF formulations respectively, while a biodegradation rate of only 91% was obtained after 123 days in the case of neat PHBV. These results were discussed in the light of several parameters such as the material structure, the affinity of the fillers for the matrix, the composition and the degree of crystallinity of the filler, together with the antibacterial activity of the OP samples assessed by a direct contact technique on solid medium.

The Positive Fate of Biochar Addition to Soil in the Degradation of PHBV-Silver Nanoparticle Composites.

The environmental contamination of soils by polymeric and nanomaterials is an increasing global concern. Polymeric composites containing silver nanoparticles (AgNP) are collectively one of the most important products of nanotechnology due to their remarkable antimicrobial activity. Biochars are a promising resource for environmental technologies for remediation of soils considering their high inorganic and organic pollutant adsorption capacity and microbial soil consortium stimulation. In this work we report, for the first time, the use of biochar material as a tool to accelerate the degradation of polyhydroxybutyrate- co-valerate (PHBV) and PHBV composites containing AgNP in a tropical soil system, under laboratory conditions. This positive effect is associated with microbial community improvement, which increased the degradation rate of the polymeric materials, as confirmed by integrated techniques for advanced materials characterization. The addition of 5-10% of sugarcane bagasse biochar into soil has increased the degradation of these polymeric materials 2 to 3 times after 30 days of soil incubation. However, the presence of silver nanoparticles in the PHBV significantly reduced the degradability potential of this nanocomposite by the soil microbial community. These results provide evidence that AgNP or Ag+ ions caused a decline in the total number of bacteria and fungi, which diminished the polymer degradation rate in soil. Finally, this work highlights the great potential of biochar resources for application in soil remediation technologies, such as polymeric (nano)material biodegradation.

Preparation and characterization of antimicrobial, biodegradable, triclosan‐incorporated polyhydroxybutyrate‐co‐valerate films for packaging applications

ABSTRACTThe prospective application of polyhydroxybutyrate‐co‐valerate (PHB‐VA) as a biodegradable polymer for packaging through the incorporation of triclosan (TCS) was studied via thermal, mechanical, and antimicrobial studies. The solvent‐casting technique was used for the preparation of PHB‐VA–TCS blend films. The blend films were characterized by differential scanning calorimetry, thermogravimetry, Fourier transform infrared spectroscopy, and mechanical properties measurements. The addition of TCS to PHB‐VA resulted in increased film stretchability along with improved flexibility. The crystallization and melting temperatures of PHB‐VA decreased with increasing concentration of TCS. Scanning electron microscopy images showed a homogeneous dispersion of TCS in PHB‐VA. The bactericidal activities of the PHB‐VA–TCS blend films were investigated against Escherichia coli and Staphylococcus aureus by the disc‐diffusion method. The blend films exhibited higher antibacterial activities with increasing concentration of TCS. We concluded from the study that TCS could be successfully incorporated into PHB‐VA to obtain flexible antimicrobial films for packaging applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46862.