Understanding the effect of copolymer content on the processability and mechanical properties of polyhydroxyalkanoate (PHA)/wood composites

Chan, Clement Matthew; Vandi, Luigi‐Jules; Pratt, Steven; Halley, Peter J.; Ma, Yiming; Chen, Guoqiang; Richardson, Desmond; Werker, Alan; Laycock, Bronwyn

doi:10.1016/j.compositesa.2019.05.005

Cited by 34 publications

(27 citation statements)

References 44 publications

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“…DCD, 99%, was purchased from Sigma Aldrich, Australia. The PHBV with ~1 mol% hydroxyvalerate (HV) content (as determined by 1 H‐NMR analysis), 68% crystallinity 26 and a weight‐average molecular weight of 590 kDa was supplied by TianAn Biopolymer, China under the trade name of ENMAT Y1000.…”

Section: Methodsmentioning

confidence: 99%

Designing for effective controlled release in agricultural products: new insights into the complex nature of the polymer–active agent relationship and implications for use

et al. 2020

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BACKGROUND Various active chemical agents, such as soil microbial inhibitors, are commonly applied to agricultural landscapes to optimize plant yields or minimize unwanted chemical transformations. Dicyandiamide (DCD) is a common nitrification inhibitor. However, it rapidly decomposes under warm and wet conditions, losing effectiveness in the process. Blending DCD with an encapsulating polymer matrix could help overcome this challenge and slow its release. Here, we encapsulated DCD in a biodegradable matrix of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and investigated the effects of DCD crystal size and loading rates on release rates. RESULTS Three DCD crystal size fractions (0–106, 106–250 and 250–420 μm) were blended with PHBV at 200, 400, 600 and 800 gkg−1 loadings through extrusion processing and release kinetics were studied in water over 8 weeks. For loadings ≥ 600 g kg−1, more than 95% release was reached within the first 7 days. By contrast, at 200 g kg−1 loading only 10%, 36% and 57% of the DCD was mobilized after 8 weeks in water for 0 to 106 μm, 106 to 250 μm and 250 to 420 μm crystal size fractions, respectively. CONCLUSION The lower percolation threshold for this combination of materials lies between 200 and 400 g kg−1 DCD loading. The grind size fraction of DCD significantly affects the quantity of burst release from the surface of the pellet, particularly below the lower percolation threshold. The results presented here are likely translatable to the encapsulation and release of other crystalline materials from hydrophobic polymer matrices used in controlled release formulations, such as fertilizers, herbicides and pesticides. © 2020 Society of Chemical Industry

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Section: Methodsmentioning

confidence: 99%

Designing for effective controlled release in agricultural products: new insights into the complex nature of the polymer–active agent relationship and implications for use

et al. 2020

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“…The T m of the PHBV here synthesized by Hfx. mediterranei was markedly lower than the commercial sample, this latter previously characterized by the 1–3 mol% HV [ 84 , 85 ]. According to the literature [ 86 ], melting point of the experimental PHBV corresponds to an approximately HV content of 16 mol%.…”

Section: Discussionmentioning

confidence: 97%

“…Overall, the XPS results corroborated the DSC and ATR-IFTR conclusions regarding the abundance of the alkyl region, corresponding to the HV chains. The analysis of the mechanical properties revealed a lower tensile strength than the commercial sample, this latter characterized by a low percentage of HV (1–3 mol%) [ 84 , 85 ]. It was previously reported that increasing HV percentages in the PHBV co-polymer cause the decrease of the tensile strength.…”

Section: Discussionmentioning

confidence: 99%

“…It was previously reported that increasing HV percentages in the PHBV co-polymer cause the decrease of the tensile strength. Nevertheless, a relevant increase of the elongation break was observed in correspondence of high HV incorporation [ 85 ]. Indeed, a, three-fold higher elongation break value was observed for the experimental PHBV sample compared to ENMAT commercial preparation.…”

Section: Discussionmentioning

confidence: 99%

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Production of the Polyhydroxyalkanoate PHBV from Ricotta Cheese Exhausted Whey by Haloferax mediterranei Fermentation

Raho¹,

Carofiglio²,

Montemurro

et al. 2020

Foods

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In the last decade, the dairy industry underwent a rapid expansion due to the increasing demand of milk-based products, resulting in high quantity of wastewater, i.e., whey and ricotta cheese exhausted whey (RCEW). Although containing high content of nutritional compounds, dairy by-products are still disposed as waste rather being reintroduced in a new production chain, hence leading to environmental and economic issues. This study proposes a new biotechnological approach based on the combination of membrane filtration and fermentation to produce poly-hydroxyalkanoates (PHA), biodegradable bioplastics candidate as an alternative to petroleum-derived plastics. The protocol, exploiting the metabolic capability Haloferax mediterranei to synthesize PHA from RCEW carbon sources, was set up under laboratory and pilot scale conditions. A multi-step fractionation was used to recover a RCEW fraction containing 12.6% (w/v) of lactose, then subjected to an enzymatic treatment aimed at releasing glucose and galactose. Fermentation conditions (culture medium for the microorganism propagation, inoculum size, time, and temperature of incubation) were selected according to the maximization of polymer synthesis, under in-flasks experiments. The PHA production was then tested using a bioreactor system, under stable and monitored pH, temperature, and stirring conditions. The amount of the polymer recovered corresponded to 1.18 g/L. The differential scanning calorimetry (DSC) analysis revealed the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the polymer synthesized, with a relatively high presence of hydroxyvalerate (HV). Identity and purity of the polymer were confirmed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) spectroscopy analyses. By combining the fractionation of RCEW, one of the most abundant by-products from the agri-food industry, and the use of the halophile Hfx mediterranei, the production of PHBV with high purity and low crystallinity has successfully been optimized. The process, tested up to pilot scale conditions, may be further implemented (e.g., through fed-batch systems) and used for large-scale production of bioplastics, reducing the economical and environmental issues related the RCEW disposal.

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“…degrades at temperature of 180-190℃ [54] . PCL melts at 57℃ [55] , and its degradation first appears at 415℃ [56] .…”

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confidence: 99%

Tailoring the release of DCD from biopolymer matrices: The effect of DCD crystal size, loading, blends of PHBV and PCL and temperature on DCD release kinetic

Liao¹

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To increase the efficiency of nitrogen fertilizers, stabilized fertilizers have been developed by the fertilizer industry. These stabilized fertilizers can slow down the nitrification of ammonium using nitrification inhibitors (NI). Dicyandiamide (DCD) is a commonly used NI used in agriculture today, but its lifetime in soil exponentially declines with increasing temperature. Controlled-release of DCD can protect the molecule from bacterial degradation and prolong the duration of inhibition. This can be achieved by encapsulating it in a biodegradable polymer matrix. Biopolymer matrices include poly(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) and polycaprolactone (PCL). In this research, DCD-PHBV pellets with DCD crystal sizes of 0-106 μm, 106-250 μm, >250 μm at DCD loadings of 20% (w/w), 40%, and 60% were produced by extrusion processing. In addition, an 80% loading with 0-106 μm DCD was fabricated. Further, 0-106 μm DCD was extruded at 40% loading with PHBV, PCL and 3:1, 1:1 and 1:3 PHBV/PCL blends. The release kinetics of DCD from these materials was monitored in water over eight weeks. Firstly, the effect of loading and DCD crystal size was investigated at 23℃. Following this, the effect of blends of PHBV and PCL were studied at 10℃, 23℃ and 40℃. The pellets were characterized using micro-computed tomography (µ-CT), Raman spectroscopy mapping and differential scanning calorimetry (DSC). The water release experiments confirm that the release profiles of DCD can be tailored by controlling the DCD loading, DCD crystal grind size, and the compositions of PHBV/PCL blends for specific applications and climatic conditions. Increasing loading increased the amount and rate of DCD release of DCD-PHBV pellets. This is due to a higher degree of connected channels to the outside, confirmed by the µ-CT results. For DCD-PHBV/PCL pellets, it is likely molten PCL filled the in voids/cracks forming in the PHBV matrix during production, which resulted in a diffusion controlled release mechanism. This is supported by Raman mapping and DSC results. The release profiles of DCD from DCD-PHBV pellets were modelled using a power law for the initial surface wash (0-5 h), modified first order model for II release via connected pathways (5 h-21 d) and a linear regression for the slow diffusion controlled release (21 d-56 d), based on which we predicted the release profile of DCD-PHBV pellets with other loadings. Our research indicated that DCD-loaded PHBV/PCL pellets is a practicable delivery system for the controlled release of DCD.

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Understanding the effect of copolymer content on the processability and mechanical properties of polyhydroxyalkanoate (PHA)/wood composites

Cited by 34 publications

References 44 publications

Designing for effective controlled release in agricultural products: new insights into the complex nature of the polymer–active agent relationship and implications for use

Designing for effective controlled release in agricultural products: new insights into the complex nature of the polymer–active agent relationship and implications for use

Production of the Polyhydroxyalkanoate PHBV from Ricotta Cheese Exhausted Whey by Haloferax mediterranei Fermentation

Tailoring the release of DCD from biopolymer matrices: The effect of DCD crystal size, loading, blends of PHBV and PCL and temperature on DCD release kinetic

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