Structure–property relationship of recycled carbon fibres revealed by pyrolysis recycling process

The structure-property relationship for recycled carbon fibres is investigated by characterisation of the structure changes induced by the pyrolysis recycling process. Two important factors influencing the properties of recycled carbon fibres are identified for various recycling processes: oxidative effect and thermal effect. The oxidative effect results in surface defects, and the surface defects causes a reduction in tensile strength and lateral crystallite size. The thermal effect of the recycling process results in an expansion in the distance between graphite layers and a decrease in surface oxygen concentration, which would lead to a drop in interfacial shear strength with epoxy resins. The tensile strength of recycled carbon fibres has a strong correlation with the intensity ratio of the D and G bands of the Raman spectra (ID/IG). With an increase in ID/IG, the tensile strength of recycled carbon fibre decreases linearly

Forensic engineering of advanced polymeric materials Part IV: Case study of oxo-biodegradable polyethylene commercial bag – Aging in biotic and abiotic environment

This is an accepted manuscript of an article published by Elsevier in Waste Management on 03/04/2017, available online: https://doi.org/10.1016/j.wasman.2017.03.043 The accepted version of the publication may differ from the final published version.The public awareness of the quality of environment stimulates the endeavor to safe polymeric materials and their degradation products. The aim of the forensic engineering case study presented in this paper is to evaluate the aging process of commercial oxo-degradable polyethylene bag under real industrial composting conditions and in distilled water at 70 °C, for comparison. Partial degradation of the investigated material was monitored by changes in molecular weight, thermal properties and Keto Carbonyl Bond Index and Vinyl Bond Index, which were calculated from the FTIR spectra. The results indicate that such an oxo-degradable product offered in markets degrades slowly under industrial composting conditions. Even fragmentation is slow, and it is dubious that biological mineralization of this material would occur within a year under industrial composting conditions. The slow degradation and fragmentation is most likely due to partially crosslinking after long time of degradation, which results in the limitation of low molecular weight residues for assimilation. The work suggests that these materials should not be labeled as biodegradable, and should be further analyzed in order to avoid the spread of persistent artificial materials in nature

Biomass extraction using non-chlorinated solvents for biocompatibility improvement of polyhydroxyalkanoates

An economically viable method to extract polyhydroxyalkanoates (PHAs) from cells is desirable for this biodegradable polymer of potential biomedical applications. In this work, two non-chlorinated solvents, cyclohexanone and -butyrolactone, were examined for extracting PHA produced by the bacterial strain Cupriavidus necator H16 cultivated on vegetable oil as a sole carbon source. The PHA produced was determined as a poly(3-hydroxybutyrate) (PHB) homopolyester. The extraction kinetics of the two solvents was determined using gel permeation chromatography (GPC). When cyclohexanone was used as the extraction solvent at 120 C in 3 min, 95% of the PHB was recovered from the cells with a similar purity to that extracted using chloroform. With a decrease in temperature, the recovery yield decreased. At the same temperatures, the recovery yield of -butyrolactone was significantly lower. The effect of the two solvents on the quality of the extracted PHB was also examined using GPC and elemental analysis. The molar mass and dispersity of the obtained polymer were similar to that extracted using chloroform, while the nitrogen content of the PHB extracted using the two new solvents was slightly higher. In a nutshell, cyclohexanone in particular was identified as an expedient candidate to efficiently drive novel, sustainable PHA extraction processes

Understanding the dechlorination of chlorinated hydrocarbons in the pyrolysis of mixed plastics

The dechlorination of chlorine containing hydrocarbons in pyrolysis vapor is poorly understood. In order to shed new light on the dechlorination mechanism, a model mixture composed of iso-octane doped with 2-chlorobutane, 2-chloroethylbenzene, and chlorobenzene was used to study the dechlorination of chlorinated hydrocarbons by alkali adsorption. These three chlorinated hydrocarbons were selected as they can be typically produced from the pyrolysis of mixed plastic waste containing polyvinyl chloride (PVC). The mixture is pumped continuously through a Na2CO3 or CaCO3/alumina bed, and GC-MS is used to identify the dechlorination products and to follow the dechlorination reactions. When chlorine is bonded to an aliphatic carbon with an adjacent aliphatic hydrogen, the chlorinated compound first undergoes a dehydrochlorination reaction to form HCl and olefins, and subsequently the HCl is reacted with the alkali in the absorbents. In our experiments, 2-chlorobutane is converted to 2-butene, and 2-chloroethylbenzene is converted to styrene. The formation of HCl and subsequent reaction with alkali components in the absorbent is verified by IR spectroscopy and XRD. In the presence of an alkali, the aliphatic chlorinated hydrocarbons underwent dechlorination at a temperature of 180 °C. The removal of chlorine from aromatic chlorinated compounds operates in a different mechanism, in which the C–Cl bond scission is promoted significantly by the presence of an alumina and hydrocarbon medium. It was found that chlorobenzene undergoes dechlorination forming phenol and benzene

The molecular level characterization of biodegradable polymers originated from polyethylene using non-oxygenated polyethylene wax as a carbon source for polyhydroxyalkanoate production

There is an increasing demand for bio-based polymers that are developed from recycled materials. The production of biodegradable polymers can include bio-technological (utilizing microorganisms or enzymes) or chemical synthesis procedures. This report demonstrates the corroboration of the molecular structure of polyhydroxyalkanoates (PHAs) obtained by the conversion of waste polyethylene (PE) via non-oxygenated PE wax (N-PEW) as an additional carbon source for a bacterial species. The N-PEW, obtained from a PE pyrolysis reaction, has been found to be a beneficial carbon source for PHA production with Cupriavidus necator H16. The production of the N-PEW is an alternative to oxidized polyethylene wax (O-PEW) (that has been used as a carbon source previously) as it is less time consuming to manufacture and offers fewer industrial applications. A range of molecular structural analytical techniques were performed on the PHAs obtained; which included nuclear magnetic resonance (NMR) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS). Our study showed that the PHA formed from N-PEW contained 3-hydroxybutyrate (HB) with 11 mol% of 3-hydroxyvalerate (HV) units.This research was funded by the Research Investment Fund, University of Wolverhampton, Faculty of Science and Engineering, UK. This work was also partially supported under the EU 7FP BIOCLEAN Project, Contract No. 312100, “New biotechnological approaches for biodegrading and promoting the environmental biotransformation of synthetic polymeric materials

Biodegradable PBAT/PLA blend with bioactive MCPA-PHBV conjugate suppresses weed growth

This document is confidential and is proprietary to the American Chemical Society and its authors. Do not copy or disclose without written permission.The herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) conjugated with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was prepared via a melt transesterification route. The resultant bioactive oligomer was then mixed with a blend of polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) with different loadings; to manufacture films to be used as a bioactive, biodegradable mulch to deliver the herbicide to target broadleaf weed species. The biological targeting of the MCPA-PHBV conjugate in the mulch film was investigated under glasshouse conditions using faba bean (Vicia faba) as a selective (non-target) model crop species having broadleaf morphology. The presence of the MCPA-PHBV conjugate in the biodegradable PBTA/PLA blend was shown to completely suppress the growth of broadleaf weed species, whilst displaying only a mild effect on the growth of the model crop. The degradation of the mulch film under glasshouse conditions was quite slow. The release of the MCPA-PHBV during this process was detected using NMR, GPC, EDS and DSC analyses, indicating that the majority of the MCPA diffused out after MCPA-PHBV conjugate bond scission. These data provide a strong “proof of concept” and show that this biodegradable, bioactive film is a good candidate for future field applications and may be of wide agricultural applicability.This work was funded by the Research Investment Fund, University of Wolverhampton (Wolverhampton, UK)

Recycling supercapacitors based on shredding and mild thermal treatment

Supercapacitors are widely used in electric and hybrid vehicles, wind farm and low-power equipment due to their high specific power density and huge number of charge–discharge cycles. Waste supercapacitors should be recycled according to EU directive 2002/96/EC on waste electric and electronic equipment. This paper describes a recycling approach for end-of-life supercapacitors based on shredding and mild thermal treatment. At first, supercapacitors are shredded using a Retsch cutting mill. The shredded mixture is then undergone thermal treatment at 200 °C to recycle the organic solvent contained in the activated carbon electrodes. After the thermal treatment, the mixture is roughly separated using a fluidized bed method to remove the aluminium foil particles and paper particles from the activated carbon particles, which is subsequently put into water for a wet shredding into fine particles that can be re-used. The recycled activated carbon has a BET surface area of up to 1200 m2/g and the recycled acetonitrile has a high purity

Carbon sources for polyhydroxyalkanoates and an integrated biorefinery

© 2016 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/ijms17071157Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs’ biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels’ production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs

Effective control against broadleaf weed species provided by biodegradable PBAT/PLA mulch film embedded with the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA)

This is an accepted manuscript of an article published by American Chemical Society in ACS Sustainable Chemistry and Engineering on 19/03/2020, available online: https://doi.org/10.1021/acssuschemeng.0c00991 The accepted version of the publication may differ from the final published version.Biodegradable mulches are considered a promising alternative to polyethylene-based, nonbiodegradable mulch for sustainable agriculture. In the present study, a bioactive 2-methyl-4- cholorophenoxyacetic acid/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (MCPA-PHBV) conjugate blended with biodegradable poly(butylene adipate-co-terephthalate/polylactide (PBAT/PLA) was developed and used as mulch under controlled condition greenhouse pot experiment with fava bean (Vicia faba) as the nontarget crop species. The objectives were to examine the effectiveness of sustained-release of MCPA herbicide from biodegradable mulch for broadleaf weed suppression and to assess any adverse effects of the herbicide on the nontarget species (fava bean). The energy-dispersive X-ray spectroscopy analysis (EDS) suggests that a substantial quantity of the herbicide was released from the biodegradable mulch which effectively killed the broadleaf weed species even at 1% MCPA concentration. However, the higher concentrations of the herbicide adversely affected several physiological parameters of fava bean growth and development. Stomatal conductance decreased, while leaf temperature subsequently rose (at MCPA concentrations 5, 7.5, and 10%). The quantum yield of the Photosystem II (PSII) indicates that the photosynthetic efficiency was also restricted at concentrations 7.5% and 10%. Evidently, this slow-release herbicide system worked efficiently for broadleaf weed control but at higher concentrations, resulted in adverse physiological effects on the nontarget crop species. This study has demonstrated that biodegradable mulches containing MCPA herbicide are able to effectively inhibit the growth of broad leaf weed species and may be of potential importance in a wide variety of horticultural and agricultural applications.Published onlin

Oxidized polyethylene wax as a potential carbon source for PHA production

© 2016 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/ma9050367We report on the ability of bacteria to produce biodegradable polyhydroxyalkanoates (PHA) using oxidized polyethylene wax (O-PEW) as a novel carbon source. The O-PEW was obtained in a process that used air or oxygen as an oxidizing agent. R. eutropha H16 was grown for 48 h in either tryptone soya broth (TSB) or basal salts medium (BSM) supplemented with O-PEW and monitored by viable counting. Study revealed that biomass and PHA production was higher in TSB supplemented with O-PEW compared with TSB only. The biopolymers obtained were preliminary characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The detailed structural evaluation at the molecular level was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The study revealed that, when TSB was supplemented with O-PEW, bacteria produced PHA which contained 3-hydroxybutyrate and up to 3 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units. The ESI-MS/MS enabled the PHA characterization when the content of 3-hydroxybutyrate was high and the appearance of other PHA repeating units was very low