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Molecules (Basel, Switzerland) Mar 2019Velcrands are a specific class of cavitands whose complementary surfaces induce self-dimerization. The insertion of a velcrand as physical cross-linking unit into a...
Velcrands are a specific class of cavitands whose complementary surfaces induce self-dimerization. The insertion of a velcrand as physical cross-linking unit into a polymer is reported. To this purpose, the velcrand was functionalized at the lower rim with an isocyanate group. The functional velcrand was reacted with poly (ethylene-co-(2-hydroxethylmethacrylate)) (PE-HEMA), a polymer equipped with free hydroxyl groups suitable for reaction with the isocyanate group. The obtained functionalized polymer was characterized by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR), proving the introduction of velcraplexes in the polymer. Films with varying amounts of velcrands were obtained by solution casting and slow evaporation, testifying the processability of the functionalized polymers. The obtained films were used to measure the oxygen barrier properties of the functionalized material.
Topics: Calorimetry, Differential Scanning; Chemistry Techniques, Synthetic; Magnetic Resonance Spectroscopy; Oxygen; Polyethylene; Spectroscopy, Fourier Transform Infrared
PubMed: 30841484
DOI: 10.3390/molecules24050902 -
The Science of the Total Environment Sep 2023For the past two decades, with the increase in plastic consumption came a rise in plastic waste, with the bulk of it ending up in landfills, incinerated, recycled or... (Review)
Review
For the past two decades, with the increase in plastic consumption came a rise in plastic waste, with the bulk of it ending up in landfills, incinerated, recycled or leaking into the environment, especially in aquatic ecosystems. Plastic waste poses a significant environmental threat and a wealth issue due to its non-biodegradability and recalcitrant nature. Polyethylene (PE) remains one of the major utilized polymers in different applications amid all the other types because of its low production costs, simplistic nature prone to be modified and historically predominant researched material. Since the common methods for plastic disposal are troubled by limitations, there is a growing need for more appropriate and environment friendly methods alternatives. This study highlights several ways that can be used to assist PE (bio)degradation and mitigate its waste impact. Biodegradation (microbiological activity driven) and photodegradation (radiation driven) are the most promising for PE waste control. The shape of the material (powder, film, particles, etc.), the composition of medium, additives and pH, temperature and incubation or exposure times contribute to plastic degradation efficiency. Moreover, radiation pretreatment can enhance the biodegradability of PE, providing a promising approach to fighting plastic pollution. This paper relates the most significant results regarding PE degradation studies followed by weight loss analysis, surface morphology changes, oxidation degree (for photodegradation) and mechanical properties assessment. All combined strategies are very promising to minimize the polyethylene impact. However, there is still a long way to go through. The degradation kinetics is still low for the currently available biotic or abiotic processes, and complete mineralization is thoroughly unseen.
Topics: Polyethylene; Ecosystem; Plastics; Polymers; Biodegradation, Environmental
PubMed: 37285989
DOI: 10.1016/j.scitotenv.2023.164629 -
The Journal of Craniofacial SurgeryEar reconstruction is 1 of the most technically challenging sub-specialties of craniofacial and reconstructive plastic surgery. The reconstructive ear must not only... (Review)
Review
Ear reconstruction is 1 of the most technically challenging sub-specialties of craniofacial and reconstructive plastic surgery. The reconstructive ear must not only fulfil the requirement of being aesthetically pleasing but must also have good vascularity with a low complication rate. Several ear reconstructive techniques have been developed such as the autologous ear reconstruction technique using costal cartilage and ear reconstruction with high-density porous polyethylene or Medpor (Porex Surgical, Inc, College Park, GA). Autologous ear reconstructive techniques have advantages of durability and low infection rates however are associated with poorer aesthetic outcomes such as poor projection of the ear. Medpor has advantages of a more consistent three-dimensional definition without the need to harvest costochondral cartilage and create a donor site. However, due to its alloplastic material properties, Medpor has historically been reported as having a higher rate of extrusion and infection. This is the first systematic review to compare the outcomes of both techniques. The 6 studies that were reviewed were analyzed against 3 evaluative criteria: aesthetic outcome, complication rate, and convenience of intervention. This is so a comprehensive, evidence-based decision can be made by the surgeon and patient when ear reconstruction is required. The results showed heterogeneity in data and a lack of detailed descriptions of the assessment for aesthetic outcomes and convenience, hence were inconclusive. The results however showed that there were more complications with Medpor framework with 15% of total cases resulting in either extrusion or infection compared to 2% of autologous ear reconstruction framework.
Topics: Ear, External; Esthetics, Dental; Humans; Polyethylene; Polyethylenes; Plastic Surgery Procedures
PubMed: 34643598
DOI: 10.1097/SCS.0000000000008130 -
Knee Surgery, Sports Traumatology,... Sep 2022Total knee arthroplasty (TKA) has experienced exponential growth over the last decade, including increasingly younger patients with high functional demands. Highly... (Meta-Analysis)
Meta-Analysis Review
Comparable results between crosslinked polyethylene and conventional ultra-high molecular weight polyethylene implanted in total knee arthroplasty: systematic review and meta-analysis of randomised clinical trials.
PURPOSE
Total knee arthroplasty (TKA) has experienced exponential growth over the last decade, including increasingly younger patients with high functional demands. Highly crosslinked polyethylene (HXLPE) has been proven effective in reducing osteolysis and loosening revisions while improving long-term survival and performance in total hip arthroplasty; nevertheless, this superiority is not demonstrated in TKA. The aim of this systematic review and meta-analysis was to examine whether HXLPE improved overall survival and postoperative functional and radiological outcomes compared to conventional polyethylene (CPE) in TKA.
METHODS
According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, a literature search of five databases (PubMed, Medline, Scopus, Science Direct and Embase) was made. A PICOS model was performed. The initial screening identified 2541 studies. Each eligible clinical article was analysed according to the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence (LoE). Only randomised clinical trials (RCTs) of LoE 1 and 2 were included. The methodological quality of the articles was assessed using the Risk of Bias 2 (RoB 2) tool.
RESULTS
Six clinical studies were included in the final study. This systematic review and meta-analysis were registered on the International Prospective Register of Systematic Reviews (PROSPERO). A total of 2285 knees were included. Eight outcomes (total reoperations, reoperations for prosthesis loosening and infections, radiolucent lines, osteolysis, mechanical failure, postoperative KSS knee score and function score) were analysed. For none of them, a statistically significant difference was found about the superiority of HXLPE over CPE (p > 0.05).
CONCLUSIONS
There were no statistically significant differences between HXLPE and CPE for TKA concerning clinical, radiological, and functional outcomes; nevertheless, HXLPE did not show higher failure rates or complications and can be safely used for TKA.
LEVEL OF EVIDENCE
II.
Topics: Arthroplasty, Replacement, Knee; Humans; Knee Prosthesis; Osteolysis; Polyethylene; Polyethylenes; Prosthesis Design; Prosthesis Failure; Randomized Controlled Trials as Topic
PubMed: 35182171
DOI: 10.1007/s00167-022-06879-7 -
The Science of the Total Environment Dec 2022Plastic pollution has always been a hot issue of global concern. Previous studies have mainly focused on the flow of plastics. However, information on the patterns and...
Plastic pollution has always been a hot issue of global concern. Previous studies have mainly focused on the flow of plastics. However, information on the patterns and characteristics of flow, stock, and waste in the plastic life cycle and their driving factors is limited in China, and effective waste reduction and sustainable strategies are missing. Therefore, this research established a flow model of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET); further analyzed the driving factors; and proposed strategies for waste reduction and sustainable development. We found that the total consumption, stock, and waste of PET, PE, and PP in 2010-2017 reached 552.96, 292.70, and 257.18 Tg, respectively. Building and construction (B&C), packaging, and textiles were the sectors with the largest stock of PE, PP, and PET. From 2010 to 2013, the stock of PE increased by 440 %, which was mainly driven by the increase in material utilization intensity (MUI). Similarly, the growth of MUI was the main driving factor driving PP (351 %) and PET (367 %) stocks. Notably, from 2014 to 2017, economic growth was the main factor driving the plastic stock. These results will provide a scientific basis for promoting the sustainable utilization of PE, PP, and PET and be of great significance to achieve the strategic goal of a no-waste city.
Topics: Plastics; Polyethylene Terephthalates; Polypropylenes; Product Packaging; Polyethylene
PubMed: 36075419
DOI: 10.1016/j.scitotenv.2022.158513 -
STAR Protocols Dec 2023Depolymerization and upcycling are promising approaches to managing plastic waste. However, quantitative measurements of reaction rates and analyses of complex product...
Depolymerization and upcycling are promising approaches to managing plastic waste. However, quantitative measurements of reaction rates and analyses of complex product mixtures arising from depolymerization of polyolefins constitute significant challenges in this emerging field. Here, we detail techniques for recovery and analysis of products arising from batch depolymerization of polyethylene. We also describe quantitative analyses of reaction rates and products selectivity. This protocol can be extended to depolymerization of other plastics and characterization of other product mixtures including long-chain olefins. For complete details on the use and execution of this protocol, please refer to Sun et al..
Topics: Polyethylene; Alkenes
PubMed: 37729056
DOI: 10.1016/j.xpro.2023.102575 -
Journal of the American Chemical Society Dec 2022Among commercial plastics, polyolefins are the most widely produced worldwide but have limited recyclability. Here, we report a chemical recycling route for the...
Among commercial plastics, polyolefins are the most widely produced worldwide but have limited recyclability. Here, we report a chemical recycling route for the conversion of post-consumer high-density polyethylene (HDPE) into telechelic macromonomers suitable for circular reprocessing. Unsaturation was introduced into HDPE by catalytic dehydrogenation using an Ir-POCOP catalyst without an alkene acceptor. Cross-metathesis with 2-hydroxyethyl acrylate followed by hydrogenation transformed the partially unsaturated HDPE into telechelic macromonomers. The direct repolymerization of the macromonomers gave a brittle material due to the low overall weight-average molecular weight. Aminolysis of telechelic macromonomers with a small amount of diethanolamine increased the overall functionality. The resulting macromonomers were repolymerized through transesterification to generate a polymer with comparable mechanical properties to the starting post-consumer HDPE waste. Depolymerization of the repolymerized material catalyzed by an organic base regenerated the telechelic macromonomers, thereby allowing waste polyethylene materials to enter a chemical recycling pathway.
Topics: Polyethylene; Plastics; Polymers; Waste Products; Catalysis
PubMed: 36524740
DOI: 10.1021/jacs.2c11949 -
BMC Biotechnology Jul 2023Plastic pollution is a major global concern to the health and wellbeing of all terrestrial and marine life. However, no sustainable method for waste management is...
Plastic pollution is a major global concern to the health and wellbeing of all terrestrial and marine life. However, no sustainable method for waste management is currently viable. This study addresses the optimisation of microbial enzymatic polyethylene oxidation through rational engineering of laccases with carbohydrate-binding module (CBM) domains. An explorative bioinformatic approach was taken for high-throughput screening of candidate laccases and CBM domains, representing an exemplar workflow for future engineering research. Molecular docking simulated polyethylene binding whilst a deep-learning algorithm predicted catalytic activity. Protein properties were examined to interpret the mechanisms behind laccase-polyethylene binding. The incorporation of flexible GGGGS(x3) hinges were found to improve putative polyethylene binding of laccases. Whilst CBM1 family domains were predicted to bind polyethylene, they were suggested to detriment laccase-polyethylene associations. In contrast, CBM2 domains reported improved polyethylene binding and may thus optimise laccase oxidation. Interactions between CBM domains, linkers, and polyethylene hydrocarbons were heavily reliant on hydrophobicity. Preliminary polyethylene oxidation is considered a necessity for consequent microbial uptake and assimilation. However, slow oxidation and depolymerisation rates inhibit the large-scale industrial implementation of bioremediation within waste management systems. The optimised polyethylene oxidation of CBM2-engineered laccases represents a significant advancement towards a sustainable method of complete plastic breakdown. Results of this study offer a rapid, accessible workflow for further research into exoenzyme optimisation whilst elucidating mechanisms behind the laccase-polyethylene interaction.
Topics: Laccase; Polyethylene; Molecular Docking Simulation; Oxidation-Reduction; Carbohydrates
PubMed: 37415113
DOI: 10.1186/s12896-023-00787-5 -
Microbiological Research Feb 2023Microorganisms degrade microplastics, but their potential is still not fully exploited, e.g., due to inadequate selection of microorganisms. We developed an effective...
Microorganisms degrade microplastics, but their potential is still not fully exploited, e.g., due to inadequate selection of microorganisms. We developed an effective selection method of microorganisms capable of polyethylene (PE) and polypropylene (PP) degradation and assessed the scale of polymer degradation by microbial populations. We isolated seven bacterial strains (three Priestia megaterium strains, Klebsiella pneumoniae, Pseudomonas fluorescens, Enterobacter ludwigii, Chryseobacterium sp.) and seven fungal strains (four Fusarium spp., two Lecanicillium spp. and Trichoderma sp.) with PE degradation potential, as well as seven bacterial strains (five Serratia marcescens and two Enterobacter spp.) and six fungal strains (four Aspergillus spp., Fusarium oxysporum and Penicillium granulatum) with PP degradation ability. Scanning electron microscopy (SEM) analysis confirmed the presence of a biofilm and revealed surface changes in both PE and PP pellets, but the greatest changes (microcracks and corrugations) were observed for PP incubated with bacteria. Fourier transform infrared (FTIR) spectroscopy confirmed the structural changes on the studied polymer surfaces. In conclusion, the isolation of plastic-degrading bacteria and fungi from waste landfills represents an effective strategy for the collection of microorganisms with high potential for PE and PP degradation. The bacteria and fungi revealed better potential for PP degradation and PE degradation, respectively.
Topics: Polyethylene; Polypropylenes; Plastics; Biodegradation, Environmental; Fungi
PubMed: 36423546
DOI: 10.1016/j.micres.2022.127251 -
Food Research International (Ottawa,... Oct 2023Instant coffees are consumed worldwide and their packages must protect them mainly from moisture gain. Flexible packaging stand-up pouches made by PET/Al foil/LDPE are...
Instant coffees are consumed worldwide and their packages must protect them mainly from moisture gain. Flexible packaging stand-up pouches made by PET/Al foil/LDPE are currently used but, the look for alternative materials is interesting to replace the aluminum foil with reducing costs and focusing on sustainability. Therefore, the aim of this study was to evaluate the quality loss of freeze-dried and spray-dried (agglomerated and powder) instant coffees during 365 days at 25 °C/75% RH, packaged in five plastic structures: PET (polyethylene terephthalate)/Al (aluminum) foil/LDPE (low density polyethylene), LDPE/HDPE (high density polyethylene)/LDPE, BOPP (biaxially oriented polypropylene)/BOPP met (metallized)/PP, PET/PET met/LDPE and PET/BOPP met/LDPE. The results were compared with the shelf-life estimated by modeling the moisture sorption isotherms of the products by mathematical models. Results indicated that the lower the barrier to water vapor of the packaging material, the greater the gains in moisture and water activity of the instant coffees and in addition to being thermally less stable. After 365 days of storage, the three soluble coffees still had acceptable characteristics in the five packaging structures, indicating that it is possible to replace the currently used laminate, which contains aluminum foil, with recyclable structures. However, the greatest stability for the coffees was obtained using the alternative structures: BOPP/BOPP met/PP and LDPE/HDPE/LDPE, a result that was in concordance with that obtained by mathematical modeling.
Topics: Polyethylene; Coffee; Plastics; Aluminum; Product Packaging
PubMed: 37689919
DOI: 10.1016/j.foodres.2023.113165