Microwave assisted ecofriendly recycling of poly (ethylene terephthalate) bottle waste

Glycolysis of poly (ethylene terephthalate) bottle waste was carried out using microwave energy. A domestic microwave oven of 800 W was used with suitable modification for carrying out the reaction under reflux. The catalysts used for the depolymerization in ethylene glycol (EG) were zinc acetate and some simple laboratory chemicals such as sodium carbonate, sodium bicarbonate and barium hydroxide. Comparison of results was made from the point of view of the yield of bis (2-hydroxyethylene) terephthalate (BHET) and the time taken for depolymerization. It was observed that under identical conditions of catalyst concentration and PET:EG ratio, the yield of BHET was nearly same as that obtained earlier by conventional electric heating. However, the time taken for completion of reaction was reduced drastically from 8 h to 35 min. This has led to substantial saving in energy.     

Effect of diverse weathering conditions on the physicochemical properties of biodegradable plastic mulches

The effect of simulated and agricultural weathering in two diverse US regions: Tennessee (TN) and Washington (WA), on the physicochemical properties of three commercially available biodegradable plastic mulch films (BDMs), and an experimental polylactic acid/polyhydroxyalkanoate (PLA/PHA) mulch was investigated to assess the potential impact of weather on mulch performance in specialty crop production. The tensile strength and thermostability of PLA/PHA increased by weathering, suggesting the formation of cross-links between the polyesters and inorganic filler. The decrease of mechanical properties for the commercially available BDMs differed slightly: simulated weathering > TN > WA. Chemical bonding changes due to photodegradative, hydrolytic, and oxidative reactions followed the order: TN > WA > simulated weathering. The differences reflect the higher moisture and temperature for TN compared to WA, and that simulated weathering did not mimic many secondary environmental factors, since ultraviolet radiation exposure was nearly equal between weathering treatments.     

Stability of model recycled mixed plastic waste compatibilised with a cooperative compatibilisation system

The effect of the degree of degradation of the components of a model municipal plastic waste (a mixture of low-density polyethylene, high-density polyethylene, polypropylene and high-impact polystyrene) on the toughness and stability of recyclates compatibilised with a cooperative compatibilisation system (a mixture of ethylene-propylene statistical and styrene-butadiene block copolymers with a secondary amine-based stabiliser) was studied. It was shown that good impact strength was achieved for recyclates having components with a low or medium degree of degradation. Mechanical properties of recyclates having the components with a high degree of degradation are deteriorated. The addition of the cooperative compatibilisation system leads to a higher thermo-oxidative stability of recyclates irrespective of the degree of degradation of their components. Photo-oxidative stability of the recyclates is low but it can be improved to a satisfactory level by the addition of carbon black or a commercial photo-stabiliser.     

Determination of volatile organic compounds in recycled polyethylene terephthalate and high-density polyethylene by headspace solid phase microextraction gas chromatography mass spectrometry to evaluate the efficiency of recycling processes

A method for the determination of volatile organic compounds (VOCs) in recycled polyethylene terephthalate and high-density polyethylene using headspace sampling by solid-phase microextraction and gas chromatography coupled to mass spectrometry detection is presented. This method was used to evaluate the efficiency of cleaning processes for VOC removal from recycled PET. In addition, the method was also employed to evaluate the level of VOC contamination in multilayer packaging material containing recycled HDPE material. The optimisation of the extraction procedure for volatile compounds was performed and the best extraction conditions were found using a 75 μm carboxen-polydimethylsiloxane (CAR-PDMS) fibre for 20 min at 60 °C. The validation parameters for the established method were linear range, linearity, sensitivity, precision (repeatability), accuracy (recovery) and detection and quantification limits. The results indicated that the method could easily be used in quality control for the production of recycled PET and HDPE.     

Comparison of thermal degradation products from real municipal waste plastic and model mixed plastics

The thermal degradation of real municipal waste plastic (MWP) obtained from Sapporo, Japan and model mixed plastics was carried out at 430 °C in atmospheric pressure by batch operation. The chlorinated hydrocarbons found in PE/PP/PS/PVC [poly(ethylene)/poly(propylene)/poly(styrene)/poly(vinyl chloride)] degradation liquid products were also observed in PE/PP/PS/PVC/PET (poly(ethylene terephalate)) and MWP degradation liquid products. The presence of PET in MWP produced the additional chlorinated hydrocarbons, which are similar to the chlorinated hydrocarbons observed during the PE/PP/PS/PVC/PET degradation liquid products. In addition, the presence of PET facilitated the formation of more organic chlorine content in liquid products and drastic decrease in the formation of inorganic chlorine content.     

The effect of dynamic crosslinking on morphology,thermal and mechanical properties of polylactic acid and bioelastomer blend

The objective of this work is to enhance the toughness of In the current study, inherently brittle polylactic acid (PLA) has been toughened using a biobased polyester without compromising the biocompatibility, renewability, strength and thermal properties of PLA. For this purpose, biodegradable Renewable resources resource based flexible aliphatic polyester (BBPE) has been synthesized and the same has been confirmed by FTIR and ¹H NMR. Melt blending of BBPE elastomer with PLA in presence of free radical initiator dicumyl peroxide (DCP) leads to the development of crosslinked PLA/BBPE (PBE) blends of tunable properties. Additionally, the mechanical, morphological, thermal, crosslink density and water absorption behaviour of PBE blends were explored. It was observed that the synthesized biobased BBPE elastomers contribute to toughening of the PLA matrix consequently, improving the its impact strength and elongation at break. of the blend     

The effect of covalent immobilization of sialic acid on the removal of lipopolysaccharide and reactive oxygen species for polyethylene terephthalate

Polyethylene terephthalate (PET) was aminolyzed with 1,6‐diaminohexane (DAH) and then sialic acid (NANA) was immobilized via amidation onto the surface. The surface concentration of NANA was determined by 2‐thiobarbituric acid (TBA) test. The hemocompatibility of the resulting PET fabrics was evaluated based on complete blood count (CBC), coagulating times, and protein adsorption. The ability to remove lipopolysaccharide (LPS) was also determined. In addition, the effect of contacting NANA‐immobilizing PET on the suppression of reactive oxygen species (ROS) production was measured by the chemiluminescence (CL) method. The results show that by immobilizing NANA onto PET, the adhesion of platelet (PLt) was reduced, and oxidative stress was suppressed. The level of LPS was also greatly reduced. Copyright © 2010 John Wiley & Sons, Ltd.     

Hydrolysis of post-consume poly(ethylene terephthalate) with sulfuric acid and product characterization by WAXD, C NMR and DSC

Post-consume PET was hydrolysed with commercial sulfuric acid (96%) with varying reaction times (5-120 min). The structure of the material obtained was analysed by ¹³C NMR, DSC, and WAXD and the results were correlated with reaction time. ¹³C NMR shows a decrease in chain size with reaction time and an increase in the number of carboxyl groups at the end of the chains. The correlation of DSC and WAXD data indicates the presence of structures of different sizes and an increase in crystallinity with reaction time. The structure of the samples hydrolysed for 5-60 min is less ordered than those of the samples hydrolysed for 60-120 min because the amorphous phase is predominantly quickly dissolved. Dissolution of the crystalline phase is favoured by the increase in reaction time. In this process, the crystalline memory retained in the dissolution of the crystalline phase behaves as nucleation sites which form smaller and more ordered structures compared to those obtained with shorter reaction times.     

The effect of triethyl citrate on the dispersibility and water vapor sorption behavior of polylactic acid/zeolite composites

The aim of this study was to investigate the water vapor adsorption behavior and mechanical properties of poly (lactic acid) (PLA)/zeolite (5, 10, or 15 phr) composites prepared with triethyl citrate (TEC; 20 phr) via a melting process. TEC was used to improve the flexibility of the PLA and the dispersibility of the zeolite in TEC-zeolite suspensions that were ultra-sonicated. It was found that zeolite was uniformly dispersed in the PLA matrix, and the interfacial adhesion between the PLA matrix and zeolite was enhanced by TEC. In addition, the tensile strengths and Young's modulus of the composites improved with increasing zeolite content. The PLA/zeolite composites prepared with TEC had increased water vapor permeability and contact angles compared to neat PLA and standard PLA/zeolite due to the presence of TEC. In particular, TEC accelerated the hydrolysis of the PLA surface in a high humidity environment, resulting in an improvement in water vapor sorption capacity. At the same zeolite content of 15 phr, the equilibrium moisture content (EMC) values of PLA/zeolite films prepared with TEC increased by up to 39.25 mg/g whereas those prepared without TEC only increased by up to 24.33 mg/g. The results suggest the possibility of applying PLA/zeolite films prepared with TEC as a flexible active packaging material.     

Synthesis of 3-amino 1H-pyrazoles catalyzed by p-toluene sulphonic acid using polyethylene glycol-400 as an efficient and recyclable reaction medium

Abstract

An efficient synthesis of 3-amino 1H-pyrazoles is described. The reaction of β-keto nitriles with hydrazines in the presence of a catalytic amount of p-toluene sulphonic acid using polyethylene glycol-400 as an efficient and recyclable reaction medium afforded the corresponding 3-amino 1H pyrazoles excellent yields.     

Highly selective separation and purification of chicoric acid from Echinacea purpurea by quality control methods in macroporous adsorption resin column chromatography

Chicoric acid is the main phenolic active ingredient in Echinacea purpurea (Asteraceae), best known for its immune‐enhancing ability, as well as used as a herbal medicine. To achieve further utilization of medicinal ingredients from E. purpurea, an efficient preparative separation of chicoric acid was developed based on macroporous adsorption resin chromatography. The separation characteristics of several different typical macroporous adsorption resins were evaluated by adsorption/desorption column experiments, and HPD100 was revealed as the optimal one, which exhibited that the adsorbents fitted well to the pseudo‐second‐order kinetics model and Langmuir isotherm model, and the optimal process parameters were obtained. The breakthrough curves could be predicted and end‐point could be determined early. Besides, the optimal elution conditions of chicoric acid can be achieved using the quality control methods. As a result, the purity of chicoric acid was increased 15.8‐fold (from 4 to 63%) after the treatment with HPD100. The process of the enrichment and separation of chicoric acid is considerate, because of its high efficiency and simple operation. The established separation and purification method of chicoric acid is expected to be valuable for further utilization of E. purpurea according to product application in pharmaceutical fields in the future.     

Synthesis of high‐molecular‐weight aliphatic–aromatic copolyesters from poly(ethylene‐co‐1,6‐hexene terephthalate) and poly(L‐lactic acid) by chain extension

A series of aliphatic–aromatic multiblock copolyesters consisting of poly(ethylene‐co‐1,6‐hexene terephthalate) (PEHT) and poly(L ‐lactic acid) (PLLA) were synthesized successfully by chain‐extension reaction of dihydroxyl terminated PEHT‐OH prepolymer and dihydroxyl terminated PLLA‐OH prepolymer using toluene‐2,4‐diisoyanate as a chain extender. PEHT‐OH prepolymers were prepared by two step reactions using dimethyl terephthalate, ethylene glycol, and 1,6‐hexanediol as raw materials. PLLA‐OH prepolymers were prepared by direct polycondensation of L ‐lactic acid in the presence of 1,4‐butanediol. The chemical structures, the molecular weights and the thermal properties of PEHT‐OH, PLLA‐OH prepolymers, and PEHT‐PLLA copolymers were characterized by FTIR, ¹H NMR, GPC, TG, and DSC. This synthetic method has been proved to be very efficient for the synthesis of high‐molecular‐weight copolyesters (say, higher than M_w = 3 × 10⁵ g/mol). Only one glass transition temperature was found in the DSC curves of PEHT‐PLLA copolymers, indicating that the PLLA and PEHT segments had good miscibility. TG curves showed that all the copolyesters had good thermal stabilities. The resulting novel aromatic–aliphatic copolyesters are expected to find a potential application in the area of biodegradable polymer materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5898–5907, 2009     

Degradation-fragmentation of marine plastic waste and their environmental implications: A critical review

This review critically evaluates the plastic accumulation challenges and their environmental (primarily) and human (secondarily) impacts. It also emphasizes on their degradation and fragmentation phenomena under marine conditions. In addition, it takes into account the leachability of the various chemical substances (additives) embedded in plastic products to improve their polymeric properties and extend their life. Regardless of their effectiveness in enhancing the polymeric function of plastic products, these additives can potentially contaminate air, soil, food, and water. Several findings have shown that, regardless of their types and sizes, plastics can be degraded and/or fragmented under marine conditions. Therefore, the estimation of fragmentation and degradation rates via a reliable developed model is required to better understand the marine environmental status. The main parameter, which is responsible for initiating the fragmentation of plastics, is sunlight/UV radiation. Yet, UV- radiation alone is not enough to fragment some plastic polymer types under marine conditions, additional factors are needed such as mechanical abrasion. It should be also mentioned that most current studies on plastic degradation and fragmentation centered on the primary stages of degradation. Thus, further studies are needed to better understand these phenomena and to identify their fate and environmental effects.     

Bibliometric analysis and an overview of the application of the non-precious materials for pyrolysis reaction of plastic waste

Huge plastic consumption and depletion of fossil fuels are at the top of the world's environmental and energy challenges. The scientific community has tackled these issues through different approaches. Catalytic pyrolysis of plastic wastes to valuable products has been proved as a sustainable route which fits with the circular economy aspects. The design of catalytic materials is the central factor for performing the catalytic conversion of plastic wastes. This review aims to conduct a Bibliometric analysis of the pyrolysis of plastic wastes and non-precious-based catalysts by mapping research studies over the last fifty years. The analysis was developed via VOSviewer and RStudio tools. It showed the historical progress regarding plastic waste pyrolysis to produce valuable products and chemicals worldwide. The research shows that the top five countries with the highest citations and publications in this field were Spain, China, England, the USA and India. The Journal of Analytical and Applied Pyrolysis had the most comprehensive coverage of plastic waste. The relationship between the catalyst and the mechanism of plastic waste can influence the production yield and selectivity. The research gap and underrepresented research topics were identified, and previous research studies on developing non-precious-based catalysts that were most relevant to the current topic were reviewed and discussed. The challenges and perspectives on catalyst preparation and development for material complexity were critically discussed. Challenges of previous studies and directions for future research were provided. This report might guide the reader to take a general look at plastic waste valorization by pyrolysis and easily understand the main challenges.