Chemical Recycling Process Research Articles

Degradation of Post-consumer PLA: Hydrolysis of Polymeric Matrix and Oligomers Stabilization in Aqueous Phase

Degradation of post-consumer PLA to lactic acid was analysed in order to assess the economic feasibility of the PLA chemical recycling process. Hydrolysis of PLA, in batch reactor, was analysed in the temperature range of 443–473 K, under autogenous pressure and a constant PLA to water ratio (equal to approximately 0.11 by weight), without the use of a catalyst. The experimental results suggest that the complete degradation of PLA can be obtained using relatively low reaction-times with the production of a mixture containing the monomer and traces of the dimer of lactic acid. The overall process was modelled using a two-step process: bulk degradation of PLA (in the solid or molten phase) with the solubilisation of low molecular weight oligomers, and their subsequent hydrolysis in water (stabilization). The model describes the trend of oligomer concentrations in the aqueous phase and PLA conversion as a function of time with both high accuracy and agreement with experimental results.

Improvement of the chemical recycling process of waste carbon fibre reinforced plastics using a mechanochemical process: Influence of process parameters.

We present the experimental results of an optimal recycling method for waste carbon fibre reinforced plastics (CFRPs) that is based on the application of a set of unit mechanochemical processes. The objectives of this study were to highlight the influence of process factors that are inherent in the chemical recycling process of waste CFRP. We investigated the influence of the soaking period, the application of a catalyst and impurities on the recycling process and recovery efficiency of the waste CFRP. Different combinations of the unit mechanochemical processes were investigated, and the effectiveness of the combination was analysed. The chemical recycling process was conducted using benzyl alcohol under ordinary pressure at initial solvent temperatures lower/equivalent to its flash point temperature. Experimental results showed that the solvent temperature increased up to boiling temperature levels when the mechanochemical process was initiated, thereby enhancing the mechanochemical process. The presence of impurities did not influence the recovery rate. Likewise, this experimental study highlighted the importance of accounting for the soaking period during the chemical recycling process: an extended soaking period resulted in a higher recovery rate, a lower portion of undissolved solids and recovered fibres of better quality. This research highlighted the significance of choosing the proper combination for the chemical recycling process as well as the benefits of recycling the waste CFRP with negligible application of the catalyst.

The influence of different glycerine purities on chemical recycling process of polyurethane waste and resulting semi‐products

Chemical recycling is the most favourable recycling method due to the possibility of polyol recovery. This work is dedicated to the utilisation of crude glycerine and polyurethane waste. It aims at determining the impact of the use of glycerine from the production of biodiesel with various degrees of purity as a cleavage agent on the decomposition process of polyurethane foam. The influence of glycerine purity on the chemical structure of recycling products was analysed using Fourier transform infrared and 1H NMR spectroscopies and gel permeation chromatography. Hydroxyl and amine values were determined, and rheological measurements were performed. Glycerolysates showed minor structural differences due to the presence of amine groups and exhibited heterogeneous structure compared to original polyols. The ones obtained in decomposition using 84 and 99.5% glycerine had a lower viscosity below 0.45 Pa s at 50 °C and higher hydroxyl number of 183 and 220 mg KOH g−1, respectively, compared to the ones obtained with glycerine purity of 40 and 62% due to a different chemical structure. All of the products of decomposition were defined as non‐Newtonian fluids, where viscosity depended on the shear rate. Selected glycerolysates were used in the production of cast polyurethanes with satisfactory mechanical properties. © 2018 Society of Chemical Industry

Comparing Life Cycle Energy and Global Warming Potential of Carbon Fiber Composite Recycling Technologies and Waste Management Options

Carbon fibre reinforced polymers (CFRP) are used in increasing quantities as they have some of the best properties in terms of specific strength and stiffness of any widely available material. By 2020, annual global CFRP production is expected to be over 140,000 tonnes. However, the resulting increased quantity of CFRP waste has highlighted the need for sustainable treatment options as carbon fibre manufacture has high-energy intensity. A life cycle methodology is used to evaluate primary energy demand (PED) and global warming potential (GWP) leveraging best available literature data, process models, and experimental work. Overall results indicate that recycling scenarios are generally the environmentally preferable options over landfill and incineration. However, the relative environmental benefits of advanced recycling processes (i.e., pyrolysis, fluidised bed, and chemical recycling process) depend on the method used to determine displacement of virgin carbon fibre by recycled carbon fibre. Totally, recycling processes can achieve a representative GWP of -19 to -27 kg CO2eq. and PED of -395 to -520 MJ per kg CFRP, providing superior environmental performance to conventional composite waste treatment technologies.

Conversion of polyurethane technological foam waste and post-consumer polyurethane mattresses into polyols – industrial applications

Researches were carried out to determine the possibility of reusing polyols produced in the chemical recycling process of polyurethane (PUR) foam technological waste and post-consumer mattresses for the production of mattresses and thermal insulation panels. It was found that such PUR waste can be converted into repolyol by similar processes that are currently used at Dendro Poland LTD Sp. z o.o. The mixture containing repolyols was used to produce rigid and flexible polyurethane-polyisocyanurate (PUR-PIR) foams. It was found that a mixture of polyols containing up to 50 wt % of repolyols can be used in the production of flexible PUR-PIR foams. The most suitable application for recycled polyol from post-consumer foam waste was identified as rigid PUR-PIR foam for thermal insulation. The produced rigid foams showed good performance in the foaming process, foam structure and dimensional stability. The practical application of chemical recycling of post-consumer mattresses is of great environmental importance and, additionally, the obtained repolyol is cheaper than the standard polyol.

Innovative Chemical Process for Recycling Thermosets Cured with Recyclamines® by Converting Bio-Epoxy Composites in Reusable Thermoplastic-An LCA Study.

An innovative recycling process for thermoset polymer composites developed by Connora Technologies (Hayward, CA, USA) was studied. The process efficacy has already been tested, and it is currently working at the plant level. The main aspect investigated in the present paper was the environmental impact by means of the Life Cycle Assessment (LCA) method. Because of the need to recycle and recover materials at their end of life, the Connora process creates a great innovation in the market of epoxy composites, as they are notoriously not recyclable. Connora Technologies developed a relatively gentle chemical recycling process that induces the conversion of thermosets into thermoplastics. The LCA demonstrated that low environmental burdens are associated with the process itself and, furthermore, impacts are avoided due to the recovery of the epoxy-composite constituents (fibres and matrix). A carbon fibre (CF) epoxy-composite panel was produced through Vacuum Resin Transfer Moulding (VRTM) and afterwards treated using the Connora recycling process. The LCA results of both the production and the recycling phases are reported.

An Efficient Method of Recycling of CFRP Waste Using Peracetic Acid

We report a one-step oxidative method for the recycling of carbon fiber-reinforced polymer (CFRP) composite waste and the recovery of carbon fiber and the epoxy resin by treatment with peracetic acid (PAA) formed in situ from a mixture of acetic acid and hydrogen peroxide. The surfaces of the recovered carbon fibers were clean, and the tensile strength was comparable to that of the virgin fibers. A higher resin decomposition ratio of 97% could be achieved for the epoxy matrix under mild reaction conditions in comparison to other chemical recycling processes. ATR-FTIR, MALDI/TOF-MS, GPC, GC-MS, 1H NMR, and Pyro-GC/MS analyses showed the formation of low molecular weight oxidation products of amine-cured epoxy resin along with high molecular weight compounds of high viscosity. A possible reaction mechanism for the degradation of the epoxy matrix is proposed. All the solvents used were recovered in pure and reusable form with more than 90% recovery efficiency. The recovered epoxy was reused along with an adh...

Surface analysis of glass fibres using XPS and AFM: case study of glass fibres recovered from the glass fibre reinforced polymer using chemical recycling

In this study, we present the results of an experimental study of the use of the X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) to characterise the coatings of the recovered E – glass fibres. The recovered E – glass fibres were obtained using chemical recycling process coupled with ultrasound cavitation. The objective of this study was to analyse the impact of chemical recycling and the ultrasound cavitation process on the sizing properties of the recovered fibres. We obtained the recovered fibres and sized using 1 wt% 3 – aminopropyltriethoxysilane (APS). Part of the sized fibres was washed with acetone and analysed all the sample fibres using AFM and XPS. Results showed the different composition of sizing after extraction using acetone. We compared the results of this study with that of virgin clean glass fibres.

Mehanička i toplotna svojstva ekološki prihvatljivog premaza dobijenog od proizvoda nastalih iz otpadnog polietilentereftalata

The technology used in creating coatings is very important for the environmental science field. Regarless to the available types of raw materials, new methods of combining materials or the evolution of traditional technologies, coatings provide a range of options to meet different the range of environmental performances and appearance requirements. In this work, chemical recycling process of polyethylene terephthalate was investigated, since, the bottles grade consumption is reaching high levels, especially those of bottled water and soft drinks. Waste polyethylene terephthalate (PET) flakes were depolymerized using ethylene glycol. The resin based on waste PET was prepared from phthalic anhydride (PA), glycerin (G), ricinoleic acids and glycolyzed products of waste PET. The mechanical, thermal and chemical properties were tested. The properties of the resin based on waste PET were found to be compatible with the properties of the reference one. The synthesized resin based on waste PET could be potentially employed as the composition for the preparation of eco-friendly baking enamels.

The utilisation of oils produced from plastic waste at different pyrolysis temperatures in a DI diesel engine

Chemical recycling is an attractive way to address the explosive growth of plastic waste and disposal problems. Pyrolysis is a chemical recycling process that can convert plastics into high quality oil, which can then be utilised in internal combustion engines for power and heat generation. The aim of the present work is to evaluate the potential of using oils that have been derived from the pyrolysis of plastics at different temperatures in diesel engines. The produced oils were analysed and found to have similar properties to diesel fuel. The plastic pyrolysis oils were then tested in a four-cylinder direct injection diesel engine, and their combustion, performance and emission characteristics analysed and compared to mineral diesel. The engine was found to perform better on the pyrolysis oils at higher loads. The pyrolysis temperature had a significant effect, as the oil produced at a lower temperature presented higher brake thermal efficiency and shorter ignition delay period at all loads. This oil also produced lower NOX, UHC, CO and CO2 emissions than the oil produced at a higher temperature, although diesel emissions were lower.

Increasing textile circulation—Consequences and requirements

The global textile fiber production, consumption of textiles and amounts of textile waste are constantly growing. The increase of textile waste has also been demonstrated in sorting studies performed for the municipal solid waste, where the share of textiles has grown. Ideally, recycling and, even more so, reusing textiles can reduce the production of new textiles from virgin materials and hence reduce the use of water, energy and chemicals in the production chain. The aim of the study was to ascertain the flows of textiles and textile waste currently in Finland and assess the environmental performance of the current system. In addition, the possible consequences of a significant increase in the reuse or recycling of discarded textiles were analyzed. Finally, an assessment on the policy measures available for increasing textile circulation was performed.An account of the textiles and textile waste flows in Finland in 2012 showed that roughly 20% of discarded textiles were collected separately by charity organizations and directed mainly towards reuse. Only a few percent of the overall flow was recycled. The majority of the discarded textiles were collected in municipal solid waste (MSW) and incinerated with energy recovery. The life cycle assessment (LCA) of the current situation and two comparing scenarios showed that environmental benefits could be obtained by increasing the separate collection of discarded textiles and their reuse or recycling. The results were dominated by the benefits potentially obtained from compensating virgin textile production with reuse or recycling. However, it is not known how much textile reuse actually compensates virgin production, or whether it simply generates new markets and adds to the overall demand and consumption of textiles. Similarly, there are uncertainties about whether recycled fibers can replace virgin fibers due to the fact that chemical recycling processes are still being developed. Research and development activities are already in progress for increasing the circulation of textiles. While developing the textile chain it must be taken into account that the whole chain for collecting, sorting, separating and recovering needs to be developed simultaneously and the operations optimized in order to keep environmental impacts to a minimum.Well-accepted voluntary producer responsibility could be one way to increase the collection of discarded textiles, but it requires the engagement of producers, operators and consumers. The use of recycling criteria in public procurements to enhance recycling requires an increase of recycled products in the market and advice for procurers.Both increased reuse and increased recycling require major changes to the current system and the engagement of all operators of the textile chain.

PLA Chemical Recycling Process Optimization: PLA Solubilization in Organic Solvents

The recycling of used, post-industrial and post-consumer PLA is crucial to reduce both the consumption of renewable resources for the monomer synthesis and the environmental impact related to its production and disposal. Several processes are actually available: among these, there is a particular interest on the chemical recycling of PLA with production of its monomer. The aim of this work is to analyse the PLA dissolution behaviour in different organic solvents (acetone and Ethyl lactate) at different water concentrations in order to optimize the chemical depolymerisation process of PLA. New experimental data are presented and a kinetic model is provided for a first analysis. Preliminary results suggest that acetone based solvents (i.e., acetone water mixtures at various concentrations) are more effective to solubilize the PLA rather than the Ethyl-lactate based solvent. Anyway, an increase of water concentration in the solvent phase, determines both a reduction of the solvent power and a reduction of mass transport coefficient for the two solvents tested.

Recovery of Metals from Electronic Waste by Physical and Chemical Recycling Processes

Recovery of Metals from Electronic Waste by Physical and Chemical Recycling Processes

Sodium titanium tris(glycolate) as a catalyst for the chemical recycling of poly(ethylene terephthalate) via glycolysis and repolycondensation

Poly(ethylene terephthalate) (PET) was chemically recycled through glycolysis with ethylene glycol (EG) and repolycondensation of its main depolymerized product bis(2-hydroxyethyl terephthalate) (BHET). In this process, synthesized sodium titanium tris(glycolate) was used as a new catalyst for both reactions. The catalytic efficiency and selectivity of sodium titanium tris(glycolate) in both reactions has been investigated and compared with conventional catalysts used in glycolysis or polycondensation. The results indicate that sodium titanium tris(glycolate) is a desirable catalyst for chemical recycling of PET because it can present high catalytic activity and selectivity not only in glycolysis but also in repolycondensation, which means high cost of the catalysts separation between two reactions during chemical recycling process could be avoided. Meanwhile, a mechanism of the glycolysis of PET catalyzed by sodium titanium tris(glycolate) was proposed based on the results of interactions among BHET, EG and catalysts revealed by infrared spectroscopy.

Characterization of recycled polyethylene terephthalates and polyethylene terephthalate–nylon6 blend knitted fabrics

For environmental conservation, post-consumer polyethylene terephthalate (PET) bottles are recycled using methods ranging from mechanical recycling to various chemical recycling processes. In this study, the characterization of recycled PETs and PET–nylon6 blend knitted fabrics, and virgin PET knitted fabric, was carried out with the aim of broadening the application of recycled PET fabrics. The tensile strength values of mechanically and chemically recycled PET knitted fabrics were similar to those of virgin PET knitted fabric. The elongation of recycled PET–nylon6 blend knitted fabric was the best. Both virgin and recycled PET knitted fabrics had excellent pilling resistance. Based on the drape ratio, the recycled PET–nylon6 blend knitted fabric was more flexible than other samples. The warm/cool feeling ( Qmax), compressional and surface properties were measured using the Kawabata evaluation system for fabrics (KES-FB system). The compressional properties of mechanically recycled PET knitted fabric were similar to those of virgin PET knitted fabric. The recycled PET–nylon6 blend knitted fabric showed the smoothest appearance and coolest feeling among the four samples. Moisture regain and moisture permeability were the best in recycled PET–nylon6 blend knitted fabric. However, the wickability of mechanically recycled PET knitted fabric was better than other recycled PET knitted fabrics.

Hydrolysis of poly(lactic acid) into calcium lactate using ionic liquid [Bmim][OAc] for chemical recycling

Hydrolysis of poly(lactic acid) (PLA) to calcium lactate was studied using an ionic liquid catalyst, 1-butyl-3-methylimidazolium acetate [Bmim][OAc], to develop a chemical recycling process for waste PLA. The influences of experimental parameters, such as reaction time, reaction temperature, [Bmim][OAc] dosage and water dosage on the hydrolysis results of PLA were examined. A study on reusability of the ionic liquid showed that it could be reused up to 7 times with no noticeable decrease in the hydrolysis conversion of PLA and the yield of calcium lactate. A mechanism of PLA hydrolysis in [Bmim][OAc] was proposed. In addition, the kinetics of this reaction was investigated. The results demonstrated that the hydrolysis process was a first-order kinetic reaction in the presence of [Bmim][OAc] and the activation energy is 133.9 kJ/mol.

A Closed-Loop Process from Microwave-Assisted Hydrothermal Degradation of Starch to Utilization of the Obtained Degradation Products as Starch Plasticizers

A green closed-loop water-based process for chemical recycling of starch was demonstrated. The process starts from microwave-assisted controllable starch degradation to functional chemicals and continues to utilization of the formed degradation products, glucose and levulinic acid (LA), as starch plasticizers. The degradation process and the effect of process parameters on the formed degradation products and residues were carefully fingerprinted by multiple techniques, e.g., NMR, ESI-MS, FTIR imaging, UV–vis, and SEM. The degradation process took place in three steps, proceeding from rupture of starch granules and oligosaccharide formation to further hydrolysis to glucose. Finally, at well-defined time point rapid degradation of glucose to LA and formic acid (FA) was initiated through a 5-hydroxymethyl furfural (5-HMF) intermediate. 5-HMF also participated in carbonization reactions leading to formation of solid carbon spheres. Through selection of processing parameters, LA could be produced in high yield with 95% selectivity. The results demonstrated that microwave-assisted degradation of starch leads to well-defined controllable degradation products. These products are directly reusable as plasticizers for new starch products, which suggest great opportunities for biomass and starch recycling, opening the door toward potential industrial applications.

Microwave-Assisted Reaction in Green Solvents Recycles PHB to Functional Chemicals

An efficient microwave-assisted process for chemical recycling of poly(3-hydroxybutyrate) (PHB) in green solvents was demonstrated. Previously, PHB has been thermally recycled to crotonic acid and unsaturated oligomers. Our aim was to utilize green solvents (water, methanol, and ethanol) under alkaline conditions to achieve fast hydrolysis and monomeric or oligomeric degradation products with carboxyl and hydroxyl or methoxy or ethoxy end groups. Preliminary screening confirmed that the most efficient degradation process was obtained in alkaline methanol. In addition, sample amount, sodium hydroxide concentration, and degradation time all influenced the degradation process and final degree of degradation. Comparison with pure thermal degradation clearly demonstrated the effectiveness of the microwave-assisted process as the time and temperature needed for complete degradation was significantly reduced. Several characterization techniques were utilized for mapping the degradation processes and resulting degradation products. After optimization of the process, complete degradation of PHB to monomeric degradation products (3-hydroxybutanoic acid, 3-methoxybutanoic acid, and crotonic acid) was reached after only 20 min of microwave heating at 110 °C. Functional chemicals for synthesis or modification of biopolymers are thus obtainable from microwave-assisted degradation of PHB in green solvents. This offers new possibilities for retaining the material value of PHB via chemical recycling.

Chemical modification of bisphenol a polycarbonate by reactive blending with ethylene carbonate

ABSTRACTA new method for the insertion of aliphatic moieties into bisphenol A (BPA) polycarbonate (PC) by reactive blending with ethylene carbonate (ETC) has been developed. By this route, new polymeric materials with modified thermal and rheological properties have been synthesized; the structure of the poly(ether‐co‐carbonate)s prepared can be controlled using different ETC/PC molar ratios. Using model compounds and selective degradation reactions, the different chemical structures of the aliphatic units inserted into PC backbone were identified. ETC/PC molar ratios below 1 afforded both aliphatic–aromatic carbonate and ether groups, while higher ETC/PC molar ratios afforded aliphatic–aromatic ether and aliphatic–aliphatic carbonate groups. The co‐polymers prepared by the new process were clear without discoloration or opacity. The thermal analyses of the co‐polymers showed that, by the insertion of aliphatic moieties, it is possible to modulate the glass transition temperature (Tg) in a 30°C range. A decreased melt viscosity of the co‐polymers was also observed and therefore an improved processability should be expected with respect to standard PC. The reaction with aliphatic carbonates can be also considered as a promising chemical recycling process for PC scraps, through the synthesis of monomers such as bis(hydroxyethyl)ether of BPA. This monomer has already been used for the preparation of co‐polyesters of terephthalic acid with high Tg and thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39820.

Chemical Recycling of PLA: A Great Opportunity Towards the Sustainable Development?

This work aims at analyzing the energy efficiency of the chemical recycling process of polylactic acid (PLA) and its sustainability from an environmental point of view. The results show that the production of lactic acid from chemical depolymerization of PLA is preferable, from an energy point of view, to the production of lactic acid by glucose fermentation. The study also shows that the environmental footprint of the analyzed process is larger than that of the PLA mechanical recycling.