Recycled Polyethylene Terephthalate Flakes Research Articles

Recycling-oriented characterization of PET waste stream by SWIR hyperspectral imaging and variable selection methods

The proposed study was carried out to develop a fast and efficient strategy for plastic waste sensor-based sorting in recycling plants, based on hyperspectral imaging (HSI), combined with variable selection methods, to produce a high-quality recycled polyethylene terephthalate (PET) flakes stream. Variable selection techniques were applied in order to identify a limited number of spectral bands useful to recognize the presence of other plastic materials, considered as contaminant, inside a stream of recycled PET flakes, reducing processing time as requested by sorting online applications. Post-consumer plastic samples were acquired by HSI device working in the short-wave infrared (SWIR) range (1000 - 2500 nm). As a first step, the hypercubes were processed applying chemometric logics to build a partial least squares discriminant analysis (PLSDA) classification model using the full investigated spectral range, able to identify PET and contaminant classes. As a second step, two different variable selection methods were then applied, i.e., interval PLSDA (I-PLSDA) and variable importance in projection (VIP) scores, in order to identify a limited number of spectral bands useful to recognize the two classes and to evaluate the best method, showing efficiency values close to those obtained by the full spectrum model. The best result was achieved by the VIP score method with an average efficiency value of 0.98. The obtained results suggested that the variables selection method can represent a powerful approach for the sensor-based sorting-online, decreasing the amount of data to be processed and thus enabling faster recognition compared to the full spectrum model.

Circular economy in the brewing chain

The main aim of this review was to check for the applicability of the concept of circular economy to brewing chain. By analyzing the beer brewing process, it was possible to identify the main brewery wastes formed and packaging materials used as well as their range of composition and yields. In order to reduce the contribution of packaging material to the carbon footprint of beer, it would be necessary to replace one-way containers used nowadays with lighter, reusable, or recycled ones. Even if the contribution of beer consumption phase was taken into account, there was no definitive solution about the less environmentally impacting beer packaging format. The direct management of polyethylene terephthalate (PET) packaging for liquid foodstuffs could make available 100% recycled PET flakes to be reconverted into food-grade bottles with minimum downcycling to other non-food usage. The countless potential uses of brewery wastes in nutritional and biotechnological fields were tested in laboratory by disregarding any cost–benefit or market analysis. This was mainly because the estimated market price of dried brewer’s spent grain (BSG) resulted to be about 450% higher than that of conventional lignocellulose residues. All the alternative uses hailed in the literature appeared to be more useful for publishing articles than for defining any economically feasible reusing procedure for all brewery wastes. Owing to their high moisture content, such wastes are so perishable as to prevent their safe usage in the human food chain. Currently, their use as-is in animal feeding is the disposal method not only economically feasible but also able to reduce the greenhouse gas load of beer packed in glass bottles (GB) by about one-third of that associated with packaging materials. Not by chance, it is practiced by most industrial and craft breweries.

A Comparative Study of Care Processes Effect on the Abrasion Resistance of some Virgin and Recycled Polyester Fabrics

Polyethylene terephthalate (PET), which commonly referred to as ‘polyester’ in the textile industry, is considered one of the most important thermoplastic polyesters. It is widely used for various applications such as bottles, fibers, moldings, and sheets because of its excellent tensile and impact strength, clarity, process-ability, chemical resistance, and thermal stability. PET bottle wastes are separated from other wastes and then some processes are applied to obtain PET flakes. Recycled polyester fibers are produced by melt spinning method from these recycled PET flakes. In this research, usability of recycled PET fibers in textile industry was studied. A comparative investigation of fabric abrasion resistance property were done to fabrics produced from virgin and recycled polyester before and after care processes.

Effect of Recycled PET Fibers on the Performance Properties of Knitted Fabrics

PET (polyethylene terephthalate) is mostly used in textile and packaging industries. PET Bottle wastes are separated from other wastes and after that some processes are applied to obtain PET flakes, such as breaking, washing, drying and etc. r-PET fibers are produced by melt spinning method from these recycled PET flakes. r-PET fibers have already been used for secondary textile products like as carpet bottoms, sleeping bags and insulation materials. In this study usability of recycled PET fibers in apparel industry were researched. Comparative investigations of bursting strength, abrasion resistance, air permeability, surface friction, circular bending rigidity and dimensional stability properties were done to knitted fabrics produced from r-PET and blends with PET and cotton fibers. It was found that, instead of PET, r-PET fibers can be blended in certain amounts without compromising fabrics performance.

Performance of Natural Aggregates and Recycled Aggregates for Unbound Granular Pavement Layers

Recycled aggregates from solid waste can be used on pavements to minimize road construction costs and decrease environmental impacts related to the exploitation of natural resources and pollution. Thus, this study aimed to compare the mechanical performance of mixtures composed of natural aggregates, concrete recycled aggregates and polyethylene terephthalate (PET) flakes (in proportions from 0.5 to 4.0%) for application in granular pavement layers. Asphalt mixing, construction and demolition solid waste recycling, and PET recycling plants located in Joao Pessoa/PB, Brazil, provided the material used in this study. Tests such as particle size distribution, compaction with intermediate energy and California Bearing Ratio (CBR) were performed. The results of particle size distribution were useful to determine particle size proportions according to Brazilian DNIT specified standards and to prepare specimens for CBR tests. The compaction results indicated optimum water contents of 8.0 and 14.9%, and maximum dry densities of 2.01 and 1.83 g/cm3, for natural aggregates and recycled aggregates, respectively. Moreover, the optimum water contents increased between 16.4 and 17.7%, while the maximum dry densities decreased from 1.773 to 1.702 g/cm3 in mixtures of recycled aggregates and PET flakes, as PET proportions rose. Assessing mechanical resistance, the CBR value of natural aggregates resulted 45%, while that of recycled aggregates resulted 61%. On the other hand, the CBR results did not show a particular behavior tendency with the addition of recycled PET flakes. Therefore, it was possible to conclude that concrete recycled aggregates are technically viable for use in building granular pavement layers (sub-base and base) with low traffic flow, in spite of the variability of CBR results for mixtures of recycled aggregates and PET flakes.

A method to determine volatile contaminants in polyethylene terephthalate (PET) packages by HDC-GC-FID and its application to post-consumer materials

A simple and low cost method to determine volatile contaminants in post-consumer recycled PET flakes was developed and validated by Headspace Dynamic Concentration and Gas Chromatography-Flame Ionization Detection (HDC-GC-FID). The analytical parameters evaluated by using surrogates include: correlation coefficient, detection limit, quantification limit, accuracy, intra-assay precision, and inter-assay precision. In order to compare the efficiency of the proposed method to recognized automated techniques, post-consumer PET packaging samples collected in Brazil were used. GC-MS was used to confirm the identity of the substances identified in the PET packaging. Some of the identified contaminants were estimated in the post-consumer material at concentrations higher than 220 ng.g-1. The findings in this work corroborate data available in the scientific literature pointing out the suitability of the proposed analytical method.

ポリエチレンテレフタレート再生材中の残存揮発性物質の分析

The residual volatiles in recycled polyethylene terephthalate (PET) were analyzed using headspace/GC/MS. Recycled PET samples were made from PET bottles used for beverages, alcohol and soy sauce, and they were recycled in physical recycling plants, chemical recycling plants and superclean-like recycling trials. The physically recycled PET flakes contained small amounts of volatiles such as ethanol, limonene, 2-methyl-1,3-dioxolane, acetone, octanal and nonanal. Most of them originated from foods packed in bottles, and only 2-methyl-1,3-dioxolane was derived from polymer impurities. In contrast, the superclean-like or chemically recycled PET contained no detectable volatiles, like new PET pellets. The PET sheets shaped from physically recycled PET had no detectable volatiles. Not only the chemically and superclean-like recycled PET, but also the physically recycled PET contained no hazardous volatiles. It was concluded that there is no safety concern about volatiles in recycled PET, for the present use.

Evaluation of some screening methods for the analysis of contaminants in recycled polyethylene terephthalate flakes

A range of different analytical techniques were used to test recycled polyethylene terephthalate (PET) flakes for potential chemical contaminants. The techniques used were headspace gas chromatography coupled to mass spectrometry (GC-MS), liquid extraction followed by GC-MS, supercritical-fluid extraction followed by GC-MS, and migration testing followed by elemental analysis using inductively coupled plasma mass spectroscopy (ICP-MS). The PET samples were 50 representative samples taken from 600 that had been collected throughout Europe and which had been screened for potential contaminants using a single technique of high-temperature GC-MS. Six of the 50 samples tested had been spiked with a selection of model contaminants, three samples were virgin PET flakes and two of the samples were from supercleaning processes. All samples were analysed ‘blind’ in this exercise. The qualitative results showed that most of the contaminants came from the first use, being flavour-aroma compounds from soft drinks. The quantitative analysis found concentrations under a few mg kg−1 in the polymer, except for the spiked samples. Element migrations were low and only calcium, silicon and sodium had median migrations above 50 µg l−1. This in-depth analysis of recycled PET flakes did not identify any significant contaminants that had not already been detected by the high-temperature static GC-MS screening method, thus demonstrating its utility.