Multilayer Plastic Research Articles

Simultaneous Material and Chemical Recycling of Waste PET/PE Multi-Layer Films under Hydrothermal Conditions.

Multi-layer plastic films are widely used in various fields especially for packaging, but due to complex composition, it is very difficult to recover single-material polymers or high-purity monomers from them after usage. In this study, we proposed a hydrothermal process for recycling PET/PE (PET: Polyethylene terephthalate; PE: Polyethylene) films. PET can be hydrolyzed to monomers of terephthalic acid (TPA) and ethylene glycol (EG). Using a hydrothermal system equipped with two filters, PE, TPA, and EG were collected separately, indicating the simultaneous material and chemical recycling of PET/PE films was firstly achieved. At 300 °C and 10 MPa for 60 min, PET conversion reached around 100 %, and TPA yield of 83.0 % was obtained with a high TPA purity of 96.1 %. In addition, the effect of the holding time on PET conversion, TPA yield, EG yield, and TPA purity was studied. This research opened up a new and sustainable pathway to recycle multi-layer plastic films in both lab and industry.

Pyrolysis of multilayered plastic packets to hydrocarbon fuel feedstock: Thermal degradation behaviour, kinetics and thermodynamic analysis, and semi-batch studies

This study examines the kinetics and batch pyrolysis behavior of multilayered waste milk packets to optimize their conversion into valuable products. Using thermogravimetric analysis at heating rates of 5, 10, 15, and 20 °C/min and employing the model fitting and model-free methods such as the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Kissinger methods, the process was found to follow an F1 order-based mechanism with an activation energy of 304 kJ/mol and a pre-exponential factor of 2.60 × 1012 min.−1 The maximum weight loss (97.2 %) occurs at 5 °C/min. The average changes in free energy, enthalpy, and entropy are 814.939 kJ/mol, 135.698 kJ/mol, and −903.846 × 10−3 kJK−1mol−1 respectively. At 450 °C, the maximum pyrolytic oil yield reaches 66.92 %, with FTIR analysis confirming the presence of diverse hydrocarbon components such as alkanes, alkenes, cycloalkanes, aromatic hydrocarbons etc. in the oil. Kinetic triplet and thermodynamic parameter data, alongside physical and chemical analyses, suggest that the pyrolytic oil from multilayered waste milk packets could serve as a superior substitute for petrochemical fuel oil.

Compositional analysis of multilayered plastic constituents and constituent mixtures using benchtop 1H NMR spectroscopy.

Multilayered plastics are widely used in food packaging and other commercial applications due to their tailored functional properties. By layering different polymers, the multilayered composite material can have enhanced mechanical, thermal, and barrier properties compared to a single plastic. However, there is a significant need to recycle these multilayer plastics, but their complex structure offers significant challenges to their successful recycling. Ultimately, the use and recycling of these complex materials requires the ability to characterize the composition and purity as a means of quality control for both production and recycling processes. New advances and availability of low-field benchtop 1H NMR spectrometers have led to increasing interest in its use for characterization of multicomponent polymers and polymer mixtures. Here, we demonstrate the capability of low-field benchtop 1H NMR spectroscopy for characterization of three common polymers associated with multilayered packaging systems (low-density polyethylene [LDPE], ethylene vinyl alcohol [EVOH], and Nylon) as well as their blends. Calibration curves are obtained for determining the unknown composition of EVOH and Nylon in multilayered packaging plastics using both the EVOH hydroxyl peak area and an observed peak shift, both yielding results in good agreement with the prepared sample compositions. Additionally, comparison of results extracted for the same samples characterized by our benchtop spectrometer and a 500-MHz spectrometer found results to be consistent and within 2wt% on average. Overall, low-field benchtop 1H NMR spectroscopy is a reliable and accessible tool for characterization of these polymer systems.

Effect of functional fillers in solvent‐free polyurethane adhesives: Processing and characterization

AbstractThe present work is focused on the study of polyurethane adhesives in the presence of functional fillers (encapsulated enzymes) intended to make them degradable. This is part of a general strategy aiming to recycle multilayer films for packaging, at their end of life, by means of separating the constituent layers as a result of adhesives degradation. Primarily, it was found that the presence of small quantities of functional filler greatly affects both, the quality of the coating process and the kinetics of the adhesive curing. The former, because of the dependency on particle size distribution, leads to high variations in thickness and mechanical properties of multilayers and, the latter, because of a significant catalytic effect (higher curing rates). Indeed, an assessment of the adhesives' kinetics by rheology showed that the pot‐life and the cross‐over point (G′ = G″) for the enzyme‐containing system were obtained three times faster in comparison to the control formulation. These findings were also confirmed by differential scanning calorimetry measurements. On the other hand, by reducing and homogenizing the filler's particle size using separated sieved material (≤50 μm), improvements in coating control as well as in the quality and final properties of the multilayers were evidenced.Highlights Recycling multilayer plastic films for flexible packaging. Encapsulated enzymes to degrade the polyurethane adhesive in specific conditions. The presence of functional fillers affects the coating process. Process optimization to ensure the coating quality control.

Impact of thermomechanical reprocessing on multilayer plastic packaging blend

Multilayer plastic packaging (MPP) has attracted extensive attention due to its functionality and inherent difficulty in reclamation. One primary concern is the performance of reprocessed MPP since it inherently consists of many dissimilar polymers. This study aims to assess the effect of multiple thermomechanical reprocessing cycles on the properties of a MPP blend. Low density polyethylene (LDPE)/maleic anhydride grafted linear LDPE (LLDPE-g-MA)/ethylene vinyl alcohol (EVOH) blend was manufactured and subjected to thermomechanical reprocessing, including thermal compounding, grinding, and injection molding for six cycles to characterize the impact of thermomechanical reprocessing on the blend's mechanical, morphological, thermal, and rheological properties. The tensile strength and modulus of the reprocessed blend remained consistent throughout six cycles. A pronounced decline in elongation at break was observed after four cycles of reprocessing. Toughness, as represented by the essential work of fracture, increased steadily up to three cycles of processing, followed by a decline in the following reprocessing cycles. The main property change is possibly caused by the gelling of the EVOH in the reprocessed blend, as demonstrated by larger EVOH agglomerates in the LDPE matrix. Differential scanning calorimetry results indicated that the degree of crystallization of the EVOH phase changed with increasing reprocessing cycles, suggesting EVOH degradation. Rheological behavior in the linear viscoelastic region indicated enhanced interfacial interaction between LDPE and EVOH due to the cross-linking of LLDPE-g-MA and rigid EVOH in the early reprocessing stages. After four cycles of reprocessing, decreases in storage and loss moduli were observed, indicating the possibility of phase separation caused by gelling of EVOH. Using polymer blending to reclaim LDPE-based EVOH multilayer is promising for up to four cycles of reprocessing as shown by mechanical, thermal, and rheological behaviors.

Tackling Low-Value Plastics: Environmental and Health Concerns

Plastic pollution, spanning macroplastics to nanoplastics, poses multifaceted challenges. Low-value plastics (LVP), like multi-layered plastics (MLP) and soft plastics, are often discarded, exacerbating environmental issues. LVP's classification, with high collection costs and complex recycling, demands immediate attention. This study explores LVP management solutions, including converting to plastic lumber and RDF products. Anticipated advancements in multilayer plastic recycling offer hope, with downcycling as an option. LVP's environmental and health impacts, including microplastic contamination and toxin release during incineration, underscore the need for sustainable waste practices and plastic alternatives. Addressing LVP is crucial for environmental and human health, ensuring sustainability. Keywords: Low-value plastics, Multi-Layered Plastic (MLP), Health implications, Recycling challenges

The Recycling Technologies of Mono-material and Multilayer Plastic Film: A Descriptive Literature Review

Plastic-based flexible films are widely used in many areas of modern industry, including the food industry. Depending on the application field, mono-material or multi-material films can be used, usually based on polyolefins such as PE and/or PP. Compared to mono-material films, multilayer films offer greater performance and functionality in terms of mechanical and barrier properties, thanks to the different types of polymers used. Considering the end-of-life of the two types of materials, the recyclability of mono-material film turns out to be much greater than that of a multilayer, since only one type of polymer can be handled in specific and specialized streams. The biggest issue with multilayer films is precisely end-of-life management, which currently appears to be mainly landfilling or waste-to-energy. In recent years, the use of increasingly sustainable packaging has become a prerequisite. The issue of recycling is of fundamental importance because of the implementation of a circular economy. This review aims to investigate recycling methodologies for both mono-material and multi-material films, from traditional ones, such as mechanical recycling, to more modern technologies not widely used in industry, such as delamination and chemical recycling.

Exploring the low-temperature performance of MPP-modified asphalt binders and mixtures using wet method

Thermal cracking significantly impacts the structural integrity of flexible pavements, particularly in colder regions like Canada. Limited studies investigated the impact of plastic modification of asphalt binders and mixtures using the wet method on the low-temperature performance of asphalt materials. The plastic material utilized in this project is multilayer plastic packaging (MPP). This study aims to determine whether MPP can be integrated to enhance the performance of the MPP-modified binder and MPP-modified mixtures, especially considering that MPP accounts for just over 40% of total plastic usage, making it the largest end-use market segment. This research evaluates the impact on rheological and mechanical behaviour when introducing MPP additives to conventional hot mix asphalt. This study used the wet method to test MPP-modified asphalt materials at 2%, 4%, and 8% (by weight of the asphalt binder). Test results demonstrate that the MPP modification percentage should ideally not exceed 2% as blends with 4% MPP or higher exhibited lower performance at low temperatures. The use of a softer binder as a base binder would help increase the MPP modification rates, but this hypothesis needs to be validated experimentally.

Hydrothermal Processing of Multilayer Plastic Film for Cascaded Valorization of Nonrecyclable Waste

Hydrothermal Processing of Multilayer Plastic Film for Cascaded Valorization of Nonrecyclable Waste

Catalytic upcycling of post-consumer multilayered plastic packaging wastes for the selective production of monoaromatic hydrocarbons

In order to obtain extended storage life of food-grade materials and better barrier properties against environmental factors, a multilayer plastic packaging (MLP) is often used. The multilayer packaging plastics are labelled as “other” (SPI#7) category, and are manufactured with a combination of barrier plastics, rigid plastics and printing surface. Owing to their complex composition and difficulty in separating the layers of MLP, its mechanical recycling is challenging. In this study, MLP wastes (MLPWs) were collected from zero-waste garbage collection center of IIT Madras, India, and thoroughly characterized to determine their composition and plastic types. MLPWs were characterized using various physico-chemical methods such as thermogravimetric/differential scanning calorimetric analysis, Fourier transform infrared spectroscopy, bomb calorimetry, and proximate and ultimate analyses. The MLPWs were mainly made up of polyethylene (PE) and polyethylene terephthalate (PET). Further, the non-catalytic and zeolite-catalyzed fast pyrolysis of these MLPWs were studied using analytical pyrolysis coupled with gas chromatograph/mass spectrometer (Py-GC/MS). The non-catalytic fast pyrolysis of MLPWs primarily produced a mixture of aliphatic and alicyclic hydrocarbons, while zeolite catalyzed fast pyrolysis resulted in the formation of mono-aromatic hydrocarbons (MAHs). The activity of HZSM-5, zeolite Y (HY) and zeolite beta (Hβ) catalysts were evaluated, and the salient products were quantified. The yields of MAHs like benzene, toluene, ethylbenzene and xylene using the zeolites followed the trend: HZSM-5 (14.9 wt%) > HY (8.1 wt%) > Hβ (7.8 wt%), at 650 °C. The use of HZSM-5 resulted in highest yield of MAHs, viz. 16.1 wt%, at the optimum temperature of 550 °C and MLPW-to-catalyst ratio of 1:15 (w/w). The superior activity of HZSM-5 is due to its nominal acidity and larger pore size of 4.24 nm, as compared to HY and Hβ. The MAHs yield from three other types of MLPWs varied in the range of 9–16 wt%. The present study demonstrates a promising pathway for the catalytic upcycling of highly heterogeneous MLPWs in the context of circular economy.

Study of mechanical properties of multilayer composite plastic blocks with various materials

ABSTRACT Plastic waste is considered a global environmental disaster due to its extensive negative impacts on ecosystems, human health, and the overall well-being of the planet. Approximately 91% of plastic waste, including multi-layer plastic (MLP), is yet to be recycled and ends up in the landfill, incinerated or in the environment. MLP can be used as a construction material since it exhibits the necessary characteristics. This study evaluated the mechanical properties of multilayer plastic (MLP) composite blocks as a wall material. Two types of composite plastic blocks were tested: one made entirely of MLP and the other composed of MLP (80%) and mixed material (20%). The mixed material included sawdust powder, stone dust, and cement mixed with sand. Tests were conducted to measure the compressive strength, water absorption, and fire resistance of the blocks. The MLP composite block mixed with cement and sand in a ratio of 1:5 exhibited the highest compressive strength at 9.43 MPa, while the 100% MLP block had the lowest compressive strength at 2.73 MPa. The MLP composite block mixed with sawdust showed the highest water absorption at 11.35%, while the 100% MLP block had the lowest water absorption at 0.96%. The 100% MLP composite block ignited and melted within 2 minutes during the fire test, while the MLP composite block mixed with cement and sand did not ignite during 10 minutes of burning. It was concluded that the composite blocks containing 100% MLP do not meet the requirements for wall construction. This study also found that 80% MLP mixed with 20% cement and sand in a ratio of 1:5 exhibits the best mechanical properties among all blocks. MLP content with a considerable portion of each plastic composite block product will help reduce plastic waste in the environment.

Super-resolution Fluorescence Imaging of Recycled Polymer Blends via Hydrogen Bond-Assisted Adsorption of a Nile Red Derivative.

A key challenge in the recycling of multilayer plastic films of polyethylene and polyamide, as typically used for food packaging, is to assess and control the phase separation of the two types of polymers in the recycled material, the specifics of which determine the mechanical strength of the recycled material. However, visualizing the polyamide-in-polyethylene domains with conventional fluorescence methods or electron microscopy is challenging. We present a new approach that combines the point accumulation in nanoscale topography (PAINT) super-resolution method with a newly synthesized Nile Red probe (diOHNR) as the fluorescent label. The molecule was modified to undergo a hydrogen bond-assisted interaction with the polyamide phase in the blend due to its two additional hydroxyl groups but preserves the spectral properties of Nile Red. As a result, the localization density of the probe in the PAINT image is 13 times larger at the polyamide phase than at the polyethylene phase, enabling quantitative evaluation of the spatial polyamide/polyethylene distribution down to the nanoscale. The method achieved a spatial resolution of 18.8 nm, and we found that over half of the polyamide particles in a recycled sample were smaller than the optical diffraction limit. Being able to image the blends with nanoscopic resolution can help to optimize the composition and mechanical properties of recycled materials and thus contribute to an increased reuse of plastics.

Decohesion of a polyolefin overlay from a substrate high density polyethylene layer by impact induced stress waves

High-density polythene (HDPE) is difficult to separate from food packaging waste for recycling because the packaging occasionally has multilayer plastic labels attached. Solvents are employed in the current separation techniques to remove undesirable layers from HDPE substrates. The possibility of separating HDPE via the impact-delamination phenomenon was explored both theoretically and experimentally. Using the cohesive zone model (CZM), the decohesion of layers in a model two-layer laminate made of HDPE and LDPE layers was studied theoretically. According to this study, stress waves emerge and severely damage the adhesion between the layers as a cutting blade strikes the laminate at speeds greater than 40 m/s. The damage can be enhanced by increasing the strike velocity and the apex radius of the blade. These findings show that a novel plastic delaminator that can cut and delaminate the laminates simultaneously can be designed. The proposed machine will feature two sets of blades with varying edge apex radii. One set of blades can be designed to cause the most adhesion damage while the other blades cut the laminate. This unique combination of cutting and delamination operations has several benefits, including less solvent waste and downstream processes, greater environmental friendliness, and faster HDPE separation.Laminates from HDPE milk bottles were cut using a high-speed cutter-blender with six blades to test the predicted results. The cut HDPE flakes were separated pneumatically. According to FTIR analysis and SEM, only a trace of adhesive was present on the cut and separated HDPE flakes.

Evaluation and identification of chemical migrants leached from baby food pouch packaging

Multilayer plastic pouch (MLPP) has an estimated 9% annual increase of market growth. However, the migrants it can introduce to food has not yet been systematically studied. A total of 79 MLPPs for baby food were purchased from major retail outlets in Australia. The methodology for testing chemical migration followed the design of previous studies using four types of selected simulants according to the European Committee Regulation No. 10/2011 method. Four bisphenols and five phthalic acid diesters (PAEs) were detected, including the ones known for endocrine disrupting effect in human. Three intentionally added and 23 non-intentionally added substances (NIAS) were tentatively identified through a suspect screening procedure. Out of the 23 NIAS, neopentyl glycol – phthalic acid – 1,6-hexanediol – phthalic acid oligomer was identified for the first time with MLPP. A further two NIAS were detected for the first time in baby food related products. For 40% of the pouches where adipic acid - diethylene glycol was detected, the estimated exposure from consuming one pouch of food per day may exceed the threshold of toxicological concern established based on the Cramer classification.

Recycling of a post-industrial printed multilayer plastic film containing polyurethane inks by solvent-targeted recovery and precipitation

The recently reported Solvent-Targeted Recovery And Precipitation (STRAP) strategy is used to deconstruct multilayer plastic packaging films into their constituent resins by selective polymer dissolution. To broaden the applicability of STRAP, we demonstrate the process with a flexible post-industrial printed multilayer plastic film used for food packaging. The material was a reverse printed film composed of polyethylene (PE), ethylene vinyl alcohol (EVOH), polyethylene terephthalate (PET), and polyurethane (PU)-based inks. Removal of all colors was observed with biomass-derived gamma-valerolactone (GVL) and the recovered polymers possessed comparable properties to the corresponding virgin resins. A technoeconomic analysis indicates that this STRAP process could be economically feasible at a processing capacity of 6,000 tons per year. Moreover, the production of plastic films with materials recovered by this STRAP process can have a lower climate change impact than the production of films from virgin polymers.

Multilayer plastic film chemical recycling via sequential hydrothermal liquefaction

Multi-material layered plastic films are used in the food packaging industry due to their excellent properties; however they cannot be mechanically recycled. In this study, a two-stage hydrothermal liquefaction (HTL) process is proposed and tested for chemical recycling of a two-layer film made of LLDPE-PET. Experimental results showed that after a first subcritical stage at 325 °C, 94% of terephthalic acid (TPA) is recovered from the PET fraction as a solid and 47% of ethylene glycol in the aqueous phase. The unconverted PE was then used as feedstock for a subsequent supercritical HTL stage at 450 °C for 90 min, achieving mass yields of 47% and 29% in a naphtha-gasoline oil and in an alkane-rich gas, respectively. In conclusion, this work proved that a sequential HTL procedure can be used for chemical recycling of multilayer plastics, allowing the recovery of PET monomers to be recycled back to the PET industry and a paraffinic oil and hydrocarbon-rich gas phase that could be used as feedstock for steam cracking to produce virgin materials.

Mono-material product design with bio-based, circular, and biodegradable polymers

Mono-material product design with bio-based, circular, and biodegradable polymers

Analysis of the Delamination Process with Nitric Acid in Multilayer Composite Food Packaging

Multilayer packaging, commonly referred to as composite materials, is widely utilized in food storage, distribution, and consumption. The employment of plastic packaging, which consists of multiple layers of polymers, ink, paper, and metal, has elicited concerns regarding its detrimental impact on the environment. This article presents an in-depth study of the delamination process of multilayer plastic waste (MLPW) recycling, which is deemed as an effective solution for MLPW recycling. This study aimed to examine the effects of temperature, concentration, width, and ultrasound on the separation of layers in multilayer packaging. The results demonstrated that ultrasound is the most influential factor with nitric acid concentration ranking as the second most significant factor. The findings also disclosed considerable disparities among the time frames, and the impacts of various factors, such as temperature and concentration, lay the groundwork for further investigation into this process. The study underscores the importance of temperature and nitric acid concentration, which can inform the design of future experiments and the development of more efficient methods for layer separation.

THE EFFECT OF MULTILAYER PLASTIC WASTE ADDITION TO POLYMER MODIFIED BITUMEN CHARACTERISTICS

Bitumen, one of the main components in manufacturing asphalt, is essential for the growing development of infrastructure in Indonesia. Improving the quality of bitumen and the utilization of multilayer plastic waste is the background of this research. Modified bitumen by adding multilayer plastic waste is called Polymer Modified Bitumen (PMB). This study aimed to determine the effect of adding multilayer plastic waste as a bitumen mixture filler. The method used to mix this material is hot melt mixing. The independent variables used were stirring temperatures of 170, 180, and 190 °C, and the composition of plastic waste is 3, 4, and 5 wt%. The characterizations were FTIR, TGA, contact angle test, and SEM. The results showed that the higher the composition level of multilayer plastic waste, the higher the dispersion properties of the mixture and the lower the thermal stability of the mixture.

An innovative shock-absorbing blue silicone shell to reduce breakage of veterinary pharmaceutical glass vials

Although glass is an excellent material for manufacturing containers for pharmaceutical use, it remains fragile. This study aimed to support the qualities of glass by protecting the bottles with a shell made of polysiloxane elastomer, and to compare the relative resistance to breakage of this combination with that of a specifically designed plastic bottle.320 vials (250 and 500 ml) made of both glass and plastic, containing injectable veterinary drugs, were subjected to serial drop tests. A first group of containers (SCG: Silicone-Coated Glass) made of Type-1 glass were protected at the shoulder and bottom by a blue silicone soft shell, while those in the second group (LAS: Layered Anti-Shatter) were made of layered shatter-resistant plastic available on the market. Drop tests were carried out at three different angles (0°, 45°, 90°) from the vertical axis of the drop, from two drop heights (80 and 120 cm). All drop conditions (angle, height) and packaging (250 and 500 ml) combined, the risk of breakage of SCG vs LAS vials was RR=0.250 (shattered/intact ratio: 6/154 vs 24/136, 95% CI [0.105;0.595], P=0.002). Up to h=80 cm, no SCG (250 or 500 ml) was broken (0/80), compared to 9/71 for LAS (RR=0.053, 95% CI [0.003; 0.889], P=0.041). The 45° drop on the heel of the bottle produced the most damage for LAS containers (0/80 vs 23/57, RR=0.021; 95% CI [0.001; 0.344], P=0.007). In the event of an accidental fall, the contents of the glass bottle in a silicone shell are significantly better protected than in the multi-layer plastic bottle.