Pyrolysis of Polypropylene and Nitrile PPE Waste: Insights into Oil Composition, Kinetics, and Steam Cracker Integration.

Nitrile butadiene rubber (NBR) is a polymer widely used in pipe fittings as a sealing and damping element. The performance of the polymer materials degrades with time and temperature. The present work emphasizes the thermal degradation of NBR materials using thermogravimetric analysis (TGA) at heating rates of 5, 10, 15, and 20 °C min−1 in a controlled nitrogen environment. Model-free methods, namely the Kissenger, Kissinger-Akahira-Sunose (KAS), and Ozawa-Flynn-Wall (OFL) approaches, are used to determine the kinetic activation energy and frequency factor. The obtained values were used to calculate the lifetime of virgin NBR and the remaining life of naturally aged NBR. Fourier-transform infrared spectroscopy (FTIR) was used to detect changes in the functional groups of the NBR material with age. From the experimental data, it is concluded that virgin NBR has better thermal stability than naturally aged NBR. Furthermore, the activation energy of NBR is temperature-dependent, and oxidative aging has a significant impact on the degradation of kinetic parameters. At lower conversion rates, the activation energy of virgin NBR (79.39 kJ mol−1) and aged NBR (78.25 kJ mol−1) are almost the same, while at increased conversion rates, virgin NBR (529.77 kJ mol)−1 has higher activation energy than aged NBR (280.15 kJ mol−1).

Malaysia, wearing face mask during Covid-19 outbreak were mandatory. This action has caused significant surge in face mask production which deem to affect environment and human health. This paper evaluates and compared the environmental impacts, in a life cycle assessments perspective between disposable surgical face mask and reusable cloth face mask using cradle-to-grave approaches according to ISO 14040. The environmental impacts were assessed based on nine midpoint impact categories which are ozone depletion, greenhouse gases, acidification, eutrophication, smog formation, human health cancer and non-cancer, human health particulates and ecotoxicity. The functional unit for both types of face masks is a person wearing face mask as protection every day for one year (365 masks for disposable surgical face mask and 3 masks for reusable cloth face mask). The LCA tool used was OpenLCA software with Ecoinvent consequential 3.7.1 version database and TRACI 2.1 for impact method assessment. The study showed that reusable cloth face mask had the lowest impact compared to disposable surgical face mask across the assessed midpoint impact categories. This study suggested incineration as the best disposal method for the End-of-Life (EoL) of both face masks. Sensitive analysis also performed by manipulating the amount of face mask used per individual and it was found that the amount of mask used had significant effects to the environmental performance.

Mechanisms and kinetics of isothermal polymerization of N,N′-bismaleimide-4,4′-diphenylmethane with 5,5-dimethylbarbituric acid in the presence of triphenylphosphine

To reduce virus transmission, the use of personal protective equipment (PPE) increased substantially during the COVID-19 global pandemic. As a result, disposable face masks and gloves made from plastic polymers rapidly entered the environment, with little understanding of ecological impacts. Many plastic polymers sink to the bottom of freshwater bodies, either immediately or following biofouling and degradation, posing a potential risk to the benthos. We assessed the acute and chronic ecotoxicity of disposable polypropylene face masks and nitrile gloves on Lumbriculus variegatus, a benthic ecosystem engineer. In microcosm experiments, we also investigated direct impacts on sediment biogeochemistry and indirect impacts mediated by toxicity to L. variegatus. Exposure to fragments of both masks and gloves decreased vitality of L. variegatus. Gloves were acutely toxic, but mask toxicity was mediated by physical interactions. Glove fragments significantly decreased nitrogen removal and phosphorus release to the water column. Both materials suppressed the ecosystem engineering role of L. variegatus by decreasing its impact on microalgal primary production, net ecosystem metabolism, and sediment nitrate consumption. The influx of PPE to the environment may have profound and cascading negative impacts on benthic organisms and ecosystem function, suggesting the need for improved management of PPE litter.

In the present work, the pyrolysis of polypropylene and polyethylene was evaluated with and without the addition of niobium oxide as catalyst by means of thermogravimetric analysis and experiments in a glass reactor. The results revealed that niobium oxide performed well in the pyrolysis of both polypropylene and polyethylene separately. For the mixture of polypropylene with polyethylene, the catalyst reduced the pyrolysis time.

This study investigates the shelf life of nitrile butadiene rubber (NBR) based on age and temperature factors. Natural aging of nitrile butadiene rubber samples is performed under laboratory conditions for 2 years, followed by thermogravimetric analysis to evaluate Arrhenius parameters. Toop’s equation is used to predict shelf life at 5% conversion rate. Model-free kinetic methods, including Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS), and Kissinger, estimate shelf life at different temperatures for both virgin and naturally aged nitrile butadiene rubber. Results show close correlation between KAS and Kissinger methods, with slight variations in activation energy impacting shelf life. Fourier-transform infrared spectroscopy (FTIR) tests assess functional group changes with age. Virgin nitrile butadiene rubber activation energy: OFW-73.33 kJ/mol, KAS-68.43 kJ/mol. Aged nitrile butadiene rubber activation energy: OFW-72.57 kJ/mol, KAS-67.88 kJ/mol. Shelf life at 40°C: Virgin nitrile butadiene rubber - OFW-111.29 years, KAS-26.31 years. Aged nitrile butadiene rubber - OFW-89.01 years, KAS-22.37 years. These findings provide valuable insights for predicting and assessing nitrile butadiene rubber viscoelastic damper performance in engineering applications.

A total of 5.4 million tons of face masks were generated worldwide annually in 2021. Most of these used masks went to landfills or entered the environment, posing serious risks to wildlife, humans, and ecosystems. In this study, batch low-pressure hydrothermal processing (LP-HTP) methods are developed to convert disposable face masks into oils. Three different materials from face masks were studied to find optimal processing conditions for converting full face masks into oil. The oil and gas yields, as well as oil compositions, depend on the feedstock composition, particle size, and reaction conditions. Yields of 82 wt.% oil, 17 wt.% gas, and minimal char (~1 wt.%) were obtained from full masks. LP-HTP methods for converting face masks have higher oil yields than pyrolysis methods in the literature and have lower operating pressures than supercritical water liquefaction. LP-HTP methods for face masks can increase net energy returns by 3.4 times and reduce GHG emissions by 95% compared to incineration. LP-HTP has the potential to divert 5.4 million tons of waste masks annually from landfills and the environment, producing approximately 4.4 million tons of oil.

A two-stage process was employed for high yield production of multi-walled carbon nanotubes (MWCNTs) via pyrolysis of polypropylene (PP) waste. In the first stage, a new design was used for the pyrolysis of PP waste at 500 °C to form a mixture of condensable hydrocarbons (≥C6) and non-condensable gases (C1–C5) inside a vertical reactor closed from the bottom and connected directly to a vertical condenser at the top. This pyrolysis technique permitted to form a large amount of non-condensable hydrocarbon gases, which were used in the second stage as a carbon source for the production of MWCNTs over Co-Mo/MgO catalyst. The influences of growth temperature (700–850 °C) and carrier gas flow rate of N2 (50–110 sccm) on the yield and morphology of as-deposited MWCNTs have been investigated. The fresh Co-Mo/MgO catalyst and the as-deposited carbon were characterized by XRD, FTIR, TPR, BET surface properties, TEM, Raman spectroscopy and TGA. The results demonstrated that the adjustment of growth temperature and N2 flow-rate caused a marked impact on the yield, type and quality of as-grown MWCNTs. The optimum MWCNTs yields of 32.6 and 38.3 g/gcatalyst have been achieved at the growth temperature of 800 °C and the carrier gas flow rate of 90 sccm, respectively. TEM images illustrated the formation of pure MWCNTs at the growth temperature range of 700–800 °C, whereas mixed materials of MWCNTs and graphene nanosheets (GNSs) were obtained at the growth temperature of 850 °C. Raman spectroscopy illustrated that highly graphitized and crystalline MWCNTs were produced at all operating conditions. TGA proved that all MWCNTs samples exhibited higher thermal stability.

Non-isothermal oxidation kinetics of single- and multi-walled carbon nanotubes (CNTs) have been studied using thermogravimetry up to 1273 K in ambient using multiple heating rates. One single heating rate based model-fitting technique and four multiple heating rates based model-free isoconversional methods were used for this purpose. Depending on nanotube structure and impurity content, average activation energy (Ea), pre-exponential factor (A), reaction order (n), and degradation mechanism changed considerably. For multi-walled CNTs, Ea and A evaluated using model-fitting technique were ranged from 142.31 to 178.19 kJ mol−1, respectively, and from 1.71 × 105 to 5.81 × 107 s−1, respectively, whereas, Ea for single-walled CNTs ranged from 83.84 to 148.68 kJ mol−1 and A from 2.55 × 102 to 1.18 × 107 s−1. Although, irrespective of CNT type, the model-fitting method resulted in a single kinetic triplet i.e., Ea, A, and reaction mechanism, model-free isoconversional methods suggested that thermal oxidation of these nanotubes could be either a simple single-step mechanism with almost constant activation energy throughout the reaction span or a complex process involving multiple mechanisms that offered varying Ea with extent of conversion. Criado method was employed to predict degradation mechanism(s) of these CNTs.

The fallen leaf has the potential to be energy-valorized in cities with sustainability goals. Thermochemical characterization of garden waste through pyrolysis and combustion kinetics will establish the reactivity of this lignocellulosic biomass as biofuel for thermochemical conversion processes for energy recovery. Herein, the thermal degradation of two types of pellets produced from fallen leaf (pellets without glycerol PG0, and pellets with 5 wt% glycerol PG5) are characterized under inert and oxidative atmospheres using three different approaches: thermogravimetry (TG) and differential thermogravimetry (DTG) analyses, TG-based reactivity, and reaction kinetics from three model-free isoconversional methods. The model-free isoconversional methods are Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Friedman, which were applied for estimating the kinetic parameters, activation energy (Eα) and pre-exponential factor, using different heating rates (20, 30, and 40 °C/min) to ensure reliable data interpretation. The pyrolysis results showed that PG5 was more reactive compared to PG0 because the addition of glycerol during the pelletizing process increased the volatile matter and oxygen content in PG5. Likewise, the higher reactivity of PG5 under pyrolysis was determined by average activation energy (Eα) with an average value of 96.82 kJ/mol compared to 106.46 kJ/mol for PG0. During the combustion process, Eα was 90.70 kJ/mol and 90.29 kJ/mol for PG0 and PG5, respectively. Finally, both materials exhibited higher reactivity under an oxidative atmosphere. Therefore, according to our results, the pellets produced from leaf litter can be used as biofuels for thermochemical processes, highlighting that using glycerol as a binder favors the reactivity of the densified garden waste.

Isothermal polymerization kinetics of N,N′-bismaleimide-4,4′- diphenylmethane with cyanuric acid

Determination of thermal degradation behavior and kinetics parameters of chemically modified sun hemp biomass

Multicomponent devolatilization kinetics and thermal conversion of Imperata cylindrica

Modified neoprene adhesive dedicated to bonding UHMWPE and 45# steel was prepared. Thermal analysis with TG-DTG curve was determined and its thermal decomposition kinetics was studied. The result show that the thermal degradation process of CR/MMA/CPE/MgO adhesive is a three-step reaction and the its thermal degradation starting temperature is 200°C and complete decomposition temperature is 570°C. The first mass loss stage is 0.6 order chemical reaction and its average activation energy E is 19.21kJ/mol and pre-exponential factor A is 3.68×102. The second mass loss stage is 3 order chemical reaction and its average activation energy E is 82.14kJ/mol and its pre-exponential factor A is 1.52×108. The third mass loss stage is 3 order chemical reaction and its average activation energy E is 55.07kJ/mol and pre-exponential factor A is 1.33×105.

A comprehensive kinetics study of coconut shell waste pyrolysis