Predominant Degradation Mechanism Research Articles

The impact of mechanical recycling on the degradation of polyamide

There is currently no agreement on the degradation mechanisms for PA6 as a result of mechanical recycling. In this study, PA6 was extruded five times to simulate mechanical melt recycling process. Both virgin PA6 and the extruded PA6 were characterised to determine the predominant degradation mechanism. Melt flow rate (MFR) increases with increasing number of extrusion passes suggesting a reduction in melt viscosity due to mechanical processing. Gel permeation chromatography (GPC) results confirmed a reduction in molecular weight from 18,600 g/mol to 13,100 g/mol. Chain ends titration showed a decrease in the concentration of both the amine and carboxyl chain ends after the fifth extrusion. There were no changes to the chemical structure of the virgin PA6 and extruded PA6 observed from the Fourier transform infra-red (FTIR) and Nuclear magnetic resonance (NMR) spectra. X-ray photoelectron spectroscopy (XPS) showed a reduction in the C–N peak area supporting the scission of the N-alkylamide bond. The increase in the O=C–N peak area suggests that chain recombination via branching is possible. The shorter chains have higher mobility, and this gives rise to an increase in the crystallisation rate as seen from the differential scanning calorimeter (DSC) thermograms. The appearance of the γ phase after the fifth extrusion was identified in the DSC melting endotherms. The understanding of the degradation process of recycled PA6 will enable targeted modifications involving the incorporation of additives in the recycling process to ensure good mechanical properties in the recycled polymer.

Insight into recycling spent power ternary cathode materials: Towards preparation of Mn-based catalyst for efficient toluene removal

Both the resource utilization of spent power ternary lithium-ion batteries (LIBs) and degradation of volatile organic compounds (VOCs) by thermal catalytic oxidation are environmental concerns. In this study, a novel perspective is presented: the Mn-based composite metal oxide catalysts were synthesized via impregnation of spent ternary cathode materials for the thermocatalytic oxidative degradation of toluene gas. The results demonstrated that the optimal conditions for catalyst synthesis were a 2% Mn loading, a Co/Mn molar ratio of 0.4, and calcination at 500 ℃ for 6 h. The effectiveness of catalysts is determined by two inherent factors: the specific surface area and the presence of active sites on the surface. The degradation of toluene remained stable across various reaction environments, with the predominant degradation mechanism being Marks-Van-Kreven (MVK) model. The toluene undergoes oxygenation on the catalyst in this pathway, resulting in the formation of H2O, CO2, and intermediates containing benzene rings; and simultaneously, the catalyst is regenerated. The present study offers a valuable reference for the resource utilization of spent ternary LIBs and advances the development of catalysts for efficient degradation of VOCs.

Towards operation‐stabilizing perovskite solar cells: Fundamental materials, device designs, and commercial applications

AbstractOver the last decade, perovskite solar cells (PSCs) have drawn extensive attention owing to their high power conversion efficiency (single junction: 26.1%, perovskite/silicon tandem: 33.9%) and low fabrication cost. However, the short lifespan of PSCs with initial efficiency still blocks their practical applications. This operational instability may originate from the intrinsic and extrinsic degradation of materials or devices. Although the lifetime of PSCs has been prolonged through component, crystal, defect, interface, encapsulation engineering, and so on, the systematic analysis of failure regularity for PSCs from the perspective of materials and devices against multiple operating stressors is indispensable. In this review, we start with elaboration of the predominant degradation pathways and mechanism for PSCs under working stressors. Then the strategies for improving long‐term durability with respect to fundamental materials, interface designs, and device encapsulation have been summarized. Meanwhile, the key results have been discussed to understand the limitation of assessing PSCs stability, and the potential applications in indoor photovoltaics and wearable electronics are demonstrated. Finally, promising proposals, encompassing material processing, film formation, interface strengthening, structure designing, and device encapsulation, are provided to improve the operational stability of PSCs and promote their commercialization.image

Effect of AST Atmosphere on Pt/C Electrocatalyst Degradation

The targeted development of novel stress testing protocols as well as the production of highly active and stable catalysts require abandoning a trial-and-error approach and transitioning to identifying the principal degradation mechanisms of electrocatalysts for PEMFCs under various conditions. Methodological aspects of research related to both qualitative and quantitative assessment of the materials’ robustness against degradation and its mechanisms become the key issues. In this study, accelerated stress testing has been conducted in Ar and O2 to identify the influence of the atmosphere on the degradation and durability mechanisms of the Pt/C catalysts. Initial and final parameters after the AST have been studied in detail by transmission electron microscopy and voltammetry using the rotating disk electrode technique. The Ostwald ripening (redeposition) of platinum particles has been established to be the predominant degradation mechanism during the testing in an O2 atmosphere, this being the agglomeration of nanoparticles during the testing in Ar. An ultra-small size and a narrow size distribution of platinum nanoparticles, as well as their uniform spatial distribution over the surface of the carbon support, have been shown to allow both ORR activity to be increased and durability to be enhanced.

Stability evaluation and quantitative analysis of filmy cathode in solid oxide fuel cells under operating conditions

For interface-modified cathodes via the infiltration method, the quantitative analysis of degradation mechanism in solid oxide fuel cells (SOFCs) is the key to optimizing cell stability. Here, we prepare the anode-supported SOFC with a multifunction layer (MFL) cathode-infiltrated filmy La0.6Sr0.4CoO3-δ (LSC), which provides a peak power density as high as 1.1 W cm−2 at 750 °C, and outstanding durability with slight voltage loss under 0.5 A cm−2 and 750 °C for over 1000 h. According to collected data from electrochemical impedance spectroscopy (EIS) at different operating times, the distribution of relaxation time (DRT) and equivalent circuit model (ECM) methods are applied to quantify the contribution of different electrode processes to the whole voltage degradation during the cell operation. The result shows that oxygen ionic transport and charge transfer at the MFL/electrolyte interface dominate almost all voltage degradation (95.31%), while the oxygen surface exchange and oxygen ionic bulk diffusion in the cathode just contributes 1.82%. Microtopographic characterization provides that the filmy morphology of LSC cathode remains intact, but the Sr element enriches at the MFL/electrolyte interface. Therefore, the exacerbation of oxygen ionic transport and charge transfer at the MFL/electrolyte interface due to Sr enrichment is identified as the predominant degradation mechanism during long-term galvanostatic operation.

Atomically-resolved structural changes of ceramic supported nanoparticulate oxygen evolution reaction Ir catalyst

The reduction of Ir loading and thus its efficient utilization in proton exchange membrane water electrolyzers (PEM-WE) inevitably depends on the rational design of novel nanomaterials. This, however, is not possible without the understanding of structure-stability interrelations and underlying mechanisms. When pursuing the reduction of Ir amount by its dispersion on ceramic materials, the interactions between the catalytically active sites and their support further complicate the already understood processes. In the present study, we use our unique approach, where we employ an Ir/TiON-based TEM grid and use it as a support system for the investigation of structural transformations of Ir nanoparticles. This was achieved by utilizing both the modified floating electrode (MFE) apparatus, which enables efficient bubble management during electrochemical experiments and identical-location scanning transmission electron microscopy (IL-STEM) approach. The analysis of obtained high-resolution images with in-house developed computer algorithms for image analysis reveals several processes with surface roughening being the predominant degradation mechanism. Additionally, suppressed oxidation tendency of supported Ir was directly confirmed.

Effect of interface roughness on the tribo-corrosion behavior of diamond like carbon coatings on titanium alloy

Substrate surface morphology can significantly affect the functional performance and durability of the subsequently deposited coatings. In the present work, diamondlike carbon films were prepared by radio frequency plasma enhanced chemical vapor deposition on Ti-6Al-4V alloy substrates with different premediated surface roughness parameters (average roughness Ra, Skewness Rsk and Kurtosis Rku), and their mechanical, electrochemical, and tribo-corrosion properties were studied. The surface parameters, the microstructure, and the chemical composition were assessed by optical profilometry, scanning electron microscopy, Raman spectroscopy, and energy dispersive spectroscopy. The mechanical properties were evaluated using depth-sensing indentation and scratch testing, and the films' tribo-corrosion behavior was determined using a reciprocating tribometer in a ball-on-flat configuration with the tribological contact (Al2O3 counterpart) immersed in a 3.5% NaCl sea waterlike solution. The evolution of the corrosion potential as a function of time before, during, and after the wear tests indicated that the tribo-corrosion behavior is strongly affected by the surface roughness parameters. The potential of samples with Ra = 20 nm was unaffected by the rubbing process under the chosen tribological conditions compared to samples with higher Ra values. A similar trend was observed for samples with negative Rsk as opposed to those with Rku values greater than 3. The poor tribo-corrosion behavior of samples with Ra > 20 nm and high Rku (greater than 3) is mainly due to the significant height of asperities that constitute initiation sites for stress and strain failure on the surface. The predominant degradation mechanism was abrasive wear for samples with high surface roughness, tested under dry wear conditions. In the tribo-corrosion process, a synergy between the abrasive wear and corrosion was found to contribute to the overall material loss.

Predictive Modeling of Dye Solar Cell Degradation

Degradation of dye solar cell performance based on the early changes in electrolyte color is predicted, allowing to estimate the lifetime of the dye solar cells even before their efficiency declines. Previous predictive models commonly rely on regression analysis of the predicted parameter; thus, they are unable to capture degradation before a significant decrease in performance. Degradation tests, even when accelerated, may take thousands of hours. As such, recognizing degradation trends early can lead to rewarding cuts in the duration of solar cell development pipelines. With accurate lifetime predictions, researchers can steer materials research to reach longer lifetimes in shorter cycles. The predictive power of our model relies on color changes in the electrolyte that directly correlate with the concentration of tri‐iodide charge carriers within it, the loss of which is the predominant degradation mechanism for most liquid‐electrolyte dye solar cells. By linking the physical mechanisms inside the cell, which eventually start to degrade the performance of dye solar cells, an early prediction of the lifetime can be made even when the device performance still appears stable. It is exemplified with dye solar cells that integrating architecture‐specific knowledge on degradation mechanisms has potential to improve lifetime predictions for photovoltaics.

Shifts of surface-bound •OH to homogeneous •OH in BDD electrochemical system via UV irradiation for enhanced degradation of hydrophilic aromatic compounds

Indirect electrochemical oxidation by hydroxyl radicals is the predominant degradation mechanism in electrolysis with a boron-doped diamond (BDD) anode. However, this electrochemical method exhibits low reactivity in removal of hydrophilic aromatic pollutants owing to mass transfer limitation. In this study, the combination of ultraviolet light and BDD electrolysis could increase the degradation rate of hydrophilic aromatic pollutants by approximately 8–10 times relative to electrolysis alone. According to the results of the scavenging experiments and identification of benzoic acid oxidation products, surface-bound hydroxyl radical (•OH(surface)) was the primary reactive species degrading aromatic pollutants in the BDD electrolysis process, whereas freely-diffusing homogeneous hydroxyl radical (•OH(free)) was the major reactive species in the UV-assisted BDD electrolysis process. Cyclic voltammetry revealed that UV light decomposed H2O2 formed on the BDD anode surface, thus retarding O2 evolution and facilitating •OH(free) generation. This work also explored the potential application of UV-assisted BDD electrolysis in removing COD from bio-pretreated landfill leachate containing high concentrations of hydrophilic aromatic pollutants. This study shed light on the importance of the existing state of •OH on removal of pollutants during BDD electrolysis, and provided a facile and efficient UV-assisted strategy for promoting degradation of hydrophilic aromatic pollutants.

The degradation mechanisms of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) by different chemical methods: A critical review

Per- and polyfluoroalkyl substances (PFASs) are a class of artificial compounds comprised of a perfluoroalkyl main chain and a terminal functional group. With them being applied in a wide range of applications, PFASs have drawn increasing regulatory attention and research interests on their reductions and treatments due to their harmful effects on environment and human beings. Among numerous studies, chemical treatments (e.g., photochemical, electrochemical, and thermal technologies) have been proved to be important methods to degradation PFASs. However, the pathways and mechanisms for the degradation of PFASs through these chemical methods still have not been well documented. This article therefore provides a comprehensive review on the degradation mechanisms of two important PFASs (perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)) with photochemical, electrochemical and thermal methods. Different decomposition mechanisms of PFOA and PFOS are reviewed and discussed. Overall, the degradation pathways of PFASs are associated closely with their head groups and chain lengths, and H/F exchange and chain shortening were found to be predominant degradation mechanisms. The clear study on the degradation mechanisms of PFOA and PFOS should be very useful for the complete degradation or mineralization of PFASs in the future.

Photocatalysts synthesized via plant mediated extracts for degradation of organic compounds: A review of formation mechanisms and application in wastewater treatment

Photocatalysis is a promising technology to remove several persistent and recalcitrant pollutants in water and wastewater. Most of the conventional chemical and physical synthesis routes of photocatalysts result in the release of toxic pollutants to the environment and hence green synthesis is a better alternative. Green synthesis of photocatalyst using plants, fungi, bacteria, yeast, and other biological sources is widely explored in recent years. The presence of various biomolecules used in green synthesis replaces conventional reducing and stabilizing agents such as hydrazine, sodium borohydride, ascorbic acids, and other polymer substitutes. This review focuses on the synthesis of photocatalysts using plant extracts through different synthesis routes and explores the efficacy of photocatalyst synthesized via plant extract mediated synthesis routes in the photodegradation of organic compounds present in water. The pathway as well as the factors affecting the formation of photocatalysts, the role of plant extract in the photocatalytic properties are explored in detail. The action of plant-mediated photocatalyst on the pollutant and the underlying predominant degradation mechanism are also discussed. Besides, this study gives an insight into the recyclability of the photocatalyst synthesized via plant extract mediated synthesis routes and addresses future perspectives and the challenges of green photocatalysts.

A Comparison of Lithium-Ion Cell Performance across Three Different Cell Formats

To investigate the influence of cell formats during a cell development programme, lithium-ion cells have been prepared in three different formats. Coin cells, single layer pouch cells, and stacked pouch cells gave a range of scales of almost three orders of magnitude. The cells used the same electrode coatings, electrolyte and separator. The performance of the different formats was compared in long term cycling tests and in measurements of resistance and discharge capacities at different rates. Some test results were common to all three formats. However, the stacked pouch cells had higher discharge capacities at higher rates. During cycling tests, there were indications of differences in the predominant degradation mechanism between the stacked cells and the other two cell formats. The stacked cells showed faster resistance increases, whereas the coin cells showed faster capacity loss. The difference in degradation mechanism can be linked to the different thermal and mechanical environments in the three cell formats. The correlation in the electrochemical performance between coin cells, single layer pouch cells, and stacked pouch cells shows that developments within a single cell format are likely to lead to improvements across all cell formats.

Ab-initio investigation of the effect of adsorbed salts on segregation of Cr at the Ni (100) surface

The dissolution and depletion of chromium (Cr) in salt facing nickel (Ni) alloy surfaces is one of the predominant degradation mechanisms of structural components in molten salt technology. In this work, we use density functional theory to investigate the role of electronic level interactions that may underlie the depletion phenomenon of Cr in a Ni 100 surface exposed to various adsorbed salt species. Our results show that, under vacuum, Ni preferentially segregates to the surface layer. Conversely, in the presence of adsorbed anionic salt species (e.g., chlorine (Cl), fluorine (F) or the impurity oxygen (O)) Cr segregation becomes more favorable. In these cases, Cl has the weakest effect on segregation, while O has the strongest effect. Our analysis reveals the strong correlation between Cr segregation and the amount of valence charge transferred between the Cr atom and surface adsorbate: the greater the charge transfer, the lower the segregation energy. We also show that, when considered, secondary cations screen Cr-anion interactions, which in turn reduce the magnitude of the anions effect on segregation. These results shed light on the role of salt impurities likely play in the overall corrosion phenomena in molten salt environments. This work provides insights into the atomic level interactions fundamental to molten salt corrosion and on the importance of maintaining salt purity.

Mechanisms and toxicity evaluation of the degradation of sulfamethoxazole by MPUV/PMS process

In this work, a sulfate radical (SO4-)-based advanced oxidation process was applied to the degradation of sulfamethoxazole (SMX). In these experiments, a medium pressure UV (MPUV) lamp was employed to active peroxymonosulfate (PMS). It was found that 98% of SMX was removed by MPUV/PMS at a UV dose of 200 mJ cm−2 (3.95 μM SMX, 0.2 mM PMS, pH0 = 3.7). Direct MPUV photolysis played a remarkable role in SMX removal by MPUV/PMS process. As for the indirect photolysis, SO4- was the major reactive species under acidic and neutral conditions in MPUV/PMS system, while the hydroxyl radical (OH) became the predominant radical under alkaline conditions. The transformation products (TPs) of SMX that formed in the MPUV-only and MPUV/PMS experiments were identified, and the possible degradation pathways were proposed. Photoisomerization of the isoxazole ring was the major pathway of SMX during MPUV-only process. Hydroxylation/oxidation of the aniline and isoxazole ring was the predominant degradation mechanism of SMX by MPUV/PMS. Toxicity evaluation showed that MPUV/PMS was effective at reducing the antibacterial activity of SMX solutions, while MPUV-only was not. However, some TPs with equivalent or even higher antibacterial activity than SMX were formed during the initial degradation period in MPUV/PMS system. Ecotoxicity of SMX and its TPs was also hypothetically predicted via the ECOSAR program, and the results indicated that some TPs could be more toxic than SMX.

Remaining Life Evaluation Based on Strain Deformation Monitoring

The operating conditions of a power plant affect its structural integrity due to many degradation mechanisms, among which is creep. Strain measurements constitute a relatively simple and reliable method of obtaining accurate data regarding the capability of engineering materials to withstand loads and of determining stress distribution in all manner of structural components. This work carried out a critical evaluation of the application of a high-temperature strain gage on a strain and stress analysis. The sensor was undergoing a group of long-term creep tests whose results were compared with the creep machine’s acquisition system. The same strain gage was part of a monitoring system and its out some used on the remaining life evaluation a power plant’s pipeline. The methodology consists of online strain monitoring of those components or regions more susceptible to creep failure, which were identified by finite element analysis. The long-term creep tests using high-temperature strain gages showed that the relative position between sensor and the sample necking region exercises great influence on the measured results. Linear relationship between minimum creep rate obtained by strain gages and rupture time values was observed. The power plant pipeline analysis showed that thermomechanical fatigue is the predominant degradation mechanism.

Degradation and metabolite formation of 17ß-estradiol-3-glucuronide and 17ß-estradiol-3-sulphate in river water and sediment

Laboratory degradation tests with two model estrogen conjugates, 17ß-estradiol-3-glucuronide (E2-3G) and 17ß-estradiol-3-sulphate (E2-3S), using river water and sediment as inoculum under aerobic conditions were investigated. Throughout the 14-day incubation, degradation of E2-3G in river water, at environmentally-relevant level (25 ng/L), obeyed first-order kinetics with the formation of 17-ß estradiol and estrone; in contrast, E2-3S was slowly converted to estrone-3-sulphate stoichiometrically. Degradation of the two conjugates across the spiking concentrations (0.01–1 μg/g) was much faster in sediment than in river water where 25 ng/L of conjugate standards were spiked, possibly due to relatively high population densities of microorganisms in sediment. De-conjugation of the thio-ester bond at C-3 position and oxidation at C-17 position were the predominant degradation mechanisms for E2-3G and E2-3S, respectively, with negligible presence of metabolites estrone-3-glucuronide for E2-3G and 17ß-estradiol for E2-3S. In addition, delta-9(11)-dehydroestrone and 6-ketoestrone were determined as new metabolites of the two conjugates. Also, a lactone compound, hydroxylated estrone and a few sulfate conjugates were tentatively identified. With the observation of new metabolites, biodegradation pathways of E2-3G and E2-3S were proposed. The formation of new metabolites may pose unknown risks to aquatic biota.

Characterization and wear of oxides formed on CoCrMoSi alloy coatings

CoCrMoSi alloys were developed for high-temperature use and their performance associated with the almost continuous Laves-phase network. The metallurgical stability of CoCrMoSi coatings exposed to high temperatures has been shown to be associated with the stability of the Laves phase. However, the successful development of coatings for high-temperature applications requires an understanding of their oxidation behavior and the role the oxide layer plays on their wear characteristics. The aim of the study was to assess the wear behavior of oxides formed on the surface of CoCrMoSi coatings. Exposure to 450°C and 750°C induced the formation of different oxides identified by Raman spectroscopy and X-ray diffraction. Abrasive wear tests were carried out with a rotating ball tester and low applied loads ranging from 0.2N to 0.45N. Confocal microscopy and scanning electron microscopy were used to characterize the wear scar. Exposure to 450°C induced the formation of Co3O4, Fe3O4 and Fe2O3 Their low adhesion to the coatings surface allows the removal of oxide particles that scratch the surface of coatings forming grooves. Exposure to 750°C resulted in a continuous Cr2O3 film, subsequent wear testing revealed rolling wear to be the predominant degradation mechanism. Comparison with as-deposited CoCrMoSi coatings wear results showed that the oxides formed at 450°C did not affect wear performance. In contrast, the continuous oxide film formed at 750°C has an increased wear resistance as is expected to postpone the on-set of wear in coatings.

FIB-SEM Tomography Connects Microstructure to Corrosion-Induced Performance Loss in PEMFC Cathodes

Extensive corrosion has been shown to result in collapse of the porous cathode microstructure in PEMFCs and has been presumed responsible for severe mass-transport voltage losses observed in polarization data. Corrosion of the carbon support was studied by electrochemical methods, non-dispersive infrared spectroscopy, and FIB-SEM tomography to evaluate the connected roles of carbon loss, microstructure, and performance degradation. In silico characterization of the three-dimensional, digital microstructures generated by FIB-SEM included porosity, Dijkstra tortuosity, and two-point correlation functions before and after corrosion. Carbon loss and H2/air operando performance decay were strongly correlated but contrary to expectation, the associated porosity loss and tortuosity gain did not explain the observed performance decay; cell failure occurred long before microstructural collapse was observed. Platinum catalyst ripening and preferential corrosion of the amorphous interior of carbon black primary particles were likely the two predominant degradation mechanisms induced among the cells tested. These results connect and clarify the roles of performance, microstructure, and corrosion degradation and demonstrate that microstructural collapse need not underlie cell failure.

Wear properties of Fe3Al-based HVOF coatings strengthened with in-situ precipitated nitride and boride particles

Abstract Iron aluminide coatings reinforced with in-situ precipitated TiN, TiB2 and Fe2B particles were synthesized from Fe3Al, BN and Ti powders using a combination of high-energy ball milling and high velocity oxy-fuel (HVOF) process. In the present work, we investigate the effect of the BN/Ti contents on the microstructure and characteristics of the HVOF coatings and we discuss their tribological properties. The microstructure and composition of powders and coatings were investigated using X-ray diffraction, differential thermal analysis and optical and scanning electron microscopies. The wear rate was evaluated by tribometry in a pin-on-disc configuration, and the mechanical properties were obtained using indentations. X-ray analysis of the coatings prepared from the as-milled powders revealed evidence of TiN, TiB2 and Fe2B peaks. The microhardness (4.3 GPa) and the wear resistance (3 × 10− 4 mm3/Nm) of the coating prepared from the pure Fe3Al powder were increased 3.3 times and by about three orders of magnitude, respectively, when 70 wt% of Fe3Al was milled with 10 wt% of BN and 20 wt% of Ti. Fatigue and abrasive wear were found to be the predominant degradation mechanisms during sliding against an alumina ball of the pure Fe3Al and composite HVOF coatings, respectively. Adhesive wear also contributed to the material loss as confirmed by EDS analysis that revealed a transfer of the coating material to the counterpart.

Thermal Cracking of Virgin and Waste Plastics of PP and LDPE in a Semibatch Reactor under Atmospheric Pressure

Study of the decomposition kinetics, pyrolysis products, and even reaction mechanisms plays an important role for the development of polymer recycling. In the present research, the kinetics of virgin and waste polypropylene (PP) and low-density polyethylene (LDPE) were studied by a modified Coats–Redfern method. Afterward, thermal cracking of them in a semibatch reactor under atmospheric pressure in nitrogen has been investigated. Both virgin and waste plastics are decomposed at 420–460 °C, and the products have been characterized using GC, FT-IR, 1H NMR, and GC-MS. The reaction path and the degradation mechanism for the thermal cracking of polymer in this study were also discussed. The lower activation energy of waste PP and LDPE indicates that waste plastics degrade at lower initial temperature and may favor mild conditions. Due to the short residence time, the higher gaseous and liquid yields were obtained for virgin PP and LDPE. A large amount of residues for waste polymer indicates that it is a favorable way to degrade waste plastics in a semibatch reactor without further separation. Chain scission reactions are the predominant degradation mechanism in this thermal cracking process. The significant content of unsaturated hydrocarbons in PP thermal cracking products shows the intramolecular hydrogen transfer and β-scission reactions are predominant. In the case of LDPE, intermolecular hydrogen transfer and β-disproportionate reactions also occur. For thermal cracking polymer in a semibatch reactor under atmospheric pressure, the high yields of gasoline (C6–C12) and diesel (C13–C22) fraction in liquid products confirm that it is a desirable way to realize waste plastics recovery.