Pyrolysis Of Resin Research Articles

Modeling the microwave transmittance of glass fiber-reinforced plastics subjected to laser ablation

The microwave transmittance of glass fiber-reinforced plastic (GFRP) slabs subjected to continuous-wave laser ablation was studied in the framework of continuum mechanics. First, a one-dimensional physical model involving laser absorption, heat conduction, resin pyrolysis, thermal radiation, and convection heat transfer was established to obtain the temperature field. An experiment-based absorption coefficient was proposed to capture the bulk-to-surface absorption transition during laser ablation. Second, the complex dielectric constant was modeled using a solid-state kinetic model describing the graphitization of pyrolysis products. The microwave reflectivity and transmittance were calculated based on the dielectric constant distribution. The agreement of the temperature and microwave transmittance with the experimental results suggests the feasibility of the model. The influence of laser power density, material thickness, and tangential airflow velocity on microwave transmittance was studied based on the model. The microwave transmittance changed nonmonotonically with increasing slab thickness owing to the competition between different physical mechanisms. The existence of tangential airflow reduced the decrease in microwave transmittance, particularly for weaker lasers. This study provides a useful physical model for predicting the microwave transmittance performance of GFRP in extreme heat environments.

High flame retardant and heat-resistance, low dielectric benzoxazine resin with phthalimide structure

In order to improve the thermal stability, flame retardancy and dielectric properties of benzoxazine resin, benzoxazine resins with different content of 4,4′-‍(hexafluoroisopropylidene) diphthalic dianhydride(m-EFDA) were prepared by crosslinking alkynyl groups. The results showed that benzoxazine can improve the processing window of m-EFDA, while m-EFDA was beneficial to improve the thermal stability and dielectric properties of benzoxazine resins. The Td5% of PBZFI-50 reached 418.2°C, Td10% was up to 457.3°C, Dk was 2.89 and Df was as low as 0.013 at 1MHz. The chemical structures of volatile products from the pyrolysis of benzoxazines resin at different temperatures were identified by TG-FTIR and Py-GC/MS, and the promoting effect of m-EFDA on improving the thermal stability was confirmed. Compared with pure benzoxazine resin, the resin containing m-EFDA has great performance improvement, which is expected to be used as high temperature and low dielectric material in aerospace and microelectronics field.

Fabrication and properties of SiCnw‐reinforced SiC composites by reactive melt infiltration with BN and PyC interface

AbstractTo tailor the fiber–matrix interface of SiC nanowires‐reinforced SiC (SiCnw/SiC) ceramic matrix composites (CMCs) for improved mechanical properties, SiC nanowires were coated with BN and pyrolytic carbon (PyC) compound coatings prepared by the dip‐coating process in boric acid and urea solution and the pyrolysis of phenolic resin. SiCnw/SiC CMC with PyC/BN interfaces were fabricated by reactive melt infiltration (RMI) at 1680°C for 1 h. The influences of phenolic resin content on the microstructure and mechanical properties of the CMC were investigated. The results showed that the flexural strength and fracture toughness reach the maximum values of 294 MPa and 4.74 MPa m1/2 as the phenolic resin content was 16 and 12 wt%, respectively. The displacement–load curve of the sample exhibited a gradient drop with increasing phenolic resin content up to 12 wt%. The results demonstrated that the PyC/BN compound coatings could play the role of protecting the SiCnw from degradation as well as improving the more moderate interfacial bonding strengths during the RMI.

Phase evolution of a novel silicon-alumina-fused mullite-containing Ti2O3 refractory at 1300 °C in N2

A novel silicon-alumina-fused mullite-containing Ti2O3 composite refractory is prepared and sintered in the presence of solid carbon at 1300 °C in N2. The sintered samples exhibit a functional gradient characteristic. The phase evolution can be described as follows: Passive and active oxidation of Si to form SiO2 and SiO to reduce the partial pressure of oxygen. SiO(g) and Si react with N2 to form Si3N4 respectively. As the temperature increases and the partial pressure of oxygen decreases, Ti2O3 reacts with CO and N2 to form Ti(C,N)ss, which is accompanied by the release of O2. Si3N4 fixes the O2 and reacts to form Si2N2O, and Si2N2O reacts with Al2O3 to form O′-Sialon, thereby realizing the transformation from Si3N4 to Sialon. CO and residual carbon from the pyrolysis of phenolic resin react with SiO(s) and Si to form SiC. The dense layer formed by SiC and SiO2 blocks the diffusion of external gas to the central parts of the samples, there is still free Si which can continue to react and transform into a non-oxide reinforcing phase. In this paper, the reaction models are presented.

ДОСЛІДЖЕННЯ СТІЙКОСТІ МОДИФІКОВАНИХ БІТУМІВ ДО ТЕХНОЛОГІЧНОГО СТАРІННЯ

A comparison of the ability of modifiers of different classes to slow down the aging processes occurring in petroleum bitumen during pavement operation is presented in the article. Oxidized and residual road bitumens were used as research objects. Determination of resistance to hardening under the influence of heat and air was performed by the RTFOT method. Samples of oxidized bitumen with the addition of petroleum polymer resins with hydroxyl functional groups and heavy pyrolysis resin were found to have the best resistance, while for residual bitumen the highest resistance was observed with the introduction of heavy pyrolysis resin and sulfur.

Prediction of the removal of aqueous phase during boiling of highly stable water-hydrocarbon emulsions

The removal of water from highly stable natural and technogenic water-hydrocarbon emulsions is studied. For various crudes (oil waste blends, pyrolysis resin emulsion, lake oil sludge, intermediate oil layer) dehydration end temperatures, leading to complete stabilized evaporation of water without foaming, are defined (water content is less than 1% wt.). The end dehydration temperature varies within a wide range (109-150 °C). The parameters of hydrocarbon phase, which indirectly reflect the stability to removal of water by evaporation during thermomechanical dehydration and help to predict final dehydration temperature, such as, density, coking capacity, pour point and viscosity, are suggested.

Catalytic preparation of carbon nanotube/SiC whisker bonded low carbon MgO–C refractories and their high-temperature mechanical properties

The effects of Co, Fe and Ni catalysts generated from their nitrate precursors on the formation of carbon nanotubes (CNTs) from pyrolysis of phenolic resin were investigated, and the former two performed the best at 873 K, and 1073–1273 K, respectively. Density functional theory calculations indicate that a Co nanocluster requires the lowest energy for forming the five-membered carbon ring (the controlling step in the CNT generation), making Co the best catalyst for the formation of CNTs at relatively low temperatures. On the other hand, molecular dynamics calculations show that an Fe nanocluster has the highest melting point among the three nanoclusters and can retain its integrity at 1280 K, making Fe the best catalyst for the formation of CNTs at relatively high temperatures. Hot modulus of rupture of the CNT (along with additionally formed SiC whisker) reinforced low-carbon MgO–C refractory sample containing 0.25 wt% Fe catalyst was about 20% higher than that of its catalyst-free counterpart.

Reducing down-cycling of carbon fibre by fibre architecture preservation: Multi-layer fibre surface quality investigation

Carbon fibre has a high mechanical reinforcement capability associated with fibre architectures. However, it is significantly down-cycled in the current recycling practice as a result of a loss of fibre architecture. Without the use of chopping/shredding process, the architecture of carbon fibre can be preserved, but the surface cleanliness of recycled carbon fibre (rCF) is not clear. In this study, an investigation is carried out on the surface quality of architecture-preserved rCF obtained from multiple layers of a carbon fibre reinforced polymer (CFRP). Carbon fibre woven fabrics are manufactured into CFRP, recycled using a pyrolysis technique, and inspected using visual and microscopic techniques. The results indicate a good preservation of fibre architecture in all five layers of CFRP. Nonetheless, the residue from the pyrolysis of resin is increased in the internal layers (4th and 5th) of rCF in comparison to the external layers (1st to 3rd). The results suggest that fibre architecture preservation has a potential to reduce the down-cycling of carbon fibre, but the impact is limited in internal fibre layers due to reduced fibre surface cleanliness. The insights from this study provide a further understanding on the approach to reduce the down-cycling of carbon fibre and move the carbon fibre industry towards circular economy.

High-value-added reutilization of resin pyrolytic oil: Pyrolysis process, oil detailed composition, and properties of pyrolytic oil-based composites

Although numerous efforts have been focused on the high-value-added reutilization of resin matrix in abandoned composites, the evidence chain of whether high-value-added resin pyrolysis oil can be reused has not been comprehensively presented. Herein, the epoxy resin (EP) matrix in composite wastes was pyrolyzed into EP pyrolytic oil (EPO), and its detailed composition and effects on the microstructure, strength, and ablation of remanufactured carbon fiber (CF) composites were analyzed and evaluated. According to the results, more than half (57.8 wt%) of the EP matrix was converted into EPO, which mainly included phenol and its derivatives. Given that EPO contains a certain amount of phenol derivatives, the viscosity and wettability of EPO-formaldehyde (EPOF) prepolymer with CF was slightly poorer than that of industrial grade phenol formaldehyde (PF). In addition, CF reinforced EPOF (CF/EPOF) composites with strengths and ablation rates comparable to those of CF/PF composites were fabricated successfully, owing to good process performance of the EPOF prepolymer. The present work provides a comprehensive feasibility data support and basis for high-value-added reutilization of an abandoned resin matrix composite for the manufacture of composites.

Molecular Dynamics Simulation of Cracking Process of Bisphenol F Epoxy Resin under High-Energy Particle Impact.

The current lead insulation of high-temperature superconductivity equipment is under the combined action of large temperature gradient field and strong electric field. Compared with a uniform temperature field, its electric field distortion is more serious, and it is easy to induce surface discharge to generate high-energy particles, destroy the insulation surface structure and accelerate insulation degradation. In this paper, the degradation reaction process of bisphenol F epoxy resin under the impact of high-energy particles, such as O3−, HO–, H3O+ and NO+, is calculated based on ReaxFF simulation. According to the different types of high-energy particles under different voltage polarities, the micro-degradation mechanism, pyrolysis degree and pyrolysis products of epoxy resin are analyzed. The results show that in addition to the chemical reaction of high-energy particles with epoxy resin, their kinetic energy will also destroy the molecular structure of the material, causing the cross-linked epoxy resin to pyrolyze, and the impact of positive particles has a more obvious impact on the pyrolysis of epoxy resin.

Decomposition of carbon/phenolic composites for aerospace heatshields: Detailed speciation of phenolic resin pyrolysis products

Thermal Protection Materials (TPM) such as carbon/phenolic composites are used to protect spacecraft structures from extreme conditions. This protection is, in part, achieved by the decomposition via pyrolysis of the phenolic resin. Finite rate chemistry models are however still unable to predict the chemical production rates and composition of the pyrolysis products accurately. This is mostly due to the scarcity of experimental data for model validation. In this work, the decomposition of a phenolic material representative of thermal protection material is studied in a unique micro-pyrolysis unit for the temperature range 300-800°C. This unit is equipped with highly sensitive detectors allowing us to identify and quantify products in a broad range of molecular weights up to 240 gmol−1. More than 50 different products of the pyrolysis of phenolic resin have been quantified with a mass balance closure greater than 80%. The major compound groups found are permanent gases, phenols as well as larger molecules such as diphenols and naphthalenes. In addition, the char yield obtained at the fast heating rates employed in our apparatus was found ∼5%-points lower compared to traditional thermogravimetry.

Experimental Research and Simulation Analysis of Lightning Ablation Damage Characteristics of Megawatt Wind Turbine Blades

In this paper, the damage mechanism of glass fiber reinforced composite (GFRC) under lightning strike by laying and inserting copper wires in the laminate was studied. The ablation characteristics of GFRC under different lightning current components were explored. Scanning electron microscope (SEM) was used to conduct the morphology analysis at the damaged area. The results show that the high temperature induced by lightning striking leads to resin pyrolysis, glass fiber (GF) sublimation, and stress waves, which results in fiber breakage and delamination. Then, a finite element (FE) thermal-electric coupling model for predicting the lightning ablation damage of GFRC was established. The comparison between the simulation and experimental results are in good agreement, which validate the effectiveness of the proposed FE model. The relationship between the lightning ablation area and the lightning current amplitude, charge amount, and specific energy in creeping discharge and through discharge was obtained by data fitting. The whole ablation damage process was revealed by FE simulation.

Investigation of the Dependence of the Softening Temperature on the Content of Mesophase in Petroleum Pitches Obtained from Heavy Pyrolysis Resin and Decant Oil

Investigation of the Dependence of the Softening Temperature on the Content of Mesophase in Petroleum Pitches Obtained from Heavy Pyrolysis Resin and Decant Oil

Elucidating multiple-scale reaction behaviors of phenolic resin pyrolysis via TG-FTIR and ReaxFF molecular dynamics simulations

Phenolic resin is a matrix material widely used in ablative thermal protection systems (TPS) and its pyrolysis behavior is crucial for the analysis and prediction of TPS thermal response. However, it still remains a huge challenge to elucidate the involved reaction mechanisms due to the process complexity and unpredictability. Herein, a combination of TG-FTIR and ReaxFF MD simulation method was adapted to explore phenolic resin pyrolysis mechanism. Experiment results indicate that the pyrolysis process of phenolic resin can be divided into three stages, and the activation energy of each stage increases gradually. Heating rate affects the initial pyrolysis temperature of phenolic resin, but has no obvious effect on the types of pyrolysis products. Additionally, an accurate and reasonable decomposition kinetic model is established based on 30 kinds of kinetic function models, involving diffusion, random nucleation and nuclei growth, phase interface reaction and chemical reaction. The cook-off simulations results suggest that the major pyrolysis products of phenolic resin at high temperature include H2, CO, C2H2, and H2O, which formation mechanisms are also discussed according to the simulation trajectories. The reaction model and the activation energy of phenolic resin pyrolysis based on simulations are in good agreement with the experimental results, contributing to the deep understanding of phenolic resin pyrolysis behaviors at atom scale. This study may provide theoretical data basis for the establishment of thermal response calculation model of resin-based composite thermal protection materials.

Kinetic analysis and reaction mechanism of p-alkoxybenzyl alcohol ([4-(hydroxymethyl)phenoxymethyl]polystyrene) resin pyrolysis: Revealing new information on thermal stability

This study provides new information on the thermal stability and kinetics of pyrolysis of commonly used resins in solid-phase peptide synthesis. Pyrolysis process of 4-benzyloxybenzyl alcohol resin was monitored by simultaneous TGA-DTG measurements in a nitrogen atmosphere, at four different heating rates (5, 10, 20 and 30 K min−1). Kinetic computations included the model-free (isoconversional) and model-based methods for reliable estimation of kinetic parameters and the mechanism of investigated process. Based on the findings from applied methods, the pyrolysis process can be described by three reaction steps, where one of them encompasses the consecutive reactions. The first step (n-th order reaction, referred to Fn) is attributed to the random scission of the main chain in PS (polystyrene) solid support, where polymer radicals were formed. The second step proceeds through homolytic cleavage path of ether linkage of the resin (by the first-order reaction, referred to F1) and then via phenoxy radical (semiquinone) formation which is converted into the benzoquinone through a dehydrogenation (by autocatalysis reaction, referred to Cnm). Finally, the third step (referred to Fn reaction) was characterized by depolymerization mechanism, which takes place at higher temperatures (T > 385 °C). With determined kinetic parameters and the most probable mechanism functions, the model agrees excellently with experimental data. By applying the obtained kinetic results, isothermal life-time prediction was also performed.

Mechanical Properties of Al Matrix Composite Enhanced by In Situ Formed SiC, MgAl2O4, and MgO via Casting Process.

Al matrix composite, reinforced with the in situ synthesized 3C–SiC, MgAl2O4, and MgO grains, was produced via the casting process using phenolic resin pyrolysis products in flash mode. The contents and microstructure of the composites’ fracture characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties were tested by universal testing machine. Owing to the strong propulsion formed in turbulent flow in the pyrolysis process, nano-ceramic grains were formed in the resin pyrolysis process and simultaneously were homogeneously scattered in the alloy matrix. Thermodynamic calculation supported that the gas products, as carbon and oxygen sources, had a different chemical activity on in situ growth. In addition, ceramic (3C–SiC, MgAl2O4, and MgO) grains have discrepant contents. Resin pyrolysis in the molten alloy decreased oxide slag but increased pores in the alloy matrix. Tensile strength (142.6 ± 3.5 MPa) had no change due to the cooperative action of increased pores and fine grains; the bending and compression strength was increasing under increased contents of ceramic grains; the maximum bending strength was 378.2 MPa in 1.5% resin-added samples; and the maximum compression strength was 299.4 MPa. Lath-shaped Si was the primary effect factor of mechanical properties. The failure mechanism was controlled by transcrystalline rupture mechanism. We explain that the effects of the ceramic grains formed in the hot process at the condition of the resin exist in mold or other accessory materials. Meanwhile, a novel ceramic-reinforced Al matrix was provided. The organic gas was an excellent source of carbon, nitrogen, and oxygen to in situ ceramic grains in Al alloy.

A comprehensive study on the oxidative pyrolysis of epoxy resin from fiber/epoxy composites: Product characteristics and kinetics

Thermal treatment has been the most feasible process to recycle valuable carbon fibers and obtain fuel and chemicals from waste fiber/epoxy composites. The present work studied the oxidative pyrolysis behaviors of epoxy resin from fiber/epoxy composites using a thermogravimetric apparatus and a fixed-bed reactor, respectively. The effects of various O2 concentrations on the thermal behaviors of epoxy resin were investigated and the product characteristics were analyzed. Furthermore, a multi distributed activation energy model (multi-DAEM) was first developed to determine the oxidative pyrolysis kinetics of epoxy resin under various atmospheres. Results showed that the degradation behaviors of epoxy resin were largely altered by the O2 concentrations. High O2 concentrations accelerated the primary decomposition of epoxy resin and shifted the oxidation of resin residue into lower temperatures. High contents of methylcyclohexene and phenolic derivatives were detected in liquid products. In air atmosphere, high yields of CO and CO2 were generated and distributed in several stages. The kinetic analysis indicated that the multi-DAEM method can well explain the oxidative pyrolysis behaviors of epoxy resin. A minimum six-reaction fitting process can perfectly simulate the oxidative pyrolysis of epoxy resin. The predictions for various O2 concentrations were in good agreement with the experimental tests.

Исследование разделения древесной смолы на органические фракции на основе индивидуального выкипания веществ

Pyrogenic gums of walnut shells are raw materials for various commercial products, for example, phenols. In the process of pyrolysis, valuable organic products are formed: volatile gases — 33.5%, liquid substances (organic substances) — 35% and charcoal — 31.4%. In this work, we studied the chemical composition of the fraction of the pyrolysis resin of walnut shells using a TKP-160 Cr-MIUKhL thermostat using a refrigerator. In the resin reactor, the following products were separated: light, phenolic, naphthalene, absorbent, anthrocene and pitch. It has been established that the separated organic fractions depend on the individual boiling off of substances.

Исследование зависимости температуры размягчения от содержания мезофазы в нефтяных пеках, полученных из тяжелой пиролизной смолы и декантойля

Samples of petroleum pitches were obtained from heavy pyrolysis resin and decantoil (heavy gas-oil of catalytic cracking) by thermal polycondensation at atmospheric pressure, temperatures of 380–400 and 410–440°С (for resin and decantoil, respectively) and isothermal holding time of 30–480 min. Analysis of the dependence of the softening point on the mesophase content for the obtained samples showed that at the same mesophase content, decantoil pitches exhibit a lower softening point compared to pyrolysis resin pitches, for which, even at 30 % mesophase, the softening point approaches 300°C. This suggests that it is impossible to obtain pitch from pyrolysis resin with high mesophase content without preliminary preparation (for example, by hydrogenation). On the other hand, it has been shown that for pitches from decantoil, it is possible to isolate the mesophase up to 65% or more with a softening point not higher than 250°C.

Процесс термополиконденсации и производство нефтяного пека

The article discusses the methods of obtaining petroleum pitch of thermal polycondensation. The main attention is paid to the characteristics of petroleum pitch, its properties, its comparison with coal-tar pitch, the advantages of petroleum pitch in comparison to coal-tar pitch, the processes of production of petroleum pitch by thermal polycondensation are given. Three promising technologies for the production of petroleum pitch have been identified: thermal polycondensation of cracking residue, high-temperature thermal polycondensation of petroleum feedstock and thermal polycondensation of pyrolysis resin according to a two-stage scheme. Methods of obtaining petroleum pitch in laboratory conditions, such as thermal polycondensation under pressure and heat treatment under reduced pressure, are presented. The urgency and feasibility of developments for the creation of petroleum pitch and the introduction of thermopoly-condensation processes in Russia is emphasized.