Changes In Molecular Structure Research Articles

Effect of sheeting stress and heating on the molecular chain structure, size, and conformation of gluten proteins during noodle processing

In this paper, the changes in molecular structure, size distribution, and conformation of gluten induced by the mechanical stress during sheeting and the heating effect during cooking of noodles were investigated by atomic force microscopy (AFM), X-ray scattering (SAXS), and size-exclusion chromatography multi-angle laser light scattering (SEC-MALLS). AFM results showed that the height and width of gluten molecular chains were decreased after calendering and increased post-cooking. Calendering reduced the molecular size and compacted the gluten network (increased Dm). The SDS extractable gluten components showed a quasi-spherical chain conformation but gradually changed to a random coil conformation due to heating. According to SEC-MALLS profiles, calendering and appropriate heating (4 min) promoted the homogeneity of molecular mass of glutenin polymer. The mechanical depolymerization and the heat-promoted polymerization of gluten could be due to the breakage and formation of disulfide bonds and the interconversion of sulfhydryl groups.

Exploring thermal isomerisation in gas chromatography analyses using natural pyrethrins: Comparison of comprehensive two-dimensional and one-dimensional gas chromatography

This study aims to assess and qualitatively compare the visual presentation of chromatographic data from the isomerisation of natural pyrethrins – a group of pesticides derived from Chrysanthemum flowers – using one-dimensional gas chromatography (1DGC) and comprehensive two-dimensional gas chromatography (GC×GC). Molecular structural changes, such as thermal isomerisation in this case, occur during gas chromatography injection and separation, to provide characteristic patterns which may not be routinely recognised on the 1D chromatogram. To demonstrate the influence of analytical method parameters on isomerisation processes, variations in oven temperature (isothermal vs. temperature programmed analysis), inlet mode (split vs. splitless), inlet temperature, and carrier gas flow rate were investigated. Increasing oven temperature was the most significant factor affecting isomerisation. Splitless injection mode and increasing inlet temperature promoted isopyrethrin formation, while the effect of inlet temperature appeared minimal with a split injection technique, most likely due to the short residence time in the inlet. Increased carrier gas flow rates in a temperature programmed analysis reduced retention time and minimised isomerisation. The unique presentation of isopyrethrin peaks on a GC×GC contour plot allows for facile recognition of isomerisation especially at low concentrations, simplifies chromatogram interpretation, and aids in analyte identification. It also confirms that the isomerisation process is irreversible since the pyrethrin I and II compounds are absent throughout the bridge formation. These benefits support the use of GC×GC over 1DGC to study isomerisation. Additionally, due to limited data in the literature, Kováts retention indices and linear retention indices of the natural pyrethrins, including isopyrethrins, were experimentally determined on four columns: DB-5 ms UI, Rxi-17Sil MS, SLB-IL60i, and SLB-IL111i.

Changes in Molecular Structure of Humic Substances in Cambisols under Agricultural Use

Soil organic matter stability and transformation affected by agriculture is a global problem of great concern. This study aimed to reveal structural changes in humic molecules under conventional soil tillage in Cambisols of the Transbaikal area. Humic acids were isolated from the humus horizons of native and arable variants of Eutric Cambisol Cryic (gleyic, humic, loamic) from the forest steppe, and Haplic Cambisol (arenic, humic, protocalcic) from the steppe zone. The changes in the humic substances’ quality were evaluated by means of an elemental analysis and 13C nuclear magnetic resonance spectroscopy. The results indicate that different agronomic management affected the changes in the composition and molecular structure of humic acids. Soil tillage induced an increase in the carbon content, the proportion of aromatic compounds and carboxyl groups and the depletion in nitrogen. As measured by 13C NMR spectroscopy, the intensity of these changes was determined by soil properties and the hydrothermal regime. Organic matter from Eutric Cambisol Cryic was suggested as providing significant environmental resistance to the agricultural impact due to the optimization of the water regime and a loamy texture. Prolonged ploughing of sandy Haplic Cambisol under the arid conditions promoted deep changes in the humic substances’ composition and chemical structure.

Evolution mechanism of the low-carbon MgO-based alkali-activated system under different heat-treatment conditions

Magnesium silicate hydrate (M-S-H) gel is the main product of MgO-based alkali-activated system (MAAS). The molecular structure and phase changes of M-S-H gel at different temperatures were characterised. The results showed that the initial MgO:SiO2 affected the Mg:Si ratio and the binding water content of M-S-H gel. With the decrease of Mg:Si ratio, the proportion of structural water in the gel decreases. Compared with structured water, the change of free water can more accurately characterise the content of M-S-H gel in the system. Below 600°C, the molecular structure and phase composition are relatively stable. When the temperature reached 1000°C, M-S-H gel transfers from amorphous phase to crystallized phase. The study characterised the evolution of MASS under different heat treatment conditions.

Analysis of Molecular Structure Changes in Humic Acids from Manure-Amended Soils over 17 Years Using Elemental Analysis and Solid-State 13C Nuclear Magnetic Resonance Spectroscopy

Soil organic matter (SOM) plays an important role in regulating plant nutrient availability. Here, the effects of the long-term application of different forms of processed swine manure on the SOM structure are explored through the analysis of humic acid (HA) using elemental analysis and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. The HAs from soils amended with liquid swine manure (LSM) and swine manure compost (SMC) are found to be more humified compared to the soils treated with solid swine manure (SSM) and the control (CK). The H/C and O/C molar ratios suggest that carboxyl-rich aliphatic structures are the most important class of biomolecules contributing to the LSM- and SMC-HA structures, while lignin-like structures are the most important biomolecules contributing to the CK- and SSM-HAs. SSM promoted the formation of aliphatic polar structures, which are more susceptible to aerobic biodegradation, whereas the CK facilitated the inclusion of condensed aromatic structures into the HA. Apart from the LSM-HA, the proportion of carboxylic acid functional groups reduced with manure application, while the proportion of phenolic acid functional groups increased. LSM-HA has the highest potential to enhance plant nutrient availability.

Molecular insights on influence of CO2 on CH4 adsorption and diffusion behaviour in coal under ultrasonic excitation

Decoupling the molecular structure from the pore structure is challenging under experimental conditions; this hinders the independent investigation of the effect of the changes in molecular structure on methane (CH4) transport. In this study, the molecular model of coal was reconstructed based on the test results of X-ray photoelectron spectroscopy (XPS) and 13C nuclear magnetic resonance (13C NMR). A grand canonical Monte Carlo (GCMC) based molecular dynamics (MD) simulation method was used to independently investigate the effect of CO2 on CH4 adsorption and diffusion behaviour in coal under changes in the molecular structure of coal after ultrasonic excitation. The experimental results show that, under ultrasonic excitation, the proportion of oxygen content in the coal increases and the oxygen-containing functional groups (carboxyl groups, ether bonds/hydroxyl groups) increase compared to the original coal. The simulation results show that the amount of CH4 adsorbed, the isosteric heat and the proportion of low-energy CH4 in the coal sample decrease after ultrasonic excitation for the same pore size. Furthermore, for the same pore size and CO2 partial pressure ratio, adsorption selectivity factor increases after ultrasonic treatment. Additionally, for the same pore size and the same CO2 partial pressure ratio, the interaction energy between CH4 and coal in the CH4–CO2–coal mixed system decreases and the density of high-energy CH4 increases after ultrasonic excitation; this leads to an increase in CH4 self-diffusion and transport diffusion coefficient. The presence of oxygen-containing functional groups causes a significant increase in the electrostatic potential difference between CO2 and coal as compared to that between CH4 and coal, which is the fundamental reason for the change in the effect of CO2 on the adsorption-diffusion behaviours of CH4. Our findings revealed the micro-mechanism of ultrasonic-assisted coalbed methane extraction and demonstrated the effectiveness of ultrasonic-CO2 collaborative technology.

Impact of processing methods (dry-heating, autoclaving, and (microwave irradiation) on protein-related molecular structure spectral feature and protein nutritive value of cool-seasoned oat varieties in ruminant system in western Canada

The objectives of this study were to reveal the effects of heating method and variety on (1) protein molecular structure spectral features revealed by Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and (2) ruminant relevant protein chemical profiles, protein subfractions, rumen degradable protein (RDP), rumen undegradable protein (RUP), and intestinal protein digestibility using the Cornell Net Carbohydrate and Protein System (CNCPS) in oat varieties [CDC Nasser (feed-type oat) and CDC Seabiscuit (milling-type oat)]. Heating method included control (raw), dry heating (DH), moist heating (autoclaving, MH), and microwave irradiation (MIR). The dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF) contents in CDC Nasser were 934, 107, and 252 g/kg DM, respectively; the contents of these nutrients in CDC Seabiscuit were 933, 110, and 268 g/kg DM, respectively. Heat processing significantly affected the total RDP (TRDP, P < 0.001), which was higher for DH than MIR and MH in CDC Nasser (5.46%, 5.01%, and 4.45%DM). Conversely, MIR had a higher value for TRDP than DH and MH in CDC Seabiscuit (5.32%, 5.24%, and 4.51%DM). The total RUP (TRUP) was higher for MH than MIR and DH in both varieties (P < 0.001). The intestinal digestible feed protein was similar between the varieties (P = 0.308); however, DH and MH reduced the value, while MIR increased it compared to the control (P = 0.010) for both varieties. The results from the ATR-FTIR analysis showed an interaction between varieties and heat processing in the protein secondary structures α-helix (P = 0.003), β-sheet (P = 0.031), and their ratio (P = 0.030). Moreover, in the multivariate analyses, no independent groups were observed between the raw and the three heat processing methods in the protein-related molecular structure of oats. In conclusion, heat processing altered the protein subfractions, the TRDP, and TRUP, affecting intestinal protein digestibility. The ATR-FTIR spectroscopy with univariate molecular analysis showed heat processing-induced molecular structure changes in the protein-related spectral profiles in CDC Nasser and CDC Seabiscuit.

Effect of Anaerobic Calcium Oxide Alkalization on the Carbohydrate Molecular Structures, Chemical Profiles, and Ruminal Degradability of Rape Straw.

To improve the utilization efficiency of rape straw, anaerobic calcium oxide (CaO) alkalization was conducted, and advanced molecular spectroscopy was applied, to detect the internal molecular structural changes. Rape straw was treated with different combinations of CaO (3%, 5%, and 7%) and moisture levels (50% and 60%) and stored under anaerobic conditions. We investigated the carbohydrate chemical constituents, the ruminal neutral detergent fiber (aNDF) and acid detergent fiber (ADF) degradation kinetics, and the carbohydrate molecular structural features. CaO-treated groups were higher (p < 0.05) for ash, Ca, non-fiber carbohydrate, soluble fiber, and the ruminal degradability of aNDF and ADF. In contrast, they were lower (p < 0.05) for the contents of aNDF, ADF, and indigestible fiber. With CaO levels rising from 3% to 7%, the content of aNDF and ADF linearly decreased (p < 0.05). CaO treatment and anaerobic storage changed the molecular characteristics, including structural parameters related to total carbohydrates (TC), cellulosic compounds (CEC), and structural carbohydrates (STC). Alterations in cellulosic compounds' spectral regions were highly correlated with the differences in carbohydrate chemical constituents and the ruminal digestibility of rape straw. In summary, CaO treatment and anaerobic storage altered the molecular structural parameters of carbohydrates, leading to an enhancement in the effective degradability (ED) of aNDF and ADF in rape straw. From the perspective of processing cost and effectiveness, 5% CaO + 60% moisture could be suggested as a recommended treatment combination.

Hydraulic properties of bentonite buffer material beyond 100 °C

Bentonite buffer materials are important components of engineered barrier systems for the disposal of high-level radioactive waste produced during nuclear power generation. The design temperature of the buffer material is < 100 °C, and increasing the design temperature can reduce the required disposal area. This characteristic necessitates the evaluation of the thermal–hydraulic–mechanical properties of the buffer at temperatures above 100 °C to increase its target temperature. Therefore, the hydraulic properties of Gyeongju (KJ) bentonite buffer material were evaluated in this study, including the soil–water characteristic curve (SWCC) and hydraulic conductivity. An experimental system was manufactured to measure the suction and saturated hydraulic conductivity of KJ bentonite buffer material above 100 °C; the relative humidity of KJ bentonite buffer material was measured at 25–149 °C with an initial water content of 0, 0.06, and 0.12 under constant saturation conditions. The suction decreased as the temperature increased (10%–25% reduction at 99 °C-149 °C). The Van-Genuchten SWCC fitting parameters were also derived at 25 °C-149 °C using previously reported and newly generated experimental results, and the applicability of the modified Van-Genuchten SWCC model in this temperature range was verified. The hydraulic conductivity was proportional to temperature up to 100 °C, in agreement with the theoretical model results. Between 100 °C and 150 °C, the hydraulic conductivity increased nonlinearly because of molecular motion and structural changes inside the sample.

Impact of Electrostatic Interaction on Non-radiative Recombination Energy Losses in Organic Solar Cells Based on Asymmetric Acceptors.

Reducing non-radiative recombination energy loss (ΔE3 ) is one key to boosting the efficiency of organic solar cells. Although the recent studies have indicated that the Y-series asymmetric acceptors-based devices featured relatively low ΔE3 , the understanding of the energy loss mechanism derived from molecular structure change is still lagging behind. Herein, two asymmetric acceptors named BTP-Cl and BTP-2Cl with different terminals were synthesized to make a clear comparative study with the symmetric acceptor BTP-0Cl. Our results suggest that asymmetric acceptors exhibit a larger difference of electrostatic potential (ESP) in terminals and semi-molecular dipole moment, which contributes to form a stronger π-π interaction. Besides, the experimental and theoretical studies reveal that a lower ESP-induced intermolecular interaction can reduce the distribution of PM6 near the interface to enhance the built-in potential and decrease the charge transfer state ratio for asymmetric acceptors. Therefore, the devices achieve a higher exciton dissociation efficiency and lower ΔE3 . This work establishes a structure-performance relationship and provides a new perspective to understand the state-of-the-art asymmetric acceptors.

Impact of Electrostatic Interaction on Non‐radiative Recombination Energy Losses in Organic Solar Cells Based on Asymmetric Acceptors

AbstractReducing non‐radiative recombination energy loss (ΔE3) is one key to boosting the efficiency of organic solar cells. Although the recent studies have indicated that the Y‐series asymmetric acceptors‐based devices featured relatively low ΔE3, the understanding of the energy loss mechanism derived from molecular structure change is still lagging behind. Herein, two asymmetric acceptors named BTP‐Cl and BTP‐2Cl with different terminals were synthesized to make a clear comparative study with the symmetric acceptor BTP‐0Cl. Our results suggest that asymmetric acceptors exhibit a larger difference of electrostatic potential (ESP) in terminals and semi‐molecular dipole moment, which contributes to form a stronger π–π interaction. Besides, the experimental and theoretical studies reveal that a lower ESP‐induced intermolecular interaction can reduce the distribution of PM6 near the interface to enhance the built‐in potential and decrease the charge transfer state ratio for asymmetric acceptors. Therefore, the devices achieve a higher exciton dissociation efficiency and lower ΔE3. This work establishes a structure‐performance relationship and provides a new perspective to understand the state‐of‐the‐art asymmetric acceptors.

Understanding the effects of dry heat treatment on wheat flour pasting: Insights from protein and starch structural changes

This study aimed to investigate the impact of heat treatment on the molecular structure of starch and protein in wheat flour and to establish a correlation between the changes in molecular structure and the resulting effects on the pasting properties of the flour. Heat treatment increased the pasting viscosity and pasting temperature with the extent of heat-treated time and temperature. Moreover, the water absorption indexes, swelling power, and gelatinization enthalpy of heat-treated flour were higher than that of untreated flour, while the water solubility indexes were lower. The clustered starch granules and aggregated protein increased the particle size of flour after heat treatment. Additionally, heat treatment decreased the damaged starch content from 6.54% in native flour to 2.94% in treated flour (100 °C, 30 min), causing an increase in the short-range order structure and relative crystallinity of starch. The aggregated protein induced by heat owned the lower free sulfhydryl content and higher SDS-insoluble protein and β-sheet structure. The pasting properties variations were mainly correlated with the molecular structure changes of protein induced by heat. These results provided a theoretical basis for tailoring flour to produce wheat-based products with desired properties through the application of heat treatment technology.

Shear and temperature sensitivity of a shear-thickening biopolymer from the New Zealand black tree fern

Mamaku polysaccharide (MP) is a water-soluble shear-thickening biopolymer that has shown potential to be used in the design of novel food products targeting satiety management and weight loss. During the processing of MP at industrial scale, the polymer may be exposed to high temperature and shear, which could affect its rheological behaviour. Thus, herein we subjected extracted MP to high shear (between 1000–8000 rpm at various times, using a lab-scale high-shear mixer) and temperature treatment (between 65 and 115 °C, for 30 min) and investigated the changes in molecular structure and rheological properties. The temperature treatment disintegrated the backbone of MP into smaller fragments (molecular weight-Mw, reduced from ∼3.9 × 106 Da with no heat, to ∼0.6 × 106 Da at 115 °C), which caused a reduction in viscosity and in the extent of shear-thickening as well as an increase in the damping factor (Gʹʹ/Gʹ). Similar rheological trends were observed post-shear treatment, however, there was no evidence of depolymerisation, with the Mw, constituent sugar composition and NMR spectra (1H and 13C) being unaffected. It is suggested that the changes in rheological behaviour after shear treatment could be due to changes in the re-arrangement of MP molecules, which led to a compact and folded structure due to increased intra-molecular interactions. The results, therefore, indicate that modification of MP molecules during the industrial process such as shearing and heating should be considered as it may adversely affect the rheological properties of the product where MP is incorporated and the expected physiological benefits in the gastrointestinal tract.

Regioselectivity of CH activation in cytochrome P450‐catalyzed intramolecular cyclization of alkylamine compounds

AbstractThe reaction mechanism of cytochrome P450‐mediated intramolecular cyclization of 2‐aminoamide compounds to imidazolinone was studied by density functional theory. The cyclization reaction involves three steps: hydrogen abstraction, dehydration of intermediates to zwitterions and final ring closure. Interestingly, high spin (HS) state P450‐catalyzed dehydration exhibits a mechanism distinct from conventional processes such as in low spin state. In HS pathways, the hydroxyl group after hydrogen abstraction does not rebound but produce an intermediate, which makes the second hydrogen abstraction regioselective. Regioselectivity leads to diverse intermediates and mechanisms to zwitterion, which implies different functions of the high and low spin states P450. The alkylamine nitrogen and amide group are key groups to enables regioselectivity of in HS pathway. Small changes of molecular structure can affect the molecular transformation process, indicating the complex regulation of electronic state to reaction process. The results lay the theoretical basis for the regioselectivity determined by P450 enzyme and substrate structure together. The research establishes a foundation for the drug design, drug metabolite, and synthesis of nitrogen‐containing heterocyclic drugs.

Probing the kinetics of chemical reactions in ultra-small droplet samples using digital microfluidic nuclear magnetic resonance spectroscopy

In this study, we present a digital microfluidic (DMF) system that connects analyte droplets with planar microcoils in a high-field nuclear magnetic resonance (NMR) spectrometer for in situ photoreaction analysis. Transparent indium tin oxide glass was employed in fabricating the DMF electrode chips. NMR spectroscopy was utilized for its superior sensitivity and ability to detect small changes in molecular structure, making it highly advantageous for chemical analysis. Utilizing Computer Simulation Technology Studio Suite, we designed a plane annular microstrip coil that accurately matches droplet shape to optimize detection sensitivity and increase filling factor. An advanced DMF control circuit remotely manages droplet samples and facilitates precise mixing for in situ reaction analysis. Our results demonstrate improved sensitivity in the in situ experimental analysis, such as the aldehyde amine reaction (sodium benzaldehyde-2-sulfonate solution and aniline solution) and photopolymerization reaction (polyethylene glycol ester). The integration of DMF and NMR technologies provides a promising approach for increasing efficiency and accuracy in chemical analysis.

Effect of homologous molecular crosslinking on the tribological properties of PTFE composites

AbstractA method of improving the tribological properties of hexagonal boron nitride/short carbon fibers/polytetrafluoroethylene (h‐BN/SCFs/PTFE) composites by adding homologous micropowder (MP1100) with polar groups is proposed in this study. Composites of h‐BN/SCFs/PTFE with MP1100 at 0, 8, 16, 24, and 32 wt% were prepared. The pin‐on‐disc device was used to evaluate the friction properties of composites, and wear mechanisms against duplex stainless steel was examined. The experimental results show that MP1100 micropowder improves composite mechanical properties, friction coefficient, and wear resistance of composites. A 78.4% drop in wear rate was measured for 24 wt% MP1100. Such decrease in wear rate is explained based on changes in composite molecular structure, a transfer film formed by the absorption of debris, and the formation of chemically reacted polar group compounds on the steel disc.

Assessing B-Z DNA Transitions in Solutions via Infrared Spectroscopy

Z-DNA refers to the left-handed double-helix DNA that has attracted much attention because of its association with some specific biological functions. However, because of its low content and unstable conformation, Z-DNA is normally difficult to observe or identify. Up to now, there has been a lack of unified or standard analytical methods among diverse techniques for probing Z-DNA and its transformation conveniently. In this work, NaCl, MgCl2, and ethanol were utilized to induce d(GC)8 from B-DNA to Z-DNA in vitro, and Fourier transform infrared (FTIR) spectroscopy was employed to monitor the transformation of Z-DNA under different induction conditions. The structural changes during the transformation process were carefully examined, and the DNA chirality alterations were validated by the circular dichroism (CD) measurements. The Z-DNA characteristic signals in the 1450 cm−1–900 cm−1 region of the d(GC)8 infrared (IR) spectrum were observed, which include the peaks at 1320 cm−1, 1125 cm−1 and 925 cm−1, respectively. The intensity ratios of A1320/A970, A1125/A970, and A925/A970 increased with Z-DNA content in the transition process. Furthermore, compared with the CD spectra, the IR spectra showed higher sensitivity to Z-DNA, providing more information about the molecular structure change of DNA. Therefore, this study has established a more reliable FTIR analytical approach to assess BZ DNA conformational changes in solutions, which may help the understanding of the Z-DNA transition mechanism and promote the study of Z-DNA functions in biological systems.

Effect of molecular structure change on the properties of persistent free radicals during coal oxidation

This study is aimed at exploring the effect of molecular structure changes on the properties of persistent free radicals in coal during the heating process of coal spontaneous combustion (CSC). Therefore, the persistent free radicals and main functional groups variation characteristics in the process of coal oxidation were analyzed by means of in situ electron spin resonance and in situ infrared spectroscopy, and the change relationship between the molecular structure of coal and the persistent free radicals in coal during the reaction was further discussed by correlation analysis. The results showed that the concentration of persistent free radicals showed a stage change of “first decreasing, then increasing and then decreasing”. The g-factor decreases gradually and the heteroatom free radicals are consumed continuously. Dehydrogenation oxidation reaction causes the weakening of the “electron-proton” interaction, which narrows the line-width (ΔH) of free radicals. The phenolic hydroxyl as the electron donating group is converted into -CO functional group through dehydrogenation and oxidation reaction, which promotes the formation and accumulation of persistent free radicals in coal. Under the influence of phenolic hydroxyl, the relationship between the stretching vibration strength of aromatic ring CH and the properties of persistent free radicals in coal shows a similar change law with phenolic hydroxyl. In addition, the chain structure represented by –CH2-, –CH3/–CH2- is continuously consumed in the oxidative dehydrogenation reaction, triggering a series of free radical reactions. The free radicals formed in this process are affected by the steric hindrance of polymer networks and the electron delocalization of aromatic group in coal, so the persistent free radicals can be formed and accumulated. The dehydrogenation and oxidation reaction of the active group led to the reduction of g-factor and ΔH. Persistent free radicals play an important role in the free radical chain reaction that triggers CSC, so preventing the dehydrogenation and oxidation reaction of hydroxyl (especially phenolic hydroxyl) and aliphatic hydrocarbons (especially –CH2- and –CH3/–CH2-) is the key to prevent CSC.

Enhancing Inhibition of Electrical Treeing in XLPE Cables Based on the Targeted Movement of Rejuvenation Fluid Induced by Electric Field

In this study, the inhibition effect of electrical treeing is investigated in a cross-linked polyethylene (XLPE) cable under the targeted movement of rejuvenation fluid induced by an electric field. First, the fluid concentration around the defects is characterized by Fourier transform infrared spectroscopy (FTIR) under different voltages, application durations, and application temperatures. These results show that with increasing applied voltage, application duration and temperature, the fluid concentration around the defects increases nonlinearly. Next, the electrical treeing features of samples with and without electric field induction show that the tree initiation voltage increases and the tree accumulated damage decreases for the samples with electric field induction. By analyzing the changes in the molecular chain structure of the XLPE under different influencing factors, it is found that with applied voltage and duration increase and application temperature decreases, the methyl groups increase and the methylene groups decrease, the diffusion channel of fluid is expanded. Finally, it is proposed that the dielectrophoretic (DEP) force, changes in molecular chain structure, and molecular thermal motion determine the behaviors of the targeted movement of fluid in insulation. The fluid concentration around the defects increases after the targeted movement of fluid, and the electrical treeing inhibition effect is enhanced.

Chemical Characterization of Ultra High Molecular Weight Polyethylene Based Tibial Inserts After Ethylene Oxide Sterilization

Ultra-high molecular weight polyethylene (UHMWPE) has become the gold standard for total joint replacements such as tibial inserts because of its chemical inertness, superior mechanical properties, and biocompatibility. Ethylene oxide sterilization is one of the most common and effective methods used, especially for the sterilization of polyethylene-based polymeric implants. However, variable sterilization conditions can cause a change in the chemical structure of the polymeric material, which affects its mechanical properties and lifetime. The aim of this study is to investigate whether the chemical structure of UHMWPE tibial inserts sterilized with ethylene oxide undergoing certain conditions remains the same. Chemical characterization studies were performed with Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffractometer, differential scanning calorimetry, thermogravimetric analysis, mass spectrometry and elemental analysis techniques recommended for polymeric materials in ISO 10993-8:2020 standard. According to the FTIR results, the spectra of the non-sterile and sterile tibial inserts were compared, and it was determined that the similarity between them was 99.97%. XRD results revealed that after ethylene oxide sterilization, there was no significant shift in the Bragg (1 0 0) peak. The percentages of crystallinity calculated from the fusion enthalpies determined by DSC of sterile and non-sterile samples are 54.3% and 53.3%, respectively. Characterization results revealed that there was no significant change in molecular structure, crystallinity, elemental composition of UHMWPE materials after ethylene oxide sterilization. These results can provide assurance that tibial inserts keep their physical, chemical, and mechanical properties after sterilization.