Molecular Chain Breakage Research Articles

Potential skincare benefits and self-healing properties of Lignosus rhinocerotis polysaccharides as affected by ultrasound-assisted H2O2/Vc treatment

Natural polysaccharides have been recognized as major bioactive components in skincare and wound care products. In this study, the skincare benefits and self-healing properties of Lignosus rhinocerotis polysaccharides (LRP) and its degraded products (DLRP-1, DLRP-2 and DLRP-3) by ultrasound assisted H2O2/Vc treatment (U-H/V) at different ultrasonic intensity (28.14, 70.35, and 112.56 W/cm2) were investigated. U-H/V altered the internal crystalline structure and microstructure of LRP, and enhanced the thermal stability. Due to the breakage of molecular chains after U-H/V, the moisture absorption of LRP was enhanced but the moisturizing property showed a different degree of reduction. U-H/V significantly improved the antioxidant, anti-tyrosinase and anti-inflammatory activities of LRP. Furthermore, the results of enzyme kinetic studies showed a mixed competitive-noncompetitive inhibition of tyrosinase activity by DLRP-3 and the inhibition constant of DLRP-3 on tyrosinase was 2.97 mg/mL. The apparent viscosity of LRP dispersions showed a first increasing followed by decreasing trend as ultrasonic intensity rose. U-H/V enhanced the viscoelastic properties of LRP gels without destroying their self-healing properties. This findings reveal that U-H/V is beneficial for improving the skincare efficacy of LRP, providing a theoretical foundation for the applicability of LRP in wound dressings.

Influence of accelerated aging on mechanical properties and aging behavior of glass fiber reinforced pipe

In this work, the accelerated aging test of GFRP in two thermal environments was conducted. The accelerated aging test was conducted at a constant temperature of 95°C for periods of 3000h to analyze and study the aging behaviors and mechanism under two environments. Resin defects caused by aging were found in the SEM images, and degradation of the fiber/resin interface was observed. Both the hoop tensile test and uniaxial compression test showed brittle fracture characteristics, and the strength of hydrothermal aging specimens decreased more significantly. Due to matrix degradation, uniaxial compression fracture after hydrothermal aging was observed that the resin exhibited poor adhesion. The decrease in the hardness of the outer resin layer was attributed to the development of the degree of molecular chain breakage. ATR-FTIR results showed that the accelerated aging process is accompanied by changes in the concentration of functional groups. The change in C-H intensity was attributed to the post-curing phenomenon. Accelerated aging resulted in the formation of carboxylic acids or esters and the introduction of hydroxyl groups. Thermogravimetric tests showed that accelerated aging did not change the thermal decomposition temperature of epoxy resins, but caused a decrease in resin content.

One-step light-induced hierarchical surface wrinkles on photodegradable polymer films

Photodegradable polymers have become an emerging class of stimulus-sensitive materials for advanced applications, in which using the photolysis characteristic for patterning surface is a key but still a notable challenge. Herein, we report a simple, facile, green and high-efficiency strategy to induce and further tune surface wrinkling only relying on one-step ultraviolet (UV) irradiation of a photodegradable polymer-based film/substrate composite system. Interestingly, a series of intriguing wrinkling states from no wrinkling to surface wrinkling and final no wrinkling with UV exposure take place on the photodegradable polymer film. This wrinkling behavior is intimately related to the competition between the stress accumulation from the heating effect of UV lamp itself and the stress release from the UV-induced molecular chain breakage. Meanwhile, the dependence of photodegradable polymer film modulus and photodegradation-induced stress release on the exposure time has been characterized by taking advantage of surface wrinkling metrology, which is not easily accessible to other systems and methods. This one-step light irradiation strategy has enabled the fabrication of diverse hierarchical surface wrinkling on photodegradable polymer film by simply controlling the UV exposure time. As demonstrated, these hierarchical surface wrinkles with tunable features have been applied for optical information display/storage and optical gratings. Notably, this simple flexible light control strategy not only provides new insights into the photo-induced change in mechanical properties and stress release of photodegradable polymers in molecular level, but also paves new avenues for advanced wrinkle-based applications by incorporating desirable functional materials into the photodegradable polymer-based systems.

Modeling and tracing of polycarbonate (PC) degradation in soil microcosm with a PC microplastics quantification method based on pyrolysis GC–MS

Understanding the migration and transformation of polycarbonate (PC) plastic wastes in the natural environment is crucial for assessing their environmental impact and bioremediation. In this study, PC plastic degradation was modeled and traced in soil microcosm by investigating physiochemical properties changes of PC, the formation of microplastics, and changes in soil microbial communities. Notably, PC microplastics quantification method was also successfully devised by pyrolysis gas chromatography mass spectrometry and also applied herein. Through gel permeation chromatography analysis, the molecular weight of the naturally aged PC film obviously reduced, whereas no change for unaged ones. After 12 months of soil burial, the surface corrosion and holes formation were emerged on the surfaces of both PC films in the non-sterilized soil harboring indigenous microorganisms by scanning electron microscope. The worsened thermal stability of both PC films in non-sterilized soil was demonstrated by thermogravimetric analysis. Meanwhile, the presence of increased hydroxyl group absorption and decreased carbonyl peak highlighted molecular chain breakage in both PC films by Fourier transform infrared spectroscopy. In particular, all the changes were more significant in aged PC than unaged ones. Furthermore, the increase of quantified PC microplastics on the surface of PC film in the non-sterilized soil accompanied the decreasing of microbial diversity and the enrichment of potential functional microorganisms. These findings revealed that the combination of natural aging and indigenous microbes exhibited a noticeable performance in PC plastics degradation in soil microcosm, providing new insights into the degradation mechanism of PC plastic wastes in the natural environment.

Design of Environmental-Friendly Carbon-Based Catalysts for Efficient Advanced Oxidation Processes.

Advanced oxidation processes (AOPs) represent one of the most promising strategies to generate highly reactive species to deal with organic dye-contaminated water. However, developing green and cost-effective catalysts is still a long-term goal for the wide practical application of AOPs. Herein, we demonstrated doping cobalt in porous carbon to efficiently catalyze the oxidation of the typically persistent organic pollutant rhodamine B, via multiple reactive species through the activation of peroxymonosulfate (PMS). The catalysts were prepared by facile pyrolysis of nanocomposites with a core of cobalt-loaded silica and a shell of phenolic resin (Co-C/SiO2). It showed that the produced 1O2 could effectively attack the electron-rich functional groups in rhodamine B, promoting its molecular chain breakage and accelerating its oxidative degradation reaction with reactive oxygen-containing radicals. The optimized Co-C/SiO2 catalyst exhibits impressive catalytic performance, with a degradation rate of rhodamine B up to 96.7% in 14 min and a reaction rate constant (k) as high as 0.2271 min-1, which suggested promising potential for its practical application.

Failure behavior of dielectric films for peaking capacitor subjected to surface flashover under nanosecond pulses

The flashover failure and damage of polypropylene (PP) and polyester (PET) films under nanosecond current pulses were experimentally investigated. A nanosecond pulse current test platform was established to study the flashover characteristics, performance degradation, and structural damage of dielectric films under repeated nanosecond current pulses. The accumulation and emission of surface charge influenced by field distortion and trap distribution were analyzed to clarify the mechanism by which the flashover voltage increases linearly with gas pressure at low pressure and saturates at high pressure. The significant effects of pulse energy, gas pressure, and discharge gap on film damage behavior were investigated. The damage pattern of PP and PET films includes surface deformation, reduced flash-voltage tolerance, molecular chain breakage, and group shedding. The damage of PP films is manifested as fine furrows, while PET corresponds to mountainous bumps. With the increasing number of discharges, the breakdown voltage of PP films decreased significantly, while the flash tolerance performance of PET films was more stable. Under the conditions of high pulse current amplitude, small discharge gap, and low air pressure, the damage degree of the film intensifies, which is characterized by severe destruction to the molecular structure and a significant decrease in flashover withstand voltage. Polymer films, flashover, nanosecond current pulses; performance degradation; microstructural damage.

Effect of addition of triallyl isocyanurate and post‐ultraviolet irradiation on the selected properties of composites of poly(lactic acid), poly(butylene succinate) and nano‐sized calcium carbonate

AbstractComposites of poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and nano‐sized calcium carbonate (CaCO3) with triallyl isocyanurate (TAIC), glycidyl methacrylate and benzophenone (BP) were prepared by using a double screw extruder and blown into films by extrusion blow molding. After exposure to ultraviolet (UV) light at 10, 20, and 40 J/cm2 of irradiation doses, the selected performances of the irradiated films were investigated. UV irradiation increased the tensile performances but had little effect on the thermal behaviors. Scanning electron microscope revealed that UV irradiation enhanced the connection between the two phases of PLA and PBS. The improvement in tensile properties was attributed to the formation of crosslinking during UV irradiation in the presence of TAIC and BP and the enhancement of the interface bonding between the two. However, excessive exposure reduced the elongation at break and fracture energy, attributed to the molecular chain breakage at high doses. On the other hand, the tensile performances improved and the light transmission decreased with increasing the TAIC content up to 2.5 phr after UV exposure at the same irradiation dose. UV irradiation was revealed to be a simple and effective technique to improve the tensile performances of LA/PBS/CaCO3 films with bicontinuous phases.

Near-infrared-dominated photothermal nanofluids for degradation and H2-producing photochemical reforming of fiber-based microplastics

One effective strategy to solve the existing limits of photocatalyst applications is to broaden the spectrum absorption range of catalysts for the degradation and conversion of microplastics. As a result, a brand-new composite system BN/PDA/MoS2 (BPM) was developed in this work to form nanofluids for the degradation and reformation of fiber-based microplastics (FMPs) under the irradiation of near-infrared light (NIR) for the first time. The collaborative system BPM nanofluids/NIR could remove 94.7% and 95.2% of reactive blue KN-R (100 mg/L) and Cr (VI) (10 mg/L) within 60 min, along with the temperature of the system could reach 58°C within 30 min. The weight loss rates of FMPs like PET and PLA were 92% and 34%, respectively after undergoing molecular chain breakage to form a series of small molecules in the system. Moreover, the H2 production maintained an improvement to 100 mmol g−1 (PET) as well as 160 mmol g−1 (PLA) compared to the past research. In conclusion, this work is an effective attempt to develop a new method for water treatment based on the photothermal degradation of microplastics by BPM nanofluids, which also bears new ideas and ways for industrial pollutant removal and waste utilization.

Dynamic compression and fracture of poly(ether-ether-ketone) under plate impact

Plate impact experiments are conducted to investigate shock compression and spallation properties of poly(ether-ether-ketone) (PEEK) up to a peak shock stress of 2.5 GPa with high-speed velocimetry and postmortem X-ray computed tomography. The Hugoniot equation of state and the shock-state Lagrangian sound velocity of PEEK are obtained via reverse impact. The free-surface velocity measurements indicate two-stage spallation. Spall strength and corresponding tensile strain rates are determined via symmetric impact. Spall strength varies in a narrow range of 0.18–0.22 GPa; it increases with increasing shock pressure as a result of increasing tensile strain rate, reaches a plateau and then drops due to shock heating. With the increasing impact velocity, the fracture toughness decreases monotonically. The compression and fracture features at different impact velocities are likely associated with the rearrangement and breakage of molecular chains.

Molecular Dynamic Simulations and Experiments Study on the Mechanical Properties of HTPE Binders.

The mechanical properties of HTPE binders have been systemically studied through combining the microstructure molecular simulations with macroscopic experiments. In this study, the crosslinking structures of HTPE binders were established by a computational procedure. Based on the optimized crosslinking models, the mechanical properties and the glass transition temperatures (Tg) of HTPE/N-100, HTPE/HDI, HTPE/TDI, and HTPE/IPDI binder systems were simulated; specifically, the Tg were 245.758 K, 244.573 K, 254.877 K, and 240.588 K, respectively. Then the bond-length distributions, conformation properties, cohesive energy densities, and fraction free volume were investigated to analyze how the microstructures of the crosslinking models influenced the mechanical properties of HTPE binders. Simultaneously, FTIR-ATR spectra analysis of HTPE binders proved that the special peaks, such as -NH and -NCO, could be seen in the crosslinking polyurethane structures synthesized between prepolymers and curing agents. The dynamic mechanical analysis was carried out, and it found that the Tg of HTPE/N-100, HTPE/HDI, HTPE/TDI, and HTPE/IPDI binder systems were -68.18 °C, -68.63 °C, -65.67 °C, and -68.66 °C, respectively. In addition, the uniaxial tension verified that both the ultimate stress and Young's modulus of HTPE binder systems declined with the rising temperatures, while the strains at break presented a fluctuant variation. When it was closer to glass temperatures, especially -40 °C, the mechanical properties of HTPE binders were more prominent. The morphology of the fractured surface revealed that the failure modes of HTPE binders were mainly intermolecular slipping and molecular chain breakage. In a word, the experimental results were prospectively satisfied using the simulations, which confirmed the accuracy of the crosslinking models between prepolymers and curing agents. This study could provide a scientific option for the HTPE binder systems and guide the design of polyurethanes for composite solid propellant applications.

The Aging Performance of PVDF in Acid Oil and Gas Medium

In the process of transporting oil and gas, the service performance of thermoplastic pipes will decline due to the multiple influences of medium, temperature, and pressure. In order to study the service performance changes of PVDF pipes under oil and gas transportation conditions, the high-temperature autoclave is used to simulate the service state of the pipe in the mediums. The PVDF samples are exposed to simulated oil and gas mediums for 1 week, 3 weeks, 5 weeks, and 7 weeks under 60 °C and 90 °C conditions. After the exposure test, the physical and chemical properties of the PVDF pipe are tested and compared with the initial samples. Compared with the initial sample, the sample quality after the exposure test has a slight increase, with growth rates of 2% and 3% at 60 °C and 90 °C, respectively. Meanwhile, the tensile strength of the samples is about 13% and 21% lower than that of the initial sample, respectively. According to the microscopic morphology analyses, there are some crack defects on the surface of the sample after the exposure test. Through infrared analysis, it is shown that no molecular chain breakage, crosslinking, or other reactions are found after the exposure test. The above analysis shows that the PVDF sample has slight penetration and swelling during the exposure test. However, due to the large force between the PVDF molecules, its mechanical properties have a small downward trend, showing excellent environmental stress crack resistance.

Tuning the properties of Ni-based catalyst via La incorporation for efficient hydrogenation of petroleum resin

The hydrogenation of petroleum resin (PR) is an effective process to prepare high value-added hydrogenated PR (HPR). However, the preparation of non-noble metal-based catalysts with high catalytic activity for PR hydrogenation still remains a challenge. Herein, a La promoted Ni-based catalyst is reported through the thermal reduction of quaternary NiLaMgAl-layered double hydroxides (NiLaMgAl-LDHs). The incorporation of La is beneficial to the reduction and stability of Ni particles with reduced particle size, and the increased alkalinity effectively mitigates the breakage of molecular chains of PR. As a result, the La promoted Ni-based catalyst exhibits high catalytic activity and excellent stability for PR hydrogenation. A hydrogenation degree of 95.4% and 96.1% can be achieved for HC 5 PR and HC 9 PR with less reduced softening point, respectively. Notably, the hydrogenation degree still maintains at 92.7% even after 100 hours’ reaction, much better than that without La incorporation or prepared using conventional impregnation method.

Influence of surface discharge on the deterioration characteristics of ethylene‐propylene rubber cable insulation under alternating current high voltage

To investigate partial discharge-induced deterioration characteristics of ethylene-propylene rubber (EPR) cable insulation under repeated alternating current (AC) voltage on high-speed trains, an experimental platform with a column-plate EPR insulation model is established. The surface condition and breakdown voltage of insulation samples after discharge treatment are observed and measured. In addition, a fitting formula to evaluate the deterioration extent of EPR samples is proposed. The results show that under repeated discharge pretreatments, the volume resistivity increases first and decreases afterwards when discharge magnitude is low. When partial discharge (PD) intensity increases to 100 pC, the volume and surface resistivity decrease monotonously, and the decreasing rate is positively correlated with PD intensity. During PD pre-treatment, a white circle appears near the electrode and turns to pale yellow with PD intensity. For PD pretreatments of 50 and 100 pC, withstand voltage of EPR insulation increase first and decrease afterwards, and the downward trend is slow. For PD pre-treatments of 200 and 400 pC, the withstand voltage decreases significantly with the degradation time. The fitting formula model shows that under the action of a strong electric field, the relationship between the reliability of EPR insulation samples, the probability and rate of molecular chain breakage, and the intensity of discharge activity is not linear.

Effect of hard particles on the tribological properties of hydrogenated nitrile butadiene rubber under different lubricated conditions

It is a common seal failure phenomenon that the hard particles enter the rubbing pair interface, which limits the service life of sealing elements. The tribological properties of the hydrogenated nitrile butadiene rubber under four lubricated conditions were investigated through a pin-on-disk rubbing pair. The experimental results and analysis show that the wear mechanism of rubber in the drilling mud is fatigue wear and the energy dissipation of rubber comes from the adhesive and hysteretic effects. When the drilling mud contains hard particles, the wear mechanism of rubber is abrasive wear, and the kinematic analysis of hard particles combined with the Kelvin-Voigt model indicates that the energy dissipation of rubber consists of a friction-driven term, a molecular chain breakage term and a hysteresis recovery term.

Use of Vibrational Optical Coherence Tomography to Analyze the Mechanical Properties of Composite Materials.

Energy storage and dissipation by composite materials are important design parameters for sensors and other devices. While polymeric materials can reversibly store energy by decreased chain randomness (entropic loss) they fail to be able to dissipate energy effectively and ultimately fail due to fatigue and molecular chain breakage. In contrast, composite tissues, such as muscle and tendon complexes, store and dissipate energy through entropic changes in collagen (energy storage) and viscous losses (energy dissipation) by muscle fibers or through fluid flow of the interfibrillar matrix. In this paper we review the molecular basis for energy storage and dissipation by natural composite materials in an effort to aid in the development of improved substrates for sensors, implants and other commercial devices. In addition, we introduce vibrational optical coherence tomography, a new technique that can be used to follow energy storage and dissipation by composite materials without physically touching them.

Soil microbiomes mediate degradation of vinyl ester-based polymer composites

Polymer composites are attractive for structural applications in the built environment due to their lightweight and high strength properties but suffer from degradation due to environmental factors. While abiotic factors like temperature, moisture, and ultraviolet light are well studied, little is known about the impacts of naturally occurring microbial communities on their structural integrity. Here we apply complementary time-series multi-omics of biofilms growing on polymer composites and materials characterization to elucidate the processes driving their degradation. We measured a reduction in mechanical properties due to biologically driven molecular chain breakage of esters and reconstructed 121 microbial genomes to describe microbial diversity and pathways associated with polymer composite degradation. The polymer composite microbiome is dominated by four bacterial groups including the Candidate Phyla Radiation that possess pathways for breakdown of acrylate, esters, and bisphenol, abundant in composites. We provide a foundation for understanding interactions of next-generation structural materials with their natural environment that can predict their durability and drive future designs.

Formability mechanism of CFRP sheets using multiscale model based on microscopic characteristics of thermosetting resin

This study was undertaken to attempt to establish the press-forming of carbon fiber-reinforced plastic (CFRP) sheets through a forming simulation. Since press-forming induces large plastic deformation of a material, a reliable simulation requires accurate modeling of the plastic deformation of resin. However, there has been little research on the deformation mechanism of thermosetting resins under large plastic forming, which is targeted in this study, and therefore no appropriate plastic deformation model of a resin has been established. Thus, a new model was constructed for a thermosetting resin on the basis of plastic deformation characteristics considering the microscopic mechanism. In the proposed model, the breakage of molecular chains of a thermosetting resin is considered. A molecular dynamics simulation of epoxy resin determined the effect of this molecular chain breakage. It was confirmed that the proposed model can appropriately represent the mechanical characteristics of an actual thermosetting resin. Furthermore, using this model, the numerical analysis of a CFRP sheet through its representative volume element was carried out, and the result explained the improved formability of CFRP at high temperatures, as observed in related experiments.

Comparative study on aromatic thermosetting co-polyester (ATSP) coating and nickel-aluminum bronze on under torsional fretting wear

In current work, the wear resistance of CuNiAl was improved by the application of an aromatic thermosetting co-polyester (ATSP)-based coating on its surface. Tribological behaviors of the ATSP coating at stresses of 1.52, 3.04 and 3.75 MPa under different lubrication conditions (dry friction and oil) were studied by the fretting wear test. The morphology and chemical composition of the coating were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and three-dimensional (3D) optical microscope. Results showed that at the same conditions, the friction torque of the ATSP coating was lower than that of CuNiAl. Significantly, wear was reduced by more than 90% after the application of the ATSP coating. The wear mechanism of the ATSP coating was slight deformation with pits induced by plastic deformation and fatigue crack propagation. The ATSP coating underwent molecular chain breakage during wear and chemical reaction with the friction pair to form a transfer film which played an important role in the reduction of wear.

Effects of alumina trihydrate (ATH) and organic montmorillonite (OMMT) on asphalt fume emission and flame retardancy properties of SBS-modified asphalt

The objective of this study was to evaluate the flame retardancy and emission properties of asphalt binders containing ATH and OMMT. Limit oxygen index test was performed to evaluate the flame retardancy of each asphalt binder. Volatile organic compound (VOC) emission properties of the asphalt mixture in the mixing process were investigated using a designed test method. Thermogravimetry and Fourier transform infrared spectroscopy were used to evaluate the thermal stability and volatile-release properties of the asphalt binders. The results indicated that both ATH and OMMT effectively suppress the VOC release of the modified asphalt. The flame retardancy and VOC-emission properties of the OMMT/ATH modified asphalt were significantly improved. The addition of ATH/OMMT delayed the thermal decomposition and exhibited good thermal-insulation performance, reducing the heat release during asphalt combustion. Additionally, The ATH/OMMT compounds prevented the breakage of molecular chains in the asphalt, promoting the charring of the asphalt during combustion. According to the engineering-property tests of modified asphalt mixtures, the ATH/OMMT significantly improved the high-temperature performance of the asphalt mixture. However, it slightly reduced the thermal-cracking resistance and moisture susceptibility of the asphalt mixture.

Ultrasonic-Assisted Preparation and Characterization of RS3 from Pea Starch

Resistant starch (RS) cannot be digested in the small intestine of healthy individuals and it is considered to have functional properties and fine applications in a variety of foods. Among the different types of starches, RS3 starch presents an exciting new potential as a food ingredient. The objective of the present study was to investigate the potential utilization of ultrasound-assisted process to increase RS3 yield after gelatinization using pea starch as raw material. The ultrasound-assisted RS3production process was optimized using a response surface methodology (RSM). The optimal condition from the model was starch solution concentration 36%, pH 3.5, and ultrasonic time 13 min. At this condition, the RS3 yield was predicted 35.26%. The solubility and swelling degree was analyzed and the RS3 starch was characterized by infrared spectrum (IR), scanning electron microscope (SEM). Results showed that ultrasound could increase the yield of RS3 and the cavitation of ultrasonic wave has a certain effect on molecular chain breakage and starch grain recrystallization during the preparation of RS3.