Changes In Mechanical Strength Research Articles

Freeze-thaw resistance and deterioration mechanism of alkali-activated filling grouts prepared from full industrial solid wastes for tunnels

To promote the application of the proposed alkali-activated grout (AAG) prepared from full solid wastes in cold-zone tunnel projects located at high altitudes and latitudes, it is imperative to fully recognise its endurance to the repeated freezing and thawing in specific service scenarios. For this purpose, two groups of representative AAG were selected as subjects for this study, and a typical OPC-based grout was chosen as the control group. Freeze-thaw cycle tests were carried out on grout samples after 28 days of standard curing using the slow-freeze method to simulate the harsh service environment in cold regions. The deterioration impact of freeze-thaw cycling on the grout samples were evaluated by monitoring the changes in visual appearance, mass loss, mechanical strength, and damage coefficient after 20, 40, 60 and 80 freeze-thaw cycles. Furthermore, the deterioration mechanism of various grout samples under the action of freeze-thaw cycling was revealed by multi-technique characterization methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP). The results show that at the same number of freeze-thaw cycles, the surface deterioration, mass loss and strength damage of AAG were obviously better than that of the OPC-based grout, suggesting that AAG exhibited greater resistance to freezing and thawing than the OPC-based grout. The mass loss ratio increased with the increase of the number of freeze-thaw cycles, following a roughly power function pattern. The deterioration in the flexural strength of grout samples caused by freeze-thaw cycles was more severe than the deterioration in their compressive strength. The gel products of AAG were mainly C-A-S-H and N-A-S-H, which showed stronger resistance to freeze-thaw damage than the gel products of the OPC-based grout, C-S-H and portlandite. Compared with the OPC-based grout, AAG samples possessed a denser microstructure with lower porosity and a smaller proportion of large-sized harmful pores, which was not favourable for the pore water holding and migration of during freeze-thaw cycling and the development of osmotic and frost heave stresses, thus providing better resistance to freezing and thawing. A variety of macroscopic characterisations and microstructural tests have demonstrated the good durability of AAG against the freeze-thaw cycles, which can serve as a scientific foundation for its future engineering uses.

Accounting for decarbonization impacts across the full life cycle of alternative concrete materials: A case-study for graphene-amended cementitious composites

Concrete's extensive use worldwide comes with significant environmental cost, contributing to 8% of annual global carbon emissions. This study investigates the use of life cycle assessment (LCA) and technoeconomic assessment (TEA) as tools to quantify anticipated reductions in global warming potential (GWP) arising from use of novel concrete mixtures or innovative production techniques, with specific focus on a case study related to graphene nanoplatelets (GNPs) as functional fillers. LCA and TEA results are reported for several choices of functional unit (FU) and system boundaries (SB). This approach illustrates how various LCA and TEA framings are differently useful to articulate how changes in technical performance properties such as mechanical strength and durability influence overall life-cycle environmental impacts. Framing 1 make use of a nominal volume-based FU (1 m3) and cradle-to-gate SB. Under this framing, addition of GNPs to the base mix seems to increase GWP and production cost. Framing 2 makes use of a strength-normalized FU and cradle-to-gate SB. Under this framing, life-cycle GWP and production cost for the GNP-amended mortars are decreased relative to the control, due to the appreciable increase in mechanical strength of the GNP-amended mortars. Finally, Framing 3 makes use of the nominal volume-based FU (1 m3) and cradle-to-grave SB. Under this framing, GWP and production cost for the GNP-amended mortars again seem to decrease, due to improved durability which gives rise to longer estimated service life and reduced maintenance. This study illustrates that use of GNPs as functional filler is a seemingly promising strategy for decarbonizing concrete. More broadly, it is concluded that LCAs and TEAs of novel concretes should be framed in a way that articulates how changes in mechanical strength and/or durability properties contribute to changes in environmental impacts over all stages of the concrete life-cycle (i.e., cradle-to-grave). Such framing will help ensure that results that are meaningful to support decision-making in the area of sustainable construction materials.

Study of Surface Repair Materials for Aged Silicone Rubber Insulators

The aging phenomenon of silicone rubber insulators can bring great safety risks for the stable operation of high-voltage transmission lines. To avoid the significant costs and prolonged downtime associated with completely replacing insulating equipment, our research described in this paper proposes a surface repair material for aged silicone rubber insulators using α, ω-dihydroxy-polydimethylsiloxane as the matrix. The material was, after preparation, uniformly applied to the surface of insulators that had been in grid operation for more than 14 years. The chemical structure, elemental composition and surface morphology of the insulator surfaces were characterized both before and after repair. Our research described here also examined the changes in mechanical properties, insulating resistivity, water repellency and adhesion strength of the insulators. The data showed that the functional group types and element contents on the surface of the repaired silicone rubber insulators were restored to those of the new insulators, and the surface and internal cracks were also effectively repaired. Moreover, the water-repellent, mechanical, and electrical properties underwent a notable enhancement. The robust adhesion between the repair material and the deteriorated surface resulted in the formation of a stable and robust adhesive interface. The results demonstrated that the materials created for the purpose of repair in our research had the capability to efficiently enhance the performance of aged insulators. Furthermore, we suggest this study presented a novel path toward addressing the predicament of aging insulation equipment.

Interaction mechanisms between fouling and chemical cleaning on the ageing behavior of ion-exchange membranes during electrodialysis treatment of flue gas desulfurization wastewater

Chemically irreversible fouling (CIF) and erosion caused by chemical cleaning would result in the changes of desalination performance and membrane properties of the ion-exchange membranes (IEMs), which were defined as membrane ageing. Roles of CIF and chemical erosion in the ageing process and the interaction mechanisms have been systematically investigated during the electrodialysis treatment of flue gas desulfurization wastewater. The main foulants contributed to CIF were anionic polyacrylamide (APAM) and CaSO4 for anion-exchange membranes (AEMs) and CaSO4 for cation-exchange membranes. The variation in the ageing behaviors has undergone three main stages. The general tendency of desalination rates was initially decreased, subsequently increased, and gradually declined at last. Membrane morphology and chemical structure of the aged IEMs transformed as a result of the CIF as well as the alternant NaOH and HCl cleaning. Chemical erosion caused the degradation of functional groups and polymer matrix, which was demonstrated by the changes in ion exchange capacity, contact angle, thermal stability and mechanical strength. Cleaning efficiency was limited by CIF, while chemical erosion would in turn affect membrane fouling behaviors. The extended Derjaguin-Landau-Verwey-Overbeek analysis verified that the antifouling ability of aged AEMs enhanced with a decrease of the total interaction energy of APAM-AEM.

Short-term interactions between Longmaxi shale and carbon dioxide-based fracturing fluids

The shale is a dense quarried rock material containing abundant shale oil/gas. Extracting shale gas usually requires fracturing the rock formation to speed up gas desorption and migration. Supercritical carbon dioxide fracturing, as an environmentally friendly and waterless fracturing technique of reservoir stimulation, gains increasing recognition in commercial exploitation of shale oil and gas. However, there is insufficient understanding on the interaction between carbon dioxide-based fracturing fluids and shale, as well as its influence on the mechanical parameters of shale, which are pivotal for determining injection parameters and forming the fracture network. This study focuses on the injection of carbon dioxide-based fracturing fluids to enhance shale gas extraction and carbon dioxide sequestration. Simulation tests of injection were conducted to investigate the influence of different fracturing fluids (deionized water, gaseous/supercritical carbon dioxide, gaseous/supercritical carbon dioxide mixed with brine) injected into shale reservoirs on the microstructure and mechanical properties of shale after short-term physicochemical interaction. This article adopts research methods such as uniaxial compression and uniaxial tensile mechanical experiments based on acoustic emission monitoring and various physical characterizations such as scanning electron microscopy, X-ray diffraction, X-ray fluorescence spectrometer, etc. Results show that following treatment with different carbon dioxide-based fluids, the uniaxial tensile/compressive strength, elastic modulus, fractal dimension of pore structure, and the brittleness index of shale exhibit varying degrees of decrease compared to those of dry untreated shale samples. After interacting with different carbon dioxide-based fracturing fluids, the mechanical parameters and brittleness index of shale decrease more significantly than that of the others as the addition of brine. This study shows that the water in carbon dioxide-based fracturing fluids is a controlling factor affecting the elastic modulus of shale. Additionally, the ductility of the shale increases and the acoustic emission emitting lag due to the coupling effects of brine and carbon dioxide. The change law of the elemental and mineral composition of the shale is consistent with the mechanical strength; and the change of element content and mineral composition is the most significant. Compared to gaseous carbon dioxide, the supercritical carbon dioxide has a greater impact on mineral composition of the shale. The change of mechanical strength and microstructure evolution mechanism caused by the short-term interactions between the shale and fracturing fluids provide theoretical references and implications for the determination of injection parameters and permeability transformation of the Longmaxi shale reservoirs.

Macro–micro correlation analysis on the loess from Ili River Valley subjected to freeze–thaw cycles

The Ili River Valley in Xinjiang, China, is a typical seasonal frozen area where loess landslide disasters have become increasingly common during the freeze–thaw periods in recent years. This study analyzed the macroscopic mechanical strength and microstructure changes of the Ili loess under different freeze–thaw cycles (FTCs) through the post-freeze–thaw triaxial compression test on the unsaturated soil in laboratory. Apart from the scanning electron microscopy (SEM), and the nuclear magnetic resonance (NMR), the macro–micro correlation analysis and the cluster-principal component analysis were applied for the theoretical discussion. The results indicated that the cohesive force of the loess exhibits an initial decreases, followed by the increases, and eventually keep stable after various FTCs, while the internal friction angle showed the opposite developing trend before the final constant. Similar to the strong correlation between the cohesive force and the particle abundance, the internal friction angle is also closely related to the abundance and orientation fractal dimension of the loess particles. However, the principal component analysis results showed that cohesive force strongly correlates with the average maximum pore size and the pore size fractal dimension, for which the internal friction angle most strongly affected by the average maximum particle size. The possible reason is that the extracted principal components represent a class of microscopic parameters with the same or similar change trend, although there may be a certain offset between them. The mechanical deterioration of loess is attributed to the repeated frost heaving force and the migration potential caused by FTCs. The alterations of the microstructure accelerated the deterioration of the macroscopic mechanical properties of the loess, which further widens the understanding of the mechanism behind the deterioration of loess mechanical strength in the Ili River Valley under FTCs, and contributes to the prevention and management of the local landslide disasters.

The Effects of Acute and Chronic Alcohol Administration and Withdrawal on Bone Microstructure, Mechanical Strength, and Remodeling Protein Expression and Their Relation to an Antioxidant and FGF23 In Vivo.

Alcohol's detrimental effects on bone health are well established, yet some literature suggests moderate consumption may offer benefits. With alcohol use on the rise, we investigate the impact of acute and chronic alcohol administration, along with withdrawal, on male Wistar rat femurs. We observed a transient cortical thickness increase with acute alcohol (AA) compared to chronic exposure (CA) but no significant changes in trabecular parameters or mechanical properties. High osteocalcin and osteopontin expression levels were noted in AA, alongside elevated RANKL expression. Conversely, CA showed low TRAP levels. FGF23 expression significantly increased during alcohol withdrawal (AW), while GPX decreased after chronic exposure but rose during withdrawal. Although mechanical strength changes were insignificant, biochemical shifts suggest alcohol exposure promotes bone resorption, reduces antioxidant protection, and potentially hampers active vitamin D and phosphate reabsorption via FGF23 upregulation.

Investigation on the stability and durability of PVDF membranes under prolonged exposure to household bleach cleaning agents

This study delves into the impact of aging on PVDF membranes due to exposure to various NaOCl-based household bleach products, namely Bayclin, Proclin, and Soclin, over different durations (0, 1, 3, and 5 days). The primary objective is to assess the influence of household bleaches as cleaning agents on the stability and durability of PVDF membranes. Our findings underscore that prolonged exposure to NaOCl-based cleaning agents induces changes in pore structure, morphology, mechanical strength, and flux performance of the membranes owing to oxidation by hypochlorite. However, these alterations are mitigated when using household cleaning agents, particularly Soclin and Proclin. For instance, after 5 days, membranes aged with NaOCl exhibited an enlargement of pore size up to 0.2 mm, whereas those aged with Soclin (MS) and Proclin (MP) only experienced an enlargement to 0.12 mm from the original pore size of 0.05 mm. This increase in pore size is undesirable as it adversely affects the selectivity performance of the membranes. Additionally, the hydrophilicity of membranes was found to be better maintained when aged with household products compared to pure NaOCl, as evidenced by the higher water contact angle observed in MP and MS membranes. Furthermore, the flux recovery ratio (FRR) exhibited an upward trend with prolonged aging duration, with Bayclin showing the highest FRR of 180 %, closely to that of pure NaOCl at nearly 190 %, among the other two products. This significant increase in FRR is undesirable as it results from the enlargement of pore morphology caused by damage from exposure to hypochlorites which is stronger in the chemical-grade NaOCl compared to the household bleach products. In summary, this study highlights that household bleaches, especially Soclin and Proclin, present a promising option in terms of stability for prolonged use. These results are crucial for identifying chemicals that are not only more efficient in the cleaning process but also less damaging to the membranes with good stability in long-term use.

Change in Microstructure, Mechanical Strength, Fire Resistance, and Radiation Attenuation Properties of Gypsum Plaster with Boric Acid

AbstractIn this study, the effect of boric acid addition on the microstructure of gypsum plaster was investigated to determine an environmentally friendly gypsum additive that may enhance mechanical strength, fire resistance, and X-ray radiation attenuation properties. The mechanical strengths of bare gypsum and boric acid-added (0–0.5% by weight with respect to gypsum amount) gypsum plasters were evaluated in terms of compressive and bending strengths. The effects of the different addition procedures of boric acid (0.1% by wt.) on the fire resistance of the gypsum plasterboard were also evaluated. X-ray radiation attenuation properties of boric acid-added (0.1% by wt.) gypsum plasterboard were investigated as well. XRD, ATR-FTIR, Helium pycnometer, N2 adsorption–desorption, and SEM analysis were performed to determine the microstructural properties of gypsum plaster. XRD and ATR-FTIR analysis revealed that boric acid did not change the calcium sulfate dihydrate structure of gypsum plaster. Whereas, Helium pycnometer, N2 adsorption–desorption, and SEM analysis showed that the physical properties of gypsum changed with an increase in pore volume, skeletal density, and particle size after boric acid addition. The increase in the pore volume and particle size decreased the mechanical strength of gypsum. However, boric acid addition on the gypsum plaster plate, especially using the spraying method, enhanced the fire resistance of gypsum. Additionally, boric acid slightly enhanced the X-ray radiation attenuation properties (0.7%) of the gypsum plasterboard.

Mechanical strength change and coal damage analysis of frozen saturated bitumite after cryogenic freezing

The changes in mechanical strength and damage analysis of bitumite under the action of liquid nitrogen (LN2) freezing are critical issues that need to be addressed in the application of LN2 in coal seam permeability enhancement. Using an MTS testing machine, strain gauges, and ultrasonic detection instruments, experiments were conducted to obtain stress-strain curves and ultrasonic time-domain images of coal samples after single freezing and cyclic freeze-thaw processes. These data were analyzed to understand the mechanical performance and internal fracture evolution of coal samples subjected to ultra-low temperatures of LN2. The experimental results indicate that: (1) the uniaxial compressive strength and elastic modulus of coal samples subjected to a single LN2 freeze are positively correlated with the freezing time from 0 to 50 min, and negatively correlated with the freezing time from 50 to 180 min. (2) The uniaxial compressive strength and elastic modulus of coal samples subjected to cyclic freezing and thawing with LN2 decrease as the number of freeze-thaw cycles increases. (3) The Poisson's ratio of coal samples subjected to single freezing and cyclic freezing-thawing is negatively correlated with the absolute freezing time. Additionally, the decrease in Poisson's ratio is greater in coal samples subjected to cyclic freezing-thawing compared to those subjected to single freezing. (4) As the absolute freezing time increases, the ultrasonic waveforms of the coal samples begin to become disordered, which is manifested by a decrease in amplitude and a delay in the arrival time of the first wave. Under ultra-low temperature conditions, LN2 can deteriorate the mechanical properties of coal samples, with the degree of deterioration being greater under cyclic freezing-thawing than single freezing. This study can provide theoretical guidance for increasing the permeability of coal seams.

Deterioration Valuation of Polymer Materials in UV-ozone Generator using Microwave Plasma

Various materials are used to sterilize medical instruments. Rubber and other products deteriorate owing to ozone and UV exposure. Ozone is capable of inactivating bacteria and fungi and is known to be effective in inactivating a wide range of viruses. Silent discharge is the mainstream method of ozone generation. The silent discharge method is also concerned with the generation of nitrogen oxides (NOX) caused by nitrogen molecules in the air, and the deterioration of electrodes during use poses a problem. Furthermore, nitrogen oxides react with water in the gaseous phase to produce nitric acid. Nitric acid reacts with several metals to form nitrates. A sterilization device using high concentrations of ozone has not been put to practical use because of the lack of an efficient method for decomposing ozone and the corrosion of metals. If a medical device is altered, it cannot be used as a sterilizing device. In this study, we exposed polymeric materials, which are often used in medical instruments, to ozone and UV light to determine whether their properties changed. Elution tests were conducted on polymeric medical materials from the viewpoints of their physical and chemical properties, functional decline, and biological safety. This study investigates changes in mechanical strength and surface chemical properties, representing the physical and chemical aspects.

Repairing Performance of Polymer-Modified Cement-Based Thin Spray-On Liners on Pre-Cracked Rock-like Specimens

With the development of coal mining and the increase in excavation depth, the stress on roadway surrounding rock is also increasing. This creates conditions for crack development in the roadway, so it is urgent to develop rock repair materials with excellent performance. The ability of thin spray-on liner (TSL) to repair rock and concrete opens up the possibility of reusing abandoned roadways. The ability of TSL to support the surrounding rock is also important in preventing the generation of roadway waste. In this paper, styrene–acrylic emulsion (SAE), vinyl acetate–ethylene copolymer emulsion (VAE), and polyvinyl alcohol powder (PVA) were used to prepare three TSLs. Rock-like materials were configured using cement mortar according to similar principles. Three types of TSLs were tested for basic properties such as viscosity and mechanical strength, which provided data to support the explanation of the repair performance of TSLs. Three TSLs were used to repair pre-cracked rock-like specimens (PR). The number of brushing times and the angle of PR’s cracks were regarded as test variables. Changes in the mechanical strength of repaired PRs were tested by compressive and flexural tests. TSL repair performance was evaluated with the help of mechanical strength changes. Results show that polyvinyl alcohol powder modified cement-based thin spray-on liner is most suitable for repairing rock cracks; as the thickness of the brush slurry increases, its repair performance continues to improve. This paper can provide experience and a theoretical basis for the research of other rock repair materials, and it is also instructive for repairing shotcrete in the roadway.

Mechanical strength changes of combustible municipal solid waste components during their early pyrolysis stage and mechanism analysis.

Implementation of municipal solid waste (MSW) source segregation leads to a more convenient recycle of combustible MSW components. Textiles, plastics and papers are commonly available combustible components in MSW. Their shredding is conducive to resources recovery. But these components usually have high tensile strengths and are difficult to shred. To understand their mechanical strength changes in their early pyrolysis stage will help to address this problem. In this study, a universal electronic testing machine was used to determine the breaking strengths of the materials including cotton towel, polyethylene glycol terephthalate (PET), ivory board (IB), kraft paper (KP) and wool scarf in the temperature range of 30-250°C under N2 atmosphere, and the mechanisms of their strength changes were explored. The reaction force field molecular dynamics (ReaxFF-MD) simulation was used to explain the decomposition behaviours of different sugar groups of hemicellulose in cotton and paper and the change of van der Waals energy of wool during their early pyrolysis stages. The results showed that breaking strengths of all the combustible MSW components reduced as the temperature increased. The breaking strength of PET was found to have the highest descent rate with increasing temperature, then the descent rates of wool and cotton came as the second and third, respectively. Compared with cotton, the breaking strengths of KP and IB decreased more slowly. As the temperature increased, the breaking strength of cotton reduced mainly due to the decomposition of the glucuronic acid in hemicellulose, and the reduction was characterized by CO2 release. The breaking strength reduction of PET was caused by its molecular chain being relaxed. The breaking strength reduction of wool was firstly caused by the decrease in the van der Waals energy between its molecules, and then caused by molecular chain breaking. In addition, in order to understand the influence of material size on the breaking strength change during thermal treatment, the breaking strengths of cotton yarn bundles were correlated with their yarn number and temperature. This study lays the foundation for understanding changes in mechanical strengths of combustible MSW components during their early pyrolysis stage.

Synergistic promotions between high purity H2 production and CO2 capture via sorption enhanced chemical looping reforming

Hydrogen energy, a promising clean source, holds potential to combat global warming. To achieve efficient and low-carbon H2 production, we proposed an isothermal sorption-enhanced chemical looping reforming (SE-CLR) process to realize the high-purity hydrogen production and in-situ CO2 capture at mild temperatures (550–650 °C). For practical application, the process is characterized to use Fe-Ni double metal oxide particles as steam methane reforming oxygen carriers, and K2CO3-promoted Li4SiO4 particles as CO2 sorbent. The oxygen transfer capacity of metal oxide matintained high at 57.4%, and the K-Li4SiO4 absorbents remained at 22.5% CO2 absorption capacity over 200 isothermal absorption-regeneration cycles. Conducting a synergistic conversion mechanism within double metal oxides and absorbents, and adjusting the absorbent-to-metal oxide mass ratio to 7:4, enhanced hydrogen purity to 92% and CO2 uptake to 95%. Furthermore, in-situ CO2 removal in CLR processes achieved methane conversion and H2 production rates equivalent to conventional CLR processes under the same reaction conditions, but at temperatures ∼60 °C lower. The effects of the reaction temperature, pressure, steam-to-methane and methane-to-solid ratios on SE-CLR performance were studied systematically. Finally, stable hydrogen production with a purity of 91%–89% and CO2 uptake of 94%–91% were obtained over 25 CLR cycles, with minimal changes in mechanical strength of particles.

Study of the Kinetics of Adhesive Bond Formation Using the Ultrasonic Method

Adhesive bonding is widely used in modern industry. It has many advantages—the main one being the reduction in production costs. It also has certain limitations. One of the limitations of adhesive bonds is the relatively long bonding time of the joints. The main objective of this research was to determine the possibility of studying the kinetics of adhesive bond formation using a non-destructive ultrasonic method. A research experiment was planned and carried out. Adhesive specimens were prepared, and their quality changes over time were evaluated. In addition, the change in ultrasonic measures during the testing of these bonds was evaluated, as well as the hardness of the adhesive. In this study, the choice of test apparatus was made, in particular ultrasonic probes for the adhesive used and the materials to be bonded. The choice of adhesive was also made, for one in which bonding phenomena occur uniformly throughout the volume. This work examined the changes in the mechanical strength and hardness with time. The tests showed that the greatest changes in mechanical strength occur within the first 24 h after the bond was made. With the mechanical strength reaching 12.6 Mpa after 216 h, the strength in the first 24 h was 10.36 (for bonded steel sheets). For bonded steel discs, the maximum tensile strength was 26.99 Mpa (after 216 h), with a hardness of 22.93 Mpa during the first 24 h. Also, significant changes were observed in the adhesive hardness during the first 24 h. The hardness of the adhesive after 216 h was 70.4 Shore’a on the D scale, while after 24 h it was 69.4 Shore’a on the D scale. Changes in the ultrasonic parameters of the adhesive bond quality were found to occur along with changes in the bond quality.

Carboxyl-modified nanocellulose (cNC) enhances the stability of cNC/pullulan bio-nanocomposite hard capsule against moisture variation

The quality of polysaccharide-based films and hard capsules is often affected by changes in relative humidity, manifesting as unstable water content, and changes in mechanical strength that make them brittle or soft. Herein, carboxyl-modified nanocellulose (cNC) was prepared and used as a new component to successfully improve the moisture resistance of cNC/pullulan/high-acyl gellan bio-nanocomposite hard capsules (NCPGs). Homogenously dispersed cNC in the pullulan/high-acyl gellan matrix could render the formation of more hydrogen bonds that provided additional water-binding sites and limited the free movement of pullulan and high-acyl gellan molecular chains within NCPGs. This contributed to a decreased amount of pooling adsorption water and an increased amount of Langmuir adsorption water in NCPGs, as compared to pullulan/high-acyl gellan hard capsules (PGs) without cNC. Therefore, the equilibrium moisture content (EMC) values of NCPGs decreased at 83 % relative humidity and increased at 23 % relative humidity compared to those of PGs. Together with enhanced mechanical and barrier properties, NCPGs effectively protected encapsulated amoxicillin and probiotic powder from changes in the outside humidity. Additionally, NCPGs exhibited faster drug release. This study presents a new mechanism and strategy for fabricating films and hard capsules with enhanced stability against moisture variation.

The impact of resin harvest history on properties of Scots pine wood tissue

This study was conducted in Central Europe (Poland) in pine forests that were subjected to the process of resin harvesting in the 1970s. Forty trees were designated for the study, which had one or two resin blazes. The objectives of the experiment were to determine the effect of resin tapping on the changes in annual growth, wood density, and mechanical strength of wood in the damaged trees. Resin tapping affected the development dynamics, especially in trees with a single resin blaze. In addition, bark cutting affected wood density over the cross-section. However, no significant variation was found in terms of the mechanical properties of wood, which may support the theory of adaptive tree growth and optimization of tree’s structure to its functions.

Mechanical Properties of 3D Printed Parts and Their Injection Molded Alternatives Subjected to Environmental Aging.

Additive manufacturing is the technology used in medical, industrial, or lifestyle applications. The scientific literature include works reporting various manufacturing parameters' influence on changes in additive manufacturing components' mechanical behavior, especially with fused filament fabrication (FFF). The changes in mechanical strength and toughness of FFF compared to injection molding parts were studied. In the study, the FFF and injection molded parts were aged in buffered saline solution in temperature of 37°C. The results show that by differentiating the orientation of the fibers during fabricating, it is possible to reach strength values similar to injection molded parts. Therefore, it was reported that the mechanical strength and toughness changed significantly after aging, and the FFF components lost strength more quickly than their injected alternatives. The research results can be useful during the fabrication of mechanically stable and biodegradable components, which can be more easily recycled than their injected alternatives when used with warmer temperatures and humidity. This article completes the present state of the art on the problem of environmental aging of parts produced from biodegradable materials. Especially, the research was related to the multilayer laminate structure.

Nucleophilic substituted NH2-MIL-125 (Ti)/polyvinylidene fluoride hollow fiber mixed matrix membranes for CO2/CH4 separation and CO2 permeation prediction via theoretical models

Improper degree of nucleophilic substitution on PVDF may reduce the crystallinity of the membrane and weaken mechanical properties. Subsequently, the drop in membrane crystallinity might cause a decline in membrane performance, particularly in gas separation, which was unpropitious. Also, inappropriate models for predicting CO2 permeation of MMMs would lead to incompatibility between theoretical results and experimental CO2 permeation data, subsequently affecting the design of the membrane separation system. In the current work, ammonia solutions with 3 different concentrations (25, 30, and 35% v/v) were used to modify PVDF incorporated with 2 wt% NH2-MIL-125 (Ti). The SEM, XPS, XRD, contact angle, and mechanical analyses were performed to investigate the structural changes, degree of substitution on PVDF, crystallinity, hydrophilicity, and changes in mechanical strength, respectively. In single and CO2/CH4 (50:50) mixed gas test, PVDF-4 showed the highest ideal and real selectivity, which also showed a good increment in CO2 permeance compared to pure PVDF and 2 wt% NH2-MIL-125 (Ti)/PVDF HFMMM. Therefore, appropriate ammonia solution modification conditions are required to enhance the membrane properties without severely compromising the stability of the membrane and ensuring better CO2 gas separation. After aging, PVDF-4 demonstrated a 23% reduction in CO2 permeance, while also showing a 9% improvement in CO2/CH4 ideal selectivity. The optimized membranes were then coated with PDMS to enhance its CO2/CH4 (50:50) mixed gas separation performance. The basic Maxwell, Bruggeman, Pal, Lewis–Nielson, and Bottcher model, along with modified Pal model, were used to estimate the CO2 permeation of PVDF HFMMMS developed. Modified Pal model demonstrated −3.68 AARE% towards PVDF-2 which has higher accuracy in the prediction of CO2 permeation compared to other models in this study.

Aging resistance under short time ultraviolet (UV) radiations of polymer wood composites entirely based on wastes

The paper studies the UV exposure influence on the mechanical properties, crystalline, interface and morphology of the optimised (previously water immersed) composites with wastes of rubber, PET, HDPE, wood and inorganic filler (CaO and fly ash). The mechanical strength, photo-degradation, crystalline structure and surface morphologies changes of the composites are evaluated after their exposure under simulated UV light and compared to unexposed ones. Experimental results showed UV exposure lead to the increase of Young moduli, compressive strength and tensile for high content PET samples. Significant mechanical strength even after water immersion and UV exposure were recorded for the rubber–PET–HDPE–wood–fly ash with a compression strength of about 70 MPa and for the 40 wt% PET composites with Young moduli of about 15 MPa. Therefore short term UV treatment could be used to enhance de composite’interface strength aiming at their outdoor applications.