Loss Of Tensile Strength Research Articles

Transforming Tree Bark Waste into a Green Composite: Mechanical Properties and Biodegradability

In this study, a “green composite” material made from 60% tree bark and 40% polylactic acid (PLA) was fabricated and evaluated according to its mechanical properties and biodegradability. Biodegradation tests were performed in compost, simulated aquatic environments, and natural soil. In compost, the composite degraded steadily and reached 47% biodegradation after 11 weeks. In soil, the material quickly lost much of its tensile strength, and after 6 weeks, there were signs that the surface and the internal structure had started to deform. Biodegradation in aquatic environments also caused a loss of tensile strength after only a few weeks. Because of the high filler content, excellent biodegradability, and light weight, the composite material has a low environmental footprint. The material could be used in agricultural equipment such as plant pots.

Room-temperature ionic liquid electrolytes for carbon fiber anodes in structural batteries

Structural batteries require thermally stable electrolytes paired with carbon fibers (CFs), which offer advantages of lightweight, high mechanical strength, and good electrical conductivity. This work evaluated various room-temperature ionic-liquids (RTILs) as compatible electrolytes for CF anodes and LiFePO4 (LFP) cathodes on CFs. This LFP/CF full-cell design eliminates Cu and Al current-collectors, potentially enhancing gravimetric energy and reducing costs. Among various RTILs, LiTFSI in N-propyl-N-methylpyrrolidinium (PYR13) – bis(fluorosulfonyl)imide (FSI) offered promising LFP/CF full-cell performances, attributed to the formation of solid electrolyte interphase (SEI) layer on the CF anode with components such as Li2Sx, Li2S–SO3, LiF, LixFy and F–SO2, identified through X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analyses further confirmed the electrochemical stability of the SEI layer on CF anodes. The LFP/CF cell delivered an initial capacity of 119 mAh/g and relatively high Coulombic efficiency when using the 1 M LiTFSI in PYR13-FSI. CF cycled in different electrolytes exhibit varying mechanical properties with up to 10.08 % loss in tensile strength, which may be related to CF surface degradation during cycling. The 1 M LiTFSI in PYR13-FSI is non-flammable, offering a significant thermal safety. This work successfully demonstrated the significant potential of 1 M LiTFSI in PYR13-FSI RTILs, which enables the use of CF as both an anode active material and cathode current collector for structural battery applications.

The Influence and Mechanism of Polyvinyl Alcohol Fiber on the Mechanical Properties and Durability of High-Performance Shotcrete

This study investigates the impact of polyvinyl alcohol (PVA) fibers on the mechanical properties and durability of high-performance shotcrete (HPS). Results demonstrate that PVA fibers have a dual impact on the performance of HPS. Positively, PVA fibers enhance the tensile strength and toughness of shotcrete due to their intrinsic high tensile strength and fiber-bridging effect, which significantly improves the material’s splitting tensile strength, deformation resistance, and toughness, and the splitting tensile strength and peak strain have been found to be increased by up to 30.77% and 31.51%, respectively. On the other hand, the random distribution and potential agglomeration of PVA fibers within the HPS matrix can lead to increased air-void formations. This phenomenon raises the volume content of large bubbles and increases the average bubble area and diameter, thereby elevating the pore volume fraction within the 500–1200 μm and >1200 μm ranges. Therefore, these microstructural changes reduce the compactness of the HPS matrix, resulting in a decrease in compressive strength and elastic modulus. The compressive strength exhibited a reduction ranging from 10.44% to 15.11%, while the elastic modulus showed a decrease of between 8.09% and 12.67%. Overall, the PVA-HPS mixtures with different mix proportions demonstrated excellent frost resistance, chloride ion penetration resistance, and carbonation resistance. The electrical charge passed ranged from 133 to 370 C, and the carbonation depth varied between 2.04 and 6.12 mm. Although the incorporation of PVA fibers reduced the permeability and carbonation resistance of shotcrete, it significantly mitigated the loss of tensile strength during freeze–thaw cycles. The findings offer insights into optimizing the use of PVA fibers in HPS applications, balancing enhancements in tensile properties with potential impacts on compressive performance.

Melt processing of chemically modified cellulosic fibres with only water as plasticiser: Effects of moisture content and processing temperature

To replace petroleum-derived polymers with cellulose fibres, it is desirable to have the option of melt processing. However, upon heating, cellulose degradation typically starts before the material reaches its softening temperature. Alternatives to plastics should also, ideally, be recyclable via existing recycling streams. Here, we address the problem of melt processing cellulose as fibres while preserving recyclability. Native cellulose fibres were partially modified to dialcohol cellulose to impart thermoplastic characteristics. We demonstrate melt processing of these modified fibres with only water as plasticiser. Processability was investigated at selected processing temperatures and initial moisture content by monitoring the axial force of the extruder screws as a rheological indicator. The effects on molecular structure, fibre morphology and material properties were characterised by NMR spectroscopy, microscopy, tensile testing, fibre morphology analysis and X-ray diffraction. When comparing the melt-processed extrudate with handsheets, the already exceptional ductility was further increased. Moderate losses in tensile strength and stiffness were observed and are attributable loss of crystallinity and fibre shortening. This is the first report of strong and durable extrudates using cellulosic fibres as the only feedstock. Finally, the potential for recycling the processed material with unmodified fibres by paper recycling procedures was demonstrated.

Biodegradation Behaviour of the Composite Consisting of Polypropylene and Bauhinia Vahlii Fiber

AbstractThe current study focuses on the degradation rate of polypropylene (PP) and Bauhinia Vahlii (BV) fibers under soil burial and natural weathering conditions for 360 days. The BV‐PP composite was produced with varying BV fiber compositions (0, 10, 20, and 30 wt.%) and 3 % MAPP (Maleic Anhydride Grafted Polypropylene). In addition, MAPP is employed as a coupling agent to improve fiber‐matrix compatibility and promote degradation. The XRD examination shows that a 10 % BV‐PP composite has a crystallinity index of 52.05 %, which is higher than that of neat PP. The rate of biodegradability was investigated using weight loss and tensile properties. The largest degradation was seen in natural weathering conditions with 30 % composite showing the maximum weight loss of 3.8 % and loss in tensile strength and modulus of 16.76 % and 5.11 %, respectively. Simultaneously, no weight loss or drop in tensile characteristics was found in the case of neat PP over 360 days. The SEM images of soil burial show material deterioration, which may be aided by bacterial and fungal activity, whereas natural weathering conditions show a large crack, rougher fracture surface, and cavities, which are attributed to thermal stresses, changes in moisture content, and ultraviolet radiation, thereby promoting the degradation process.

Study on Strength Properties of of Woven Fabrics Including Recycled Cotton Yarns.

In this study, plain fabrics were produced from yarns obtained from cotton fibers and recycled cotton fibers obtained from yarn waste. Within the scope of the study, yarns with cotton/recycled cotton fiber ratios of 100-0%, 90-10%, 80%-20%, 70-30%, 60-40% were used. All fabrics were subjected to finishing processes respectively under the same conditions. Breaking strength and tear strength tests were carried out to understand the effect of the recycling rate on the strength loss in fabrics. In the research, important findings were reached regarding these fabrics. It was determined that there was a decrease of nearly 45% in the tear strength of fabrics obtained by mixing 40% recycled fiber. Additionally, the loss in tensile strength was less than the loss in tear strength.

Dynamic borate ester bond reinforced hydroxyethyl cellulose/corn starch crosslinked film for simple recycling and regeneration

Endowing biodegradable plastics with easy recyclability can reduce competition with food resources and further enhance their environmental friendliness. In this work, 4-carboxyphenylboronic acid was grafted onto the side chains of hydroxyethyl cellulose and compounded with inexpensive cornstarch. Upon the introduction of tannic acid, stable and reversible borate ester bond rapidly formed, yielding composite biodegradable plastic films with outstanding mechanical properties and facile recyclability. The formation of a dynamic cross-linked network mitigates the aggregation of gelatinized starch molecules, enhancing the flexibility and durability of the crosslinked film. Testing revealed that while maintaining high tensile strength, the elongation at break of the crosslinked film increased by 952.86 %. The static water contact angle was improved from 32.74° to 78.82°, with a change of <5° within 1 min, demonstrating enhanced water resistance. Excellent antioxidant and thermal stability were also characterized, the crosslinked film can be easily dissolved by heating in water at pH = 6.5 and reshaped in water at pH = 7.2. After five times of regeneration, the tensile strength loss was as low as 5.68 %. This eco-friendly and efficient recycling process is promising during green chemistry.

Research on the aging mechanism of polypropylene nonwoven geotextiles under simulated heavy metal aging scenarios

We conducted accelerated aging experiments on two types of polypropylene (PP) nonwoven geotextiles (filament geotextile and staple fiber geotextile), immersing them in five different simulated liquids at temperatures of 25 °C, 55 °C, and 85 °C for 200 days. At 85 °C and a pH of 1, the tensile strength and elongation at break of PP filament materials decreased by 95% and 86%, respectively. The presence of heavy metals(arsenic and cadmium), speeds up the aging process in both types of PP geotextiles. Under identical conditions, these heavy metals can increase the loss of tensile strength in geotextiles by more than 7% in 200 days. Increases in temperature, acidic environment, and heavy metal concentration all contribute to faster aging of these geotextiles. Although filament geotextiles exhibit higher tensile strength and elongation at break, staple fiber geotextiles show a lower rate of tensile strength loss during aging and better maintain their tensile strength in high-temperature acidic conditions. During the aging process, cross-linking and recrystallization occur, both of which control the aging rate and the formation of microplastics.

Exploring the potential of insect gut symbionts for polyethylene biodegradation

The global issue of synthetic plastic pollution is escalating, necessitating innovative bioremediation approaches. Specific insect species have developed symbiotic associations with intestinal microorganisms that possess the ability to degrade resistant plant materials, such as lignocellulose. This is the first study to our knowledge to isolate, characterize, and compare microbial isolates (yeast and bacteria) extracted from the guts of wood-feeding termites (WFT) and lesser waxworms (LWW). The objective was to determine their efficacy in decomposing recalcitrant pollutants, such as low-density polyethylene (LDPE). The isolates belonged to numerous taxonomic groups, as determined by molecular identification; these groups included Bacillus, Citrobacter, Cellulosimicrobium, Rhodococcus, Pseudomonas, Candida, and others. A number of isolates had the potential to degrade LDPE. After 45 days of incubation, the polymer sheets lost 19.8 % of their weight for Bacillus cereus (LDPE-DB2) and 15.4 % of their weight for Candida guilliermondii (LDPE-DY6). Additionally, LDPE degraded by LDPE-DY6 showed a tensile strength loss of 50.3 % compared to that degraded by LDPE-DB2 (58.3 %). During this time, robust biofilm formation was observed on the surfaces of the polymers. Extracellular enzymes such as cutinases, aryl alcohol oxidases, and peroxidases, secreted by specific yeast and bacterial isolates, contribute to the degradation of plastic and recalcitrant biopolymers. Notably, the isolates from LWW demonstrated a greater advantage in this regard than those from WFT. Bacillus cereus, Pseudomonas aeruginosa, Candida guilliermondii, and Sterigmatomyces halophilus were found to have the highest activities in degrading LDPE among the studied WFT and LWW gut-derived symbionts. This study paves the way for a new opportunity to enhance polyethylene degradation by insect gut bacteria and yeasts that may facilitate biotechnological applications for plastic waste remediation.

Effects of Zr additions and process annealing on mechanical and corrosion properties of AA5383 Al–Mg alloys

Abstract The study investigates how Zr additions and process annealing affect mechanical and corrosion properties of AA5083 Al–Mg alloys by microstructural examination, tensile strength, hardness testing and ASTM G67 nitric acid mass loss test. In the present work, process annealing temperatures were set to 220 °C and 250 °C. The results show that the hardness and tensile properties of Zr-containing cold rolled alloy were superior to that of Zr-free cold rolled alloy before and after process annealing treatment and sensitization heat treatment. Unfortunately, adding Zr to AA5383 alloy significantly degraded the corrosion resistance of the Zr-containing cold rolled alloy annealed at 220 °C. For improving corrosion resistance of Zr-containing alloy, annealing temperature could be increased to 250 °C to avoid a marked drop in the corrosion resistance.

Electrochemical properties and corrosion induced mechanical degradation of biomedical Zn–Cu–Li alloy in simulated body fluid

The electrochemical behavior and corrosion induced mechanical degradation of biodegradable Zn–2Cu–0.03Li alloy were in detail investigated. The results indicated that the corrosion product film presented an increasing corrosion resistance, while the localized corrosion induced by microgalvanic effect was intensified. Corrosion pits, as the typical defect, acted as the crack initiation sites and accelerated the fracture process of the Zn–2Cu–0.03Li alloy. Accordingly, the fracture mode transformed from ductile to brittle failure. Significant loss in ultimate tensile strength and elongation of the alloys occurred due to strong stress concentration at corrosion pit, threatening the mechanical reliability after implantation.

Investigation of weave influence on flame retardancy of jute fabrics

Abstract In the present work, seven different weave-structured jute fabrics were treated using an organophosphorus-based flame-retardant (FR) chemical (ITOFLAM CPN) along with a cross-linking agent (KNITTEX CHN) by the pad–dry–cure method. The flammability properties were determined by vertical and horizontal flammability tests and limiting oxygen index (LOI). The flame-spread and after-glow time in the vertical flammability test were calculated to be zero seconds on the FR-treated fabrics while the untreated fabrics were completely burnt. The burn rate in the horizontal flammability test is also measured at zero seconds on the FR-treated fabrics. The highest LOI (43.33) is found in the Twill-3/1 and 4-ends Irregular Satin fabrics, while other fabrics had similar LOI (40) results after FR treatment. The maximum char length (71 and 74 mm) was determined in the warp and weft directions of the Plain-1/1 fabric, while an average minimum char length was found for Twill-2/2 fabrics. Despite the significant improvement in FR performance, it strongly affects the tensile properties of FR-treated fabrics. A substantial loss of tensile strength loss was measured in all treated fabrics; however, the highest loss (77%) was examined for the Plain-1/1 fabric, and the lowest loss of strength (60%) was in the Basket weave (Matt)-4/4 fabric.

Mechanical Response and Deterioration Mechanisms in Freeze–Thaw Environments for Crushed Stone Stabilized with Industrial Solid Waste

The conflict between industrial solid waste treatment and environmental protection in Inner Mongolia is becoming increasingly prominent. Using industrial solid waste such as mineral powder, fly ash and wet calcium carbide slag as raw materials, using the alkali excitation method to prepare geopolymer, and replacing part of the cement for pavement base can effectively absorb industrial solid waste and realize the dual goals of waste utilization and environmental protection. Through mechanical properties tests before and after a freeze–thaw cycle and micro tests such as scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), the strength variation rule and mechanism of geopolymer-cement stabilized aggregate under freeze–thaw cycles were deeply investigated. The relationship between different porosity indexes and mechanical properties in mercury intrusion porosimetry (MIP) was established by grey relation analysis. The results prove that a mixture with impaired properties after freeze–thaw cycles and the anti-freezing performance of the mixture with 20% geopolymer content are better than that of the mixture with no geopolymer content and 40% geopolymer content. The loss rates of unconfined compressive strength (UCS) after 5, 10 and 20 freeze–thaw cycles were 9.5%, 27.6% and 36.4%, respectively. The appropriate addition of geopolymer can enhance the anti-freezing performance of a stable aggregate. Following freezing and thawing cycles, the unconfined compressive strength (UCS) damage of the mixture is mainly influenced by a rise in total porosity, and the grey correlation degree is 0.75. The increase in more harmful pores and total porosity mainly results in an indirect tensile strength (ITS) loss. The grey correlation degree is 0.91. The compressive rebound modulus (CRM) is not affected by the change in pores but decreases with a rise in the geopolymer dosage.

Simultaneous Application of Acid Protease and Transglutaminase on Wool and its Optimisation to Achieve Machine Washable Care Claim

In the previous work by the same authors, optimisation of sequential application of acid protease and transglutaminase was carried out to achieve Woolmark specification AW-1 for the machine washable care claim, that is, less than 3% total shrinkage. As a result of optimisation, the total warp shrinkage reduced to 2.64% with only 2.82% loss in warp tensile strength. In this work, simultaneous application of acid protease and transglutaminase was explored and optimised using Box–Behnken design of experiment. The optimisation was carried out using two criteria. In the first criterion, the model was used to predict treatment parameters for minimum total warp shrinkage with minimum loss in warp tensile strength. Taking these predicted treatment parameters, wool was treated with acid protease (1%, owf) and transglutaminase (2.8%, owf) at pH ∼5.3 and 50°C for 60 min. After treatment, the total warp shrinkage reduced to only 4.32% with 4.65% loss in warp tensile strength. This was not only higher than the optimised sequential application of both the enzymes but also failed to meet the Woolmark specification for machine washable care claim. So, the second criterion was used in which the prediction was taken for treatment parameters to achieve the minimum total warp shrinkage without any constraints on loss in warp strength. Again, taking these predicted treatment parameters, wool was treated with acid protease (1.3%, owf), transglutaminase (1.6%, owf), pH ∼4.7 at 55°C for 85 min. Under these treatment conditions, the total warp shrinkage reduced to 2.89% with 10.1% loss in warp strength. Furthermore, interaction between the enzymes also plays a role in the outcomes of the treatment. It was evident that there was a loss in transglutaminase activity as a result of acid protease digestion. However, there was no loss in the activity of acid protease, indicating that transglutaminase did not have any negative influence on the activity of acid protease.

The role of the fiber–matrix interface in the tensile properties of short fiber–reinforced 3D‐printed polylactic acid composites

AbstractIn this study, we investigate the relationship between structure and properties of fiber–matrix adhesion for material extrusion–based 3‐dimensional (3D) printed composites. We examine the influence of fiber length and fiber content on the tensile properties of glass, basalt, and carbon fiber–reinforced polylactic acid (PLA) composites. Short fiber–reinforced filaments were produced, then, simple micromechanical models were used to predict the in‐plane tensile properties. We found that interlayer tensile properties are strongly influenced by fiber–matrix adhesion. If adhesion is sufficient, the fibers and matrix deform together under tensile load. A second‐order relationship describes interlayer tensile strength in relation to fiber content between 5 and 25 w%, with a maximum at 15 w%, for carbon and basalt fiber–reinforced composites. If adhesion is weak, the crack propagates along the fiber–matrix interface, causing brittle fracture and low strength. This behavior was noted for the glass fiber composite, for which the calculated interface shear strength was the lowest (1.4 MPa). In this case, fiber content is inversely proportional to interlayer tensile strength. Our results show the role of fiber–matrix adhesion quality on tensile properties, which has a major impact on both the accuracy of predictions and the damage processes.Highlights Critical fiber length determines accuracy of tensile property estimates Quality of fiber–matrix adhesion governs interlayer damage process Poor adhesion causes brittle fracture and low strength Second‐order relationship of interlayer tensile strength and fiber content Loss of interlayer tensile strength in composite due to fiber–matrix interface

Characterization and Implementation of Cocoa Pod Husk as a Reinforcing Agent to Obtain Thermoplastic Starches and Bio-Based Composite Materials.

When the cocoa pod husk (CPH) is used and processed, two types of flour were obtained and can be differentiated by particle size, fine flour (FFCH), and coarse flour (CFCH) and can be used as a possible reinforcement for the development of bio-based composite materials. Each flour was obtained from chopping, drying by forced convection, milling by blades, and sieving using the 100 mesh/bottom according to the Tyler series. Their physicochemical, thermal, and structural characterization made it possible to identify the lower presence of lignin and higher proportions of cellulose and pectin in FFCH. Based on the properties identified in FFCH, it was included in the processing of thermoplastic starch (TPS) from the plantain pulp (Musa paradisiaca) and its respective bio-based composite material using plantain peel short fiber (PPSF) as a reinforcing agent using the following sequence of processing techniques: extrusion, internal mixing, and compression molding. The influence of FFCH contributed to the increase in ultimate tensile strength (7.59 MPa) and higher matrix-reinforcement interaction when obtaining the freshly processed composite material (day 0) when compared to the bio-based composite material with higher FCP content (30%) in the absence of FFCH. As for the disadvantages of FFCH, reduced thermal stability (323.57 to 300.47 °C) and losses in ultimate tensile strength (0.73 MPa) and modulus of elasticity (142.53 to 26.17 MPa) during storage progress were identified. In the case of TPS, the strengthening action of FFCH was not evident. Finally, the use of CFCH was not considered for the elaboration of the bio-based composite material because it reached a higher lignin content than FFCH, which was expected to decrease its affinity with the TPS matrix, resulting in lower mechanical properties in the material.

Investigation of Performance Properties of Wool Fabrics Treated with Bromelain from Pineapple Peel Wastes

The pilling and shrinkage of wool fabrics are major problems in the textile industry. Chemical treatments are used to improve the performance properties of wool fabrics. These processes severely pollute the ecosystem. This study is aimed to use bromelain isolated from pineapple peel waste instead of toxic chemicals used during pretreatments to prevent shrinkage and minimize pilling in the woolen textile industry. Bromelain was isolated from pineapple peels using different techniques and isolated bromelain to be used was also encapsulated. Encapsulation was preferred to increase enzyme stability and reusability and to reduce cost. Area shrinkage, pilling, tensile strength, elongation, and weight loss tests were performed on the treated fabrics. According to the findings of this study, the isolated and encapsulated bromelain from pineapple peel wastes improved the washability of the wool fabric and eliminated the pilling problem. This developed method is sustainable, low cost, high added value, innovative, and environmentally friendly.

Microstructure, mechanical properties and corrosion resistance of direct energy deposited AlCu0.25CoCrFeNi2.1 high entropy alloy: Tailored by annealing heat treatment

In this study, a novel high entropy alloy AlCu0.25CoCrFeNi2.1 is additively manufactured by laser direct energy deposition process. The microstructure, mechanical properties and corrosion resistance of the prepared AlCu0.25CoCrFeNi2.1 high entropy alloy are investigated and tailored by annealing heat treatment. The results indicate the alloy exhibits a dual-phase microstructure with face-centered cubic (FCC) columnar dendrites and body-centered cubic (BCC) interdendritic structures. The annealing heat treatment facilitates the precipitation and coarsening of Cu-rich short rod-like B2 phase within the incipient FCC phase and the dissolution of incipient BCC phase, synergistically varying the proportion of FCC/BCC + B2 contents and tailoring the properties. The hardness of microstructure fluctuates under the coupling effect of precipitation strengthening and lattice distortion reduction and shows an overall downward trend with the increase of annealing time. The tensile properties are noteworthily improved within 6-h annealing and achieve a maximum ultimate tensile strength of 1156.4 MPa. After 8-h annealing, the ductility of the alloy obtains a maximum value of 30.3% with minor loss of ultimate tensile strength. The corrosion resistance is dramatically enhanced and obtains the best value after 2-h annealing, and then gradually deteriorates with the destroying of FCC matrix passive film phase by coarsened B2 phases. These results are of great importance in rapidly designing/manufacturing novel high entropy alloys by laser direct energy deposition process and tailoring microstructure, mechanical properties and corrosion resistance by annealing heat treatment.

Aging behaviour assessment of cellulosic fibres in alkaline media: A green technology approach in construction materials

With the increasing demand for buildings, the utilisation of green materials represents a novel approach toward achieving sustainable development goals. Cellulose-based materials, such as jute, exemplify eco-friendly substances for civil engineering applications. The present study aims at studying the aging behavior of jute fibers in an alkaline environment. For this purpose, three alkali environments (NaOH, KOH, Ca(OH)2) with three different concentrations were selected. Samples were treated at three different periods (7 d, 14 d, and 28 d) to assess the impact of treatment on the fiber properties. This study introduces a pioneering concept of the alkali treatment of jute-based fibres to evaluate tensile strength and weight loss, marking the first of its kind. This approach incorporates various characterisation techniques, including Differential Scanning Calorimetry (DSC), Thermo-Gravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) to assess the treatment process. In our experimental procedures, we evaluated key parameters such as the type of alkali, alkali concentration, and curing time for their influence on tensile strength. Subsequently, we applied Response Surface Methodology (RSM) in conjunction with bagging techniques to develop mathematical models based on the acquired data. Results demonstrated varied tensile strengths based on alkali type, concentration, and treatment duration. Fibres treated with 15 g/L concentration of NaOH exhibited an increase in tensile strength from 7 days (79.66 MPa) to 28 days (225.05 MPa). The highest tensile strength of jute fibres treated with KOH was observed with 15 g/L concentration at 14 days (237.58 MPa). For Ca(OH)₂ treatments, the highest tensile strength was observed with 30 g/L concentration at 14 days (111.28 MPa). It was also observed that prolonged exposure to very high alkali concentrations could adversely affect the tensile strength, as observed in the case of 30 g/L concentration of NaOH at 28 days (84.73 MPa). Among the various alkali materials tested, NaOH and KOH demonstrated greater effectiveness compared to Ca(OH)2. According to RSM analysis, the time of sample curing was found to be the most significant factor in tensile strength, with a P-value of 0.009. On average, the tensile strength changes by 54 %, 52 %, and 35 % for NaOH, KOH, and Ca(OH)₂, respectively, when the curing time shifts from 7 days to 28 days.

Fractional Lengthening of Forearm Flexor Tendons: A Cadaveric Biomechanical Analysis

Multiple procedures have been described for wrist and finger flexion contractures and spasticity. Fractional lengthening of forearm flexor tendons involves making parallel transverse tenotomies at the musculotendinous junction to elongate the muscle. Currently, there is limited literature to define the biomechanical consequences of this lengthening technique. Forty-eight flexor tendons were harvested from eight paired upper limbs including flexor carpi radialis, flexor carpi ulnaris, flexor pollicis longus, and flexor digitorum superficialis tendons. Each tendon that was lengthened was paired with the contralateral tendon as a control. A pair of transverse tenotomies were completed for the fractional lengthening. The first tenotomy was performed at the musculotendinous junction where the tendon narrowed to 75% of its maximal width. The second tenotomy was made 1 cm distal to the first. Tendon length was measured before and after fractional lengthening at a constant resting tension of 1 N. The maximum load at failure of each tendon and the mechanism of failure were each measured and compared with the contralateral side. After fractional lengthening, the mean increase in resting tendon length was 4 mm. When loaded to failure, the mean maximum load of fractionally lengthened tendons was 42% of the mean maximum load of intact tendons. All lengthened tendons failed at the distal tenotomy site. Fractional lengthening resulted in an increase of 3-6 mm (mean: 4 mm) in tendon length at resting tension. There was a significant loss in tensile strength and load to failure following fractional lengthening compared with an intact musculotendinous unit. The reduction in tensile strength following fractional lengthening results in loads at failure that are, in some cases, lower than the estimated forces required to perform basic tasks. Caution during the healing and rehabilitation period is warranted.