Search Results (51)

Articular fractures require precise anatomical reduction and rigid fixation to heal appropriately. In veterinary cases that involve fracturing of the lateral humeral condyle, cortical bone screws inserted in lag fashion with Kirschner wire are the preferred method for surgical fixation. However, relatively high complication rates associated with cortical lag screws (CLSs) highlights the need to investigate alternate screw designs. Variable-pitch headless compression screws (VPHCSs) are unique as they advance beneath the cortical surface. Although the use of VPHCSs are widely utilised in human orthopaedics, the current use in veterinary orthopaedics is limited. This study aimed to evaluate the peak interfragmentary force (PIF) and area of compression (AOC) generated by a 3.5 mm self-tapping cortical screw placed in lag fashion and a 3.5 mm VPHCS inserted to four depths. PIF and AOC were measured using a pressure-sensitive film placed between two blocks of polyurethane foam (0.24 g/cm³), simulating a transverse fracture. CLSs were inserted by hand into predrilled 2.5 mm pilot holes. PIF and AOC were measured at full insertion. VPHCSs were placed into predrilled 2.5 mm pilot holes, followed by a 3.5 mm tapered countersink. The screw was inserted until the head was level with the surface. PIF and AOC were measured between the two blocks. The screw was continued until the head was at a depth of 2, 5, and 9 mm below the surface, and the PIF and AOC were measured again at each stage. There was no detectable difference in PIF and AOC between CLSs and VPHCSs countersunk to −2 mm (PIF–CLS: Mean = 12.886, SD = 2.370; 2 mm: Mean = 17.301, SD = 8.858, p = 0.319; AOC–CLS: Mean = 0.936, SD = 0.291; 2 mm: Mean = 0.925, SD = 0.447, p = 0.872). VPHCSs countersunk to −5 mm and −9 mm produced significantly greater PIF compared to CLSs (5 mm: Mean = 16.086, SD = 6.799, p = 0.002; 9 mm: Mean = 34.987, SD = 4.015, p < 0.001). VPHCSs countersunk to −5 and −9 mm produced significantly greater PIF and AOC compared to CLSs in this model. Further investigation is required to produce recommendations for clinical use. Full article

Benefiting from their outstanding porosity, considerable specific surface area, and natural flexibility, cellulose nanofibers (CNFs)/MOF materials have emerged as competitive candidates for advanced flexible energy storage devices. However, conventional CNFs/MOFs aerogels or films often suffer from poor recoverability under compression, bending, and folding, accompanied by severe plastic deformation that compromises the cycling and structural stability of devices. To address this issue, we report a rationally designed flexible PU/CNFs/ZIF-8/PANI composite foam with an interconnected micro-mesoporous structure. Using polyurethane foam as a soft substrate and CNFs/ZIF-8 as building blocks, the composite was fabricated through a combined strategy of impregnation, in situ ZIF-8 growth, hot-pressing, and in situ aniline polymerization with simultaneous etching of the ZIF-8. The incorporation of carboxylated CNFs enhances the hydrophilicity of the PU skeleton. This, in combination with the hot-pressed framework, establishes an interconnected 3D network, thereby effectively preventing the agglomeration of active materials. Meanwhile, the hierarchical pores derived from the sacrificial ZIF-8 template provide abundant electroactive sites, accelerate ion transport, and facilitate high PANI loading. By virtue of this synergistic architectural effect, the resultant electrode achieves a high specific capacitance of 449 F/g at 0.2 A/g, with 97% capacitance retention after 2000 cycles at 5 A/g. Furthermore, the composite foam demonstrates excellent mechanical flexibility, with a tensile strength of 0.87 MPa and an elongation at break of 230%. This work offers a feasible approach for developing high-performance flexible supercapacitors and provides novel perspectives for the rational design of portable energy storage devices. Full article

Rigid polyurethane foams are often manufactured in sealed molds, so knowledge of the density distribution in the molded blocks is essential. A study was conducted with the aim to estimate density distribution within a rigid polyurethane foam block (average core density of ≈96 kg/m³) manufactured in a rectangular sealed mold. The density of 150 rectangular samples was determined experimentally. Characteristic locations of the foams’ columns in the block were outlined, having similar foaming conditions. Averaged density in the characteristic columns was calculated for each characteristic location. A mathematical model was developed based on density data of characteristic columns, approximated with second- and third-degree polynomials. Density distribution was calculated, and corresponding color charts with density zones and equidensity lines were constructed for six horizontal and two vertical sections of the block. It was found that the common center of the elliptical equidensity lines is located asymmetrically, ≈17 mm above the geometric center of the untrimmed block. Density gradients were calculated in directions parallel and perpendicular to the foams’ rise direction. The developed mathematical model allowed us to estimate density distribution within the rigid polyurethane foam block manufactured in a rectangular sealed mold. Full article

Adequate ridge width and thermal control are critical for predictable implant site preparation. This in vitro study compared conventional osteotomy (CO), osseodensification (OD), and OsseoShaper (OS) protocols in standardized polyurethane foam blocks simulating narrow D2 ridges. A total of 18 osteotomies (n = 6 per group) were prepared under protocol-specific irrigation. Ridge width was measured at 3, 6, and 9 mm apical to the crest before and after osteotomy using a digital caliper, and expansion (ΔW) was calculated. Intraoperative thermal changes (ΔT) were recorded in real time with an infrared thermal camera. OD achieved consistent expansion at all depths (p < 0.05), while OS produced significant widening at the 3 and 6 mm levels; CO yielded only a minor but significant gain at the 3 mm level. At the intergroup level, OS showed significantly greater crestal expansion than CO at 3 mm (p = 0.006). All protocols generated comparable thermal changes (mean ΔT 7.4–8.2 °C), remaining well below the critical 47 °C threshold. Within the limitations of this in vitro model, OD and OS enhanced ridge expansion compared with CO, particularly at the crestal level, where expansion is most critical. All protocols maintained thermally safe profiles, supporting their clinical applicability. Full article

Achieving reliable implant stability in type IV (D4) bone remains a clinical challenge due to its thin cortical plates and low trabecular density, which increase the risk of early failure. Novel osteotomy techniques such as osseodensification and the OsseoShaper have been proposed, yet their effects when combined with different implant macrogeometries are not fully understood. This in vitro study evaluated forty osteotomies in standardized polyurethane foam blocks simulating D4 bone density. Three site preparation protocols—conventional osteotomy, osseodensification, and OsseoShaper—were combined with two implant macrogeometries (parallel-walled conical and tri-oval tapered designs). Insertion torque (IT) was measured using a calibrated digital torque meter, and implant stability was assessed by resonance frequency analysis (ISQ). Intraoperative thermal changes were monitored with infrared thermography under constant irrigation. Statistically significant differences were observed among groups (p < 0.05). Osseodensification with parallel-walled implants achieved the highest stability, whereas osseodensification with tri-oval implants showed the lowest. Although osseodensification produced the greatest thermal increase, all values remained below the 47 °C osteonecrosis threshold. Within the study’s limitations, both the osteotomy technique and implant macrogeometry significantly affected stability and thermal outcomes, with osseodensification plus parallel-walled implants providing the most predictable performance in D4 bone. Full article

We present a case of unexpected proximal displacement of an intramedullary pin (IMP) during plate–rod repair of a femoral fracture caused by minimally invasive plate osteosynthesis (MIPO), requiring immediate revision. Implant retrieval analysis and ex vivo modelling were performed to characterise the technique failure mode. The case details are reported. Implant retrieval analysis consisted of stereo zoom microscopic examination of the retrieved IMP. Wear patterns formed by conflict with a 2.8 mm, two-fluted surgical drill bit and a 3.5 mm AO locking screw were replicated using a simple paper impression model. The mechanism of pin movement was replicated in a benchtop laminated polyurethane foam block model, and wear patterns produced during drilling and screw insertion were characterised using stereo zoom. The wear pattern visible on the retrieved IMP suggested axial displacement caused by a rack-and-pinion-like mechanism, enacted by contact with either the drill bit or locking screws during placement of the repair construct. Significant axial displacement of the IMP due to conflict with screws during construct placement is possible during the placement of plate–rod fixation. Surgeons should confirm implant positioning if implant conflict is recognised intra-operatively. Full article

Background: Primary implant stability is a critical factor for successful osseointegration and long-term implant success. This study investigates the impact of drilling protocol modifications on primary stability, considering different bone qualities and implant macro-designs, lengths, and diameters. Material and Methods: Three implant designs—two parallel-walled and one tapered—were tested with diameters ranging from 3.4 to 5.2 mm and lengths from 7.5 to 14.5 mm. Implants were placed in polyurethane foam blocks simulating different bone densities (10, 15, 25, and 35 PCF). A standard drilling protocol was used in all groups, with modifications based on bone quality: overpreparation in dense bone and underpreparation in softer bone. Primary stability was evaluated using insertion torque (IT). The optimal IT range was defined as 25–50 Ncm, based on clinical guidelines for immediate loading. The influence of drilling protocol adaptations on stability parameters was assessed. Results: Insertion torque was primarily influenced by bone density and implant diameter, with implant length playing a minor role. In dense bone (D1, D2), underpreparation improved torque values, especially in smaller implants, while overpreparation reduced them. The highest torques occurred with 5.2 mm implants, sometimes exceeding 80 Ncm. Standard protocols did not consistently achieve optimal torque across implant types. In soft bone (D3), underpreparation—particularly with tapered implants—was modestly beneficial. In very soft bone (D4), none of the protocols reliably reached the desired torque range. Conclusions: Adapting drilling protocols to bone density improves insertion torque, especially with wider implants and in denser bone. Underpreparation is generally more effective than overpreparation. However, in very soft bone, neither implant geometry nor drilling adaptations reliably achieve optimal primary stability, highlighting the need for additional strategies. Full article

Polyurethane foam is widely used as a primary filling material in car seats. While it provides good damping and energy absorption, the mechanical properties are complex but play a vital role in vibration attenuation and vehicle ride comfort. This study proposes a comprehensive experimental and analytical method to characterize the visco-hyperelastic properties of seat-grade polyurethane foam. Quasi-static and dynamic compression tests were conducted on foam blocks to obtain load–deflection curves and dynamic stiffness. A visco-hyperelastic material model was developed, where the hyperelastic response was derived via the hereditary integral and difference-stress method, and viscoelastic behavior was captured using a Prony series fitted to dynamic stiffness data. The model was validated using finite element simulations, showing good agreement with experimental results in both static and dynamic conditions. The proposed method enables accurate characterization of the visco-hyperelastic material properties of seat-grade polyurethane foam. Full article

To investigate the impermeability of foam concrete in various challenging environments, this study evaluates its water resistance by measuring the water contact angle and water absorption. Polyurethane (PU) was used to fabricate polyurethane foam concrete (PFC), enabling a monolithic hydrophobic modification to improve the permeation performance of foam concrete. The study also examines the effects of carbonation and freeze–thaw environments on the permeation resistance of PFC. Graphene oxide (GO), KH-550, and a composite hydrophobic coating (G/S) consisting of GO and KH-550 were employed to enhance the permeation resistance of PFC through surface hydrophobic modification. The functionality of the G/S composite hydrophobic coating was confirmed using energy dispersive X-ray spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). The results showed the following: (1) The water contact angle of PFC increased by 20.2° compared to that of ordinary foam concrete, indicating that PU-based hydrophobic modification can significantly improve its impermeability. (2) After carbonation, a micro–nano composite structure resembling the surface of a lotus leaf developed on the surface of PFC, further enhancing its impermeability. However, freeze–thaw cycles led to the formation and widening of microcracks in the PFC, which compromised its hydrophobic properties. (3) Surface hydrophobic modifications using GO, KH-550, and the G/S composite coating improved the anti-permeability properties of PFC, with the G/S composite showing the most significant enhancement. (4) GO filled the tiny voids and pores on the surface of the PFC, thereby improving its anti-permeability properties. KH-550 replaced water on the surface of PFC and encapsulated surface particles, orienting its R-groups outward to enhance hydrophobicity. The G/S composite emulsion coating formed a hydrophobic silane layer inside the concrete, which enhanced water resistance by blocking water penetration, reducing microscopic pores in the hydrophobic layer, and improving impermeability characteristics. Full article

The key challenge in polymer science is developing sustainable synthesis methods using renewable feedstocks. This study explores plant-derived diarylheptanoids with various structures as the building blocks for polyurethane (PU) materials. Diarylheptanoid glucosides isolated from black alder (Alnus glutinosa) bark were hydrolyzed and fractionated to remove sugar moieties. The resulting diarylheptanoids, along with unhydrolyzed analogues and curcumin, were used as biomass-based polyols to synthesize model PU films. Incorporating diarylheptanoids enhanced the mechanical strength and reduced the flexibility of PU due to increased crosslinking, with effects proportional to the OH functionality of the biomass-based polyols. Weight loss, FTIR, and Py-GC-MS/FID analyses revealed that the catechol moieties and the glucosidic bonds are biodegradable structural subunits of diarylheptanoids incorporated into PU films. Rigid polyurethane foams (PURs) incorporating high-OH-functionality diarylheptanoid glucosides such as oregonin demonstrated significantly higher compression strength and less weight loss during non-isothermal thermal analysis in air compared to those of commercial polyol-based foams. A cone calorimeter test showed that the PUR foam with diarylheptanoid derivatives had a lower degradation rate, a longer flame-burning time, 30% less heat emission, and 25% less smoke, indicating improved flame retardancy. Adding 1–2% oregonin-enriched black alder bark extracts to commercial Elastopir 1132/509/0 PUR foam significantly improved its resistance to thermal oxidative aging, outperforming the commercial antioxidant Irganox. Full article

Three fungal strains were employed for the stereoselective oxidation of the cheap and commercially available substrate 2-phenylethanol, which resulted in chiral building blocks being received. The whole-cell biocatalysts were as follows: Beauveria bassiana DSM 1344, Beauveria brongniartii DSM 6651, and Rhizopus arrhizus DSM 1185. The main product of Beauveria bassiana bioconversion was 1-phenylethane-1,2-diol, obtained, depending on the form of the biocatalyst, as an R-enantiomer (e.g., 99.9%) with fresh biomass application or as a racemic mixture in cases of immobilization in agar-agar. The best and most innovative results for the synthesis of the R-enantiomer of diol were received under precisely defined conditions as a result of a scaling study conducted on an automatic batch reactor. This is a pioneering result, since, in previous studies, fresh mycelium of Aspergillus niger resulted in this product being received as the (S) enantiomer. Also, the use of Rhizopus arrhizus DSM 1185 (immobilized in polyurethane foams) presented important results, as the bioconversion of phenyl ethanol led, indeed, to the racemic mixture of 1-phenylethane-1,2-diol but was accompanied by a noticeable tyrosol synthesis, which had not been reported previously. Full article

Polyurethane (PUR) soft foams release malodorous and potentially toxic compounds when exposed to oxidative conditions. Current chamber test methods cannot distinguish between pre-existing volatiles and those formed during oxidation, nor can they assess the formation rates of oxidation products. We subjected PUR soft foam to oxidative treatment in a continuous air flow at 120 °C. Emissions were convectively transferred from the foam to an exhaust port and analyzed using a thermodesorption–gas chromatography–mass spectrometry (TD-GC-MS) system, with external calibration employed for the quantification of selected analytes. The study identified hydroperoxide formation and degradation as key mechanisms in the breakdown of the polyether soft segments. This process predominantly produces volatiles, such as carboxylic acids, formates, acetates, alpha-hydroxy-ketones, (unsaturated) aldehydes, substituted dioxolanes and dioxanes, glycols, and allyl ethers. Volatiles associated with the degradation of the hard segments include aniline, benzoxazole, 2-methylbenzoxazole, and benzaldehyde. This experimental setup enables reproducible qualitative and quantitative analysis of volatiles formed during the oxidative degradation of PUR soft foams, providing new insights into the segment-dependent chemical pathways of the polymer’s molecular breakdown. Full article

Background: While titanium implants are widely recognized for their clinical success, zirconia implants have emerged as a metal-free alternative. This study aimed to evaluate the influence of zirconia implant macrogeometry and bone density on primary implant stability. Methods: Two types of zirconia implants were tested—the Neodent^® Zi Ceramic Implant and the Straumann^® PURE Ceramic Implant, that were placed into polyurethane foam blocks mimicking different bone densities (10 PCF, 15 PCF, 20 PCF, 30 PCF, and 40 PCF). Each implant type was inserted and removed multiple times, with primary stability measured using resonance frequency analysis via the Osstell^® Beacon device. Statistical tests, including the Shapiro–Wilk test, t-tests, the Mann–Whitney U test, and the Kruskal–Wallis test, were applied, with significance set at 5% (p < 0.05). Results: The tapered Neodent^® Zi Ceramic Implant consistently showed higher ISQ values across all foam densities compared to the Straumann^® PURE Ceramic Implant (p = 0.035). Additionally, lower-density foams exhibited lower stability scores (p < 0.05). Conclusion: The study concludes that both the macrogeometry of zirconia implants and bone density significantly affect primary implant stability. Specifically, tapered implants demonstrated higher stability than cylindrical designs, suggesting that implant macrogeometry and bone density should be considered for optimal primary stability in clinical settings. Full article

Recycling flexible polyurethane foam (F-PUF) scraps is difficult due to the material’s high cross-linking structure. In this work, a wedge-block-reinforced extruder with a considerable enhanced shear extrusion and stretching area between the rotating screw and the stationary wedge blocks was utilized to recycle F-PUF scraps into powder containing surface-active hydroxyl groups. The powder was then utilized for the quantitative replacement of polyol in the foaming process. Characterizations showed that the continuous shear extrusion and stretching during the extrusion process reduced the volume mean diameter (VMD) of the F-PUF powder obtained by extruding it three times at room temperature to reach 54 μm. The -OH number (OHN) of the powder prepared by extruding it three times reached 19.51 mgKOH/g due to the mechanochemical effect of the powdering method. The F-PUF containing recycled powder used to quantitively replace 10 wt.% polyol was similar in microstructure and chemical structure to the original F-PUF, with a compression set of 2%, indentation load deflection of 21.3 lbf, resilience of 43.4%, air permeability of 815.7 L/m²·s, tensile strength of 73.0 Kpa, and tear strength of 2.3 N/cm, indicating that the recycling method has potential for industrial applications. Full article

The flammability of rigid polyurethane foam (RPUF) limits its application. A new type of chitosan phase-change microcapsule (CS/PCM) was successfully prepared by the condensation method with chitosan and gum acacia as the wall material and paraffin as the core material. CS/PCM was introduced into RPUF composite material as filler to improve the thermal and flame-retardant properties of polyurethane. The morphology, structure, thermal properties and flame retardancy of the materials were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and cone calorimetry. It is found that when the CS/PCM content is 30 wt%, the latent heat of phase transition of RPUF-30 is 12.308 J/g, the limiting oxygen index (LOI) is 26.1% and the fire risk is reduced. The flame-retardant mechanism shows that the barrier effect provided by chitosan plays an important role in effectively blocking the transfer of heat and combustible gas, and improving the flame-retardant property of the composite. This paper provides a new idea for the application of CS/PCM in RPUF. Full article