Density Polyurethane Foam Research Articles

Experimental investigation and soft bond modelling analysis on mechanical behaviours of foamed polyurethane solidified ballast

Polyurethane solidified ballasted track (PSBT) offers a novel solution to the frequent maintenance requirements of ballasted track, delivering a high-quality track infrastructure. In this study, laboratory tests were carried out on polyurethane solidified ballast (PSB) specimens under compression, tensile and shear conditions to obtain stress-strain curves and deformation characteristics. The numerical model of the PSB specimens was developed based on the discrete element method (DEM). The effects of the parameters related to the bond elongation on the tensile and compressive properties of the PSB specimens were analysed, and the parameters were calibrated by the test results. The results showed that the compressive, tensile and shear strengths of the specimens increased with increasing polyurethane foam density. During uniaxial and split loading, the stress-strain curves of the PSB specimens gradually entered the stress softening stage after an elastic phase. The compressive-tensile strength ratio of the specimens was around 1.55. From the perspective of deformation, the PSB specimen is primarily strained by the highly compressible polyurethane materials, and the specimen generates a considerable residual strain at the initial stage of cyclic loading. Thus, it is necessary to pre-compress the PSB to achieve an optimal load-bearing condition. DEM simulations show that there is a strong correlation between the mesoscale bond elongation of particles and the macroscopic tensile and compressive strengths of the specimens. It is therefore possible to utilise a high value of bond elongation to simulate bonded granular materials with low compressive-tensile strength ratios. The results obtained from the simulation of the numerical method used in this study are in high agreement with the test, which provides a new idea for revealing the meso- and macro- mechanical properties of PSB and its application in PSBT.

On the Crush Behavior and Energy Absorption of Sustainable Beverage Cans and Their Polyurethane Foam-Filled Structures: An Experimental Study.

In the pursuit of global energy conservation and emissions reductions, utilizing beverage cans as energy-absorbing components offers potential for a sustainable economy. This study examines the impact of foam filling on the crushing behaviors and energy absorption of various types of beverage cans. Quasi-static compression tests were conducted on five geometrically sized cans filled with three densities of polyurethane foam to study their deformation modes and calculate crashworthiness parameters within the effective stroke. Results show that empty beverage cans have lower energy absorption capacities, and deformation modes become less consistent as can size increases. Higher foam density leads to increased total energy absorption, a slight reduction in the effective compression stroke, and a tendency for specific energy absorption to initially increase and then decrease. Regarding crush behavior, smaller cans transition from a diamond mode to a concertina mode, while larger cans exhibit a columnar bending mode. Next, the coupling effect of energy absorption between foam and cans was analyzed so as to reveal the design method of energy-absorbing components. The specific energy absorption of smaller cans filled with polyurethane foam is superior to that of similar empty cans. These findings provide valuable insights for selecting next-generation sustainable energy absorption structures.

Thermal insulation properties of materials for fishing vessel coolboxes

Abstract Effective insulation is critical for traditional fishing boats because it helps to maintain the quality of the fish catch. Inadequate insulation can lead to significant economic losses for fishermen, as they may have to discard or sell the fish at a lower price. This study aimed to compare the thermal conductivity properties of three different insulation materials: Petung bamboo, polystyrene foam, and polyurethane foam. The experiment involved testing the density of the materials and conducting thermal conductivity tests. The results indicated that polyurethane foam is the best material for insulation because it has the lowest thermal conductivity value compared to laminated bamboo and polystyrene foam. The addition of more isocyanate mass fraction to the polyurethane foam material can increase its density and strength. This is because increasing the isocyanate concentration increases the cross-linking density of the foam, making it more durable and resilient. Moreover, higher density polyurethane foams exhibit lower heat conductivity, indicating better insulation qualities. This study highlights the importance of effective insulation to maintain the quality of the fish catch. The findings suggest that polyurethane foam, particularly with increased isocyanate concentration, is the most suitable material for insulation due to its superior insulation qualities.

Biomechanical Performance of a Novel Implant Design in Simulated Extraction Sites and Sinuslift Procedures

With increasing experience and in an attempt to shorten overall treatment times, implant placement in combination with tooth extractions and sinus lift procedures has become popular. In both cases, primary stability has to be achieved by either engaging apical and oral regions of trabecular bone or by engaging residual host bone beneath the sinus cavity. Extraction sites were formed by pressing a root analog into homogeneous low density polyurethane foam which was used as bone surrogate while a 3 mm thick sheet of medium density foam was used for mimicking a sinus lift situation. Two types (n = 10) of bone level implants with a conventional tapered design and a cervical back taper (NobelActive; control) and a novel design characterized by a shift in core diameter and thread geometry (AlfaGate; test) were placed in these models following conventional osteotomy preparation. Insertion torque was measured using a surgical motor and primary stability was determined by resonance frequency analysis. Statistical analysis was based on Welch two sample t tests with the level of significance set at α = 0.05. In sinuslifting, NobelActive implants required significantly higher insertion torques as compared to AlfaGate (p = 0.000) but did not achieve greater implant stability (p = 0.076). In extraction sites, AlfaGate implants showed both, significantly higher insertion torques (p = 0.004) and significantly greater implant stability (p = 0.000). The novel implant design allowed for greater primary stability when being placed in simulated extraction sockets and sinuslift situations. While in extraction sockets the position of condensing threads in combination with an increase in core diameter is beneficial, the deep cervical threads of the novel implant lead to superior performance in sinuslift situations.

Performance of foam-filled kirigami corrugated sandwich panels as sacrificial cladding against blast loads

In this study, the blast mitigation performance of kirigami corrugated (KC) panels filled with polyurethane foam as sacrificial cladding was investigated. Firstly, the effect of filling polyurethane (PU) foam on the energy absorption capacity and deformation mode of KC units was investigated by quasi-static compression. Numerical model was then built and validated. Following this, blast simulations were conducted to investigate the protective effectiveness of the aluminum foam panel, KC panel, and foam-filled KC panel as cladding for comparison. The blast loading effects on the structure without protection were also calculated and compared with different types of cladding. The key evaluating parameters, including peak transmitted load to the protected structure, energy absorption, and the crushed depth of the front plate, were used to evaluate the mitigation performance under various blast loads. The numerical results demonstrated the superior mitigating performance of foam-filled KC sandwich structures under various blast loading scenarios. The proposed foam-filled KC panel shows a higher energy absorption capacity than aluminum foam panels. The foam-filled KC panels with various densities of PU foam under different blast loads were also conducted to investigate its influence on blast mitigation performance. It was found that the second peak in the transmitted load can be reduced for KC panels with a higher density of the foam, as it leads to higher energy absorption capacity and later densification of the core against blast loads.

Experimental study of the effect of clay nanoparticles on the strength of hybrid sandwich panels under quasi-static loading

The aim of this study is to investigate the effect of clay nanoparticles on the strength of a hybrid sandwich structure with polyurethane foam core with two different densities. The sandwich structure is made of E-glass woven fabric and basalt fiber. Different percentages of clay nanoparticles are 0.0%, 0.1%, 0.3% and 0.5%, respectively. Furthermore, polyurethane foam with two densities of 40 and 140 (kg/m3) was used for the core of the sandwich structure. By force-displacement diagram obtained from quasi-static impact, the experimental studies of the effect of clay nanoparticles and polyurethane foam with different densities in this type of structure were performed. In addition, crashworthiness features including crush force efficiency and energy absorption capability were discussed. Finally, images of the damage surface and the cut view were taken and the results were reported in order to scrutinize the damage in the hybrid structure. The results indicate that with the increase of clay nanoparticles in the resin of the hybrid structure, the performance of the structure against the indenter effect is improved and displays good resistance. Furthermore, the strength of the structure is enhanced by increasing the density of polyurethane foam. Holistically, polyurethane foam prevents the spread of damage in all structures. In samples with foam with a density of 40 (kg/m3), the hybrid structure with 0.0% Nano absorbs more energy and in samples with foam with a density of 140 (kg/m3), has less energy absorption.

Investigation on the technology of soft recovery of fragment produced by metal cylindrical shell subjected to explosive loading

According to the requirements on the soft recovery of fragments of expanding cylindrical metal shells under explosion loading, this paper presents a recovery device combining low density polyurethane foam and water medium through theoretical analysis and numerical simulation. Compared to traditional recovery device designed with a single material, the combined recovery device can reduce the amplitude of impact pressure, which is produced by the initial interaction of low impedance polyurethane foam with high speed fragments, by about 1/3 compared to the impact pressure produced by water, and maintain the high decay rate of fragment speed. It can also make full use of the advantages of high density of water medium when the fragment speed is less than 0.5 km/s, which can reduce the decay thickness of the recovery device based on single polyurethane foam. Based on the device, the recovery experiment of expansion and fracture of 304 stainless steel cylindrical shell under explosive loading is carried out. Through the measurement of the wall velocity of the recovery tank and the appearance inspection after the experiment, it is implied that the wall and bottom of the recovery tank are in good condition and can be reused. According to the statistics of the recovered fragments, the recovery rate of the fragments is more than 85%, and the internal and external interfaces of fragments are highly recognizable, the turning blade lines on the surface of the fragments are clearly visible, and several non-penetrating cracks are visible, which verified that the impact damage of the recovery device to the fragments is significantly reduced. Acording to the fracture and surface information of the fragments, the approximate position of the fragments in the metal cylindrical shell is inferred.. Finally, the statistical results of the average thickness and mass distribution of the recovered fragments are given.

High-Strength and Low-Cost Biobased Polyurethane Foam Composites Enhanced by Poplar Wood Powder Liquefaction.

An environmentally friendly liquefaction of wood powder was prepared by atmospheric pressure liquefaction technology to replace the non-renewable petroleum polyols in the preparation of polyurethane foam composites. The liquefaction time varied from 0 min to 140 min. The composition of liquefied products and the effects of liquefaction time on the morphology, apparent density and mechanical properties of polyurethane foam composites were investigated. The results showed that the optimal process time for the preparation of wood powder liquefaction products, which could replace traditional petroleum polyols, was 110 min. At this time, polyether polyols are the main liquefaction products, with an average molecular weight in Mn reaching 237 and average molecular weight in Mw reaching 246. The functional group of the liquefied product consisted mainly of hydroxyl, with the highest content of 1042 mg KOH/g and the lowest acid number of 1.6 mg KOH/g. In addition, the surface of the polyurethane foam based on poplar wood is dominated by closed cell foam; thus its foam has good heat insulation and heat preservation properties. At 110 min liquefaction time, the apparent density of polyurethane foam is 0.164 g/cm3 and the compression strength is 850 kPa, which is higher than that of traditional polyurethane foam (768 kPa), which is without wood powder modification. Replacing petroleum polyol with renewable wood powder liquefaction products to prepare biomass-based polyurethane foam composite materials, researching complex chemical changes in different liquefaction stages, and finding the best liquefaction conditions are of great significance to optimize the performance of polyurethane, address the shortage of resources and reduce environmental pollution.

Dynamic crushing of a dedicated buffer during the high-speed vertical water entry process

A composite buffer has been designed to reduce the impact load of high-speed water entry projectile. Rigid Polyurethane (PU) foams of different densities have been used to make the damper of the buffer. A series of compression tests for PU foam specimens are implemented to obtain the stress-strain curves under different loading speeds. The constitutive model used in the simulation for PU foam has been validated by comparing the results with the experimental data. Six different failure modes have been found in the dynamic crushing process of the nose cap. The effects of PU foam density, the length of the nose cap on these failure modes are presented quantitatively by introducing a time-related non-dimensional number that represents the beginning time of each failure mode. The results show, the complete disintegration of the nose cap strongly depends on PU foam density, its effect is more pronounced in the cases when the ratio of the length of the buffer to the diameter of the projectile is greater than 0.92. The dedicated buffer is very efficient in reducing the impact load imposed in the cavitator of the projectile (the highest load-reducing ratio up to 51%).

The Influence of Neem Oil and Its Glyceride on the Structure and Characterization of Castor Oil-Based Polyurethane Foam.

Neem (Azadirachta indica) oil is a non-edible oil that contains azadirachtin, which can be used as a biopesticide. This study synthesizes bio-based polyurethane (PU) foam from neem and castor (Ricinus communis L.) oil at normal temperature and pressure. Neem oil can be reacted to narrow-distribution polyol by transesterification of oil and glycerol. Neem oil glyceride (NOG) can be used as polyol for bio-based PU foams and can be blended with castor oil homogeneously to reduce the cost of production. The composition of polyol was castor oil and 0 to 20% molar ratios of NOG. Hexamethylene diisocyanate trimer (Desmodur N) was used as isocyanate. The molar ratios of NCO/OH were set as 1.0, 1.5 and 2.0. The average hydroxyl contents of castor oil, neem oil and NOG were 2.7 mmol/g, 0.1 mmol/g and 5.1 mmol/g, respectively. The reaction time of bio-based PU foam could be adjusted between 5 to 10 min, which is acceptable for manufacturing. The densities of PU foams were between 49.7 and 116.2 kg/m3 and decreased with increasing NCO/OH and NOG ratios and decreasing neem oil. The ranges of specific compressive strength of foams were from 0.0056 to 0.0795 kPa·m3/kg. Increasing the NOG and neem oil ratio significantly enhanced the specific compressive strength in the low NCO/OH ratio. The solvent resistance and thermogravimetric (TG) results showed that the foams have high water and thermal stability. NOG can help to increase solvent resistance. Adding neem oil reduces the solvent resistance. The results indicated that increasing NCO/OH and NOG ratios increases the cross-linking density and hard segment content of PU foams. This investigation demonstrated that castor oil-based PU foams are improved by adding NOG to the polyol mixture. PU foam has excellent properties. Neem oil can be used in manufacturing processes to produce high-performance foams via a green synthesis process.

A calibration CT mini-lung-phantom created by 3-D printing and subtractive manufacturing.

We describe the creation and characterization of a calibration CT mini‐lung‐phantom incorporating simulated airways and ground‐glass densities. Ten duplicate mini‐lung‐phantoms with Three‐Dimensional (3‐D) printed tubes simulating airways and gradated density polyurethane foam blocks were designed and built. Dimensional accuracy and CT numbers were measured using micro‐CT and clinical CT scanners. Micro‐CT images of airway tubes demonstrated an average dimensional variation of 0.038 mm from nominal values. The five different densities of incorporated foam blocks, simulating ground‐glass, showed mean CT numbers (±standard deviation) of −897.0 ± 1.5, −844.1 ± 1.5, −774.1 ± 2.6, −695.3 ± 1.6, and −351.0 ± 3.7 HU, respectively. Three‐Dimensional printing and subtractive manufacturing enabled rapid, cost‐effective production of ground‐truth calibration mini‐lung‐phantoms with low inter‐sample variation that can be scanned simultaneously with the patient undergoing lung quantitative CT.

Impact of the Jatoba shell residue amount on polyurethane foams based on castor polyol

This study proposes an alternative for Jatoba shell residues as reinforcement in castor oil-based polyurethane (PU), obtaining an eco-friendly biocomposites. Biocomposites were obtained by mass mixing the polyol with the prepolymer (1:1) and reinforced from (0, 10, 15, and 20% wt) with Jatoba shell residues (JS). The alterations of morphology, thermal, and mechanical properties of the biocomposites were evaluated by varying the amount of fibers added to the PU. Flexural and impact tests showed an improvement on the mechanical properties, and scanning electron microscope images revealed a decrease in the average cell size of the foam, which caused an increase in the crosslinking density of PU foams due to the incorporation of additional groups of fibers, reacting with isocyanate groups. The fiber's addition to PU improved crystallinity, thermal stability, and presented high hydrophobicity. Thus, the developed biocomposites are an excellent option for environmental applications, such as industrial water purification and oil sorption.

Experimental investigation of pull-out performance of pedicle screws at different polyurethane (PU) foam densities.

Pedicle bone screws are one of the most critical materials used in spinal orthopaedic operations. Screw loosening and pull-out (PO) are basic complications encountered during or after surgery. Pull-out Strength (POS) of the bone is one of the significant parameters to understand the mechanical behaviour of a screw fixed to poor quality or osteoporotic bone. This study investigates how the POS of a pedicle screw is affected by the factors of the screw diameter and the polyurethane (PU) foam density by experimental analysis. In the experiments, two different diameter (5.5 and 6.5 mm) of conical pedicle screws and five different density (0.08, 0.16, 0.24, 0.32 and 0.48 g·cm-3) PU foams were used. According to the force-displacement curves obtained from experimental results, the POS increased with the increases in screw diameter and PU foam density.

Influence of cellulose fibers extracted from pineapple (Ananas comosus) leaf to the mechanical properties of rigid polyurethane foam

The influence of cellulose fibers extracted from pineapple (Ananas comosus) leaf fibers on polyurethane foam’s mechanical properties (PUF) is reported. The PUFs were reinforced with different weight ratios (1, 3, and 5 wt%) of cellulose fibers. The surface morphology of the extracted cellulose fibers was determined using a scanning electron microscope (SEM). The functional groups and vibrational modes of the reinforced PUFs were measured using Fourier transform infrared spectroscopy (FTIR). The influence of cellulose fibers to the density and mechanical property of the PUFs were also investigated using universal testing Machine (UTM). Experimental results showed the absence of hemicellulose, lignin, and other soluble materials present in the pineapple leaves after alkaline treatment, suggesting high-quality cellulose fibers. Likewise, FTIR spectra revealed the presence of typical urethane linkages of PUFs suggesting the successful formation of PUFs with a varied amount of cellulose fibers. The mechanical properties of the PUFs with an increasing amount of cellulose fibers exhibit a decrease of the compressive strength of the fabricated PUFs may be due to the lack of cross-linking between the cellulose fibers and PUFs that will influence the reactivity in the system that eventually affects the polyurethane foam density expansion.

Enhanced mechanical strength of talc-containing porous kaolin prepared by a replica method

Recently, porous ceramics have received much interest in various applications, finding use in membranes, thermal insulation, catalytic substrates, and gas burner media owing to their outstanding thermal stability and chemical stability. To fabricate porous ceramics, many processing methods can be used. Particularly, reticulated porous ceramics prepared by the replica method are worthy of attention given their interconnected open pores with high porosity and a low pressure drop. Therefore, many researchers have studied reticulated porous ceramics using various raw materials, such as alumina, mullite, silicon carbide, cordierite and partially stabilized zirconia. However, there are few reports about reticulated porous ceramic based on kaolin, which is a low-cost raw material that can be sintered at low temperature. In this study, reticulated porous kaolin is fabricated via the replica method. To tailor the mechanical properties of the reticulated porous kaolin, the pore density of polyurethane foam (10–80 PPI (Pores Per Inch)) and the sintering temperature (1000–1300 ℃) of the kaolin slurry-coated polyurethane foams are controlled. To characterize the kaolin, scanning electron microscopy (SEM), mercury porosimetry, high-resolution micro-computed tomography (µCT), and a universal testing machine were used. When the reticulated porous kaolin with a pore density of 60 PPI was sintered at 1300 ℃, it showed compressive strength of 1.23 MPa.

Osseodensification Drilling vs. Standard Protocol of Implant Site Preparation: An In Vitro Study on Polyurethane Foam Sheets

(1) Background: The aim of the present in vitro investigation was to evaluate, on polyurethane sheets, two different drilling techniques for dental implant positioning using osteocondensing burs compared to a standard type protocol. (2) Methods: Three different implant designs (Implacil De Bortoli UN III 4 × 10 mm, Restore RBM 4 (HEX) × 10 mm; Implacil De Bortoli UN II 4 × 10 mm) were evaluated (test implant (osteocondensing drills) and control implant (standard drills)). The insertion torque (IT), the removal torque (RT) and the resonance frequency analysis (RFA) values of test and control implants inserted in different size and different density polyurethane foam models were compared for 120 experimental sites. Accordingly, 120 experimental holes were produced in different PCF polyurethane foams: 60 sites were produced in 10 PCF sheets and 60 sites in 10 PCF sheets with an additional 1 mm layer of 30 PCF. (3) Results: The IT, removal torque and RFA values were significantly higher for both of the evaluated implants, in the sites prepared with the osteocondenser drills when compared to sites prepared with standard drills (p < 0.05). The UNII and UN III showed significantly higher stability compared to the HEX implant; these differences increased drastically in the 10 PCF Polyurethane Block with the additional 1 mm cortical layer (p < 0.05). (4) Conclusions: The outcome of this investigation suggested a possible clinical application of osteocondensing burs in case of reduced bone quality and quantity in the posterior maxilla.

Sound absorption and compressive property of PU foam‐filled composite sandwiches: Effects of needle‐punched fabric structure, porous structure, and fabric‐foam interface

The flexible polyurethane (PU) foam‐filled composite sandwiches are constructed using three types of needle‐punched fabrics (upper layer), PU foam (core layer), and nylon (bottom layer). Different contents of deionized water were used to adjust the pore size and bulk density of PU foam by free‐foaming. Effects of needle‐punched fabric components, cell structure, and fabric‐foam interface on sound absorption and compressive property of the composite sandwiches were investigated. Fabric‐foam interface contributes to improve high‐frequency sound absorption efficiency. When containing 0.5 wt% water in the core and nylon‐glass grid needle‐punched composite fabric (NPUN‐G) in the upper face, the composite sandwiches exhibited optimal sound absorption of 0.78 at low frequency of 450 Hz, and optimal compressive strength of 14.4 kPa. Combination of needle‐punched composite fabric improved the sound absorption coefficient and compressive strength, as high as 223% and 121%, respectively, compared with pure PU foam. This study provided an important basis for the preparation of high‐strength composite sandwiches with low‐frequency sound absorption.

Short vs. Standard Length Cone Morse Connection Implants: An In Vitro Pilot Study in Low Density Polyurethane Foam

The aim of the investigation was to evaluate the insertion torque, pull-out torque and implant stability quotient (ISQ) of short implants (SI) and standard length implants (ST) inserted into linearly elastic and constitutive isotropic symmetry polyurethane foam blocks. Short dental titanium implants with a Cone Morse connection and a conical shape (test implants: Test Implant A—diameter 5.5 mm and length 6 mm) (Test Implant B—diameter 5.5 mm and length 5 mm) were used for the present in vitro investigation. ST implants (4 mm diameter and 10 mm length), with a Cone Morse connection and a conical shape, were used as Control Implant A and as Control Implants B. These two latter implants had a different macro design. A total of 20 implants (5 Test A, 5 Test B, 5 Control A and 5 Control B) were used for the present research. The results were similar when comparing the Test A and Test B implants. The test implants had very good stability in polyurethane 14.88–29.76 kgm3 density blocks. The insertion torque values were very high for both types of test implant (25–32 Ncm on 14.88 kgm blocks, and up to 45 Ncm in 29.76 kgm3 blocks). The pull-out test values were very similar to the insertion torque values. The ISQ values were significantly high with 75–80 in 14.88 kgm3 blocks, and 78–83 in 29.76 kgm3 blocks. No differences were found in the values of the Control A and Control B implants. In both these implants, the insertion torque was quite low in the 14.88 kgm3 blocks (16–28 Ncm). Better results were found in the 29.76 kgm3 blocks. The pull-out values for these control implants were slightly lower than the insertion torque values. High ISQ values were found in both control implants (57–80). When comparing SI and ST implants, the SI had a similar if not better performance in low quality polyurethane foam blocks (14.88–29.76 kgm), corresponding to D3 and D4 bone.

Study on the protective properties of polyurethane foam for water-entry projectile

When the projectile enters into the water at high velocity, the impact force will be huge, therefore, it is necessary to protect the projectile. In this paper, polyurethane foam is selected to study its protective properties for water-entry projectile. The water-entry test was designed to compare the numerical simulation results, in order to verify the feasibility and the validity of the model. In particular, the numerical simulation method was used to compare the motion and response characteristics of unprotected and protected projectile. The results demonstrated that the polyurethane foam has good protective properties and comparing the protective effect of different density polyurethane foam by numerical simulation methods, it can be seen that the better protection is achieved at a density of 0.17 g/cm3 and 0.40 g/cm3.

Feasibility of using tapping torque during lumbar pedicle screw insertion to predict screw fixation strength

BackgroundRigid pedicle screw fixation is mandatory for achieving successful spinal fusion; however, there is no reliable method predicting screw fixation before screw insertion. The purpose of the present study was to investigate the efficacy of measurement of tapping torque to predict pedicle screw fixation. MethodsFirst, different densities of polyurethane foam were used to measure tapping torque. The insertional torque during pedicle screw insertion and axial pullout strength were measured and compared between under-tapped and same-tapped groups. Next, for in vivo study, the tapping and insertional torque of lumbar pedicle screws using the cortical bone trajectory technique were measured intraoperatively in 45 consecutive patients. Then, correlations between tapping torque, the bone mineral density of the femoral neck and lumbar vertebrae, and insertional torque were investigated. ResultsEx vivo tapping torque significantly correlated with the insertional torque and pullout strength regardless of tapping sizes (r = 0.98, p < 0.001). The mean in vivo tapping and insertional torque were 1.48 ± 0.73 and 2.48 ± 1.25 Nm, respectively (p < 0.001). Insertional torque significantly correlated with tapping torque and two BMD parameters, and the correlation coefficient of tapping torque (r = 0.83, p < 0.001) was higher than those of femoral neck BMD (r = 0.59, p < 0.001) and lumbar BMD (r = 0.39, p < 0.001). ConclusionsTapping torque is a reliable predictor of pedicle screw fixation and allows surgeons to improve the integrity of the bone-screw interface by making modification prior to actual screw insertion.