scholarly journals The Dynamic Viscoelasticity of Dental Soft Polymer Material Containing Citrate Ester-Based Plasticizers

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5078
Author(s):  
Guang Hong ◽  
Wei-qi Wang ◽  
Lu Sun ◽  
Jian-min Han ◽  
Keiichi Sasaki
Keyword(s):  
Polymer Material ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Polymer Materials ◽  
Significance Level ◽  
Dynamic Viscoelasticity ◽  
Methacrylate Polymers ◽  
Significant Difference ◽  
Tan Δ ◽  
Soft Polymer

The aim of this study was to investigate the dynamic viscoelasticity of dental soft polymer material containing citrate ester-based plasticizers. Three kinds of citrate ester-based plasticizer (Citroflex® C-2: TEC, Citroflex® A-2: ATEC, and Citroflex® A-4: ATBC), with the combination of 5 wt% ethyl alcohol, were used as the liquid phase. The dynamic viscoelastic properties of nine ethyl methacrylate polymers: (A, B, C, D, E, F, G, H, and I) were immersed in 37 °C distilled water for 0, 1, 3, 7, 14 and 30 days, respectively. The dynamic viscoelastic properties were measured at 37 °C with an automatic dynamic mechanical analyzer. The shear storage modulus (G′), shear loss modulus (G″), and loss tangent (tan δ) were determined at 1 Hz. These parameters were statistically analyzed by two-way and one-way ANOVA and Tukey’s multiple comparison test at a predetermined significance level of 0.05. A significant difference was found among the materials in terms of the dynamic viscoelasticity. The materials containing citrate ester-based plasticizer ATBC showed the most stable dynamic viscoelasticity. Considering the limitations of this study, the results suggest that the inclusion of citrate ester-based plasticizer can improve the durability of dental soft polymer materials.

Dynamic Viscoelasticity of a Magnetorheological Fluid in Oscillatory Slit Flow

1999 ◽  
Vol 13 (14n16) ◽  
pp. 2068-2076 ◽  
Author(s):  
Masami Nakano ◽  
Hideki Yamamoto ◽  
Mark R. Jolly
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Strain Amplitude ◽  
Loss Modulus ◽  
Plastic Property ◽  
Mr Fluid ◽  
Dynamic Viscoelasticity ◽  
Slit Flow ◽  
Tan Δ

The nonlinear dynamic viscoelasticity of an MR fluid in oscillatory slit flow under magnetic flux normal to the flow has been investigated by using a newly developed oscillatory pressure flow type rheometer. An MR fluid consisting of micron-sized, magnetically polarizable particles dispersed into a carrier medium is evaluated. The dynamic viscoelasticity remarkably depends on a fluid strain amplitude and a magnetic field strength. Both of the storage modulus (G′) and loss modulus (G″) increase dramatically with the increase of applied magnetic field strength H from 0 to 160 kA/m. And for the increase of the strain amplitude, both of them dramatically decrease, while the loss tangent ( tan δ) increases remarkably, showing the dominance of viscoelastic plastic property. The above results are discussed in terms of three deformation regions of the MR fluid; pre-yield, yield, post-yield.

scholarly journals The effect of crude drugs on the angiogenic property and dynamic viscoelasticity of PEMA-based soft polymer materials

2017 ◽  
Vol 36 (6) ◽  
pp. 770-777
Author(s):  
Wei-Qi WANG ◽  
Guang HONG ◽  
Jian-Min HAN ◽  
Hiroshi MURATA ◽  
Keiichi SASAKI
Keyword(s):  
Polymer Materials ◽  
Dynamic Viscoelasticity ◽  
Crude Drugs ◽  
Soft Polymer

scholarly journals The effect of addition of selected carrageenans on viscoelastic properties of model processed cheese spreads

2007 ◽  
Vol 55 (5) ◽  
pp. 51-58
Author(s):  
Michaela Černíková ◽  
František Buňka ◽  
Vladimír Pavlínek ◽  
Pavel Březina ◽  
Jan Hrabě ◽  
...  
Keyword(s):  
Viscoelastic Properties ◽  
Dry Matter ◽  
Loss Modulus ◽  
Aqueous Dispersion ◽  
Matter Content ◽  
Reference Frequency ◽  
Dry Matter Content ◽  
Powder Form ◽  
Processed Cheese ◽  
Tan Δ

The effect of 0.25% w/w κ-carrageenan and ι‑carrageenan on viscoelastic properties of processed cheese were studied using model samples containing 40% w/w dry matter and 45 and 50% w/w fat in dry matter. Experimental samples of processed cheese were evaluated after 14 days of storage at the temperature of 6 ± 2 °C. Basic parameters of processed cheese samples under study (i.e. their dry matter content and pH) were not different (P ≥ 0.05). There were no statistically significant differences in values of storage modulus G´ [Pa], loss modulus G'' [Pa] and tangent of phase shift angle tan δ [-] for the reference frequency of 1 Hz between processed cheese with κ‑carrageenan applied in the form of powder and in the form of aqueous dispersion (P ≥ 0.05). The addition of 0.25% w/w κ‑carrageenan and ι‑carrageenan (in the powder form) resulted in an increase in storage (G´) and loss (G'') moduli and a decrease in values of tan δ (P < 0.05). As compared with control (i.e. without added carrageenans), samples of processed cheese became firmer. Iota-carrageenan added in the powder form in concentration of 0.25% w/w showed a more intensive effect on the increase in firmness of processed cheese under study than κ‑carrageenan (P < 0.05).

Dynamic Viscoelastic Characterization of Bulk-fill Resin-based Composites and Their Conventional Counterparts

2020 ◽  
Vol 45 (2) ◽  
pp. 173-182 ◽  
Author(s):  
AU Yap ◽  
AH Eweis ◽  
NA Yahya
Keyword(s):  
Aqueous Solutions ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Water Solution ◽  
Artificial Saliva ◽  
High Stress ◽  
Mechanical Analysis ◽  
Significance Level ◽  
Post Hoc ◽  
The Impact

SUMMARY This study compared the viscoelastic properties of restorative and flowable bulk-fill resin-based composites (RBCs) with their conventional counterparts and evaluated the impact of aqueous solutions on viscoelastic properties. The materials examined included three conventional RBCs (Filtek Z350, Tetric N Ceram, and Beautifil II), three restorative bulk-fill RBCs (Filtek Bulk-Fill Restorative, Tetric N Ceram Bulk-Fill, and Beautifil Bulk-Fill Restorative) in addition to three flowable bulk-fill RBCs (Filtek Bulk-Fill Flowable, Tetric N Flow Bulk-Fill, and Beautifil Bulk-Fill Flowable). Beam-shaped specimens (12×2×2 mm) were fabricated using customized stainless-steel molds, finished, and measured. The specimens were randomly divided into four groups and conditioned in air (control), artificial saliva, 0.02 N citric acid, and 50% ethanol-water solution for seven days at 37°C. They were then subjected to dynamic mechanical analysis (n = 10) in flexure mode at 37°C with a frequency of 0.1 to 10 Hz. Storage modulus, loss modulus, and loss tangent data were subjected to statistical analysis using one-way analysis of variance/Tukey post hoc test at a significance level of α = 0.05. Viscoelastic properties of the RBCs were found to be product and conditioning medium dependent. For most RBCs, exposure to aqueous solutions, particularly an ethanol-water solution, degraded viscoelastic properties. With the exception of Filtek Bulk-Fill Restorative, bulk-fill restorative and flowable RBCs generally had significantly lower storage and loss modulus than their conventional counterparts regardless of conditioning medium. Conventional RBCs are thus favored over their bulk-fill counterparts, particularly for high-stress-bearing areas.

Relationships Between the Friction and Viscoelastic Properties of Rubber

2000 ◽  
Vol 28 (3) ◽  
pp. 178-195 ◽  
Author(s):  
N. Amino ◽  
Y. Uchiyama
Keyword(s):  
Viscoelastic Properties ◽  
Skid Resistance ◽  
Grain Sizes ◽  
Abrasive Grain ◽  
The Coefficient Of Friction ◽  
Tan Δ ◽  
Silicone Carbide ◽  
And Storage ◽  
Wet Skid Resistance ◽  
Frequency Curves

Abstract In this study, the relationships between friction and viscoelastic properties such as loss tangent tan δ and storage modulusE′ were examined. Wet skid resistance was measured using the British Pendulum Tester. The rubber specimens were rubbed againstfive silicone carbide cloths of differing abrasive grain sizes. The viscoelastic properties of the rubber specimens were measured with a viscoelasticspectrometer. From the data on wet skid resistance and viscoelastic properties, it is found that the coefficient of friction μ varies as follows:           μ = a + b · tan δ/E′ where a and b are constants. Tan δ/E′ was related to the hysteresis term of friction, and the μ-frequency curves were compared with the tan δ/E′ –frequency curves.

Effect of a-Week Summer Camp on the Hopelessness and Self-Esteem of the University Students Attending Sport Sciences Faculty

2018 ◽  
Vol 7 (4) ◽  
pp. 42-49 ◽  
Author(s):  
Korkmaz YİĞİTER ◽  
Hakan TOSUN
Keyword(s):  
University Students ◽  
Summer Camp ◽  
Pearson Correlation ◽  
Self Esteem ◽  
Female Students ◽  
T Test ◽  
Significance Level ◽  
Significant Difference ◽  
Post Test ◽  
The University

The aim of this study is to investigate the effects of participation in a 1-week summer camp on thehopelessness and self-esteem of the university students attending Sport Sciences Faculty. Participants were 36university students assigned to experiment group using a random procedure. Coopersmith Self-esteem and Beck Hopelessness Scales were completed at the beginning and end of the summer camp by designed the university. The obtained data were analysed in the SPSS 18.0 program and the significance level was taken as 0.05. The descriptive statistics, independent simple t test, paired simple t test and Pearson correlation were used for analyse the data in the study. According to the results of the research, no significant difference was observed in the comparison of the hopelessness and self-esteem levels between pre and post-test. In addition, there was a significant difference in the hopelessness level of male and female students but any significant difference was not observed in terms of self-esteem. There was a significant relationship between hopelessness and self-esteem pre and post-test. These result shows that a 1-week summer camp cannot change the hopelessness or self-esteem level. However, as the self-esteem rises, the rate of despair decreases whereas as the despair rises, the selfesteem decreases.

scholarly journals Effect of Nanofiller Content on Dynamic Mechanical and Thermal Properties of Multi-Walled Carbon Nanotube and Montmorillonite Nanoclay Filler Hybrid Shape Memory Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 700
Author(s):  
Muhamad Hasfanizam Mat Yazik ◽  
Mohamed Thariq Hameed Sultan ◽  
Mohammad Jawaid ◽  
Abd Rahim Abu Talib ◽  
Norkhairunnisa Mazlan ◽  
...  
Keyword(s):  
Shape Memory ◽  
High Performance ◽  
Loss Modulus ◽  
Decomposition Temperature ◽  
Hybrid Nanocomposites ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Hybrid Filler ◽  
Dynamic Mechanical ◽  
Tan Δ

The aim of the present study has been to evaluate the effect of hybridization of montmorillonite (MMT) and multi-walled carbon nanotubes (MWCNT) on the thermal and viscoelastic properties of shape memory epoxy polymer (SMEP) nanocomposites. In this study, ultra-sonication was utilized to disperse 1%, 3%, and 5% MMT in combination with 0.5%, 1%, and 1.5% MWCNT into the epoxy system. The fabricated SMEP hybrid nanocomposites were characterized via differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The storage modulus (E’), loss modulus (E”), tan δ, decomposition temperature, and decomposition rate, varied upon the addition of the fillers. Tan δ indicated a reduction of glass transition temperature (Tg) for all the hybrid SMEP nanocomposites. 3% MMT/1% MWCNT displayed best overall performance compared to other hybrid filler concentrations and indicated a better mechanical property compared to neat SMEP. These findings open a way to develop novel high-performance composites for various potential applications, such as morphing structures and actuators, as well as biomedical devices.

scholarly journals The Influence of the Addition of Nuts on the Thermal and Rheological Properties of Wheat Flour

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3969
Author(s):  
Karolina Pycia ◽  
Lesław Juszczak
Keyword(s):  
Rheological Properties ◽  
Wheat Flour ◽  
Viscoelastic Properties ◽  
Control Sample ◽  
Scanning Calorimetry ◽  
Creep And Recovery ◽  
Research Material ◽  
Pasting Characteristics ◽  
Tan Δ ◽  
Weak Gels

The aim of the study was to assess the influence of replacing wheat flour with hazelnuts or walnuts, in various amounts, on the thermal and rheological properties of the obtained systems. The research material were systems in which wheat flour was replaced with ground hazelnuts (H) or walnuts (W) in the amount of 5%, 10%, and 15%. The parameters of the thermodynamic gelatinization characteristics were determined by the differential scanning calorimetry method. In addition, the pasting characteristics were determined with the use of a viscosity analyzer and the viscoelastic properties were assessed. Sweep frequency and creep and recovery tests were used to assess the viscoelastic properties of the tested gels. It was found that replacing wheat flour with nuts increased the values of gelatinization temperature, gelatinization, and retrogradation enthalpy, and the degree of retrogradation. The highest viscosity was characteristic of the control sample (2039 mPa·s), and the lowest for the paste with 15% addition of walnuts (1120 mPa·s). Replacing the flour with nuts resulted in a very visible reduction in the viscosity of such systems. In addition, gels based on the systems with the addition of H and W were weak gels (tan δ = G″/G′ > 0.1), and the values of G′ and G″ parameters decreased with the increased share of nuts in the systems. Creep and recovery analysis indicated that the systems in which wheat flour was replaced with hazelnuts were less susceptible to deformation compared to the systems with the addition of W.

scholarly journals Soft Jumping Robot Using Soft Morphing and the Yield Point of Magnetic Force

2021 ◽  
Vol 11 (13) ◽  
pp. 5891
Author(s):  
Gang-Hyun Jeon ◽  
Yong-Jai Park
Keyword(s):  
Residual Stress ◽  
Polymer Materials ◽  
Rigid Base ◽  
Release Mechanism ◽  
Transfer Energy ◽  
Deformation Control ◽  
Energy Retention ◽  
Base Jumping ◽  
Jumping Robot ◽  
Soft Polymer

In this paper, soft-morphing, deformation control by fabric structures and soft-jumping mechanisms using magnetic yield points are studied. The durability and adaptability of existing rigid-base jumping mechanisms are improved by a soft-morphing process that employs the residual stress of a polymer. Although rigid body-based jumping mechanisms are used, they are driven by multiple components and complex structures. Therefore, they have drawbacks in terms of shock durability and fatigue accumulation. To improve these problems, soft-jumping mechanisms are designed using soft polymer materials and soft-morphing techniques with excellent shock resistance and environmental adaptability. To this end, a soft jumping mechanism is designed to store energy using the air pressure inside the structure, and the thickness of the polymer layer is adjusted based on the method applied for controlling the polymer freedom and residual stress deformation. The soft jumping mechanism can transfer energy more efficiently and stably using an energy storage and release mechanism and the rounded ankle structure designed using soft morphing. Therefore, the soft morphing and mechanisms of energy retention and release were applied to fabricate a soft robot prototype that can move in the desired direction and jump; the performance experiment was carried out.

scholarly journals The Relationship between Foot Status and Motor Status in Preschool Children: A Simple, Comparative Observational Study

Healthcare ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 936
Author(s):  
Milan Kojić ◽  
Branka Protić Gava ◽  
Milan Bajin ◽  
Marko Vasiljević ◽  
Jasmina Bašić ◽  
...  
Keyword(s):  
Preschool Children ◽  
Observational Study ◽  
Total Sample ◽  
Nonparametric Tests ◽  
Significance Level ◽  
Flat Feet ◽  
Significant Difference ◽  
Left And Right ◽  
The Relationship

Background: The research objective of the study is to determine the differences in the manifestation of the motor status of normally fed preschool test subjects, classified into groups according to foot status. Methods: This is a simple, comparative observational study. Preschool children included in this study have been subjected to anthropometric measurements in order to determine BMI, tests for motor skills assessment (running at 20 m from a high start, standing broad jump, backwards polygon, rectangular seated forward bend, plate tapping, sit-ups for 60 s, and bent arm hang), and a determination of foot status. The total sample was comprised of 202 test subjects who attended a regular sports program, aged 3.9 to 6.5 years of decimal age (M = 141; Age = 5.3 ± 0.74; Height = 117.3 ± 7.1; Weight = 22 ± 3.7; F = 61; Age = 5.1 ± 0.73; Height = 114.9 ± 7.4; Weight = 21.2 ± 3.8), of which 153 (75.7%) were normally fed, 6 (3%) were undernourished, 30 were overweight (14.9%), and 13 were obese (6.4%). Results: In the total sample, 30 (14.9%) subjects had normal arch feet, 90 (44.6%) high arched feet, and 41 (20.3%) flat feet. We found 41 (20.3%) subjects who had different left and right foot statuses within this sample. The data were processed by means of nonparametric tests (the Kruskal–Wallis and Mann–Whitney U tests) at a significance level p ≤ 0.05. Conclusion: The results show that there is a statistically significant difference between groups of subjects with different foot statuses in the manifestation of motor status in most tests, with a significance level of p ≤ 0.01, and in tests of sit-ups for 60 s and the bent arm hang, there is a statistically significant difference, the level of which is p ≤ 0.05. It is only in the inclination test of rectangular seated forward bend that no statistically significant difference was displayed.

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