Viscoelastic Polyurethane Foams for Use as Auxiliary Materials in Orthopedics

One of the essential factors in prostheses is their fitting. To assemble a prosthesis with the residual limb, so-called liners are used. Liners used currently are criticized by users for their lack of comfort, causing excessive sweating and skin irritation. The objective of the work was to develop viscoelastic polyurethane foams for use in limb prostheses. As part of the work, foams were produced with different isocyanate indexes (0.6–0.9) and water content (1, 2 and 3 php). The produced foams were characterized by scanning electron microscopy, computer microtomography, infrared spectroscopy, thermogravimetry and differential scanning calorimetry. Measurements also included apparent density, recovery time, rebound elasticity, permanent deformation, compressive stress value and sweat absorption. The results were discussed in the context of modifying the foam recipe. The performance properties of the foams, such as recovery time, hardness, resilience and sweat absorption, indicate that foams that will be suitable for prosthetic applications are foams with a water content of 2 php produced with an isocyanate index of 0.8 and 0.9.

Download Full-text

Physical Properties of Soy-Phosphate Polyol-Based Rigid Polyurethane Foams

International Journal of Polymer Science ◽

10.1155/2012/907049 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Hongyu Fan ◽

Ali Tekeei ◽

Galen J. Suppes ◽

Fu-Hung Hsieh

Keyword(s):

Thermal Conductivity ◽

Compressive Strength ◽

Thermal Properties ◽

Water Content ◽

Polyurethane Foams ◽

Solid Polymer ◽

Mechanical And Thermal Properties ◽

Blowing Agent ◽

Isocyanate Index ◽

Pu Foams

Water-blown rigid polyurethane (PU) foams were made from 0–50% soy-phosphate polyol (SPP) and 2–4% water as the blowing agent. The mechanical and thermal properties of these SPP-based PU foams (SPP PU foams) were investigated. SPP PU foams with higher water content had greater volume, lower density, and compressive strength. SPP PU foams with 3% water content and 20% SPP had the lowest thermal conductivity. The thermal conductivity of SPP PU foams decreased and then increased with increasing SPP percentage, resulting from the combined effects of thermal properties of the gas and solid polymer phases. Higher isocyanate density led to higher compressive strength. At the same isocyanate index, the compressive strength of some 20% SPP foams was close or similar to the control foams made from VORANOL 490.

Download Full-text

Acoustic damping flexible polyurethane foams: Effect of isocyanate index and water content on the soundproofing

Journal of Applied Polymer Science ◽

10.1002/app.47363 ◽

2018 ◽

Vol 136 (15) ◽

pp. 47363 ◽

Cited By ~ 4

Author(s):

Sahar Abdollahi Baghban ◽

Manouchehr Khorasani ◽

Gity Mir Mohamad Sadeghi

Keyword(s):

Water Content ◽

Polyurethane Foams ◽

Acoustic Damping ◽

Isocyanate Index ◽

Flexible Polyurethane

Download Full-text

Viscoelastic Polyurethane Foams for Use in Seals of Respiratory Protective Devices

Materials ◽

10.3390/ma14071600 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1600

Author(s):

Małgorzata Okrasa ◽

Milena Leszczyńska ◽

Kamila Sałasińska ◽

Leonard Szczepkowski ◽

Paweł Kozikowski ◽

...

Keyword(s):

Water Content ◽

Apparent Density ◽

Recovery Time ◽

Elastic Recovery ◽

Air Permeability ◽

Polyurethane Foams ◽

Time Compression ◽

Protective Devices ◽

Compression Set ◽

Respiratory Protective Devices

A key factor in effective protection against airborne hazards, i.e., biological and nonbiological aerosols, vapors, and gases, is a good face fit of respiratory protective devices (RPDs). Equally important is the comfort of use, which may encourage or discourage users from donning RPDs. The objective of the work was to develop viscoelastic polyurethane foams for use in RPD seals. The obtained foams were characterized using scanning electron microscopy, infrared spectroscopy, thermogravimetry, and differential scanning calorimetry. Measurements also involved gel fraction, apparent density, air permeability, elastic recovery time, compression set, rebound resilience, and sweat uptake. The results were discussed in the context of modifications to the foam formulation: the isocyanate index (INCO) in the range of 0.6–0.9 and the blowing agent content in the range of 1.2–3.0 php. FTIR analysis revealed a higher level of urea groups with increasing water content in the formulation. Higher INCO and water content levels also led to lower onset temperatures of thermal degradation and higher glass-transition temperatures of the soft phase. A decrease in apparent density and an increase in mean pore sizes of the foams with increasing INCO and water content levels was observed. Functional parameters (air permeability, elastic recovery time, compression set, rebound resilience, and sweat uptake) were also found to be satisfactory at lower INCO and water content levels.

Download Full-text

Effects of Various Types of Expandable Graphite and Blackcurrant Pomace on the Properties of Viscoelastic Polyurethane Foams

Materials ◽

10.3390/ma14071801 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1801

Author(s):

Rafał Oliwa ◽

Joanna Ryszkowska ◽

Mariusz Oleksy ◽

Monika Auguścik-Królikowska ◽

Małgorzata Gzik ◽

...

Keyword(s):

Mechanical Properties ◽

Chemical Structure ◽

Oxygen Index ◽

Polyurethane Foams ◽

Expandable Graphite ◽

Ftir Analysis ◽

Limiting Oxygen Index ◽

Peak Heat Release Rate ◽

Physical And Chemical ◽

Scanning Electron

We investigated the effect of the type and amount of expandable graphite (EG) and blackcurrant pomace (BCP) on the flammability, thermal stability, mechanical properties, physical, and chemical structure of viscoelastic polyurethane foams (VEF). For this purpose, the polyurethane foams containing EG, BCP, and EG with BCP were obtained. The content of EG varied in the range of 3–15 per hundred polyols (php), while the BCP content was 30 php. Based on the obtained results, it was found that the additional introduction of BCPs into EG-containing composites allows for an additive effect in improving the functional properties of viscoelastic polyurethane foams. As a result, the composite containing 30 php of BCP and 15 php of EG with the largest particle size and expanded volume shows the largest change in the studied parameters (hardness (H) = 2.65 kPa (+16.2%), limiting oxygen index (LOI) = 26% (+44.4%), and peak heat release rate (pHRR) = 15.5 kW/m2 (−87.4%)). In addition, this composite was characterized by the highest char yield (m600 = 17.9% (+44.1%)). In turn, the change in mechanical properties is related to a change in the physical and chemical structure of the foams as indicated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis.

Download Full-text

Application of the Calorimetric Methods to the Characteristics of Seeds from Olives

Proceedings ◽

10.3390/foods_2020-07665 ◽

2020 ◽

Vol 70 (1) ◽

pp. 90

Author(s):

Andrzej Bryś ◽

Joanna Bryś ◽

Marko Obranović ◽

Dubravka Škevin ◽

Szymon Głowacki ◽

...

Keyword(s):

Olive Oil ◽

Water Content ◽

Cooling System ◽

Waste Product ◽

Normal Pressure ◽

Ash Content ◽

Initial Water Content ◽

Scanning Calorimetry ◽

Initial Water

The olive oil industry represents an important productive sector in the Mediterranean basin countries. Olive stone is an essential by-product generated in the olive oil extraction industries and it represents roughly 10% by weight of the olive fruit. The seeds of pickled olives are also a significant waste product. In the present study, we have investigated the possibility of the use of differential scanning calorimetry for the thermal characterization of seeds from green and black pickled olives from Croatia. The differential scanning calorimeter (DSC) with a normal pressure cell equipped with a cooling system was used to determine the thermal properties of seeds from olives. The following analyses were also performed: the determination of calorific values in a pressure bomb calorimeter, the determination of initial water content, the determination of changes of water content during drying at the temperatures of 30 °C, 50 °C and 80 °C, the determination of a percentage content of seeds mass to the mass of the whole olives, and the determination of ash content. Seeds from olives are characterized by very good parameters as a biomass. The analyzed olive seeds were characterized by low water content, low ash content, and a relatively high caloric value.

Download Full-text

Characteristics of Reconstituted Collagen Fibers from Chicken Keel Cartilage Depends on Salt Type for Removal of Proteoglycans

Molecules ◽

10.3390/molecules26123538 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3538

Author(s):

Anna Pudło ◽

Szymon Juchniewicz ◽

Wiesław Kopeć

Keyword(s):

Electron Microscopy ◽

Rheological Properties ◽

Thermal Denaturation ◽

Surface Structures ◽

Scanning Calorimetry ◽

Cartilage Extracellular Matrix ◽

Oscillatory Rheometry ◽

Freeze Dried ◽

Basic Features ◽

Scanning Electron

The aim of the presented research was to obtain reconstituted atelocollagen fibers after extraction from poultry cartilage using the pepsin-acidic method in order to remove telopeptides from the tropocollagen. Firstly, we examined the extraction of collagen from the cartilage extracellular matrix (ECM) after proteoglycans (PG) had been removed by the action of salts, i.e., NaCl or chaotropic MgCl2. Additionally, the effects of the salt type used for PG and hyaluronic acid removal on the properties of self-assembled fibers in solutions at pH 7.4 and freeze-dried matrices were investigated. The basic features of the obtained fibers were characterized, including thermal properties using scanning calorimetry, rheological properties using dynamic oscillatory rheometry, and the structure by scanning electron microscopy. The fibers obtained after PG removal with both analyzed types of salts had similar thermal denaturation characteristics. However, the fibers after PG removal with NaCl, in contrast to those obtained after MgCl2 treatment, showed different rheological properties during gelatinization and smaller diameter size. Moreover, the degree of fibrillogenesis of collagens after NaCl treatment was complete compared to that with MgCl2, which was only partial (70%). The structures of fibers after lyophilization were fundamentally different. The matrices obtained after NaCl pretreatment form regular scaffolds in contrast to the thin, surface structures of the cartilage matrix after proteoglycans removal using MgCl2.

Download Full-text

Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part I: Membrane Synthesis and Characterization

Nanomaterials ◽

10.3390/nano11030607 ◽

2021 ◽

Vol 11 (3) ◽

pp. 607

Author(s):

Carolina Hermida-Merino ◽

Fernando Pardo ◽

Gabriel Zarca ◽

João M. M. Araújo ◽

Ane Urtiaga ◽

...

Keyword(s):

Polymer Membranes ◽

Small Addition ◽

Polymeric Membranes ◽

Synthesis And Characterization ◽

Complete Disappearance ◽

Optical Profilometry ◽

Scanning Calorimetry ◽

Exfoliated Graphene ◽

The Stability ◽

Scanning Electron

In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was determined by thermogravimetric analysis (TGA). The morphology of membranes was characterized using scanning electron microscope (SEM) and interferometric optical profilometry (WLOP). SEM results evidence that upon the small addition of xGnP into the IL-dominated environment, the interaction between IL and xGnP facilitates the migration of xGnP to the surface, while suppressing the interaction between IL and Pebax®1657. Fourier transform infrared spectroscopy (FTIR) was also used to determine the polymer–IoNF interactions and the distribution of the IL in the polymer matrix. Finally, the thermodynamic properties and phase transitions (polymer–IoNF) of these functionalized membranes were studied using differential scanning calorimetry (DSC). This analysis showed a gradual decrease in the melting point of the polyamide (PA6) blocks with a decrease in the corresponding melting enthalpy and a complete disappearance of the crystallinity of the polyether (PEO) phase with increasing IL content. This evidences the high compatibility and good mixing of the polymer and the IoNF.

Download Full-text

Thermal properties of polybenzoxazine exhibiting improved toughness: Blending with cyclodextrin and its derivatives

High Performance Polymers ◽

10.1177/09540083211013091 ◽

2021 ◽

pp. 095400832110130

Author(s):

Hailong Li ◽

Sipei Zhao ◽

Li Pei ◽

Zihe Qiao ◽

Ding Han ◽

...

Keyword(s):

Thermal Properties ◽

Hydrogen Bonds ◽

High Performance ◽

Practical Application ◽

Scanning Calorimetry ◽

Thermoset Resins ◽

Chemical Structures ◽

Microscopy Techniques ◽

Fractured Surface ◽

Scanning Electron

Polybenzoxazines are emerging as a class of high-performance thermoset polymers that can find their applications in various fields. However, its practical application is limited by its low toughness. The cyclic β-cyclodextrin and a newly synthesized derivative (β-cyclodextrin-MAH) were separately blended with benzoxazine to improve the toughness of polybenzoxazine. The results revealed that the maximum impact strength of the blend was 12.24 kJ·m−2 and 14.29 kJ·m−2 when 1 wt.% of β-Cyclodextrin and β-Cyclodextrin-MAH, respectively, were used. The strengths were 53% and 86% higher than that of pure polybenzoxazine. The curing reaction, possible chemical structures, and fractured surface were examined using differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques to understand the mechanism of generation of toughness. The results revealed that the sea-island structure and the presence of hydrogen bonds between polybenzoxazine and β-cyclodextrin and β-cyclodextrin-MAH resulted in the generation of toughness. Furthermore, the curves generated during thermogravimetric analysis did not significantly change, revealing the good thermal properties of the system. The phase-separated structure and the hydrogen bonds present in the system can be exploited to prepare synergistically tough polybenzoxazine exhibiting excellent thermal properties. This can be a potential way of modifying the thermoset resins.

Download Full-text

Extraction of Boron from Ludwigite Ore: Mechanism of Soda-Ash Roasting of Lizardite and Szaibelyite

Minerals ◽

10.3390/min9090533 ◽

2019 ◽

Vol 9 (9) ◽

pp. 533 ◽

Cited By ~ 4

Author(s):

Xin Zhang ◽

Guanghui Li ◽

Jinxiang You ◽

Jian Wang ◽

Jun Luo ◽

...

Keyword(s):

Sodium Carbonate ◽

Energy Dispersive Spectrometer ◽

Low Grade ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Selective Activation ◽

X Ray ◽

Shed Light ◽

Soda Ash ◽

Scanning Electron

Ludwigite ore is a typical low-grade boron ore accounting for 58.5% boron resource of China, which is mainly composed of magnetite, lizardite and szaibelyite. During soda-ash roasting of ludwigite ore, the presence of lizardite hinders the selective activation of boron. In this work, lizardite and szaibelyite were prepared and their soda-ash roasting behaviors were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) analyses, in order to shed light on the soda-ash activation of boron within ludwigite ore. Thermodynamics of Na2CO3-MgSiO3-Mg2SiO4-Mg2B2O5 via FactSage show that the formation of Na2MgSiO4 was preferential for the reaction between Na2CO3 and MgSiO3/Mg2SiO4. While, regarding the reaction between Na2CO3 and Mg2B2O5, the formation of NaBO2 was foremost. Raising temperature was beneficial for the soda-ash roasting of lizardite and szaibelyite. At a temperature lower than the melting of sodium carbonate (851 °C), the soda-ash roasting of szaibelyite was faster than that of lizardite. Moreover, the melting of sodium carbonate accelerated the reaction between lizardite with sodium carbonate.

Download Full-text

INFLUENCE OF La2O3 ADDITIONS ON CHEMICAL DURABILITY AND DIELECTRIC PROPERTIES OF BOROALUMINOSILICATE GLASSES

Surface Review and Letters ◽

10.1142/s0218625x1250062x ◽

2012 ◽

Vol 19 (06) ◽

pp. 1250062 ◽

Cited By ~ 3

Author(s):

X. H. ZHANG ◽

Y. L. YUE ◽

H. T. WU

Keyword(s):

Dielectric Properties ◽

Chemical Durability ◽

Tangent Loss ◽

Frequency Range ◽

Scanning Calorimetry ◽

Glass Transition Temperatures ◽

Weight Losses ◽

Quenching Method ◽

Scanning Electron

Boroaluminosilicate glasses containing La2O3 were prepared by the normal quenching method. The glass transition temperatures (Tg) were measured by differential scanning calorimetry (DSC). The structural role of RO was investigated by nuclear magnetic resonance (NMR). Chemical durability was evaluated by weight losses of glass samples after immersion in HC1 solution. High resolution scanning electron microscopy (HR-SEM) was used to examine the surface micrographs of corroded glass samples. The dielectric constant and tangent loss were measured in the frequency range 10–106 Hz. The results revealed that chemical durability and dielectric properties increased with increasing La2O3 content.

Download Full-text