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15 pages, 6575 KiB

Open AccessArticle

Quasi-Static and Fatigue Properties of Thermoset Sandwiches with 3D Continuous Fibre Reinforced Polyurethane Foam Core

by Kay Schäfer, Daisy Nestler and Lothar Kroll

Materials 2022, 15(3), 764; https://doi.org/10.3390/ma15030764 - 20 Jan 2022

Cited by 2 | Viewed by 1871

Abstract

Innovative materials for substituting metals are required to reduce the mass of moving components. This decreases the CO₂ emissions of overall systems. A thermoset sandwich for high mechanical properties and thermal insulation is presented in this paper. It has an innovative 3D [...] Read more.

Innovative materials for substituting metals are required to reduce the mass of moving components. This decreases the CO₂ emissions of overall systems. A thermoset sandwich for high mechanical properties and thermal insulation is presented in this paper. It has an innovative 3D continuous reinforced core, which allows the optimisation of the substance exploitation by wide-ranging possibilities of fibre orientation. This was demonstrated with three sandwich variants. The reference had no core reinforcement and the other two were reinforced with different spacer fabrics. The process chain for the manufacturing consists of Structural Reaction Injection Moulding (SRIM) and Vacuum Assisted Resin Transfer Moulding (VARTM). Significant increases in absolute as well as specific characteristic values were demonstrated by the reinforcement in a compression and bending test. It was also shown that quasi-static characteristic values under fatigue loading are maintained to a greater extent with the core reinforcement. The sandwich material was applied as a floor assembly for a snow groomer. The design was tailor-made for the mechanical, thermal and acoustic requirements. This proved the transferability of the process chain for manufacturing samples to the production of large-volume components with complex geometry. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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19 pages, 10467 KiB

Open AccessEditor’s ChoiceArticle

Polyurethane Foams for Domestic Sewage Treatment

by Ewa Dacewicz and Joanna Grzybowska-Pietras

Materials 2021, 14(4), 933; https://doi.org/10.3390/ma14040933 - 16 Feb 2021

Cited by 21 | Viewed by 3880

Abstract

The aim of the study was to assess the possibility of using polyurethane foams (PUF) as a filling of a foam-sand filter to directly treat domestic sewage with increased content of ammonium nitrogen and low organic carbon to nitrogen ratio (C/N). The study [...] Read more.

The aim of the study was to assess the possibility of using polyurethane foams (PUF) as a filling of a foam-sand filter to directly treat domestic sewage with increased content of ammonium nitrogen and low organic carbon to nitrogen ratio (C/N). The study compared performance of two types of flexible foams: new, cylinder-shaped material (Novel Foams, NF) and waste, scrap foams (Waste Foams, WF). The foams serving as a filling of two segments of a foam-sand filter were assessed for their hydrophobic and physical properties and were tested for their cell structure, i.e., cell diameter, cell size distribution, porosity, and specific surface area. The study accounted also for selected application-related properties, such as hydrophobicity, water absorption, apparent density, dimensional stability, amount of adsorbed biomass, and the possibility of regeneration. Cell morphology was compared in reference foams, foams after 14 months of the filter operation, and regenerated foams. The experimental outcomes indicated WF as an innovative type of biomass carrier for treating domestic sewage with low C/N ratio. SEM images showed that immobilization of microorganisms in NF and WF matrices involved the formation of multi-cellular structures attached to the inner surface of the polyurethane and attachment of single bacterial cells to the foam surface. The amount of adsorbed biomass confirmed that the foam-sand filter made up of two upper layers of waste foams (with diameters and pore content of 0.50–1.53 mm and 53.0–63.5% respectively) provided highly favorable conditions for the development of active microorganisms. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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14 pages, 3813 KiB

Open AccessArticle

Microstructure–Property Relationship of Polyurethane Foams Modified with Baltic Sea Biomass: Microcomputed Tomography vs. Scanning Electron Microscopy

by Paulina Kosmela, Jan Suchorzewski, Krzysztof Formela, Paweł Kazimierski, Józef Tadeusz Haponiuk and Łukasz Piszczyk

Materials 2020, 13(24), 5734; https://doi.org/10.3390/ma13245734 - 16 Dec 2020

Cited by 6 | Viewed by 2327

Abstract

In this paper, novel rigid polyurethane foams modified with Baltic Sea biomass were compared with traditional petro-based polyurethane foam as reference sample. A special attention was focused on complex studies of microstructure, which was visualized and measured in 3D with high-resolution microcomputed tomography [...] Read more.

In this paper, novel rigid polyurethane foams modified with Baltic Sea biomass were compared with traditional petro-based polyurethane foam as reference sample. A special attention was focused on complex studies of microstructure, which was visualized and measured in 3D with high-resolution microcomputed tomography (microCT) and, as commonly applied for this purpose, scanning electron microscopy (SEM). The impact of pore volume, area, shape and orientation on appearance density and thermal insulation properties of polyurethane foams was determined. The results presented in the paper confirm that microcomputed tomography is a useful tool for relatively quick estimation of polyurethane foams’ microstructure, what is crucial especially in the case of thermal insulation materials. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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21 pages, 5796 KiB

Open AccessArticle

Research of Wood Waste as a Potential Filler for Loose-Fill Building Insulation: Appropriate Selection and Incorporation into Polyurethane Biocomposite Foams

by Nerijus Augaitis, Saulius Vaitkus, Sylwia Członka and Agnė Kairytė

Materials 2020, 13(23), 5336; https://doi.org/10.3390/ma13235336 - 25 Nov 2020

Cited by 20 | Viewed by 2142

Abstract

Currently, the recycling potential of wood waste (WW) is still limited, and in a resource efficiency approach, recycling WW in insulation materials, such as polyurethane (PUR), appears as an appropriate solution. It is known that the quality of WW is the main aspect [...] Read more.

Currently, the recycling potential of wood waste (WW) is still limited, and in a resource efficiency approach, recycling WW in insulation materials, such as polyurethane (PUR), appears as an appropriate solution. It is known that the quality of WW is the main aspect which influences the stability of the final products. Therefore, the current study analyses different WW-based fillers as possible modifiers for polyurethane biocomposite foams for the application as loose-fill materials in building envelopes. During the study of WW-based fillers, it was determined that the most promising filler is wood scobs (WS) with a thermal conductivity of 0.0496 W/m·K, short-term water absorption by partial immersion—12.5 kg/m², water vapour resistance—0.34 m²·h·Pa/mg and water vapour diffusion resistance factor—2.4. In order to evaluate the WS performance as a filler in PUR biocomposite foams, different ratios of PUR binder and WS filler (PURb/WS) were selected. It was found that a 0.40 PURb/WS ratio is insufficient for the appropriate wetting of WS filler while a 0.70 PURb/WS ratio produced PUR biocomposite foams with the most suitable performance: thermal conductivity reduced from 0.0523 to 0.0476 W/m·K, water absorption—from 5.6 to 1.3 kg/m², while the compressive strength increased from 142 to 272 kPa and the tensile strength increased from 44 to 272 kPa. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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13 pages, 7727 KiB

Open AccessArticle

Is Fracture Toughness of PUR Foams a Material Property? A Statistical Approach

by Adrian Pugna, Romeo Negrea, Emanoil Linul and Liviu Marsavina

Materials 2020, 13(21), 4868; https://doi.org/10.3390/ma13214868 - 30 Oct 2020

Cited by 9 | Viewed by 2513

Abstract

The published data on the experimentally determined fracture toughness of foams are based on a small number of specimens, having a lack of statistical consistency. The paper proposes a statistical approach on the fracture toughness results of rigid polyurethane (PUR) foams of three [...] Read more.

The published data on the experimentally determined fracture toughness of foams are based on a small number of specimens, having a lack of statistical consistency. The paper proposes a statistical approach on the fracture toughness results of rigid polyurethane (PUR) foams of three different densities. Five types of fracture tests were considered. The results were statistically analyzed using six types of regressions and a meta-analysis to identify the factors influencing the fracture toughness. The statistical analysis indicates that the fracture toughness represents a material property because does not depend on the specimen type. The density plays a major role in the fracture toughness of PUR foams. The irregular shape of the cells induced small anisotropy for low-density foams (100 kg/m³ and 145 kg/m³). This effect could not be observed for the foam with 300 kg/m³ density, for which the cells have a more regular spherical shape. The statistical analysis indicates that the influence of the loading speed is very weak. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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18 pages, 5225 KiB

Open AccessArticle

Upgrading Sustainable Polyurethane Foam Based on Greener Polyols: Succinic-Based Polyol and Mannich-Based Polyol

by Ferdinando de Luca Bossa, Letizia Verdolotti, Vincenzo Russo, Pietro Campaner, Andrea Minigher, Giuseppe Cesare Lama, Laura Boggioni, Riccardo Tesser and Marino Lavorgna

Materials 2020, 13(14), 3170; https://doi.org/10.3390/ma13143170 - 16 Jul 2020

Cited by 19 | Viewed by 4574

Abstract

It is well known that the traditional synthetic polymers, such as Polyurethane foams, require raw materials that are not fully sustainable and are based on oil-feedstocks. For this reason, renewable resources such as biomass, polysaccharides and proteins are still recognized as one of [...] Read more.

It is well known that the traditional synthetic polymers, such as Polyurethane foams, require raw materials that are not fully sustainable and are based on oil-feedstocks. For this reason, renewable resources such as biomass, polysaccharides and proteins are still recognized as one of the most promising approaches for substituting oil-based raw materials (mainly polyols). However, polyurethanes from renewable sources exhibit poor physical and functional performances. For this reason, the best technological solution is the production of polyurethane materials obtained through a partial replacement of the oil-based polyurethane precursors. This approach enables a good balance between the need to improve the sustainability of the polymer and the need to achieve suitable performances, to fulfill the technological requirements for specific applications. In this paper, a succinic-based polyol sample (obtained from biomass source) was synthesized, characterized and blended with cardanol-based polyol (Mannich-based polyol) to produce sustainable rigid polyurethane foams in which the oil-based polyol is totally replaced. A suitable amount of catalysts and surfactant, water as blowing reagent and poly-methylene diphenyl di-isocyanate as isocyanate source were used for the polyurethane synthesis. The resulting foams were characterized by means of infrared spectroscopy (FTIR) to control the cross-linking reactions, scanning electron microscopy (SEM) to evaluate the morphological structure and thermal gravimetric analysis (TGA) and thermal conductivity to evaluate thermal degradation behavior and thermal insulation properties. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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16 pages, 5873 KiB

Open AccessArticle

The Synergistic Effect of Ionic Liquid-Modified Expandable Graphite and Intumescent Flame-Retardant on Flame-Retardant Rigid Polyurethane Foams

by Yongjun Chen, Yuanfang Luo, Xiaohui Guo, Lijuan Chen and Demin Jia

Materials 2020, 13(14), 3095; https://doi.org/10.3390/ma13143095 - 10 Jul 2020

Cited by 26 | Viewed by 3022

Abstract

In this study, a nitrogen–phosphorus intumescent flame-retardant 3-(N-diphenyl phosphate) amino propyl triethoxy silane (DPES), the ionic liquid (IL) of 1-butyl-3-methyl-imidazole phosphate, and a phosphorous-containing ionic liquid-modified expandable graphite (IL-EG), were synthesized, and their molecular structures were characterized. The flame-retardant rigid polyurethane foams (RPUFs) [...] Read more.

In this study, a nitrogen–phosphorus intumescent flame-retardant 3-(N-diphenyl phosphate) amino propyl triethoxy silane (DPES), the ionic liquid (IL) of 1-butyl-3-methyl-imidazole phosphate, and a phosphorous-containing ionic liquid-modified expandable graphite (IL-EG), were synthesized, and their molecular structures were characterized. The flame-retardant rigid polyurethane foams (RPUFs) were compounded with synergistic flame-retardant IL-EG/DPES to study the effects of the combination IL-EG and DPES on the pore structure, mechanical properties, thermal decomposition behavior and thermal decomposition mechanism of RPUF. The results showed that IL-EG/DPES had good thermal stability, and an excellent expansibility and char yield. The flame-retardant RPUF, modified with IL-EG and DPES at the ratio of 1:1, had a relatively uniform pore size, the highest compressive strength, and an excellent flame-retardant performance due to the form interwoven hydrogen bonds between IL-EG and DPES, as well as the new synergistic flame-retardant coating on the RPUF surface to restrict the transfer of gas or heat into the PU matrix. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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21 pages, 3996 KiB

Open AccessArticle

Application of Walnut Shells-Derived Biopolyol in the Synthesis of Rigid Polyurethane Foams

by Sylwia Członka, Anna Strąkowska and Agnė Kairytė

Materials 2020, 13(12), 2687; https://doi.org/10.3390/ma13122687 - 12 Jun 2020

Cited by 26 | Viewed by 2875

Abstract

This study aimed to examine rigid polyurethane (PUR) foam properties that were synthesized from walnut shells (WS)-based polyol. The Fourier Transform Infrared Spectroscopy (FTIR) results revealed that the liquefaction of walnut shells was successfully performed. The three types of polyurethane (PUR) foams were [...] Read more.

This study aimed to examine rigid polyurethane (PUR) foam properties that were synthesized from walnut shells (WS)-based polyol. The Fourier Transform Infrared Spectroscopy (FTIR) results revealed that the liquefaction of walnut shells was successfully performed. The three types of polyurethane (PUR) foams were synthesized by replacement of 10, 20, and 30 wt% of a petrochemical polyol with WS-based polyol. The impact of WS-based polyol on the cellular morphology, mechanical, thermal, and insulating characteristics of PUR foams was examined. The produced PUR foams had apparent densities from 37 to 39 kg m⁻³, depending on the weight ratio of WS-based polyol. PUR foams that were obtained from WS-based polyol exhibited improved mechanical characteristics when compared with PUR foams that were derived from the petrochemical polyol. PUR foams produced from WS-based polyol showed compressive strength from 255 to 310 kPa, flexural strength from 420 to 458 kPa, and impact strength from 340 to 368 kPa. The foams that were produced from WS-based polyol exhibited less uniform cell structure than foams derived from the petrochemical polyol. The thermal conductivity of the PUR foams ranged between 0.026 and 0.032 W m⁻¹K⁻¹, depending on the concentration of WS-based polyol. The addition of WS-based polyol had no significant influence on the thermal degradation characteristics of PUR foams. The maximum temperature of thermal decomposition was observed for PUR foams with the highest loading of WS-based polyol. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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21 pages, 3730 KiB

Open AccessArticle

High Functionality Bio-Polyols from Tall Oil and Rigid Polyurethane Foams Formulated Solely Using Bio-Polyols

by Mikelis Kirpluks, Edgars Vanags, Arnis Abolins, Slawomir Michalowski, Anda Fridrihsone and Ugis Cabulis

Materials 2020, 13(8), 1985; https://doi.org/10.3390/ma13081985 - 24 Apr 2020

Cited by 39 | Viewed by 5158

Abstract

High-quality rigid polyurethane (PU) foam thermal insulation material has been developed solely using bio-polyols synthesized from second-generation bio-based feedstock. High functionality bio-polyols were synthesized from cellulose production side stream—tall oil fatty acids by oxirane ring-opening as well as esterification reactions with different polyfunctional [...] Read more.

High-quality rigid polyurethane (PU) foam thermal insulation material has been developed solely using bio-polyols synthesized from second-generation bio-based feedstock. High functionality bio-polyols were synthesized from cellulose production side stream—tall oil fatty acids by oxirane ring-opening as well as esterification reactions with different polyfunctional alcohols, such as diethylene glycol, trimethylolpropane, triethanolamine, and diethanolamine. Four different high functionality bio-polyols were combined with bio-polyol obtained from tall oil esterification with triethanolamine to develop rigid PU foam formulations applicable as thermal insulation material. The developed formulations were optimized using response surface modeling to find optimal bio-polyol and physical blowing agent: c-pentane content. The optimized bio-based rigid PU foam formulations delivered comparable thermal insulation properties to the petro-chemical alternative. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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17 pages, 2590 KiB

Open AccessArticle

Closed Cell Rigid Polyurethane Foams Based on Low Functionality Polyols: Research of Dimensional Stability and Standardised Performance Properties

by Agnė Kairytė, Arūnas Kremensas, Giedrius Balčiūnas, Sylwia Członka and Anna Strąkowska

Materials 2020, 13(6), 1438; https://doi.org/10.3390/ma13061438 - 21 Mar 2020

Cited by 21 | Viewed by 4748

Abstract

Currently, polyurethane foam producers come across the several problems when petroleum-based polyols are replaced with low functionality biomass, or waste-based, polyols. In addition, the dilemma is intensified with regulations that require full or partial replacement of blowing agents that can cause high ozone [...] Read more.

Currently, polyurethane foam producers come across the several problems when petroleum-based polyols are replaced with low functionality biomass, or waste-based, polyols. In addition, the dilemma is intensified with regulations that require full or partial replacement of blowing agents that can cause high ozone depletion with alternatives like water, which causes the formation of CO₂. Therefore, these gases diffuse out of the foam so quickly that the polymeric cell walls cannot withstand the pressure, consequently causing huge dimensional changes at ambient temperature and humidity. Even though the theoretical stoichiometric balance is correct, the reality shows that it is not enough. Therefore, polyethylene terephthalate waste-based polyol was chosen as a low functionality polyol which was modified with high functionality sucrose-based polyol in order to obtain dimensionally stable polyurethane foams in the density range of 30–40 kg/m³. These more stable foams are characterized by linear changes no higher than 0.5%, short-term water absorption by partial immersion no higher than 0.35 kg/m², and water vapor resistance factors up to 50. In order to obtain thermally efficient polyurethane foams, conventional blowing agents and water systems were implemented, thus, assuring thermal conductivity values in the range of 0.0198–0.0204 W/(m·K) and obtaining products which conform to all the requirements for performance of sprayed and factory-made polyurethane foam standards EN 14315-1 and EN 13165. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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20 pages, 2652 KiB

Open AccessArticle

Bio-Based Polyurethane Composite Foams with Improved Mechanical, Thermal, and Antibacterial Properties

by Sylwia Członka, Anna Strąkowska, Krzysztof Strzelec, Agnė Kairytė and Arūnas Kremensas

Materials 2020, 13(5), 1108; https://doi.org/10.3390/ma13051108 - 02 Mar 2020

Cited by 55 | Viewed by 7415

Abstract

Among different organic fillers, the chemical composition of Syzygium aromaticum, commonly known as cloves, has great potential as a sustainable reinforcement for polymeric materials. In the study, grounded cloves were used as cellulosic filler for a novel polyurethane (PU) composite foams. Soybean [...] Read more.

Among different organic fillers, the chemical composition of Syzygium aromaticum, commonly known as cloves, has great potential as a sustainable reinforcement for polymeric materials. In the study, grounded cloves were used as cellulosic filler for a novel polyurethane (PU) composite foams. Soybean oil-based PU composite foams were successfully reinforced with different concentrations (1, 2, and 5 wt%) of clove filler. PU foams were examined by rheological behavior, processing parameters, cellular structure (scanning electron microscopy analysis), mechanical properties (compression test, impact test, three-point bending test), thermal properties (thermogravimetric analysis), viscoelastic behavior (dynamic mechanical analysis) as well as selected application properties (apparent density, dimensional stability, surface hydrophobicity, water absorption, color characteristic). In order to undertake the disc diffusion method, all PU composites were tested against selected bacteria (Escherichia coli and Staphylococcus aureus). Based on the results, it can be concluded that the addition of 1 and 2 wt% of clove filler leads to PU composite foams with improved compression strength (improvement by ≈18% for sample PU-1), greater flexural strength (increase of ≈11%), and improved impact strength (increase of ≈8%). Moreover, it has been proved that clove filler may be used as a natural anti-aging compound for polymeric materials. Based on the antibacterial results, it has been shown that the addition of clove filler significantly improved the antibacterial properties of PU foams and is suitable for the manufacturing of antimicrobial PU composite foams. Due to these positive and beneficial effects, it can be stated that the use of cloves as a natural filler in PU composite foams can promote a new application path in converting agricultural waste into useful resources for creating a new class of green materials. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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Review

Jump to: Research

38 pages, 3892 KiB

Open AccessReview

Clays as Inhibitors of Polyurethane Foams’ Flammability

by Aleksander Hejna

Materials 2021, 14(17), 4826; https://doi.org/10.3390/ma14174826 - 25 Aug 2021

Cited by 15 | Viewed by 3649

Abstract

Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications [...] Read more.

Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a “labyrinth effect” inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams’ flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams’ flammability, either by their incorporation as a nanofiller or by preparation of coatings. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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