Research

17 pages, 3038 KiB

Open AccessArticle

Polyurethane Adhesives with Chemically Debondable Properties via Diels–Alder Bonds

by María Pilar Carbonell-Blasco, María Alejandra Moyano, Carlota Hernández-Fernández, Francisco J. Sierra-Molero, Isidro M. Pastor, Diego A. Alonso, Francisca Arán-Aís and Elena Orgilés-Calpena

Polymers 2024, 16(1), 21; https://doi.org/10.3390/polym16010021 - 20 Dec 2023

Cited by 1 | Viewed by 1519

Abstract

Covalent adaptable networks (CANs) represent a pioneering advance in polymer science, offering unprecedented versatility in materials design. Unlike conventional adhesives with irreversible bonds, CAN-based polyurethane adhesives have the unique ability to undergo chemical restructuring through reversible bonds. One of the strategies for incorporating [...] Read more.

Covalent adaptable networks (CANs) represent a pioneering advance in polymer science, offering unprecedented versatility in materials design. Unlike conventional adhesives with irreversible bonds, CAN-based polyurethane adhesives have the unique ability to undergo chemical restructuring through reversible bonds. One of the strategies for incorporating these types of reactions in polyurethanes is by functionalisation with Diels–Alder (DA) adducts. By taking advantage of the reversible nature of the DA chemistry, the adhesive undergoes controlled crosslinking and decrosslinking processes, allowing for precise modulation of bond strength. This adaptability is critical in applications requiring reworkability or recyclability, as it allows for easy disassembly and reassembly of bonded components without compromising the integrity of the material. This study focuses on the sustainable synthesis and characterisation of a solvent-based polyurethane adhesive, obtained by functionalising a polyurethane prepolymer with DA diene and dienophiles. The characterisation of the adhesives was carried out using different experimental techniques: nuclear magnetic resonance spectroscopy (NMR), Brookfield viscosity, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and T-peel strength testing of leather/adhesive/rubber joints to determine the adhesive properties, both before and after the application of external stimuli. The conversion of both the DA and retro-Diels–Alder (r-DA) reactions was confirmed by ¹H-NMR. The adhesive properties were not altered by the functionalisation of the adhesive prepolymer, showing similar thermal resistance and good rheological and adhesive properties, even exceeding the most demanding technical requirements for upper-to-sole joints in footwear. After the application of an external thermal stimuli, the bonded materials separated without difficulty and without damage, thus facilitating their separation, recovery and recycling. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Figure 1

19 pages, 38750 KiB

Open AccessArticle

Enhancing Strength and Sustainability: Evaluating Glass and Basalt Fiber-Reinforced Biopolyamide as Alternatives for Petroleum-Based Polyamide Composite

by Dariusz Bednarowski, Patrycja Bazan and Stanisław Kuciel

Polymers 2023, 15(16), 3400; https://doi.org/10.3390/polym15163400 - 14 Aug 2023

Viewed by 864

Abstract

This study aims to analyze strength properties and low-cycle dynamic tests of composite materials modified with glass and basalt fibers. Biopolyamide 4.10 was used as the matrix, and the fiber contents were 15, 30, and 50% by weight. Static tensile tests, impact tests, [...] Read more.

This study aims to analyze strength properties and low-cycle dynamic tests of composite materials modified with glass and basalt fibers. Biopolyamide 4.10 was used as the matrix, and the fiber contents were 15, 30, and 50% by weight. Static tensile tests, impact tests, and determination of mechanical hysteresis loops were carried out as strength tests. The length of the fibers in the produced composites and their processing properties were determined. The composite materials were compared with commercially available glass fiber-reinforced composites with 30 and 50% fiber contents. The results showed that such composites can successfully replace composite materials based on petroleum-based polymeric materials, providing high strength properties and reducing the negative environmental impact by using renewable sources. Composites with 30% basalt fiber composition were characterized by higher tensile strength by about 60% compared to commercially available composites with 30% glass fiber composition and an almost doubly increased Young’s modulus. Increasing the content of basalt fibers to 50% results in a further increase in strength properties. Despite the lower tensile strength compared to polyamide 6 with 50% glass fiber content, basalt fibers provided an approximately 10% higher modulus of elasticity. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Figure 1

19 pages, 12060 KiB

Open AccessArticle

Characteristics of 3D Printed Biopolymers for Applications in High-Voltage Electrical Insulation

by Robert Sekula, Kirsi Immonen, Sini Metsä-Kortelainen, Maciej Kuniewski, Paweł Zydroń and Tomi Kalpio

Polymers 2023, 15(11), 2518; https://doi.org/10.3390/polym15112518 - 30 May 2023

Cited by 3 | Viewed by 1387

Abstract

Three-dimensional printing technology is constantly developing and has a wide range of applications; one application is electrical insulation, where the standard technology uses polymer-based filaments. Thermosetting materials (epoxy resins, liquid silicone rubbers) are broadly used as electrical insulation in high-voltage products. In power [...] Read more.

Three-dimensional printing technology is constantly developing and has a wide range of applications; one application is electrical insulation, where the standard technology uses polymer-based filaments. Thermosetting materials (epoxy resins, liquid silicone rubbers) are broadly used as electrical insulation in high-voltage products. In power transformers, however, the main solid insulation is based on cellulosic materials (pressboard, crepe paper, wood laminates). There are a vast variety of transformer insulation components that are produced using the wet pulp molding process. This is a labor-intensive, multi-stage process that requires long drying times. In this paper, a new material, microcellulose-doped polymer, and manufacturing concept for transformer insulation components are described. Our research focuses on bio-based polymeric materials with 3D printability functionalities. A number of material formulations were tested and benchmark products were printed. Extensive electrical measurements were performed to compare transformer components manufactured using the traditional process and 3D printed samples. The results are promising but indicate that further research is still required to improve printing quality. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Figure 1

30 pages, 7242 KiB

Open AccessArticle

Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler—Part II: Mechanical, Thermal and Ageing (Chemical) Properties

by Jelena Lubura, Olga Kočková, Beata Strachota, Oskar Bera, Ewa Pavlova, Jelena Pavličević, Bojana Ikonić, Predrag Kojić and Adam Strachota

Polymers 2023, 15(10), 2397; https://doi.org/10.3390/polym15102397 - 21 May 2023

Cited by 1 | Viewed by 1399

Abstract

Natural rubber composites were reinforced by the co-fillers ‘hydrochar’ (HC), obtained by hydrothermal carbonization of hardwood sawdust and commercial carbon black (CB). The content of the combined fillers was kept constant while their ratio was varied. The aim was to test the suitability [...] Read more.

Natural rubber composites were reinforced by the co-fillers ‘hydrochar’ (HC), obtained by hydrothermal carbonization of hardwood sawdust and commercial carbon black (CB). The content of the combined fillers was kept constant while their ratio was varied. The aim was to test the suitability of HC as a partial filler in natural rubber. Due to its larger particle size and hence smaller specific surface area, large amounts of HC reduced the crosslinking density in the composites. On the other hand, due to its unsaturated organic character, HC was found to display interesting chemical effects: if it was used as the exclusive filler component, it displayed a very strong anti-oxidizing effect, which greatly stabilized the rubber composite against oxidative crosslinking (and hence embrittlement). HC also affected the vulcanization kinetics in different ways, depending on the HC/CB ratio. Composites with HC/CB ratios 20/30 and 10/40 displayed interesting chemical stabilization in combination with fairly good mechanical properties. The performed analyses included vulcanization kinetics, tensile properties, determination of density of permanent and reversible crosslinking in dry and swollen states, chemical stability tests including TGA, thermo-oxidative aging tests in air at 180 °C, simulated weathering in real use conditions (‘Florida test’), and thermo-mechanical analyses of degraded samples. Generally, the results indicate that HC could be a promising filler material due to its specific reactivity. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Graphical abstract

14 pages, 3699 KiB

Open AccessArticle

Pyroresistive Properties of Composites Based on HDPE and Carbon Fillers

by Yevgen Mamunya, Oleksii Maruzhenko, Roman Kolisnyk, Maksym Iurzhenko, Andrii Pylypenko, Olha Masiuchok, Marcin Godzierz, Igor Krivtsun, Barbara Trzebicka and Sébastien Pruvost

Polymers 2023, 15(9), 2105; https://doi.org/10.3390/polym15092105 - 28 Apr 2023

Cited by 3 | Viewed by 1448

Abstract

Electrothermal processes were studied in pyroresistive composites based on high-density polyethylene (HDPE) containing 8 vol.% carbon black (CB), 8 vol.% carbon fibers (CF), and their mixture 4 vol.% CB + 4 vol.% CF. It is shown that the kinetic heating curves of composites [...] Read more.

Electrothermal processes were studied in pyroresistive composites based on high-density polyethylene (HDPE) containing 8 vol.% carbon black (CB), 8 vol.% carbon fibers (CF), and their mixture 4 vol.% CB + 4 vol.% CF. It is shown that the kinetic heating curves of composites are well described by an exponential dependence with a certain heating rate constant k for each type of composite. After a short heating time, the equilibrium temperature T_e is reached in the sample. When the applied voltage exceeds a certain value, the T_e value decreases due to the presence of the positive temperature coefficient of resistance (PTC) effect. Due to the PTC effect, the composites exhibit a self-regulating effect relative to the T_e. Relations between the applied voltage, electric power, and equilibrium temperature are found, the T_e value depends on the applied voltage according to the quadratic law whereas there is a linear relationship between the T_e and electric power. A possible application of such pyroresistive composites is resistance welding of plastics using a heating element (HE) made of a pyroresistive material. The use of HDPE-CB composite to create HE for resistance welding is demonstrated and the welded joint of HDPE parts obtained using HE is shown. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Graphical abstract

12 pages, 3300 KiB

Open AccessArticle

Multiple Responsive Hydrogel Films Based on Dynamic Phenylboronate Bond Linkages with Simple but Practical Linear Response Mode and Excellent Glucose/Fructose Response Speed

by Rong Xu, Jiafeng Tian, Yusheng Song, Shihui Dong and Yongjun Zhang

Polymers 2023, 15(9), 1998; https://doi.org/10.3390/polym15091998 - 23 Apr 2023

Viewed by 1301

Abstract

Multiple responsive hydrogels are usually constructed by the addition of many different functional groups. Generally, these groups have different responsive behaviors which lead to interleaved and complex modes of the multi-response system. It is difficult to get a practical application. In this study, [...] Read more.

Multiple responsive hydrogels are usually constructed by the addition of many different functional groups. Generally, these groups have different responsive behaviors which lead to interleaved and complex modes of the multi-response system. It is difficult to get a practical application. In this study, we show that multi-response hydrogels can also be constructed using dynamic bonds as crosslinks. The multiple responsive hydrogel films with thicknesses on the sub-micrometer or micrometer scale can be fabricated from P(DMAA-3-AAPBA), a copolymer of N,N-dimethylacrylamide, 3-(acrylamido)phenylboronic acid, and poly(vinylalcohol) (PVA) though a simple layer-by-layer (LbL) technique. The driving force for the film build up is the in situ-formed phenylboronate ester bonds between the two polymers. The films exhibit Fabry–Perot fringes on their reflection spectra which can be used to calculate the equilibrium swelling degree (SD_e) of the film so as to characterize its responsive behaviors. The results show that the films are responsive to temperature, glucose, and fructose with simple and practical linear response modes. More importantly, the speed of which the films respond to glucose or fructose is quite fast, with characteristic response times of 45 s and 7 s, respectively. These quick response films may have potential for real-time, continuous glucose or fructose monitoring. With the ability to bind with these biologically important molecules, one can expect that hydrogels may find more applications in biomedical areas in the future. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Figure 1

12 pages, 2439 KiB

Open AccessArticle

Examination of Low-Cyclic Fatigue Tests and Poisson’s Ratio Depending on the Different Infill Density of Polylactide (PLA) Produced by the Fused Deposition Modeling Method

by Anna Gaweł, Stanisław Kuciel, Aneta Liber-Kneć and Dariusz Mierzwiński

Polymers 2023, 15(7), 1651; https://doi.org/10.3390/polym15071651 - 26 Mar 2023

Cited by 3 | Viewed by 3792

Abstract

This article examines the impact of fatigue cycles on polylactide samples produced by 3D printing using the FDM method. Samples were printed in three infill degree variants: 50%, 75% and 100%. To compere the influence of infill degree on PLA properties, several tests, [...] Read more.

This article examines the impact of fatigue cycles on polylactide samples produced by 3D printing using the FDM method. Samples were printed in three infill degree variants: 50%, 75% and 100%. To compere the influence of infill degree on PLA properties, several tests, including the uniaxial tensile test, the low-cycle fatigue test, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), were conducted. Poisson’s ratio has also been studied. Single hysteresis loops were summed to obtain the entire low-fatigue cycle. The infill of density influenced all compared mechanical parameters. The decrease in infill degree caused the reduction of Young’s modulus and shear modulus. For a 100% degree of sample infill, a higher number of transferred load cycles were observed compared to PLA with 75% and 50% of infill. Additionally, the value of the transferred cyclic load before fatigue failure and the dissipation of mechanical energy was the highest for 100% of infill. It is also worth noting that fatigue tests can positively affect the appearance of the PLA structure. Obviously, it depends on the number of load cycles and the infill density. It causes that if the goal is to transfer as much load as possible over a long period of time, the maximum filling of the printed element should be used. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Figure 1

18 pages, 4497 KiB

Open AccessArticle

Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler- Part I: Structure, Morphology, and Rheological Effects during Vulcanization

by Jelena Lubura, Libor Kobera, Sabina Abbrent, Ewa Pavlova, Beata Strachota, Oskar Bera, Jelena Pavličević, Bojana Ikonić, Predrag Kojić and Adam Strachota

Polymers 2023, 15(5), 1176; https://doi.org/10.3390/polym15051176 - 26 Feb 2023

Cited by 5 | Viewed by 1934

Abstract

A new generation biomass-based filler for natural rubber, ‘hydrochar’ (HC), was obtained by hydrothermal carbonization of hardwood waste (sawdust). It was intended as a potential partial replacement for the traditional carbon black (CB) filler. The HC particles were found (TEM) to be much [...] Read more.

A new generation biomass-based filler for natural rubber, ‘hydrochar’ (HC), was obtained by hydrothermal carbonization of hardwood waste (sawdust). It was intended as a potential partial replacement for the traditional carbon black (CB) filler. The HC particles were found (TEM) to be much larger (and less regular) than CB: 0.5–3 µm vs. 30–60 nm, but the specific surface areas were relatively close to each other (HC: 21.4 m²/g vs. CB: 77.8 m²/g), indicating a considerable porosity of HC. The carbon content of HC was 71%, up from 46% in sawdust feed. FTIR and ¹³C-NMR analyses indicated that HC preserved its organic character, but it strongly differs from both lignin and cellulose. Experimental rubber nanocomposites were prepared, in which the content of the combined fillers was set at 50 phr (31 wt.%), while the HC/CB ratios were varied between 40/10 and 0/50. Morphology investigations proved a fairly even distribution of HC and CB, as well as the disappearance of bubbles after vulcanization. Vulcanization rheology tests demonstrated that the HC filler does not hinder the process, but it significantly influences vulcanization chemistry, canceling scorch time on one hand and slowing down the reaction on the other. Generally, the results suggest that rubber composites in which 10–20 phr of CB are replaced by HC might be promising materials. The use of HC in the rubber industry would represent a high-tonnage application for hardwood waste. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Application of Functional Polymer Materials for Advanced Technologies

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI