Polymers

Research

15 pages, 2933 KiB

Open AccessArticle

Self-Healing and Reprocessable Oleic Acid-Based Elastomer with Dynamic S-S Bonds as Solvent-Free Reusable Adhesive on Copper Surface

by Luca Pettazzoni, Francesca Leonelli, Andrea Giacomo Marrani, Luisa Maria Migneco, Fabrizio Vetica, Lorenzo Celio, Valerio Napoleone, Sara Alfano, Andrea Colecchia, Francesco Amato, Valerio Di Lisio and Andrea Martinelli

Polymers 2022, 14(22), 4919; https://doi.org/10.3390/polym14224919 - 14 Nov 2022

Cited by 2 | Viewed by 2670

Abstract

In the last decade, the application of dynamic covalent chemistry in the field of polymeric materials has become the subject of an increasing number of studies, gaining applicative relevance. This is due to the fact that polymers containing dynamic functions possess a structure [...] Read more.

In the last decade, the application of dynamic covalent chemistry in the field of polymeric materials has become the subject of an increasing number of studies, gaining applicative relevance. This is due to the fact that polymers containing dynamic functions possess a structure that affords reprocessability, recyclability and peculiar self-healing properties inconceivable for “classic” polymer networks. Consequently, the synthesis of a dynamic covalent chemistry-based polymer and its chemical, thermal, and mechanical characterizations are reported in the present research. In particular, oleic acid has been used as starting material to follow the founding principles of the circular economy system and, thanks to the aromatic disulfide component, which is the foundation of the material dynamic characteristics, the obtained polymer resulted as being reprocessable and self-healable. Moreover, the polymer can strongly interact with copper surfaces through the formation of stable Cu-S bonds. Then, the application of the polymer as a solvent-free reusable adhesive for copper was investigated by lap joint shear tests and comparisons with the properties of an analogous material, devoid of the disulfide bonds, were conducted. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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19 pages, 5795 KiB

Open AccessArticle

Comparative Mechanical Study of Pressure Sensitive Adhesives over Aluminium Substrates for Industrial Applications

by Marta Ortega-Iguña, Mariane Chludzinski and José María Sánchez-Amaya

Polymers 2022, 14(21), 4783; https://doi.org/10.3390/polym14214783 - 7 Nov 2022

Cited by 7 | Viewed by 2735

Abstract

The use of adhesives for fixing low-weight elements is showing increasing interest in the industry, as it would reduce the weight of the assembly, costs, and production time. Specifically, the application of pressure-sensitive adhesives (PSAs) to join non-structural naval components to aluminium substrates [...] Read more.

The use of adhesives for fixing low-weight elements is showing increasing interest in the industry, as it would reduce the weight of the assembly, costs, and production time. Specifically, the application of pressure-sensitive adhesives (PSAs) to join non-structural naval components to aluminium substrates has not yet been reported. In the present work, a study of the mechanical behaviour of different double-sided PSAs applied on bare aluminium alloy substrates is performed. The influence of surface roughness, surface chemical treatments, and the matrix of the adhesives is studied through different mechanical tests, such as shear, T-peel, and creep. The application of an adhesion promoter improved the mechanical behaviour. Low roughness substrates provided better performance than ground samples. Acrylic foam adhesives were subjected to creep tests, whose results were fitted to a simple mathematical model, predicting the fracture time as a function of the applied load. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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13 pages, 3945 KiB

Open AccessArticle

Effect of Epoxy Structure on Properties of Waterborne Coatings and Electrical Steel Laminates

by Cornelia Marchfelder, Robert Pugstaller, Gernot M. Wallner, Oliver Brüggemann and Maëlenn Aufray

Polymers 2022, 14(8), 1556; https://doi.org/10.3390/polym14081556 - 11 Apr 2022

Cited by 6 | Viewed by 2922

Abstract

Epoxy varnishes are of high relevance to advanced steel laminates for the transformation of electric energy. Structure–property correlations of epoxy varnishes, coil coatings and electrical steel laminates are poorly described. Hence, the main objective of this paper was to develop, implement and evaluate [...] Read more.

Epoxy varnishes are of high relevance to advanced steel laminates for the transformation of electric energy. Structure–property correlations of epoxy varnishes, coil coatings and electrical steel laminates are poorly described. Hence, the main objective of this paper was to develop, implement and evaluate well-defined waterborne model epoxy varnishes for electrical steel laminates, and to elucidate structure–property correlations. Adhesives with systematically varied equivalent epoxy weight (EEW) based on bisphenol-A-diglycidyl ether (DGEBA) were investigated and used to formulate waterborne varnishes. Crosslinking agent dicyandiamide (DICY) was added in an over-stoichiometric ratio. The waterborne model varnishes were prepared by shear emulsification at elevated temperatures. The model varnishes in the A-stage were applied to electrical steel using a doctoral blade. At a peak metal temperature of 210 °C, the coatings were cured to the partly crosslinked B-stage. Coated steel sheets were stacked, laminated and fully cured to C-stage at 180 °C for 2 h. For laminates with an epoxy adhesive layer in the C-stage, glass transition temperatures (T_G) in the range of 81 to 102 °C were obtained by dynamic mechanical analysis in torsional mode. Within the investigated EEW range, a negative linear correlation of EEW and T_G was ascertained. Presumably, higher EEW of the varnish is associated with a less densely crosslinked network in the fully cured state. Roll peel testing of laminates at ambient and elevated temperatures up to 140 °C confirmed the effect of EEW. However, no clear correlation of roll peel strength and glass transition temperature was discernible. In contrast, fatigue fracture mechanics investigations revealed that hydroxyl functionality and crosslinking density were affecting the crack growth resistance of laminates in a contrary manner. The energy-based fracture mechanics approach was much more sensitive than monotonic peel testing. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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16 pages, 7791 KiB

Open AccessArticle

Structural Integrity of the Aircraft Interior Spare Parts Produced by Additive Manufacturing

by Stepans Kobenko, Didzis Dejus, Jānis Jātnieks, Dāvis Pazars and Tatjana Glaskova-Kuzmina

Polymers 2022, 14(8), 1538; https://doi.org/10.3390/polym14081538 - 11 Apr 2022

Cited by 10 | Viewed by 2997

Abstract

In this paper, the results obtained for the structural integrity of two real-life aircraft interior parts produced by using Ultem 9085 and the fused deposition modeling (FDM) are presented. Numerical simulation was used to perform static mechanical analysis of the class divider subjected [...] Read more.

In this paper, the results obtained for the structural integrity of two real-life aircraft interior parts produced by using Ultem 9085 and the fused deposition modeling (FDM) are presented. Numerical simulation was used to perform static mechanical analysis of the class divider subjected to the case of the most critical load. By using a simple beam model, it was identified that the most efficient way of increasing the bending stiffness (required to pass the most crucial load case test) would be to increase the part’s width of the class divider. Mechanical testing of the parts was performed in vertical and horizontal load directions to supplement the numerical results. For the class divider, it was testified that the 3D-printed part would not fail under the most critical load case. For the folding table printed as a honeycomb structure, when loaded at the tip, the critical load of 900 N was acceptable, and as it was shown, there was significant potential for further optimization of the structure to either increase the maximum load or reduce the weight for any given load. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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16 pages, 6162 KiB

Open AccessArticle

Effect of Marble Dust on the Mechanical, Morphological, and Wear Performance of Basalt Fibre-Reinforced Epoxy Composites for Structural Applications

by Abhinay Singh Rajawat, Sanjeev Singh, Brijesh Gangil, Lalit Ranakoti, Shubham Sharma, Muhammad Rizal Muhammad Asyraf and Muhammad Rizal Razman

Polymers 2022, 14(7), 1325; https://doi.org/10.3390/polym14071325 - 24 Mar 2022

Cited by 47 | Viewed by 3781

Abstract

The reinforcement of natural fibre and fillers in polymer resin is the latest trend followed by research groups and industries for the development of sustainable composites. Basalt fibre and waste marble powder are naturally occurring substances used to enhanced polymer properties. The present [...] Read more.

The reinforcement of natural fibre and fillers in polymer resin is the latest trend followed by research groups and industries for the development of sustainable composites. Basalt fibre and waste marble powder are naturally occurring substances used to enhanced polymer properties. The present research examined the effect of both basalt fibre and waste marble powder in epoxy resin. The hand lay-up method was employed to fabricate the composite and test for mechanical and wear behaviour. The tensile, flexural, and impact energy were enhanced up to 7.5 wt. % of WMP, and the Vickers hardness of epoxy enhanced every state of reinforcement of WMP. The specific wear rate was observed to be increased with the addition of WMP until 7.5 wt. %. Scanning electron microscopy was performed to examine the nature of fractured surface wear phenomena. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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13 pages, 3634 KiB

Open AccessArticle

Influence of Acrylonitrile Content on the Adhesive Properties of Water-Based Acrylic Pressure-Sensitive Adhesives

by Irene Márquez, Núria Paredes, Felipe Alarcia and José Ignacio Velasco

Polymers 2022, 14(5), 909; https://doi.org/10.3390/polym14050909 - 24 Feb 2022

Cited by 4 | Viewed by 3354

Abstract

A series of pressure-sensitive adhesives (PSA) were prepared by emulsion polymerization in order to obtain a PSA that meet with the current label market requirements. For it, the effect of the incorporation of acrylonitrile (ACN) as hard monomer was investigated in a n [...] Read more.

A series of pressure-sensitive adhesives (PSA) were prepared by emulsion polymerization in order to obtain a PSA that meet with the current label market requirements. For it, the effect of the incorporation of acrylonitrile (ACN) as hard monomer was investigated in a n-butyl acrylate (n-BA) and acrylic acid (AA) system. Great differences were found in the adhesive performance according to the ACN weight ratio. Its increased resulted in a considerable rise in the average sol molecular weight and in the glass transition temperature. This was reflected in a decrease of adhesion forces (peel resistance and tack) and an increase of the cohesion forces (shear resistance). Moreover, the incorporation of the minimum amount of ACN studied showed a great change in the elastic modulus determined by dynamic shear resistance with respect to the based formulation that did not contain ACN. Finally, the ice bucket test was carried out to check the adhesive performance in cold and wet environments. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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15 pages, 2152 KiB

Open AccessArticle

Role of Macrodiols in the Synthesis and Thermo-Mechanical Behavior of Anti-Tack Water Borne Polyurethane Dispersions

by Nadia Akram, Muhammad Saeed and Muhammad Usman

Polymers 2022, 14(3), 572; https://doi.org/10.3390/polym14030572 - 31 Jan 2022

Cited by 5 | Viewed by 2822

Abstract

The texture and molecular weight of polymer drastically affect the adhesion or tack strength. Waterborne polyurethane dispersions (WBPU) have been prepared using two different macrodiols of hydroxyl terminated polybutadiene (HTPB; Mn = 2912 g/mol⁻¹) and four compositions of Polypropylene glycol (PPG [...] Read more.

The texture and molecular weight of polymer drastically affect the adhesion or tack strength. Waterborne polyurethane dispersions (WBPU) have been prepared using two different macrodiols of hydroxyl terminated polybutadiene (HTPB; Mn = 2912 g/mol⁻¹) and four compositions of Polypropylene glycol (PPG Mn = 425, 1000, 2000, 2700 g/mol⁻¹). The contents of the macrodiols have been varied using HTPB as 5, 10 and 15 mol%. The prepolymer of HTPB and Poly propylene glycol (PPG) have been developed using 4,4-Methylene bis(cyclohexyl isocyanate) (H₁₂MDI) which is extended using 1, 4 butanediol (BD) followed by the dispersion of polymers in deionized water. Fourier Transform Infra-red spectroscopy (FTIR) is used to confirm the desired PU linkage. The probe tack graphs for tack analysis have not shown any plateau indicating absence of fibrillation. Two different values of glass transition temperature (Tg) have been observed for each dispersion using Differential Scanning Calorimetry(DSC). Storage modulus (E′) up to 3.97 MPa and (tanδ/E′) from 0.01–0.30 MPa⁻¹ has been observed via Dynamic Mechanical Analysis (DMA). Introducing the HTPB has resulted in a decrease in the values of (tanδ/E′). No adhesion favorable parameters have been retrieved, indicating the molar variation a key factor in the development of anti-tack dispersions. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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13 pages, 20484 KiB

Open AccessArticle

Experimental Research on Polymer-Based Coaxial Sealing Systems of Hydraulic Cylinders for Small Displacement Velocities

by Tudor Deaconescu and Andrea Deaconescu

Polymers 2022, 14(2), 290; https://doi.org/10.3390/polym14020290 - 11 Jan 2022

Cited by 3 | Viewed by 2353

Abstract

Reducing friction in the coaxial sealing systems of hydraulic cylinders is one of the solutions for increasing the energy efficiency of industrial actuations. This is a requirement, particularly in the case of small velocities that carry the risk of eigen-vibrations and/or stick-slip. The [...] Read more.

Reducing friction in the coaxial sealing systems of hydraulic cylinders is one of the solutions for increasing the energy efficiency of industrial actuations. This is a requirement, particularly in the case of small velocities that carry the risk of eigen-vibrations and/or stick-slip. The authors discuss the experimental research conducted on three coaxial sealing systems made from thermoplastic polymer and polyurethane type materials. The paper presents the equipment and method used for the experimental determination of static and kinematic friction coefficients and discusses the subsequent results obtained to test different working parameters. The experimentally determined friction coefficients yielded a range of materials recommended for coaxial seals such as to minimize the occurrence of jerky operation. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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14 pages, 5849 KiB

Open AccessArticle

Understanding the Role of Carbon Fiber Skeletons in Silicone Rubber-Based Ablative Composites

by Yuan Ji, Shida Han, Zhiheng Chen, Hong Wu, Shaoyun Guo, Ning Yan, Hongyan Li and Tao Luan

Polymers 2022, 14(2), 268; https://doi.org/10.3390/polym14020268 - 10 Jan 2022

Cited by 12 | Viewed by 2734

Abstract

At present, silicone rubber-based ablative composites are usually enhanced by carbon fibers (CFs) to protect the case of solid rocket motors (SRMs). However, the effect of the CFs’ length on the microstructure and ablation properties of the silicone rubber-based ablative composites has been [...] Read more.

At present, silicone rubber-based ablative composites are usually enhanced by carbon fibers (CFs) to protect the case of solid rocket motors (SRMs). However, the effect of the CFs’ length on the microstructure and ablation properties of the silicone rubber-based ablative composites has been ignored. In this work, different lengths of CFs were introduced into silicone rubber-based ablative composites to explore the effect of fiber length, and ceramic layers of various morphologies were constructed after ablation. It was found that a complete and continuous skeleton in ceramic layers was formed by CFs over 3 mm in length. In addition, the oxyacetylene ablation results showed that the linear ablation rate declined from 0.233 to 0.089 mm/s, and the maximum back-face temperature decreased from 117.7 to 107.9 °C as the length of the CFs increased from 0.5 to 3 mm. This can be attributed to the fact that successive skeletons concatenated and consolidated the ceramic fillers as well as residues to form an integrated, robust, and dense ceramic layer. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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18 pages, 2112 KiB

Open AccessArticle

Effect of Low Molecular Weight Oxidized Materials and Nitrogen Groups on Adhesive Joints of Polypropylene Treated by a Cold Atmospheric Plasma Jet

by Kateřina Polášková, Miloš Klíma, Zdeňka Jeníková, Lucie Blahová and Lenka Zajíčková

Polymers 2021, 13(24), 4396; https://doi.org/10.3390/polym13244396 - 15 Dec 2021

Cited by 16 | Viewed by 3466

Abstract

Polypropylene is a typical representative of synthetic polymers that, for many applications including adhesive joints, requires an increase in wettability and chemical surface reactivity. Plasma processing offers efficient methods for such surface modifications. A particular disadvantage of the plasma jets can be the [...] Read more.

Polypropylene is a typical representative of synthetic polymers that, for many applications including adhesive joints, requires an increase in wettability and chemical surface reactivity. Plasma processing offers efficient methods for such surface modifications. A particular disadvantage of the plasma jets can be the small plasma area. Here, we present a cold atmospheric plasma radio-frequency slit jet developed with a width of 150 mm applied to polypropylene plasma treatment in Ar, Ar/O

_{2}

and Ar/N

_{2}

We identified two main parameters influencing the tensile strength of adhesive joints mediated by epoxy adhesive DP 190, nitrogen content, and the amount of low molecular weight oxidized materials (LMWOMs). Nitrogen functional groups promoted adhesion between epoxy adhesive DP 190 and the PP by taking part in the curing process. LMWOMs formed a weak boundary layer, inhibiting adhesion by inducing a cohesive failure of the joint. A trade off between these two parameters determined the optimized conditions at which the strength of the adhesive joint increased 4.5 times. Higher adhesion strength was previously observed when using a translational plasma gliding arc plasma jet with higher plasma gas temperatures, resulting in better cross linking of polymer chains caused by local PP melting. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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18 pages, 45550 KiB

Open AccessArticle

The Effect of Disinfectants Absorption and Medical Decontamination on the Mechanical Performance of 3D-Printed ABS Parts

by Diana Popescu, Florin Baciu, Catalin Gheorghe Amza, Cosmin Mihai Cotrut and Rodica Marinescu

Polymers 2021, 13(23), 4249; https://doi.org/10.3390/polym13234249 - 3 Dec 2021

Cited by 9 | Viewed by 2742

Abstract

Producing parts by 3D printing based on the material extrusion process determines the formation of air gaps within layers even at full infill density, while external pores can appear between adjacent layers making prints permeable. For the 3D-printed medical devices, this open porosity [...] Read more.

Producing parts by 3D printing based on the material extrusion process determines the formation of air gaps within layers even at full infill density, while external pores can appear between adjacent layers making prints permeable. For the 3D-printed medical devices, this open porosity leads to the infiltration of disinfectant solutions and body fluids, which might pose safety issues. In this context, this research purpose is threefold. It investigates which 3D printing parameter settings are able to block or reduce permeation, and it experimentally analyzes if the disinfectants and the medical decontamination procedure degrade the mechanical properties of 3D-printed parts. Then, it studies acetone surface treatment as a solution to avoid disinfectants infiltration. The absorption tests results indicate the necessity of applying post-processing operations for the reusable 3D-printed medical devices as no manufacturing settings can ensure enough protection against fluid intake. However, some parameter settings were proven to enhance the sealing, in this sense the layer thickness being the most important factor. The experimental outcomes also show a decrease in the mechanical performance of 3D-printed ABS (acrylonitrile butadiene styrene) instruments treated by acetone cold vapors and then medical decontaminated (disinfected, cleaned, and sterilized by hydrogen peroxide gas plasma sterilization) in comparison to the control prints. These results should be acknowledged when designing and 3D printing medical instruments. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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10 pages, 4163 KiB

Open AccessArticle

Characteristic Tearing Energy and Fatigue Crack Propagation of Filled Natural Rubber

by Jigang Rong, Jun Yang, Youjian Huang, Wenbo Luo and Xiaoling Hu

Polymers 2021, 13(22), 3891; https://doi.org/10.3390/polym13223891 - 10 Nov 2021

Cited by 8 | Viewed by 2709

Abstract

Below the incipient characteristic tearing energy (T₀), cracks will not grow in rubber under fatigue loading. Hence, determination of the characteristic tearing energy T₀ is very important in the rubber industry. A rubber cutting experiment was conducted to determine [...] Read more.

Below the incipient characteristic tearing energy (T₀), cracks will not grow in rubber under fatigue loading. Hence, determination of the characteristic tearing energy T₀ is very important in the rubber industry. A rubber cutting experiment was conducted to determine the T₀, using the cutting method proposed originally by Lake and Yeoh. Then, a fatigue crack propagation experiment on a edge-notched pure shear specimen under variable amplitude loading was studied. A method to obtain the crack propagation rate da/dN from the relationship of the crack propagation length (Δa) with the number of cycles (N) is proposed. Finally, the T₀ obtained from the cutting method is compared with the value decided by the fatigue crack propagation experiment. The values of T₀ obtained from the two different methods are a little different. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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12 pages, 58419 KiB

Open AccessArticle

Surface Treatment of Composites with Bismaleimide Resin-Based Wet Peel Ply for Enhanced Adhesive Bonding Performance

by Hongfeng Li, Liwei Zhao, Yingjie Qiao, Xuefeng Bai, Dezhi Wang, Chunyan Qu, Changwei Liu and Yongqiang Wang

Polymers 2021, 13(20), 3488; https://doi.org/10.3390/polym13203488 - 11 Oct 2021

Cited by 11 | Viewed by 2475

Abstract

Surface treatment is typically required to improve the bonding performance of carbon-fiber-reinforced composites. Herein, a wet peel ply was prepared using bismaleimide (BMI) resins as a matrix resin. The temperature–heating rate extrapolation method and rheological method were employed to study the reaction characteristics [...] Read more.

Surface treatment is typically required to improve the bonding performance of carbon-fiber-reinforced composites. Herein, a wet peel ply was prepared using bismaleimide (BMI) resins as a matrix resin. The temperature–heating rate extrapolation method and rheological method were employed to study the reaction characteristics and viscosity-temperature characteristics of the matrix in the BMI wet peel ply. The curing temperatures of the BMI wet peel ply and the BMI prepreg were the same (200 °C), making this wet peel ply suitable for co-curing with the BMI prepreg. After treatment with the wet peel ply, the bonding strength of the BMI composite joint showed a mean shear strength of 35.5 MPa, which was 1.72% higher than that of the sanded composite and 17.5% higher than that of the composite treated with the dry peel ply. In addition, the BMI composite treated with the BMI wet peel ply exhibited good bonding stability with a coefficient of variation of 3.9. After damp-heat aging for 1440 h, the retention rate of shear strength at room-temperature was 82.3%. The relatively loosely woven carrier in the BMI wet peel ply increased the surface roughness of the composite, thus improving the bonding strength. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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19 pages, 10236 KiB

Open AccessArticle

Mechanical Properties of Hybrid Carbonized Plant Fibers Reinforced Bio-Based Epoxy Laminates

by Edgar Adrián Franco-Urquiza, Raúl Samir Saleme-Osornio and Rodrigo Ramírez-Aguilar

Polymers 2021, 13(19), 3435; https://doi.org/10.3390/polym13193435 - 7 Oct 2021

Cited by 7 | Viewed by 1819

Abstract

In this work, henequen and ixlte plant fibers were carbonized in a horizontal quartz tube furnace. Several carbonized and non-carbonized fiber fabric configurations were impregnated with a bio-based epoxy resin through the infuseon process. The infrared spectra revealed characteristic bands of styrene instead [...] Read more.

In this work, henequen and ixlte plant fibers were carbonized in a horizontal quartz tube furnace. Several carbonized and non-carbonized fiber fabric configurations were impregnated with a bio-based epoxy resin through the infuseon process. The infrared spectra revealed characteristic bands of styrene instead of organic compounds, representing that the carbonization procedure was adequate to carbonize the plant fibers. The porosity volume ratio for the non-carbonized henequen laminates showed the highest number of voids >1.9%, and the rest of the composites had a similar void density between 1.2–1.7%. The storage modulus of the non-carbonized and carbonized henequen laminates resulted in 2268.5 MPa and 2092.1 MPa, respectively. The storage modulus of the carbonized ixtle laminates was 1541.4 MPa, which is 37.8% higher than the non-carbonized ixtle laminates and 12% higher than henequen composites. The laminates were subject to thermal shock cycling, and tomography scans revealed no alterations on the porosity level or in the cracks after the cycling procedure. Thermal shock cycling promoted the post-curing effect by increasing the glass transition temperature. The viscoelastic results showed a variation in the storage modulus when the carbonized fiber fabrics were located between natural fiber fabrics, which was attributed to more excellent compaction during the infusion process. Variations in the viscoelastic behavior were observed between the different types of natural fibers, which influenced the mechanical properties. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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14 pages, 6290 KiB

Open AccessArticle

Environmental Resistance and Fatigue Behaviors of Epoxy/Nano-Boron Nitride Thermally Conductive Structural Film Adhesive Toughened by Polyphenoxy

by Cheng’e Yue, Shaobo Dong, Ling Weng, Yazhen Wang and Liwei Zhao

Polymers 2021, 13(19), 3253; https://doi.org/10.3390/polym13193253 - 24 Sep 2021

Cited by 6 | Viewed by 2352

Abstract

The thermally conductive structural film adhesive not only carries large loads but also exhibits excellent heat-transfer performance, which has huge application prospects. Herein, a novel epoxy (Ep) thermally conductive structural film adhesive was prepared using polyphenoxy (PHO) as the toughening agent and film [...] Read more.

The thermally conductive structural film adhesive not only carries large loads but also exhibits excellent heat-transfer performance, which has huge application prospects. Herein, a novel epoxy (Ep) thermally conductive structural film adhesive was prepared using polyphenoxy (PHO) as the toughening agent and film former, boron nitride (BN) nanosheets as the thermally conductive filler, and polyester fabric as the carrier. When the amount of PHO in the epoxy matrix was 30 phr and the content of nano-BN was 30 wt.% (Ep/PHO30/nBN30), the adhesive resin system showed good film-forming properties, thermal stability, and thermal conductivity. The glass transition temperature of Ep/PHO30/nBN30 was 215 °C, and the thermal conductivity was 209.5% higher than that of the pure epoxy resin. The Ep/PHO30/nBN30 film adhesive possessed excellent adhesion and peeling properties, and the double-lap shear strength at room temperature reached 36.69 MPa, which was 21.3% higher than that of pure epoxy resin. The double-lap shear strength reached 15.41 MPa at 150 °C, demonstrating excellent high temperature resistance. In addition, the Ep/PHO30/nBN30 film adhesive exhibited excellent heat-aging resistance, humidity, and medium resistance, and the shear strength retention rate after exposure to the complicated environment reached more than 90%. The structural film adhesive prepared showed excellent fatigue resistance in the dynamic load fatigue test, the double-lap shear strength still reached 35.55 MPa after 1,000,000 fatigue cycles, and the strength retention rate was 96.9%, showing excellent durability and fatigue resistance. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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17 pages, 7590 KiB

Open AccessArticle

The Effect of Hybridisation on Mechanical Properties and Water Absorption Behaviour of Woven Jute/Ramie Reinforced Epoxy Composites

by Cionita Tezara, Agung Efriyo Hadi, Januar Parlaungan Siregar, Zalinawati Muhamad, Mohammad Hazim Mohamad Hamdan, Ahmed Nurye Oumer, Jamiluddin Jaafar, Agustinus Purna Irawan, Teuku Rihayat and Deni Fajar Fitriyana

Polymers 2021, 13(17), 2964; https://doi.org/10.3390/polym13172964 - 31 Aug 2021

Cited by 32 | Viewed by 3257

Abstract

Recently, the most critical issue related to the use of natural fibre-reinforced polymer composites (NFRPC) is the degradation properties of composites exposed to the environment. NFRPC’s moisture absorption behaviour has adverse effects on the composite’s mechanical properties and dimensional stability. The purpose of [...] Read more.

Recently, the most critical issue related to the use of natural fibre-reinforced polymer composites (NFRPC) is the degradation properties of composites exposed to the environment. NFRPC’s moisture absorption behaviour has adverse effects on the composite’s mechanical properties and dimensional stability. The purpose of this study is to analyse the mechanical properties of epoxy composites reinforced by jute–ramie hybridisation. This study also analysed the effect of stacking sequence hybridisation of the jute–ramie composite on water absorption behaviour. A five-layer different type of stacking sequence of single and hybrid jute–ramie is produced with the hand lay-up method. The results obtained from this study found that the mechanical properties and water absorption behaviour of a single jute fibre are lower compared to a single ramie fibre. The hybrid of jute–ramie has been able to increase the performance of composite compared to pure jute composites. The mechanical properties of the hybrid jute–ramie composite show a reduction effect after exposure to an aqueous environment due to the breakdown of fibre matrix interfacial bonding. However, after 28 days of immersion, all types of the stacking sequence’s mechanical properties are still higher than that of pure epoxy resin. In conclusion, the appropriate sequence of stacking and selecting the material used are two factors that predominantly affect the mechanical properties and water absorption behaviour. The hybrid composites with the desired and preferable properties can be manufactured using a hand-lay-up technique and used in the various industrial applications. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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9 pages, 6356 KiB

Open AccessCommunication

Enhanced Impact Properties of Hybrid Composites Reinforced by Carbon Fiber and Polyimide Fiber

by Boyao Wang, Bin He, Zhanwen Wang, Shengli Qi, Daijun Zhang, Guofeng Tian and Dezhen Wu

Polymers 2021, 13(16), 2599; https://doi.org/10.3390/polym13162599 - 5 Aug 2021

Cited by 23 | Viewed by 2725

Abstract

A series of hybrid fiber-reinforced composites were prepared with polyimide fiber and carbon fiber as the reinforcement and epoxy resin as the matrix. The influence of stacking sequence on the Charpy impact and flexural properties of the composites as well as the failure [...] Read more.

A series of hybrid fiber-reinforced composites were prepared with polyimide fiber and carbon fiber as the reinforcement and epoxy resin as the matrix. The influence of stacking sequence on the Charpy impact and flexural properties of the composites as well as the failure modes were studied. The results showed that hybrid fiber-reinforced composites yielded nearly 50% increment in Charpy impact strength compared with the ones reinforced by carbon fiber. The flexural performance was significantly improved compared with those reinforced solely by polyimide fibers and was greatly affected by the stacking sequence. The specimens with compressive sides distributed with carbon fiber possessed higher flexural strength, while those holding a sandwich-like structure with carbon fiber filling between the outer layers displayed a higher flexural modulus. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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11 pages, 1263 KiB

Open AccessArticle

Application of Micromechanical Modelling for the Evaluation of Elastic Moduli of Hybrid Woven Jute–Ramie Reinforced Unsaturated Polyester Composites

by Agung Efriyo Hadi, Mohammad Hazim Mohamad Hamdan, Januar Parlaungan Siregar, Ramli Junid, Cionita Tezara, Agustinus Purna Irawan, Deni Fajar Fitriyana and Teuku Rihayat

Polymers 2021, 13(15), 2572; https://doi.org/10.3390/polym13152572 - 1 Aug 2021

Cited by 11 | Viewed by 2960

Abstract

Woven laminated composite has gained researchers’ and industry’s interest over time due to its impressive mechanical performance compared to unidirectional composites. Nevertheless, the mechanical properties of the woven laminated composite are hard to predict. There are many micromechanical models based on unidirectional composite [...] Read more.

Woven laminated composite has gained researchers’ and industry’s interest over time due to its impressive mechanical performance compared to unidirectional composites. Nevertheless, the mechanical properties of the woven laminated composite are hard to predict. There are many micromechanical models based on unidirectional composite but limited to the woven laminated composite. The current research work was conducted to evaluate elastic moduli of hybrid jute–ramie woven reinforced unsaturated polyester composites using micromechanical effectiveness unidirectional models, such as ROM, IROM, Halpin–Tsai, and Hirsch, which are based on stiffness. The hybrid jute–ramie laminated composite was fabricated with different layering sizes, and the stacking sequence was completed via hand lay-up with the compression machine. Tensile modulus values for hybrid composites are between those for single jute and single ramie. Obtained p-values less than 0.05 prove the relationship between layering size and tensile modulus. This study showed that several micromechanical models, such as Halpin–Tsai’s predicted value of homogenized mechanical properties, were in good agreement with the experimental result. In the case of the hybrid composite, the micromechanical model deviates from the experimental result. Several modifications are required to improve the current existing model. A correlation function was calculated based on the differences between the elastic modulus values determined experimentally and those derived from each micromechanical model calculation. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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17 pages, 9412 KiB

Open AccessArticle

Moisture Absorption Behavior and Adhesion Properties of GNP/Epoxy Nanocomposite Adhesives

by Nurziana Kong, Nur Zalikha Khalil and Holger Fricke

Polymers 2021, 13(11), 1850; https://doi.org/10.3390/polym13111850 - 2 Jun 2021

Cited by 14 | Viewed by 4401

Abstract

In the current work, an attempt has been made to investigate the effect of Graphene Nanoplatelets (GNP) reinforcement to water absorption behavior and mechanical properties of adhesive bonding with epoxy. Epoxy adhesive with various GNP content (i.e., 0.0~2.0 wt%) was utilized to joint [...] Read more.

In the current work, an attempt has been made to investigate the effect of Graphene Nanoplatelets (GNP) reinforcement to water absorption behavior and mechanical properties of adhesive bonding with epoxy. Epoxy adhesive with various GNP content (i.e., 0.0~2.0 wt%) was utilized to joint aluminum adherend subjected to various immersion periods (i.e., 0~60 days). Subsequently, the effect of GNP reinforcement on water uptake, water absorption rate and tensile shear strength was investigated. Depending on GNP content, two distinct behaviors in water uptake and moisture absorption rate have been observed; specimens with lower GNP content (0.5~1.0 wt%) have demonstrated increased/retention of water uptake and water absorption rate regardless of immersion period. Meanwhile, at higher GNP content (1.5~2.0 wt%), decreased water uptake and water absorption rate are generally observed. At similar GNP content, regardless of immersion periods, water immersed specimens generally demonstrate higher or retention of shear strength when compared to specimens at 0-day immersion period. These observations suggest that the relation between moisture absorption behavior and mechanical properties of GNP-reinforced adhesive with GNP content are rather complex which might be attributed to the interplay of several possible mechanisms. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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15 pages, 6720 KiB

Open AccessArticle

Attapulgite–MXene Hybrids with Ti₃C₂T_x Lamellae Surface Modified by Attapulgite as a Mechanical Reinforcement for Epoxy Composites

by Lu Liu, Guobing Ying, Yinlong Zhao, Yuexia Li, Yiran Wu, Dong Wen, Meng Wu, Minghui Wang, Qingzhong Zhou, Xiang Wang and Cheng Wang

Polymers 2021, 13(11), 1820; https://doi.org/10.3390/polym13111820 - 31 May 2021

Cited by 12 | Viewed by 2942

Abstract

As a member of two-dimensional (2D) materials, MXene is an ideal reinforcement phase for modified polymers due to its large number of polar functional groups on the surface. However, it is still relatively difficult to modify any functional groups on the surface of [...] Read more.

As a member of two-dimensional (2D) materials, MXene is an ideal reinforcement phase for modified polymers due to its large number of polar functional groups on the surface. However, it is still relatively difficult to modify any functional groups on the surface of MXene at present, which limits its application in enhancing some polymers. Herein, one-dimensional (1D) attapulgite (ATP) nanomaterials were introduced onto the surface of MXene to form ATP–MXene hybrids, which successfully improved the mechanical properties of the epoxy composites. ATP with appropriate content can increase the surface roughness of the MXene lamellae to obtain better interface interaction. Therefore, remarkable enhancement on the mechanical property was achieved by adding M02A025 (0.2 wt % MXene and 0.25 wt % ATP), which is the optimum composition in the hybrids for composite mechanical properties. Compared to neat epoxy, the tensile strength, flexural strength and critical stress intensity factor (K_IC) of M02A025/epoxy are increased by 88%, 57%, and 195%, respectively, showing a high application prospect. Full article

(This article belongs to the Special Issue Mechanical and Adhesive Properties of Polymeric Materials)

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