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18 pages, 5766 KiB

Open AccessArticle

Thermal Degradation Studies of Poly(2-ethyl hexyl acrylate) in the Presence of Nematic Liquid Crystals

by Amina Bouriche, Lamia Alachaher-Bedjaoui, Ana Barrera, Jean-Noël Staelens and Ulrich Maschke

Polymers 2023, 15(19), 3934; https://doi.org/10.3390/polym15193934 - 29 Sep 2023

Cited by 2 | Viewed by 1279

Abstract

The thermal degradation behavior of Poly(2-ethyl hexyl hcrylate) (Poly(2-EHA)), blended with a commercially available nematic liquid crystal (LC) mixture, was investigated by thermal gravimetric analysis (TGA). Different heating rates, ranging from 5 to 200 °C/min, were applied under an inert atmosphere. Based on [...] Read more.

The thermal degradation behavior of Poly(2-ethyl hexyl hcrylate) (Poly(2-EHA)), blended with a commercially available nematic liquid crystal (LC) mixture, was investigated by thermal gravimetric analysis (TGA). Different heating rates, ranging from 5 to 200 °C/min, were applied under an inert atmosphere. Based on the TGA results, activation energies (E_α) at different conversion rates (α) were determined using three integral isoconversion methods: Flynn-Wall-Ozawa (FWO), Tang, and Kissinger-Akahira-Sunose (KAS). It can be noticed that the global evolution of these activation energies was the same for the three models. The coefficient of determination R² presented values generally higher than 0.97. Using these models, the E_α value for the LC remains constant at 64 kJ/mol for all conversions rates. For the polymer Poly(2-EHA), applying the Tang and FWO models, the activation energy presents a variation ranging from 80 kJ/mol, for conversion α = 0.1, to 170 kJ/mol, for α = 0.9. For the third model (KAS), this energy varies between 80 and 220 kJ/mol in the same range of α. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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22 pages, 6121 KiB

Open AccessArticle

Improvement of Chitosan Films Properties by Blending with Cellulose, Honey and Curcumin

by Noha G. Madian, Basant A. El-Ashmanty and Hadeel K. Abdel-Rahim

Polymers 2023, 15(12), 2587; https://doi.org/10.3390/polym15122587 - 6 Jun 2023

Cited by 9 | Viewed by 2148

Abstract

Chitosan is a natural biopolymer that can be used in biomedical applications, tissue engineering, and wound dressing because of its biodegradability, biocompatibility, and antibacterial activity. The blending of chitosan films with natural biomaterials such as cellulose, honey, and curcumin was studied at different [...] Read more.

Chitosan is a natural biopolymer that can be used in biomedical applications, tissue engineering, and wound dressing because of its biodegradability, biocompatibility, and antibacterial activity. The blending of chitosan films with natural biomaterials such as cellulose, honey, and curcumin was studied at different concentrations in order to improve their physical properties. Fourier transform infrared (FTIR) spectroscopy, mechanical tensile properties, X-ray diffraction (XRD), antibacterial effects, and scanning electron microscopy (SEM) were studied for all blended films. The XRD, FTIR, and mechanical results showed that films blended with curcumin were more rigid and compatible and had higher antibacterial effects than other blended films. In addition, XRD and SEM showed that blending chitosan films with curcumin decreases the crystallinity of the chitosan matrix compared to cellulose and honey blending films due to increased intermolecular hydrogen bonding, which reduces the close packing of the CS matrix. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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12 pages, 2173 KiB

Open AccessEditor’s ChoiceArticle

Polypropylene Degradation on Co-Rotating Twin-Screw Extruders

by Matthias Altepeter, Volker Schöppner, Sven Wanke, Laura Austermeier, Philipp Meinheit and Leon Schmidt

Polymers 2023, 15(9), 2181; https://doi.org/10.3390/polym15092181 - 4 May 2023

Cited by 4 | Viewed by 2504

Abstract

Nowadays, usable plastic materials with defined properties are created by blending additives into the base polymer. This is the main task of compounding on co-rotating twin-screw extruders. The thermal and mechanical stress occurring in the process leads to a mostly irreversible damage to [...] Read more.

Nowadays, usable plastic materials with defined properties are created by blending additives into the base polymer. This is the main task of compounding on co-rotating twin-screw extruders. The thermal and mechanical stress occurring in the process leads to a mostly irreversible damage to the material. Consequently, the properties of the polymer melt and the subsequent product are affected. The material degradation of polypropylene (PP) on a 28 mm twin-screw extruder has already been studied and modeled at Kunststofftechnik Paderborn. In this work, the transferability of the previous results to other machine sizes and polypropylene compounds were investigated experimentally. Therefore, pure polypropylene was processed with screw diameters of 25 mm and 45 mm. Furthermore, polypropylene compounds with titanium dioxide as well as carbon fibers were considered on a 28 mm extruder. In the course of the evaluation of the pure polypropylene, the melt flow rates of the samples were measured and the molar masses were calculated on this basis. The compounds were analyzed by gel permeation chromatography. As in the previous investigations, high rotational speeds, low throughputs and high melt temperatures lead to a higher material degradation. In addition, it is illustrated that the previously developed model for the calculation of material degradation is generally able to predict the degradation even for different machine sizes by adjusting the process coefficients. In summary, this article shows that compounders can use the recommendations for action and the calculation model for the material degradation of polypropylene, irrespective of the machine size, to design processes that are gentle on the material. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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12 pages, 2760 KiB

Open AccessArticle

Kinetic Analysis of Thermal Degradation of Recycled Polypropylene and Polystyrene Mixtures Using Regenerated Catalyst from Fluidized Catalytic Cracking Process (FCC)

by Paul Palmay, Leslie Pillajo, Mónica Andrade, Carlos Medina and Diego Barzallo

Polymers 2023, 15(9), 2035; https://doi.org/10.3390/polym15092035 - 25 Apr 2023

Cited by 2 | Viewed by 2324

Abstract

The pyrolysis process is a thermochemical recycling process that in recent years has gained importance due to its application in plastic waste, which is one of the biggest environmental problems today. Thus, it is essential to carry out kinetic and thermodynamic analyses to [...] Read more.

The pyrolysis process is a thermochemical recycling process that in recent years has gained importance due to its application in plastic waste, which is one of the biggest environmental problems today. Thus, it is essential to carry out kinetic and thermodynamic analyses to understand the thermocatalytic degradation processes involved in plastic waste mixtures. In this sense, the main objective of this study is to analyze the degradation kinetics of the specific mixture of polypropylene (25%) and polystyrene (75%) with 10% mass of regenerated FCC catalyst which was recovered from conventional refining processes using 3 heating rates at 5, 10 and 15 K min⁻¹ by thermogravimetric analysis (TGA). The obtained TGA data were compared with the isoconversional models used in this work that include Friedman (FR), Kissinger Akahira Sunose (KAS), Flynn–Wall–Ozawa (FWO), Starink (ST) and Miura–Maki (MM) in order to determine the one that best fits the experimental data and to analyze the activation energy and the pre-exponential factor; the model is optimized by means of the difference of minimum squares. Activation energy values between 148 and 308 kJ/mol were obtained where the catalytic action has been notorious, decreasing the activation energy values with respect to thermal processes. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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21 pages, 5944 KiB

Open AccessArticle

Effect of LNR-g-MMA on the Mechanical Properties and Lifetime Estimation of PLA/PP Blends

by Kraiwut Wisetkhamsai, Weerawat Patthaveekongka and Wanvimon Arayapranee

Polymers 2023, 15(7), 1712; https://doi.org/10.3390/polym15071712 - 29 Mar 2023

Viewed by 1934

Abstract

Polylactide (PLA) polymer, polypropylene (PP) polymer, and a PLA/PP (70:30 wt%) blend, with liquid natural rubber−graft−methy methacrylate (LNR−g−MMA) of 0.0, 2.5, 5.0, and 10.0 phr as compatibilizers, were prepared by internal mixing and compression molding. The effect of LNR-g-MMA content on the morphology, [...] Read more.

Polylactide (PLA) polymer, polypropylene (PP) polymer, and a PLA/PP (70:30 wt%) blend, with liquid natural rubber−graft−methy methacrylate (LNR−g−MMA) of 0.0, 2.5, 5.0, and 10.0 phr as compatibilizers, were prepared by internal mixing and compression molding. The effect of LNR-g-MMA content on the morphology, mechanical properties, water absorption, thermal degradation, and a lifetime of blends based on PLA and PP was investigated. Scanning electron microscopy (SEM) revealed that the PLA/PP blend underwent phase separation, and the presence of LNR−g−MMA in the PLA/PP blend showed a more homogenized and refined blend morphology. Hence, the addition of LNR−g−MMA was used as a compatibilizer to induce miscibility in the PLA/PP blend. The values of tensile strength, elongation at break, and impact strength of the polymer blends increased, whereas water absorption values decreased with increased LNR−g−MMA content. Thermal degradation kinetics was studied over a temperature range of 50–800 °C with multiple heating rates. The results demonstrated that the thermal stability of blends without LNR-g-MMA was greater than that of blends with LNR−g−MMA and that the thermal stability decreased with increasing LNR−g−MMA content. The activation energy (E_a) was calculated by using the Kissinger–Akahira–Sunose method. The E_a value of PLA was much lower than that of PP, and incorporating PP in the PLA matrix increased the E_a. The addition of LNR−g−MMA to the PLA/PP blend decreased the E_a. The lifetime of PLA/PP blends was reduced with the addition of LNR−g−MMA. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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17 pages, 5120 KiB

Open AccessArticle

The Effect of Accelerated Aging on the Molecular Weight and Thermal and Mechanical Properties of Polyester Yarns Containing Ceramic Particles

by Gabriela Mijas, Marta Riba-Moliner and Diana Cayuela

Polymers 2023, 15(6), 1348; https://doi.org/10.3390/polym15061348 - 8 Mar 2023

Cited by 3 | Viewed by 2034

Abstract

The accelerated aging of polyethylene terephthalate (PET) multifilament yarns containing nano or microparticles of titanium dioxide (TiO₂), silicon carbide (SiC), or fluorite (CaF₂) at a maximum percentage of 2% has been studied. For this, the yarn samples were introduced [...] Read more.

The accelerated aging of polyethylene terephthalate (PET) multifilament yarns containing nano or microparticles of titanium dioxide (TiO₂), silicon carbide (SiC), or fluorite (CaF₂) at a maximum percentage of 2% has been studied. For this, the yarn samples were introduced into a climatic chamber at 50 °C, 50% relative humidity, and an ultraviolet A (UVA) irradiance of 1.4 W/m². They were then removed from the chamber after periods of between 21 and 170 days of exposure. Subsequently, the variation in weight average molecular weight, number molecular weight, and polydispersity was evaluated by gel permeation chromatography (GPC), the surface appearance was evaluated using scanning electron microscopy (SEM), the thermal properties were evaluated using differential scanning calorimetry (DSC), and the mechanical properties were evaluated using dynamometry. The results showed that, at the test conditions, there was degradation in all of the exposed substrates, possibly due to the excision of the chains that make up the polymeric matrix, which resulted in the variation in the mechanical and thermal properties depending on the type and size of the particle used. This study provides insight into the evolution of the properties of PET-based nano- and microcomposites and might be helpful when selecting materials for specific applications, which is of great interest from an industrial point of view. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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17 pages, 6111 KiB

Open AccessEditor’s ChoiceArticle

Effect of Aging on Unidirectional Composite Laminate Polyethylene for Body Armor

by Amy Engelbrecht-Wiggans, Zois Tsinas, Ajay Krishnamurthy and Amanda L. Forster

Polymers 2023, 15(6), 1347; https://doi.org/10.3390/polym15061347 - 8 Mar 2023

Cited by 4 | Viewed by 1959

Abstract

The construction of ballistic-resistant body armor is experiencing an increasing use of flexible unidirectional (UD) composite laminates that comprise multiple layers. Each UD layer contains hexagonally packed high-performance fibers with a very low modulus matrix (sometimes referred to as binder resins). Laminates are [...] Read more.

The construction of ballistic-resistant body armor is experiencing an increasing use of flexible unidirectional (UD) composite laminates that comprise multiple layers. Each UD layer contains hexagonally packed high-performance fibers with a very low modulus matrix (sometimes referred to as binder resins). Laminates are then made from orthogonal stacks of these layers, and these laminate-based armor packages offer significant performance advantages over standard woven materials. When designing any armor system, the long-term reliability of the armor materials is critical, particularly with regard to stability with exposure to temperature and humidity, as these are known causes of degradation in commonly used body armor materials. To better inform future armor designers, this work investigates the tensile behavior of an ultra-high molar mass polyethylene (UHMMPE) flexible UD laminate that was aged for at least 350 d at two accelerated conditions: 70 °C at 76% relative humidity (RH) and 70 °C in a desiccator. Tensile tests were performed at two different loading rates. The mechanical properties of the material after ageing demonstrated less than 10% degradation in tensile strength, indicating high reliability for armor made from this material. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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11 pages, 1284 KiB

Open AccessArticle

Microplastic Removal from Drinking Water Using Point-of-Use Devices

by Ashlyn G. Cherian, Zeyuan Liu, Michael J. McKie, Husein Almuhtaram and Robert C. Andrews

Polymers 2023, 15(6), 1331; https://doi.org/10.3390/polym15061331 - 7 Mar 2023

Cited by 15 | Viewed by 5753

Abstract

The occurrence of microplastics in drinking water has drawn increasing attention due to their ubiquity and unresolved implications regarding human health. Despite achieving high reduction efficiencies (70 to >90%) at conventional drinking water treatment plants (DWTPs), microplastics remain. Since human consumption represents a [...] Read more.

The occurrence of microplastics in drinking water has drawn increasing attention due to their ubiquity and unresolved implications regarding human health. Despite achieving high reduction efficiencies (70 to >90%) at conventional drinking water treatment plants (DWTPs), microplastics remain. Since human consumption represents a small portion of typical household water use, point-of-use (POU) water treatment devices may provide the additional removal of microplastics (MPs) prior to consumption. The primary objective of this study was to evaluate the performance of commonly used pour-through POU devices, including those that utilize combinations of granular activated carbon (GAC), ion exchange (IX), and microfiltration (MF), with respect to MP removal. Treated drinking water was spiked with polyethylene terephthalate (PET) and polyvinyl chloride (PVC) fragments, along with nylon fibers representing a range of particle sizes (30–1000 µm) at concentrations of 36–64 particles/L. Samples were collected from each POU device following 25, 50, 75, 100 and 125% increases in the manufacturer’s rated treatment capacity, and subsequently analyzed via microscopy to determine their removal efficiency. Two POU devices that incorporate MF technologies exhibited 78–86% and 94–100% removal values for PVC and PET fragments, respectively, whereas one device that only incorporates GAC and IX resulted in a greater number of particles in its effluent when compared to the influent. When comparing the two devices that incorporate membranes, the device with the smaller nominal pore size (0.2 µm vs. ≥1 µm) exhibited the best performance. These findings suggest that POU devices that incorporate physical treatment barriers, including membrane filtration, may be optimal for MP removal (if desired) from drinking water. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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13 pages, 5720 KiB

Open AccessArticle

Microscopic Mechanism of Electrical Aging of PVDF Cable Insulation Material

by Zhiyi Pang, Yi Li, Hanbo Zheng and Rui Qin

Polymers 2023, 15(5), 1286; https://doi.org/10.3390/polym15051286 - 3 Mar 2023

Cited by 3 | Viewed by 2175

Abstract

In this study, the quantum chemical method was used to investigate the microscopic characteristics of α-poly viny difluoride (PVDF) molecules under the influence of an electric field, and the impact of mechanical stress and electric field polarization on the insulation performance of PVDF [...] Read more.

In this study, the quantum chemical method was used to investigate the microscopic characteristics of α-poly viny difluoride (PVDF) molecules under the influence of an electric field, and the impact of mechanical stress and electric field polarization on the insulation performance of PVDF was analyzed through the material’s structural and space charge characteristics. The findings reveal that long-term polarization of an electric field leads to a gradual decline in stability and a reduction in the energy gap of the front orbital, resulting in the improved conductivity of PVDF molecules and a change in the reactive active site of the molecular chain. When the energy gap reaches a certain value, a chemical bond fracture occurs, with the C-H and C-F bonds at the ends of the backbone breaking first to form free radicals. This process is triggered by an electric field of 8.7414 × 10⁹ V/m, which leads to the emergence of a virtual frequency in the infrared spectrogram and the eventual breakdown of the insulation material. These results are of great significance in understanding the aging mechanism of electric branches in PVDF cable insulation and optimizing the modification of PVDF insulation materials. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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17 pages, 5608 KiB

Open AccessArticle

Sustainable Engineered Design and Scalable Manufacturing of Upcycled Graphene Reinforced Polylactic Acid/Polyurethane Blend Composites Having Shape Memory Behavior

by Busra Cetiner, Gulayse Sahin Dundar, Yusuf Yusufoglu and Burcu Saner Okan

Polymers 2023, 15(5), 1085; https://doi.org/10.3390/polym15051085 - 21 Feb 2023

Cited by 13 | Viewed by 2389

Abstract

Material design in shape memory polymers (SMPs) carries significant importance in attaining high performance and adjusting the interface between additive and host polymer matrix to increase the degree of recovery. Herein, the main challenge is to enhance the interfacial interactions to provide reversibility [...] Read more.

Material design in shape memory polymers (SMPs) carries significant importance in attaining high performance and adjusting the interface between additive and host polymer matrix to increase the degree of recovery. Herein, the main challenge is to enhance the interfacial interactions to provide reversibility during deformation. The present work describes a newly designed composite structure by manufacturing a high-degree biobased and thermally induced shape memory polylactic acid (PLA)/thermoplastic polyurethane (TPU) blend incorporated with graphene nanoplatelets obtained from waste tires. In this design, blending with TPU enhances flexibility, and adding GNP provides functionality in terms of mechanical and thermal properties by enhancing circularity and sustainability approaches. The present work provides a scalable compounding approach for industrial applications of GNP at high shear rates during the melt mixing of single/blend polymer matrices. By evaluating the mechanical performance of the PLA and TPU blend composite composition at a 9:1 weight percentage, the optimum GNP amount was defined as 0.5 wt%. The flexural strength of the developed composite structure was enhanced by 24% and the thermal conductivity by 15%. In addition, a 99.8% shape fixity ratio and a 99.58% recovery ratio were attained within 4 min, resulting in the spectacular enhancement of GNP attainment. This study provides an opportunity to understand the acting mechanism of upcycled GNP in improving composite formulations and to develop a new perspective on the sustainability of PLA/TPU blend composites with an increased biobased degree and shape memory behavior. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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25 pages, 9096 KiB

Open AccessArticle

Effects of Bamboo Leaf Fiber Content on Cushion Performance and Biodegradability of Natural Rubber Latex Foam Composites

by Keavalin Jitkokkruad, Kasama Jarukumjorn, Chaiwat Raksakulpiwat, Saowapa Chaiwong, Jutarat Rattanakaran and Tatiya Trongsatitkul

Polymers 2023, 15(3), 654; https://doi.org/10.3390/polym15030654 - 27 Jan 2023

Cited by 7 | Viewed by 5161

Abstract

Bamboo leaf fiber (BLF) was incorporated into an eco-friendly foam cushion made from natural rubber latex (NRL) to enhance the biodegradation rate. The objective of this work was to investigate the effects of BLF content on the foam structure, mechanical properties, cushion performance, [...] Read more.

Bamboo leaf fiber (BLF) was incorporated into an eco-friendly foam cushion made from natural rubber latex (NRL) to enhance the biodegradation rate. The objective of this work was to investigate the effects of BLF content on the foam structure, mechanical properties, cushion performance, and biodegradability. The NRL foam cushion nets with and without BLF were prepared using the Dunlop method along with microwave-assisted vulcanization. BLF (90–106 µm in length) at various loadings (0.00, 2.50, 5.00, 7.50, and 10.00 phr) were introduced to the latex compounds before gelling and vulcanizing steps. Scanning electron microscopy (SEM) showed that the BLF in a NRL foam caused an increase in cell size and a decrease in the number of cells. The changes in the cell structure and number of cells resulted in increases in the bulk density, hardness, compression set, compressive strength, and cushion coefficient. A soil burial test of 24 weeks revealed faster weight loss of 1.8 times when the BLF content was 10.00 phr as compared to the NRL foam without BLF. The findings of this work suggest the possibility of developing an eco-friendly cushion with a faster degradation rate while maintaining cushion performance, which could be a better alternative for sustainable packaging in the future. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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11 pages, 2183 KiB

Open AccessArticle

The Effect of Shear on the Properties of an Associated Polymer Solution for Oil Displacement

by Guoying Jiao, Shijie Zhu, Zhongbin Ye, Zheng Shu, Xijin Wang and Daming Wang

Polymers 2023, 15(3), 616; https://doi.org/10.3390/polym15030616 - 25 Jan 2023

Cited by 5 | Viewed by 2059

Abstract

Polymer flooding is one of the techniques used to enhance oil recovery from depleted hydrocarbon reservoirs. Although this technology is popular for this application, the shearing effect in the injection process causes poor performance, which is an obstacle to meeting the needs of [...] Read more.

Polymer flooding is one of the techniques used to enhance oil recovery from depleted hydrocarbon reservoirs. Although this technology is popular for this application, the shearing effect in the injection process causes poor performance, which is an obstacle to meeting the needs of the formation. An experimental evaluation of the rheological properties, viscoelasticity, hydrodynamic size, static adsorption, and seepage characteristics of the associated polymer solution before and after shearing was conducted to determine the influence of shearing on the polymer solution. The results show that the effect of shear on the polymer was irreversible, and the properties of the polymer solution damaged by shear were attenuated. After the critical associating concentration, the associated polymer can recover its solution properties through hydrophobic association, which can improve the shear resistance of the polymer solution and make its own rheological law and reduce the viscoelastic change. Although the hydrodynamic size, viscoelasticity, and adsorption capacity of the polymer solution after shear failure decreased, strong flow resistance during porous media seepage and mobility control was achieved. Improving the shear resistance of the polymer solution by increasing the intermolecular force is proposed to develop new polymer systems for subsequent oil displacement. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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16 pages, 3086 KiB

Open AccessEditor’s ChoiceArticle

Insight into Degrading Effects of Two Fungi on Polyurethane Coating Failure in a Simulated Atmospheric Environment

by Xiangping Hao, Kexin Yang, Dawei Zhang and Lin Lu

Polymers 2023, 15(2), 328; https://doi.org/10.3390/polym15020328 - 9 Jan 2023

Cited by 3 | Viewed by 2106

Abstract

Two different fungi, Talaromyces funiculosus (T. funiculosus) and Phanerochaete chrysosporium (P. chrysosporium), were collected from the Xishuangbanna atmospheric corrosion site and incubated on a polyurethane (PU) coating at 30 °C for two weeks under 95% relative humidity (RH). The biodegrading [...] Read more.

Two different fungi, Talaromyces funiculosus (T. funiculosus) and Phanerochaete chrysosporium (P. chrysosporium), were collected from the Xishuangbanna atmospheric corrosion site and incubated on a polyurethane (PU) coating at 30 °C for two weeks under 95% relative humidity (RH). The biodegrading effects of these fungi on the coating failure were investigated from aspects of metabolism and electrochemistry. The results showed that T. funiculosus contributed more to the degradation of the PU coating failure than P. chrysosporium, and two factors played dominant roles. First, the weight of the T. funiculosus mycelium was nearly 3 times more than that of P. chrysosporium, indicating there was more substrate mycelium of T. funiculosus deep into the coatings to get more nutrition in atmospheric during colonization. Second, T. funiculosus secreted carboxylic acids, such as citric, propanoic, succinic, and tartaric acids, and accelerated the hydrolysis of the ester and urethane bonds in the PU coatings. As a result, the mycelium of T. funiculosus readily penetrated the interface of the coating and substrate resulting in a rapid proliferation. Thus, the |Z|_0.01Hz value of the coating decreased to 5.1 × 10⁴ Ω·cm² after 14 days of colonization by T. funiculosus while the value remained at 7.2 × 10⁷ Ω·cm² after colonization by P. chrysosporium. These insights suggest that the biodegradation process in simulated atmospheric environments would provide theoretical guidance and directions for the design of antifungal PU coatings. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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16 pages, 4168 KiB

Open AccessArticle

Catalytic Pyrolysis of Polystyrene Waste in Hydrocarbon Medium

by Konstantin I. Dement’ev, Stanislav P. Bedenko, Yulia D. Minina, Aniya A. Mukusheva, Olga A. Alekseeva and Timur A. Palankoev

Polymers 2023, 15(2), 290; https://doi.org/10.3390/polym15020290 - 6 Jan 2023

Cited by 5 | Viewed by 2564

Abstract

The fast catalytic pyrolysis of polystyrene in the hydrocarbon medium (light and heavy cycle oil) over zeolite catalysts at 450–550 °C was investigated. The influence of reaction conditions (medium, temperature, vapor residence time, polystyrene concentration) on polymer conversion and product distribution was studied. [...] Read more.

The fast catalytic pyrolysis of polystyrene in the hydrocarbon medium (light and heavy cycle oil) over zeolite catalysts at 450–550 °C was investigated. The influence of reaction conditions (medium, temperature, vapor residence time, polystyrene concentration) on polymer conversion and product distribution was studied. It was found that the polymer conversion is close to 100%, while ethylbenzene, benzene, and toluene are the main products of its transformation. The maximum yield of ethylbenzene (80%) was achieved at 550 °C, vapor residence time 1–2 s, polystyrene concentration 10%, and heavy cycle oil as the medium. The influence of zeolite topology on product distribution was explored. The possible mechanism of polystyrene pyrolysis was proposed. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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15 pages, 3739 KiB

Open AccessArticle

Improvement in Acid Resistance of Polyimide Membranes: A Sustainable Cross-Linking Approach via Green-Solvent-Based Fenton Reaction

by Srinath Ravi, Woo-Seok Kang, Hyung-Kae Lee, You-In Park, Hosik Park, In-Chul Kim and Young-Nam Kwon

Polymers 2023, 15(2), 264; https://doi.org/10.3390/polym15020264 - 4 Jan 2023

Cited by 2 | Viewed by 2529

Abstract

In this study, we present a facile surface modification method using green solvents for a commercial polyimide (PI) nanofiltration membrane to exhibit good acid stability. To enhance acid stability, the PI organic solvent nanofiltration membrane was modified using Fenton’s reaction, an oxidative cross-linking [...] Read more.

In this study, we present a facile surface modification method using green solvents for a commercial polyimide (PI) nanofiltration membrane to exhibit good acid stability. To enhance acid stability, the PI organic solvent nanofiltration membrane was modified using Fenton’s reaction, an oxidative cross-linking process, using environmentally friendly solvents: water and ethanol. The surface properties of the pristine and modified PI membranes were investigated and compared using various analytical tools. We studied the surface morphology using scanning electron microscopy, performed elemental analysis using X-ray photoelectron spectroscopy, investigated chemical bonds using attenuated total reflectance-Fourier transform infrared spectroscopy, and studied thermal stability using thermogravimetric analysis. The acid resistances of the pristine and modified membranes were confirmed through performance tests. The pristine PI nanofiltration membrane exposed to a 50 w/v% sulfuric acid for 4 h showed an increase in the normalized water flux to 205% and a decrease in the MgSO₄ normalized rejection to 44%, revealing damage to the membrane. The membrane modified by the Fenton reaction exhibited a decline in flux and improved rejection, which are typical performance changes after surface modification. However, the Fenton-modified membrane exposed to 50 w/v% sulfuric acid for 4 h showed a flux increase of 7% and a rejection increase of 4%, indicating improved acid resistance. Furthermore, the Fenton post-treatment enhanced the thermal stability and organic solvent resistance of the PI membrane. This study shows that the acid resistance of PI membranes can be successfully improved by a novel and facile Fenton reaction using green solvents. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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15 pages, 2393 KiB

Open AccessEditor’s ChoiceArticle

Studying the Physical and Chemical Properties of Polydimethylsiloxane Matrix Reinforced by Nanostructured TiO₂ Supported on Mesoporous Silica

by Sari Katz, Noa Lachman, Nir Hafif, Lilach Rosh, Alexander Pevzner, Amir Lybman, Tal Amitay-Rosen, Ido Nir and Hadar Rotter

Polymers 2023, 15(1), 81; https://doi.org/10.3390/polym15010081 - 25 Dec 2022

Cited by 6 | Viewed by 3874

Abstract

In this study, a reactive adsorbent filler was integrated into a polymeric matrix as a novel reactive protective barrier without undermining its mechanical, thermal, and chemical properties. For this purpose, newly synthesized TiO₂/MCM/polydimethylsiloxane (PDMS) composites were prepared, and their various properties [...] Read more.

In this study, a reactive adsorbent filler was integrated into a polymeric matrix as a novel reactive protective barrier without undermining its mechanical, thermal, and chemical properties. For this purpose, newly synthesized TiO₂/MCM/polydimethylsiloxane (PDMS) composites were prepared, and their various properties were thoroughly studied. The filler, TiO₂/MCM, is based on a (45 wt%) TiO₂ nanoparticle catalyst inside the pores of ordered mesoporous silica, MCM-41, which combines a high adsorption capacity and catalytic capability. This study shows that the incorporation of TiO₂/MCM significantly enhances the composite’s Young’s modulus in terms of tensile strength, as an optimal measurement of 1.6 MPa was obtained, compared with that of 0.8 MPa of pristine PDMS. The composites also showed a higher thermal stability, a reduction in the coefficient of thermal expansion (from 290 to 110 ppm/°C), a 25% reduction in the change in the normalized specific heat capacity, and an increase in the thermal degradation temperatures. The chemical stability in organic environments was improved, as toluene swelling decreased by 40% and the contact angle increased by ~15°. The enhanced properties of the novel synthesized TiO₂/MCM/PDMS composite can be used in various applications where a high adsorption capacity and catalytic/photocatalytic activity are required, such as in protective equipment, microfluidic applications, and chemical sensor devices. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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13 pages, 3400 KiB

Open AccessArticle

Selective Solvolysis of Bio-Based PU-Coated Fabric

by David De Smet, Jente Verjans and Myriam Vanneste

Polymers 2022, 14(24), 5452; https://doi.org/10.3390/polym14245452 - 13 Dec 2022

Cited by 9 | Viewed by 2869

Abstract

Polyurethane (PU) coatings are widely applied on high performing textiles due to their excellent durability and mechanical properties. PUs based on renewable resources were developed to improve the environmental impact of coatings by decreasing the carbon footprint. However, at the end-of-life, PU-coated textiles [...] Read more.

Polyurethane (PU) coatings are widely applied on high performing textiles due to their excellent durability and mechanical properties. PUs based on renewable resources were developed to improve the environmental impact of coatings by decreasing the carbon footprint. However, at the end-of-life, PU-coated textiles still end up as landfill or are incinerated since PUs are not biodegradable and are not being recycled at this moment. Therefore, the recycling of PU-coated substrates needs to be examined. This study reports the selective solvolysis of a polyester (PET) fabric coated with a bio-based PU using a 70% ZnCl₂ aqueous solution. This method allowed the easy separation of the coating from the fabric. The thermal, chemical and mechanical characteristics of the virgin PET and recycled PET were examined via tensile strength tests, IR, TGA, DSC and GPC. Analysis of the fractions after solvolysis revealed that the PU was converted into the original polyol and an amine, corresponding to the isocyanate used for PU synthesis. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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13 pages, 3357 KiB

Open AccessArticle

Large-Scale Preparation of Uniform Millet Bread-like Durable Benzoxazine-Phthalonitrile Foam with Outstanding Mechanical and Thermal Properties

by Wenwu Lei, Dengyu Wang, Qi Liu, Kui Li, Ying Li, Fei Zhong, Qiancheng Liu, Pan Wang, Wei Feng and Xulin Yang

Polymers 2022, 14(24), 5410; https://doi.org/10.3390/polym14245410 - 10 Dec 2022

Cited by 5 | Viewed by 1805

Abstract

It is essentially important to develop durable polymer foams for services in high-temperature conditions. The current study reported the preparations and properties of a high-performance benzoxazine-phthalonitrile (BZPN) foam by utilizing azodicarbonamide and tween-80 as the blowing agent and stabilizer, respectively. Rheological and curing [...] Read more.

It is essentially important to develop durable polymer foams for services in high-temperature conditions. The current study reported the preparations and properties of a high-performance benzoxazine-phthalonitrile (BZPN) foam by utilizing azodicarbonamide and tween-80 as the blowing agent and stabilizer, respectively. Rheological and curing studies indicated that the appropriate foaming temperature for BZPN foam is below 180 °C, and its foaming viscosity window is below 20 Pa·s. Guided by these results, uniform millet bread-like BZPN foams with decimeter leveling size were successfully realized, suggesting the high prospect of large-scale production. The structural, mechanical, and thermal properties of BZPN foams were then investigated in detail. BZPN foam involves a hierarchical fracture mechanism during the compressive test, and it shows a high compression strength of over 6 MPa. During a burning test over 380 °C, no visible smoke, softening, or droplet phenomena appeared and the macroscopic structure of BZPN foam was well maintained. Mechanically robust, flame-retardant, and uniform large-size BZPN foam are promising light durable materials with high service temperatures, i.e., as filling materials even in a very narrow pipette. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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13 pages, 10225 KiB

Open AccessArticle

Analysis of Erosion Characteristics and Erosion Mechanism of Polypropylene Fiber Tailings Recycled Concrete in Salt Spray Environment

by Xiuyun Chen, Tao Li, Meng Zhan, Yijie Ding, Faguang Leng and Jia Sun

Polymers 2022, 14(23), 5137; https://doi.org/10.3390/polym14235137 - 25 Nov 2022

Cited by 2 | Viewed by 1373

Abstract

Economic development and infrastructure improvement will inevitably lead to the accumulation of construction waste and tailings, which has not only a huge impact on the environment but is also a waste of resources. Recycling these resources and making green concrete is an effective [...] Read more.

Economic development and infrastructure improvement will inevitably lead to the accumulation of construction waste and tailings, which has not only a huge impact on the environment but is also a waste of resources. Recycling these resources and making green concrete is an effective way to solve these problems. In this study, the salt spray erosion characteristics and erosion mechanism of tailings recycled concrete (TRC) with polypropylene fibers were studied through macro and micro methods. The results showed that its compressive strength and splitting tensile strength increased at first and then decreased, with the optimum content of 0.6–0.9%, and the strength increase coefficient reached its maximum value at the erosion period being 14 d to 28 d. Under the same erosion cycle, when the fiber content was low (≤0.6–0.9%), the erosion depth hardly fluctuated. While the fiber content changed from 0.6% to 1.2%, the erosion depth and curing ability (erosion for 90 days) increased by 16.29% and 11.20%, which implied that its erosion resistance decreased sharply. Through SEM microscopic analysis, it could be observed that when the fiber content was low, the matrix structure and porosity had little change; while the fiber content was excessive, the porosity increased greatly. The longer the erosion period was, the greater the cumulative expansion of salt crystals was, and the larger the porosity was, whose results were in good agreement with the experimental results. This research provides a significant theoretical basis for the application of TRC in engineering. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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15 pages, 5776 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Wear Phenomena Produced by Erosion with Abrasive Particles against Fluoropolymeric Coatings

by Guillermo Guerrero-Vaca and Oscar Rodríguez-Alabanda

Polymers 2022, 14(21), 4617; https://doi.org/10.3390/polym14214617 - 31 Oct 2022

Cited by 7 | Viewed by 2197

Abstract

To date, PTFE, PFA, and FEP-based fluoropolymer coatings have proven unbeatable in many services due to their excellent chemical inertness, very low wettability, thermal resistance, high non-stick properties, and good applicability. In use, these coatings usually suffer service cycles with consequent deterioration, and [...] Read more.

To date, PTFE, PFA, and FEP-based fluoropolymer coatings have proven unbeatable in many services due to their excellent chemical inertness, very low wettability, thermal resistance, high non-stick properties, and good applicability. In use, these coatings usually suffer service cycles with consequent deterioration, and it is of great interest to determine the intensity and type of wear caused in addition to the deterioration that occurs in their properties. In this work, the response of three polymeric coatings of interest applied to aluminum substrates, after being subjected to the action of abrasive particles of aluminum corundum, glass, and plastic projected under pressure, has been studied. During the application of a given wear cycle, the hardness, surface roughness, surface texture, and thickness of the coating have been measured, in addition to the slip angle and surface transmittance to analyze the evolution of each type of coating. The results allowed a concise evaluation of the performance of three fluoropolymeric coatings of great interest, differentiating the induced erosive wear phenomena and contributing complete information to facilitate the correct selection for users with practical application purposes and as a basis for future research work focused on advancements in this field. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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21 pages, 497 KiB

Open AccessEditor’s ChoiceReview

Hydrothermal Ageing of Glass Fibre Reinforced Vinyl Ester Composites: A Review

by James Thomason and Georgios Xypolias

Polymers 2023, 15(4), 835; https://doi.org/10.3390/polym15040835 - 8 Feb 2023

Cited by 14 | Viewed by 3263

Abstract

The use of glass fibre-reinforced polymer (GFRP) composites in load-carrying constructions has significantly increased over the last few decades. Such GFRP composite structures may undergo significant changes in performance as a consequence of long-term environmental exposure. Vinyl ester (VE) resins are a class [...] Read more.

The use of glass fibre-reinforced polymer (GFRP) composites in load-carrying constructions has significantly increased over the last few decades. Such GFRP composite structures may undergo significant changes in performance as a consequence of long-term environmental exposure. Vinyl ester (VE) resins are a class of thermosetting polymers increasingly being used in such structural composites. This increasing use of VE-based GFRPs in such applications has led to an increasing need to better understand the consequences of long-term environmental exposure on their performance. The reliable validation of the environmental durability of new VE-based GFRPs can be a time- and resource-consuming process involving costly testing programs. Accelerated hydrothermal ageing is often used in these investigations. This paper reviews the relevant literature on the hydrothermal ageing of vinyl ester-based GFRP with special attention to the fundamental background of moisture-induced ageing of GFRP, the important role of voids, and the fibre-matrix interface, on composite mechanical performance. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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20 pages, 1065 KiB

Open AccessFeature PaperReview

Methods of Analyses for Biodegradable Polymers: A Review

by Siti Baidurah

Polymers 2022, 14(22), 4928; https://doi.org/10.3390/polym14224928 - 15 Nov 2022

Cited by 35 | Viewed by 9965

Abstract

Biodegradable polymers are materials that can decompose through the action of various environmental microorganisms, such as bacteria and fungi, to form water and carbon dioxide. The biodegradability characteristics have led to a growing demand for the accurate and precise determination of the degraded [...] Read more.

Biodegradable polymers are materials that can decompose through the action of various environmental microorganisms, such as bacteria and fungi, to form water and carbon dioxide. The biodegradability characteristics have led to a growing demand for the accurate and precise determination of the degraded polymer composition. With the advancements in analytical product development, various analytical methods are available and touted as practical and preferable methods of bioanalytical techniques, which enable the understanding of the complex composition of biopolymers such as polyhydroxyalkanoates and poly(lactic acid). The former part of this review discusses the definition and examples of biopolymers, followed by the theory and instrumentation of analytical methods applicable to the analysis of biopolymers, such as physical methods (SEM, TEM, weighing analytical balance, etc.), chromatographic methods (GC, THM-GC, SEC/GPC), spectroscopic methods (NMR, FTIR, XRD, XRF), respirometric methods, thermal methods (DSC, DTA, TGA), and meta-analysis. Special focus is given to the chromatographic methods, because this is the routine method of polymer analysis. The aim of this review is to focus on the recent developments in the field of biopolymer analysis and instrument application to analyse the various types of biopolymers. Full article

(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials II)

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