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18 pages, 7244 KiB

Open AccessArticle

Influence of Aging on the Physical Properties of Knitted Polymeric Materials

by Antonija Petrov, Ivana Salopek Čubrić and Goran Čubrić

Polymers 2024, 16(4), 513; https://doi.org/10.3390/polym16040513 - 14 Feb 2024

Viewed by 583

Abstract

Nowadays, as consumer expectations have increased worldwide, the importance of polymer materials performance has been raised to a new level. Efforts are required to produce a high-quality product that maintains its quality despite aging factors in certain geographical locations. In the experimental part [...] Read more.

Nowadays, as consumer expectations have increased worldwide, the importance of polymer materials performance has been raised to a new level. Efforts are required to produce a high-quality product that maintains its quality despite aging factors in certain geographical locations. In the experimental part of this study, polyester materials produced from conventional and recycled yarns, further intended for the production of sportswear, were exposed to natural weathering. Before and after the exposure, the following material properties were investigated: material surface appearance, material thickness, mass per unit area, horizontal and vertical density, surface roughness, tensile properties (force at break, elongation at break), water vapor permeability, liquid dispersion and drying of the material. The results indicate that the surface mass and thickness of all exposed polyester materials decreased after aging due to material shrinkage. The results indicated that prolonged aging negatively affected the values of elongation and force at break. The recycled material exhibited the highest overall decreases in elongation and force at break, but lower surface roughness. In addition, recycled material exhibited a shorter drying time than that of conventional material, both before and after aging. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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21 pages, 11824 KiB

Open AccessArticle

Degradation Behavior of Biodegradable Man-Made Fibers in Natural Soil and in Compost

by Pia Borelbach, Rodion Kopitzky, Jörg Dahringer and Patrick Gutmann

Polymers 2023, 15(13), 2959; https://doi.org/10.3390/polym15132959 - 06 Jul 2023

Cited by 5 | Viewed by 2088

Abstract

In open environment applications, fibers are increasingly being used that are expected to biodegrade in the soil after their desired service life. Biodegradable polymer fibers are a versatile alternative to natural fibers. In this study, the degradation behavior of fibers made from polylactic [...] Read more.

In open environment applications, fibers are increasingly being used that are expected to biodegrade in the soil after their desired service life. Biodegradable polymer fibers are a versatile alternative to natural fibers. In this study, the degradation behavior of fibers made from polylactic acid (PLA) and a polyhydroxy alkanoate (PHA) blend with PLA, as well as a bicomponent fiber (BICO) made from polybutylene succinate (PBS) and PLA, was investigated. The fibers were stored in topsoil at 23 °C for 12 weeks. In addition, fibers were stored in compost at 58 °C for 4 weeks to investigate the degradation behavior in an industrial composting plant. Reference materials were also stored without substrate under the same temperatures and humidity conditions. Samples were taken regularly, and mechanical testing, scanning electron microscopy (SEM), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and infrared spectroscopy (IR) were used to study the degradation of the fibers. After 12 weeks in soil at ambient temperatures, the PLA and BICO fibers showed no degradation. The PHA fibers showed cracks in SEM, a decrease in molecular weight, and changes in the IR spectrum. No evidence of biological influence (bacteria or fungi) was found. Under industrial composting conditions, all fibers showed a decrease in strength and molecular weight. For the BICO and the PHA fibers, the SEM images show significant changes. Especially in the PHA fibers, fungal mycelia can be seen. The studies provide a better insight into the processes involved in the degradation behavior under different environmental conditions. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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17 pages, 7332 KiB

Open AccessArticle

Study of the Sensitivity Limit of Detection of α-Particles by Polymer Film Detectors LR-115 Type 2 Using X-ray Diffraction and UV-Vis Spectroscopic Methods

by Dana S. Yerimbetova, Artem L. Kozlovskiy, Umitali N. Tuichiyev and Kassym S. Zhumadilov

Polymers 2023, 15(11), 2500; https://doi.org/10.3390/polym15112500 - 29 May 2023

Viewed by 930

Abstract

This work is devoted to the applicability assessment of optical spectroscopy and X-ray diffraction methods to establish the lower detection limit for the density of latent tracks from α-particles in polymer nuclear-track detectors, in the case of simulation of the formation of radon [...] Read more.

This work is devoted to the applicability assessment of optical spectroscopy and X-ray diffraction methods to establish the lower detection limit for the density of latent tracks from α-particles in polymer nuclear-track detectors, in the case of simulation of the formation of radon decay daughter products using Am-241 sources. During the studies, the detection limit for the density of latent tracks—traces of the interaction of α-particles with the molecular structure of film detectors—was established using optical UV spectroscopy (10⁴ track/cm²) and X-ray diffraction (10⁴ track/cm²). At the same time, analysis of the connection between structural and optical changes in polymer films indicates that a growth in the density of latent tracks above 10⁶–10⁷ results into the formation of an anisotropic change in the electron density associated with distortions in the molecular structure of the polymer. An analysis of the parameters of diffraction reflections (the position and width of the diffraction maximum) showed that in the range of latent track densities of 10⁴–10⁸ track/cm², the main changes in these values are associated with deformation distortions and stresses caused by ionization processes during the interaction of incident particles with the molecular structure of the polymer. The increase in optical density, in turn, is caused by the accumulation of structurally changed regions (latent tracks) in the polymer as the irradiation density increases. A general analysis of the obtained data showed good agreement between the optical and structural characteristics of the films depending on the irradiation density. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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13 pages, 6886 KiB

Open AccessArticle

Electrical Properties and Lifetime Prediction of an Epoxy Composite Insulation Material after Hygrothermal Aging

by Yan Yang, Jielin Ma, Malvern Yap, Qi Wang, Wen Kwang Chern, Yi Shyh Eddy Foo and Zhong Chen

Polymers 2023, 15(8), 1942; https://doi.org/10.3390/polym15081942 - 19 Apr 2023

Viewed by 1333

Abstract

In this study, we conducted the hygrothermal aging of an epoxy composite insulation material at 95% relative humidity (RH) and temperatures of 95 °C, 85 °C, and 75 °C. We measured electrical properties, including volume resistivity, electrical permittivity, dielectric loss, and breakdown strength. [...] Read more.

In this study, we conducted the hygrothermal aging of an epoxy composite insulation material at 95% relative humidity (RH) and temperatures of 95 °C, 85 °C, and 75 °C. We measured electrical properties, including volume resistivity, electrical permittivity, dielectric loss, and breakdown strength. It was found to be impossible to estimate a lifetime based on the IEC 60216 standard, because it uses breakdown strength as its criterion even though breakdown strength hardly changes in response to hygrothermal aging. In analyzing variations in dielectric loss with aging time, we found that significant increases in dielectric loss correlated well with lifetime prediction based on the mechanical strength of the material, as described in the IEC 60216 standard. Accordingly, we propose an alternative lifetime prediction criterion by which a material is deemed to reach its end of life when its dielectric loss reaches 3 and 6–8 times the unaged value at 50 Hz and low frequencies, respectively. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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23 pages, 7772 KiB

Open AccessArticle

Moisture Content Prediction in Polymer Composites Using Machine Learning Techniques

by Partha Pratim Das, Monjur Morshed Rabby, Vamsee Vadlamudi and Rassel Raihan

Polymers 2022, 14(20), 4403; https://doi.org/10.3390/polym14204403 - 18 Oct 2022

Cited by 7 | Viewed by 2107

Abstract

The principal objective of this study is to employ non-destructive broadband dielectric spectroscopy/impedance spectroscopy and machine learning techniques to estimate the moisture content in FRP composites under hygrothermal aging. Here, classification and regression machine learning models that can accurately predict the current moisture [...] Read more.

The principal objective of this study is to employ non-destructive broadband dielectric spectroscopy/impedance spectroscopy and machine learning techniques to estimate the moisture content in FRP composites under hygrothermal aging. Here, classification and regression machine learning models that can accurately predict the current moisture saturation state are developed using the frequency domain dielectric response of the composite, in conjunction with the time domain hygrothermal aging effect. First, to categorize the composites based on the present state of the absorbed moisture supervised classification learning models (i.e., quadratic discriminant analysis (QDA), support vector machine (SVM), and artificial neural network-based multilayer perceptron (MLP) classifier) have been developed. Later, to accurately estimate the relative moisture absorption from the dielectric data, supervised regression models (i.e., multiple linear regression (MLR), decision tree regression (DTR), and multi-layer perceptron (MLP) regression) have been developed, which can effectively estimate the relative moisture absorption from the dielectric response of the material with an R¬2 value greater than 0.95. The physics behind the hygrothermal aging of the composites has then been interpreted by comparing the model attributes to see which characteristics most strongly influence the predictions. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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21 pages, 4619 KiB

Open AccessArticle

Analysis of Permeation and Diffusion Coefficients to Infer Aging Attributes in Polymers Subjected to Supercritical CO₂ and H₂ Gas at High Pressures

by Hamad Raheem, Bernadette Craster and Ashwin Seshia

Polymers 2022, 14(18), 3741; https://doi.org/10.3390/polym14183741 - 07 Sep 2022

Cited by 4 | Viewed by 2662

Abstract

There is a need to understand the permeation flux behavior of polymers exposed to high-pressure and -temperature fluids continuously for long time intervals. This study investigates evidence of structural alterations in polymer specimens as indicators of material aging through the monitoring of transport [...] Read more.

There is a need to understand the permeation flux behavior of polymers exposed to high-pressure and -temperature fluids continuously for long time intervals. This study investigates evidence of structural alterations in polymer specimens as indicators of material aging through the monitoring of transport coefficients at pressure steps from 10 barg to 400 barg and temperatures ranging between 30 °C and 90 °C. The continuous flow permeation methodology is a well-established technique described in the literature for applications from membrane separation processes to polymeric pressure barriers used for complex fluid containment in the oil and gas industry. In this study, a novel methodology has been used that allows the permeating flux of supercritical CO₂ and H₂ gas through raised-temperature polyethylene and polyvinylidene fluoride films at varying elevated temperatures and pressures to be determined, over timescales of several months using gas chromatography. During these long-term measurements, changes in the test conditions, principally in temperature and stepwise increases in differential gas pressure, were made in order to determine the activation energy for permeation along with the transport coefficients of permeation, diffusion, and sorption. At no time was the polymer film allowed to outgas during the temperature or pressure alterations. The permeation experiments are complemented by differential scanning calorimetry tests to track changes in polymer crystallinity before and after exposure of the specimen to plasticizing gases, which revealed the extent of structural alterations inflicted on the specimen due to high temperature and pressure loads. It is seen that specimens that were exposed to starting high pressures aged more than those that had gradual increases in feed pressure. Furthermore, the relationship between transport coefficients and fractional free volume in the polymer upon exposure to high pressure and temperature conditions is explored. Lastly, the benefit of using fugacity in place of feed pressure for the calculation of the permeability coefficient is discussed. This study contributes to the understanding of the effect of prolonged exposure of the polymeric specimens to CO₂ and H₂ gas under stepwise pressure and temperature loading on their flux behaviors and crystallinity, and to candidate polyethylene-based specimens for oil field deployment. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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10 pages, 2327 KiB

Open AccessArticle

The Variety of the Stress–strain Response of Silicone Foam after Aging

by Zhaoqun Shao, Min Zhu, Tianxi Liang, Fei Wu, Zijian Xu, Yang Yang and Yilong Liu

Polymers 2022, 14(17), 3606; https://doi.org/10.3390/polym14173606 - 01 Sep 2022

Cited by 1 | Viewed by 1660

Abstract

The mechanical properties of silicone foam will degrade when exposed to environmental loads such as temperature and pressure for a long time. In recent years, the variation law of the stress–strain response of silicone foam during the aging process has received more and [...] Read more.

The mechanical properties of silicone foam will degrade when exposed to environmental loads such as temperature and pressure for a long time. In recent years, the variation law of the stress–strain response of silicone foam during the aging process has received more and more attention, but there are few works that quantitatively analyze the variation of the stress–strain response. In this work, we quantitatively analyzed the variation law of the stress–strain response of silicone foam during aging by the constitutive model. Firstly, the accelerated aging test of silicone rubber foam under long-term compressive strain was carried out, and its compression set, stress relaxation and strain stress curves of different aging degrees were obtained. Further, degenerate trajectory equations for the compression set and stress–relaxation were obtained. In addition, the hyper-foam constitutive model was obtained by fitting stress–strain curves, and the changes in the model parameters after aging were studied. The results show that the compressed set and stress–relaxation are exponential functions of time, while different to existing research findings, we found that the stress–strain curves do not change monotonically with increasing time, which first softens, then hardens, and finally softens. Additionally, to better understand the changing trend of the stress–strain response, the correlation between the stress–strain curve and the compression set and stress–relaxation was discussed qualitatively. Finally, in the stage of monotonic change of the stress–strain curve, the exponential function of the model parameters with the increase of aging time was obtained. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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14 pages, 3872 KiB

Open AccessArticle

High-Voltage FDS of Thermally Aged XLPE Cable and Its Correlation with Physicochemical Properties

by Haoyue Wang, Maolun Sun, Kaijie Zhao, Xiaowei Wang, Qilong Xu, Wei Wang and Chengrong Li

Polymers 2022, 14(17), 3519; https://doi.org/10.3390/polym14173519 - 27 Aug 2022

Cited by 10 | Viewed by 1863

Abstract

This paper aims to investigate the influence of thermal aging on a crosslinked polyethylene (XLPE) cable, and the relationships between the macroscopical high-voltage dielectric and the microscopical physicochemical properties are also elucidated. To better simulate thermal aging under working condition, the medium-voltage-level cable [...] Read more.

This paper aims to investigate the influence of thermal aging on a crosslinked polyethylene (XLPE) cable, and the relationships between the macroscopical high-voltage dielectric and the microscopical physicochemical properties are also elucidated. To better simulate thermal aging under working condition, the medium-voltage-level cable is subjected to accelerated inner thermal aging for different aging times. Then, high-voltage frequency domain spectroscopy (FDS) (cable sample) and analyses of microscopic physical and chemical properties (sampling from the cable), including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and elongation at the break (EAB), are conducted at different cable aging stages. The dielectric test results show that after a certain aging time, the high-voltage FDS curves of the cable have layered characteristics, and this phenomenon is more obvious as the aging degree increases. Moreover, the slope and the integral of the high-voltage FDS curves rise with aging time. The mechanism is deduced by the physicochemical results that thermo-oxidative aging results in increasing polar groups and dislocation defects in the crystal region, which leads to the above phenomenon. On the one hand, the appearance of polar groups increases the density of the dipole. On the other hand, the destruction of the crystal region increases the probability and amplitude of dipole reversal. In addition, the breaking of molecular bonds and the increase in the amorphous phase also reduce the rigidity of the XLPE molecular main chain. The above factors lead to obvious delamination and larger dielectric parameters of the thermally aged cable. Finally, according to the experimental results, an on-site diagnosis method of cable insulation thermal aging based on high-voltage FDS is discussed. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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21 pages, 10897 KiB

Open AccessArticle

PA-12-Zirconia-Alumina-Cenospheres 3D Printed Composites: Accelerated Ageing and Role of the Sterilisation Process for Physicochemical Properties

by Damian S. Nakonieczny, Magdalena Antonowicz, Gražyna SimhaMartynkova, Frank Kern, Lenka Pazourková, Karol Erfurt and Michał Hüpsch

Polymers 2022, 14(15), 3152; https://doi.org/10.3390/polym14153152 - 02 Aug 2022

Cited by 4 | Viewed by 1835

Abstract

The aim of this study was to conduct artificial ageing tests on polymer-ceramic composites prepared from polyamide PA-12 polymer matrix for medical applications and three different variants of ceramic fillers: zirconia, alumina and cenospheres. Before ageing, the samples were subjected to ethyl oxide [...] Read more.

The aim of this study was to conduct artificial ageing tests on polymer-ceramic composites prepared from polyamide PA-12 polymer matrix for medical applications and three different variants of ceramic fillers: zirconia, alumina and cenospheres. Before ageing, the samples were subjected to ethyl oxide sterilization. The composite variants were prepared for 3D printing using the fused deposition modeling method. The control group consisted of unsterilized samples. Samples were subjected to artificial ageing in a high-pressure autoclave. Ageing conditions were calculated from the modified Hammerlich Arrhenius kinetic equation. Ageing was carried out in artificial saliva. After ageing the composites were subjected to mechanical (tensile strength, hardness, surface roughness) testing, chemical and structural (MS, FTIR) analysis, electron microscopy observations (SEM/EDS) and absorbability measurements. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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18 pages, 6768 KiB

Open AccessArticle

Study on Hydrolysis Properties and Mechanism of Poly(3-Methacrylamido Propyl Trimethyl Ammonium Chloride) Solution

by Yongji Wang, Xu Jia and Yuejun Zhang

Polymers 2022, 14(14), 2811; https://doi.org/10.3390/polym14142811 - 10 Jul 2022

Cited by 2 | Viewed by 1809

Abstract

Poly(3-methacrylamido propyl trimethyl ammonium chloride) (PMAPTAC) is a typical cationic water-soluble polyelectrolyte, which has been widely used in petroleum, papermaking, daily cosmetics and other fields in the form of an aqueous solution. However, the acid–base and thermal stability of PMAPTAC in aqueous solution [...] Read more.

Poly(3-methacrylamido propyl trimethyl ammonium chloride) (PMAPTAC) is a typical cationic water-soluble polyelectrolyte, which has been widely used in petroleum, papermaking, daily cosmetics and other fields in the form of an aqueous solution. However, the acid–base and thermal stability of PMAPTAC in aqueous solution have not been reported yet, which hinders its further application in high-temperature and acid–base environments. To address these deficiencies, the effects of temperature and pH of PMAPTAC with different intrinsic viscosities on its hydrolysis stability were investigated qualitatively and quantitatively, and the hydrolysis mechanism was studied. Firstly, the qualitative analysis showed that the apparent viscosity of the PMAPTAC solution decreased with hydrolysis time at different temperatures and pH. The higher the temperature and the lower the pH, the greater the viscosity loss of PMAPTAC. The quantitative analysis showed that the hydrolysis rate of the PMAPTAC sample solution increased with the increase in temperature and pH. In addition, the intrinsic viscosity of PMAPTAC samples had little effect on the hydrolytic stability of PMAPTAC. Secondly, by analyzing the viscosity curves at different pH and temperatures by Arrhenius analysis, the Arrhenius equations were found to be 1/τ = 200.34e^((−25.04)/RT), 1/τ = 9127.07e^((−38.90)/RT) and 1/τ = 4683.03e^((−39.89)/RT) for pH 3, pH 7 and pH 11, respectively. Thirdly, the hydrolysis rate of PDMC was the fastest under alkaline conditions. In addition, compared with PDMC, PMAPTAC had better hydrolysis stability under the same conditions. Finally, the mechanism of the hydrolyzed polymer was studied by FTIR and ¹³CNMR, which showed that the carbonyl group of PMAPTAC was hydrolyzed into a carboxyl group, and the small molecule (3-aminopropyl) trimethylammonium chloride was generated, while the ester group of PDMC was hydrolyzed into a carboxyl group, and choline chloride was released. The above results can provide a theoretical basis for the application of PMAPTAC in some high-temperature and acid–base environments. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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14 pages, 18905 KiB

Open AccessArticle

Thermal Degradation Kinetics Analysis of Ethylene-Propylene Copolymer and EP-1-Hexene Terpolymer

by Hassam Mazhar, Farrukh Shehzad, Sung-Gil Hong and Mamdouh A. Al-Harthi

Polymers 2022, 14(3), 634; https://doi.org/10.3390/polym14030634 - 07 Feb 2022

Cited by 6 | Viewed by 2386

Abstract

LLDPE is a less crystalline polymer with vast industrial and domestic applications. It is imperative to understand the synthesis, processing conditions, and thermal degradation mechanism of the co- as well as terpolymers. This paper reports the in-situ synthesis and thermal degradation studies of [...] Read more.

LLDPE is a less crystalline polymer with vast industrial and domestic applications. It is imperative to understand the synthesis, processing conditions, and thermal degradation mechanism of the co- as well as terpolymers. This paper reports the in-situ synthesis and thermal degradation studies of the ethylene-propylene copolymer and ethylene-propylene-1-hexene terpolymer and its nanocomposite with ZnAL LDH sheets. The 1-hexene dosing during the in-situ process influenced the product yield and immensely affected the thermal stability of the resultant polymer. One milliliter 1-hexene in-situ addition increased the product yield by 170 percent, while the temperature at 10 percent weight loss in TGA was dropped by about 60 °C. While only 0.3 weight percent ZnAL LDH addition in the terpolymer improved the thermal stability by 10 °C. A master plot technique and combined kinetics analysis (CKA) were deployed to access the thermal degradation mechanism of the synthesized polymers. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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22 pages, 5743 KiB

Open AccessEditor’s ChoiceReview

Investigation of Polymer Aging Mechanisms Using Molecular Simulations: A Review

by Fan Zhang, Rui Yang and Diannan Lu

Polymers 2023, 15(8), 1928; https://doi.org/10.3390/polym15081928 - 18 Apr 2023

Cited by 11 | Viewed by 3462

Abstract

Aging has a serious impact on the properties of functional polymers. Therefore, it is necessary to study the aging mechanism to prolong the service and storage life of polymer-based devices and materials. Due to the limitations of traditional experimental methods, more and more [...] Read more.

Aging has a serious impact on the properties of functional polymers. Therefore, it is necessary to study the aging mechanism to prolong the service and storage life of polymer-based devices and materials. Due to the limitations of traditional experimental methods, more and more studies have adopted molecular simulations to analyze the intrinsic mechanisms of aging. In this paper, recent advances in molecular simulations of the aging of polymers and their composites are reviewed. The characteristics and applications of commonly used simulation methods in the study of the aging mechanisms (traditional molecular dynamics simulation, quantum mechanics, and reactive molecular dynamics simulation) are outlined. The current simulation research progress of physical aging, aging under mechanical stress, thermal aging, hydrothermal aging, thermo-oxidative aging, electric aging, aging under high-energy particle impact, and radiation aging is introduced in detail. Finally, the current research status of the aging simulations of polymers and their composites is summarized, and the future development trend has been prospected. Full article

(This article belongs to the Special Issue Aging of Polymer Materials)

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