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Assessment of the Ageing and Durability of Polymers III

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 50447

Special Issue Editor


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Guest Editor
Innovation Engineering Department, University of Salento, 73100 Lecce, Italy
Interests: cold-cured adhesives and matrices for FRP employed in constructions; polymeric nanostructured adhesives and coatings; hydrophobic coatings for stone conservation and wood protection; durability of polymers, adhesives and coatings; eco-efficient materials for construction and cultural heritage
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Special Issue Information

Dear Colleagues,

Further to the success of the Special Issues of Polymers “Assessment of the Ageing and Durability of Polymers: Procedures and Reliability” and “Assessment of the Ageing and Durability of Polymers II: Procedures and Reliability”, I am delighted to open a new Special Issue entitled “Assessment of the Ageing and Durability of Polymers III”.

Polymers, as any other material, can experience some degradation during their service life, resulting in modifications in their properties. The durability of a polymeric material can be, then, defined as its average lifetime under the in-service conditions; it depends on several parameters, the most important being the type of polymer, the process used to manufacture and to apply it, the usage and load regime and the kind and level of environmental exposure. The durability of polymeric materials and their long‐term performance significantly affect their reliability in common as well as in high tech applications.

Despite the extensive attention devoted to durability of polymers, due to the wide selection of polymeric materials (based on thermoplastics, semi-crystalline and amorphous, cross-linked, thermosettings, elastomers, natural and biodegradable polymers, composites and nano-composites, etc.), to the variety of their applications and utilization and to the variability of exposure regimes, several issues regarding their aging and durability are still open: the most appropriate methods and procedures to foresee their long-term performance; the reliability of standard accelerated aging tests; the identification of ageing mechanisms taking place under complex and coupled mechanical-environmental conditions; the reliability of numerical simulations able to predict their useful life in service.

This Special Issue aims at providing a platform for the discussion of open issues, challenges and achievements when analyzing the chemical ageing and durability features of different polymers/polymeric materials and the possibility of making reliable previsions for their long-term performance.

Prof. Dr. Mariaenrica Frigione
Guest Editor / Section Associate Editor

Keywords

  • aging
  • aging kinetics
  • chemical degradation
  • durability
  • environmental agents
  • exposure regimes
  • hygrothermal aging
  • natural and accelerated procedures
  • long‐term performance
  • numerical simulations
  • service conditions
  • test methods
  • useful life estimation
  • weathering

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Published Papers (14 papers)

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Editorial

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5 pages, 199 KiB  
Editorial
Assessment of the Ageing and Durability of Polymers
by Mariaenrica Frigione
Polymers 2022, 14(10), 1934; https://doi.org/10.3390/polym14101934 - 10 May 2022
Cited by 9 | Viewed by 2019
Abstract
As any other natural or industrial material, polymers can experience some kind of degradation during their service life, resulting in minor to severe changes in their properties [...] Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)

Research

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16 pages, 5295 KiB  
Article
Effect of Aging on the Mechanical Properties of Highly Transparent Fluoropolymers for the Conservation of Archaeological Sites
by Maria Paola Bracciale, Lorena Capasso, Fabrizio Sarasini, Jacopo Tirillò and Maria Laura Santarelli
Polymers 2022, 14(5), 912; https://doi.org/10.3390/polym14050912 - 24 Feb 2022
Cited by 5 | Viewed by 2517
Abstract
In recent years, fluoropolymers have found numerous applications in the architectural field because of their combination of mechanical-chemical resistance and high transparency. In the present work, commercial fluorinated polymers, such as perfluoro alkoxy (PFA) and ethylene tetrafluoroethylene copolymer (ETFE), have been evaluated for [...] Read more.
In recent years, fluoropolymers have found numerous applications in the architectural field because of their combination of mechanical-chemical resistance and high transparency. In the present work, commercial fluorinated polymers, such as perfluoro alkoxy (PFA) and ethylene tetrafluoroethylene copolymer (ETFE), have been evaluated for use as protective and transparent layers on monumental and archaeological sites (to preserve mosaics or frescoes) during the phases of restoration or maintenance outdoors. Considering this specific application, the present study was developed by evaluating the evolution of the mechanical (tensile, tear propagation resistance, and low-velocity impact tests) and chemical (FTIR and DSC analysis) properties of the films after accelerated UV aging. The results that were obtained demonstrated the high resistance capacity of the ETFE, which exhibits considerably higher elastic modulus and critical tear energy values than PFA films (1075.38 MPa and 131.70 N/mm for ETFE; 625.48 MPa and 59.06 N/mm for PFA). After aging, the samples exhibited only a slight reduction of about 5% in the elastic modulus for both polymers and 10% in the critical tear energy values for PFA. Furthermore, the differences in impact resistance after aging were limited for both polymers; however, the ETFE film showed higher peak force than the PFA films (82.95 N and 42.22 N, respectively). The results obtained demonstrated the high resistance capacity of ETFE films, making them the most suitable candidate for the considered application. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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13 pages, 5211 KiB  
Article
High-Density Patterned Array Bonding through Void-Free Divinyl Siloxane Bis-Benzocyclobutene Bonding Process
by Nam Woon Kim, Hyeonjeong Choe, Muhammad Ali Shah, Duck-Gyu Lee and Shin Hur
Polymers 2021, 13(21), 3633; https://doi.org/10.3390/polym13213633 - 21 Oct 2021
Cited by 5 | Viewed by 3166
Abstract
Divinylsiloxane-bis-benzocyclobutene (DVS-BCB) has attracted significant attention as an intermediate bonding material, owing to its excellent properties. However, its applications are limited, due to damage to peripheral devices at high curing temperatures and unoptimized compressive pressure. Therefore, it is necessary to explore the compressive [...] Read more.
Divinylsiloxane-bis-benzocyclobutene (DVS-BCB) has attracted significant attention as an intermediate bonding material, owing to its excellent properties. However, its applications are limited, due to damage to peripheral devices at high curing temperatures and unoptimized compressive pressure. Therefore, it is necessary to explore the compressive pressure condition for DVS-BCB bonding. This study demonstrates an optimization process for void-free DVS-BCB bonding. The process for obtaining void-free DVS-BCB bonding is a vacuum condition of 0.03 Torr, compressive pressure of 0.6 N/mm2, and curing temperature of 250 °C for 1 h. Herein, we define two factors affecting the DVS-BCB bonding quality through the DVS-BCB bonding mechanism. For strong DVS-BCB bonding, void-free and high-density chemical bonds are required. Therefore, we observed the DVS-BCB bonding under various compressive pressure conditions at a relatively low temperature (250 °C). The presence of voids and high-density crosslinking density was examined through near-infrared confocal laser microscopy and Fourier-transform infrared microscopy. We also evaluated the adhesion of the DVS-BCB bonding, using a universal testing machine. The results suggest that the good adhesion with no voids and high crosslinking density was obtained at the compressive pressure condition of 0.6 N/mm2. We believe that the proposed process will be of great significance for applications in semiconductor and device packaging technologies. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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22 pages, 3412 KiB  
Article
An Effective Package of Antioxidants for Avoiding Premature Failure in Polypropylene Random Copolymer Plastic Pipes under Hydrostatic Pressure and High Temperature
by Enrique Blázquez-Blázquez, Joaquín Lahoz, Ernesto Pérez and María L. Cerrada
Polymers 2021, 13(16), 2825; https://doi.org/10.3390/polym13162825 - 22 Aug 2021
Cited by 6 | Viewed by 3910
Abstract
Pipes of polypropylene random (PP-R) copolymers are the best choice for hot- and cold-water networks. Validation of a severe test, accomplishing the ISO 1167 standard, is mandatory to assess their service lifetime expectancy. This work evaluates the behavior shown by three commercial pipes, [...] Read more.
Pipes of polypropylene random (PP-R) copolymers are the best choice for hot- and cold-water networks. Validation of a severe test, accomplishing the ISO 1167 standard, is mandatory to assess their service lifetime expectancy. This work evaluates the behavior shown by three commercial pipes, either the original ones (new pipes) or after being subjected to a hydrostatic pressure test at elevated temperature (aged pipes). Several features with relevance for the final performance have been examined: crystalline characteristics, phase transitions in crystalline regions, effect of high temperature and pressure on these transitions, and oxidation induction time. Moreover, the presence of inorganic fillers, and the content of different antioxidants together with their depletion, have also been analyzed. Films from the new pipes were also prepared for replication of the different environments in order to achieve a better and complete understanding of the phase transitions in the crystalline regions and of the consumption of antioxidants. Distinct environments surrounded the inner and outer parts of the pipes exposed to the failure aging test at 110 °C: hot water and warm dry air, respectively. These features play a key role in the loss of additives and in the subsequent initiation of degradation. Even if the crystalline characteristics are appropriate in the polymeric matrix, the success of a pipe lies in the homogeneous dispersion of components for avoiding damage at interfacial properties, and in a correct package of antioxidants used in its formulation. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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12 pages, 631 KiB  
Article
New Aspects of Degradation in Silicone Rubber under UVA and UVB Irradiation: A Gas Chromatography–Mass Spectrometry Study
by Zheng Wang, Libing Qian, Xiangyang Peng, Zhen Huang, Yue Yang, Chunqing He and Pengfei Fang
Polymers 2021, 13(13), 2215; https://doi.org/10.3390/polym13132215 - 5 Jul 2021
Cited by 9 | Viewed by 3815
Abstract
In this paper, gas chromatography–mass spectrometry (GC–MS) and positron annihilation lifetime spectroscopy (PALS) were used to probe the changes of oligomers and the polydimethylsiloxane (PDMS) network in silicone rubber, after different durations of UVA/UVB irradiation. At the early stage (<300 h) of UVA/UVB [...] Read more.
In this paper, gas chromatography–mass spectrometry (GC–MS) and positron annihilation lifetime spectroscopy (PALS) were used to probe the changes of oligomers and the polydimethylsiloxane (PDMS) network in silicone rubber, after different durations of UVA/UVB irradiation. At the early stage (<300 h) of UVA/UVB irradiation, the concentration of D4-D9 decreases. The o-Ps intensity of the extracted silicone rubber increases in the stage after UVB irradiation. These results indicate the crosslinking of oligomers into the PDMS network. After a long duration (>300 h) of UVB irradiation, D4 was generated and the lifetime of τ3 also increased, indicating the rupture of the Si-O bond in the PDMS network. These two aging processes were termed the post curing process and the chain session process. The new finding was that UVA could only induce the post curing process; UVB causes the rupture of the chemical bond in silicone rubber. Photons of UVB could break the C-H bond, and then trigger the backbiting decomposition of PDMS, breaking the Si-O bond, while the photons of UVA cannot. The fact that D4 was generated after UVB irradiation can be used to evaluate the UVB stability of silicone rubber in the future. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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21 pages, 5303 KiB  
Article
Influence of Gamma Irradiation on Electric Cables Models: Study of Additive Effects by Mid-Infrared Spectroscopy
by Astrid Maléchaux, Juliette Colombani, Sandrine Amat, Sylvain R. A. Marque and Nathalie Dupuy
Polymers 2021, 13(9), 1451; https://doi.org/10.3390/polym13091451 - 30 Apr 2021
Cited by 10 | Viewed by 3223
Abstract
Cables, especially their insulation and jacket materials made of polymers, are vulnerable to ageing degradation during normal operation. However, they must remain functional for the entire life of a nuclear power plant, or even in the event of an accident for cables with [...] Read more.
Cables, especially their insulation and jacket materials made of polymers, are vulnerable to ageing degradation during normal operation. However, they must remain functional for the entire life of a nuclear power plant, or even in the event of an accident for cables with a safety requirement. This study focuses on models of crosslinked polyethylene (XLPE)-based insulation of cables and deals with the structure modification and the behavior of XLPE for nuclear applications due to the effect of additives. Various additives are added to the polymer formulation to evaluate their impact on ageing. The samples are irradiated at room temperature by several gamma doses, up to 374 kGy, with two dose rates (40 Gy/h and 300 Gy/h) and compared with a non-irradiated sample used as reference. To understand the impact of gamma irradiation on the materials, the principal component analysis (PCA) method is applied on spectra recorded through attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy. The results highlight the effects of ageing depending on the dose rate and on the formulation of the materials, with the identification of different degradation products. A curve resolution study compares the effects of different additives on polymer oxidation and shows that the low dose rate leads to a higher degradation than the high dose rate. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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18 pages, 5706 KiB  
Article
Reliability Prediction of Acrylonitrile O-Ring for Nuclear Power Applications Based on Shore Hardness Measurements
by Alvaro Rodríguez-Prieto, Ernesto Primera, Mariaenrica Frigione and Ana María Camacho
Polymers 2021, 13(6), 943; https://doi.org/10.3390/polym13060943 - 19 Mar 2021
Cited by 7 | Viewed by 2824
Abstract
The degradation of polymeric components is of considerable interest to the nuclear industry and its regulatory bodies. The objective of this work was the development of a methodology to determine the useful life—based on the storage temperature—of acrylonitrile O-rings used as mechanical sealing [...] Read more.
The degradation of polymeric components is of considerable interest to the nuclear industry and its regulatory bodies. The objective of this work was the development of a methodology to determine the useful life—based on the storage temperature—of acrylonitrile O-rings used as mechanical sealing elements to prevent leakages in nuclear equipment. To this aim, a reliability-based approach that allows prediction of the use-suitability of different storage scenarios (that involve different storage times and temperatures) considering the further required in-service performance, is presented. Thus, experimental measurements of Shore A hardness have been correlated with storage variables (temperature and storage time). The storage (and its associated hardening) was proved to have a direct effect on in-service durability, reducing this by up to 60.40%. Based on this model, the in-service performance was predicted; after the first three years of operation the increase in probability of failure (POF) was practically insignificant. Nevertheless, from this point on, and especially, from 5 years of operation, the POF increased from 10% to 20% at approximately 6 years (for new and stored). From the study, it was verified that for any of the analysis scenarios, the limit established criterion was above that of the storage time premise considered in usual nuclear industry practices. The novelty of this work is that from a non-destructive test, like a Shore A hardness measurement, the useful life and reliability of O-rings can be estimated and be, accordingly, a decision tool that allows for improvement in the management of maintenance of safety-related equipment. Finally, it was proved that the storage strategies of our nuclear power plants are successful, perfectly meeting the expectations of suitability and functionality of the components when they are installed after storage. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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13 pages, 6339 KiB  
Article
Mathematical Modeling of Outdoor Natural Weathering of Polycarbonate: Regional Characteristics of Degradation Behaviors
by Takato Ishida and Ryoma Kitagaki
Polymers 2021, 13(5), 820; https://doi.org/10.3390/polym13050820 - 7 Mar 2021
Cited by 6 | Viewed by 2974
Abstract
Many natural exposure sites have been developed to ensure the reliability of materials intended for outdoor use. However, the effects of local climate on aging have not been completely understood. This study aimed to elucidate the regional characteristics of natural aging. Non-stabilized and [...] Read more.
Many natural exposure sites have been developed to ensure the reliability of materials intended for outdoor use. However, the effects of local climate on aging have not been completely understood. This study aimed to elucidate the regional characteristics of natural aging. Non-stabilized and stabilized polycarbonates were monitored in terms of their appearance (yellowing and loss of gloss) during natural weathering at five exposure sites (Tokyo, Kagoshima, Okinawa, Florida, and Arizona) in conjunction with climate fluctuation for up to 24 months. Three approaches were employed to characterize the natural aging behaviors: (i) modeling the rate function of degradation, (ii) evaluating the contribution ratio of individual degradational factors, and (iii) estimating the “synchronicity” by cross-correlation analysis with the climate dataset. The aging rates were the highest in Arizona and lowest in Kagoshima among the five exposure sites. First, prediction curves were constructed from the degradation rate function (variables: UV irradiation, temperature, and humidity), and these curves were found to agree well with the measured aging behaviors. Second, the exposure data in Arizona demonstrated strong temperature dependence, while those in Okinawa and Florida had stronger dependence on UV irradiation compared to other sites. Lastly, the synchronicity between UV irradiation and temperature was the highest in Arizona and lowest in Kagoshima, which can explain the significantly faster deterioration in Arizona and the slow deterioration in Kagoshima. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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16 pages, 10435 KiB  
Article
Synthesis of Carvedilol–Organotin Complexes and Their Effects on Reducing Photodegradation of Poly(Vinyl Chloride)
by Omar G. Mousa, Gamal A. El‐Hiti, Mohammed A. Baashen, Muna Bufaroosha, Ahmed Ahmed, Ahmed A. Ahmed, Dina S. Ahmed and Emad Yousif
Polymers 2021, 13(4), 500; https://doi.org/10.3390/polym13040500 - 6 Feb 2021
Cited by 19 | Viewed by 3245
Abstract
Poly(vinyl chloride) (PVC) undergoes photodegradation induced by ultraviolet (UV) irradiation; therefore, for outdoor applications, its photostability should be enhanced through the use of additives. Several carvedilol tin complexes were synthesized, characterized and mixed with PVC to produce thin films. These films were irradiated [...] Read more.
Poly(vinyl chloride) (PVC) undergoes photodegradation induced by ultraviolet (UV) irradiation; therefore, for outdoor applications, its photostability should be enhanced through the use of additives. Several carvedilol tin complexes were synthesized, characterized and mixed with PVC to produce thin films. These films were irradiated at 25 °C with a UV light (λ = 313 nm) for up to 300 h. The reduction in weight and changes in chemical structure and surface morphology of the PVC films were monitored. The films containing synthesized complexes showed less undesirable changes than the pure PVC film. Organotin with a high content of aromatics was particularly efficient in inhibiting photodegradation of PVC. The carvedilol tin complexes both absorbed UV light and scavenged radicals, hydrochloride, and peroxides and, therefore, photostabilized PVC. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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20 pages, 15978 KiB  
Article
The Impact of the Acidic Environment on the Mechanical Properties of Epoxy Compounds in Different Conditions
by Anna Rudawska
Polymers 2020, 12(12), 2957; https://doi.org/10.3390/polym12122957 - 10 Dec 2020
Cited by 15 | Viewed by 2438
Abstract
The aim of this work was to determine the impact of the acidic environment on the mechanical properties of two epoxy compounds in different conditions. The samples were made from the epoxy compounds composed of the epoxy resin (based on Bisphenol A), triethylenetetramine [...] Read more.
The aim of this work was to determine the impact of the acidic environment on the mechanical properties of two epoxy compounds in different conditions. The samples were made from the epoxy compounds composed of the epoxy resin (based on Bisphenol A), triethylenetetramine curing agent (unmodified compound), and calcium carbonate (CaCO3) (modified compound). The epoxy compound samples were seasoned for the following period of time (i.e., one week, one month, and three months). The environment was tap water and the acidic environment had three different concentrations of acetic acid (3%, 6%, and 9%). Strength tests of the epoxy compound samples were carried out in accordance with the ISO 604 standard. In the case of the modified composition, it is noted that the samples immersed in tap water were characterized by a higher strength than in acidic environments. A similar tendency was observed for unmodified compositions, although the differences were smaller than for the modified compositions. It was also noticed that the increase in the pH of the acidic solution in many analyzed cases contributed to the decrease in mechanical properties, although the immersion time in the acidic solution is important. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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16 pages, 4732 KiB  
Article
Tin Complexes Containing an Atenolol Moiety as Photostabilizers for Poly(Vinyl Chloride)
by Baneen Salam, Gamal A. El-Hiti, Muna Bufaroosha, Dina S. Ahmed, Ahmed Ahmed, Mohammad Hayal Alotaibi and Emad Yousif
Polymers 2020, 12(12), 2923; https://doi.org/10.3390/polym12122923 - 6 Dec 2020
Cited by 12 | Viewed by 2863
Abstract
The lifetime of poly(vinyl chloride) (PVC) can be increased through the addition of additives to provide protection against irradiation. Therefore, several new tin complexes containing atenolol moieties were synthesized and their photostabilizing effect on PVC was investigated. Reacting atenolol with a number of [...] Read more.
The lifetime of poly(vinyl chloride) (PVC) can be increased through the addition of additives to provide protection against irradiation. Therefore, several new tin complexes containing atenolol moieties were synthesized and their photostabilizing effect on PVC was investigated. Reacting atenolol with a number of tin reagents in boiling methanol provided high yields of tin complexes. PVC was then mixed with the tin complexes at a low concentration, producing polymeric thins films. The films were irradiated with ultraviolet light and the resulting damage was assessed using different analytical and surface morphology techniques. Infrared spectroscopy and weight loss determination indicated that the films incorporating tin complexes incurred less damage and less surface changes compared to the blank film. In particular, the triphenyltin complex was very effective in enhancing the photostability of PVC, and this is due to its high aromaticity (three phenyl rings) compared to other complexes. Such an additive acts as a hydrogen chloride scavenger, radical absorber, and hydroperoxide decomposer. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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19 pages, 7474 KiB  
Article
Moving toward Smart Cities: Evaluation of the Self-Cleaning Properties of Si-Based Consolidants Containing Nanocrystalline TiO2 Activated by Either UV-A or UV-B Radiation
by José Santiago Pozo-Antonio, Daniel Noya-Pintos and Patricia Sanmartín
Polymers 2020, 12(11), 2577; https://doi.org/10.3390/polym12112577 - 2 Nov 2020
Cited by 4 | Viewed by 2126
Abstract
This study evaluated the self-cleaning ability and durability of Si-based consolidants (an ethyl silicate consolidant and a consolidant based on nanosized silica) spiked with nanocrystalline TiO2 activated by either UV-A radiation (spectral region between 340 and 400 nm, and main peak at [...] Read more.
This study evaluated the self-cleaning ability and durability of Si-based consolidants (an ethyl silicate consolidant and a consolidant based on nanosized silica) spiked with nanocrystalline TiO2 activated by either UV-A radiation (spectral region between 340 and 400 nm, and main peak at 365 nm) or UV-B radiation (spectral region between 270 and 420 nm, and main peak at 310 nm). Granite samples were coated with consolidant, to which nanocrystalline TiO2 was added at different concentrations (0.5, 1, and 3%, by wt.). Diesel soot was then applied to the coated surfaces, and the samples were exposed to UV-A or UV-B radiation for 1650 h. The surface color changes, relative to the color of untreated granite, were determined every 330 h by color spectrophotometry. Slight color changes indicated a recovery of the reference color due to the degradation of the soot. The final surfaces of both the untreated and treated surfaces were compared by stereomicroscopy and scanning electron microscopy. The main findings were that: (1) In general, the consolidant containing nanosized silica induced the most intense photocatalytic activity. In the more compact xerogel coating formed by the nanosized silica, more TiO2 nanoparticles were available to interact with the radiation. (2) For all consolidant mixtures, soot degradation remained constant or decreased over time, except with ethyl silicate with 0.5 wt % TiO2 (no self-cleaning capacity). (3) Soot degradation increased with the concentration of TiO2. (4) The UV-B radiation was the most effective in terms of soot degradation, except for the surface coated with the ethyl silicate and 3% wt. TiO2. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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Review

Jump to: Editorial, Research

18 pages, 1579 KiB  
Review
Can Accelerated Aging Procedures Predict the Long Term Behavior of Polymers Exposed to Different Environments?
by Mariaenrica Frigione and Alvaro Rodríguez-Prieto
Polymers 2021, 13(16), 2688; https://doi.org/10.3390/polym13162688 - 12 Aug 2021
Cited by 52 | Viewed by 7521
Abstract
During their useful life, polymers are subject to degradation processes due to exposure to specific environmental conditions over long times. These processes generally lead to changes, almost always irreversible, of properties and performances of polymers, changes which would be useful to be able [...] Read more.
During their useful life, polymers are subject to degradation processes due to exposure to specific environmental conditions over long times. These processes generally lead to changes, almost always irreversible, of properties and performances of polymers, changes which would be useful to be able to predict in advance. To meet this need, numerous investigations have been focused on the possibility to predict the long-term performance of polymers, if exposed to specific environments, by the so called “accelerated aging” tests. In such procedures, the long-term behavior of polymeric materials is typically predicted by subjecting them to cycles of radiations, temperatures, vapor condensation, and other external agents, at levels well above those found in true conditions in order to accelerate the degradation of polymers: this can produce effects that substantially deviate from those observable under natural exposure. Even following the standard codes, different environmental parameters are often used in the diverse studies, making it difficult to compare different investigations. The correlation of results from accelerated procedures with data collected after natural exposure is still a debated matter. Furthermore, since the environmental conditions are a function of the season and the geographical position, and are also characteristic of the type of exposure area, the environmental parameters to be used in accelerated aging tests should also consider these variables. These and other issues concerning accelerated aging tests applied to polymers are analyzed in the present work. However, bearing in mind the limitations of these practices, they can find useful applications for rating the durability of polymeric materials. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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24 pages, 6563 KiB  
Review
Durability of Externally Bonded Fiber-Reinforced Polymer Composites in Concrete Structures: A Critical Review
by Jovan Tatar and Sandra Milev
Polymers 2021, 13(5), 765; https://doi.org/10.3390/polym13050765 - 28 Feb 2021
Cited by 42 | Viewed by 6321
Abstract
Externally bonded fiber-reinforced polymer composites have been in use in civil infrastructure for decades, but their long-term performance is still difficult to predict due to many knowledge gaps in the understanding of degradation mechanisms. This paper summarizes critical durability issues associated with the [...] Read more.
Externally bonded fiber-reinforced polymer composites have been in use in civil infrastructure for decades, but their long-term performance is still difficult to predict due to many knowledge gaps in the understanding of degradation mechanisms. This paper summarizes critical durability issues associated with the application of fiber-reinforced polymer (FRP) composites for rehabilitation of concrete structures. A variety of factors that affect the longevity of FRP composites are discussed: installation, quality control, material selection, and environmental conditions. Critical review of design approaches currently used in various international design guidelines is presented to identify potential opportunities for refinement of design guidance with respect to durability. Interdisciplinary approaches that combine materials science and structural engineering are recognized as having potential to develop composites with improved durability. Full article
(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers III)
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