Artificial Weathering Environment Research Articles

A study on the surface responses and degradation mechanisms of epoxy-amine coating subjected to UV accelerated weathering and hygrothermal ageing using ToF-SIMS and FTIR analysis

Epoxy amine coatings were subjected to hygrothermal ageing and accelerated weathering conditions that is comprised of neutral salt spray test and UV accelerated degradation condition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to study the surface responses and spectral variation of epoxy amine coatings subjected to different ageing conditions. As a result, principal component analysis (PCA) of ToF-SIMS positive ion spectra illustrated that principal component 1 (PC1) has collected information on a variation of surface responses caused by accelerated weathering and hygrothermal ageing conditions as compared to fresh epoxy amine coatings. On the other hand, principal component 2 (PC2) has distinguished the different surface responses generated on epoxy amine coatings that were subjected to UV accelerated degradation conditions and those that were not. FTIR analysis has demonstrated the hydrolysis and photooxidation of epoxy amine coatings from the growth of two absorption bands at 1709 cm−1 and 1650 cm−1, indicating the formation of carbonyl-containing groups such as ketones, aldehydes, phenyl formates, imine or tertiary amides. This comprehensive analysis provides significant insights into the degradation mechanisms of epoxy amine coatings subjected to corrosion under insulation (CUI) and/or artificial weathering (AW) environment. Understanding these mechanisms is pivotal for industries reliant on epoxy coatings, such as oil and gas, ensuring enhanced performance and extended lifespan of their products under varying environmental conditions. The findings also contribute to the broader field of materials science by offering methodologies and analytical approaches that can be applied to other polymeric coatings and materials.

Influence of ZnO (Nano)Rods on the Dielectric Properties of DGEBF Epoxy Exposed to Progressive Artificial Weathering for VHF/Early UHF Applications

An as-produced epoxy material reinforced with ZnO (nano)rods for outdoor use was produced for the purpose of enclosing VHF/early UHF transceiving elements. Three different ZnO (nano)rod percentages were dispersed (0.1 wt%, 0.5 wt% and 2 wt%) in epoxy samples and were consequently exposed to an artificial weathering environment for a total period of 2880 h. SEM and XRD characterizations were followed by gravimetric, colorimetric and dielectric measurements that were conducted every 576-h AWE treatment intervals and were complemented by FTIR, UV-Vis, contact angle and gloss measurements. The composite exhibited favourable dielectric behaviour: ZnO presence inflicted minimal impact to the composites’ loss tangent, while dielectric permittivity was reduced for low ZnO content (0.1 wt%/0.5 wt%), especially until the 1152-h interval, while it suffered an increase for 2 wt% samples that was maintained from the beginning until the end of the experiment. Hence, the low-k (4–5.2) constructed material, compared to bare epoxy resin, maintained moderate loss tangent levels (0.55–0.7) in the VHF/early UHF spectrum, throughout the full AWE treatment, and also attained reduced dielectric permittivity, thus exhibiting moderate radio frequency transparency, together with enhanced endurance against environmental fatigue.

Durability of polyurethane membranes in artificial weathering environment

In the present work, the degradation behavior of some polyurethane (PU) membranes exposed to artificial weathering environment for different exposure time was studied. The study was conducted in order to understand the durability and life expectancy of these products. The specimens were investigated before and after exposure to accelerated ageing and characterized using different analysis methods: ATR-FTIR spectroscopy, thermal and mechanical properties. In terms of the material surface properties, contact angle measurements and SEM microscopy were performed. Our experimental results reveal that the decomposition of PU is a complex process and is the results of a multitude of physical and chemical phenomena which involves the combination of several steps such as chain scission, rearrangement of them and crosslinking. These investigations allow us to determine the optimum conditions of sterilization or storage of the final polymeric scaffolds, or to design high performance polymers with improved thermal stability.

Aging behavior and mechanism of bio‐based engineering polyester elastomer nanocomposites

ABSTRACTBio‐based elastomers used in industry have attracted much attention. We prepared bio‐based engineering polyester elastomer (BEE) nanocomposites by mixing bio‐based engineering polyester elastomers with carbon (CB). The CB/BEE nanocomposites were exposed to an artificial weathering environment for different time periods. Both its aging behavior changes and aging mechanism were investigated in this article. The tensile strength retention rates were each above 90% after aging at 100°C and 125°C for 72 h. CB/BEE nanocomposites exhibited good anti‐aging properties. Furthermore, the chemical changes were detected by Fourier transform infrared spectroscopy and differential scanning calorimetry. The crosslink density changes during aging of BEE were determined as well. A plausible aging mechanism of BEE was proposed. It can be concluded that the thermal oxidation process gives priority to further crosslinking in the initial period of aging. As the aging time increases, chain scission becomes the dominant element in the subsequent thermal oxidation process. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40862.

Electrochemical Analysis of the Fluorocarbon Anticorrosion Coating after Accelerated Weathering Environment Aging

Fluorocarbon coating was exposed to artificial weathering environment produced by the xenon lamp/condensation weathering equipment for different time periods. The degradation process was studied by electrochemical impedance spectroscopy (EIS), Fourier Transform Infrared Spectrometry (FTIR) and optical microscope. The results show that the resistance of the coatings decrease ，while the capacitance and soakage become larger with the increase of the aging time. This demonstrates that the early aging of the coating influences its protective properties for the corrosion medium. The reason is the changes of the coating’s surface state and chemical structure accelerate the penetration of medium into the coatings, and therefore accelerate the corrosion of metal occurs under the coating.

Surface degradation of unsaturated polyester resin in Xe artificial weathering environment

Unsaturated polyester (UP) resin samples were exposed to artificial weathering environment produced by a xenon lamp light exposure and weathering equipment for different time intervals. The change of appearance, optical property, chemical structure and surface microstructure before and after exposure in this environment was monitored by spectrophotometer, gloss meter, Specular Reflection Fourier Transform Infrared (SR-FTIR) spectroscopy and three-dimensional digital microscope. The results showed that the surface of UP resin turned darker and yellower in the whole weathering stage. Gloss decreased with increasing aging time due to the increase of surface roughness. SR-FTIR results showed that ester bonds in polymeric chains broke in the aging process. With increasing aging time, small voids can be observed on UP surface and expanded gradually to cracks.

Degradation Characterization of Ethylene-Propylene-Diene Monomer (EPDM) Rubber in Artificial Weathering Environment

Ethylene-propylene-diene monomer containing 5-ethylidene-2-norbornene as diene was exposed to artificial weathering environment produced by a xenon lamp light exposure and weathering equipment for different periods of time. The changes of surface color and mechanical properties were monitored by spectrophotometer, computer-controlled tensile testing and hardness measurements. Crosslink density of ethylene-propylene-diene monomer specimens was measured by the solvent swell method. The results showed that the surface of ethylene-propylene-diene monomer became yellower due to the form of carbonyl group. The degradation process proceeded predominantly via cross-linking. With increase in crosslink density, the tensile strength increased and the elongation at fracture decreased.

Effect of artificial weathering on surface properties of unsaturated polyester (UP) resin

Unsaturated polyester resin samples were exposed to artificial weathering environment for different time intervals. The change of appearance, morphology, chemical structure and contact angle on unsaturated polyester resin surface before and after exposure in this environment was monitored by spectrophotometer, gloss meter, microscope, Specula Reflection Fourier Transform Infrared (SR-FTIR) spectroscopy and optical contact angle measuring device. The results showed that the surface of unsaturated polyester resin turned darker and yellower in the first stage and then remained nearly unchanged during further ageing. Gloss reached maximum when the sample was aged for 12 days and then decreased. With increasing aging time, small cracks appeared and developed on the unsaturated polyester resin surface. Hydroxyl and carbonyl groups produced in aging process increased the wettability of unsaturated polyester resin surface.

Study of UV-aging of thermoplastic polyurethane material

In the present work, the characteristics of thermoplastic polyurethane (TPU) material exposed to artificial weathering environment for different durations were studied. The influence on (i) appearance and morphology, (ii) thermal properties and (iii) mechanical properties evolution of the material were investigated during aging. For this purpose, ultraviolet (UV) chamber was used as accelerated aging technique. Optical and scanning electron microscopy (SEM) observations revealed changes in appearance and morphology of TPU material after UV-exposure. From differential scanning calorimetry (DSC) analysis, it was mainly found that thermal properties, in terms of glass transition temperature ( T g), were affected. Changes in mechanical behaviour were equally discerned using both computer-controlled tensile testing and abrasive wear tester. The mechanical properties in bulk of the studied material displayed tow steps. The elastic modulus and the stress at 200% of strain initially decreased and then increased progressively revealing an increase in crosslink density. The tribological properties, in terms of wear resistance, were affected and this degradation became more important with UV-exposure. Furthermore, our experimental results displayed prominently that there was a competition between chain scission and crosslinking mechanisms.

Aging behavior and mechanism of ethylene–propylene-diene monomer (EPDM) rubber in fluorescent UV/condensation weathering environment

Ethylene–propylene-diene monomer (EPDM) rubber was exposed to an artificial weathering environment produced by fluorescent UV/condensation weathering device for different time periods. The surface chemical changes were detected by X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The plausible aging mechanism of EPDM was proposed. The surface energy was calculated through contact angles of water and formamide measured by optical contact angle measuring device. The thermal stability was evaluated by thermo-gravimetric analysis (TGA).The results showed that oxygenated species such as C–O–C, C O and O–C O groups were formed in fluorescent UV/condensation weathering environment. EPDM aging occurred from EPDM surface and propagated to EPDM inner body. The surface energy of EPDM increased to a maximum at 36 days of aging and then decreased slowly. Fluorescent UV/condensation weathering environment does not affect the thermal stability of EPDM predominantly.

Degradation evaluation of ethylene–propylene–diene monomer (EPDM) rubber in artificial weathering environment by principal component analysis

Artificial weathering tests on ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene were conducted in a xenon lamp light exposure and weathering equipment for different time periods. Principal component analysis (PCA) was used to evaluate the 12 degradation parameters of EPDM including surface properties, crosslink density and mechanical properties. The results showed that the combined evaluating parameter Z of EPDM degradation increased quickly in the first 12 days of exposure and then leveled off. After 45 days, it began to increase rapidly again. Among the 12 degradation parameters, the crosslink density is strongly associated with tensile stress at 300% elongation and tear strength. The surface tension is also well correlated with the color aberration.

UV aging characterization of epoxy varnish coated steel upon exposure to artificial weathering environment

Abstract Epoxy varnish coating was exposed to artificial weathering environment produced by fluorescent UV/condensation weathering equipment for different time periods. The degradation process of epoxy varnish coating was studied by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and adhesion test. The results showed that the electrochemical behavior of aged coating was closely related to the formation and development of blisters on the surface due to coating degradation. The coating resistance, Rp, decreased to a lower value after 28 days of exposure, which indicated significant deterioration of barrier properties. Small blisters were observed on coating surface after 21 days of exposure. With increasing aging time, blisters grow up and subsequently broke. The mechanism of blisters formation and subsequent breakage were suggested. The soluble degradation products penetrate into the coating along with water to form osmotic cells leading to the form of blisters on the coating surface under the alternating wet and UV irradiation condition. The spread of degradation areas caused the growth and development of blisters. With the loss of coating material and embrittlement, cracks appear on the surface and the blisters break, which may result in the significant deterioration of bulk properties of the coatings.

Surface degradation of ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene in artificial weathering environment

Ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene was exposed to an artificial weathering environment produced by a xenon lamp light exposure and weathering equipment for different time periods. The surface chemical changes were detected by Specular Reflection Fourier Transform Infrared (SR-FTIR) spectroscopy, Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The change in surface color, contact angle and morphology was monitored by spectrophotometer, optical contact angle measuring device and Scanning Electron Microscope (SEM). Furthermore, surface energy was calculated through contact angles of water and formamide. The results showed that hydroxyl, carbonyl and ester groups were formed during exposure to this artificial weathering environment. EPDM surface became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The contact angles of water and formamide decreased to a minimum and then increased slowly. The surface degradation is a zero order reaction. In addition, the plausible degradation mechanism was proposed.

Aging of ethylene–propylene–diene monomer (EPDM) in artificial weathering environment

Ethylene–propylene–diene monomer (EPDM) containing ENB as diene was exposed to artificial weathering environment for different periods of time. The changes of appearance, morphology, mechanical properties and chemical structures were monitored by spectrophotometer, glossmeter, microscope, computer-controlled tensile testing, hardness measurements and Fourier Transform Infrared (FTIR) spectroscopy. Crosslink density of EPDM specimens was measured by the solvent swell method. The results showed that the surface of EPDM became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The specular gloss reached a maximum when the sample was exposed for 18 days and then decreased. The aging process proceeded predominantly via crosslinking. The tensile strength increased with increase in crosslink density up to an optimum value and thereafter decreased with further increase in crosslink density. FTIR spectra confirmed the formation of carbonyl groups in an artificial weathering environment.