Effect Of Artificial Weathering Research Articles

Isıl işlem sonrası poliüretan vernik uygulanmış kestane odununda salınımsal sertlik üzerine yapay yaşlandırmanın etkileri

The effects of artificial weathering (576 h) on the pendulum hardness values of Anatolian chestnut (Castanea sativa Mill.) wood applied with polyurethane varnish (PU) after heat treatment at 190℃ for 1.5 h and at 212℃ for 2 h were investigated. The results revealed that heat treatment, weathering period, and interaction were significant. The hardness values of the heat-treated materials were higher than those of the non-heat-treated test samples. The highest hardness value was determined in the un-weathered group of the test samples that were heat-treated at 190°C for 1.5 h while the lowest value was determined in the group that was heat-treated at 190°C for 1.5 h and weathered for 432 h. The highest reduction rates after weathering were obtained on samples that were heat-treated at 190℃ for 1.5 h, followed by heat-treated at 212℃ for 2 h and non-heat-treated. It was observed that the heat treatment application caused different pendulum hardness values in chestnut wood samples covered with polyurethane varnish.

Effects of artificial weathering on the surface properties of coated radiata pine

Radiata pine boards were coated with two different methods A and B both beginning with a hydro primer and finishing with a mat oil but method A using an acrylic high gloss coating and method B three layers of an acrylic sealer in between. The samples were subjected to aging processes for 144 h, 288 h, and 432 h by using UV-A 340 nm lamps. The CIE L*a*b* and CIE L*C*H* coordinates were determined (L*, a*, b*, C*, h o*, ΔE*), gloss (perpendicular (⊥) and parallel (//) to the grain at 20°, 60°, and 85° angles) and surface adhesion strength via the pull-off method were tested before and after weathering. Results have shown that lightness (L*), decreases with weathering for both varnish applications with a higher decrease for the B coating system. Redness increased for both applications with no significant differences. At the same time there was a yellowing of the samples along the weathering period. Parallel and perpendicular gloss decreased for 20º and 60º angles while it increased for 85º angle. The adhesion strength of method A was higher and its decrease with weathering was smaller than for method B. Both varnish applications have proven to confer some protection against wood discoloration, but method A showed the best results and is therefore the best method to be used by radiata pine.

Effects of artificial weathering in NR/SBR elastomer blends

Degradation of polymer blends occurs by the constituent phases undergoing distinct chemical changes that depend on their unique chemical structures. This makes predicting and establishing a structure-property relationship for each phase necessary as well as challenging. In this work, the molecular and physical changes occurring in sulfur-cross-linked natural rubber (NR), styrene−butadiene rubber (SBR), and their 50/50 blend subjected to accelerated weathering are analyzed by 1H nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, atomic-force microscopy (AFM), and dynamic mechanical thermal analysis (DMTA). NMR transverse relaxation time (T2) studies suggest the formation of rigid components due to weathering. FTIR and AFM reveal that this is related to the formation of a stiff surface due to chemical modifications, which shows up as an additional thermal transition in the DMTA curves. Low-field double-quantum (DQ) NMR studies of the cross-link density, by the residual dipolar coupling constant (Dres), of SBR show a continuous increase in its cross-link density over the weathering duration (988 h). In contrast, NR exhibits dominant chain scission reactions resulting in defects, with both materials demonstrating the formation of different chain lengths. During the first 168 h, NR also undergoes modification of sulfur bond lengths, which is also observed in the blend. The blend largely follows an intermediate trend of cross-link densities compared to the two polymers but shows signs of lesser chain modifications than a weighted average of the two polymers. This is confirmed by phase-resolved DQ magic-angle spinning (MAS) NMR experiments whereby the peak-specific Dres of the blend was measured to be less modified than that of the individual vulcanizates, thus proving that the blend is more resistant to weathering than its constituent elastomers.

The effect of artificial weathering on shore D hardness value and surface roughness in lemon wood treated with UV system parquet varnish

Günümüzde farklı ağaç türlerine çeşitli ultraviyole (UV) sistem vernikleri uygulanmaktadır. Limon ağacının ahşabı, salon mobilyası ve kaliteli mobilya yapımında kullanılmasının yanı sıra, torna ve kakma işlerinde de değerlendirilmektedir. Bahsedilen bu alanlarda önemli özelliklere ait olan limon ahşabı üzerinde vernik, boya veya UV sistem vernik çalışmalarının kısıtlı olduğu görülmektedir. Bu çalışmada, endüstriyel uygulamalara uygun olarak 3 ve 5 kat olmak üzere UV sistem parke vernikleri limon (Citrus limon (L.) Burm.) odunu yüzeylerine uygulanmıştır. Daha sonra elde edilen kaplanmış malzemeler hızlandırılmış yaşlandırma cihazında 144, 288 ve 432 saat süreleri boyunca UV ışınlarına maruz bırakılmıştır. Daha sonrasında yüzeyler üzerinde meydana gelen değişikler ile yüzey pürüzlülüğü parametreleri ve shore D sertlik özellikleri araştırılmıştır. Elde edilen sonuçlara göre, yüzey pürüzlülüğü parametreleri için Ra, Rq ve Rz değerlerinin yaşlandırma süresinin artması ile her iki vernik türünde artışların görüldüğü bildirilmiştir. Buna ek olarak, shore D sertlik değerleri her iki tür vernik uygulaması için yaşlandırma süreleri karşısında farklılıklar göstermiştir.

Esterified Lignin from Construction and Demolition Waste (CDW) as a Versatile Additive for Polylactic-Acid (PLA) Composites-The Effect of Artificial Weathering on its Performance.

Demand for sustainable packaging and building materials has increased the need for biobased additives. Biocomposites can often be exposed to different weather conditions and UV irradiation. Thus, additives to prevent the negative impact of weathering are generally added to composites. This study aims to evaluate using esterified lignin as an additive against weathering effects in polylactic‐acid (PLA) composites. Lignin is extracted from construction and demolition waste (CDW) wood using a deep eutectic solvent then esterified and tested as an additive in the fabrication of bio‐based composites. For comparison, lignin from birch is used as a raw material for an additive. Esterification is confirmed by solid‐state NMR analysis. Samples are exposed to artificial weathering for 700 hours and their impact strength and color change properties are measured. The results indicate that esterified lignin from CDW (CDW e‐lignin) as an additive protects the biocomposite from the weathering impact. The sample containing the CDW e‐lignin as an additive suffers only a 4.3% of reduction of impact strength, while the samples that contain commercial additives lose clearly more of their impact strength (from 23.1% to 61.1%). Based on the results CDW e‐lignin is a good additive to prevent weathering. As a conclusion, the esterified lignin from CDW, is a versatile additive for composite production.

Colour stability of wood coatings pigmented with natural indigo from Isatis tinctoria after accelerated weathering

AbstractAn experimental study of artificial weathering of two outdoor coatings pigmented with natural indigo from Isatis tinctoria was carried out. The two coatings, natural indigo‐pigmented boat varnish and outdoor paint, were exposed to cycles of ultraviolet light, water condensation and water spray for 40 days in a QUV test chamber. Synthetic indigo and commercial ultramarine pigment were employed as reference materials. The effects of artificial weathering on the coatings were evaluated with CIELab parameters, as well as visual inspection. Coating and pigment stability during artificial weathering were studied with reflectance spectrometry, hyperspectral imaging technology and Fourier Transform–infrared spectroscopy. According to the results, coatings with indigo proved to be more resistant to visual and spectral changes than unpigmented or commercially pigmented coatings.

The Effect of Artificial Weathering on Surface Properties of Thermally Modified Oriental Beech Wood

The study aimed to determine some surface parameters such as surface roughness and color changes of thermally modified Oriental beech (Fagus orientalis L.) wood samples after 750 hours of artificial weathering. The results of the study showed that artificial weathering led to an increase in surface roughness of Oriental beech wood. Thermal modification interval of 210 °C - 230 °C gave a smoother surface than unmodified samples after artificial weathering. Artificial weathering caused darker, reddish, and yellowish tone of unmodified and thermally modified Oriental beech wood. According to the study fi ndings, surface properties of thermally modified Oriental beech wood were better than those of unmodified Oriental beech.

The effect of artificial weathering and hardening on mechanical properties of HDPE with and without UV stabilizers

Outdoor applications of polymers are increasing rapidly. So, the ability of polymers to withstand environmental degradation became very important for many researchers. The effect of artificial weathering and hardening on the stability of high-density polyethylene (HDPE) with and without stabilizers has been studied. HDPE samples were prepared with UV absorbers (UVA) and hindered amine light stabilizers (HALS) at different concentrations. The results indicated that non-stabilized HDPE was mechanically dead after 300 h of exposure, where it lost almost 98% of its toughness, and the percentage of elongation at break reduced from 1223% to 21%. It was clear that stabilizers sustain the mechanical properties of samples efficiently until 900 h. However, the best performance was observed by samples containing a specific concentration of HALS and UV absorber, which retain most of its properties until 1300 h. The hardening test was performed by heating the samples to 125 °C then suddenly cooled at 0 °C, 25 °C, and 50 °C. The mechanical properties of HDPE were significantly affected by hardening.

Effects of artificial weathering on the color, gloss, adhesion, and pendulum hardness of UV system parquet varnish applied to doussie (Afzelia africana) wood

An important wood species in the furniture and parquet industry today is “doussie” wood. In this study, the effects of artificial weathering on ultraviolet-cured varnish (3 coats and 5 coats) applied to doussie (Afzelia africana) wood were investigated. The samples of the UV system cured varnishes were exposed to aging effects for 252 h and 504 h via an UV-A 340 nm lamp. The coated specimens were exposed to UV-A 340 nm fluorescent lamp in a QUV accelerated weathering tester for 252 h and 504 h. The surface adhesion strength, color (L*, a*, b*, ∆E*, ∆L*, ∆a*, and ∆b*) parameters, pendulum hardness, and glossiness (parallel (//) and perpendicular (⊥) at 20°, 60°, and 85°) of UV varnishes coated samples were quantified before and after weathering. According to the results, while the a* value increased, the adhesion, L*, b*, and glossiness values decreased with aging. As a result, it was concluded that doussie wood can be used in the production of flooring with UV-cured varnish.

Effect of artificial weathering on the some surface properties of uv system parquet varnish applied to persian silk (Albizia julibrissin) wood

Her ağaç türüne ait ahşap malzemeyi doğru ve verimli kullanabilmek için farklı özelliklerini bilmek gerekmektedir. Bu çalışma, UV sistemli parke endüstrisinde gülibrişim (Albizia julibrissin) ahşabının değerlendirme olanaklarını araştırmak amacıyla yapılmıştır. UV sistemli parke vernikleri, endüstriyel uygulamalara göre bir parke fabrikasında 3 ve 5 kat gülibrişim ahşabına uygulanmıştır. Daha sonra elde edilen malzemeler 252 ve 504 saat UVA-340 lambaları kullanılarak hızlandırılmış, UV yaşlandırma işlemlerine tabi tutulmuştur. Yaşlandırma öncesi ve sonralarında renk parametreleri (L*, a* ve b*), parlaklık değerleri, könig sarkaç sertliği ve yüzey yapışma direnci (MPa) testleri yapılmıştır. Yaşlandırma ile bu testlerin değiştiği gözlenmiştir. Sonuç olarak, gülibrişim (Albizia julibrissin) ahşabı parke endüstrisinde kullanılabilir.

Degradation in photovoltaic encapsulation strength of attachment: Results of the first PVQAT TG5 artificial weathering study

AbstractDelamination of the encapsulant in photovoltaic (PV) module technology results in immediate optical loss and may enable subsequent corrosion or mechanical damage. The effects of artificial weathering were not previously known; therefore, an empirical study was performed to survey the factors most affecting adhesion, including the ultraviolet (UV) source (ie, Xe or fluorescent lamp[s]), the optical filters for the lamp, the chamber temperature, and the relative humidity. Natural weathering was also performed at locations, including the following: Golden, Colorado; Miami, Florida; Phoenix, Arizona; QiongHai, China; Riyadh, Saudi Arabia; and Turpan, China. Specimens were constructed using a laminated glass/poly (ethylene‐co‐vinyl acetate)/glass geometry. The compressive shear test (CST) was used to quantify the mechanical strength of attachment, taken as a proxy for adhesion. The fractography of select specimens (including cross‐sectional optical microscopy) was used to verify the failure mode (delamination or decohesion). Additional analysis of the local solar spectrum as well as the specimen temperature was performed to interpret the results of natural weathering. The goals of this study include to identify the most significant stressors, clarify where strong coupling may occur between stressors, and validate accelerated test results relative to natural weathering. The importance of specimen conditioning (for moisture) and hygrometric degradation as well as the effects of UV degradation are identified in this study.

Effects of artificial weathering on the surface properties of ultraviolet varnish applied to lemonwood (Citrus limon (L.) Burm.)

Ultraviolet varnishes are widely used for production processes in the parquet industry. A large number of chemicals are used in this sector, and each one has different characteristics. In this study, the effects of accelerated aging of ultraviolet varnish (3 and 5 coats) when applied to lemonwood (Citrus limon (L.) Burm.) (grown in Mezitli, Mersin, Turkey) were investigated. The ultraviolet varnish coated samples were subjected to aging processes (144 h, 288 h, and 432 h) by using UV-A 340 nm lamps. Color (L*, a*, b*, and ΔE*) parameters, glossiness (perpendicular (⊥) and parallel (//) at 20°, 60°, and 85°), and surface adhesion strength via the pull-off method for ultraviolet varnish coated samples were quantified before and after weathering. According to the results, the varnish type, aging period, and interaction between all studied variables, i.e. L*, a*, b* color parameters, glossiness (perpendicular (⊥) and parallel (//) at 20°, 60°, and 85°), and adhesion strength were found to alter the surface properties. As a result, the lemon tree can be used in the production of an ultraviolet parquet system.

Investigation of Linseed Oil Based Wood Coatings: Effect of Artificial Weathering

The aim of this research is to investigate and to evaluate the changes that occur on the surface of wood specimens, coated with three different coatings and exposed to artificial weathering. The three used coatings contain linseed oil and different types of pigments. Specimens of pine wood (Pinussylvestris L.) were painted with one or two layers of coatings to evaluate the discoloration and changes in lightness. For all the tested coatings, discoloration and loss of lightness were observed for all specimens regardless of the applied coatings. Different rates of color changes were observed for the tested coatings. The presence of pigments in the coatings formulation delays the discoloration of wood; as also the composition of pigments plays a significant role in the process.

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanocrystal films: artificial weathering, humidity absorption, water vapor transmission rate, antimicrobial activity and biocompatibility

Bionanocomposite films of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with different cellulose nanocrystal (CNC) loadings were prepared. Effects of artificial weathering, humidity absorption, water vapor transmission rate (WVTR), antimicrobial activity and biocompatibility were studied. Differential scanning calorimetry (DSC) and time resolved synchrotron X-ray diffraction were used to provide information about the effect of CNC on the crystalline structure of PHBV in the bionanocomposites. The incorporation of CNC accelerated the crystallization rate of PHBV due to a nucleating effect. DSC results showed first a decrease of crystallization and then the occurrence of secondary crystallization after artificial weathering. Scanning electron microscopy images implied well CNC distribution before artificial weathering and formation of blister—like points due to artificial weathering. Hydrophobicity of bionanocomposites was found to be slightly lower than for the PHBV in the humidity absorption tests. Bionanocomposites exhibited smaller WVTR due to restricted PHBV chain mobility. Samples with zinc oxide and silver showed antimicrobial inhibition activities against S. enterica, L. monocytogenes, S. aureus and E. coli. Results of cell viability and nitrite accumulation tests showed that PHBV and its bionanocomposites were biocompatible.

Effect of artificial weathering and temperature cycling on the performance of coating systems used for wooden windows

The effects of ultraviolet light irradiation and water spray and temperature cycling on the color stability of waterborne coating systems on spruce were investigated. The test samples were treated with three coating systems (white and brown pigmented acrylate waterborne coatings systems with different layering) from six producers. The artificial weathering was carried out based on standardized (504 h) and increased weathering parameters (504 h). Thirty cycles of temperature changes were performed. Discoloration suggesting the rate of degradation process and color stability was measured by a spectrophotometer in L*a*b* color space. The results showed greater color stability of white coating systems during both experiments. The producer of acrylate coatings with iodopropynyl butyl carbamate and permethrin as biocides and benzotriazole, silicon dioxide and methylsiloxane as additives was characterized by the best coatings performance. The most sensitive color parameter to describe the surface quality as a result of irradiation and water spray has proven to be a change of lightness. A tendency towards degradation with increasing lightness was observed during weathering. The effect of temperature itself on color change was minimal. Scanning electron microscopy and energy dispersive spectroscopy revealed microscopic changes of coatings caused by artificial weathering.

The effect of artificial weathering on PP coextruded tape and laminate

The aim of this work was to analyse the influence of artificial weathering on polypropylene (PP) self-reinforced composite both as fabric constituent (tape) and as laminate. Particular attention has been focused on the interaction between radiation and material microstructural characteristics, especially for the selective action that the former causes in PP amorphous regions. The evaluation of carbonyl index performed by Fourier Transform Infrared (FT-IR) spectroscopy has highlighted that tapes are more prone to degradation since their drawn structure induces internal stress. Differential scanning calorimetry (DSC) measurements have denoted a shift towards lower temperature of PP melting peak. While crystallinity determination performed by DSC and FT-IR spectroscopy has underlined an increasing trend for laminate over exposure time due to the higher amount of amorphous phase, Raman spectroscopy has revealed that photo-degradation induces a rise of the isomeric defect fraction, limiting chemi-crystallisation both for tapes and laminates.

Dermal absorption of benzo[a]pyrene into human skin from soil: Effect of artificial weathering, concentration, and exposure duration.

In vitro assessments of 14C-benzo[a]pyrene (BaP) absorption through human epidermis were conducted with the sub-63-μm fraction of four test soils containing different amounts of organic and black carbon. Soils were artificially weathered for eight weeks and applied to epidermis at nominal BaP concentrations of 3 and 10 mg/kg for 8 or 24 h. Experiments were also conducted at 24 h with unweathered soils and with BaP deposited onto skin from acetone at a comparable chemical load. For the weathered soils, absorption was independent of the amount of organic or black carbon, the mass in the receptor fluid was proportional to exposure duration but independent of concentration, and the mass recovered in the skin after washing was proportional to concentration and independent of exposure time. Results from the weathered and unweathered soils were similar except for the mass recovered in the washed skin, which was lower for the weathered soil only at the higher concentration. We hypothesize that chemical concentrations exceeded the BaP sorption capacity accessible within the artificial weathering timeframe for all soils tested, and that BaP mass in the washed skin was dominated by particles that were not removed by washing. Fluxes into and through skin from soils were lower by an order of magnitude than from acetone-deposited BaP.

Structure and physical-mechanical properties related to comfort of flexible polyurethane foams for mattress and effects of artificial weathering

The aim of the work was to test three flexible polyurethane foams for mattress for comfort and durability. In particular, they were investigated the effects of foam composition and cell architecture on some physical-mechanical properties of interest for bedding applications and related to foam comfort levels (i.e. surface firmness, hysteresis loss and resistance to bottoming out), and their changes after artificial weathering due to moisture and temperature. The results demonstrated that all the three foams have open cell morphology and similar cell structure, with average cell diameters ranging from 430 to 510 micron and wide cell size distribution. As a consequence, they also show comparable water vapor transport behavior. On the contrary, their mechanical response, in terms of hysteresis loss, surface firmness and resistance to bottoming out, was found strongly dependent on their chemical structure and molecular mobility, as inferred from infrared spectroscopy analysis. During accelerated weathering all the foams undergo oxidations that affected their comfort factors in static conditions, giving a progressive lowering of hysteresis loss, surface firmness and resistance to bottoming out, particularly for the two foams having lower crosslinking level and thus slow recovery rate after compression.

Effect of Artificial Weathering on the Properties of Industrial-Scale Thermally Modified Wood

Thermally modified wood is widely used in cladding, decking, and other construction projects that are meant for outdoor exposure. The purpose of this study was to investigate changes in the color, microstructure, and chemical composition of heat-treated, Larix spp. wood that was exposed to artificial weathering. In this study, accelerated weathering tests (UV and moisture) were conducted over a period of 3000 h. Photodegradation of both heat-treated and untreated wood was evaluated in terms of color, microstructure, and chemical changes that were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Ultra-violet radiation caused the degradation of lignin and extractives of wood, resulting in an immediate color change of the wood. The SEM observation of the heat-treated wood showed deformations and cracks in both treated and untreated samples. Irradiation resulted in a pronounced reduction in the absorption intensity and broadening of the FTIR spectra. It was found that the industrial heat-treatment of wood products resulted in more color stability than untreated wood during the early stages of weathering. Thermal modification was found, however, was ineffective in improving the UV resistance wood over long-term photodegradation conditions.

Nanofibrillated cellulose in wood coatings: Dispersion and stabilization of ZnO as UV absorber

Abstract The effect of nanofibrillated cellulose (NFC) on the dispersion and stabilization of zinc oxide (ZnO) nanoparticles in waterborne wood coatings was examined. Different coating compositions with and without NFC at varying concentrations of unstabilized, powdery or stabilized ZnO were produced. Properties of free coating films prepared via bar coating and wood specimens coated by brush with the coating compositions were evaluated. This included the effects of NFC and ZnO on the coating appearance, film formation, distribution of ZnO in the coatings, tensile properties and UV absorbing properties of free films and the effects of artificial weathering on the coated wood specimens. We showed that NFC significantly improved the distribution of the unstabilized ZnO in the coatings and prevented sedimentation of ZnO. NFC also improved film formation and inhibited crack formation during curing and weathering for more brittle binder materials. NFC had a pronounced matting effect but did not influence the coating colour. Colour stability of coated wood specimens during weathering was affected by the ZnO content, but needs further improvement. The results show that the biopolymer NFC is suitable to stabilize ZnO in coatings for wood, which could be of interest for other applications, as well.