Natural Weathering Tests Research Articles

Site-specific weathering of coatings: II. Comparison of natural weathering and accelerated protocols for Central Europe and Florida

AbstractWeathering protocols, which anticipate exposure behavior of coatings in the temperate climate in Central Europe (ZykStuttgart: ZS) and Florida (new protocol: NP), were applied for accelerated testing of melamine-, silicone resin/acrylate dispersion-, and polyurethane-based coating systems and compared to natural weathering at related sites in Stuttgart (Germany) and near Homestead (Florida/USA), respectively. Color parameters and infrared spectra were measured after defined exposure times and normalized to the irradiation doses. Color changes of an industrial standard with an orange pigment (ORWET) were found to depend for both artificial and natural weathering tests predominantly on irradiation dose. This confirms that the spectral power distribution of the lamp/filter configuration proposed in NP matches sufficiently well to both the sunlight spectra in Florida and Stuttgart. For a melamine-based standard crack coat, crack initiation was found only for NP and the late stage of ZS. For all coating systems studied, characteristic band intensities of infrared spectra and/or color parameters for the two protocols and from natural weathering at the related outdoor sites were shifted along the time axis to merge to master plots. To differentiate between thermally activated, photo-initiated, and hydrolytic degradation, the shift factors were plotted versus inverse annual- or cycle-averaged temperatures including irradiation ratios and averaged humidity ratios. Despite the different reaction mechanism for the acrylic component in the silicone resin/acrylate and the polyurethane coating, a dominance of thermally activated degradation was evident for both. The melamine-based binder showed coupled degradation mechanisms (photo-induced and thermally activated complimented by moisture effects). The use of irradiation doses, cycle-, and annual-averaged temperatures together with cycle- and annual-averaged humidities for data analysis provided simple possibilities for comparison of protocols and weathering sites and a rough differentiation between degradation mechanisms.

Fungal colonisation on wood surfaces weathered at diverse climatic conditions

Natural weathering test at two different European climatic zones were conducted to investigate simultaneously both, the fungal colonisation and weathering process of Scots pine wood (Pinus sylvestris L.). The hypothesis was that the wood performing differently in various climate conditions might affect fungal infestation. The colour changes, wettability, and glossiness were measured as indicators of weathering progress of wood together with an assessment of fungal diversity. Different intensities in weathering, occupancy, and colonisation of fungi on wooden surface were detected. A higher number of fungal species was found on wood exposed to the warm temperate climates compared to subarctic or boreal climates. The dominant fungal species in both locations were from the genera Cladosporium and Aureobasidium.

Influence of electrochemically deposited TiO2 on the anti-weathering properties of heat-treated wood

ABSTRACT Ultraviolet light-induced discoloration is a noticeable issue when heat-treated wood is used outdoors. In this study, titanium dioxide (TiO2) particles were electrochemically deposited on the surface of heat-treated wood via a high-voltage electrostatic field (HVEF). Natural and artificial weathering tests were carried out to evaluate the anti-weathering properties after the electrochemical deposition. During HVEF treatment, Ti particles were triggered in the form of Ti4+. Ti4+ grafted with the hydroxyl groups of hemicellulose and lignin in the form of Ti–OH, and TiO2 was produced due to the oxidizing atmosphere generated by HVEF. TiO2 and Ti–OH played roles as UV absorbers, reducing degradation and discoloration of heat-treated wood. The photodegradation of lignin was alleviated effectively during both the artificial and natural weathering. The stability of wood color was remained. After the artificial weathering, the values of L*, a* and b* of the electrochemical depositied sample were 55, 10 and 25, respectively. The leaching amount of TiO2 after artificial or natural weathering was less than 6% or 40%, respectively determined by atomic absorption spectroscopy. The results suggest the feasibility of the electrochemical deposition of TiO2 for improving the anti-weathering properties of heat-treated wood and provide an effective strategy for industrial wood modification.

Degradation of sunlight exposure on the high-density polyethylene (HDPE) pipes for transportation of natural gases

High-density polyethylene pipes are prevailing in transportation of combustible natural gases, so their reliability deserves special attention. Amongst the diverse ageing effects that are usually taken into account, including internal pressure, chemicals, temperature and vibration etc., the effect of sunlight exposure has been seldom concerned because the natural weathering test takes a really long time. Though the Xenon arc lamp is always used to simulate the ultraviolet environment, the natural weathering test is still the optimum to evaluate the performances degradation of materials to simulate the actual service conditions. In this paper, such a natural weathering test with sunlight exposure time up to 24 months was performed on the PE100 class high-density polyethylene pipes. The mechanical and the chemical properties before and after the test were measured to evaluate the extent and trend of degradation, and particularly the Fourier transform infrared microscope was utilized to quantitatively investigate the oxidation degradation mechanism in the microscopic level.

Fuzzy recognition of LDPE weathering risk based on environmental parameters

The environmental adaptabilities of low-density polyethylene (LDPE) play an important role for high-speed trains’ reliability and comfort. The weathering of LDPE depends on environment factors, while the complexity of the weathering processes inhibits the evaluation of environmental weathering risks. To elucidate the correlation between weathering and environmental factors, and to predict the weathering risk of target areas of interest, three-year-long natural weathering tests were conducted at twelve natural exposure stations in China. Properties of weathered LDPE were compared and analysed using factor analysis. The fuzzy recognition method based on analytic hierarchy process (AHP) was established and used to predict the weathering risk based on environmental database. The results indicate that the factor scores can partitioned the atmospheric environments into five weathering risk grades. This article used the accumulated cumulative temperature of the daily maximum temperature for weathering risk evaluation, which is more scientific than the annual average temperature widely used and is useful for revealing the difference in LDPE weathering in Turpan and Korla. A comparative chart of LDPE’s weathering risk in China was established by this fuzzy recognition method for the first time, which caters to the continuous extension of high-speed railway to new regions.

Effect of Aging on Solar Reflectance of White Cool Roof Coatings: Natural Weathering and the Influence on Building Energy Needs for Different Climate Conditions in Brazil

The use of cool materials on the building envelope is one of the most cost-effective ways to increase indoor thermal comfort conditions in hot climates and decrease the cooling energy needs. Despite the benefit of reducing cooling loads, researches have demonstrated that aging of roof coatings changes the initial solar reflectance (SR), which influences the long term building thermal and energy performance. Thus, this work presents preliminary natural weathering tests performed on samples of nine white coatings exposed to natural weathering for one year in the city of Sao Carlos, Brazil. Solar reflectances were measured with a spectrophotometer before and after exposure, every 3 months, for identifying the effect of aging along the time. The findings showed changes of 13% to 23% on SR after one year of natural weathering, with higher decrease on SR for rougher surfaces. The cleaning process restored from 90% to 100% of the original SR, which means maintenance can be an effective solution to restore the initial SR. Simulations indicated that roofs with higher solar reflectance increase indoor thermal comfort conditions and decrease the cooling energy need for buildings in hot climates, but the aging of white coatings increased the cooling energy needs along the time

ISOLATION OF CELLULOSE DERIVED FROM ORANGE PEEL AND ITS APPLICATION IN BIODEGRADABLE FILMS

"In this study, cellulose was extracted and isolated from orange peel (OP) via alkaline treatment, followed by a bleaching process. The orange peel derived cellulose (OPDC) was characterized and compared with microcrystalline cellulose (MCC). FTIR characterization confirmed the absorption peaks of cellulose for both OPDC and MCC. From the DSC analysis, it was found that MCC possessed higher thermal stability than OPDC. In addition, the results of FESEM and particle size analysis revealed the micro-size dimension of OPDC after the pretreatments. The crystallinity index (CrI) of OPDC (80.14%) was found to be significantly higher than that of untreated OP (23.54%). After that, biodegradable blended films with different weight ratio were prepared using OPDC and MCC with polyvinyl alcohol (PVA) by the solution casting method. According to the FTIR spectra, the shift of the characteristic absorption band and the change of the band intensity observed in the spectra of the PVA/OPDC blended films were similar to those of the PVA/MCC blended films. This confirmed the development of new inter- and intramolecular hydrogen bonds and changes in the conformation between PVA and cellulose. The tensile strength and elongation at break of both PVA/OPDC and PVA/MCC blended films decreased when the cellulose content increased in the PVA matrix. However, the elastic modulus of both films was enhanced when the amount of cellulose increased. By comparison, the PVA/OPDC blended film presented higher tensile strength and elastic modulus than the PVA/MCC blended film. Based on the natural weathering tests, the degradability of blended films increased with a rising amount of cellulose after exposure to degradation tests. The biodegradability of blended films was confirmed by the tiny black spots observed on their surface, which reflected the growth of microorganisms. It was further proven by the morphology studies performed on the surface of the films using FESEM."

DEVELOPMENT OF SPECIALTY COATED FABRICS FOR CANOPY OF INFLATABLE MILITARY TENT (IMT) FOR FOREST AREA

The principal objectives of this present work were to develop novel coated fabrics in olive green (OG) colour to serve as canopy for inflatable military tent (IMT) for forest area. Two varieties of coated fabrics were developed by coating of specific grade aliphatic thermoplastic polyurethane (TPU) on Nylon fabrics and one more with coating of plasticized polyvinyl chloride (PVC) on Polyester fabric. The construction parameters and properties of the substrate basic fabrics used for coating were evaluated and reported. The various functional parameters such as breaking strength and elongation%, tear strength, bursting strength, waterproofness, flame retardancy, flexing, accelerated ageing (-400C and 700C), blocking, ultraviolet (UV) radiation protection and colour fastness to washing and light of the coated fabrics were measured and reported with details, along with an elaborate note on the preparatory process pursued for the development of these coated fabrics. The most suitable coated fabric for canopy of IMT was selected based on the evaluated functional features. Further, the thermal analysis was carried out for the selected coated fabric using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) for assessing its heat resistance. The shelf-life of the selected coated fabric was assessed by evaluating the residual strength (tensile and bursting), measured by subjecting it to accelerated and natural weathering tests. A special device was fabricated to carry out natural weathering test. Statistical analysis was performed at 95% significance level to estimate the actual strength (tensile and bursting) loss upon weathering.

Service-Life Study of Polycarbonate Outdoors Using Python with Incomplete Data

The deterioration of polycarbonate (PC) depends on various environmental factors. Meanwhile, the complexity of the related weathering processes inhibits the prediction of service life based on the environmental factors. To elucidate the nonlinear correlation between PC weathering and the environmental factors, three-year-long natural weathering tests were conducted at eight experimental stations in China. The relationship between tensile-property data of PC and environmental and pollutant data is analyzed by extra-trees and multilayer perceptron networks implemented in Python. The results indicated that (1) the degradation of PC tensile properties is mainly affected by the experimental period (76.37%), whilst the effect of the environmental or pollutant factors on the degradation is less pronounced (23.63%); (2) the classification accuracy of the trained model on the training set is 91% (91/100), and on the testing set is 72.13% (44/61); and lastly, (3) it is inferred from the error analysis of the classification results that the performance change of polycarbonate in Qionghai and Wuhan is characterized by an initial reduction followed by a slight improvement. Lastly, we show that the proposed method performs well, especially in the case of areas with incomplete data available.

Natural weathering’s effect on mechanical properties of short cycle coconut trunk lumber impregnated using kraft black liquor

The weathering resistance properties of short cycle coconut trunk lumber (SC-CTL) were evaluated in response to impregnation using kraft black liquor (BL) and black liquor/phenol formaldehyde (BL/PF) resin. Concentrations of 10, 15, 20, and 25% w/w kraft BL and PF resin with BL were impregnated into SC-CTL using a vacuum-pressure method. Natural weathering tests lasting 6 and 12 months were performed according to ASTM D1435 (1999). After the prescribed testing period, samples were analyzed for their morphological changes via FT-IR and SEM. Mechanical tests were conducted to analyze changes caused by natural weathering in impregnated SC-CTL. The results showed that BL with PF resin impregnation into SC-CTL improved the resistance against natural weathering. The SEM study confirmed that fungi could not colonize the treated samples. The results also suggested that addition of 20% BL in PF resin was sufficient to inhibit weathering. Thus, it was concluded that impregnation of PF resin with BL is a good method to improve the mechanical properties of SC-CTL.

Studies on the durability of wood-cement particleboards produced with residues of Pinus spp., silica fume, and rice husk ash

Wood-cement composites were considered as substitutes for wood or asbestos cement. This research is focused on the development, characterization, and durability of different wood-cement particle boards composed of wood waste [residual particles of pine species (Pinus spp.)], with silica fume or rice husk ash. The wood-cement panels produced by cold compression were evaluated for their physical and mechanical properties after accelerated and natural weathering for 28 and 91 days of curing, respectively. Results indicate that the performance of wood-cement panels containing the Pinus spp. residue was comparable to that of lignocellulosic aggregate in wood cement panels. Pine residue wood panels exhibited high levels of pozzolanic activity, suggesting that silica fume or rice husk ash could be used as a partial substitute in Portland cement. There was a significant loss of mechanical properties over time with both the reference panel and the panel produced with pozzolana. Although there was no direct correlation between the values of accelerated weathering tests and natural weathering tests, there was a larger degradation of the panels after 20 cycles of the accelerated weathering than that after 12 months of natural weathering. Morphology studies supported the observed results.

Comparison of Exterior Coatings Applied to Oak Wood as a Function of Natural and Artificial Weathering Exposure

Artificial weathering can significantly reduce the testing time needed for proving coating durability, nevertheless its reliability is still not thoroughly proven. In this study, eight different transparent and pigmented coating systems, namely oil, acrylate, alkyd and urethane alkyd were evaluated through natural and artificial weathering tests on oak samples by measuring colour, gloss and surface wettability and by macroscopic and microscopic evaluation. The oil coatings performed well in wood colour stability evaluations, while the best gloss and wettability change results were noted for acrylate coatings. Pigmented coatings were characterized by significantly lower colour changes than transparent ones. The gloss and wettability changes were more sensitive to coating disruption than to total colour changes of coated wood associated with chemical changes in wood. The findings in this work showed that values of gloss changes and surface wettability for all types of coatings exposed to artificial and natural weathering resulted in significant differences from each other. The data obtained by artificial weathering method provide basic results of coatings durability and, ideally, natural weathering should be performed at the same time to support the results from laboratory tests by exposing wood under real conditions.

Properties of Gypsum Boards Made of Mixtures of Wood and Rice Straw

Aims: It was investigated to produce gypsum-based experimental composite panels with red pine wood/rice straw particles in the mixture up to 60:40 (ratio) (w/w) in gypsum-water mixture. In this case, the additives could be observed more closely.
 Methodology: The red pine wood chips and the rice straw (stalks) have been turned into suitable particle dimensions. The experimental boards were cut to determine the IB (Internal bond), MOE–MOR (Modulus of Elasticity and Rupture), and TS (thickness swelling after 24 hours immersion in water). A standard flame combustion test system was conducted according to TS EN-ISO 11925-2. For surface chemical analyses, FTIR was used to evaluate the chemical groups present in the board surface. The thermogravimetric analysis (TGA) was conducted for measuring changes in boards as a function of increasing temperature. The natural weathering tests were conducted that were exposed to outdoor for two months then color and surface hardness measurements conducted for determining property changes.
 Results: The rice straw had negative impact on thickness swelling (TS) properties of boards in water. The highest TS value of 47.66% was observed in the board that produced from 60:40 (ratio) (w/w) wood/rice straw mixture (DE4). However, the addition of rice straw to the wood/gypsum mixture has a lowering effect on the internal bond (IB) and bending strength (MOR) properties of experimental boards some level. The maximum IB strength of 0.06 N/mm2 and MOR of 2.77 N/mm2 found control sample (DE0). However, the highest MOE value of 553 N/mm2 was calculated on the DE4 board, which was produced by adding 40% rice straw to the wood/gypsum mixture. The addition of rice straw and wood particles to the gypsum structure has a positive effect on the heat transfer properties.
 Conclusion: It is clear that the addition of rice straw to the wood/gypsum mixture adversely affected the strength properties negatively. However, rice straw in wood chip/gypsum mixture helps to improve heat resistance (insulation) properties of panels at some level. Moreover, the addition of rice straw to wood/gypsum mixture effects on extending hardening time.

Mechanical Behaviour of the Polypropylene-Devulcanized Natural Rubber Compound upon Natural Weathering

This study aims to investigate the mechanical behaviour of the polypropylene/devulcanized natural rubber (PP-DeVulcNR) compound upon natural weathering. The DeVulcNR was used to improve the mechanical properties of the PP-DeVulcNR compound at the range of 0 – 20 phr. These samples were subjected to natural weathering test at a duration range of 0 – 6 months to further study the weatherability of the compound. It was found that with the addition of 5 phr DeVulcNR in PP has the highest weatherability as it has obtained the optimum value of the tensile strength after 6 months outdoor exposure. Besides that, there is more fibrils formation on the fractured surface due to better dispersion of DeVulcNR particles in PP matrix. The Young’s Modulus and elongation at break of the PP-DeVulcNR compounds reduced after 6 months outdoor exposure due to the embrittlement of the materials. The presence of the hydroxyl (O-H) and carbonyl (C = O) stretching vibration indicated that the photo-oxidation occurs in the compound during outdoor exposure.

Effect of Rosemary Antioxidanton on the Stability of Polypropylene in Natural Weathering Tests

Effects of Rosemary Antioxidanton (Rao), extracted from Rosmarinus officinalis, on the antioxidantive properties of polypropylene were evaluated by investigating the difference of mechanical properties and melt flowability between pre and post natural weathering tests. For comparison purposes, the effects of a synthetic phenolic commercial antioxidant (Irganox B215), were also analyzed. The results showed that the reduction of mechanical properties and the increment of melt flowability of polypropylene containing Rao were slower than that of the unstabilized reference during the aging process, which implies that Rao exhibits high efficiency as a thermal antioxidant for polypropylene. On the other hand, samples that contained Irganox B215 obtained further improved stability over the samples containing Rao during 105 days; however, the effectiveness of Rao lasted longer than that of Irganox B215. Rao has the characteristic of being harmless and having high activity, good stability and abundant resources to be a good natural antioxidant.

Изучение защитных свойств ингибированной пленки на основе ингибитора ифхан-112 в условиях влажного тропического климата

Polyethylene film made from the basis of a volatile corrosion inhibitor IFKHAN-112 (3.0% and 4.5% by weight) was exposure to a preliminary assessment of its effectiveness of protection against atmospheric corrosion of St3 steel, M1 copper, Ts0 zinc and D16 aluminum alloy. Natural weathering test was conducted on Natural Weather Testing Station Dam Bay over the period of 12 months. The station is located in humid tropical climatic conditions. It was shown that the contact method provided almost complete protection for St3 steel in the period of 6÷12 months, whereas the vapor-phase method - only 6 months. Both methods provided a high protective level for copper and zinc (M1, Ts0) in the period of 6÷12 months. Inhibiting film IFKHAN-112 did not provide full protection for D16 aluminum alloy against the atmospheric corrosion.

Susceptibility of thermo-hydro-treated birch plywood to mould and blue stain fungi

ABSTRACTIn this study, mould and blue stain susceptibility, capillary water uptake (CWU) and microstructural properties of two thermo-hydro-treated (THT) birch plywood products A and B were investigated. Plywood A represented a THT industrial plywood glued with a phenol formaldehyde (PF) adhesive. Plywood B represented panels from THT veneers glued with a PF film. The THT regimes were (temperature, °C/time, min): 150/10, 150/50, 160/10 and 160/50. Both THT plywood products and untreated samples were resistant to mould and blue stain growth in 1 month of exposure in laboratory and outdoor conditions. A statistically significant correlation between fungal growth in laboratory and outdoor conditions for plywood products A and B was not found (P > .05). Artificial weathering of both plywood products provided adverse fungal growth results compared to the natural weathering test outdoors. The fungal growth on plywood A and B samples mutually strongly correlated (P < .05) only in the outdoor test. Plywood B samples demonstrated a much lower CWU than plywood A, obviously because of microstructural changes, including densification, and type of glue used. Lower CWU of THT plywood in comparison with untreated samples did not provide clear evidence on inhibition of fungal growth.

Investigating plywood behaviour in outdoor conditions

Moisture behaviour of plywood is investigated in combination with detailed structural analysis. In the lab, neutron radiography and X-ray computed tomography (X-ray CT) were used to map the moisture distribution and internal structure of plywood respectively. In an outdoor natural weathering test, the average moisture content (MC) and moisture distribution of plywood were monitored using a continuous moisture measurement set-up and an adapted electrical method, respectively. The structural changes of the specimens during weathering were recorded by using X-ray CT. Based on the interrelationship of moisture behaviour and structure, suggestions are given for improving the water resistance of plywood by optimising structure.

Effect of Dihydromyricetin on the Stability of Polypropylene in Natural Weathering Tests

ABSTRACTEffects of dihydromyricetin (DMY), extracted from Ampelopsis grossedentata, on the antioxidantive properties of polypropylene were evaluated by investigating differences in mechanical properties and melt flowability between pre- and post-natural weathering tests. For comparison purposes, the effects of a synthetic phenolic commercial antioxidant (Irganox 1010) were also analyzed. The results showed that reduction in mechanical properties and increment in melt flowability of polypropylene containing DMY were slower than that of unstabilized reference during the aging process, which implies that DMY exhibits high efficiency as a thermal antioxidant for polypropylene. On the other hand, samples that contained Irganox 1010 obtained further improved stability over the samples containing DMY during 105 days; however, the effectiveness of DMY lasted longer than that of Irganox 1010. DMY has a characteristic of being harmless and having high activity, good stability, and abundant resources to be a good natural antioxidant.

Spectral sensitivity in the photodegradation of fir wood (Abies alba Mill.) surfaces: colour changes in natural weathering

Activation spectra of wood under natural irradiation were investigated in detail in this work. The main purpose was to study colour changes on the wood surface over time and into the depth during natural light exposure and thus to further contribute to the optimization of surface-protecting treatments. In a natural weathering test, three 80-μm-thick strips of fir wood forming the surface layer of a wood composite were exposed to light under a series of glass cut-off filters. Samples were withdrawn at intervals and tested for colour changes. Identification of the most detrimental wavebands of light causing photodegradation was performed based on recorded colour changes. With chronological development of exposure, the colour changes shifted ever deeper into the surface and further into the visible region of the spectrum. A relatively narrow waveband from 360 to 435 nm was identified in the activation spectra to be the most active band, causing the greatest proportion of recorded colour changes. However, also visible light of wavelengths up to 515 nm significantly contributed to colour changes of the surface layers.