Accelerated UV Weathering Research Articles

Bamboo durability: Understanding the combined effect of weathering and mildew infection

Bamboo has been widely used in outdoor applications and heat treatment is a typical industrial technique for improving its durability. Weathering and mildew are the two main types of deterioration that occur on bamboo. However, there are few studies on the deterioration of bamboo properties and degradation mechanism under such combined effect. Therefore, in this study, the effect of weathering on the mildew infection value (MIV) of natural bamboo (NB) and heat-treated bamboo (HB) were compared. The changes in surface color, morphology, and chemical composition of NB and HB during accelerated UV weathering were characterized. Meanwhile, the MIV of bamboo samples after different weathering durations was evaluated and the influencing mechanism was explored. The results revealed that the decomposition of starch and hemicellulose during heat treatment resulted in the generation of levoglucosan and acids, thereby providing a new nutrient source and a more suitable environment for mildew growth. HB exhibited superior color stability and anti-weathering characteristics compared to NB. Moreover, certain photodegradation products from HB demonstrated anti-fungal and anti-weathering properties, which resulted in a temporary resistance to mildew in weathered samples. However, after long-term exposure, the cracks on the surface of HB caused by weathering facilitated the colonization of mildew hypha by releasing inner nutrients, leading to severer mildew infection.

Transparent bamboo as a replacement for glass: Effects of lignin decolorisation methods on weatherability

Transparent bamboo proved to be a promising substitute for glass due to its high light transmittance and excellent mechanical properties. Nevertheless, it was susceptible to outdoor weathering, which negatively affected its physical and mechanical properties. In this study, two decolorisation methods, namely the delignification method and the lignin modification method, were used to produce transparent bamboos with epoxy resin, referred to as DL-TB and LM-TB, respectively. The changes in surface color, optical and mechanical properties, wettability, thermal stability, and thermal insulation properties of transparent bamboo during accelerated UV weathering were evaluated. Additionally, the deterioration mechanism of DL-TB and LM-TB was investigated. The findings revealed that DL-TB demonstrated better transparency and mechanical properties than LM-TB, although it exhibited lower thermal insulation properties. Furthermore, DL-TB demonstrated enhanced color stability and higher hydrophobicity on weathered surfaces than LM-TB. Unexpectedly, the tensile properties of both two transparent bamboos significantly improved after weathering, especially for LM-TB, which was due to the EP post-curing and the formation of more hydrogen bonds between lignin and EP. These observations revealed that lignin played a key role in the photodegradation process of transparent bamboo, but further attempts should be made in future studies to improve its color stability.

Flame-Retarded and Heat-Resistant PP Compounds for Halogen-Free Low-Smoke Cable Protection Pipes (HFLS Conduits).

Conduits are plastic tubes extensively used to safeguard electrical cables, traditionally made from PVC. Recent safety guidelines seek alternatives due to PVC's emission of thick smoke and toxic gases upon fire incidents. Polypropylene (PP) is emerging as a viable alternative but requires modification with suitable halogen-free additives to attain flame retardancy (FR) while maintaining high mechanical strength and weathering resistance, especially for outdoor applications. The objective of this study was to develop two FR systems for PP: one comprising a cyclic phosphonate ester and a monomeric N-alkoxy hindered amine adjuvant achieving V0, and another with hypophosphite and bromine moieties, along with a NOR-HAS adjuvant achieving V2. FR performance along with mechanical properties, physicochemical characterization, and dielectric behavior were evaluated prior to and after 2000 h of UV weathering or heat ageing. The developed FR systems set the basis for the production of industrial-scale masterbatches, from which further optimization to minimize FR content was performed via melt mixing with PP towards industrialization of a low-cost FR formulation. Accordingly, two types of corrugated conduits (ø20 mm) were manufactured. Their performance in terms of flame propagation, impact resistance, smoke density, and accelerated UV weathering stability classified them as Halogen Free Low Smoke (HFLS) conduits; meanwhile, they meet EU conduit standards without significantly impacting conduit properties or industrial processing efficiency.

Coupled effect of UV ageing and temperature on the diffusive transport of aqueous, vapour and gaseous phase organic contaminants through HDPE geomembrane

High-density polyethylene geomembranes (HDPE GMBs) are indispensable in constructing composite barriers of modern engineered landfills. GBMs would be exposed to various weathering conditions apart from the interaction of organic pollutants in landfill gas and leachate. Though many studies have investigated the contaminant's migration, the transport of volatile organic compounds (VOCs) concerning the synergistic effect of thermal and UV exposure has not been thoroughly explored. Given this, the present study investigated the diffusive transport of four VOCs (aqueous and vapour phase) at 10 °C, 25 °C, 40 °C, and methane diffusion through an HDPE GMB subjected to accelerated UV weathering. The results indicated that the contaminant phase (aqueous, vapour, gaseous), its properties (aqueous solubility, molar mass, polarity), temperature, and the extent of ageing significantly influenced the transport behaviour. The standard oxidative induction time decreased appreciably with ageing duration following a first-order exponential decay. The change in tensile properties and melt flow index indicated the dominance of UV degradation by cross-linking, resulting in an increased crystallinity of GMB that was identified using Fourier transforms infrared (FTIR) spectroscopy and Differential scanning calorimeter (DSC). The crystallinity increased with UV ageing and caused the sorption and diffusion coefficients to decrease.

Effects of heat treatment temperatures on the photostability of Moso bamboo during accelerated UV weathering

ABSTRACT Moso bamboo were heat-treated under saturated steam atmosphere at three different temperatures separately: 120°C (low temperature heat treatment, LH group), 160°C (medium temperature heat treatment, MH group), and 195°C (high temperature heat treatment, HH group). Then, the heat-treated bamboo slivers were placed in an accelerated UV weathering tester for a total of 960 h. The samples without any treatments (C group) were also prepared for comparison. After heat treatment, bamboo showed a darker surface color and increased lignin content, especially for those treated at higher temperatures. Compared to the C group, heat-treated samples exhibited less changes in surface color, gloss, morphology, and surface chemical groups after photodegradation, suggesting improved durability after heat treatment. Among them, the HH group exhibited the best photostability during the whole weathering process. The results revealed that higher lignin content and better surface hydrophobicity of heat-treated bamboo were the main reasons for their excellent photostability against weathering.

Accelerated weathering performance of injection moulded PP and LDPE composites reinforced with calcium rich waste resources

This study aims to assess and understand the accelerated weathering performance of injection moulded PP and LDPE composites reinforced with calcium rich waste resources for the first time. Two different calcium rich wastes: FGD gypsum and marble waste are incorporated without any chemical treatment in the polymer matrices. Visual appearance, chemical changes, flexural properties (strength, modulus and elongation) and surface morphology are analysed. Weathered surfaces are studied to analyse the structural changes with morphology by FTIR and SEM. LDPE showed higher visual stability by weathering with enhanced flexural properties for FGD gypsum composites. FTIR analysis revealed that the composites prepared with LDPE had a stabilizing effect on photo-degradation (minimum carbonyl index=1.09–1.14), which correlates well with the results of mechanical testing, showing these composites retained remarkable mechanical properties (retention rate>85%.) after weathering. Visual appearances, physical and mechanical properties of polymer composites are affected by the accelerated weathering condition. UV radiation in combination with temperature, humidity and water spray leads to polymer crystallinity with degradation resulting in weaker interfacial bonding and detachment of filler from matrix. Results show that the flexural strength of weathered FGD gypsum-PP, marble waste-PP and marble waste-LDPE composites decreased about 7–38%, 50–59% and 5–6%, respectively. Flexural strength of the weathered FGD gypsum-LDPE composites increased about 7–12%. The present study implies that both the reinforcements can enhance the properties of PP and LDPE composites after accelerated UV weathering exposure with potential for civil engineering applications. FGD gypsum is more prominent while structural and durability performances are taken into account.

Improvement of wood against UV weathering and decay by using plant origin substances: Tannin acid and tung oil

In this study, two kinds of plant origin substances, namely tannin acid (TA) and tung oil (TO), were used to treat wood to improve their durability during outdoor applications. For this purpose, southern yellow pine wood was firstly impregnated with TA solution and then immersed in TO at atmospheric pressure. The samples treated with TA or TO alone, as well as untreated wood, were also prepared for comparison. The performance of the different samples during accelerated UV weathering and brown-rot decay tests were evaluated. The results showed that TO imparted wood with excellent color stability against weathering, while samples treated with TA alone experienced more obvious discoloration. The presence of TO built a barrier for the penetration of UV light and water on wood surface. TA acted as a good UV absorber and free-radical scavenger during UV exposure. It also successfully prohibited the colonization of brown-rot fungi (Gloeophyllum trabeum) on wood owing to its strong antioxidation activity. Overall, wood treated with both TA and TO exhibited the best durability during photodegradation and biodeterioration process.

Improvement of acrylic-urethane paint adhesion to PP-EPDM surface by mediated electrochemical oxidation

Adhesion improvement of an acrylic-urethane paint on a bumper surface made from polypropylene/ethylene-propylene-diene monomer was investigated at long term after electrochemical treatment by 2N nitric acid and 0.6M Silver (II)-nitrate /2N nitric acid. The stability of the electrochemically treated samples was examined at different aging times by ATR and SEM. The results were also compared to those of the untreated and flame-treated samples. Accelerated UV weathering analysis along with morphology study by SEM approved the effectiveness of the Ag (II) treatment technique in long term particularly at curvature area of the bumper. For the Ag (II) treated samples, the increase in adhesion strength was sustained even after 650 hours exposure to UV irradiation in wet condition prior to bonding. In addition, the stability of the Ag (II)-treated surface was maintained for at least three months. In case of the flame-treated surface, hydrophobic recovery during aging in environment was found to reduce the polarity of the PP-EPDM surface. The pull-off test showed Ag (II) treatment can enhance adhesion strength of the acrylic-urethane coating on to PP-EPDM in comparison with the flaming method by 20.7%. Moreover the results of zeta potential analysis for Ag (II) treated blend showed a typical acidic surface.

Laccase-Catalyzed Synthesis of Low-Molecular-Weight Lignin-Like Oligomers and their Application as UV-Blocking Materials.

The laccase-catalyzed oxidative polymerization of monomeric and dimeric lignin model compounds was carried out with oxygen as the oxidant in aqueous medium. The oligomers were characterized by using gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis. Oxidative polymerization led to the formation of oligomeric species with a number-average molecular weight (Mn ) that ranged from 700 to 2300 Da with a low polydispersity index. Spectroscopic analysis provided insight into the possible modes of linkages present in the oligomers, and the oligomerization is likely to proceed through the formation of C-C linkages between phenolic aromatic rings. The oligomers were found to show good UV light absorption characteristics with high molar extinction coefficient (5000-38 000 m-1 cm-1 ) in the UV spectral region. The oligomers were blended independently with polyvinyl chloride (PVC) by using solution blending to evaluate the compatibility and UV protection ability of the oligomers. The UV/Vis transmittance spectra of the oligomer-embedded PVC films indicated that these lignin-like oligomers possessed a notable ability to block UV light. In particular, oligomers obtained from vanillyl alcohol and the dimeric lignin model were found to show good photostability in accelerated UV weathering experiments. The UV-blocking characteristics and photostability were finally compared with the commercial low-molecular-weight UV stabilizer 2,4-dihydroxybenzophenone.

Photo- and Biodegradable Thermoplastic Elastomers: Combining Ketone-Containing Polybutadiene with Polylactide Using Ring-Opening Polymerization and Ring-Opening Metathesis Polymerization

We report the synthesis of a new bio- and photodegradable ABA triblock copolymer that combines the high modulus of biodegradable poly(lactic acid) (PLA) with a novel photodegradable polybutadiene (PB). First, the central block was made by ring-opening metathesis polymerization (ROMP) of a mixture of 1,5-cyclooctadiene and an unsaturated cyclic ketone in the presence of cis-1,4-butenediol. The resulting hydroxyl-functionalized telechelic PB macroinitiator was then chain-extended by DBU-catalyzed ring-opening polymerization (ROP) of lactide. Using this combination of ROMP and ROP, the molecular weights of the A and B blocks were varied, and the resulting copolymers formed robust films with rubbery plateau moduli ranging from 180 to 1600 MPa as measured by dynamic mechanical analysis (DMA). Thermal analysis revealed that the polymers were thermally stable up to 273 °C and exhibited glass transition temperatures at −111 and 55 °C. Accelerated UV weathering was performed on thin polymer films with concentratio...

Studies on the Mechanical Properties and Uv-Accelerated Weathering of Ldpe with Benzophenone and Carboxy Methylated Starch

LDPE of MFI 2 g/10 min was blended with carboxy methylated starch (CMS) at various proportions of 5–30% (wt.%), photo-degradable additive – benzophenone (3%) and glycerol (3%) as compatibilizer using a twin screw extruder. Tubular blown film was extruded using blown film extruder. LDPE with CMS was processable into sheets (>250 microns) in the temperature range 150 to 230°C. It was observed that higher the CMS content, lower the processing temperature range. All the formulations made using CMS were easy for processing though the MFI was decreased as the CMS starch content increased. The sheets obtained were of golden-yellow color with snakeskin appearance. The sheets obtained were tested for various mechanical tests like tensile strength, elongation at break and tear strength in both machine direction and transverse direction. The mechanical properties like tensile strength and elongation at break were lowered. Tear strength was lowered. Also accelerated UV weathering and compost biodegradation tests were done on all the samples. Scanning Electron Microscope images were taken before and after UV weathering to determine the morphological changes on the samples. As the starch content increased, the photodegradation time also increased, but very less when compared to pure LDPE. The samples were highly photo/ biodegradable and hence will not pollute the environment.

Preparation of sodium ligninsulfonate‐layered double hydroxide and its effects on wood flour/polypropylene composites during accelerated UV weathering

In this study, Mg3Al‐NO3 layered double hydroxide (LDH) and sodium ligninsulfonate‐layered double hydroxide (LDH‐SL) complex were successfully synthesized. Then, 1wt% of LDH, sodium ligninsulfonate (SL), and LDH‐SL were mixed directly with wood flour and polypropylene to make wood flour/polypropylene (WF/PP) composites, respectively. Four groups of samples were made and exposed in a QUV accelerated weathering tester for a total of 960 h. The changes in their surface color and mechanical properties were tested, accompanied by characterizations using UV–Vis, SEM, and ATR‐FTIR. The results showed that (1) composites containing LDH‐SL exhibited less color change, fewer surface cracks, better thermal stability, and less losses of mechanical properties than other groups during weathering; (2) LDH‐SL was proved to be an effective organic/inorganic UV‐blocking material, with both physical shielding effect and chemical absorption of UV light; (3) ATR‐FTIR results showed that LDH‐SL alleviated the photodegradation of WPCs during weathering, confirming its antioxidant activity. POLYM. COMPOS., 39:2451–2460, 2018. © 2016 Society of Plastics Engineers

Synthesis, characterization and resistant performance of α-Fe2O3@SiO2 composite as pigment protective coatings

Abstract The natural pigment of hematite (red ocher, α-Fe 2 O 3 ) is coated homogenously with colloidal silica-nanoparticles (SiNP) by a sol-gel process to obtain a durable hematite pigment of Fe 2 O 3 @SiNP composite for artifacts preservation. The acid/alkali-resistance, color stability and UV shielding behavior of obtained Fe 2 O 3 @SiNP are investigated. The results indicate that 60 nm thickness of uniformed coating is acquired at pH = 1.3 with 90 nm particle size distribution. Fe 2 O 3 @SiNP reveals great thermal stability at 1400 °C with minor color variation and strong acid-alkali resistance properties compared to Fe 2 O 3 after 6 months' accelerated UV weathering, based on that the surface morphology of Fe 2 O 3 @SiNP remains intact while pure Fe 2 O 3 is faded with critical deterioration. Therefore, silica-nanoparticles coated on surface of Fe 2 O 3 could form a durable Fe 2 O 3 pigment against acid, alkali, thermal and long term of UV irradiation.

Effect of lignin nanoparticles and masterbatch procedures on the final properties of glycidyl methacrylate-g-poly (lactic acid) films before and after accelerated UV weathering

This article reports the preparation, by means of an innovative masterbatch procedure, of poly (lactic acid) (PLA)/lignin nanoparticles (LNP) films via premixing 1%wt. of LNP into PLA or glycidyl methacrylate (GMA) grafted PLA (g-PLA). These films were obtained by reactive extrusion and subsequent filmature process. Films obtained by using the masterbatch steps were characterized and compared with the system realized by direct extrusion of 1%wt. of LNP in PLA/g-PLA. Thermal, optical and mechanical properties, as well as morphology of LNP reinforced PLA nanocomposites, were characterized. The performance of the produced films was also investigated after accelerated UV weathering (up to 480h), with the aim of verify how the presence of lignin nanoparticles could modify transparency and mechanical performance of neat (and GMA grafted) PLA films. Results from UV–vis characterization showed how LNP better behave as UV light barrier in grafted PLA, and it has been also proved that GMA grafting onto PLA matrix promoted the dispersion of LNP in matrix. Mechanical tests after weathering also confirmed that both the presence of LNP and GMA accelerates the oxidation effect, since the increased deformability observed for systems containing 1%wt. of LNP in PLA and g-PLA systems at time 0 was lost after 240h of UV exposure.

Effects of two staining methods on color stability of wood flour/polypropylene composites during accelerated UV weathering

Two staining methods of wood flour/polypropylene composites in an attempt to improve the color stability of wood‐plastic composites (WPCs) were investigated. The first was to dye wood flour (WF) before compounding with polypropylene (PP) to make stained composites. The second method involved mixing pigments directly with WF and PP. Nine groups of composites were weathered in a QUV accelerated weathering tester for 960 h. Their surface color, surface gloss, washing resistance, and flexural properties were tested during weathering. Additionally, the weathered surface was characterized by SEM and ATR‐FTIR. The results revealed that (1) the washing resistance of composites were improved after staining treatments; (2) composites made of dyed WF showed higher surface gloss values and less cracks on weathered surface at the early stage of weathering; while composites containing pigments displayed brighter color, less color change, and less loss of flexural properties during weathering; and (3) weathering resulted in the protrusion of WF and photodegraded lignin on exposed surface. Adding pigments was proven to be more effective staining method for improving composite color stability during weathering. POLYM. COMPOS., 38:1194–1205, 2017. © 2015 Society of Plastics Engineers

Uses of 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate and Terbutryn as algaecides in low-density polyethylene mulching films for agricultural applications

The aim of this work concerned the performances and limitations of uses of two commercial biocides, namely 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate and N2- tert-butyl- N4-ethyl-6-methylthio-1,3,5-triazine-2,4-diamine (Terbutryn), in low-density polyethylene mulching film for agricultural application. The effects of type and algaecide concentration as well as aging deterioration of low-density polyethylene film surfaces were studied in relation to the mechanical, physical, and antialgal properties of the low-density polyethylene films. For antialgal evaluation, disk diffusion test and chlorophyll- a measurement technique were carried out on Chlorella vulgaris, a single-cell green algae, and Phormidium angustissimum, a blue-green algae. The results suggested that adding 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate or Terbutryn tended to slightly increase the lightness value (L*) of specimens, but did not affect the film mechanical properties. The disk diffusion test indicated that only Terbutryn at 600–1000 ppm resulted in clear zone development against C. vulgaris for low-density polyethylene film specimens. Regarding the quantitative study by chlorophyll- a measurement technique, the antialgal activities of low-density polyethylene films gradually improved with increasing algaecide concentrations. Terbutryn appeared to show more effective antialgal efficacy than 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate. Under aging deterioration, Terbutryn-low-density polyethylene films showed less degradation of mechanical properties than neat low-density polyethylene films. However, the antialgal activity of Terbutryn-low-density polyethylene films at various algaecide concentrations was reduced under both accelerated UV weathering and natural outdoor exposure.

Accelerated and Natural Weathering of Wood-Polypropylene Composites Containing Pigments

In general, wood-polymer composites are vulnerable to weathering factors such as UV radiation, moisture, freeze-thaw action. Weathering can cause discoloration, chalking, dimensional change, and loss of mechanical properties of wood-polymer composites. This comparative study was focused on weatherability of wood–polypropylene composites made with and without pigments. Two types of inorganic pigments were applied: carbon black master-batch and synthetic iron oxide. Wood-polypropylene composite made without pigment was used as a reference. Also, composites prepared with addition of wollastonite were tested. The composite samples were exposed to outdoor weathering and in a parallel the accelerated UV weathering was conducted in xenon weathering chamber for the 2000 hours. The colour change was estimated by spectrophotometric method, and the change of Charpy impact strength after weathering was determined. The surface morphology was studied with scanning electron microscopy (SEM). The addition of pigments decreased the lightness of non-weathered composites. The change of lightness and total colour change of weathered composites were affected a lot by type of pigment and method of weathering. As, expected wood-polypropylene composite made with carbon black showed the best results in colour stability of composites exposed to weathering. SEM showed that accelerated weathering in the xenon chamber caused more significant changes in the morphology of the polymer surface layer of the composites than outdoor weathering. Charpy impact strength of all studied composites was found to retain after 2000 hours of outdoor weathering, although accelerated weathering caused significant reduction of Charpy impact strength of these composites.

Studies on the Properties of Photo/Bio-Degradable Ldpe with Benzophenone and Hydrolysed Starch

Maize starch was acid hydrolyzed at 50–60°C for 6 hours. Reduced viscosity for raw starch, hydrolyzed starch (HS) and glucose were determined. DSC tests were done to determine the melting point of the modified starch. LDPE of MFI 2 g/10 min was blended with this hydrolyzed starch at various proportions of 3–20% (wt%), photo-degradable additive – benzophenone (3%) and glycerol (3%) as compatibilizer using a twin screw extruder. The formulations made using HS were easy for processing and since the MFI was increased, the starch added, proved to be hydrolyzed, Tubular blown film was extruded using blown film extruder. LDPE with hydrolysed starch are processable into thin films (< 250 microns). The films obtained were tested for various mechanical tests like tensile strength, elongation at break, etc. The mechanical properties like tensile strength and elongation at break were lowered. Tear strength and dart impact strength were lowered. Also accelerated UV weathering and compost biodegradation tests were done on all the samples. Scanning Electron Microscope images were taken before and after UV weathering and also after biodegradation to determine the morphological changes on the samples. The samples were highly photo/biodegradable and hence will not pollute the environment.

Studies on Mechanical, Thermal, Electrical Properties and Accelerated UV Weathering of PP with HIPS Blends

Poly Propylene (PP) was blended with High impact poly styrene (HIPS) (10-25%) using a twin screw extruder. Then the test specimens were prepared using an injection molding machine and testings were done as per ASTM standards. The mechanical properties like Tensile modulus, Flexural strength and Flexural modulus were increased. The impact strength, Tensile strength and elongation were decreased. In the thermal properties HDT was improved because HIPS has higher properties than that of PP. The Arc resistance was little lowered. The shrinkage was decreased. Accelerated UV Weathering was also carried out using an accelerated weather-o-meter. The PP-HIPS blends were found to be photo-degradable after 125 hours of UV light exposure in accelerated Weather-o-meter and in about 2.5 months in the out-door exposure.

Effect of Nanoalumina on the Electrochemical and Mechanical Properties of Waterborne Polyurethane Composite Coatings

A nanocomposite coating was formed by incorporating nanoalumina pigment in a waterborne polyurethane dispersion (WPUD) to different loading levels (0.1% and 1.0% by weight). Electrochemical performance of the nanocomposite coating was evaluated by applying these nanomodified coatings on mild steel substrate and exposing them to salt-spray, humidity, and accelerated UV weathering. The surface morphology of the composite coating was evaluated using various analytical techniques. SEM and AFM were used to investigate the dispersion of nanoalumina pigment and surface morphological changes of the nanomodified coating, before and after exposure to the test environment. Mechanical properties like scratch resistance were studied by using nanoscratch technique (Nanoindenter TI-900, Hysitron Inc, USA) and hardness using pencil hardness test method. The results showed an improvement in the corrosion, UV weathering, and mechanical properties of the coatings at lower concentration (0.1% by wt), indicating the positive effect of addition of nanoalumina pigment to the coating.