UV Weathering Research Articles

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.

Development of durable self-cleaning coatings using organic–inorganic hybrid sol–gel method

Self-cleaning coatings with excellent water-repellence and good mechanical properties are in high demand. However, producing such coatings with resistance to mechanical abrasion and environmental weathering remains a key challenge. Mechanically robust coatings based on tetraethylorthosilicate (TEOS) and glycidoxypropyltriethoxysilane (Glymo) have been prepared using a sol–gel method. Emphasis is given to the addition of Glymo, an epoxy silane which creates an organic matrix that blends with the inorganic SiOSi matrix formed from the TEOS. The combination of the blended matrix produced coatings with good adhesion to substrates and improved mechanical properties. Fluoroalkylsilane (FAS) and silica fillers were introduced to increase the hydrophobicity of the coating. It was found that the water contact angle (CA) of these coatings increases from 115° to 164° upon decreasing filler size from 1–5μm to 10–20nm. The sliding angle (SA) for coatings with 15wt.% loading of 10–20nm silica is around 2°. UV weathering does not show significant effect on the properties of the coatings. Mechanical properties and performances including hardness, Young's modulus, coating adhesion and abrasion resistance were systematically analyzed. In the current work, a simple self-cleaning test, which measures the extent of dirt accumulation and subsequent removal by water spray, was performed. The coatings with 15wt.% loading of 10–20nm silica particles show the best self-cleaning performance both before and after mechanical abrasion. The developed coating process is simple and can be easily scaled-up for large surfaces that require self-cleaning function.

Effects of a layered double hydroxide (LDH) on the photostability of wood flour/polypropylene composites during UV weathering

MgAl–CO3-LDH was synthesised and proved to play a positive effect on alleviating the photo-oxidation of wood flour/polypropylene (WF/PP) composites, confirming its UV-shielding effect.

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.

Effects of UV weathering on surface properties of polypropylene composites reinforced with wood flour, lignin, and cellulose

In this study, the influence of accelerated weathering on polypropylene composites reinforced with wood flour (WF), lignin, and cellulose at different loading levels were evaluated. Six groups of samples were exposed in a QUV accelerated weathering tester for a total of 960h. The surface color, surface gloss, contact angle and flexural properties of the samples were tested. Besides, the weathered surface was characterized by SEM and ATR-FTIR. The results revealed that (1) the discoloration of composites was accelerated by the presence of lignin, especially at high content; (2) composites containing lignin showed less loss of flexural strength and modulus, less cracks, and better hydrophobicity on weathered surface than other groups, confirming its functions of stabilization and antioxidation; (3) cellulose-based composites exhibited better color stability but more significant deterioration in flexural properties after weathering compared to other composites, suggesting that such kind of composites could not be used as load-bearing structure in outdoor applications.

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.

Preparation of Waterborne Polyurethane‐OMt Nanocomposites and Effect of Clay on UV Degradation

SummaryWaterborne polyurethane polymers (WPU) have gained importance for some decades because of their environmentally friendly characteristics due to low or zero content of solvents. Polyurethane properties can be modified by changing segmental structure or incorporating inorganic fillers into the polymer matrix. Montmorillonite (Mt) clay which is a member of smectite family is widely used in polymer clay composites as a filler. In this work, linear WPU nanocomposites were synthesized using different polyols as soft segment via acetone process which has many advantages over the prepolymer mixing process in terms of reliable reproducibility and convenience for obtaining linear polyurethanes. Sodium modified montmorillonite (NaMt) clay was used without any chemical pretreatment. WPU nanocomposites were prepared via in‐situ polymerization method by modification of sodium modified montmorillonite (NaMt) clay in polyol and following polyurethane reaction. Finally, spectroscopic, thermal, morphological characterizations and UV weathering tests carried out. As a result, different thermal and mechanical properties were observed due to different soft and hard segment content. Furthermore, increasing clay content caused lowering of resistance against UV degradation.

Synthesis and film performances of SiO2/P(MMA-BA) core–shell structural latex

• Core–shell structured latex with as high as 60 wt% of SiO 2 nanoparticles have been synthesized. • The nanocomposite film presents >90% transmittance in visible range. • The nanocomposite film displays significantly improved mechanical property. • The nanocomposite film exhibits obviously UV weathering resistant property. In this study, we have successfully synthesized silica/poly(methyl methacrylate-butyl acrylate) (SiO 2 /P(MMA-BA)) core–shell nanocomposite colloids via in situ emulsion copolymerization using cationic 2,2′-azobis(2-amidinopropane)dihydrochloride (AIBA) as the initiator and the 3-Glycidoxypropyl-trimethoxysilane (GPTMS)-modified SiO 2 nanoparticles as the seeds. The SiO 2 nanoparticles embedded can reach as high as 60 wt%. The nanocomposite film presents almost the same high transparency as the pure polymer film (>90% transmittance in visible range), and displays significantly improved mechanical and UV weathering resistant properties over its pure polymer film.

Effects of UV weathering on the mechanical and antibacterial performance of peroxide‐cured silicone rubber containing biocide HPQM

2‐Hydroxypropyl‐3‐piperazinyl‐quinoline carboxylic acid methacrylate (HPQM) was used as a biocide in a silicone rubber compound. Antibacterial and mechanical performance of the compound was assessed before and after exposure to UV light for different times. Drop‐plate and halo tests were employed to evaluate qualitatively and quantitatively the antibacterial performance of the compound against Escherichia coli (E. coli, ATCC 25922) and Staphylococcus aureus (S. aureus, ATCC 25923). The results showed that the cure characteristics and the physical and mechanical properties of the HPQM‐containing rubber compound were strongly affected by the UV light. The tensile properties and hardness increased with UV aging. The lightness (L*) of the rubber compound without HPQM did not change with UV exposure, whereas that for the compound with HPQM decreased with UV exposure. The longer the contact time, the better the ability for killing the bacteria. After experiencing initial UV aging for 3 days, the rubber compound with HPQM showed an effective killing ability. However, after prolonged UV exposure, the antibacterial efficacy was reduced as a result of HPQM removal from the rubber surface during the condensation stage and a post‐curing reaction of the residual peroxide in the rubber compound. Under UV light, the silicone rubber compound with HPQM had a greater preference for killing the E. coli. J. VINYL ADDIT. TECHNOL., 20:49–56, 2014. © 2014 Society of Plastics Engineers

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.

About the end life of novel aliphatic and aliphatic-aromatic (co)polyesters after UV-weathering: Structure/degradability relationships

A novel class of aliphatic polyesters, and their derived copolyesters, have been developed. Beside their specific mechanical and thermal properties, the durability, in terms of biodegradability and photodurability, has been investigated. In particular, the polymers were submitted to natural and accelerated photo-ageing and an original methodology based on melt rheology has been applied to determine molecular changes upon UV weathering. Both scission and recombination reactions, which strongly compete as a function of the exposure time, were found to cause a strong evolution of the molecular structure. The results indicate that chemical structure and stereochemistry of the novel materials define the predominant process and the overall behaviour of the samples upon UV exposure. Moreover, the changes of the molecular structure, induced by UV irradiation, could have a significant role into the further biodegradability of the polymers. Therefore, while the relationships between structure and durability enable to design materials with desired well-adapted performances according to their final destination, the biodegradable character upon lifetime use is considered as really questionable and needs further studies.

Structural Changes in Wood under Artificial UV Light Irradiation Determined by FTIR Spectroscopy and Color Measurements – A Brief Review

UV weathering, a process initiated primarily by the ultraviolet portion of the solar spectrum, causes surface degradation of wood. Additionally, the wetting and drying of wood through precipitation, diurnal and seasonal changes in relative humidity, abrasion by air particulates, temperature changes, atmospheric pollution, oxygen, and human activities, all contribute to the degradation of wood surfaces. Photo-oxidation or photo-chemical degradation affects only the wood surface, starting immediately after exposure to sunlight. Understanding the chemistry of UV degradation of wood requires knowledge of the chemical nature of wood components, the UV spectrum, and the interactions of UV radiation with various chemical structures in wood. Chemical changes can be evidenced by FTIR spectroscopy. Previous study has shown that wood chemical modification with succinic anhydride makes it slightly more stable to the artificial light action than non-modified wood, which might be due to a slight increase in lignin stability to the polychromatic light action. Analysis of color changes on coated wood surfaces for modified wood treated with epoxidized soybean oil (ESO) has shown that lightness (ΔL*) decreases, whereas a*, b*, and ΔE* increase with increasing irradiation time.

Polyester based-siloxane modified waterborne anticorrosive hydrophobic coating on copper

Polyester-based, polydimethylsiloxane (PDMS) modified waterborne, thermal cured hydrophobic coating was developed for corrosion protection of copper using hexa(methoxymethyl)melamine (HMMM) as a cross-linker and para-toluene sulphonic acid (p-TSA) as catalyst. The cross-linking ratio for polyester resin and HMMM was fixed based on preliminary studies to 70:30, based on FTIR-imaging and DSC studies. The coatings were applied on pre-treated copper panels by dipping method and were cured at 160°C for 20min. Electrochemical performance of the modified coating was investigated and compared with neat polyester coating using potentiodynamic polarization study and exposing the coated samples to salt spray environment and UV weathering. The structural and morphological features of the coating before and after exposure to the test environment were analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM/EDAX). Mechanical properties like, the hardness and scratch resistance of the coatings were determined by nano-indentation and nano-scratch tester respectively. Hydrophobic property of the coating was determined by contact angle measurement. The siloxane modified coating was found to have improved electrochemical and mechanical properties along with excellent hydrophobicity, as compared to the neat polyester coating.

Durability of transesterified jute geotextiles

A process for transesterifying jute fibers or textiles using reagents largely derived from natural sources has been developed for enhancing the long-term tensile strength and water repellence of fiber or textile samples. Geotextiles woven from treated jute fibers (JG1) and geotextiles treated at the fabric level (JG2) using the process developed in this study were found to retain 50% of their initial tensile strengths after remaining immersed in aqueous solutions with pH between 4 and 9 for 120 days. Correspondingly untreated jute geotextiles (JGU) retained only 15% of its initial tensile strength. Upon being immersed in 3% NaCl solution for 120 days, JG1 retained 82% of its initial tensile strength, while JG2 and JGU retained 64% and 17%, respectively. JG1 samples are estimated to loose 50% of their initial tensile strength after 1115 and 1584 days, respectively, because of UV and moisture related weathering and biodegradation in tropical outdoor environments. The corresponding estimates for JG2 were 881 and 1080 days, respectively. These estimates were about 3–5 times higher than those for JGU. Additionally, degradation of treated fiber or fabric did not produce toxic or hazardous leachate. These enhancements may make jute geotextiles useful in earthworks requiring temporary reinforcement before insitu processes, e.g., vegetation growth, filter cake formation, and development of weak cementation due to biogenic and other processes strengthen the soil obviating further need for reinforcements.

Influence of lignin content on photodegradation in wood/HDPE composites under UV weathering

The aim of this work was to examine the influence the lignin component of wood on the photodegradation of high-density polyethylene (HDPE) in wood/HDPE (WPE) composites. The neat HDPE and wood/HDPE composites were prepared using a twin screw extruder followed by an injection moulder. The lignin content was varied from 0 to 29 %wt. of wood by the addition of delignified wood pulp into wood flour. The results suggested that the photodegradation of HDPE in WPE composites was accelerated by the presence of lignin; the chromophoric groups in the lignin enhanced UV adsorption onto the WPE composite surface. The carbonyl and vinyl indices, color, percentage crystallinity, and the melting temperature increased when the lignin contents were increased. The color fading in WPE composites resulted from photobleaching of lignin. In addition, the presence of lignin led to the development ofl cracks in WPE composites, especially at high lignin contents. For the effect of UV weathering time, the carbonyl and vinyl indices, discoloration, and percentage crystallinity increased as a function of UV weathering times, whereas the melting temperature of HDPE in both neat HDPE and WPE composites and water absorption of specimens decreased; the wood index in WPE composites increased during the initial UV weathering times and then decreased at 720 h weathering time.

UV Weathering Effect on Antibacterial Performance in Silicone Rubber Compounds

Silicone rubber compounded with three different types of antibacterial agents: namely; nanoAg colloids, Silver substituted Zeolite compound (SSZ) and 2-Hydroxypropyl-3-Piperazinyl-Quinoline Carboxylic Acid Methacrylate (HPQM) were prepared and changes in antibacterial performance were assessed before and after exposure to UV light at different aging times. Drop plate and halo tests were performed to study the antibacterial performance of silicone rubber compounds. The results indicated that antibacterial activity of silicone compound changed when the UV aging time was increased. The antibacterial activity of the rubber added with HPQM extremely decreased considered by the inhibition zone and %reductions of Staphylococcus aureus and Escherichia coli bacteria for any given contact times. On the other hand, the UV light did not affect the antibacterial activity of silicone rubber compounds added with nanoAg colloids and SSZ agents.

Stabilizations of molecular structures and mechanical properties of PVC and wood/PVC composites by Tinuvin and TiO2 stabilizers

AbstractThree different UV stabilizers, 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐ditertpentylphenol (Tinuvin XT833), 2‐(2H‐benzotriazol‐2‐yl)‐p‐cresol (Tinuvin P), or rutile–titanium dioxide (TiO2) were incorporated into poly(vinyl chloride) (PVC) and wood/PVC (WPVC) composite, and mechanical and physical properties and photostabilities were monitored. The polyene and carbonyl sequences of PVC increased with UV weathering time and with presence of wood flour. The yellowness index increased because of polyene and carbonyl productions, whereas the brightness increased because of the photobleaching of lignin in wood. The photostabilities of PVC and WPVC could be improved through the use of UV stabilizers. Tinuvin P was recommended in this work as the most effective stabilizer for PVC and WPVC composites. The stabilization effect was interfered by presence of wood particles. The mechanical property changes corresponded well to the structural changes under UV for neat PVC. For WPVC composites, the presence of wood particles played more significant effect on the mechanical properties during UV aging than the UV stabilizer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Analysis of the whitening phenomenon of a thermoplastic elastomer article by UV weathering

A thermoplastic elastomer (TPE) article composed of polypropylene (PP) and ethylene-propylene-diene terpolymer (EPDM) was weathered by exposure to UV radiation of wavelength 340 nm for 80 days. The aged sample surface changed to grayish-white. The aged surfaces were analyzed using GC/MS, an image analyzer, SEM, EDX and ATR-FTIR to examine the cause of the whitening. Organic materials bloomed on the aged sample surface were collected and analyzed, but no significant materials were found. Tiny cracks were found on the grayish-white sample surface. The ATR-FTIR spectrum of the grayish-white sample surface showed a carbonyl group. The grayish-whitening phenomenon is caused by scattering of visible light on the tiny cracks produced by dissociation of the polymer chains by UV light. When the TPE article was thermally aged at 90 °C without UV radiation, the whitening phenomenon was not observed. We also found that the whitening phenomenon was not observed when UV absorbers and UV stabilizers were compounded into the TPE.

Effects of UV weathering and a CeO2‐based coating layer on the mechanical and structural changes of wood/PVC composites

AbstractComposite samples (WPVCs) of poly(vinyl chloride) (PVC) and wood flour were prepared in the PVC:wood weight ratio of 1:1, and the mechanical and structural changes of the composites were assessed in terms of UV aging time and condensation temperature. Acrylic coating containing cerium dioxide as a UV absorber was used for moderation of the mechanical and structural changes of PVC in the WPVC composites. The experimental results indicated that the tensile and flexural properties of the composites monotonically decreased when the aging time was increased, the effect being more pronounced at high condensation temperatures. It was observed that the polyene and yellowness indexes of the WPVC composites increased with UV aging time. The hydrophilicity of the WPVC was quantified by contact angle results and found to increase with increasing UV aging because of hydrogen bonding between OH groups on the wood surfaces and water molecules. The acrylic coating containing CeO2 proposed in this work was sufficiently effective for maintaining the levels of hydrophilicity and mechanical properties of the WPVC composites. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers