Hindered Amine Light Stabilizers Research Articles

Research of antiaging behavior of a new sealing coating for color painting cultural relics

PurposeThe color painting of ancient buildings has high historical and artistic value but is prone to aging due to long-term outdoor exposure. The purpose of this study is to develop a new type of sealing coating to mitigate the impact of ultraviolet (UV) light on color painting.Design/methodology/approachThe new coating was subjected to a 500-h UV-aging test. Compared with the existing acrylic resin Primal AC33, the UV aging behavior of the new coating, such as color difference and gloss, was studied with aging time. The Fourier infrared spectra of the coatings were analyzed after the UV-aging test.FindingsCompared with AC33, the antiaging performance of SF8 was substantially improved. SF8 has a lower color difference value and better light retention and hydrophobicity. The Fourier transform infrared spectroscopy results showed that the C-F bond and Si-O bonds in the resin of the optimized sealing coating protected the main chain C-C structure from degradation during the aging process; thus, the resin maintained good stability. The hindered amine light stabilizer TN292 added to the coating inhibited the antiaging process by trapping active free radicals.Originality/valueTo address the problem of UV aging of oil-decorated colored paintings, a new type of sealing coating with excellent antiaging properties was developed, laying the foundation for its demonstration application on the surface of ancient buildings.

Multiscale characterization of the UV aging resistance and mechanism of light stabilizer-modified asphalt

Abstract To clarify the effect and mechanism of hindered amine light stabilizer (HALS) on the UV aging behavior of asphalt binder, T622-HALS was selected as the modifier for UV aging resistance of asphalt. The physicochemical properties and microstructure of T622 light stabilizer were comprehensively analyzed. The light stabilizer-modified asphalt was prepared and placed in the UV radiation chamber for UV aging treatment. Scanning electron microscope and atomic force microscope were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt induced by UV radiation. The thermal properties and functional group composition changes in light stabilizer-modified asphalt during UV aging were studied by using the thermogravimetric and infrared spectroscopy combined testing system. The decay laws of the physical and rheological performances of light stabilizer-modified asphalt were studied during UV aging process, and the effect of light stabilizer on the UV aging behavior of asphalt binder was clarified. The research results indicated that HALSs could alleviate the microcracks and roughness change on the surface of asphalt and reduce the content of functional groups such as carbonyl and sulfoxide in asphalt. Furthermore, HALS could reduce the value difference of physical and rheological properties of asphalt before and after UV aging, significantly improving the UV aging resistance of asphalt binder.

First Evidence of Hindered Amine Light Stabilizers As Abundant, Ubiquitous, Emerging Pollutants in Dust and Air Particles: A New Concern for Human Health.

Hindered amine light stabilizers (HALSs) represent a crucial class of polymer additives that are extensively used in plastics and other polymeric materials. However, their environmental presence and related exposure risks have until now remained unexplored. This study addressed this critical knowledge by examining dust and air particles collected in South China, utilizing a comprehensive analytical approach to identify and quantify nine monomeric HALSs. A total of seven of the nine studied HALSs were detected in the samples, with bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin 770) and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (HS-508) identified as the most abundant and widespread pollutants. Median total concentrations of HALSs ranged from 417 to 8,830 ng/g in urban dust samples and from 28.6 to 70.9 pg/m3 in urban air particles. Notably, dust concentrations of HALSs significantly exceeded those of traditional well-known light stabilizers such as UV absorbers. Human exposure assessment indicated that in contrast to air inhalation dust ingestion represented a more substantial exposure pathway owing to the relatively low volatility of these newly identified chemicals. Predictive modeling suggests that many of the examined HALSs exhibited characteristics of persistence, high toxicity, or strong potential for long-range transport, underscoring their hazardous nature. This study represents the first comprehensive investigation into the prevalence of HALSs as a class of emerging pollutants widespread in the environment, necessitating heightened attention and further research in the future.

Aging of Environmentally Friendly Alkyd Coating Containing Tinuvin 292 under Effect of UV Radiation

This study presents durability of environmentally friendly alkyd coating containing Tinuvin 292 (a liquid hindered amine light stabilizer) under UV-thermo-humidity condition. Coatings were accelerated under UV-thermo-humidity complex for 100 cycles. FT-IR, TGA and SEM were used to value the changes of before and after accelerated weathering tested coatings. Results showed that gloss loss, adhesion, flexural strength, impact resistance, relative hardness of tested coating were much improved with 1.5 weight percent (wt.%) of Tinuvin 292. FT-IR spectrums of initial and aged coatings without Tinuvin 292 illustrated the significant changes on intensity of CH2 and C=O (ester) groups. Meanwhile, coating with Tinuvin 292 exhibited that intensity of CH2 and ester groups had been changed slightly. SEM images indicated that surface morphology of samples changed differently depending on the presence Tinuvin 292. After aging process, surface of aged coating without Tinuvin 292 became worse than that of coating with Tinuvin 292. TGA also showed that 1.5 wt.% of Tinuvin 292 had improved thermo oxidation stability of environmentally friendly coating.

Radiometric, Mechanical and Agronomic Characterization of Four Commercial Polymeric Films for Greenhouse Applications

The objective of this work was the study of four experimental plastic covers (EPCs) to assess the improvement in microclimatic conditions inside a greenhouse. This experiment was based on the comparison of four trilayer plastics: blue, grey, yellow and colorless ECPs. Radiometric and mechanical properties were studied along with the films’ behavior under semi-field conditions through their microclimate parameters. The results show that the addition of the blue pigment causes a considerable reduction in transmission (32.04%) with a reduction in the maximum temperature (+9.8 °C) compared to the other films (14% for grey, 52% for yellow and 46% for colorless). The anti-thermal additive used in the grey EPC did not achieve the desired effect, since it reduced both the photosynthetic active radiation (PAR) (62.33%) and near-infrared radiation (NIR) (62.83%) transmission equally. None of the EPCs achieved a PAR/NIR ratio greater than 1 (0.52 for blue, 0.99 for grey, 0.98 for yellow and 0.99 for colorless). Hindered amine light stabilizers (HALSs) photo-stabilizing additives block UV-A radiation (36.85 for grey) more efficiently compared to nickel quenchers (38.64 for yellow), as they allow earlier PAR transmission. The tensile test showed that all the EPCs manifested a linear relationship between stress and deformation, which defines Young’s modulus.

Stearate and hindered amine light stabilizers coordinate to boost charge storage performance of water electret melt-blown nonwovens

Water electret (WE) technology is a current research hotspot in the field of high-efficiency and low-resistance melt-blown filter materials. The electret is an important factor affecting the filtration performance and durability of WE melt-blown nonwovens. In this paper, WE melt-blown nonwovens were prepared with stearate compounded with hindered amine light stabilizer (HALS) as the electret additives, which exhibited excellent performance and the filtering efficiency of DEHS oily particles exceeding 99%. The charge formation and storage mechanism of WE melt-blown nonwoven were also elucidated by using the thermally stimulated discharge technique. Benefiting from the inherent amino group of HALS and the synergistic effect with stearate, positively charged hydrated protons were attracted and migrated to the interior of the fiber to form durable space charges, which led to a significant enhancement of the filtration/charge storage performance of melt-blown nonwoven. The charge stability performance of WE melt-blown nonwoven was also investigated under the treatment of solvents such as constant temperature and humidity, high-temperature hot water, alcohol, and isopropyl alcohol. These studies help to improve the product quality of WE melt-blown nonwovens, as well as provide a systematic guide to an in-depth understanding of the electret mechanism of WE technology.

Development of an automatic evaluation system for photooxidation and assessment of polyethylenes containing HALS and UVA

An automatic evaluation system for photooxidation has been developed by utilizing a chemiluminescence apparatus combined with a light irradiation system. The system is composed of a controller, a driving device, and irradiation equipment, which are integrated with the chemiluminescence measurement system. Various measurement conditions can be set independently, including irradiation time (fixed or variable), waiting time from irradiation to measurement, chemiluminescence measurement time, number of repetitions (up to 999 times), and measurement temperature. LLDPEs containing Hindered Amine Light Stabilizers (HALS) and Ultraviolet Absorbers (UVA) were evaluated using this system. The decay of chemiluminescence after UV irradiation was repeatedly measured at r.t. and 105℃, respectively, below the melting point of LLDPE, and the time-course of chemiluminescence was obtained by plotting time against I(t = 0) for each instance. I(t = 0) represent the rate of photooxidation under UV exposure, calculated using second-order analysis of the chemiluminescence decay. The chemiluminescence intensity increased significantly in the initial stage with irradiation time, maintained a stable intensity for a period, and then exhibited a substantial increase in the later stage. We termed the point at which this significant increase in chemiluminescence occurs as the induction time of photooxidation (photo-OIT). Using this system, the photo-OIT of LLDPE samples with HALS and UVA was measured, revealing the potential for assessing the synergistic effects of photooxidation stabilizers.

Effect of isoindole derivative pigments with planar macroconjugated structure on the UV resistance of HDPE

Different colors of high-density polyethylene (HDPE) natural gas pipelines, water supply pipelines, geomembranes in small communities, garden agriculture, and large factories, play a differentiation, warning, decorative aesthetic, and other aspects of the role. However, little research has been done on HDPE that can be used for long periods and in a variety of colors other than black and white. Phthalocyanine pigments with a large planar conjugate structure are often used in modern artists' paints because of their good stability and are hopeful for use in HDPE. For this reason, in this paper, phthalocyanine blue with a high lightfastness rating was selected. Pure HDPE and HDPE with pigment were compared by color difference, carbonyl index (CI), mechanical properties, and thermomechanical properties before and after UV irradiation. After irradiation for 2000 h, the latter not only did not fade easily but also maintained 82 % elongation at break. At the same time, the carbonyl index was much lower, representing the addition of pigments to inhibit the photo-aging process. Hindered amine light stabilizers (HALS) were also added to the matrix to further improve the ultraviolet (UV) stability along with ultraviolet light absorber (UVA). Addition of HALS and pigments had a positive effect on the UV stability of HDPE, but the excess of HALS had a negative effect on color stability, dispensability and tensile strength. Addition of UVA had little effect on HDPE/Blue/HALS. Finally, the mechanism of the phthalocyanine blue pigment in improving the light aging resistance of HDPE was investigated by ultraviolet spectroscopy. HDPE/Blue/HALS prepared in this work had a low CI and high elongation at break of all formulations at 2000 h of irradiation, indicating that it maintains good performance over a long period of time. The low color change and dispersion uniformity of that under prolonged irradiation met the long-term aesthetic needs of HDPE.

UV aging behavior evolution characterization of HALS-modified asphalt based on micro-morphological features

Abstract To clarify the effect of Hindered amine light stabilizer (HALS) on ultraviolet (UV) aging behavior of asphalt binder, the evolution history and characteristics of the UV induced micro-structure of modified asphalt were characterized. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt during UV aging. By defining the micro-structure of asphalt in aging joints induced by UV, the identification and classification of typical micro-structure are proposed. On this basis, an evaluation method based on the morphology evolution process of modified asphalt aging was proposed to quantitatively analyze the effect of HALS on the UV aging of asphalt binder. The results show that the control effect of HALS on the UV aging behavior of asphalt can be verified by SEM and AFM detection methods. At the same time, the aging interval of the asphalt modified by hindered amine was divided by the method, and it was verified that the HALS could significantly prolong the service life of the asphalt binder. The micro-morphology of asphalt binder undergoes the process of crack generation and propagation during UV aging. The micro-morphological changes of UV aged asphalt were interfered effectively by HALS, which could alleviate and control the development of UV induced micro-cracks, and promote the fusion of micro-cracks. This study provides an effective evaluation method for detecting UV aging microscopic evolution of HALS.

Evaluation of anti-ageing performance of bitumen based on rheological and chemical characterisation

ABSTRACT Improving the anti-ageing performance of bitumen plays a vital role in prolonging the service life of bituminous pavement. A bituminous additive for resisting all-weather ageing (BARAA), with excellent anti-ageing performance and fewer side effects, was developed in this study. The service life of bitumen can be doubled by using BARAA. The results show that the anti-ageing index and influence index can quantitatively evaluate the anti-ageing performance of anti-ageing additives. The BARAA was composed of amine antioxidant (1.89% by weight of base bitumen), Ni-containing antioxidant (3%) and hindered amine light stabilisers (0.7%). BARAA effectively delayed the deterioration of bitumen performance during ageing. The J nr reduction of BARAA-modified bitumen caused by ageing was 17.7% of the base bitumen. At −12°C and −18°C, the S increase of BARAA-modified bitumen caused by ageing was about 35% of the base bitumen. The oxidation during ageing was inhibited. The growth of sulphoxide groups can be curbed by BARAA. After long-term ageng, the aromatic ring increase of BARAA-modified bitumen was 41.1% of the base bitumen. In addition, the increase of average molecular weight and functional group index of BARAA-modified bitumen caused by long-term ageing was 57% and 19.1% of the base bitumen, respectively.

Evaluation on Feasibility of Carbon Black and Hindered Amine Light Stabilizer as UV-Resistant Additives of Asphalt Binder

Abstract Ultraviolet (UV) radiation is one of the main causes of asphalt pavement aging. The development of UV-resistant technology is of great significance to improve the durability of asphalt pavement. In order to evaluate the feasibility of carbon black (CB) and hindered amine light stabilizer (HALS) as UV-resistant additives, the modified asphalt binders were prepared by adding CB and HALS. The dispersibility of UV-resistant additives in asphalt binder was evaluated by using a fluorescence microscope. Then, the aging resistance of additives and their effects on virgin asphalt binder were qualitatively evaluated by calculating rheological parameters. The new aging-resistant index and impact index were defined. The results show that the aging-resistant index and impact index can accurately characterize the aging resistance of additives and their effect on virgin asphalt binder. The UV-resistant additives slowed down the aging rate of asphalt binder. A 3 % dosage of CB had a great adverse effect on the properties of virgin asphalt binder. HALS showed good UV resistance and had little effect on virgin asphalt binder. The aging-resistant index of asphalt binder modified by HALS was about 1.63 times that of the asphalt binder modified by CB at the same dosage (1 %). The aging-resistant index of asphalt binder modified by 1 % HALS was only about 1.31 times that of asphalt binder modified by 0.5 % HALS. In addition, the dosage of HALS was changed from 0.5 % to 1 % and the impact indexes changed to more than 2.67 times. It was considered that HALS was more suitable for improving the aging resistance of asphalt binder with an optimal dosage of 0.5 %.

Antioxidant Protection of Paper Heritage Objects with 4-Amino-2,2,6,6-Tetramethylpiperidine.

In protecting cultural heritage, deacidification is used to stabilize acidic papers, ensuring the neutralization of acids present in the paper. But in the process of aging, several mechanisms of degradation occur simultaneously. Therefore, substances used to stabilize the paper should contain an antioxidant component in addition to the deacidifying component. The effect of the antioxidant (hindered amine light stabilizers-HALS type) on the stabilization of lignin-containing acid papers during accelerated aging was studied in this work. The effective deacidification component was magnesium; the solvent was hexamethyldisiloxane (HMDSO). The 4-amino-2,2,6,6-tetramethylpiperidine series of hindered amine light stabilizers (HALS) was selected as appropriate for creating a modifying system based on HMDSO. The modification system was tested on samples of a model test acid lignin-containing paper (NOVO) and naturally aged acidic paper from the real book. The addition of substances to the proposed deacidification system has a favorable effect on stabilizing the pH during aging and provides the inhibition of the oxidative degradation products and stabilization of the cellulose degree of polymerization. It was confirmed that the application of the system containing deacidification and an antioxidant component may increase the effectiveness of the protection of acid groundwood paper heritage objects. Adding a tested antioxidant to the proposed deacidification system has a favorable effect on stabilizing the pH value for a long time in accelerated aging.

Rheological Properties and Microscopic Characterization of Delayed Decay-Modified Asphalt Based on UV Ageing

For clarifying the applying feasibility of hindered amine light stabilizers in asphalt binder, two types of hindered amine light stabilizers were chosen as a UV ageing resistance modifier and the modified asphalt was prepared with a selected UV ageing resistance modifier. The ultraviolet aging testing method of asphalt materials was proposed for UV ageing behavior characterization. Under the condition of different frequencies, the impact of UV ageing resistance modifier on asphalt was investigated through using the frequency sweep test of DSR. Under the effect of ultraviolet aging, the variation of thermal properties of UV ageing resistance-modified asphalt was deeply analyzed by means of a temperature scanning test of DSR following the increase of temperature. The change law of the surface morphology of light stabilizer-modified asphalt was characterized by atomic force microscopy (AFM) dynamically with the UV aging time extension. The research results showed that the hindered amine light stabilizer could improve the high temperature performance of asphalt and achieve the UV aging behavior of asphalt materials effectively. Meanwhile, the corresponding reaction mechanism was explored at the microscopic level.

Fabrication life prediction model for HDPE/Cr2O3 composites toward roof passive cooling

Passive cooling materials have been widely investigated to reduce building energy consumption. However, references about life prediction of the materials are insufficient. In this work, a novel life prediction model based on the passive cooling composites was established. The inorganic pigment chromium oxide (Cr2O3) was introduced into the high density polyethylene (HDPE) matrix to prepare HDPE/Cr2O3 composites with high long wave infrared (LWIR) emissivity and near infrared (NIR) reflectivity. The composites showed excellent cooling performance and color stability. The addition of ultraviolet absorber (UVA) and hindered amine light stabilizer (HALS) further improved the UV resistance of HDPE/Cr2O3 composites. HALS performs better and meets the needs of long-life outdoor use. Furthermore, a new failure point selection method is proposed and a model is established to predict the actual service life of HDPE/Cr2O3 composites, which provides theoretical guidance for the outdoor long-life use of the polymer composites. Based on the model, the fabricated HDPE/Cr2O3/HALS system can be used for more than 15 years. The long-term cooling composites can be used for building roof and wall to effectively reduce the indoor temperature and realize the sustainable use of energy. Besides, if used in military engineering, it has excellent cooling function and military camouflage effect. In addition, the composites can also be widely used in outdoor decoration, artificial lawn, floating materials and other fields.

Fatigue of Donor‐Acceptor Stenhouse Adducts in Polymer Matrices and Solution

AbstractThe fatigue performance of a range of donor‐acceptor‐Stenhouse‐adducts (DASAs) has been investigated to identify degradation mechanisms. The dyes were found to fatigue with and without exposure to light in both solution and in films. Excluding light below about 430 nm resulted in almost complete thermal recovery after exposure, however, a range of common film additives including hindered amine light stabilizers (HALS) and other additives (especially bases) were shown to react with the DASAs resulting in irreversible fatigue. The rate of fatigue was also found to increase with the relative strength of the donor and acceptor moieties in the molecule.

Identification and quantification of additive-derived chemicals in beached micro–mesoplastics and macroplastics

Although marine plastic debris are expected to retain various chemical additives, little is known about the additives that are retained. We conducted a screening analysis of additives in 261 macroplastic and micro–mesoplastic debris from two beaches. We detected 52 chemicals—antioxidants, phthalates, ultraviolet stabilizers, hindered amine light stabilizers, and flame retardants—and quantified the concentrations of 15 of them. Comparison of the concentrations of Irgafos 168, an antioxidant stabilizer, among sample categories indicated that leaching had occurred from micro–mesoplastics. Differences in diffusion rates between polymer types may explain faster leaching from polyethylene than polypropylene. The significant amounts of Irgafos 168 retained in even micro–mesoplastics indicated the importance of plastics as a vector of additives. This study provides fundamental data needed to assess the risks to organisms from exposure to plastic additives and to understand the effect of stabilizers on the aging behavior of marine plastics.

The Effect of Ultraviolet Light Stabilizers on Color Stability, Melt Properties and Tensile Properties of Mixed Waste Plastics Blends

Plastic waste disposal is among the most challenging problems of the current era. Therefore, new methods and applications for the utilization of waste plastics are increasingly needed. To find them, it is essential to research and develop the material properties of recycled plastics. The effect of different ultraviolet light (UV) stabilizers on the color stability, melt properties and tensile properties of mixed waste plastics blends was studied in this paper. The mixed waste plastics collected from two different waste sources were prepared as specimens by injection molding, and studied with two different types and loading amounts of UV stabilizers. UV absorbers (UVAs) and hindered amine light stabilizers (HALS) were used as UV stabilizers. A specimen produced without the addition of a UV stabilizer was used as a reference specimen of both the blends. After the accelerated weathering, the addition of a UVA provided an improved, smaller change in color than the addition of HALS. Among the tensile properties, the addition of UV stabilizers clearly improved the tensile strength and tensile modulus for almost all the studied specimens. Additionally, the melt properties of both the studied plastic blends were found to be increased by the addition of UV stabilizers.

Property Characterization of Anti-Aging Additives and Modified Asphalt Based on Long-Term Aging Behavior

In order to achieve the good application of hindered amine light stabilizer (HALS) in the long-term aging control of asphalt pavement material, Tinuvin770 and Tinuvin622 light stabilizers were selected as modifiers for asphalt. The microstructure and characteristics of hindered amine light stabilizers were characterized by FIB-SEM. The elemental composition and relative content of hindered amine light stabilizers were studied by means of EDS analysis. The functional group composition of hindered amine light stabilizers was analyzed based on Dynamic-FTIR. On this basis, light stabilizer modified asphalt was prepared, and the effect of hindered amine light stabilizer on the thermal rheological properties of asphalt binder during UV aging period was studied by dynamic shear rheology (DSR). The changing law of low temperature rheological properties of hindered amine light stabilizer modified asphalt was evaluated by low temperature bending beam rheological test (BBR). The results showed that the hindered amine light stabilizer could capture the free radicals formed during the photodegradation of asphalt when subjected to ultraviolet aging. Under the impact of ultraviolet aging, hindered amine light stabilizer could improve the high temperature performance of asphalt binder. Furthermore, HALS could achieve the improving effect on the low temperature rheological properties and long-term aging performance of asphalt pavement materials.

Constructing cross-functional intumescent flame retardants with UV resistance for polypropylene composites

Cross-functional additives were carefully designed for polypropylene (PP) composites to enhance the flame retardancy, UV resistance, and mechanical properties. In this work, first, ammonium polyphosphate (APP) was coated with polysiloxane to avoid the pyrolysis of APP under UV irradiation; second, the charring formation agent (CFA) with triazine groups was selected to enhance the absorbance of UV radiation. Hindered amine light stabilizer (TEMP) was reacted with sodium lignin sulfonate (SLS) to obtain SLS-TEMP. By using 19 wt.% (SiAPP/CFA)/2 wt.% SLS-TEMP, the limiting oxygen index of the PP composite was increased to 33.5 and the UL-94 grade was achieved to V-0. The peak heat release rate and peak smoke release rate were reduced by 76% and 74% compared with that of the control PP sample, respectively. Moreover, the aging process of the PP composite sample was delayed. The tensile and impact strength of the PP/19 wt.%(SiAPP/CFA)/2 wt.%SLS-TEMP sample was decreased by 13.4% and 27.8%, respectively after 60 h UV irradiation, which was significantly lower than that of control PP (50.9% and 68%). The change of limiting oxygen index before and after aging was minimal, and the sample still passed UL-94 V-0 grade after 100 h UV-aging test. It was proved that the SLS-TEMP has an excellent synergy effect on improving the flame retardancy and UV resistance of PP. This cross-functional additive strategy provides a good solution for obtaining high-performance PP composites.

The kinetic degradation of LDPE films subjected to aggressive environments

The effect of natural and thermo-oxidative aging on the structure and physicochemical properties of LDPE films stabilized with hindered amine light stabilizers (HALS) was investigated. Based on multiple linear regression analysis (MLRA) mathematical models to predict the lifetime of the LDPE were developed. Four statistical criteria were used to evaluate the developed models: residual variance, coefficient of determination, Student's test and the Fisher-Snedecor test. The half-life times predicted by the mathematical models were found to be statistically significant (p < 0.05).