Polymeric Hindered Amine Light Stabilizers Research Articles

Comparison of UV resistance of HDPE added with hindered amine light stabilizers with different molecular structures

UV resistance of versatile plastics has been received attention for a long time, especially of high‐density polyethylene (HDPE). It was studied systematically that hindered amine light stabilizer (HALS) with different molecular structures had an effect on the UV resistance of HDPE. The molecular weights of the two HALS were 423.7 and 2100–3000 g/mol, respectively. It was found that the low‐molecular‐weight HALS outperforms the polymeric one of HDPE matrix in UV resistances due to the different molecular structures. HDPE‐containing HALS with different molecular structures followed different degradation mechanisms during artificial accelerated aging. In addition, HDPE matrix composites with low‐molecular‐weight HALS show better mechanical properties than the polymeric one because of the decrease of delay of molecular chain fracture during irradiation. Therefore, HDPE matrix composites with low‐molecular‐weight HALS have better UV degradation resistance. However, polymeric HALS has the advantage of hard to move out of the sample surface.

Preparation of PUV-3853 and Its Mechanical Properties in ABS Resin

This paper mainly studies the synthesis of polymeric hindered amine light stabilizers by copolymerization, UV3853 (2,2,6,6-tetramethyl-4-piperidine stearate) as monomer, styrene (St The functional monomer, toluene is used as a solution, and the initiator is azobisisobutyronitrile (AIBN), and the hindered amine light stabilizer is synthesized by solution blending. The ABS composite is prepared by melt blending of the product and ABS pellets. The composite is tested for impact and tensile properties. The results show that when the addition amount of PUV-3853 is 0.1% (mass fraction), the mechanical properties of the composites are the best.

Enhancement of UV-aging resistance of UV-curable polyurethane acrylate coatings via incorporation of hindered amine light stabilizers-functionalized TiO2-SiO2 nanoparticles

In this study, polymeric hindered amine light stabilizers (HALS)-functionalized silica coated rutile titanium dioxide (TiO2-SiO2) nanoparticles were prepared by encapsulating commercially available TiO2-SiO2 nanoparticles with methyl methacrylate (MMA) and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPM) copolymers via miniemulsion polymerization. The obtained functional (TiO2-SiO2/P(MMA-co-PMPM)) fillers have been added to polyurethane acrylate (PUA) oligomers to get UV-curable nanocomposite coatings. The functionalization of the TiO2-SiO2 nanoparticles with polymeric HALS has been confirmed by infrared spectra (IR), thermogravimetric (TG), and X-ray photoelectron spectroscopy (XPS) analyses. The scanning electron microscope (SEM) micrographs indicated that homogeneous dispersion of TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles resulted in improved transparency and mechanical properties of the UV-curable PUA coatings. Rhodamine B (Rh.B) photodegradation measurement confirmed the excellent UV-shielding performance of PUA nanocomposite coatings containing TiO2-SiO2/P(MMA-co-PMPM). The addition of TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles reduced the UV-curable PUA coatings degradation rate dramatically. The UV-aging resistance of PUA coatings was improved significantly. Over all, the combination of TiO2-SiO2 nanoparticles and polymeric HALS offers an attractive way to fabricate the multi-functional fillers, which can be used to improve the mechanical properties and UV-aging resistance of PUA coatings simultaneously.

TiO2–SiO2 composite nanoparticles containing hindered amine light stabilizers encapsulated by MMA–PMPM copolymers

TiO2–SiO2 composite nanoparticles containing hindered amine light stabilizers (HALSs) were prepared by encapsulation of commercially available TiO2–SiO2 nanoparticles using methyl methacrylate (MMA) and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPM) copolymers through mini-emulsion polymerization. The Fourier transform infrared spectral analysis (FTIR) showed that the hindered amine light stabilizer PMPM was incorporated into the TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles. The X-ray photoelectron spectroscopy analysis (XPS) showed that the surface of TiO2–SiO2 nanoparticles was enriched with HALS moieties. The formation of P(MMA-co-PMPM) random copolymers on the surface of TiO2–SiO2 nanoparticles was determined by differential scanning calorimetry (DSC), and the percentage of the chemically grafted P(MMA-co-PMPM) coverage on the TiO2–SiO2 nanoparticles surface was 40.9 wt% determined by thermogravimetric analysis (TGA), which revealed that the TiO2–SiO2 nanoparticles were successfully encapsulated by MMA–PMPM copolymers. Scanning electron microscopy analysis indicated that the TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles were mainly homogeneous spherical shape particles, with an average size of about 90 nm. Rhodamine B (Rh.B) photocatalytic degradation study revealed UV-shielding characteristics for TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles and showed a remarkable decrease in photocatalytic activity of TiO2–SiO2 nanoparticles. These results indicated that TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles may be promising light stabilizers with covalent functionalization of polymeric HALS, which has little photocatalytic activity, and can be introduced into the weathering-resistant polymer materials to improve their application properties.

Development of complementary HPLC-DAD/APCI MS methods for chemical characterization of pharmaceutical packaging materials

The chemical characterization of plastics for pharmaceutical packaging has been subject to ever increasing regulatory scrutiny, the reasons for which being: a) plastic additives and degradation products can be extremely hazardous to the patients’ health (especially patients on chronic therapy) and b) they offer no therapeutic or formulatory benefit whatsoever. The last decade has seen the issuing of several books, monographs and guidelines dealing with extractables and leachables, however the amount of scientific work done so far is still fairly small (the majority of it performed by only a few research groups), with only a small number of methods published in the literature.This work focuses on developing a set of two complementary HPLC-DAD/APCI MS methods for simultaneous separation, detection, identification and quantification of a wide variety of packaging additives and degradants, the second method specifically targeting a group of compounds known as polymeric hindered amine light stabilizers (HALS), which are known to be notoriously difficult to separate and analyze with standard analytical techniques. The methods are capable of detecting plastic additives present in low ppb concentrations, from samples extracted in solvents with various polarities and pH values.Both methods were developed and optimized using system suitability mixtures comprised of 9 additives commonly encountered in plastic materials, and their practical applicability tested on a variety of extracts from low-density polyethylene (LDPE) and polypropylene (PP), where several additives were successfully separated, detected and identified.

Synthesis and photostabilizing performance of a polymeric HALS based on 1,2,2,6,6-pentamethylpiperidine and vinyl acetate

Polymeric hindered amine light stabilizers (polymeric HALS) have been extensively studied because they combine a high ability to protect the polymers against harmful effects of weathering with minimum physical loss. In this study a new polymeric N-methylated HALS was synthesized by the radical copolymerization of a cyclic tertiary amine with vinyl acetate (VAc). 4-Acryloyloxy-1,2,2,6,6-pentamethylpiperidine (APP), the cyclic tertiary amine, was prepared by the initial conversion of 2,2,6,6-tetramethyl-4-piperidinol derivatives via two different routes. The APP/VAc copolymer synthesized was characterized by size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance (13C NMR). The photostabilizing performance, particularly the induction period of polypropylene (PP) films containing different concentrations of APP/VAc copolymer, when exposed to accelerated aging, was comparable to that of PP films compounded with commercial polymeric HALS.

Synthesis of cyclic diepoxide — HALS addition polymers and their photostabilizing effects on styrenic polymers

A new cyclic, hindered amine light stabilizer (HALS) was prepared by the addition polymerization of a diepoxide and 4-amino-2,2,6,6-tetramethylpiperidine, and its photostabilizing effects on styrenic polymers were examined. The chemical structure of cyclic HALS was characterized by MALDI-TOF mass spectrometry. The prepared cyclic HALS had a moderate molecular weight (\( \overline M _w \) = 900∼1,100) and high thermal stability (Td ≈ 300 °C) that were compatible with styrenic polymers, such as polystyrene and styrene-butadiene rubber. The photostabilization effect of cyclic HALS was similar to or better than that of Tinuvin 770, a commercially available polymeric HALS. A synergistic effect between cyclic HALS and a UV absorber on the inhibition of photo-oxidation was observed.

Synthesis, Characterization, and Performance Evaluation of Polymeric Hindered Amine Light Stabilizers (HALS) in EPDM

AbstractPolymeric hindered amine light stabilizer (HALS), wherein the hindered amine functionality was attached to the brominated ethylene-propylene-diene terpolymer (EPDM) was synthesized. The brominated EPDM was synthesized as an intermediate for the synthesis of a new polymeric hindered amine light stabilizer. The grafting and functionalization reactions were characterized by FTIR and 1HNMR spectroscopy. The photostabilizing efficiency of this polymeric HALS was studied and compared with conventional HALS under accelerated weathering conditions. The results of the study give evidence for superiority of polymeric HALS over that of melt blended conventional HALS.

Synthesis and characterization of hindered amine light stabilizers based on end functionalization of polypropylene

AbstractA polymeric hindered amine light stabilizer (HALS), where HALS moiety was attached at the terminal end of the polypropylene chain via end‐functionalized vinylidine PP through simple organic reactions, was synthesized. It comprises the synthesis of vinylidine‐terminated polypropylene by using Cp2ZrCl2/MAO as catalyst system and epoxidation of vinylidene polypropylene. The final product was synthesized by carrying out the reaction between epoxy end functionalized polypropylene and 4‐amino‐2,2,6,6‐tetrametyl piperidine. The final product was characterized by using 1H NMR, 13C NMR, and FT‐IR spectra. Functionality was calculated by using vapor phase osmometry and 1H NMR. The solubility and diffusion coefficient of the product were calculated and also its stabilization performance was checked. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1596–1602, 2007

Synthesis, Characterization, and Performance Evaluation of Polymeric HALS in Ethylene‐Propylene‐Diene Terpolymer (EPDM)

A polymeric hindered amine light stabilizer (HALS), wherein the hindered amine functionality was attached to the maleic anhydride graft ethylene‐propylene‐diene terpolymer (EPDM) was synthesized. This involves photoinduced grafting of maleic anhydride groups on unsaturated sites of EPDM, followed by incorporation of amino terminated HALS. The grafting and functionalization reactions were characterized by FTIR and 13C NMR spectroscopy. The surface changes upon degradation are studied by SEM. The photostabilizing efficiency of this polymeric HALS was studied and compared with conventional HALS under accelerated weathering conditions. The HALS grafted EPDM showed significantly improved photostabilizing efficiency.

Identification and quantification of (polymeric) hindered-amine light stabilizers in polymers using pyrolysis–gas chromatography–mass spectrometry and liquid chromatography–ultraviolet absorbance detection–evaporative light scattering detection

Direct analysis of polymers containing polymeric hindered amine light stabilizers (HALS) by using pyrolysis coupled to GC-MS is applied successfully for fast and straightforward identification of these HALS additives. Each of the HALS additives shows different pyrolysis gas chromatograms containing characteristic pyrolysis products. As a result, HALS additives with very similar chemical structures, e.g. Chimassorb 944 and Chimassorb 2020, can be distinguished. A HPLC method with both ultraviolet (UV) and evaporative light scattering detection (ELSD) is developed to quantify the various HALS additives in extracts of polymers. The critical factor of the HPLC method is the use of a basic amine, like n-hexylamine, as a solvent additive to facilitate the elution of HALS additives. The various HALS additives can be distinguished according to retention time and peak shape and by using different detection methods. The suitability of the developed methods is demonstrated by the analytical performance of the HPLC method and the identification and determination of the actual content of HALS additives in polyolefines using pyrolysis GC-MS and HPLC. The HPLC method can also be used for the determination of the specific migration of HALS additives from food contact materials.

Determination of a polymeric hindered amine light stabilizer in polypropylene formulated with magnesium hydroxide flame retardant by reactive thermal desorption-gas chromatography.

A polymeric hindered amine light stabilizer (HALS), Tinuvin 622 (MW [symbol: see text] 4000), in PP materials formulated with a magnesium hydroxide flame retardant was determined by reactive thermal desorption (RTD) gas chromatography (GC). Two kinds of the HALS components that were formed through the RTD in the presence of tetramethylammonium hydroxide [(CH3)4NOH, TMAH] were clearly observed in the chromatograms of the PP samples, with negligible interference from the other additives and the PP substrate. Here, the coexisting flame retardant was proved to affect significantly the RTD process of the occluded HALS. As a result, the recovery of the HALS components in the RTD-GC chromatograms of the PP samples increased with increase in the content of the flame retardant. This enhancement of the HALS recovery is attributed mainly to the preferential exposure of the HALS on the surface of the ground PP sample through the interaction between the polymeric HALS and the flame retardant in the molten PP during kneading. In spite of such a considerable action of the flame retardant, the observed intensities of the characteristic peaks of HALS by RTD-GC showed a good linear relationship with the HALS content in the PP samples with constant content of the flame retardant (50 phr); this relationship could be used as the calibration line for the determination of the polymeric HALS in the PP materials containing the flame retardant.

Structural change of a polymeric hindered amine light stabilizer in polypropylene during UV-irradiation studied by reactive thermal desorption-gas chromatography

The structural changes of a polymeric hindered amine light stabilizer (HALS), Adekastab LA-68LD (MW=1900) added in PP materials during UV-irradiation were investigated by reactive thermal desorption-gas chromatography (RTD-GC) in the presence of tetramethylammonium hydroxide [(CH3)4NOH, TMAH]. Not only the products formed from the residual intact HALS, but also those from its oxidized moiety (nitroxyl radical) were observed on the resulting chromatograms without the use of any troublesome sample pretreatment such as solvent extraction. The changes in the yields of these key products were then examined as a function of UV-exposure time. As a result, it was revealed that the amount of the nitroxyl radical increased in the initial stage of UV-irradiation but then slightly decreased mainly because of further decomposition into the smaller compounds, whereas that of the intact HALS monotonously decreased during exposure.

Synthesis of new polymeric hindered amine light stabilizers: Performance evaluation in styrenic polymers

AbstractPolymeric hindered amine light stabilizers (HALSs), in which the HALS functionality was attached to the terminal isocyanate chain end of poly(styryl‐co‐styryl isocyanate), were synthesized by a two‐step process. First, cinnamoyl azide was prepared and copolymerized with styrene by a free‐radical copolymerization method. Polymeric low‐molecular‐weight and high‐molecular‐weight 2,2,6,6‐tetramethyl‐4‐pipridinol‐graft‐poly(styryl‐co‐styryl isocyanate) and 4‐amino‐2,2,6,6‐tetramethyl piperidine‐graft‐poly(styryl‐co‐styryl isocyanate) were synthesized by a grafting method. The photodegradation and stabilization of different grades of high‐impact polystyrene (HIPS) were studied at 55°C in air at different time intervals, and the photostabilizing efficiency of polymeric HALSs was compared with conventional light stabilizers, such as 2,2,6,6‐tetramethyl‐4‐pipridinol and bis(2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate. Polymeric HALSs showed significant improvements in the photostabilization of HIPS. The solubility and diffusion coefficient of polymeric HALSs were studied. The morphological changes in HIPS caused by photooxidation were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1126–1138, 2003

Highly sensitive determination of a polymeric hindered amine light stabilizer in polypropylene by reactive thermal desorption–gas chromatography using nitrogen-specific detection

Highly sensitive and specific determination of trace amounts of a polymeric hindered amine light stabilizer (HALS) in polypropylene (PP) materials could be established by improving reactive thermal desorption–gas chromatography (RTD–GC) in the presence of an organic alkali, tetramethylammonium hydroxide. By using nitrogen–phosphorus detection, highly selective detection of the HALS-related components was attained. In addition, the use of a polar poly(ethylene glycol) separation column alleviated the adsorption of minor specific pyrolysis products. This modified RTD–GC method allowed the determination of the polymeric HALS ( M r 1900) in PP even for trace concentrations between 100 and 500 ppm, through observing selectively the characteristic products containing a tetramethylpiperidine moiety, which had been impossible to detect under the previous RTD–GC conditions using a non-polar separation column and conventional flame ionization detection.

Light stabilization of metallocene polyolefins

Ultraviolet (UV) stabilization of metallocene polyolefins is examined from a practical and theoretical point of view. First of all, the possibility of using existing stabilizers and stabilizer systems is investigated. To this avail, the compatibility of the stabilizers needs to be checked at the concentrations most commonly used. It is found that, in this respect, there is no fundamental difference between conventional high-pressure polyethylene (PE-LD), linear low-density polyethylene (PE-LLD) and metallocene polyethylene (m-PE). With polypropylene (PP), stabilizer compatibility is generally not so much a problem as with polyethylene (PE). The assessment of the performance of light stabilizers is performed with compression molded films. The results so far available show that the UV absorbers and hindered amine light stabilizers (HALS) examined confer comparable UV stability to PE-LD, PE-LLD and m-PE. Similar results are observed with PP. It is found that the lifetimes obtained on artificial weathering of m-PP and third generation PP are comparable. Furthermore, the synergism between two polymeric HALS that has been observed previously with second and third generation PP is also found with metallocene polyolefins. The experimental laws relating the performance of the HALS to their concentration are deduced from the preliminary data available. It is found that they are the same as those found previously for PP and PE. With PP, UV stability increases linearly with HALS concentration as long as the last is not too high. With m-PE as with PE-LLD, the performance is directly proportional to the square root of the HALS concentration. From these and additional results it is concluded that the degradation and stabilization mechanisms with m-polyolefins are essentially the same as those developed for the previous types of polyethylene and polypropylene.

Synthesis, Characterization and Performance Evaluation of Polymeric Hindered Amine Light Stabilizers in Styrenic Polymers

Styrene/maleic anhydride (SMA) copolymer has been synthesized by a free radical copolymerization method. The polymeric low and high molecular weight 4-amino-2,2,6,6-tetramethyl piperidine-graft-SMA, 2,2,6,6-tetramethyl-4-piperidinol-graft-SMA and 1, 2,2,6,6-pentamethyl-4-piperidinol-graft-SMA have been synthesized by the grafting method. The stabilizing effectiveness of polymeric hindered amine light stabilizers (HALS) has been compared with conventional stabilizers like Tinuvin 770 and Tinuvin 144. The morphological changes of high impact polystyrene (HIPS) with conventional and polymeric HALS has also been studied.

Synthesis, Characterization and Performance Evaluation of Polymeric Hindered Amine Light Stabilizers in Styrenic Polymers

Synthesis, Characterization and Performance Evaluation of Polymeric Hindered Amine Light Stabilizers in Styrenic Polymers

Microwave-assisted extraction by fast sample preparation for the systematic analysis of additives in polyolefins by high-performance liquid chromatography

This paper presents a new approach for complete and systematic analysis of organic additives in polyolefins. The proposed procedure is a convenient combination of sample preparation, performed by microwave-assisted extraction (MAE), and direct chromatographic evaluation of extract by high-performance liquid chromatography coupled with ultraviolet and evaporative light scattering detection. In particular two microwave-assisted processes are reported and discussed: the one-step MAE, useful for additives with low–medium dipolarity (like stabilizers, flame retardant, antistatics, slip and processing agents), and the two-step MAE, useful for additives with either high dipolarity (like organic salts, antigasfading, antiacid, nucleating agent) or high molecular mass (like polymeric hindered amine light stabilizers). Both the proposed processes have been tested on representative additives in five commercially common polymeric matrices, demonstrating their satisfactory analytical results, in terms of repeatability and percentage recoveries, and their good performances, in terms of safety and time/solvent consumption, in comparison with those of traditional extraction methods.

Direct determination of a polymeric hindered amine light stabilizer in polypropylene by thermal desorption–gas chromatography assisted by in-line chemical reaction

A method to determine a polymeric hindered amine light stabilizer (HALS), Adekastab LA-68LD, in polypropylene (PP) was developed on the basis of reactive thermal desorption–gas chromatography (RTD-GC) in the presence of an organic alkali, tetramethylammonium hydroxide [(CH3)4NOH, TMAH]. RTD-GC using 25% TMAH methanol solution allowed the sensitive determination of HALS in PP as methylated fragments on the resulting chromatogram with a 4.8% relative standard deviation without the need for any sample pre-treatment.