改性聚碳酸酯板材的制备及性能研究

采用由丙烯酸类树脂、有机溶剂和紫外线吸收剂(UVA)组成的抗紫外线透明涂层制备改性聚碳酸酯(PC)板材,通过透光率/雾度测定仪、加速老化测试仪、分光光度计研究了涂层对PC板材光学和力学性能的影响。结果表明,抗紫外线涂层与PC板表面具有极佳的附着力,这种涂层具有优异的抗紫外线性能,未涂覆涂层的PC板经紫外光老化120h后黄色指数达到11左右,而涂覆该涂层的PC板的黄色指数仅为1左右,同时该板材能有85%以上的可见光透过率,120h紫外光加速老化后,板材的可见光透过率和力学性能基本保持不变。     

Effects of ultraviolet irradiation treatment on the surface properties and adhesion of moso bamboo (Phyllostachys pubescens)

The poor adhesion of bamboo coatings is a serious issue in the bamboo industry. To overcome this problem it is necessary to modify the actual surface of the bamboo before finishing. A study on the surface properties and adhesion of moso bamboo (Phyllostachys pubescens) were investigated with various UV irradiation conditions including irradiation time and dose using different UV lamps. Two types of wood coatings, i.e., solvent‐borne nitrocellulose (NC) lacquer and waterborne polyurethane (PU) coating, were used in the study, and 180° peel strength and shear strength tests for measuring adhesion of films were conducted. The results revealed that the wettability and the carbonyl group concentration of the bamboo surface were increased. This was particularly apparent for an irradiation time less than 15 s with a mercury UV lamp (H‐lamp), rated at an intensity of 100 W/cm kept at a distance of 15 cm. In all the treatments, the greenish appearance of moso bamboo was retained and the adhesion was improved. Especially, using solvent‐borne NC lacquer finishing, the higher‐dose (under a mercury UV lamp combined with metal halide lamp; H + M‐lamps) irradiated bamboo had the best adhesion, while, for waterborne PU coating, the H‐lamp irradiated one showed the best improvement. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

附着增进剂对塑料涂料在聚碳酸酯底材上应用的影响

聚碳酸酯具有良好的硬度、耐热性与透明性,所以广泛用于塑料相关领域,然而塑料涂料对于PC底材或是ABS/PC复合塑料很容易出现附着不良的问题,尤其是涂膜经过温、湿度环境测试后,附着不良的情况更为严重。试验附着增进剂添加在双组分聚氨酯涂料与紫外光固化涂料中对PC底材的附着效果,结果显示,选择适合的附着增进剂可以显著改善涂料对PC底材的附着效果,并且通过温、湿度环境测试。     

The influence of ageing of epoxy coatings on adhesion of polyurethane topcoats and protective properties of coating systems

The dependence of adhesion and protective properties of coating systems on surface properties of epoxy intermediate coatings, aged and non-aged before an application of polyurethane topcoats, were examined. The intermediate coatings were aged 500 h in UV chamber. The surface free energy and polar groups were estimated after ageing. After applying polyurethane topcoats on aged and non-aged epoxy coatings, resistance to salt spray and thermal shocks were tested as well as internal stresses were measured before and after corrosion tests.The results showed that adhesion in coating systems with polyurethane topcoats applied on aged epoxy coatings depends strongly on the degradation degree of epoxy intermediate coatings and the value of generated internal stresses. Coatings with good adhesion retention in corrosion environments have good protective properties even when temporary blistering has occurred.     

Surface protection of poly(vinyl chloride) by photografting of epoxy–acrylate coatings

UV-curable epoxy–acrylate coatings were used to protect poly(vinyl chloride) against superficial degradation. With α-hydroxy–acetophenone photoinitiators, the crosslinking polymerization develops in the ms time scale; 50% degree conversion is reached after irradiation times of 2.5 ms in a nitrogen atmosphere and 17 ms in air. The adhesion of the coating on to the PVC substrate can be greatly improved by inducing a photochemical grafting process. The best results are obtained by incorporating the photoinitiator into the top layer of the PVC sheet. Highly crosslinked epoxy–acrylate coatings are very stable toward UV radiations and chemical agents like organic solvents and strong acids. By their light-screening effect they provide an excellent protection against photodegradation for light-sensitive polymeric materials.     

Photostabilization of polycarbonate by ZnO coatings

The photostability of bisphenol‐A polycarbonate (PC) can be increased by depositing zinc oxide (ZnO) coatings onto PC films by radiofrequency (rf) magnetron sputtering using an Ar? O₂ plasma. The photoprotective efficiency increases with the thickness of the ZnO layer and also depends on the sputtering parameters (rf power, total pressure, plasma composition), which control the properties of coatings. The increasing thickness of the deposits is correlated with variations of the density, grain size, and composition. PC samples with ZnO coatings were submitted to artificial accelerated ageing (λ > 300 nm) and the extent of the photodegradation was evaluated by infrared and UV–visible spectroscopies. All the deposition parameters were optimized as a function of the results obtained in photoageing and are described in this article. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 380–385, 2005     

Weathering performance of spruce coated with water based acrylic paint modified with TiO2 and clay nanoparticles

This work examines the effect of wood specimens coated with water based acrylic coatings modified with TiO₂ and clay nanoparticles against weathering strain. The long-term durability of the specimens towards climate strain was studied within a relatively short time frame by accelerated climate ageing. The surface changes that occurred as a result of photodegradation of the specimens subjected to accelerated climate exposures were studied using colour measurements and Fourier transform infrared (FTIR) spectroscopy. The results revealed a significant decrease in the intensity of lignin bands attributed to degradation of the lignin component of the wood. However, the intensity of the lignin photodegradation was lower for coated specimens, with slightly lower degradation for the specimens coated with paints modified with TiO₂ and unmodified montmorillonite clay nanoparticles.     

Reversible Switching of Surface Wettability and Water Adhesion on a Polymer Nano-composite Coating

Abstract

Super-hydrophobic polymer/ZnO nano-composite coatings were fabricated by a simple spray-coating method. When the prepared super-hydrophobic coating was directly illuminated by UV light, the surface was fully covered with the hydrophilic groups, which created a state of super-hydrophilic wettability. When UV light illuminated the surface through a mask, the surface maintained its super-hydrophobic property, but the adhesion of a water droplet changed from sliding easily to a highly sticky movement. More importantly, the initial surface wettability and water adhesion can be re-established by heat treatment, and these processes were repeated, with full reproducibility, for a number of cycles.     

Durability enhancement of icephobic fluoropolymer film

An icephobic and superhydrophobic surface was made by the sputtering of fluoropolymer material (PTFE or Teflon^®) on anodized aluminum alloys. The study of this superhydrophobic coating under atmospheric icing conditions showed a 3.5 times reduction of its ice adhesion strength. To evaluate the longevity of such coated surfaces and to assess their potential outdoor applications, their durability was studied after several icing/de-icing cycles. However, these coatings showed weak stability after several icing/de-icing cycles. Plasma argon pretreatment of the anodized aluminum surface was used before sputtering to increase adhesion strength between the anodized aluminum surface and Teflon-like coating. Ice adhesion and contact angle measurements of the pretreated Teflon-like coating indicated clearly that the instability was associated with the low cohesion strength of the Teflon-like film. In order to improve the cohesive strength of the coating, the input power of the discharge was increased during the sputtering process. XPS, SEM, and contact angle analyses showed that an increase in input power renders the Teflon-like coating more stable. The results of ice adhesion measurement showed low variation in ice adhesion strength on such surfaces after 15 icing/de-icing cycles. This coating also showed an excellent stability under UV irradiation and condensation.     

Photodegradation behavior of the polycarbonate/TiO2 composite films under the UV irradiation in ambient air condition

Photocatalytic degradation mechanism of the polycarbonate(PC)/TiO₂ composite films was studied under the ambient air condition in order to investigate the feasibility of the PC/TiO₂ composite as a photodegradable polymer. TiO₂ composition in the PC/TiO₂ composite was changed from 0 wt% to 4 wt%. Photodegradation behaviors of the composite films were compared with that of the pure PC films by performing the weight loss monitoring under UV irradiation, FTIR spectroscopy, color measurement analysis, SEM, and XPS analysis. The weight loss rate of the PC/TiO₂ composite film (33% weight loss after 300 h) with 4 wt% TiO₂ was twice as high as the pure PC films (14% weight loss after 300 h). The increase in the FTIR hydroxyl peak, and carbonyl peak intensity and the yellowing observation during the photodegradation were due to the formation of the photoproducts (aliphatic, aromatic chain‐ketones, aromatic, and OH radical) and the structural modification of polycarbonate. XPS analysis of composite film showed the photodegradation of the polymer surface and TiO₂ particles exposure on the surface of the composite films matrix. POLYM. COMPOS., 36:1462–1468, 2015. © 2014 Society of Plastics Engineers     

Improved adhesion of PMSQ hard coatings on polymer substrates

Various surface treatment methods were investigated to improve the adhesion of abrasion-resistant polymethylsilsesquioxane (PMSQ) coatings on the optical resins. The adhesion of PMSQ films was improved on polymethylmethacrylate (PMMA), polycarbonate (PC), and PC/acrylonitrile butadiene styrene (ABS) by pretreating their surface with O₂ plasma or chromic acid followed by surface grafting with trimethyl ethoxysilane (TMES). After the O₂ plasma and the subsequent TMES treatments, the adhesion of PMSQ coating on PMMA substrate was significantly enhanced by the reduction of the percentage of peeling area from ~100% to <1% in cross cut tests. After the chromic acid and the subsequent TMES treatments of PC and PC/ABS substrates, the adhesion of PMSQ coatings was also significantly enhanced by reducing the percentages of peeling areas from nearly 100% to 50% and <1%, respectively, for PC and PC/ABS. The PMSQ coating might increase the hardness of the polymer by two to three levels.     

Photocurable epoxy/cubic silsesquioxane hybrid materials for polythiourethane: Failure mechanism of adhesion under weathering

A new inorganic–organic hybrid coating containing epoxy‐functionalized cubic silsesquioxane (CSSQ) has been developed, which can be polymerized cationically by UV radiation. This solvent‐free solution can be used as hybrid coating for polythiourethane (PTU) substrate. The surface properties of the coating film were determined by adhesion and scratch resistance. The excellent adhesion of coating films on the substrate was observed at the initial stage before weathering, but deteriorated after exposure to the sunshine. The low viscosity of hybrid coating solution (～ 15 mPa s) leads to fast curing and the formation of hybrid coating film during the photopolymerization reaction. The adhesion failure was evaluated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS) analyses. AFM images showed that the surface is smooth at the initial stage, but a texture surface was developed after weathering. The shrinkage of the hybrid film due to the increase in crosslinking density by postpolymerization would affect the surface roughness after weathering. XPS analysis indicated that the adhesion failure occurred by photodegradation of the PTU substrate during weathering. The weathering resistance was significantly improved by adding UV absorbers, which protected the polymer substrate from the photodegradation. The advantages of the hybrid coating include fast cure speed, solvent‐free formulation, and improved surface properties of the coating film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface degradation and nanoparticle release of a commercial nanosilica/polyurethane coating under UV exposure

Many coating properties such as mechanical, electrical, and ultraviolet (UV) resistance are greatly enhanced by the addition of nanoparticles, which can potentially increase the use of nanocoatings for many outdoor applications. However, because polymers used in all coatings are susceptible to degradation by weathering, nanoparticles in a coating may be brought to the surface and released into the environment during the life cycle of a nanocoating. Therefore, the goal of this study is to investigate the process and mechanism of surface degradation and potential particle release from a commercial nanosilica/polyurethane coating under accelerated UV exposure. Recent research at the National Institute of Standards and Technology (NIST) has shown that the matrix in an epoxy nanocomposite undergoes photodegradation during exposure to UV radiation, resulting in surface accumulation of nanoparticles and subsequent release from the composite. In this study, specimens of a commercial polyurethane (PU) coating, to which a 5 mass% surface-treated silica nanoparticle solution was added, were exposed to well-controlled, accelerated UV environments. The nanocoating surface morphological changes and surface accumulation of nanoparticles as a function of UV exposure were measured, along with chemical change and mass loss using a variety of techniques. Particles from the surface of the coating were collected using a simulated rain process developed at NIST, and the collected runoff specimens were measured using inductively coupled plasma optical emission spectroscopy to determine the amount of silicon released from the nanocoatings. The results demonstrated that the added silica nanoparticle solution decreased the photodegradation rate (i.e., stabilization) of the commercial PU nanocoating. Although the degradation was slower than the previous nanosilica epoxy model system, the degradation of the PU matrix resulted in accumulation of silica nanoparticles on the nanocoating surface and release to the environment by simulated rain. These experimental data are valuable for developing models to predict the long-term release of nanosilica from commercial PU nanocoatings used outdoors and, therefore, are essential for assessing the health and environmental risks during the service life of exterior PU nanocoatings.     

Gloss and degradation of hydroxyl polyacrylic resin/hexamethylene‐1,6‐diisocyanate coatings under ultraviolet and natural‐exposure aging

Reactive coatings of hydroxyl polyacrylic resin (HPAR) with hexamethylene‐1,6‐diisocyanate were carried out under accelerated 313‐nm ultraviolet (UV) aging for 2000 h and under natural exposure in Lhasa, Tibet, for 24 months. With UV irradiation and exposure time, the gloss changes in coatings with HPAR containing 3.0% or less hydroxyl groups decreased exponentially, whereas the gloss decay of coatings with HPAR containing over 4.5% hydroxyl groups decreased linearly. During 254‐nm UV aging, the gloss changes in coatings with HPAR containing 1.4% or less hydroxyl groups decreased as a Gaussian function. The weather resistance of a coating was correlated to the HPAR, UV irradiation, temperature, and humidity. Scanning electron microscopy indicated that there were degradation reactions and that some substance was lost in the matrix polymer during accelerated UV aging; then, uneven surfaces appeared and caused decreased gloss. Accelerated UV aging was faster than natural‐exposure aging, and the aging velocity of 254‐nm UV was 3–5 times faster than that of 313‐nm UV. Through the changes in the gloss, the aging tolerance of a coating could be monitored, and its aging resistance could also be predicted. The dynamic mechanical thermal analysis results showed that the coatings had good properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1271–1278, 2007     

聚碳酸酯材料表面防护涂料的制备及其性能研究

以TEOS(正硅酸乙酯)和MTEOS(甲基三乙氧基硅烷)为水解前驱体,以耐磨助剂、自制附着力促进树脂(PE-1)与自制反应型紫外光吸收剂(RUV-1)为改性剂,采用溶胶-凝胶技术,制备了一种能够满足聚碳酸酯材料表面防护要求的有机-无机杂化涂料。研究了无机组分与有机组分比例,以及耐磨助剂、PE-1和RUV-1用量等对涂料关键性能的影响。结果表明:当n(MTEOS)∶n(TEOS)=2∶1,耐磨助剂用量为1.5%,PE-1用量为3%,RUV-1用量为1%时,涂层的综合性能最佳,涂层经400冲程耐磨试验后的雾度值仅为4.3%,涂层经多项环境试验后的附着力均为5B,涂覆该涂层的聚碳酸酯材料经120 h紫外光辐照后的黄变指数仅为0.65。     

A macroscopically nondestructive method for characterizing surface mechanical properties of polymeric coatings under accelerated weathering

The surface of coatings and plastics is the first target in any degradation process initiated by ultraviolet (UV) radiation or mechanical stress (via scratch and abrasion). Surface damage can lead to changes in optical, morphological, and mechanical properties and can result in pathways for ingress of moisture and corrosive agents. Current test methods for monitoring performance of protective coatings focus on chemical properties and optical properties, such as color and gloss measurements, or invasive tests such as abrasion and cross-cut adhesion. In this study, a macroscopically nondestructive performance protocol using nanoindentation metrology via a well-controlled scratch test was applied to evaluate the scratch resistance and monitor the surface mechanical property changes in a protective coating under accelerated weathering. Polyurethane (PU) coatings with different polyol compositions were chosen for this study. Coating specimens were exposed to high-intensity UV radiation at 55°C and 75% RH conditions. Exposed specimens were removed at specified UV exposure times for surface modulus/hardness and scratch resistance characterization via nanoindentation and scratch test. The effect of polyol type and UV radiation dose on the scratch damage (scratch morphology) was investigated and correlated with the surface hardness and modulus of the materials.     

Enhancing exterior performance of clear coatings through photostabilization of wood. Part 2: coating and weathering performance

Clear-coated boards have not been recommended for use in exterior conditions since irradiation with visible and UV radiation darkens them and photodegrades the lignin in the wooden surface beneath the coating, leading to delamination and subsequent catastrophic coating failure due to the continued action of sun, rain, and biological factors. Many approaches to rectify this problem have been explored. Chemical modification of the surface with hexavalent chromium, reaction with various anhydrides, grafting of UV absorbers, and esterification are among the methods attempted. A second approach has been via the clear coating itself where UV absorbers, antioxidants, and ultrafine titanium and iron oxides have been added. However, these have had limited or no success in stopping photodegradation processes. Since the main cause of photodegradation is photooxidation of lignin in the wooden surface as a consequence of free radical reactions initiated by UV irradiation, the approach taken in the present study, in an attempt to enhance the weathering performance of clear-coated boards outdoors, was to delignify the surfaces of wooden boards and then apply clear coatings to try and retard possible photodegradation. Two different pretreatments were used. Firstly, chemical surface delignification with a peracetic acid treatment created a partial delignification to a depth of 2–3 mm while still retaining the structural integrity of the surface. Secondly, a preweathering treatment, which resulted in a 100-μm-deep delignification zone, was compared. The coatings applied to the exposure surface of the pretreated boards were either polyurethane or an acrylic varnish. The clear-coated boards were exposed to exterior and accelerated weathering regimes for 3 years or 3000 h, respectively. Pretreated coated boards did not darken and yellow on exposure but untreated coated boards did. However, despite apparently arresting photodegradative processes on board surfaces, there were no significant gains in the performance ratings of coated pretreated boards over those of coated untreated control boards. Explanations for this involve the effectiveness of design factors incorporated into boards for exposure trials. These factors were the fungicidal dipping of boards before coating, precoating the exposure surface with a reactive primer, and applying a full polyurethane system to the back side and edges of boards. Both pretreatments resulted in clear-coated board surfaces that performed very similarly on exposure outperforming systems reported previously. It was surprising to observe that the preweathering treatment, which resulted in a 100-μm-deep delignification zone, performed as effectively as the chemically pretreated boards with 2- to 3-mm treatment zone. However, preweathered surfaces had lost all lignin in the middle lamella and there was cell separation, whereas in peracetic acid-treated boards, there was more or less complete lignin removal from the cell corner middle lamella only and partial lignin removal from other cell wall regions. Furthermore, it is anticipated that refinements in treatment methods and coating formulations will bring desired benefits and future work should focus in this area.     

Effect of TiO2 pigment type on the UV degradation of filled coatings

The objective of this study was to investigate the effect of the photoreactivity of titanium dioxide (TiO₂) pigments on the photodegradation of polymeric coatings used in exterior applications. Two polymer matrices, an amine-cured epoxy (EP) and an acrylic urethane (AU), containing three types of TiO₂ pigments, classified by different levels of photoreactivity, were studied. Specimens were exposed on an ultraviolet (UV) weathering chamber, the Simulated Photodegradation by High Energy Radiant Exposure device at the National Institute of Standards and Technology. Two exposure conditions were used: ambient, dry condition [25°C and 0% relative humidity (RH)] and high temperature, wet condition (55°C and 75% RH), which is similar to more severe outdoor exposures. The physical and chemical degradations of the filled coatings were monitored at periodic intervals using a combination of laser scanning confocal microscopy (LSCM) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Progression of degradation on the coating surfaces was characterized by LSCM in terms of changes in surface roughness and morphology, pigment agglomerate size, and the occurrence of pits or holes in the coatings. The observed physical changes were correlated to the chemical changes measured by ATR-FTIR as a function of UV exposure time. Both EP and AU systems showed less degradation in terms of surface roughness and morphological changes under the dry conditions compared to the wet exposure conditions. It was observed that both the pigment type (and hence photoreactivity) and particle dispersion strongly affected the degradation of both EP and AU systems.     

水性聚偏氟乙烯型反射隔热涂层的耐久性研究

研究了在酸、碱、盐和 UV辐照等环境作用下水性聚偏氟乙烯型（ PVDF）反射隔热涂层性 能的时变规律。使用扫描电镜（ SEM）和能谱分析表征了涂层微观形貌及断面中的氟元素分布， 对涂层在经各类环境作用前后的明度、光泽、色差、力学性能和反射隔热性能进行了测试，并使用 ATR-FTIR对表面涂层的官能团变化进行了分析。结果表明：氟元素在涂层树脂基体中的垂向分布较均匀； 56 d UV处理会提升涂层光泽；经酸、盐和 UV处理后，涂层明度未见明显变化且色差较小，涂层断裂伸长率降低且抗拉强度提升，最高达 8.4 MPa，反射隔热性能指标未见明显变化；碱处理后的涂层出现明显的色差和明度下降，涂层变脆且抗拉强度下降，同时太阳光反射比由 0.70降至 0.65。ATR-FTIR分析结果表明：涂层的耐酸、盐和 UV能力较强，但在碱性条件下存在含氟组分的降解破坏情况。     

Transparent ZnO-Y2O3 coatings: Bactericidal effect in the lighting and in the darkness

The article presents a study of transparent bactericidal oxide coatings prepared on a glass surface by using the solutions of a polyvinylpyrrolidone and zinc and yttrium nitrates. Mixed oxide coatings were studied by spectroscopic and luminescent methods, SEM, XRD and DSC –TG analysis. Coating antibacterial activities against the bacteria Staphylococcus aureus ATCC 209Pand Escherichia coli ATCC 25922 were tested in the lighting and in the darkness. Prepared mixed oxide coatings are transparent in the visible spectral range, able to generate singlet oxygen under UV irradiation and demonstrate antibacterial effect as at the light so at the dark. It was shown that the transparency of the coating materials in the UV spectral range increases with the ZnO content reduction in mixed oxide coatings. Mixed oxide coating containing about 90% of zinc oxide demonstrates the highest bactericidal properties.