Investigating the degradation resistance of silicone-acrylate containing automotive clearcoats exposed to bird droppings

This work reports preparation of acrylic/melamine based clearcoats containing various loads of a reactive polysiloxane additive. The additive was incorporated into the clearcoat formulations up to 8 wt% to enhance its resistance against bird droppings. Contact angle measurements, ATR spectroscopy, energy dispersive X-ray analysis, appearance measurements together with different microscopic techniques were utilized to reveal the effects of additive on the properties of the coating prior and after exposure to pancreatin, the synthetic equivalent of natural bird droppings. Appearance measurements, as well as optical microscope images obviously indicated that the additive improved the clearcoats resistance against pancreatin. Results revealed that surface free energy of the films was reduced in the presence of additive. It was also found that at high concentrations of additive, a significant part of it remained in the bulk, forming a second phase. This resulted in a lack of sufficient reactive groups and lead to an under-cure state at the clearcoat surface.     

An evaluation of an automotive clear coat performance exposed to bird droppings under different testing approaches

In this study, the effects of two types of biological materials, i.e. natural bird droppings and pancreatin, on properties of an automotive acrylic melamine clear coat were studied. In addition, two different testing approaches including pre-aging and post-aging were utilized to investigate the biological resistance. To this end, effects of these biological materials on clear coat surface properties and appearance were investigated by different techniques including digital camera, SEM, AFM, optical microscopy and a gloss meter. In addition the mechanical properties of clear coats were evaluated by micro Vickers measurement and DMTA analysis. For further investigation FTIR analysis was utilized to have a more understanding of the failure mechanism.Results showed that the biological materials have an extremely vital effect on the appearance of the coatings. Decreasing of t_g and hardness of the films made by pancreatin and bird droppings were observed and were attributed to the chemical alterations as proved by FTIR analysis. It was also found that the biological degradation occurred on the samples experienced the post-aged testing method was more severe than the samples exposed to pre-aged testing. On the other hands, although bird droppings and pancreatin revealed a same failure mechanism, the effect of the former was more severe. In addition, it has been shown that the enzymatic structure of biological materials is responsible for the catalyzing the hydrolytic degradation of clear coat at neutral pH. Therefore, the biological degradation mechanism may be regarded as an enzymatically induced hydrolytic cleavage.     

Role of surface active additives on reduction of surface free energy and enhancing the mechanical Attributes of easy-to-clean automotive clearcoats: Investigating resistance against simulated tree gum

The objective of this work is enhancing the clearcoat resistance against simulated tree gum (Arabic gum) using surface active additives including hydroxyl-functional polydimethyl siloxane (PDMS) and hydroxyl-functional silicone polyacrylate which are able to reduce gum adhesion to the clearcoat surface by reducing its surface free energy and work of adhesion. Using a contact angle measuring device, the surface free energy, contact angle and work of adhesion were obtained. The mechanical and structural properties of the clearcoats were studied by tensile test, dynamic mechanical thermal analysis (DMTA) and Fourier transform Infrared spectroscopy (FT-IR). Results showed that both additives enhanced the clearcoat easy-to-clean properties and reduced work of adhesion and surface free energy. The decrease in surface free energy and work of adhesion was more pronounced in presence of hydroxyl-functional polydimethyl siloxane. It was found that polydimethyl siloxane could produce contact angles much greater than silicone polyacrylate. Both additives increased clearcoat cross-linking density and toughness by participating in curing reaction. Results showed that the increase in cross-linking density and toughness was more effective when polydimethyl siloxane based additive was used. Results also revealed that additives could significantly improved the clearcoat resistance against Arabic gum by reducing gum adhesion to the surface. Both number of cracks and etched areas were reduced in presence of the additives especially in presence of polydimethyl siloxane. Both the chemical structure and functionality of the additives were found influential parameters which could alter the clearcoat surface cleanability and biological resistance against simulated tree gum.     

不同添加剂对镁质浇注料性能的影响

以电熔镁砂和高纯镁砂为主要原料制备了镁质浇注料,研究了不同添加剂对镁质浇注料性能的影响。研究结果表明,5种添加剂中,加入氧化铝微粉的镁质浇注料经1 100℃和1 500℃烧后的体积密度最大,浇注料基质中形成的方镁石/镁铝尖晶石复相结构有利于提高试样的抗热震性。加入氧化铬、铝铬渣和焦宝石的镁质浇注料,其抗热震性均高于未加入添加剂的镁质浇注料的该项性能。     

Mode of action of surface active slip and antiblocking additives

The surface concentration and structure of oleamide slip additive and stearamide antiblocking additive commonly used in polyolefins has been investigated by X-ray photoelectron spectroscopy. The oleamide has been found to form a complete continuous thick layer on the surface of the polymer, whereas the stearamide results in an incomplete discontinuous layer of lesser thickness. Such surface structures are intuitively consistent with the observed action of these molecules in practice. Migration rates of the two long chain amides were found to differ, with the oleamide appearing at the surface at a rate about three time greater than the stearamide. Time dependent surface oxidation of the oleamide additive was observed. It is speculated that the unsaturation within the oleamide molecule is the site of oxidation.     

Preparation of surface energy controlled automotive clearcoats loaded with functional silicon additives: Studying the resistance against tree gum attack

The aim of this study is enhancing an automotive clearcoat easy-to-clean property against simulated tree gum (Arabic gum) using hydroxyl-functional silicone polyacrylate additives having different hydroxyl contents. The clearcoat surface, mechanical and chemical properties were studied using a contact angle measuring device, dynamic mechanical thermal analysis (DMTA) and Fourier Transform Infrared spectroscopy (FT-IR) respectively. It was found that additive with lower hydroxyl content gave rise to better easy-to-clean properties of the clearcoat against Arabic gum. This additive also resulted in lower contact angles and higher cross-linking density, tensile stress and work of break of the clearcoat.     

表面活性剂对纳米羟基磷灰石制备影响的研究

纳米羟基磷灰石(nano-HAP)的制备工艺在有效控制晶形、尺寸、稳定性等方面尚不成熟,阻碍了它的应用发展。采用化学沉淀法,以Ca(NO3)2.4H2O和(NH4)2HPO4为主要原料合成nano-HAP,在一定工艺条件下通过添加表面活性剂改善制备效果,用XRD、TEM、IR等检测手段表征产物,研究了聚乙二醇-400、聚乙二醇-6000、聚乙烯醇和吐温-80等4种表面活性剂对产物的形貌、粒径、结晶度、分散性等的影响。结果表明:在实验条件下,添加聚乙二醇-400的制备效果最佳,可得平均粒径约为20 nm、结晶度高、稳定性好的高纯nano-HAP针状晶体。     

不同添加剂对自硫化CSM/XNBR共混物性能的影响

在没有任何硫化剂的条件下,氯磺化聚乙烯（ＣＳＭ）和羧基丁腈橡胶（ＸＮＢＲ）的共混物（质量比１∶１）能在１８５℃×６０ｍｉｎ下模压硫化。溶胀分析、凝胶测定、硫化曲线及红外谱图分析证实了ＣＳＭ中的氯磺酰基和ＸＮＢＲ中的羧基之间发生了交联反应。共混体系能用５０份炭黑增强,３０份氯化石蜡增塑。加入ＣＳＭ的稳定剂增加了共混硫化胶的凝胶质量分数。碱性物质能大幅度提高自硫化ＣＳＭ／ＸＮＢＲ共混物的强度。共混物的耐热氧老化性能尚待提高。     

Effects of surface active agents on fall velocities of drops

Terminal velocities of drops undergoing mass transfer were measured in nine systems containing anionic, cationic, or nonionic surfactants. Variables included drop size, formation time, number of parallel droplet-streams, and surfactant concentration. Results were interpreted in terms of visually observed internal circulation and oscillation of the drops and some success was achieved in correlating the data obtained.     

Effects of surface active compounds on thermal denaturation of DNA

The interaction of surface active compounds (including N-lauroyl amino acids) withself thymus DNA in aqueous solutions has been studied by measurements of the melting temperature of the DNA. The results suggest that the surface active nature of these additives is not the primary factor governing the interaction with DNA, but their molecular structure is very important in the interaction.     

Lipase purification by various techniques and its thermostabilization in presence of surface active additives

Crude porcine pancreatic lipase was purified by removing water-insoluble impurities (residual lipid material) associated with it by a conventional method, using hydrotropic additives and by liquid coacervate extraction. Maximum yield with good recovery of activity was obtained when hydrotropes were used to separate the associated lipids from lipase. The thermostability of the enzyme was also checked in the solutions of additives such as sodium butyl monoglycol sulfate (Na-BMGS), proline and Triton X-114. In Na-BMGS solutions above a concentration of 0·2 mol dm⁻³ the lipase activity decreased beyond 50°C whereas in 1 mol dm⁻³ proline solution it was retained even at 80°C, showing a good thermostabilizing effect. However, in the presence of Triton X-114 the enzyme was completely inactivated with increase in temperature. © 1998 SCI.     

钙基添加剂对不同煤种解耦燃烧下硫释放的影响

煤燃烧后排放的硫氧化物导致的环境污染问题已经引起人们的日益关注。基于一段式和两段式卧式炉,本文探究在传统燃烧和解耦燃烧条件下,温度、煤种以及CaO对燃煤释放SO₂规律的影响。试验结果表明：不同煤种的SO₂释放规律存在差异。随着温度的升高,不同煤种燃烧SO₂的释放量均不断增加,硫的动态析出曲线逐渐由单峰分布转化为双峰分布。传统燃烧模式下,添加的CaO对烟煤、无烟煤和褐煤脱硫效率可以达到70%以上,高氯煤脱硫效率则较低,仅有12.09%～20.45%;随温度升高,烟煤、褐煤和高氯煤的脱硫效率呈现先略微下降,后升高再下降的趋势,烟煤脱硫效率则逐渐降低。解耦燃烧模式下,CaO对烟煤、无烟煤脱硫效率在42.35%～76.23%,褐煤在21.35%～52.63%,高氯煤脱硫效率仍然较低,在8.93%～10.57%;随温度升高,烟煤、褐煤和高氯煤的脱硫效率呈现先增加后降低的趋势,烟煤脱硫效率逐渐降低。解耦燃烧模式下,不同煤种SO₂的总释放量大于传统燃烧模式,添加CaO后脱硫效率小于传统燃烧模式。     

The effect of surface active additives on the partitioning of proteins and enzymes in aqueous two-phase systems

The effect of cationic and anionic surface active additives on the partitioning of proteins has been studied. The surface active agents interact with proteins electrostatically and also hydrophobically. The increased hydrophobicity of the proteins because of association with surfactants is responsible for the changes in the partition coefficients and in some cases for precipitation of the proteins. Specific interactions also exist between mildly surface active amino acids and proteins.     

不同混合材掺量对低碱水泥适应性的试验研究

对不同种类及掺量的混合材对低碱水泥流动洼能进行试验研究，结果为：低碱硅酸盐水泥中掺入矿渣粉、粉煤灰、石灰石等混合材有利于改善浆体流动性能，目双掺效果较单掺好；外加剂掺入量对流动性能的改善随着掺量的增加而增加，但掺入量应适宜、经济；石灰石为非活洼混合材，本试验研究结果表明它能显著增大水泥流动性且保持较小的经时损失，但其掺量不宜过大。     

The influence of basecoat pigmentation on chemical structure and surface topology of automotive clearcoats during weathering

The present study aims at elucidating the effect of basecoat pigmentation on the chemical structure and surface topology of its attached clearcoat during weathering exposure. Two extremes of differently behaviored basecoat pigmentations (i.e. silver and black) were chosen. Different analyses such as FTIR, ATR, surface energy measurements and AFM were carried out on such coatings after they were subjected to accelerated weathering conditions. It was found that the black basecoat procured more post-curing reactions to the attached clearcoat at initial weathering times, while the silver basecoat induced higher degrees of photodegradations during the whole time of weathering. Such inductions were attributed to the inherent absorptive or reflective behavior of the black or the silver basecoats toward incident radiation.     

Effects of different additives on bimetallic Au-Pt nanoparticles electrodeposited onto indium tin oxide electrodes

Bimetallic Au-Pt nanoparticles (Au-Pt_NPs) have been synthesized using an electrochemical reduction approach. The effects of the addition of different additives in the electrodeposition bath namely KI, 1-nonanesulfonic acid sodium salt and Triton X-100 have been investigated. The structural characterization of the bimetallic nanoparticles has been carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy, X-ray diffraction (XRD) and cyclic voltammetry (CV). The Au-Pt_NPs prepared in the presence of KI and Triton X-100 characterized by a relatively narrow size distribution as well as a higher particle density and surface coverage whereas no changes in the morphology were observed. These results suggest a dependence of the size and distribution of the bimetallic nanoparticles from the type and concentration of the additives employed.     

不同炭质添加剂对块状活性炭强度和吸附性能的影响

为制备可净化空气的室内装饰性用块状活性炭,选择自制粉状活性炭(PAC)为吸附基体,羧甲基纤维素(CMC)为黏结剂,碳酸氢钠为发泡剂,考察生石油焦、煅后石油焦和竹炭3种炭质添加剂(CA)对块状活性炭强度和吸附性能的影响.结果表明:煅后焦替换自制粉状活性炭制备的试样机械性能提升最显著,自制粉状活性炭和煅后焦以1:1的比例作...     

添加剂对醇醚糖苷表面性能的影响

以醇醚糖苷AEG050为原料,研究了其自身表面性能及不同添加剂对其表面性能的影响。结果表明,在25℃下AEG050的临界胶束浓度cmc=44.5 mg/L,最低表面张力γ_(cmc)=29.4 m N/m,具有较强的抗硬水能力。随着NaCl和Na_2SO_4两种无机盐浓度的增加,AEG050的表面活性增强。在较低浓度的一元醇溶液中,AEG050的表面活性增强,但当醇浓度较高时,其表面活性下降。AEG050与其他表面活性剂复配有一定的增效作用,尤其是与十六烷基三甲基溴化铵形成的复配体系,其cmc增效34.2%,γ_(cmc)增效4.1%。     

The development and stability of surface layers on concrete exposed to sea-water

Concrete exposed to sea-water may develop a surface skin causing a marked reduction in permeability. The skin typically consists of a layer of brucite (magnesium hydroxide) of aroun 30 μm thickness, overlain by a thicker, but more slowly developing, layer of aragonite (calcium carbonate). The aragonite may convert to calcite in an aqueous environment free from magnesium ion.The degree of saturation of sea-water with aragonite or brucite is primarily a function of its pH value. Uncontaminated sea-water has a pH within the range 7.8 to 8.3 and is supersaturated with aragonite at pH values greater than around 8.1. For good correlation of laboratory tests with natural exposure conditions appreciable increases in pH should therefore be prevented. Temperature variations may have a significant effect on layer precipitation, but the range of pressures encountered by offshore structures has negligible effect. Organic compounds present in sea-water may inhibit precipitation.