SECM study of steel corrosion under scratched microencapsulated epoxy resin

Scratch tests were performed on epoxy coated steel samples with and without microcapsulated linseed oil, known to develop a polymerized protective layer after having been released from the capsules at the damaged sites. The scanning electrochemical microscope has been applied to monitor the protection efficiency of this self-healing coating in aqueous acidic solution. In the proximity of the local damage, both the anodic metal dissolution and the cathodic oxygen reduction showed that the coating with microcapsules substantially and spontaneously decreased the rate of corrosion proving the self-repair concept of the coating. Electrochemical impedance measurements underline the protective effect of the coating as well.     

Effect of self-etching ceramic primer on bond strength of zirconia-reinforced lithium silicate ceramics

Abstract

This study evaluated the effect of self-etching ceramic primer (SECP) on shear bond strength (SBS) of zirconia-reinforced lithium silicate (ZLS) ceramics. Two hundred and seventy block-specimens of two types of ZLS ceramics and one type of lithium disilicate (LS) ceramics were prepared. Ninety blocks of each material were divided into three groups (n?=?30), namely group 1: no surface treatment (control), group 2: hydrofluoric acid (HF), silane-based primer (S), and group 3: SECP. Resin cement was applied, and light-cured for build-up. Shear bond strength (SBS) test was used. Half of the bonded specimens (n?=?15) were tested after storage in distilled water for 24?h, whereas the other half were tested after 5000 thermo-cycles. The failure modes were evaluated using scanning electron microscope (SEM). The SBS values for samples treated with SECP and HF?+?S within the respective materials were statistically comparable (p?>?0.05). Thermocycling significantly reduced the SBS (p?<?0.05) for all ceramic materials in groups 2 and 3. Mixed failure followed by adhesive failure were the most common failure modes in groups 2 and 3, whereas pretest failure was only detected in group 1. Considering the limitations of the study, with respect to in vitro bond strength, the SECP is an alternative for the conditioning of internal surface of glass ceramics.     

本器底漆用气干型不饱和聚酯树脂的研制

本文主要介绍气干型不饱和聚酯树脂的合成配方及工艺,探讨原料对树脂性能的影响,并阐述其在木器底漆中的应用。     

醇溶型无机锌车间底漆的电化学行为研究

使用电化学方法对2种不同的醇溶型无机锌车间底漆进行了研究,结合浸泡以及盐雾的实验结果,发现2种车间底漆中锌含量对阴极保护时效有影响,但不是决定车间底漆防锈能力的唯一因素,锌含量与防锈颜料对于车间底漆的防锈性能有协同效果。其中,锌粉在早期提供阴极保护的作用,而防锈颜料在后期对基底提供防锈保护。对于锌粉含量相对较高的车间底漆,锌粉并不是从一开始就全部参加阴极保护作用,而是一部分具有激活潜力的锌粉在另一部分锌粉率先反应之后才由“未激活状态”转变为“激活状态”进而提供阴极保护的作用。     

随弹小底火测试装置设计和试验

设计了随弹小底火性能测试装置,解决了无法进行定装式炮弹压装小底火性能测试的问题.测试和分析结果表明随弹小底火性能随储存时间而呈规律性变化,对炮弹内弹道性能有明显影响.为开展库存弹药的储存可靠性研究和事故分析提供了又一途径.     

Molecular Structure of Polymer/Metal Interphases

The molecular structure of interphases in aluminum/epoxy and steel/epoxy adhesive joints was characterized using infrared spectroscopy. In one series of experiments, adhesive joints were prepared by curing beams of epoxy against aluminum or steel substrates. When the joints were cooled to room temperature, the residual stresses were sufficient for crack propagation along the interface. The adhesive and substrate failure surfaces were then analyzed with reflection-absorption infrared spectroscopy (RAIR), attenuated total reflection infrared spectroscopy (ATR) and X-ray photo-electron spectroscopy (XPS). When an epoxy/anhydride adhesive was cured against aluminum substrates primed with an aminosilane coupling agent, amide and imide groups were formed in the interphase. Chemical reaction between the primary amine of the primer and the anhydride of the curing agent precluded chemical bridge formation between the primer and adhesive. Metal cations from the 2024 aluminum substrate reacted with the anhydride to form carboxylate salts on the surface. When an epoxy/tertiary amine adhesive was cured against steel substrates, evidence of oxidation of the primary amine to imine was observed in the interphase.     

A Water Soluble Hydrated Metal Oxide primer for Adhesively Bonded Joints

Weight saving and manufacturing cost benefits have led to the increase in use of adhesively-bonded structures in the automotive, aerospace and marine industries. In order to be a viable alternative to, for example, metal fasteners, these adhesive bonds should maintain the strength typical of conventional fastener systems. In many applications, the bonds are put under a variety of environmental and mechanical stresses. For example, frequently these bonds are exposed over long periods of time to wet environments which can result in a loss of bond strength. The loss of strength can result from the extension of cracks and other deformations that occur in the adhesive or metal oxide which are accelerated by the moist environment. As a result of this deficiency, extensive research and development efforts have been undertaken to define methods and identify materials which improve bonded joint performance in humid conditions. For example, it is known that surface preparation is important in the bonding of aluminum and titanium, and cleanliness in the bonding of ceramic articles. Thus, it is essential that, before bonding, the adherend is cleaned and chemically pretreated to produce a surface which in combination with the adhesive develops the bond strengths which meet application requirements. The normal procedure after surface treatment is to apply a corrosion-inhibiting primer by a spray technique for surface protection prior to bonding and to insure resin penetration into the oxide structure which provides improved environmental resistance. A major drawback of spray application is the large volume of organic solvent (normally MEK) emitted to the atmosphere. A successful alternative is the recently-developed electrodeposited primer by Northrup Corp., which consists of water solubilized primer particles which migrate in an electric field to a conductive work piece where they are deposited in a dense, continuous coating.¹ The primer was developed for use with 121°C (250°F) curing epoxy adhesives. An Air Force sponsored contract is currently under way, the objective of which is to develop an electrodeposited water-based primer for use with 177°C (350°F) curing epoxy systems.² A water-based epoxy primer system for application using the more conventional spray techniques has also been decribed.³     

水性木器涂料在松木涂装中的应用

介绍了常用松木的特点、种类,水性木器涂料在松木涂装中的涂装类型及特点。并简述了用水性木器涂料进行松木涂装时的优缺点,以及松木的除油脂及施工水性封闭底漆的重要性。     

高性能通用型防腐底漆配方设计及应用

介绍了一种可直接在带锈、带水(湿气)、带油等杂质表面上进行涂装的高性能通用型低处理表面防腐底漆及其有关性能。试验证明:该底漆施工性能好,与含有少量锈、水(湿气)、油和旧涂层等杂质的表面附着力好,其涂层耐介质性能优异,并具有长效的防腐性能。