Recrystallization of silicone release coatings

Summary The degrees of recrystallizability of silicone release coatings with different crosslink densities have been determined via monitoring the recrystallization peak of the temperature scan on the Rheometrics-RMS-800 Spectrometer and DSC. As the crosslink density of the release coating increases, the recrystallization peak of silicone diminishes sharply indicative of the increasing constrains imposed by the high crosslink density which reduces the recrystallizability of the silicone. In addition, Tg of the silicone also increases, together with a lower recrystallization and melting temperatures.     

The network structure of silicone release coatings

Silicone release coatings are used by the pressure-sensitive adhesive industry for labeling applications. A background discussion of silicone release coatings is presented. Methodology for determining the network structure of photolytically cured systems prepared by the cationic ring opening polymerization of an epoxy silicone fluid is described. Under typical polymerization conditions, these networks contain no unreached epoxides and have very low degrees of polymerization (D _p), indicating that termination is competitive with propagation. A method has also been developed to determine the network structure of thermally cured systems prepared by the platinum-catalyzed hydrosilylation of silicone vinyl compounds with silicone hydrides. The nature of the cross-links and the types of residual functionality have been determined and the systems have been shown to undergo a postcure.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

The release behavior of silicone coatings with a thickness gradient

Silicone coatings are being investigated for their foul release properties and durability in application to prevent fouling on ship hulls. To date, studies have focused on coatings with uniform thickness. These studies have shown that their release behavior follow a model presented by Kendall (1971). In that, the force required to remove pseudobarnacles, modeled as epoxy studs, from thin silicone coatings decreases as the thickness increases. The two types of release mechanisms observed were void formation and edge peeling.

However, coatings on ships’ hulls may contain areas where the coating is not uniform but may have a wavy pattern to it. In the present study, pull-off tests were performed in order to study the release behavior of epoxy from clear silicone coatings with a thickness gradient on glass substrates. The four types of release behavior observed were void formation, peeling, mixed mode of void formation then peeling, and mixed mode of fingering then peeling. The type of mixed mode release was dependent on the average thickness and thickness gradient. For samples undergoing mixed mode release, the thinner coatings had small multiple void formations, whereas the thicker coatings had a fingering decohesion pattern near the edge before peeling. For most of the samples tested, separation of the epoxy from the coating started mostly on the thin side of the coating and then proceeded to the thick side. An equivalence length parameter was also introduced that distinguishes the three modes of release involving peeling.     

有机硅涂料的剖析

采用现代化分析手段———气相色谱 -质谱 (GC -MS)、红外光谱 (IR) ,分析出有机硅涂料的主要成分 ,并对其所用有机硅类型和偶联剂进行定性。     

Application of the dynamic EIS to investigation of transport within organic coatings

The paper presents results of an investigation on rapid degradation of organic coating using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). For 60 s, polyvinyl coating has been subjected to the impact of 0.01 M solution of tetraethylammonium tetrafluoroborate in methylene chloride. During that time instantaneous impedance spectra have been determined allowing tracing the dynamics of a degradation process. Usefulness of the DEIS technique in the investigation of non-stationary phenomena has been proved in the field of coating research.     

涂料用硅树脂的开发动向

本文主要介绍硅树脂涂料的最近开发动向.     

Comparison of drag characteristics of self-polishing co-polymers and silicone foul release coatings: A study of wettability and surface roughness

An experimental study has been carried out to evaluate the drag characteristics of different self-polishing co-polymers (SPC) (tin based and tin-free) and a silicone foul release (FR) coating. Drag measurements have been performed on a smooth aluminum cylinder connected to a rotor device. Various coatings on cylinders were examined and differential length technique was also used to avoid the end effects during rotation. Surface energy of the coated samples was determined using static contact angle measurement. Characteristic roughness measurements of the coated surfaces were evaluated with atomic force microscopy (AFM) technique.Drag measurements showed that the frictional resistance of the FR coated cylinders was lower than that of SPC coated samples.Contact angle results showed that the critical surface tension and its polar component for silicone FR coating are less than SPC coatings. This prevents firm adhesion of fouling organisms on underwater hulls.AFM studies revealed a lower surface roughness for silicone FR coating as compared to SPC coatings. Also, its surface texture is considerably different from SPC coatings.It can be concluded that the drag characteristics of a surface are affected by its free energy and roughness parameters.     

Comparison of drag characteristics of self-polishing co-polymers and silicone foul release coatings: A study of wettability and surface roughness

An experimental study has been carried out to evaluate the drag characteristics of different self-polishing co-polymers (SPC) (tin based and tin-free) and a silicone foul release (FR) coating. Drag measurements have been performed on a smooth aluminum cylinder connected to a rotor device. Various coatings on cylinders were examined and differential length technique was also used to avoid the end effects during rotation. Surface energy of the coated samples was determined using static contact angle measurement. Characteristic roughness measurements of the coated surfaces were evaluated with atomic force microscopy (AFM) technique.

Drag measurements showed that the frictional resistance of the FR coated cylinders was lower than that of SPC coated samples.

Contact angle results showed that the critical surface tension and its polar component for silicone FR coating are less than SPC coatings. This prevents firm adhesion of fouling organisms on underwater hulls.

AFM studies revealed a lower surface roughness for silicone FR coating as compared to SPC coatings. Also, its surface texture is considerably different from SPC coatings.

It can be concluded that the drag characteristics of a surface are affected by its free energy and roughness parameters.     

Mobility and distribution of silicone additives in coatings; a spectroscopic study

The concentration of four prepared silicone/poly(ether) additives at the film-air (F-A) and film-substrate (F-S) interfaces of films prepared on glass and poly(ethylene) substrates is characterized via quantitative attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy. Three different coating systems, an acrylic/melamine solvent based system, an acrylic/isocyanate solvent based system, and an aqueous poly(urethane) suspension, were examined. It is found that the nature of the substrate, the mechanism of film formation, and the inherent coating/additive compatibility are all factors which may significantly influence additive behavior. Also the acrylic/melamine system generally reveals a slight degree of enrichment of both additive components to the F-A interface, but the acrylic/isocyanate system exhibits a more pronounced concentration gradient due to a lesser degree of compatibility. In contrast, the water-based poly(urethane) exhibits a more complex behavior, with the poly(ether) component revealing significant enrichment to the F-A interface, and the siloxane component exhibiting a decreased concentration as the interface is approached. Here, the mechanism of film formation involves a water flux passing out of the film which may serve to transport the water soluble poly(ether) components to the F-A interface. At the F-S interface, it is demonstrated that the nature of the substrate may influence additive behavior, and it is found that the concentration of the more polar poly(ether) components generally exhibits a lesser degree of enrichment to a poly(ethylene) substrate, relative to glass.     

A study on the elastic modulus of silicone duplex or bi-layer coatings using micro-indentation

A Fischerscope continuous microindenter with a spherical indenter was used to obtain maximum indentation load and depth data for a 2.2 mm sheet of RTV11 (a silicone elastomer), a 1.6 mm sheet of J501 (an elastomer containing 60% silicone and 40% butyl acrylate styrene) as well as six duplex elastomeric coatings. The duplex coatings consisted of RTV11 top coat and J501 bond coat. The Waters’s empirical relationship was used to determine the modulus of elasticity E for the RTV11 and J501 sheets. The Waters’s relationship was then used to determine the equivalent modulus, E_c, for duplex coatings from maximum indentation load versus elastic indentation depth data. The values of E_c as determined from the Waters’s model (and experimental data) were in good agreement with the values obtained by an equivalent stiffness method. By being able to determine E_c from the equivalent stiffness method and using this value in the Waters’s model, one may determine the load versus elastic depth of indentation for duplex coatings.     

有机硅树脂在粉末涂料中的改性作用及应用进展

综述了近年来国内外有机硅树脂在粉末涂料中的应用研究进展。讨论了有机硅树脂与有机树脂通过共混、化学结合作为粉末涂料基材以及互为固化剂等不同改性方式的特点。有机硅组分的引入可以改善和提高粉末涂料涂膜性能 ,特别是耐候性及耐热性能。展望了有机硅改性树脂在粉末涂料中的应用和发展前景。     

A new class of silicone resins for coatings

A new class of silicone has been developed for coatings or as coating additives. Cycloaliphatic silane monomers were prepared and reacted into more easily handled cyclic oligomers. These cyclic oligomers were ring-opened into siloxane polymers. The polymers were functionalized with a variety of groups, including: amino, glycidyl epoxide, cyclohexene epoxide, acrylic, and alkoxysilane. The cycloaliphatic silicones have been designed for a number of different curing conditions: (1) ambient temperature-cure (amino and glycidyl epoxide), (2) cationic ultraviolet (UV)-cure (cyclohexene epoxide), (3) radical UV-cure (acrylic), and (4) moisture-cure (alkoxysilane). The end usages thus far have been focused on silicone coatings; however, usage as coating additives will be a focus for future research. The cycloaliphatic silicone has been UV-cured with mixed sol–gel precursors for usage as aerospace coatings. The cycloaliphatic silicones have also been ambient temperature-cured for release coatings, and have application as anti-fouling coatings. The inherent low surface energy makes the cycloaliphatic silicones prime candidates for surface tension additives. Presented at the 2006 FutureCoat! Conference, sponsored by the Federation of Societies for Coatings Technology, in New Orleans, LA, on November 1–3, 2006.     

Application of dynamic pressure probe technique to characterize a circulating fluidized bed

In this study a small diameter dynamic pressure probe was used to measure the flow characteristics and the annulus thickness in a circulating fluidized bed. The nonhomogeities of fluidization in the vertical and radial directions have been measured and the results are presented in a new way, as dynamic pressure against time. The diagrams reveal that the flow can, under certain conditions, exhibit significant reversals in the core areas. Particle size distribution in the vertical direction was also studied by using the quick-closing valve technique. The pilot scale riser was cylindrical and the particles were typical FCC catalyst.     

SIMS imaging in the study of coal surfaces

With SIMS imaging of coal macerals it was possible to distinguish organic and inorganic domains. In the study presented here three phases could be identified—an aluminosilicate phase, an organic rich region and a second inorganic phase rich in Ca. The results show that SIMS imaging is a powerful technique for determining in situ element distributions.     

有机硅脱模剂生产及应用技术

概述了脱模剂的工作原理、种类和应用。对有机硅脱模剂进行了分类,并分析了每种类型的有机硅脱模剂的特点。通过比较有机硅脱模剂与非硅类型脱模剂的特点,突出了有机硅脱模剂的优势。介绍了有机硅脱模剂的生产和应用技术,包括产品配方、模拟应用实验及优选改进等。最后,对有机硅脱模剂的典型产品作了简单介绍。     

硅橡胶在电气绝缘方面的应用进展

简述了国内外硅橡胶(高温硫化型硅橡胶、室温硫化型硅橡胶、液体硅橡胶等)在电气绝缘方面的应用情况。     

硅树脂及其涂料的研究新进展

综述了近十年来国内外耐热、耐腐蚀、耐候性硅树脂、改性硅树脂及其涂料的研究新进展；指出了硅树脂及其涂料的发展趋势。     

不同硅类混凝土涂层在海洋暴露环境下的性能

将有机硅抗涂鸦涂料、硅烷和仿清水混凝土涂料涂覆于混凝土试件,在浙江舟山暴露试验站浪溅区暴露1年后,对涂层的完整性、防水性和抗氯离子侵蚀性能进行了试验对比.结果为:涂膜损失率从大到小依次为抗涂鸦涂层、仿清水混凝土涂层和硅烷涂层,其厚度与暴露前相比分别损失了62％、63％和49％;防水效果从强到弱依次为仿清水混凝土涂层、硅...     

纳米技术在表面覆盖层中的应用

介绍了纳米技术在涂料和电镀中的应用。纳米技术可以改善涂料性能，增强其硬度、抗氧化性，使其具有光催化、抗菌、吸收电磁波、随角度变色以及对水、油的亲疏性能。介绍了制备纳米镀层的电沉积方法，主要有直流电沉积、脉冲电沉积和复合共沉积。纳米覆盖层广泛应用在工业、环境、医药、军事及科技领域中，应用前景宽广。