Sealant materials

In addition to the YSZ electrolyte and metallic interconnect, SOFC stack also includes component materials such as seals and manifolds. Sealant materials based on glass or... 

Kharitonov NP, Shentenkova IA (1977) Heat-resistant organosilicate sealant materials. Nauka Leningrad [in Russian]... 

Epoxy and polyurethane adhesives are not appreciably affected by 10-9 torr for 7 days at room temperature. However polyurethane adhesives can exhibit significant outgassing when aged under 10-9 torr at 107°C.75 At room temperature a high vacuum does not generally cause significant weight loss in commercial adhesive and sealant materials. 

Once the contents of the container are evenly distributed, the adhesive or sealant material can be removed. The use of pumps for transferring the adhesive or sealant has several drawbacks. Filled compounds have an abrasive action on the moving parts. This is particularly true with fillers such as silica. Compounds that polymerize easily will tend to begin their polymerization due to friction within the pump. This will gum up the moving parts and make them inoperable. Therefore, transfer is best done under some type of pressure. 

Van Twisk, J., and Aker, S. C., Storing Adhesive and Sealant Materials, in Adhesives and Sealants. 

ACI (1993) Guide for polymer concrete overlays. ACI Material Journal, 90(5), 499-522. Brieton, P.R. (1994) Sealant materials properties and performance - an overview, in European Adhesive and Sealant Year Book 1994, FMJ International, Redhill, Surrey, pp. 7-8. 

Difficult environments for sealant materials are long-term immersion in water or continuous exposure to high humidity. A sealant immersed in water or exposed to saturated water vapour will be subject to physical, chemical and biochemical changes. The useful life of a sealant will depend on the relative levels of these effects, which in turn will depend on the type of polymer used and the formulation. The changes may occur in bulk or on the surface, and may lead to a loss of adhesion, which is the most damaging result of attack by water (Lee et al., 1992). 

Hanhela, P.J., Huang, R.H.E. and Paul, D.B. (1993) Effect of thiols and fuel system icing inhibitors on the integrity of aircraft fuel tank sealants. Materials Forum, 17(2), 139-52. 

Joints must then be sealed with an elastomeric sealer in order to prevent seepage through the seam or crack. To seal control joints and cracks, a chemically resistant joint sealer is applied in the seam joint. There are many different sealant materials and specifications for installation which should be considered at the design stage. 

Until very recently almost no new materials were developed for the solar collector industry, which is essentially in its infancy. This investigation was performed to help Identify deficiencies of the available sealant materials with the expectation, which we believe is beginning to be realized, that this would lead to development of superior materials for solar collector applications, ... 

Development of planar solid oxide fuel cells (SOFCs) and other electrochemical devices, such as oxygen generators and sensors, makes it necessary to elaborate sealant materials for hermetization in high-temperature zone. The sealants should satisfy numerous requirements, including chemical stability, good adhesion and thermal expansion. 

Weather Tester Climate Doesn t Faze Silicone Sealant". Materials News, Dow Coming Corp., Nov.-Dec. 1978, p. 5. 

Building Sealants Materials, Properties and Performance, STP 1069, edited by T.F. O Connor, 1991, 351 pp., ASTM International. 

A widely popular container or carton used to store liquid or solid food is coated/laminated with various barrier and sealant materials, for example, a high-density polyethylene (HOPE), a heat seal-able polymer material such as low-density polyethylene (LDPE), or a heat-sealable barrier material such as an ethylene vinyl alcohol copolymer (EVOH), which can emit unwanted odors created during extrusion coating or package converting/sealing. 

X. Chen, V. Cuipers, M. Fan, J.E. Frencken, Marginal leakage of two newer glass ionomer-based sealant materials assessed using micro-CT, J. Dent. 38 (2010) 731-738. 

Alternatively the pulp may be saved by the process of pulp capping. This involves placing some sort of material over the pulp to protect it and maintain its viability so that more extreme treatment (extraction or endodontic therapy) can be avoided [1]. Two possible approaches are available, namely direct pulp capping, in which a bioactive material is placed directly over the exposed pulp, and indirect pulp capping, in which a cavity liner or sealant material is placed over a residual thin layer of dentine, which may be sound or carious. In the latter approach, the pulp has not been exposed, but it is at risk of becoming so either by the progress of the residual caries or by the process of tooth preparation. 

After addition of charges, these polymers lead to elastomers that are stable at high temperature and have applications as sealant materials. 

The latter is obtained by reducing the effective depth of the slab, inducing a sawn groove. The depth of the groove is related to the thickness of the slab the width of the groove may be determined, but in any case its minimum value is 3-4 mm. The groove induced is filled with a suitable sealant material. Details of a typical contraction joint are shown in Figure 14.7. 

The sealants are usually modified bituminous materials applied hot or cold. The hot applied sealant materials should comply with the requirements of specifications such as CEN EN 14188-1 (2004) or ASTM D 6690 (2012). The cold applied sealants should comply with the requirements of specifications such as CEN EN 14188-2 (2004) or ASTM D5893 (2010). 

After completion of compaction of the last asphalt layer, it is recommended that the edges of the patch be sealed with an appropriate joint sealant. This provides an excellent sealing protection against water infiltration. The sealant material is poured along the edges, forming a bitumen band of 30 to 40 mm wide. The sealant is the same as the one used for crack/ joint sealing (modified bitumen). 

The only appropriate treatment is to remove the old joint sealant material, clean out the joint thoroughly, prepare the groove (if needed) and replace the backer material (if used) and reseal with appropriate sealant. The procedure is known as joint repair. 

Sealant materials could be hot applied (complying with CEN EN 14188-1 2004 or ASTM D 6690 2012), cold applied (complying with CEN EN 14188-2 2004 or ASTM D 5893 2010) or preformed joint seal material applied by compression (complying with CEN EN 14188-3 2006, ASTM D 2628 2011 or other specifications). When backer material is used, it should comply with ASTM D 5249 (2010) or any other specification. 

They exhibit versatility in structure and hence in their properties. For example, polyurethanes may be obtained as foam, thermoplastic, elastomeric, resin, adhesive or sealant material, depending on the composition of their constituents and the conditions of polymerisation. 

The sealant materials used for the solar collectors must be durable under harsh environments (132). They must... 

T. B. G. Jones, Ejfect of movement during cure on the experimental performance of construction sealant materials, Ph.D. Thesis, Brookes University, Oxford, England, 2001. 

Direct exposure to moisture may also have adverse effects on the performance of some sealants, either by its effects on the sealant or on the joint substrates." Absorption of water may cause softening of the sealant material, and some acrylic-based sealants are particularly affected in this way. If absorption is followed by prolonged near-freezing temperatures, the sealant may become stiffer, leading to an increase in internal stresses as the joint opens. These stresses tend to promote failures of adhesion at the interface of the sealant and the joint surfaces. The repeated absorption of moisture by components of porous materials, such as concrete, may cause a gradual migration of soluble salts towards the sealant interface, which could lead to adhesion failure. This effect can be reduced by the application of appropriate primers to the joint faces before application of the sealant. It is essential to follow the advice of the sealant manufacturer in this respect. 

The ATF chanistry required to achieve a positive p-v curve to prevent shudder and maintain a sufficiently high friction level to provide adequate torque capacity will depend on the chemistry of the friction materials and the type of materials used to construct the transmission clutches [20]. A typical transmission clutch uses a cellulosic friction material in combination with steel plates. Other friction materials like carbon fiber are also used. Instead of steel plates, aluminum, copper, bronze, tin, and other metallic materials can also be used. In addition to these materials, plastic, nylon, and a variety of elastomeric sealant materials are used to construct other components of the automatic transmission. More recently, ATFs are required to be compatible with electronic circuitry and sensors [21]. Thus, changes in transmission design and materials have a direct effect on the... 

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