Polyurethane sealants applications

The OSl PL [57] sealants are also widely used for general construction applications presented in Table 22. 

One supplier of raw materials to the adhesive and sealant industry for the automotives sector is Bayer. The polyurethane sealants created from these raw materials are used to prevent leaks, reduce wind and noise, and protect against corrosion amongst other applications. 

PU and other types of sealants will be studied in much details in the chapters Construction Sealants by Riilippe Cognard in Volume 6 of this Handbook, and in the chapter Industrial Sealants , later. 

Sonolastic 150 One-part polyurethane based For use on substrates such as aluminium, concrete, masonry, wood, and stone. It can be used in applications such as wet glazing, curtain wall construction, expansion wall joints, EIFS, panel walls, precast units, aluminium and wood window frames, fascia, and parapets Premium-grade, high performance, silyl-terminated, polyurethane-based, non-sag elastomeric sealant. It is a low-modulus formula, possessing extreme joint movement capability. -1- 100/—50% 

Sonolastic NPl One-part, moisture cure gun For expansion wall and EIFS USDA approved, joint 

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Plasticizers can be used to reduce both the viscosity and the cost of polyurethane and polysullide automotive and construction sealants. Higher molecular weight phthalate esters such as DINP, DIDP, and DUP or LI IP are generally suitable for most polyurethane sealant applications. Polysullide sealants require more polar plasticizers such as the alkyl benzyl phthalates, alkyl sulfonic acid esters, or dibenzoate esters. Recently the application of castor oil based plasticizers for polyurethanes has been described [46]. 

Whereas epoxy crack injecting systems are applied in static cracks, polyurethane systems are suitable for cracks where some movement is anticipated. There are other applications where polymeric materials are considered as competitors to each other. For example, neutral cure silicone sealants and polyurethane sealants are both suitable for use in construction joints. The former type offers greater durability and ageing resistance. However, polyurethane sealants are widely used because of their cost-effectiveness. Furthermore, some products are preferred over their counterparts for environmental reasons. 

Figure 4.4 Application of self-levelling polyurethane sealant to a pavement joint. Reproduced with permission from Fosroc...

R.M. Evans, Polyurethane Sealants, Technology and Applications, 2nd Edition, Technomic Publishing, Lancaster, PA, USA, 1993. 

The life expectancy of polyurethane sealants has been considered to be 10 years while that of butyl rubber, acrylics, polysulfides and silicones has been stated to be 15 years. Additional information on application techniques2 l and tests for sealants is readily available. 

Polyurethane Sealants Technology and Applications, by R.M. Evans, 1993, 186 pp., softcover, Technomic Publishing. Written for the compounding chemist, with four chapters on applications and live on materials. 

Main fields of application polyurethane sealants, frkns (automotive, tunnel linings, swimming pool covers, etc.), toys, gloves, profiles, tubing, coatings, work boots, occupational and protective clothing, waterbeds... 

Adhesives and Sealants. Polyurethanes can be conveniently applied in liquid or paste form and then polymerized/cured in place without evolution of volatile by-products, a very convenient feature in making enclosed adhesive bonds. Their mechanical strength, flexibility, adhesion, and chemical resistance make them attractive in many applications. Typical applications of polyurethane sealants are in expansion joints, aerospace, architectural, electronic, and marine products. 

Polyurethanes are the most versatile polymer systems used to formulate elastomeric sealants. Polyurethane sealants are sold both as two-component and one-component gun-grade compositions, packed in cartridge or in bulk. Applications are similar to those of the polysulfides, including the insulated glass markets and sealing automotive windshields. 

From Section 3.3, it was shown there are a large number of monomers and oligomers available for polyurethanes. It is often said that if cost was not of concern, then urethane-based polymers could be tailored to replace most polymers for applications that did not demand too high a service temperature [28]. Polyurethanes, besides adhesives and sealants applications, can be found as foams (rigid, flexible, micro-cellular), elastomers, and encapsulants which differ slightly in raw materials. However, processing parameters and additives make feasible a diverse synthesis of this material. 

Growing acceptance of polyurethane sealants as a replacement of older technologies, such as polysulfides for marine applications. 

Table 21 Sonnebom Sonolastic s polyurethane sealants for construction applications. 

Direct glazing is a common application in the automotive industry since the polyurethane sealant can perform the important functions of adhesion of glass directly into the metal frame, cope with the vibration and movement and still remain weather tight. The Sikaflex -255FC is a one-component compound from Sika which, because of permanent elasticity and excellent adhesion to metal, glass, and many other materials, is ideal for the automotive industry. 

Evans, R. M. (1993). Polyurethane sealants technology and applications. Technomic Publishing Co. Inc., Lancaster, USA. 

Particularly useful in preBiun sealant applications. The low volatility diaracteristics are of particular interest to foranila-tors of polysulfide and polyurethane sealants. 

In contrast, polyurethane sealants are widely used in many different applications. They are sold as two component and one-component gun-grade formulations, packaged in cartridges or in bulk. Pourable self levelling grades are also available. They compete directly with polysulfide and silicone sealants in many apphcations. 

Sealants are used to fill joints, gaps, and cavities between two or more similar or dissimilar substrates in contrast to adhesives which are used to bond two materials together, and usually with a much thinner bondline. Polymers typically used in sealant applications include silicones, urethanes, polysulfides, solvent acrylic, and butyls. Polysulfides, polyurethanes, and silicones are used more in bonding apphcations. 

Alkyl Sulfonic Acid Esters of Phenol There are two esters in this category, differing in average chain length of the alkyl group. The esters are reported to be used for GP applications in Europe and are often promoted as a phthalate alternative. They are also used in polyurethane sealants. Plasticizing efficiency (SF) is similar to that of... 

Evans, R. M. Polyurethane Sealants—Technology and Applications, Technomic, Lancaster, PA, 1993. 

Polyester polyols account for only ca. 10% of the total polyol market, which is dominated by polyether polyols such as hydroxy-terminated polyoxyethylene or polyoxypropylene. Polyester polyols are preferred for applications where better mechanical properties, wear resistance, and UV stability are required. The largest application of polyester polyols is flexible specialty polyurethane foam in the furniture, packaging, and automotive industries. Polyester polyols are also used for nonfoam applications such as coatings, paints, sealants, and adhesives 47... 

One of the more advanced technical offerings from castor oil is a line of polyester diols, triols, and higher functional polyols derived from 100% castor oil as products for the preparation of polyurethane prepolymers and elastomers [68]. The Polycin line of polyols are prepared by transesterification of ricinoleic acid and derivatives. The producers (Vertellus) offer diol and triol products, as well as a recently developed series of diol and triol glyceryl ricinoleate esters that are stated to be prepared from 100% castor oil, making them fully renewable in content. The products are recommended for coatings, sealants, and adhesive applications. 

Isocyanates (RNCO) are industrially relevant compounds which find application in several fields [9, 106]. Many isocyanates serve as the starting materials for the manufacture of plant protection agents, pesticides, dyes, resins and plastics, textile waterproofing agents, detergents, bleaches, and adhesives. They are also widely used in surface coatings such as paints, sealants and finishes, and in the manufacture of rubbery plastics such as those used to coat wires. Traditionally, diisocyanates are the primary feedstock for the production of polyurethanes. The global market for diisocyanates in the year 2000 was 4.4 million tonnes, of which 61.3% was methylene diphenyl diisocyanate (MDI), 34.1% was toluene diisocyanate... 

Most conventional low-modulus adhesives and sealants, such as polysulfides, flexible epoxies, silicones, polyurethanes, and toughened acrylics, are flexible enough for use at intermediate low temperatures such as -40°C. Low-temperature properties of common structural adhesives used for applications down to -129°C are illustrated in Fig. 15.9, and the characteristics of these adhesives are summarized in Table 15.12. 

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