Ester Adhesives

Within the last few years, cyanate ester adhesives have started to find applications in the space and, particularly, the satellite market. They are particularly suited to these applications due to their exceptionally low water uptake and out-gassing characteristics, good high-temperature performance and low dielectric constant and low loss tangent electrical properties. 

As carbon/cyanate ester prepregs start to be used in the eonstruetion of antennae reflectors, cyanate ester adhesives will be used to bond the sandwieh panel together. 

Other current applications have been seen in bonding structural components in space telescope applications. 

The fact that cyanate ester formulations offer outstanding electrical properties makes them very good candidate systems for both composite matrices and film adhesives for radome applications. 

The approach taken by Chelton Radomes is that of a slow but steady replacement of the conventional epoxy adhesives by cyanate ester-based formulations (for example, EX 1516 from Bryte Technologies) in new designs, such as the EHlOl Merlin helicopter mentioned above. 

These include cellulose acetate, cellulose acetate butyrate, cellulose cap-rate, and cellulose nitrate (nitrocellulose or pyroxylin). Cellulose esters are used for bonding leather, paper, and wood. Although not generally used with metals, specific nonporous substrates such as cellophane (regenerated cellulose) and glass are sometimes bonded with cellulose nitrate or other cellulose esters applied from solution.  

Cellulose acetate and cellulose acetate butyrate are water clear and more heat resistant, but less water resistant, than cellulose nitrate. Cellulose acetate butyrate has better heat and water resistance than cellulose acetate and is compatible with a wide range of plasticizers. Cellulose nitrate is tough, develops strength rapidly, is water resistant, bonds to many surfaces, and discolors in sunlight. The dried adhesive (nitrocellulose) is highly flammable.  

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Production of the 2-cyanoacryhc ester adhesives on a worldwide basis is estimated to be approximately 2400 metric tons. This amounts to only 0.02% of the total volume of adhesives produced but about 3% of the doUar volume. 

Because of the high costs of raw materials and the relatively complex synthesis, the 2-cyanoacryhc esters are moderately expensive materials when considered in bulk quantities. Depending on the quantity and the specific ester or formulation involved, the prices for cyanoacryhc ester adhesives can range from approximately 30/kg to over 1000/kg. For these reasons, as weU as several technical factors related to handling and performance, cyanoacryhc ester adhesives are best suited to small bonding apphcations, very often where single drops or small beads are adequate for bonding. In such cases the cost of the adhesive becomes inconsequential compared to the value of the service it performs, and these adhesives become very economical to use. 

The new technical developments have made possible quick bonding to woods, papers, and porous surfaces. Polyolefins, which comprise approximately 50% of the U.S. thermoplastic production, are now bondable with the cyanoacrylic ester adhesives. These new capabilities are sure to provide for continued market growth in the years ahead. 

Several methods have been employed to overcome the slippage problem during rheological measurement. One is to use a cyanoacrylate ester adhesive to attach the gel to the plates (Konstance and Holsinger, 1992). 

Cyanate-ester adhesives are produced from resins that contain cyanate groups... 

In spite of their low polarities, cyanate esters adhere well to metal conductors and maintain good adhesion up to 250 °C. They are thus compatible with solder-reflow temperatures. The adhesion strengths of toughened cyanate-ester adhesives, as measured from aluminum-to-aluminum lap-shear specimens are reported to be 5,900 psi at 25 °C, 2,572 psi at 67 °C, and 4,000 psi at 82 °C. 

Developments in cellulose ester adhesives and alkyd resin adhesives Cyclized rubber in adhesives (Fischer-Goodrich Co.)... 

Pressure sensitive and contact adhesives are made from a variety of polymers including acrylic acid esters, polyisobutylene, polyesters, polychloroprene, polyurethane, silicone, styrene-butadiene copolymer and natural rubber. With the exception of acrylic acid ester adhesives which can be processed as solutions, emulsions, UV curable 100% solids and silicones (which may contain only traces of solvents), all remaining rubbers are primarily formulated with substantial amounts of solvents such as hydrocarbon solvents (mainly heptane, hexane, naphtha), ketones (mainly acetone and methyl ethyl ketone), and aromatic solvents (mainly toluene and xylene). 

Cyanate ester adhesive Silver QMI301 Loetite 1.9... 

High-modulus adhesives are likely to have high bending stresses, high deflections, and low radii of curvature. As examples, a typical silver-filled epoxy with a deflection of 3 pm had a low radius of curvature of1,070 mm and a cyanate-ester adhesive reported to have a high modulus of 10,000 MPa had a radius of curvature of 5,000 mm. " ... 

Polyvinyl ester adhesives (especially polyvinyl acetate)... 

Most types of Hot melt adhesives used in the mannfacture of laminates and in rapid Packaging industry applications are mineral oil-derived, hydrophobic and essentially non-dispersible, so they cannot be considered as renewable. However, some basic polymers have been prepared over the last decade from vegetable sources, which are renewable, and are adhesive, although these properties have limitations. These include poly(hydro-xybutyrate/hydroxyvalerate) (PHBV), poly(lactide) (which has poor thermal stability), and starch esters. Adhesives based on sulphonated polyesters with polar petroleum waxes have improved adhesion and adequate water dispersibility. In general, however, the perfect adhesive from renewable resources with satisfactory adhesion properties remains to be discovered. 

A vinyl ester adhesive for bonding concrete, metal and glass. 804BDA RED EX-1... 

CD-9052 is a trifunctional acid ester adhesion promoter for UV/EB inks emd coatings that offers exceptional cure speed. CO-9052 assists adhesion to difficult stibstrates, such as plastics, metals, and glass. CD-9052 is not recommended for use in formulations containing tertiary amines. Usage levels of 3-12% are recommended. 

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