Addition-Type Adhesives

For durable bonds, adhesives should be tough. However, many high temperature adhesives (addition-type polyimides, bismaleimides (BMI), and acetylene-terminated resins) are brittle and need to be toughened by elastomers. 

Leukocyte Adhesion Deficiency Type 2. Patients with this condition have a defect in the transport or production of the carrier molecule for the carbohydrate L-fucose (guanosine disphosphate L-fucose). The lack of fucose affects the ability of neutrophils to interact with ligands on endothelial cells such as P-selectins and E-selectins (81). Patients are susceptible to recurrent infections similar to those afflicting patients with type 1 leukocyte adhesion deficiency, have periodontal problems, and, in addition, may exhibit growth retardation and neurologic defects. Treatment with oral fucose has been known to be effective in reducing the frequency of infections (80). 

Leukocyte adhesion deficiency type 2 Same cUnical problems as in type 1. In addition, patients have growth retardation and neurologic defects. Treatment wifii oral fucose reduces frequency of infections. 

Adhesive Film, Hot Melt, Addition Type Polyimide, for Foam Sandwich Structure, -67 to 450°F... 

Compressed tablet formulations contain different types of ingredients necessary for proper preparation and therapeutic performance. The ingredients needed include diluents, disintegrating or binding (adhesive) additives, and lubricants. Tablets are designed to be dissolved slowly in the mouth and should not disintegrate quickly. Lactose... 

While this book was in its final preparation stage, two additional types of adhered sheet linings for chemical exposures have come to our attention. One is a sheet with, as the exposed face, a Tedlar(sf film adhered to a layer of rubber-asphalt blend. The sheet is applied with rollers to a substrate surface that has been coated with an adhesive primer. Sheet edges are butted with an adhesive lap strip of Tedlar applied over the joint to protect it. This is a proprietary product presently available from only one source, which will supply particulars of the application procedure and chemical resistance tables upon request. 

Table I shows what adhesives A, B, and C correspond to Budd type troughs used in this program. One additional type of trough was used in which the stamped sheet metal back is replaced by an aluminum honeycomb structure. This is known as the PAR series. Epoxy Y was used in that structure.

The adhesion properties of all types of polyolefins are not easy to explain because these properties are affected by different phenomena. Using of a single theory or mechanisms based on the physical and chemical adhesion manifestations is difiicult for the description of interdisciplinary nature and diversity. There is considerable information to discuss each of the adhesion mechanisms. Therefore, it is not possible to select only the thermodynamic theory of adhesion that is the best to describe the surface free energy of the polyolefin. All mechanisms and adhesion theories are implied by the diversity of polymer systems, which are embraced in combination with research for the analyses of adhesion properties. The physical and chemical composition in the first atomic layers dictates the adhesion and some other properties of the polymer materials. This layer represents underneath layer and this subsurface partially controls the outer layers. The double bonds and cross-linked stmctures limit the mobility macromolecules of polyolefins in the subsurface layers, which results in the functional group stabilization on the surface. Other basic research is necessary for an examination of the polymer subsurface layer and explanation of its effect changes of the surface properties. Moreover, for the improvement of quantitative measurements of adhesion, additional investigation is required. 

Polyphenylquinoxalines (PPQ s) were first prepared in 1967 by Hergenrother (56). In 1975, Koval et al. (57,58) introduced the acetylene-terminated PPQ (ATPQ) (Pig. 10), which is the addition type of PPQ. Resembling ATPI, ATPQ also has shortcomings. The ethynl group hinders the flow of the polymer chain, and the cured ATPQ is less thermal-oxidatively stable than the comparable PPQ. The detailed status of PPQ, as well as other high-temperature adhesives, is discussed by Hergenrother (45). ... 

Information on particular types of adhesive may be found in articles cited above and in the following entries Hot melt adhesives. Selection of adhesives. Silicone adhesives addition cure. Silicone adhesives condensation cure. Toughened adhesives. 

Table III, Addition-Type Adhesives and Prepreg Polymers for High-Temperature...

Future developments will undoubtedly attempt to correct these deficiencies, so that high-temperature adhesives may become an attractive alternative to other joining methods. The introduction of addition-type polymers has gone some way toward improving and making the bonding of large areas feasible new cure chemistries could offer further improvements. The adhesive systems evaluated to date have all relied on the application of... 

One drawback with addition-type polymers is that the cured adhesive tends to be brittle. Attempts to toughen addition polyimides have met with some success, though improvements in this area are needed. The development of systems exhibiting the same level of toughness as today s state-of-the-art epoxy adhesives is a goal for the future. 

Addition-type polyimides, which are thermosetting resins, were developed to improve the processability of polyimides, but their thermal stability is severely degraded by the presence of aliphatic bonds in place of the aromatic nuclei. However, the adhesive strength has been evaluated for the bismaleimide- (Section 4.3.4.1), bisnadimide- (Section 4.3.4.2) and acetylene-terminated (Section 4.3.4.3) imide oligomers. 

Unsaturated polyesters are fast-curing, two-part systems that harden by the addition of catalysts, usually peroxides. Styrene monomer is generally used as a reactive diluent for polyester resins. Cure can occur at room or elevated temperature depending on the type of catalyst Accelerators such as cobalt naphthalene are sometimes incorporated into the resin to speed cure. Unsaturated polyester adhesives exhibit greater shrinkage during cure and poorer chemical resistance than epoxy adhesives. Certain types of polyesters are inhibited from curing by the presence of air, but they cure fully when enclosed between two... 

Polysulfide sealants are formulated using reinforcing fillers, plasticizers, adhesive additives, and curing agents. Table 2 illustrates five types of compounds for use in several industries ... 

Two additional types of holding adhesives are worthy of mention because their unique properties have made them valuable in the automotive industry. These are silicone adhesives and locking compounds. 

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