Two-Part Pastes

The chelated calcium cementing materials are suppHed as two-part paste products. In use, equal parts of the two pastes are thoroughly mixed together to give a fluid mass that can be appHed without pressure over an exposed tooth pulp or in a deep-seated cavity. Under the influence of the oral temperature and humidity, the fluid mass sets to a hard, strong, therapeutic protective seal. 

Paste adhesives are supplied as either one- or two-component adhesive systems. They can be used in applications where pressure cannot be applied. Some two-part pastes cure at room temperature after the appropriate proportions are mixed. Epoxy, urethane, and acrylic adhesives are all available as paste adhesives. 

Polysulfone A number of adhesives have been found useful for joining polysufone to itself or to other materials. These include 3M Company s EC 880 solvent-base adhesive, EC 2216 room-temperaturecuring epoxy two-part paste, Bloomingdale Division, American Cyana-mid Company BR-92 modified epoxy with DICY curing agent, or curing agent "Z" (both spreadable pastes), vinyl-phenolics, epoxy-nylons, epoxies, polyimide, rubber-based adhesives, styrene polyesters, resorcinol-formaldehyde, polyurethanes, and cyanoacrylates. The EC 880, EC 2216, and the two BR-92 adhesives are recommended by the polysulfone manufacturer. Union Carbide (16) (17). 

Figure 3.22 Manufacturing steps in formulating one-part and two-part paste adhesives.

There are three main polymers presently used for structural adhesive bonding and they are phenolics, epoxies and urethanes. We can also include in our classification, the initial physical state of the uncured adhesive since it governs the type of application and curing conditions. Structural adhesives are manufactured in the form of films or pastes. The films are one-part adhesives, i.e., they contain a latent catalyst which requires heat for activation. Structural adhesive films are made in a number of different thicknesses and can either be supported (containing a scrim) or unsupported. In general, film adhesives require the application of pressure during cure in order to obtain ultimate properties. Paste adhesives are either one- or two-part materials. That is, pastes can either contain a latent heat activatable catalyst, or they can be a system which is separated into two parts, one of which contains the cur a t i ve/ca talys t. Two-part pastes cure at room temperature. In this section the chemistry of one-... 

Adhesives recommended by the manufacturer (Phillips Chemical Company) include anaerobics (Loctite 306), liquid two-part epoxies (Hughson s Chemlok 305), and a two-part paste epoxy (Emerson Cuming s Eccobond 104). Also recommended are USM s BOSTIK 7087 two-part epoxy and 3M Company s liquid two-part polyurethane EC-3532. ° ... 

Scarf joints should only be used if specified by the component manufacturer. Much good material must be removed to produce the taper, so skilled operatives are necessary. A layer of toughened film adhesive should be used between the scarf and the patch, or a layer of toughened two-part paste adhesive if a wet lay-up is used. 

A family of 177 C curing, toughened cyanate ester paste adhesives. EX-1537 is a thixotropic two-part paste and EX-1537-1 is of lower viscosity. Both offer excellent mechanical and thermal performance in addition to low moisture absorption and low outgassing, coupled to excellent microcrack resistance, all ideal properties for space and cryogenic applications. 

Epoxide die attach materials are available in a wide variety of forms but the main types are two-part pastes, one-part pastes, unsupported films and supported films. The principal two types are the one- and two-part pastes. A variety of possible epoxide chemistry systems is available for both one- and two-part cured materials. A typical two-part formulation would be based on a diglycidyl ether of bisphenol A or bisphenol F and be cured with an aliphatic amine or polyamide. 

Epoxy- phenolic Two-part paste, supported film Heat and pressure Uaod properties at moderate cures volatiles released during cure retains 50% of bond strength at 500 F limited shelf life low peel strength and shock resistance Metals, honeycomb core, plastic laminates, ceramics Med... 

There are many formulations of inorganic adhesives. Often they are one- or two-part paste or cement-like compounds for specific applications. The general areas of use are ... 

There are numerous commercially available epoxy adhesives supplied as One-part Pastes, Two-part Pastes or Films. 

Two-part pastes are normally room temperature (RT) curing, although heating can be used to accelerate the cure. This may be essential to realise the full service temperature potential of the adhesive and provide an acceptable rate of cure. The paste viscosities range from thin liquids to putty. Many are thixotropic or non slumping to aid handling and placement in the joint. 

Epoxy-two part paste Epoxy - two part paste ... 

Manufacturers Comments RT cure. Lowviscosity, two-part paste with good flexibility, peel strength and low temperature properties. 

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