Liquid rubber adhesion

One of the most common rubber adhesives are the contact adhesives. These adhesives are bonded by a diffusion process in which the adhesive is applied to both surfaces to be joined. To achieve optimum diffusion of polymer chains, two requirements are necessary (1) a high wettability of the adhesive by the smooth or rough substrate surfaces (2) adequate viscosity (in general rheological properties) of the adhesive to penetrate into the voids and roughness of the substrate surfaces. Both requirements can be easily achieved in liquid adhesives. Once the adhesive solution is applied on the surface of the substrate, spontaneous or forced evaporation of the solvent or water must be produced to obtain a dry adhesive film. In most cases, the dry-contact adhesive film contains residual solvent (about 5-10 wt%), which usually acts as a plasticizer. The time necessary... 

Liquid rubbers In order to improve the flexibihty of short glass fiber-reinforced epoxy composites, Kaynak et al. [53] modified the epoxy resin matrix with hydroxyl-terminated polybutadiene (HTPB) liquid mbber. A silane coupling agent was also used to improve the interfacial adhesion between glass fibers and epoxy matrix. However, Humpidge et al. [54] reported some unique processing problems for the resulting pasty mixmres when short textile fibers were incorporated in a hquid mbber medium. 

MIL-A-8576 MIL-A-9117 MIL-A-12850 MIL-C-14064 MIL-C-15705 MIL-C-18255 MIL-C-18969 MIL-C-23092 MIL-C-27315 MIL-C-27725 MIL-C-5539 MIL-C-7438 Adhesive, Acrylic Monomer Base Synthetic Elastomeric Sealant Natural Liquid Rubber Cement Grinding Disk Cement Caulking Compound Caulking Compound with Synthetic Rubber Base Caulking Compound—Watertight Exterior Hull Seams of Vessels Cement, Natural Rubber Coating Systems, Elastomeric Coating, Corrosion, Preventative, Air Fuel Tanks Natural Rubber Cement Core Material, Aluminum, for Sandwich Construction... 

Tiquid rubbers are polymeric products used primarily as adhesives, sealants, castable rubbers, and rocket propellant binders. The name liquid rubber comes from the properties of flowing at room temperature and curing to rubbery networks. These materials offer advantages over conventional elastomers in their ease of handling and processing as they can be readily pumped and mixed in low power (relative to normal rubber) equipment with resultant savings. 

Prior to this discovery, in 1954 Silberberg and Kuhn (62) were first to study the polymer-in-polymer emulsion containing ethylcellulose and polystyrene in a nonaqueous solvent, benzene. The mechanisms of polymer emulsification, demixing, and phase reversal were studied. Wetzel and Hocks discovery would then equate the pressure-sensitive adhesive to a polymer-polymer emulsion instead of a polymer-polymer suspension. Since the interface is liquid-liquid, the adhesion then becomes one type of R-R adhesion (35, 36). According to our previous discussion, diffusion is not operative unless both resin and rubber have an identical solubility parameter. The major interfacial interaction is physical adsorption, which, in turn, determines adhesion. Our previous work on the wettability of elastomers (37, 38) can help predict adhesion results. Detailed studies on the function of tackifiers have been made by Wetzel and Alexander (69), and by Hock (20, 21), and therefore the subject requires no further elaboration. 

Caoutchouc Bindings. The process of binding with single leaves stuck in with liquid rubber instead of the traditional sewn sections was patented in Great Britain in 1836 and was commercially exploited three years later. Most volumes so bound have disintegrated and need to be reconstituted with PVA adhesive in place of the short-lived rubber. Some of the smaller ones, particularly those with card-like leaves, are easily done, but some of the larger tomes, especially those which have been... 

For many years, it was known that hydrogel adhesives and SIS adhesives were soft to the skin, and that their skin irritation was milder in comparison with common acrylic and natural rubber adhesives. Based on these findings, guiding principles for lowering the skin irritation of adhesives were gradually elucidated. These are the following 1) adhesive matrix should contain lots of liquid substance 2) polymers should... 

Compatibilized Liquid-Rubber Blends and Structural Adhesives... 

Fig. 13.7 The TEM image of the nanophase-separated structural epoxy adhesive containing nitrile rubber/phenolic polyurethane liquid rubber blends (cure with dicyandiamide at 180°C).

Fig. 13.8 The T-peel resistance as a function of the crosshead speed for nitrile rubber/phenolic polyurethane liquid rubber blend toughened epoxy (upper curve) and conventional nitrile rubber-toughened epoxy structural adhesives (lower curve).

Commercially available liquid rubber (CTBN, ATBN)-toughened epoxy often shows outstanding fracture properties, and the technology is exploited in engineering adhesives [58]. However, because the butadiene component of the elastomer contains unsaturation, it would appear to be a site for premature thermal and/or oxidative instability, and such modified resins are not suitable for application at high temperature. One would imagine that excessive crosslinking could take place with time which would detract from otherwise desirable improvements accomplished with these structures. Second, there is some limitation in its use due to a possibility of the... 

Liquid anaerobic adhesives dissolve in most organic solvents and oils and, even when true solution is not possible, they normally disperse harmlessly. With certain exceptions, the liquid adhesives will dissolve or swell many thermoplastic materials such as Polyacrylates, Polyvinylchloride, Polystyrene and, after lengthy exposure, natural rubber and shellac. 

The attempt to blend natural rubber with epoxy resins resulted from the abundance of natural rubber and that it was a renewable resource. Nevertheless, interfacial adhesion between natural rubber and epoxy resins was weak due to the hydrophobic nature of natural rubber. Thus, it was an interesting experiment to blend the toughened epoxy resins with synthetic reactive liquid rubber. In order to achieve an efficient stress transfer between rubber and the... 

Table 8.14 shows the benefit of adding Saret 633 to several liquid rubberic sealant formulations. Formulations and cure conditions are described in Section 8.3.2. In each case, a control without Saret 633 was also tested for comparison and found to have adhesive values ranging from 0 to 0.27 MPa. 

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