Лако-красочные материалы — производство

The wide variety of applications of anaerobic adhesives and sealants is made possible by the modifications that make the viscosity appropriate to the application. An application that requires penetration into close-fitting parts should have very low viscosity, while a product used with large, loose-fitting parts should have a high viscosity. A styrene acrylate copolymer could be used to increase the viscosity [59]. Polymethacrylates, cellulose esters, butadiene-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, poly(vinyl chloride), copolymers of vinyl chloride and vinyl acetate, poly(vinyl acetate), cellulose ethers, polyesters, polyurethanes, and other thermoplastic resins have also been used to control the flow characteristics of anaerobic sealants [60]. The flow characteristics of anaerobic formulations can also be controlled by the addition of fumed silica and other solid additives which can impart “thixotropic” properties [61].

Many anaerobic adhesives and sealants may require a relatively low strength so that the components can be disassembled for repair or replacement. Many liquid plasticizers have been used for this purpose [62], but the use of a low-molecular-weight polyester has been found to be advantageous [63]. The ‘‘toughness’’ properties of anaerobic adhesives can be enhanced by the addition of a reactive elastomer [64]. The heat resistance of anaerobic adhesives and sealants can be enhanced by the addition of a bismaleimide (LV) [65]. These maleimide additives appear to be relatively unreactive during the initial anaerobic cure. As the adhesive is exposed to high temperatures the methacrylate back­bone degrades and the methacrylates can then copolymerize with the maleimides, forming a more heat-resistant matrix [66].

The addition of dyes to anaerobic adhesives and sealants assists in identification and inspection of the products. Automated inspection procedures are made possible with dyes that fluoresce under ultraviolet light. Titanium dioxide pigments can make the sealants more visible.

Solid fillers are added to some anaerobic adhesives and sealants for various purposes. Mica, talc, and other mineral fillers can help to provide an instant seal capability to anaerobic pipe sealants. The sensitivity of the anaerobic cure system to metal contam­ination requires that these fillers be chosen very carefully.

Powdered graphite, polytetrafluoroethylene, and polyethylene can function as lubricants in pipe sealants and thread-locking compounds. This lubrication can prevent galling in close-fitting pipe threads [67]. Lubricating additives in thread-locking sealants can provide control of the clamping force exerted by a fastener at a given tightening torque [68].