Лако-красочные материалы — производство

When fully cured, cyanoacrylates will meet class VI standards for plastics, the highest class of safety and biocompatibility as defined by the United States Pharmacopoeia (USP).

B. Thermal Conductivity

Cyanoacrylates are essentially thermally nonconductive materials. The value for a typical methyl-grade cyanoacrylate is 2.1 (Btu-in.)/(hr-ft[16]-°F).

C. Durability

Assemblies joined with cyanoacrylate adhesives exhibit good long-term durability, particularly when the materials are somewhat flexible, such as rubbers and most plastics (see Fig. 7). Bonded lap shear specimens have been aged outdoors for 7 years with good retention of strength (see Table 8).

When impact resistance and/or strength is required, it can be improved dramatically by the ‘‘rubber sandwich’’ technique. In this case, a rubber sheet bonded between the rigid plastic or metal substrates will absorb all peel and impact forces. It is also useful in absorbing stresses when thermal expansion and contraction occur.

II. CHLOROSIS

There are times when various environmental factors can affect bonding results. One such phenomenon is chlorosis, in which white particles appear on the bonded parts. Chlorosis

5. Form a protective shield on the surface where chlorosis is likely to develop by applying oil to the area surrounding the material surface immediately before or after the bonding operation.

Chlorosis can be eliminated by the following:

1. Wipe the particles carefully with a dry cloth.

2. Wipe off the particles with solvent.

The particles can readily be wiped off by the use of a cloth containing a solvent such as dimethylformamide, nitromethane, acetone, or chlorinated or fluorinated solvents. In this case, however, if the bonded object is plastic, caution must be exercised because plastics can be affected adversely by solvents.

Poor bonding arises from problems associated with the adhesive itself: for example, its decreased adhesive power. The simplest method of checking on the spot for any decrease in adhesive power is to test with Bakelite samples. If the adhesive is found to have decreased adhesive power, it has probably been stored improperly.

Material kept in the work environment up to 6 months will not suffer deterioration. For periods over 6 months, storage in 40°F or below can triple the useful shelf life.

III. SUMMARY

Cyanoacrylates have shown themselves well in permanent outdoor assemblies as well as in temporary manufacturing aids. They are safe, convenient materials to incorporate in plant operations. New developments in technology have improved moisture resistance, setting times, gap filling, clarity, high-temperature resistance, and flexibility, and most recently, cyanoacrylates have become less surface sensitive.

As always, thorough testing of a specific application should precede specification. New research has led to improved commercially available models that are finding use in applications previously thought unsuitable for cyanoacrylates. Where appropriate, cyano­acrylates can increase productivity dramatically and reduce fundamental costs, to produce high-integrity parts for aircraft, industrial, agricultural equipment, electronic, automotive, and maintenance applications.