Лако-красочные материалы — производство

The strength of a bonded joint will be determined by the strength of its weakest component, which is generally designed to be the adhesive. It follows that the requirements for satisfactory joint performance are (a) good contact between the adhesive and substrate (b) absence of weak layers in the joint (c) that the adhesive should […]

4.1 Introduction The truly structural adhesive joint is relatively new. The evolution of the various design approaches follows the empirical development of appropriate joint configurations(l-7) — themselves following on from the long historical development of load-bearing joints in, and between, engineering materials. It must however be emphasized that structural bonded joints existing in engineering disciplines […]

Optimisation of surface pretreatment is the key to maximising joint durability. The adhesive influences the surface oxide layer and the surface oxide layer influences the boundary layer polymer matrix; the whole must therefore be viewed as a unique system for every adherend-adhesive combination. The interplay of chemical bonding and microstructural and macrostructural behaviour greatly compli­cates […]

The wide range of techniques for studying pretreatment effects may be classified as (a) mechanical (destructive) and (b) surface analytical (non-destructive). Naturally, different substrate materials warrant different approaches. Mechanical test procedures Experimental assessments of the effects of surface treatments using mechanical tests are of limited value unless environmental exposure is included. Appropriate comparative tests subject […]

The time elapsed between surface pretreatment and application of the adhesive should generally be kept as short as possible, as implied earlier, because surface energies are lowered by the adsorption of atmospheric moisture and contaminants. Silicone-containing contaminants and mould-release oils should particularly be avoided. Kinloch(7) discusses some theoretical aspects of the bonding operation, and Hewlett […]

In general, adhesive application to painted surfaces is not to be recommended. However, just as the correct surface treatment is necessary, the application of an adhesive-compatible primer coating may also be desirable. Naturally, the picture of the adhesive-adherend interfacial zone then becomes more complicated. The use of adhesive primers may be more critical in some […]

The surfaces of many plastics and rubbers have low surface energies (Table 3.1) such that wetting by an adhesive is inhibited unless special surface pretreatment processes have been employed. How­ever, plastics which contain polar groups such as PVC, nylons and acrylics are bondable with a minimum of surface treatment. Plastic composites such as glass — […]

Surface preparation should include (a) removal of all loose and unsound material until coarse aggregate is exposed (b) cleaning and (c) drying (although there exist some special polymeric systems which are claimed to bond to damp or wet concrete, and cementitious Applied stress (N/mm2) Log Failure Time (min) □ Phosphoric acid anodise (Boeing process) • […]

Metal and oxide surfaces. In joints involving metallic substrates, the adhesive ‘sticks’ to the metal surface oxide layer and not to the metal itself. Such joints can cause problems in service because oxide structures, and bonds to them, are susceptible to environmental attack. Refined metals, by their nature, are chemically unstable, tending to react with […]

Some effects of surface pretreatments are summarised in Table 3.4. Degreasing. Solvent degreasing removes grease and most potential contaminants. The choice of solvent should be based on the principle Fig. 3.6. Schematic topography of solid surfaces (Ref. 62).   x 2000 x 20000 Micron scale shown in bottom r. h. corners Fig. 3.7. Scanning electron […]