8 сентября, 2015 
Pokraskin Phenolic resin PVF adhesives are available as liquid-solid products or in the form of ready-made adhesive films, with or without support material. Both types cure at temperatures above 150 °C and at a pressure of more than 4 x 105 N m~2, requiring corresponding equipment such as heated presses or autoclaves. The pressure is required to squeeze out any water liberated within the adhesive in the form of vapor during condensation.
The liquid-solid product comprises a resol solution that is first applied, after which PVF powder is then sprinkled on; any excess PVF that does not adhere to the somewhat tacky resol coating is simply blown off. Nitrile-phenolic adhesives are applied in the form of a solution, the solvent is then allowed to evaporate, and the adhesive cures under pressure.
In the cured condition, nitrile-phenolic adhesives and phenolic resin PVF adhesives are extremely durable. Following correct oxidative surface preparation, PVF modified resol-type resins in particular demonstrate the unique property ofbuilding up unmatched, water-resistant adhesive forces towards metals (preferably aluminum alloys), without requiring any additives. There are three reasons why this salient feature occurs:
• The molecular weight of the resol component is low (mononuclear, dinuclear or sometimes trinuclear molecules), and the molecular mass distribution narrow; this allows the molecules to easily penetrate into nanostructured aluminum oxides without segregating in relation to stoichiometry.
• In cooperation with the phenolic OH-group, the ortho hydroxymethyl group may form absolutely water-resistant chelate compounds with the metal present on the aluminum surface.
• The cured phenolic resin retains a weakly acid character that stabilizes the aluminum oxides against hydration as soon as the moisture penetrates (see Section 3.1) [24].
These are the reasons why, despite a number of disadvantages, phenolic resin adhesives have been widely used since the 1950s and still are used today, virtually without any long-term problems, particularly in aircraft manufacture where aluminum is used predominantly. Although today, epoxy resins with better deformation properties and lower curing temperatures (120 °C) are employed, phenolic resin — containing primers are still indispensable and widely accepted. Nevertheless, due to their difficult processability (a curing temperature >170 °C for only 30min will alter the long-term resistance of cured aluminum alloys) and rather problematic brittleness and toxicity, phenolic resin adhesives have been replaced by other adhesive systems except in the wood construction industry (see Section 8.4) and
in friction lining bonding. Although, during the past 30 years there have been no major advances in the development of this type of adhesive, it might prove very interesting to take advantage of the new approaches with nanoparticles being used for plastication purposes.
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